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Cirrodrilus japonicus (Pierantoni, 1912) Japanese name: Ko-zariganimimizu (Figures 2, 3) Stephanodrilus japonicus Pierantoni, 1912: 20, Fig. 14, Tab. 5, Figs. 11–13. Stephanodrilus (Stephanodrilus) japonicus Pierantoni: Yamaguchi 1934: 199; Yamaguchi 1935a: 24. Stephanodrilus japonicus Pierantoni: Yamaguchi 1954: 101. Cirrodrilus japonicus (Pierantoni): Timm 1991: 329, Fig. 46; Gelder 1996: 658; Gelder 2019: 490. Stephanodrilus (Stephanodrilus) ezoensis Yamaguchi, 1934: 197, Fig. 7. Stephanodrilus (Stephanodrilus) ezoensis Yamaguchi: Yamaguchi 1935a: 23, Fig. 10.2a, 2b; Yamaguchi 1935b: 14, Fig. 6. Stephanodrilus ezoensis Yamaguchi: Yamaguchi 1954: 101. Cirrodrilus ezoensis (Yamaguchi): Timm 1991: 329, Fig. 46; Gelder 1996: 658; Gelder & Ohtaka 2002: 338, Tabs. 1, 2; Ohtaka 2010: 460, Fig. 12; Gelder 2019: 489; Ohtaka et al. 2020: 184, Tab. 1. Type material. In 1912, Pierantoni deposited 16 specimens in a fluid-filled small jar labeled “ Stephanodrilus japonicus Syntypes ” under the catalogue number, ZMH V-2912, in the Museum of Nature Hamburg —Zoology, Germany; two specimens were mounted whole in Canada balsam on separate slides by AO in 2023. Yamaguchi (1934) did not designate any type specimens either or a type location, but slide-mounted whole specimens of Stephanodrilus ezoensis in his collection were identified and designated syntypes according to Article 73.2. of the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 1999) by Ohtaka et al. (2020) (ICHUM-1666, -1799, -1801, -1809, -1802, -1806, -1807, -1811, -1815, -1821). Yamaguchi reported collecting specimens from 15 sites on Hokkaido, Japan (Gelder & Ohtaka 2002), but only one slide (ICHUM-1811) bore a location name, that of Soranuma (Fig. 1: site No. 6). Material investigated. Two specimens of syntype series of C. japonicus, and extant syntype series of C. ezoensis (see above). Sixty-eight non-type specimens, collected by the first author and his colleagues on Hokkaido at sites No. 2, 9, 16–37 (Fig. 1), together with specimens whole-mounted on slides, in the first author's collection. Description. Total body length 2.0–3.0 mm, the head width is usually subequal to segment 1, and the club-shaped body has distinct segments (Fig. 2A). Dorsal ridges and projections, supernumerary muscles and lateral paired lobes on segments 8 and 9 are all absent. Peristomium has four lobes on the dorsal lip, two pairs of lateral lobes, a median emargination in the ventral lip (Fig. 2B), and the mouth is surrounded by 16 oral papillae. The jaws differ in size and shape; dorsal being 1.5x the ventral. Dorsal jaw has a crescent-shaped base about 45 μm wide, with a large median tooth and small lateral teeth across the anterior surface along with ridges parallel to the median axes (Fig. 2C). The base of the ventral jaw is ovoid, smaller, 35 μm wide, also with a large median tooth and small lateral teeth across the anterior surface along with ridges parallel to the median axes. The dental formula is about 9/9 (4-1-4/4-1-4) and there is one pharyngeal sulcus. A pair of vasa deferentia or sperm tubes open separately into the glandular atrium; their exact entry has not been resolved. The tubular glandular atrium is about 0.7x the segment diameter in length; deferent lobes and a prostate gland are absent. A terete muscular atrium, about 0.2x segment diameter in length, and a sub-spherical muscular bursa length is 0.3x the segment diameter (Fig. 2D), and its atrium opens externally through the genital pore. The penis is eversible and when retracted, occupies the penial sheath that extends from the ental bursa back into the muscular atrium for about half the latter’s length. The spermatheca is about 0.7x segment diameter in length and consists of a spermathecal bulb (tubular when empty) about 0.2x the organ’s length and a terete muscular duct about 0.8x the organ’s length which opens externally through a spermathecal pore (Fig. 2D). The anterior excretory ducts open separately close to the median line on the dorsal surface of segment 3. Variations. Body length of adults vary from 2.0 mm to 3.0 mm depending on the response to the preservative before death. The dorsal jaw base varies from crescent-shaped to elongate oval, while the ventral jaw base is oval to banana-shaped. Measuring the width of the jaws was found to be less influenced by aspect than other jaw dimensions, e.g., height of the median tooth. The dorsal jaw widths ranged from 41.0 μm to 52.0 μm (N = 22, mean value 44.6 μm) and for the ventral jaw, 28.9 μm to 46.0 μm (N = 18, mean value 34.9 μm). Yamaguchi (1934: 197) drew the jaws and gave their magnification, and from his figures (7a & b) in a reprint, it was calculated that the dorsal jaw was 68 μm and the ventral 38 μm wide, respectively. Ridges parallel to the median axes on both jaws vary from distinct to absent (Fig. 2E, F); note the ventral jaw in figure 2F. The dental formula also varies due to the number of small teeth on each jaw, which range from 7/7 (3-1-3/3-1-3) to 11/13 (5-1-5/6-1-6). The glandular atrium is tubular and varies in appearance from straight to having two or more folds. As the atrium floats free in the coelom, other organs can push it into available spaces thus causing the folds. When the spermathecal bulb is filled with spermatozoa it can double in size, and the duct may temporarily contain spermatozoa causing it to dilate medially. Syntypes. Body lengths of the two syntypes, ZMH V-2912 a and 2912b are 2.3 mm and 1.8 mm long, respectively. Both specimens are slim terete, widest in segment 5 or 6, with their posterior discs being slightly narrower, and showing indistinct, partially autolyzed internal organs (Fig. 3A). Specimen 2912a has an everted pharynx with clearly visible jaws (Fig. 3B), and indistinguishable peristomial lobes. The constricted peristomium in specimen 2912b appears to have only 9, but actually 10 inwardly curved lobes (Fig. 3C); four dorsal lobes (d), two pairs are lateral lobes (l) and a ventral lip with a median emargination (v). The jaws are well preserved with distinct ridges parallel to their median axes, and the dorsal jaws are larger than the ventral ones (Fig. 3D,E). The base width of the dorsal jaws in 2912a and 2912b are 41 and 38 μm, respectively. The dental formula in 2912a and 2912b is 3-1-4/3- 1-4 and 3-1-3/3-1-4 (Fig. 3D,E), respectively. Diagnosis. Length about 2.5 mm, head width usually subequal segment 1, body club-shaped, segments distinct; dorsal lip four lobes, lateral lobes two pairs, ventral lip with median emargination; 16 oral papillae; jaws size different (dorsal 1.5x ventral), dorsal crescent-shaped, ventral ovoid, teeth single large median, small lateral, longitudinal striations, dental formula 9/9 (4-1-4/4-1-4); pharyngeal sulcus one; glandular atrium tubular, length 0.7x segment diameter; muscular atrium terete, length 0.7x segment diameter; bursa sub-spherical, length 0.25x segment diameter, penial sheath, ectal 0.1x muscular atrium, penis eversible; spermatheca shape club-like, length 0.7x segment diameter, duct shape terete, length 0.8x organ, bulb shape tubular (empty), length 0.2x organ. Type locality. Otaru, Hokkaido Island, Japan (Fig. 1, site No. 1), according to the Museum’s specimen ledger. Distribution. Specimens have only been recorded from Hokkaido Island, Japan,under the name of Stephanodrilus japonicus by Pierantoni (1912), Stephanodrilus (St.) ezoensis by Yamaguchi (1934) and of Cirrodrilus japonicus in the present study (Fig. 1). Host. Cambaroides japonicus (De Haan, 1841), the “Japanese crayfish” or “Nihon-zarigani” in Japanese. Habitat. Specimens have been observed alive on all parts of the exposed host and in the gill chambers. Additional information. Yamaguchi (1934: 198) observed that some individuals lacked a spermatheca but had eggs in segment 7, while in other specimens, spermatozoa were seen in the glandular atrium. Further studies of the life cycle of this species are needed to fully explain these observations., Published as part of Ohtaka, Akifumi & Gelder, Stuart R., 2023, A taxonomic reassessment of Cirrodrilus japonicus (Pierantoni, 1912) (Annelida, Clitellata, Branchiobdellida), pp. 557-565 in Zootaxa 5263 (4) on pages 559-560, DOI: 10.11646/zootaxa.5263.4.7, http://zenodo.org/record/7835969, {"references":["Pierantoni, U. (1912) Monografia dei Discodrilidae. Annuario del Museo Zoologico della Rigia Universita di Napoli, New Series, 3, 1 - 27.","Yamaguchi, H. (1934) Studies on Japanese Branchiobdellidae with some revisions on the classification. Journal of the Faculty of Science, Hokkaido University, Series VI, Zoology, 3, 177 - 219.","Yamaguchi, H. (1935 a) Family Branchiobdellidae (Class Clitellata). Fauna Nipponica. Vol. 6. (3). Sanseido Publishing Co., Tokyo, 37 pp. [in Japanese]","Yamaguchi, H. (1954) A catalogue of the aquatic Oligochaeta in Japan. Bulletin of the Hokkaido Gakugei Daigaku, 5, 93 - 120. [in Japanese]","Timm, T. (1991) Branchiobdellida (Oligochaeta) from the farthest South-East of the U. S. S. R. Zoologica Scripta, 20, 321 - 331. https: // doi. org / 10.1111 / j. 1463 - 6409.1991. tb 00297. x","Gelder, S. R. (1996) A review of the taxonomic nomenclature and a checklist of the species of the Branchiobdellae (Annelida: Clitellata). Proceedings of the Biological Society of Washington, 109, 653 - 663.","Gelder, S. R. (2019) Subclass Branchiobdellida. In: Thorp, J. H. & Rogers, D. C. (Eds.), Thorp and Covich's Freshwater Invertebrates. Vol. 4. Key to Palaearctic Fauna. 4 th Edition. Academic Press, London, pp. 483 - 491.","Yamaguchi, H. (1935 b) On the Branchiobdellidae, a special group of Oligochaeta. Botany and Zoology, Tokyo, 3, 552 - 560. [in Japanese]","Gelder, S. R. & Ohtaka, A. (2002) A review of the oriental branchiobdellidans (Annelida: Clitellata) with reference to the rediscovered slide collection of Prof. Hideji Yamaguchi. Species Diversity, 7, 333 - 344. https: // doi. org / 10.12782 / specdiv. 7.333","Ohtaka, A. (2010) Community conservation. In: Kawai, T. & Takahata, M. (Eds.), Biology of Crayfish. Hokkaido Daigaku Shuppankai, Sapporo, pp. 445 - 475. [in Japanese]","Ohtaka, A., Gelder, S. R. & Peterson, S. M. (2020) A catalog and assessment of Prof. Hideji Yamaguchi's slide collection of branchiobdellidans (Annelida: Clitellata) with the identification of syntypes. Zoosymposia, 17, 159 - 187. https: // doi. org / 10.11646 / zoosymposia. 17.1.14","International Commission on Zoological Nomenclature (1999) International Code of Zoological Nomenclature. 4 th Edition. Available from: http: // www. nhm. ac. uk / hosted-sites / iczn / code / (accessed 15 October 2022) https: // doi. org / 10.5479 / si. 00963801.124 - 3631.1"]}

融雪期の尾瀬において積雪が赤褐色に呈することが観察され，これはアカシボと呼ばれている．アカシボの実体を捉えるため，尾瀬ヶ原で採集後，現地ですみやかにアカシボ粒子の内容物を光学顕微鏡で観察し，アカシボの形成過程を調べた．また過去に尾瀬沼，および青森県の多雪地域で採集された赤褐色雪についても，尾瀬ヶ原との比較観察を行った．その結果，多雪地帯の融雪時に現れる，酸化鉄の赤褐色雪の原因として，アカシボ粒子の中心に含まれる細菌が深く関与していることが示唆された．この結果は，アカシボ粒子は細菌群集であるとの先行研究結果を支持する．, This article outlines optical structural characteristics of microbial communities associated with red snow and Akashibo with a focus on bacteria. Observations by optical microscope of the Akashibo particle of snow in Oze region has been suggested that bacterial community in red snow tends to be dominated in organisms.

Pristina multiseta sp. nov. (Figs 1–4) Material examined. Holotype. NSMT-An 1876, a sexually mature specimen whole-mounted on slide, 15 July 2007, coll. A. Ohtaka. Type locality. Paddy field in Nagayama, Shizukuishi Town, Iwate Prefecture, Japan (39.7469°N, 140.9644°E). Paratypes. NSMT-An 1877, a whole-mounted mature specimen; NSMT-An 1878, a sagittally-sectioned mature specimen; locality, date and collector the same as for the holotype. Other material examined. 12 sexually mature and one immature specimens mounted on slides and three mature, sagittally-sectioned specimens; locality, date and collector the same as for the holotype. Three mature and two immature specimens from a paddy field in Hata, Takashima City, Shiga Prefecture, Japan (35.2923°N, 135.9339°E), 24 July 2015, coll. M. J. Grygier. Etymology. The specific name refers to high number of dorsal chaetae in the present species. Diagnosis. Body length of single zooid 1.5–3.0 mm in fixed state. Prostomium forming a short proboscis. Dorsal chaetal bundles with 3–5 smooth hairs and 2–5 shortly bifid needles in anterior segments. Ventral chaetae in IV through VII enlarged. No modified genital chaetae. Stomach widening in anterior half of VIII, lined with column-shaped and glandular epithelium embedded in a blood plexus. Male duct with short vas deferens and tubular atrium, opening ventrolaterally in VIII. Blood vessels surrounding ectal half of atrium. Spermatheca with large ampulla and short and conical duct, opening on the chaetal line behind 6/7. Description. In fixed state, body length 1.5–3.0 mm, width 0.15–0.25 mm at clitellum and 0.13–0.17 mm at middle of body, 25–34 segments. No budding zone observed. No eyes. Prostomium forming a short proboscis (Fig. 1A–D): length 24–61 µm, diameter 10–16 µm, shorter than frontal width of segment I. Segments II to VI biannulate (Fig. 1A), each with short anterior and long, chaetaebearing posterior annuli. Genital segments longer than nongenital ones. Clitellum conspicuous, from 2/3 VII to end of IX; ventral side of body in VIII–IX indented longitudinally and slightly swollen at male pores laterally in VIII (Fig. 1A). Body wall 3–6 µm thick except for clitellum which has up to 10 µm high glandular epidermis. Coelomocytes scattered throughout the segments, spherical, 4–5 µm in diameter. Pharynx in II and III, dorsal wall up to 7 µm thick, slightly thicker than ventral wall (Fig. 1E). Pharyngo-esophageal glands developed dorsally in II–IV, each 12–15 µm high (Fig. 1E). Esophagus in IV through VII, 15–24µm wide with wall 4–6 µm thick. Esophagus widening and forming stomach in anterior half of VIII. Stomach gradually (Fig. 1E) or abruptly widening (Fig. 4A), up to 80–96 µm wide and lined with glandular and column-shaped inner epithelium, 20–25µm tall and 3–5 µm wide (Fig. 1F). Blood vessels developed on stomach, penetrating epithelium between the individual cells of the stomach. From IX on gut 70–100 µm wide with thin (5–8µm thick) wall. Chloragocytes beginning in V with single cells of less than 8 µm high, covering the alimentary canal. Transverse vessels forming loops in IV–VI (Fig. 1E). Dorsal chaetal bundles (Fig. 2A) consisting of hair and needle chaetae, both beginning in II. Hair chaetae smooth under examination with 1000× using oil immersion lens, 3–5 per bundle, 106–200 µm long in preclitellar segments; 1–3 per bundle, 64–170 µm long in postclitellar ones. Dorsal needle chaetae bayonet-shaped, with inconspicuous nodulus, weakly bent at 1/4 from the distal end (Fig. 2B), 2–5 per bundle, 35–50 µm long in preclitellar segments; 1–2 per bundle, 30–45 µm long in postclitellar ones. Distal ends of dorsal needle chaetae shortly bifid and slightly divergent; length of teeth almost as long as chaetal width. Upper teeth of dorsal needle chaetae as long as or a little longer and as thick as or a little thinner than weakly bent lower teeth (Fig. 2C, D). No intermediate teeth on dorsal needle chaetae. Ventral chaetae all bifid crotchets with slightly distal nodulus (Fig. 2E–K). In sexually mature worms, those in II and III smaller than those in the following segments, 3–6 per bundle, 48–56 µm long, upper tooth slightly longer and almost as thick as lower one (Fig. 2E, F); those in IV–VII longer and thicker than those in the rest of segments (Fig. 2G–J), 2–5 per bundle, 60–70 µm long, 2.0–2.5 µm thick, distal teeth longer and almost as thick as lower ones; ventral chaetae in IV and VII longer and thicker than those in V and VI, with distal teeth 1.5 to 2 times longer than lower teeth; ventral chaeta from VIII on 2–5 per bundle, 48–55 µm long, upper teeth as long as or a little longer and slightly thinner than lower ones (Fig. 2K). No modified genital chaetae at genital pores. No chaetophorous or associated glands in any ventral chaetal bundles. In immature worms, ventral chaetae in anterior segments 2–5 per bundle, 40–49 µm long, not especially longer or thicker in IV–VII; upper tooth almost as long as or a little longer and and almost as thick as lower. Gonads and copulatory organs paired. Testes in VII, ovaries in VIII. Male funnels on anterior face of 7/8, 30–40 µm in diameter (Figs 3, 4B). Vasa deferentia about 45 µm long, 6–8 µm thick, not winding, covered with glandular, 8–10 µm high, prostate cells, connected with atria apically (Fig. 3). Atria tubular, 50–64 µm long, 20–25 µm wide, with thick and glandular inner epithelium and thin muscular cover (Figs 3, 4B). Several thin blood vessels 1.5–2.2 µm in diameter surrounding ectal half of atria (Figs 3, 4C); it is unclear that they are arranged spirally or several circles separate from each other. Ejaculatory ducts not detected and male pores opening on papillae ventrolaterally in anterior part of VIII. Spermathecae in VII (Fig. 3); spermathecal ampullae large and ovoid, 64–128 µm long, 58–96 µm wide, with thin wall; spermathecal ducts well-distinguished from ampullae, short and conical, 16–18 µm long, 14–18 µm wide at junction with ampullae, opening on the chaetal line slightly behind anterior septa (Fig. 3). Loose sperm present in spermathecal ampullae. Sperm sac in VII–VIII. Egg sac in VIII–X. Variations. Length of proboscis varied from one forth to almost equal to frontal width in segment I (Fig. 1A–D). All sexually mature specimens examined (n=15) had enlarged ventral chaetae in IV through VII, and those in IV and VII were invariably larger than those in V and VI. The enlargement of ventral chaetae in V and/or VI varied from slightly larger than in II and III to nearly as large as in IV or VII. All sexually immature specimens examined had ventral chaetae of normal size, not larger than the rest. Distribution and habitat. The new species was collected from bottom surfaces of two inundated paddy fields in north and central parts of Japan, with water depth of both localities less than 10 cm. At the type locality in Iwate Prefecture, north Japan, three tubificines, Aulodrilus limnobius Bretscher, 1899, A. pigueti Kowalewski, 1914, Limnodrilus hoffmeisteri Claparède, 1862, and two naidines, Nais pardalis Piguet, 1906 and Slavina appendiculata (d’Udekem, 1855), were found together with the present species., Published as part of Ohtaka, Akifumi, 2022, Pristina multiseta sp. nov. (Annelida: Clitellata: Oligochaeta: Naididae: Pristininae) from Paddy Fields in Japan, pp. 95-100 in Species Diversity 27 (1) on pages 95-98, DOI: 10.12782/specdiv.27.95, http://zenodo.org/record/7175499, {"references":["Piguet, E. 1906. Observations sur les Naididees et revision systematique de quelques especes de cette famille. Revue Suisse Zoologie 14: 185 - 315."]}

Ohtaka, Akifumi (2022): Pristina multiseta sp. nov. (Annelida: Clitellata: Oligochaeta: Naididae: Pristininae) from Paddy Fields in Japan. Species Diversity 27 (1): 95-100, DOI: 10.12782/specdiv.27.95, URL: http://dx.doi.org/10.12782/specdiv.27.95

Aulodrilus pigueti Kowalewski, 1914 (Figures 13, 14) Aulodrilus pigueti Kowalewski, 1914: 625, fig 12. Aulodrilus pigueti Kowalewski: Hrabě 1981: 72, pl 11, figs 16–21, pl 12, figs 1–6; Brinkhurst et al. 1990: 908, fig. 2A; Finogenova & Arkhipova 1994: 13, figs 14–17; Pinder & Brinkhurst 2000: 46; Arslan & Sahin 2003: 278, fig 4. Aulodrilus remex Stephenson, 1921: 753, pl XXVIII, figs. 2–6; 1923: 107, figs 42–45; Aiyer 1929: 81, pl VI, figs 1–10; Naidu 1965: 470, fig 3a–e. Aulodrilus kashi Mehra, 1922: 946, figs 1–11; Stephenson 1923: 509. Aulodrilus prothecatus Chen, 1940: 68, fig 22. Aulodrilus tchadensis Lauzanne, 1968: 102, figs 12–13. Material examined. Japan: 5 immature specimens, offshore O-numa, Nanae Town, Hokkaido (10–12 m depth), 1 June 2008. 3 immature specimens, rice paddy in Iwaihana, Hachimantai City, Iwate Prefecture, 15 July 2007. 3 immature specimens, offshore Lake Izunma, Tome City, Miyagi Prefecture (1.5 m depth), 7 June 2008. 1 immature specimen, Kabukuri-numa Marsh, Tome City, Miyagi Prefecture, 7 June 2008. 3 mature specimens, Nikatsutsumi reservoir, Maki Town, Niigata Prefecture, 7 Oct. 1982. 1 immature specimen, a stream in Saitama City, Saitama Prefecture, Aug. 2005, coll. T. Torii. 2 immature specimens, littoral Lake Hinuma, Ibaraki prefecture, 9 Aug. 1982, coll. H. Morino. 4 mature and 178 immature specimens, offshore Lake Kitaura, Ibaraki Prefecture (6 m depth), 3 July, 9 Aug. 1980, 20 Jan., 20 May, 22 June, 16 July, 26 Aug., 29 Sep., 21 Oct., 19, 26 Nov., 24 Dec. 1982; 24 June, 14 Feb., 15 Mar., 14 Apr., 17 May, 25 June, 14 July, 19 Aug. 1983; 20 Jan., 14 June, 16 July, 17 Aug., 14 Sep. 1984; 17 June 1985. 4 immature specimens, Mizuhara, Lake Kitaura, Ibaraki Prefecture, 11 Dec. 1980; 9 June 1981. 5 immature specimens, offshore Lake Kasumigaura, 9 Aug. 1983, 9 Feb. 2011. 3 mature and 2 immature specimens, offshore Lake Suwa, Nagano Prefecture (5.5 m depth), 18 Oct. 1980; 9 Aug. 2006, coll. H. Fukuhara. 2 immature specimens, Lake Kahoku-gata, Ishikawa Prefecture, 11 Aug. 1999, coll. M. Nishino. 3 immature specimens, Yamanoshita Bay, south basin of Lake Biwa, Otsu City, Shiga Prefecture, 3 Oct. 1992. 2 immature specimens, Mizorogaike Marsh, Kyoto City, Kyoto Prefecture, 1 Nov. 2004, coll. Y. Murakami. 1 immature specimen, River Kitafune, Hirata City, Shimane Prefecture, 6 Nov. 1993. Littoral Lake Ikeda, Ibusuki City, Kagoshima Prefecture (10 m depth), 15 July 1998. Altogether 10 mature and 112 immature specimens from Japan. U.S.A.: 16 immature specimens, Coeur d’Alene Lake, Idaho, 24 June 2004, coll. K. Kuwabara (S. V. Fend collection). 2 immature specimens, Cosumnes River, San Francisco Bay Delta, California, (date and collector unknown) (S. V. Fend collection). Description. Description of Japanese specimens in mature and preserved states: 6–9 mm length, about 0.25 mm width in anterior segments; up to 62 segments. Posterior 1/5–1/7 of body without chaetae and unsegmented, with numerous transverse wrinkles. Prostomium bluntly conical. Pharynx covered by a thin layer of pharyngeal glands. Intestine suddenly widens in VII. Chloragogen cells on gut from VI or VII on. Transverse vessels forming complicated loops in I–VI. Forming a mud tube with mucus and foreign matter. Dorsal chaetal bundles consist of hairs and bifid or oar-shaped chaetae. Dorsal hairs smooth and slightly sigmoid, beginning in III or IV in immature specimens but in III in mature ones: 2–8 per bundle, 70–125 µm long. Dorsal crotchets in anterior segments (Fig. 13A,B) 6–11 per bundle, 46–80 µm long, with distal nodulus and with upper tooth shorter and thinner than lower one; replaced by 4–8 oar-shaped chaetae (Fig. 13C,D,G–K) from VII to X on. Oar-shaped chaetae 50–82 µm long. Distal, oar-shaped part 4.1–5.7 µm wide; chaeta with nodulus at 1/3 from distal end, bent backward slightly at 1/4 from distal end (Fig. 13D). The distal part rounded and slightly concave with a swollen edge (Fig. 13C,J,K). Ventral chaetae (Fig. 13E) all bifid crotchets with nodulus at 1/3 from distal end and with parallel teeth, with upper tooth about 2/3 times longer and much thinner than lower one; 8–12 per bundle, 53–70 µm long in anterior segments, 4–7 per bundle and 46–60 µm long in posterior ones. Penial chaetae (Fig. 13F) in VII when mature; 1–3 per bundle (usually 2), 130–158 µm long, much larger than other, somatic crotchets. Distal end hollow and spoon-shaped. Clitellum (Fig. 14A) in 1/2 VI–VIII, conspicuous, except around male pores. Paired testes at V and VI, with former pair smaller than the latter one. Paired ovaries in VII. Male funnels large, about 90 µm in diameter. Vasa deferentia (Fig. 14A) about 140 µm long, 20 µm wide, not winding, somewhat thinner near atria; connected with atria apically. Atria globular or ovoid in shape, 90 µm long and 70 µm wide, with thick and glandular inner epithelium (Fig. 14D). Prostate glands solid, slightly smaller than atria, connected through short stalk at lateral sides of atria. Penes conical and as large as atrium when protruding, consisting of non-glandular, loose tissues and thin inner and outer epithelia, opening into large ventromedian male bursa at middle of VII (Fig. 14C,E). Large penial chaetophores (Fig. 14A, F), 80 µm long, 70 µm wide, located posterior to penes in VII, consisting of a layer of tall glandular cells surrounding penial chaetae and thin muscular coverings; opening into posterior side of male bursa. Accessory glands formed by several clusters of glandular cap cells attached to dorsal side of the penial chaetophore (Fig. 14A). Female funnel small and thin. Sperm sac restricted to VII, ovisac in VII and VIII. Spermatheca in VI (Fig. 14A); ampulla large and globular or ovoid, and duct well marked off from ampulla, opening at chaetal line in VI ventrolaterally (Fig. 14B). Sperm diffuse in spermathecal ampulla. Remarks. Oar-shaped chaetae in dorsal bundles usually begin to appear in VII or VIII, and they completely replace bifid crotchets from VIII–XI on. Therefore, some 'transitional' chaetal bundles in VII–X have both bifid and oar-shaped chaetae, and occasionally their intermediates (Figs. 13G–I), in addition to hair chaetae. Replacement of bifid chaetae by oar-shaped chaetae proceeds from medial to lateral in each chaetal bundle. Paired testes were observed in V and VI in all mature specimens examined. Because segment V had no efferent duct, the testes of this segment are thought to be functionless. Large penes and glandular cap cells on penial chaetophores found in the present specimens agree well with earlier descriptions of this species (Kowalewski 1914; Ohtaka & Usman, 1997). Several Aulodrilus species with oar-shaped chaetae in dorsal bundles have been described. Among them, A. remex Stephenson, 1921, A. kashi Mehra, 1922, A. prothecatus Chen, 1940 and A. tchadensis Lauzanne, 1968 have been regarded as junior synonyms of A. pigueti by several authors (Chekanovskaya 1962; Brinkhurst 1963, 1971; Brinkhurst et al. 1990; Finogenova & Arkhipova 1994; Ohtaka & Usman 1997). They share rounded oar-shaped chaetae in dorsal bundles, ovoid or bean-shaped atria, penes set in a median male bursa, and spoon-shaped penial chaetae. Cap cells on penial chaetophores are also found in the descriptions of A. remex by Aiyer (1929) and A. prothecatus by Chen (1940). A sightly swollen edge and concavity in the oar-shaped portion found in the Japanese specimens of A. pigueti were also confirmed in SEM micrographs of Russian specimens by Finogenova & Arkhipova (1994) and those of Indonesian specimens by Ohtaka & Usman (1997). Chen (1940) and Aiyer (1929) described no true penes, but instead described atrial ducts winding in large penial sacs for A. prothecatus and A. remex, respectively. Hrabě (1981) also described the atrium as ending in a very small penis, which extends into a long outlet duct in A. pigueti. These atrial ducts should be everted and protruded, forming the large pseudopenes found in the present study. Aulodrilus acutus Ohtaka & Usman, 1997 has tapering oar-shaped chaetae in dorsal bundles. This species resembles A. pigueti in having a median male bursa and globular atrium, but it differs from A. pigueti in lacking penial chaetae. Distribution. A. pigueti is cosmopolitan (Brinkhurst 1971). In Japan, this species has been widespread in mesoeutrophic lakes as well as paddy fields (Ohtaka 2014; 2018b). Aulodrilus pigueti and its relatives are common in Southeast Asia and the south Asian region (Stephenson 1921; Mehra 1922; Ohtaka & Usman 1997; Ohtaka 2018a). Although no molecular approach has been used in the taxonomy and phylogeny of the nominal A. pigueti and its related taxa, it is probable that there are multiple lineages within the species., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 18-21, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489, {"references":["Kowalewski, M. (1914) Rodzaj Aulodrilus Bretscher, 1899 I jego przedstawicieli. Bulletin of the International Academy of Science and Letters, Cracow, 54, 598 - 604.","Hrabe, S. (1981) Vodni malostetinatci (Oligochaeta) Ceskoslovenska. Acta Universitatis Carolinae. Biologica, 1979, 1 - 167.","Brinkhurst, R. O., Qi, S. & Liang, Y. (1990) The aquatic Oligochaeta from the People's Republic of China. Canadian Journal of Zoology, 68, 901 - 916. https: // doi. org / 10.1139 / z 90 - 131","Finogenova, N. P. & Arkhipova, N. R. (1994) Morphology of some species of the genus Aulodrilus Bretscher. Hydrobiologia, 278, 7 - 15. https: // doi. org / 10.1007 / 978 - 94 - 011 - 0842 - 3 _ 2","Pinder, A. M. & Brinkhurst, R. O. (2000) A review of the Tubificidae (Annelida: Oligochaeta) from Australian inland waters. Memoirs of Museum Victoria, 58, 39 - 75. https: // doi. org / 10.24199 / j. mmv. 2000.58.3","Arslan, N. & Sahin, Y. (2003) Two new records of Aulodrilus Bretscher, 1899 (Oligochaeta, Tubificidae) for the Turkish fauna. Turkish Journal of Zoology, 27, 275 - 280.","Stephenson, J. (1921) Oligochaeta from Manipur, the Laccadive Islands, Mysore, and other parts of India. Records of the Indian Museum, 22, 745 - 768. https: // doi. org / 10.5962 / bhl. part. 1484","Aiyer, K. S. P. (1929) On the sexual organs of the tubificid worm Aulodrilus remex Steph. Records of the Indian Museum, 31, 81 - 85.","Naidu, K. V. (1965) Studies on the freshwater Oligochaeta of South India. II. Tubificidae. Hydrobiologia, 26, 463 - 483. https: // doi. org / 10.1007 / BF 00045539","Mehra, H. R. (1922) Two new Indian species of the little known genus Aulodrilus Bretscher. Proceedings of the Zoological Society of London, 59, 943 - 954.","Stephenson, J. (1923) The Fauna of British India, including Ceylon and Burma. Oligochaeta. Taylor and Francis, London, 518 pp.","Chen, Y. (1940) Taxonomy and faunal relations of the limnic Oligochaeta of China. Contributions of the Biological Laboratory of the Science Society of China, Zoology, 14, 1 - 131.","Lauzanne, L. (1968) Inventaire preliminaire des oligochetes du Lac Tchad. Cahiers ORSTOM serie Hydrobiologie, 11, 83 - 110.","Ohtaka, A. & Usman, R. (1997) Records of tubificid oligochaetes from Padang, west Sumatra, Indonesia, with description of a new species of Aulodrilus Bretscher. Species Diversity, 2, 145 - 154. https: // doi. org / 10.12782 / specdiv. 2.145","Chekanovskaya, O. V. (1962) Aquatic Oligochaeta of the USSR, Akademiya Nauk SSSR Publishers, Moscow, Leningrad. English Translation 1981. Amerind Publishing Co. Pvt. Ltd, New Delhi, 513 pp.","Brinkhurst, R. O. (1963) Taxonomical studies on the Tubificidae (Annelida, Oligochaeta). Internationale Revue der gesamten Hydrobiologie. Systematische Beihefte, 2, 1 - 89.","Brinkhurst, R. O. (1971) Part 2. Systematics, 8. Family Tubificidae. In: Brinkhurst, R. O. & Jamieson, B. G. M. (Eds.), \" Aquatic Oligochaeta of the World \". Oliver and Boyd, Edinburgh, pp. 444 - 625.","Ohtaka, A. (2014) Profundal oligochaete faunas (Annelida, Clitellata) in Japanese lakes. Zoosymposia, 9, 24 - 35. https: // doi. org / 10.11646 / zoosymposia. 9.1.7","Ohtaka, A. (2018 b) Aquatic microdrile oligochaete fauna (Annelida, Clitellata) in paddy fields of Japan. Japanese Journal of Benthology, 73, 48 - 56. [in Japanese with English abstract] https: // doi. org / 10.5179 / benthos. 73.48","Ohtaka, A. (2018 a) Aquatic oligochaete fauna (Annelida, Clitellata) in Lake Tonle Sap and adjacent waters in Cambodia. Limnology, 19, 367 - 373. https: // doi. org / 10.1007 / s 10201 - 018 - 0543 - 5"]}

Aulodrilus limnobius Bretscher, 1899 (Figures 1, 2) Aulodrilus limnobius Bretscher, 1899: 388. Aulodrilus limnobius Bretscher: Michaelsen 1900: 55; Piguet & Bretscher 1913: 58; Brinkhurst 1963: 66; 1965: 150, figs 9–10; 1971: 524, fig 8.23 G, H; 1986: 191; Brinkhurst & Cook 1966: 19, fig 7 T, U; Brinkhurst 1971: 524, figs 8.23 G, H; Hrabě 1981: 72; Davis 1982: 24, fig 8; Giani et al. 1984: 20, fig 2 C; Finogenova & Arkhipova 1994: 8, figs 1, 3, 4, 5, 19; Pinder & Brinkhurst 2000: 45. Paranais tenuis Cernosvitov, 1937: 143, figs 21–24. Material examined. Japan: 30 immature specimens, Chubetsu-numa at 1790 m alt. of Mt. Chubetsu-dake, Taisetu Mountains, Hokkaido, 26 July 1983. 8 immature specimens, Lake Takkobu, Kushiro City, Hokkaido, 23 July 2003, coll. T. Ito. 12 immature specimens, Lake Bankei-numa at 910 m alt. of Mt. Soranuma-dake, Sapporo City, Hokkaido, 8 Aug. 1982, 2 July 1983. 3 immature specimens, offshore Lake Okotanpe, Chitose City, Hokkaido (15–20 m in depth), 4 Aug. 1984. 13 mature and 10 immature specimens, rice paddy in Nozawa, Aomori City, Aomori Prefecture, 28 June, 2007. 4 immature specimens, rice paddy in Kanagi, Goshogawara City, Aomori Prefecture, 1 July 2000. 3 immature specimens, Lake Hiyamizu-numa, Tsugaru City, 1 July 2007. 10 immature specimens, rice paddy in Inakadate Village, Aomori Prefecture, 3 June 2011. 8 immature specimens, rice paddy in Utarube, Towada City, Aomori Prefecture, 5 June 2011. 3 mature and 4 immature specimens, rice paddy in Shin-hoshi, Hirosaki City, Aomori Prefecture, 29 June, 2014. 10 mature and 25 immature specimens, rice paddy in Zatoishi, Hirosaki City, Aomori Prefecture, 18 June 2011. 5 immature specimens, rice paddy in Orikasa, Hirosaki City, Aomori Prefecture, 25 June 2011. 5 mature and 15 immature specimens, rice paddy in Ichoda, Hirosaki City, Aomori Prefecture, 25 June 2011. 13 immature specimens, a marsh in Sakamoto, Hirosaki City, Aomori Prefecture, 25 Sep. 2011. 5 mature and 7 immature specimens, rice paddy in Ohkawara, Kuroishi City, Aomori Prefecture, 16 Aug. 2011. 3 immature specimens, Aseishigawa Reservoir, Kuroishi City, Aomri Prefecture, 4 Aug. 2014. 5 mature and 7 immature specimens, rice paddy in Shichinohe Town, Aomori Prefecture, 24 June 2007, 16 Aug. 2011. 20 immature specimens, rice paddy in Ishizawa, Gonohe Town, Aomori Prefecture, 16 Aug. 2011. 5 immature specimens, rice paddy in Muranaka, San-nohe Town, Aomori Prefecture, 16 Aug. 2011. 10 mature and 20 immature specimens, rice paddy in Iwaihana, Hachimantai City, Iwate Prefecture, 15 July 2007. 2 immature specimens, Lake Hachiro-gata, Akita Prefecture (3.6m depth), 9 July, 2005. 1 immature specimen, a marsh in Osawa near Lake Tazawa, Senboku City, Akita Prefecture, 29 Sep. 2007. 3 mature and 20 immature specimens, rice paddy in Gojome Town, Akita Prefecture, 17 July 2011. 10 mature and 9 immature specimens, rice paddy in Hinai, Odate City, Akita Prefecture, 22 July 2011. 5 immature specimens, rice paddy in Akafuchi, Kazuno City, Akita Prefecture, 16 July, 2007. 100 mature, 20 immature specimens, rice paddy in Tajiri, Osaki City, Miyagi Prefecture, 25 Jul. 2007, coll. M. Kawase. 5 mature and 18 immature specimens, rice paddy in Tome City, Miyagi Prefecture, 27 May 2007. 3 mature specimens, rice paddy in Fujishima, Tsuruoka City, Yamagata Prefecture, 30 June 2006, coll. M. Kawase. 1 immature specimen, rice paddy in Obanazawa City, Yamagata Prefecture, 9 Aug. 1990. 5 immature specimens, rice paddy in Tomioka City, Gunma Prefecture, 16 Aug. 1985. 2 mature and 28 immature specimens, rice paddy in Oki, Takasaki City, Gunma Prefecture, 24 July 1995. 4 mature specimens, a small current in Ozegahara mire, Gunma Prefecture, 26 Jul. 1995, 8 May 1998. 3 mature and 10 immature specimens, rice paddy in Hotaka, Azumino City, Nagano Prefecture, 3 Aug. 2007. 1 immature specimen, off Hayasaki, Lake Biwa, Shiga Prefecture (33 m in depth), 29 Sep. 1992. 3 immature specimens, off Wani, L. Biwa, Shiga Prefecture, 13 Apr. 1993. 2 immature specimens, Zeze Park, Otsu City, Shiga Prefecture, 9 July, 1999. 10 mature and 14 immature specimens, rice paddy in Hiruta, Yasu City, Shiga Prefecture, 1 June 2009, coll. M.J. Grygier. 4 immature specimens, Ukasho, Yasuki City, Shimane Prefecture, 2 Mar. 2015, coll. N. Kado. 1 immature specimen, rice paddy in Nangoku City, Kochi Prefecture, 24 Mar 2007. 1 immature specimen, Isahaya Bay, Saga Prefecture, 11 Dec. 2000, coll. M. Azuma. Altogether 191 mature and 357 immature specimens from Japan. China: 1 immature specimen, offshore Lake Erhai, Yunnan Province, 13 May 1992, coll. M. Nishino. U.S.A.: 2 immature specimens, Oregon, U. S.A. (detailed collection data unknown), coll. R. O. Brinkhurst. 12 immature specimens, Yakima River, Washington (detailed locality unknown), 29 Oct. 1987, coll. S. V. Fend. 8 mature specimens, Tuolumne River, San Joaquin, California, coll. S. V. Fend. Russia: 2 immature specimens, a nameless stream near Khabarovsk in the tributary of Amur River, 20 Sep. 1992. Description. In fixed state, body length 10–13 mm, width 0.28 mm at middle of body, with up to 130 segments. Posterior 1/7–1/8 of body without chaetae and unsegmented, with many transverse furrows. Prostomium bluntly conical: length less than half of the width in segment I. Body wall 15–25 µm thick, uneven, with several transverse furrows in each segment. Pharynx in II and III, dorsal wall up to 50 µm thick, much thicker than ventral wall. Pharyngeal glands weakly developed. Intestine with thin wall, and with spacious cavity in middle and posterior segments. Chloragogen cells less than 15 µm in height from VI on, a thin layer on gut. Transverse vessels forming complicated loops in II–VII, thick in VIII and IX as hearts (Fig. 1E). Chaetae all bifid crotchets; the form, size and number not different between dorsal and ventral bundles. In several anterior segments, chaetae (Fig. 1 A) up to 9 per bundle, 41–50 µm long, slightly shorter, thicker and more strongly curved than those in the remaining segments; nodulus situated distal to midpoint, and distal teeth parallel: upper tooth about half as long as, and much thinner than lower one. From VII or VIII on, chaetae up to 7 per bundle, 43–58 µm long, with nodulus at 1/3 or less from distal end, distal ends with lateral wings (Fig. 1 B, C); distal teeth parallel, with upper tooth more than half as long as and much thinner than the lower one. Lateral wings on chaetae made up by lateral expansions along the axis on the convex side of chaeta (Fig. 1D), extending from slightly distal to nodulus to base of the upper tooth. Maximum width of lateral wings 2.4–2.9 µm. Dorsal and ventral chaetae in II and III often fewer (2 or 3 per bundle) than those in later segments. Ventral chaetae in genital segments not modified. Clitellum surround the segments from 1/2 VI to end of VIII; the genital segments longer than the rest. Testes two pairs, in V and VI; latter pair larger than the former, and ovaries one pair in VII (Fig. 1F). Male funnels small, 50 µm in diameter. Vasa deferentia about 200 µm long and 30 µm wide, winding in the middle course, connected with atria apically. Atria stoutly tubular, 130 µm long by 60 µm wide; the inner epithelium tall and glandular. Prostate glands large, connected with atria laterally through a short stalk. Ejaculatory ducts not detected. Penes large in deep and folded chambers (Fig. 1F), which open separately, just lateral to ventral chaetal bundles in VII. Spermathecae in VI, opening laterally and anterior to the dorsal chaetal bundles (Fig. 1F); ampullae ovoid and ducts short. Loose sperm found in the ampullae. Sperm sac in V–VII. Egg sac in VI–VII. Making a tight tube from detritus together with mucus secreted from the body wall. Body not coiled up when a live worm is removed from mud tube and stimulated. Cocoon spindle to ovoid in shape, 520–600 µm long by 300–400 µm wide, covered with fine mineral particles (Fig. 2A). Operculae of cocoon 40–60 µm in diameter, dis- tinct on one end of the long axis, but somewhat inconspicuous in the opposite one. The cocoons invariably contain a single embryo which occupies the whole volume of the cocoon (Fig. 2B). Remarks. This species was distinguished by the absence of hair chaetae and presence of prominent lateral wings on the bifid chaetae. The form of male reproductive organs in the present specimens agrees with the descriptions by Hrabě (1981), Giani et al. (1984) and Finogenova & Arkhipova (1994). Distribution. This is a cosmopolitan species (Brinkhurst 1971). In Japan it is common in lakes and ponds, especially shallow waters. These are often the most abundant oligochaetes in paddy fields in Japan (Ohtaka 2018b)., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 2-5, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489, {"references":["Bretscher, K. (1899) Beitrag zur Kenntnis der Oligochaetenfauna der Schweiz. Revue Suisse de Zoologie, 6, 369 - 426. https: // doi. org / 10.5962 / bhl. part. 82518","Michaelsen, W. (1900) Oligochaeta. Das Tierreich, Berlin, 10, 1 - 575.","Piguet, E. & Bretscher, K. (1913) Oligochaetes. Fasc. 7 Catalogue des invertebres de la Suisse. Museum d'Histoire naturelle de Geneve, 1913, 214.","Brinkhurst, R. O. (1963) Taxonomical studies on the Tubificidae (Annelida, Oligochaeta). Internationale Revue der gesamten Hydrobiologie. Systematische Beihefte, 2, 1 - 89.","Brinkhurst, R. O. (1965) Studies on the North American aquatic Oligochaeta II: Tubificidae. Proceedings of the Academy of Natural Sciences of Philadelphia, 117, 117 - 172.","Brinkhurst, R. O. & Cook, D. G. (1966) Studies on the North American aquatic Oligochaeta. III. Lumbriculidae and additional notes and records of other families. Proceedings of the Academy of Natural Sciences of Philadelphia, 118, 1 - 33.","Brinkhurst, R. O. (1971) Part 2. Systematics, 8. Family Tubificidae. In: Brinkhurst, R. O. & Jamieson, B. G. M. (Eds.), \" Aquatic Oligochaeta of the World \". Oliver and Boyd, Edinburgh, pp. 444 - 625.","Hrabe, S. (1981) Vodni malostetinatci (Oligochaeta) Ceskoslovenska. Acta Universitatis Carolinae. Biologica, 1979, 1 - 167.","Davis, J. R. (1982) New records of aquatic Oligochaeta from Texas, with observation on their ecological characteristics. Hydrobiologia, 96, 15 - 29. https: // doi. org / 10.1007 / BF 00006276","Giani, N., Martinez-Ansemil, E. & Brinkhurst, R. O. (1984) Revision du statut taxonomique des Aulodrilinae (Tubificidae, Oligochaeta). Bulletin de la Societe d'Histoire Naturelle de Toulouse, 120, 17 - 20.","Finogenova, N. P. & Arkhipova, N. R. (1994) Morphology of some species of the genus Aulodrilus Bretscher. Hydrobiologia, 278, 7 - 15. https: // doi. org / 10.1007 / 978 - 94 - 011 - 0842 - 3 _ 2","Pinder, A. M. & Brinkhurst, R. O. (2000) A review of the Tubificidae (Annelida: Oligochaeta) from Australian inland waters. Memoirs of Museum Victoria, 58, 39 - 75. https: // doi. org / 10.24199 / j. mmv. 2000.58.3","Cernosvitov, L. (1937) Notes sur les Oligochaeta (Naididees et Enchytraeidees) de l'Argentine. Anales del Museo Argentino de Ciencias Naturales \" Bernardino Rivadavia \", 39, 135 - 157.","Ohtaka, A. (2018 b) Aquatic microdrile oligochaete fauna (Annelida, Clitellata) in paddy fields of Japan. Japanese Journal of Benthology, 73, 48 - 56. [in Japanese with English abstract] https: // doi. org / 10.5179 / benthos. 73.48"]}

Aulodrilus dentosus sp. nov. (Figures 9, 10) Holotype. NSMT-An 625, a mature specimen, 22 June 1982, coll. H. Kikuchi. Anterior part of the body sagittally sectioned and mounted on two slides and the posterior one whole-mounted on another slide. Type locality. Offshore Lake Kitaura, Ibaraki Prefecture, Japan (36.016N, 140.566E), 6 m deep with muddy bottom. Paratypes. NSMT-An 626, a cross-sectioned mature specimen from the type locality on one slide, 16 July 1982, coll. H. Kikuchi; NSMT-An 627, a whole-mounted mature specimen from the type locality, 22 June, 1982, coll. H. Kikuchi. Other material examined. Japan: 3 immature specimens, offshore Lake Toro, Shibecha Town, Hokkaido, 6 June 2000, coll. T. Ito. 5 mature and 20 immature specimens, offshore Lake Takkobu, Kushiro City, Hokkaido, 23 July 2003, coll. T. Ito. 6 immature specimens, littoral Lake Barato, Sapporo City, Hokkaido, 12 Oct. 1983. 5 immature specimens, littoral Lake Ogawara, Kamikita Town, Aomori Prefecture, 21 Sep. 2003. 2 immature specimens, offshore Lake Hachiro-gata, Akita Prefecture (3.6 m depth), 9 July, 2005. 1 immature specimen, offshore Lake Izunuma, Tome City, Miyagi Prefecture, 7 June 2008. 42 mature and 87 immature specimens, offshore Lake Kitaura (type locality), 29 May, 14 June, 3 July 1980; 28 Oct., 20 Nov., 26 Dec. 1981, 16 Mar. 1982; 19 Apr., 20 May, 22 June, 16 July, 26 Aug., 29 Sep., 26 Nov. 1982; 14 Apr., 17 May, 25 June, 14 July, 3 Aug., 15 Dec. 1983; 14 Feb., 18 May, 14 June, 16 July, 17 Aug., 14 Sep. 1984; 5 Jan. 1985. 3 immature specimens, Mizuhara, Lake Kitaura, Ibaraki Prefecture, July 1981. 10 immature specimens, offshore Lake Kasumigaura, Ibaraki Prefecture, 10 Jan.1984; 9 Oct. 1985; 9 Feb. 2011, coll. T. Iwakuma. 3 immature specimens, offshore Lake Inba-numa, Chiba Prefecture, 9 Mar. 2009. 3 mature and 2 immature specimens, offshore Lake Kahoku-gata, Ishikawa Prefecture, 11 Aug. 1999, coll. M. Nishino. 2 mature and 4 immature specimens, offshore Lake Suwa, Nagano Prefecture, 18 Oct. 1980. 2 immature specimens, offshore Lake Yogo, Nagahama City, Shiga Prefecture, 7 May 2000, coll. M. Nishino. 8 immature specimens, offshore Lake Koyama-ike, Torrori City Torrori Prefecture, 16 Mar. 2010. 2 immature specimens, Kanna Reservoir, Ginoza Village, Okinawa Island, Okinawa Prefecture, 14 May 2018, collector unknown. Altogether 55 mature and 158 immature specimens. Etymology. The specific epithet refers to the form of the distal ends of the dorsal chaetae, having several teeth. Description. In fixed state, length 10–20 mm, maximum width 0.36 mm in clitellum, 0.2–0.27 mm in mid-segments; 85–125 segments. Prostomium bluntly conical. Posterior segments (less than 1/10 of body length) without chaetae. No secondary annulation, but many narrow transverse furrows present. In anterior segments, epidermis 13–20 µm thick with many glandular cells staining deeply with hematoxylin. Pharynx in II and III; pharyngeal glands weakly developed dorsally (Fig. 10A). Chloragogen cells from VII, 5–10 µm in height, thinly covering gut. Intestine more or less widening in VII. Clusters of pear-shaped cells, 20–30 µm in height, present around ventral nerve cord in III–V. Transverse vessels forming loops in II–V. All dorsal chaetal bundles, beginning in II, with hairs and crotchets. Hairs smooth, slightly sigmoid, about twice as long as crotchets in the same respective bundles; 5–8 per bundle, 150–172 µm long in anterior segments and 2–5 per bundle, 104–130 µm long in posterior segments. Dorsal crotchets (Fig. 9A–C) weakly sigmoid in shape with distal nodulus; 7–8 per bundle, 60–68 µm long in anterior segments, 2–5 per bundle, 50–64 µm long in posterior ones. Distal end of dorsal crotchets bifid or divided into several fine and blunt teeth. In some anterior bundles (mostly II and III), distal teeth frequently bifid (Fig. 9E) or pectinate with long lateral teeth and short intermediate teeth (Fig. 9F). In mid-segments, several (4–8) digitiform teeth arranged in a single row, showing pectinate condition (Fig. 9G,H,L,M). Distal teeth often rudimentary in posterior bundles (Fig. 9I,J). Ventral chaetae (Fig. 9D) all bifid crotchets with nodulus slightly distal to middle: 9–15 per bundle, 58–68 µm long in anterior segments and 2–10 per bundle, 50–60 µm long in posterior ones; upper tooth of the ventral crotchets about half as long as and slightly thinner than lower ones (Fig. 9K). No lateral expansion on dorsal or ventral crotchets. In sexually mature specimens, ventral chaetae in VII (segment having male pore) not modified but reduced in number or absent. Clitellum from 1/2VI to end of VIII, conspicuous, broadly flattened ventrally; epidermis thick (up to 30 µm) and glandular. Gonads and copulatory organs (Fig. 10A,B) paired. Testes and ovaries paired respectively in VI and VII. Additional testes sometimes in V (Fig. 10A). Male funnels not large. Vasa deferentia about 260 µm long, not winding, connected with atria apically. Atria stoutly tubular in shape, 220 µm long, 80 µm wide, with high and glandular inner epithelium (Fig. 10B,E). Prostate gland large and solid, laterally connected to atrium by narrow (18 µm wide) junction (Fig. 10F). Ejaculatory ducts not detected. Penes rounded conical in shape, set in spacious copulatory bursa (Fig. 10B), opening ventrolaterally near middle of VII, immediately anterior to the chaetal bundle (Fig. 10D). Spermathecae in VI, opening ventrolaterally at mid-segment (Fig. 10B, C); ampullae large, globular or ovoid, 120–220 µm in diameter, containing 3–7 loose sperm masses; spermathecal ducts 30–50 µm long, short but well-defined from ampullae. Sperm sac in VI and VII. Egg sac in VII and VIII. Remarks. Aulodrilus dentosus sp. nov. resembles A. pluriseta, A. japonicus or A. apeniatus in having hair chaetae beginning in II and pectinate chaetae in the dorsal bundles, but it is clearly distinguished from the congeners in having dorsal crotchets with multiple digitiform teeth of similar length and arranged in one direction. In contrast, distal ends of dorsal crotchets are bifid in A. pluriseta, with multiple upper teeth in A. japonicus, and with fine intermediate teeth between upper and lower teeth in A. apeniatus. As to the distal shape of the dorsal crotchets, the present species more closely resembles A. pectinatus. However, the present species has no modified genital chaetae. Its hair chaetae invariably begin in II, whereas A. pectinatus has spoon-shaped penial chaetae and lacks hair chaetae in II and III (Aiyer 1928; Brinkhurst 1971). Furthermore, the number of distal teeth in dorsal crotchets of A. dentosus sp. nov. (5–8) is higher than that of A. pectinatus (usually 2–3 and rarely 4) (Aiyer 1928). Structure of male duct of the present species resembles that of A. limnobius in the stoutly tubular atrium, which is slightly shorter than the vas deferens, and directly connected with penis without an ejaculatory duct. Distribution. It has been recorded from muddy bottoms in shallow and eutrophic lakes and lagoons in Hokkaido, Honshu, and Okinawa islands in Japan (Ohtaka 2014 under the name of Aulodrilus sp.). Aulodrilus sp. from Lake Hachiro-gata (Ohtaka 2006), from Lake Izu-numa (Ohtaka 2009), from Lake Kitaura (Ohtaka & Kikuchi 1997), from Lake Toro (Ito et al. 2002), from Lake Ogawara (Ohtaka & Sato 2005), from Lake Takkobu (Takamura et al. 2009), and from Lake Inaba-numa (Ohtaka et al. 2010) correspond to this species. The localities include both freshwater and brackish habitats. The present species can withstand salinity to some degree., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 13-16, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489, {"references":["Aiyer, K. S. P. (1928) On a new species the oligochaete genus Aulodrilus Bretscher. Records of the Indian Museum, 30, 345 - 352.","Brinkhurst, R. O. (1971) Part 2. Systematics, 8. Family Tubificidae. In: Brinkhurst, R. O. & Jamieson, B. G. M. (Eds.), \" Aquatic Oligochaeta of the World \". Oliver and Boyd, Edinburgh, pp. 444 - 625.","Ohtaka, A. (2014) Profundal oligochaete faunas (Annelida, Clitellata) in Japanese lakes. Zoosymposia, 9, 24 - 35. https: // doi. org / 10.11646 / zoosymposia. 9.1.7","Ohtaka, A. (2006) Aquatic oligochaete fauna in offshore Lake Hachiro-gata, Akita Prefecture, northern Japan. Biology of Inland Waters, 21, 11 - 19. [in Japanese with English abstract]","Ohtaka, A. (2009) Records of aquatic oligochaetes (Annelida, Clitellata) from Lake Izunuma and Kabukurinuma Marsh, Miyagi Prefecture, northern Japan. Izunuma-Uchinuma Wetland Researches, 3, 1 - 11. [in Japanese with English abstract] https: // doi. org / 10.20745 / izu. 3.0 _ 1","Ohtaka, A. & Kikuchi, H. (1997) Composition and abundance of zoobenthos in the profundal region of Lake Kitaura, central Japan during 1980 - 1985, with special reference to oligochaetes. Publications of Itako Hydrobiological Station, Faculty of Science, Ibaraki University, 9, 1 - 14.","Ito, T., Ohtaka, A., Fukuhara, H., Ito, T., Wu, J., Mikami, H., Ishikawa, K., Igarashi, S., Nagahara, K., Takano, T. & Yasutomi, R. (2002) Benthic macroinvertebrates in Lake Toro and Shirarutoro, Kushiro Mire, Hokkaido, northern Japan. Biology of Inland Waters, 17, 17 - 24. [in Japanese with English abstract]","Ohtaka, A. & Sato, C. (2005) Bottom fauna in Lake Ogawara, Aomori Prefecture, northern Japan, with special reference to oligochaetes. Journal of the Natural History of Aomori, 10, 1 - 7. [in Japanese with English abstract]","Takamura, N., Ito, T., Ueno, R., Ohtaka, A., Wakana, I., Nakagawa, K., Ueno, Y. & Nakajima, H. (2009) Environmental gradients determining distribution of benthic macroinvertebrates in Lake Takkobu, Kushiro wetland, northern Japan. Ecological Research, 24, 371 - 381. https: // doi. org / 10.1007 / s 11284 - 008 - 0514 - 0"]}

Genus Aulodrilus Bretscher, 1899 Type species. Aulodrilus limnobius Bretscher, 1899 Diagnosis. Medium sized worms with numerous chaetae (up to 16 in ventral bundles) and unsegmented tails. Short and slightly sigmoid hair chaetae present or absent. Lateral wings on crotchet chaetae present or absent. Vasa deferentia usually about as long as atrium, with uniform width, connected to apical end of atrium. Atria globular to tubular in shape, laterally joined by a solid, single prostate gland through a short stalk. Protrusible, true penes usually present without cuticular sheaths or eversible pseudopenes. Loose sperm masses in spermathecae, not forming spermatozeugmata. Coelomocytes sparse or absent. Duplication and forward shift of genital organs often occur. Single embryo in cocoon. Dwelling in mud tubes. The diagnosis is modified from Brinkhurst (1971), Hrabě (1981) and Finogenova and Arkhipova (1994). Remarks. Brinkhurst (1971) listed three diagnostic characters of the genus Aulodrilus by which he afforded subfamilial rank: 1) prostates attached to atria by broad bases, 2) sperm in bundles (masses) in spermathecae, 3) coelomocytes absent. Subsequently Giani et al. (1984) corrected the first feature, because prostate glands of A. pluriseta and A. limnobius are stalked on the atrium like those of Tubificinae, and they invalidated the subfamily Aulodrilinae. At the genus level, along with other two characters listed above, short vas deferentia, globular or cylindrical atria, large eversible pseudopenes, and unsegmented posterior ends have been used as diagnostic characters (Brinkhurst 1971; Hrabě 1981; Finogenova & Arkhipova 1994). Finogenova and Arkhipova (1994) emphasized a forward shift of reproductive organs and multiplication of gonads as diagnostic characters of Aulodrilus. It is reasonable to regard the subfamily Aulodrilinae invalid and to maintain the genus Aulodrilus in the subfamily Tubificinae. Among Tubificinae, lateral expansions of somatic chaetae occur only in this genus; however, not all congeners have this feature, and species also vary in expression of the other characters listed above. The genusdiagnostic characters of Aulodrilus are evaluated in the "Discussion"., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on page 2, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489, {"references":["Bretscher, K. (1899) Beitrag zur Kenntnis der Oligochaetenfauna der Schweiz. Revue Suisse de Zoologie, 6, 369 - 426. https: // doi. org / 10.5962 / bhl. part. 82518","Brinkhurst, R. O. (1971) Part 2. Systematics, 8. Family Tubificidae. In: Brinkhurst, R. O. & Jamieson, B. G. M. (Eds.), \" Aquatic Oligochaeta of the World \". Oliver and Boyd, Edinburgh, pp. 444 - 625.","Hrabe, S. (1981) Vodni malostetinatci (Oligochaeta) Ceskoslovenska. Acta Universitatis Carolinae. Biologica, 1979, 1 - 167.","Finogenova, N. P. & Arkhipova, N. R. (1994) Morphology of some species of the genus Aulodrilus Bretscher. Hydrobiologia, 278, 7 - 15. https: // doi. org / 10.1007 / 978 - 94 - 011 - 0842 - 3 _ 2","Giani, N., Martinez-Ansemil, E. & Brinkhurst, R. O. (1984) Revision du statut taxonomique des Aulodrilinae (Tubificidae, Oligochaeta). Bulletin de la Societe d'Histoire Naturelle de Toulouse, 120, 17 - 20."]}

Aulodrilus japonicus Yamaguchi, 1953 (Figures 6, 7, 8) Aulodrilus japonicus Yamaguchi, 1953: 298, fig 12m, pl VIII, figs 5–7. Aulodrilus japonicus Yamaguchi: Brinkhurst 1963: 70; Yamaguchi 1965: 542; Hrabě 1981: 70, pl XI, figs 5–10; Liang & Xie 1997: 390, fig 5; Finogenova & Arkhipova 1994: 8, figs 3, 6–10, 18; Timm & Všivkova 2007: 32, fig 6. Ohtaka & Chen 2010: 105. Aulodrilus pluriseta (Piguet): Brinkhurst 1971: 525, fig 8.23J (in part); Wang & Liang 2001: 36, fig. d, e. Material examined. Japan: 20 immature specimens, a pond in Wakkasakanai, Toyotomi Town, Hokkaido, 29 Oct. 1984. 2 immature specimens, Shinoro-Shinkawa River, Sapporo, Hokkaido, 6 May 1983. 128 mature and 500 immature specimens, Maruyama, Sapporo City, Hokkaido, 4, 19 Oct., 30 Dec. 1983; 23 Apr., 18 May, 2, 28 July, 15 Aug. 12 Oct., 4 Nov. 1984; 19 Apr. 10 May, 20 June, 27 July, 11, 28 Aug., 19 Sep., 1985. 6 immature specimens, Nishioka reservoir, Sapporo City, Hokkaido, 1 Sep. 1982, 28 Apr. 1983. 2 mature and 7 immature specimens, littoral Lake Shikotsu, Hokkaido, 30 May 1979, coll. T. Ito. 2 immature specimens, littoral Lake O-numa, Nanae Town, Hokkaido, 9 May 1984. 5 immature specimens, Mitake Park, Hirosaki City, Aomori Prefecture, 17 July 1992. 3 immature specimens, a stream in Tokiwano, Hirosaki City, Aomori Prefecture, 15 May 2009. 20 immature specimens, rice paddy in Sakamoto, Hirosaki City, Aomori Prefecture, 16 July, 25 Sep. 2011; 1 Sep. 2012. 10 immature specimens, Osawa near Lake Tazawa, Senboku City, Akita Prefecture, 29 Sep. 2007. 1 immature specimen, Ushiawari River on Mt. Chokai, Yuza Town, Yamagata Prefecture, 29 July 2015.1 immature specimen, a brook in Gobono, Obanazawa City, Yamagata Prefecture, 8 May 1984. 1 immature specimen, a stream in Naganeyama hill, Obanazawa City, Yamagata Prefecture, 9 Aug. 1990. 3 immature specimens, offshore Lake Onogawa, Kita-Shiobara Village, Fukushima Prefecture (2.5 m depth), 9 July, 2010. 1 immature specimen, offshore Lake Yunoko, Nikko City, Tochigi Prefecture (6 m in depth), 22 July 1988, coll. T. Iwakuma. 3 immature specimens, offshore Lake Maru-numa, Katashina Village, Gunma Prefecture (16.3 m depth), 21 Sep. 2009. 6 immature specimens, Saikawa River, Sano City, Tochigi Prefecture, 10 Nov. 1980. 3 immature specimens, River Takada, Tomioka City, Gunma Prefecture, 4 Apr. 1984. 5 immature specimens, littoral Lake Kizaki, Omachi City, Nagano Prefecture (5.3 m depth), 2 Aug. 2007. 4 immature specimens, Tsuya River, Yoro Town, Gifu Prefecture, 9 June 2005, coll. K. Tanida. 15 immature specimens, north basin of Lake Biwa (10–70 m deep, mud), 26 Jan. 1992 – 14 Feb. 1995. 7 immature specimens, a marsh in Hayasaki, Nagahama City, Shiga Prefecture, 29 Aug. 2002. 2 immature specimens, Mizorogaike Marsh, Kyoto City, Kyoto Prefecture, 1 Nov. 2004, coll. Y. Murakami. 10 immature specimens, Kitafune Stream, Izumo City, Shimane Prefecture, 6 Nov. 1993. 5 immature specimens, Rivers Kanna and Kesashi, Okinawa Is., Okinawa Prefecture, 7, 8 Aug. 1990, coll. M. Tsuchiya. Altogether 130 mature and 642 immature specimens from Japan. Taiwan : 1 immature specimen (ESRI-OA0009), a pond in Minchien, Nantou County, 10 Sep. 2008. U.K.: 1mature and 3 immature specimens, Bala Lake, N. Wales, 1962 (detailed collection data unknown), (R. O. Brinkhurst collection). Estonia: 25 immature specimens, aquarial culture at the Võrtsjärv Limnological Station, started in 2006 with specimens from the Emajõgi River, Tartu City, Estonia, coll. T. Timm. U.S.A. USNM 32648, 1 immature specimen from Sonoma County, California, 18 Sep. 1962, R.O. Brinkhurst collected and deposited as Aulodrilus pluriseta. 2 mature and 1 immature specimens, Santa Clara, California (exact locality unknown), 1 Apr. 2002, coll. S. V. Fend. 10 immature specimens, a stream near McMinnville, Oregon, 10 May, 2001, coll. S. V. Fend. 3 immature specimens, Coeur d’Alene Lake, Idaho, 24 June 2004, coll. J. Kuwabara (S. V. Fend collection). 5 immature specimens, Sacra- mento– San Joaquin River Delta, California, Oct. 2003, coll. W. Fields. 2 immature specimens, Cosumnes River, San Francisco Bay Delta, California (date and collector unknown) (S. V. Fend collection). Description. The following description is based on the topotypic specimens from Maruyama, Sapporo, Japan. Mature and living state: length 28–35 mm, width 0.3–0.5 mm in anterior segments; up to 150 segments. Body anteriorly dark red; posteriorly somewhat yellowish. Prostomium conical, more or less pointed. No secondary annulations. Posterior part of body (consisting of up to 45 segments) without chaetae, and the posterior end of about 0.4 mm without septa, loosely packed with coelomocytes. Pharynx in II and III; thick walls (20–25 µm) covered by a thin layer of pharyngeal glands. Chloragogen cells from posterior part of IV on, a thin tissue as far as VIII or IX, and then suddenly thickened. Intestine widens at X or XI. Contractile commissural vessels in VIII–IX. Dorsal vessel shifted ventrolaterally in X, located on the left side of ventral vessel. Nephridia from XI, elongate; ental part of narrow duct densely surrounded by large (up to 80 µm diameter) and spherical cells. Forming a loose and thick mud tube. Dorsal chaetal bundles consisting of hair and pectinate crotchets, both beginning in II. Hair chaetae smooth and slightly sigmoid, 4–7 per bundle, 90–207 µm long in anterior segments; 1–3 per bundle, 60–150 µm long in posterior ones. Dorsal crotchets (Fig. 6A) with distal nodulus, 5–9 per bundle, 76–110 µm long in anterior segments; 2–6 per bundle, 65–86 µm long in posterior ones; distal end with upper tooth split into 5–20 fine teeth which are arranged irregularly, and much thinner and shorter than single lower tooth (Fig. 6D, E, G, H). Ventral chaetae (Fig. 6B, C) bifid crotchets with distal nodulus, 8–13 per bundle, 75–112 µm long in anterior segments; 3–8 per bundle, 68–84 µm long in posterior segments; distal teeth parallel and lower tooth about twice longer and much thicker than upper one; one to several small teeth often occur laterally between upper and lower teeth (Fig. 6F). Distal parts of all dorsal and ventral crotchets with lateral expansions along the axis of chaeta. Ventral chaetae in spermathecal and penial segments of usual type, neither modified nor absent even in fully mature specimens. Clitellum more or less conspicuous, usually occupying from 2/3 IX to end of XI; ventral side flattened and slightly swollen laterally of male pores. Gonads and copulatory organs paired (Fig. 7A). Testes usually in VIII and IX, ovaries in X. In fully mature specimens, anterior pair of testes not as well developed as posterior testes and ovaries. Male funnels one pair on 9/10, large, 160 µm in diameter. Vasa deferentia about 600 µm long, winding and slightly stouter ectally than entally, connected with atrium apically. Atrium bean-shaped, 180–220 µm long, inner epithelium thick and glandular with basal nuclei (Fig. 7B). Prostate gland large, connected laterally with atrium through short and narrow stalk (Fig. 7C). Ejaculatory duct about 190 µm long, nearly as long as atrium, and swollen at middle (Fig. 7B). Penes short and conical, set in small depressed chambers, opening at lateral side of ventral chaetal bundle in X or rarely XI (Fig. 8B). Paired spermathecae usually in VIII and IX (Fig. 7A); anterior pair smaller than posterior one. Spermathecal ampullae globular or ovoid in shape. Spermathecal ducts short, well-marked off from ampullae, opening laterally at slightly behind anterior septa (Fig. 8A). Loose sperm masses present in spermathecal ampullae. Sperm sac usually in VIII–X. Egg sac restricted to ovarial segment. Variation. Variations related to multiplication of spermathecae and to shift in the segmental position of genital organs were found in the present specimens as follows. Of 28 mature specimens from the type locality in Sapporo, 24 had two pairs of spermathecae, one in VIII and another one in IX, and one pair of male ducts in X (Fig. 8C). One specimen showed the same arrangement of genital organs, but lacked the spermatheca on the left side in VIII. Two specimens had a third pair of spermathecae in VII, in addition to those in VIII and IX (Fig. 8D). One specimen had paired spermathecae in VII, IX, and X and the male duct in XI. In all cases examined, anterior spermathecal ampullae were smaller than posterior ones. Remarks. Since Yamaguchi (1953) described the present species based on immature specimens lacking genital organs except for gonads, the identity of this species has remained unclear for several decades (Brinkhurst 1963, 1971; Brinkhurst & Wetzel 1984). Brinkhurst (1971) once tentatively synonymized it with A. pluriseta (Piguet). Hrabě (1981) described the male duct for the first time and regarded A. japonicus as a distinct species. Then Finogenova & Arkhipova (1994), Liang & Xie (1997), and Timm & Všivkova (2007) redescribed the species based on specimens from continental Eurasia. The newly obtained Japanese specimens, including topotypes listed above, agree well with the previous descriptions both in chaetal and genital structures. A. japonicus differs from A. pluriseta in the following respects (corresponding condition of latter species in parentheses): upper teeth multiple in dorsal crotchets (both dorsal and ventral crotchets mostly bifid); vasa deferentia about three times longer than atria (slightly longer than atria); male ejaculatory ducts long, as long as atria (much shorter than atria); spermathecal ampullae ovoid, well distinguished from ducts (cylindrical and not well marked off from the ducts); wide midgut begins either in X or XI (VIII or IX); very thick chloragogen tissue appears in one segment before the beginning of midgut (chloragogen tissue thin throughout). Results of this examination confirmed that all specimens listed above have multiple upper teeth in the dorsal chaetae. The irregularly arranged, multiple upper teeth in the dorsal chaetae of A. japonicus are unique in oligochaetes, whereas such a condition is common in hooded hooks of capitellid polychaetes (e.g., Yabe & Mawatari 1998; Tomioka et al. 2016). Additional small teeth were often found in ventral chaetae on the lateral sides on the base of teeth branch in the SEM observation of topotypic specimens (Fig. 6F). Finogenova & Arkhipova (1994) presented this structure on Neva estuary specimens from western Russia. All mature Japanese specimens that were examined had more than one pair of spermathecae. Two pairs of spermathecae in VIII and IX are also confirmed in the Bala Lake specimen from northern Wales and in a Santa Clara specimen from North America. Multiple pairs of spermathecae, in VIII and IX and occasionally also in VI, were described for Czech material (Hrabě 1981) and for Chinese specimens (Liang & Xie 1997). Multiple pairs of spermathecae therefore appear to be the normal condition in A. japonicus. The long ejaculatory duct with a middle swelling is also unique in the genus. Gonads were found in VIII, IX, and X in the present specimens, as Yamaguchi (1953) described. In fully mature worms, gonads of IX (testes) and X (ovaries) were well developed, although those in VIII (testes) were rudimentary. The rudimentary testes were much smaller and without corresponding efferent ducts. They are thought to be functionless as in A. pluriseta (Naidu 1965), A. remex Stephenson, 1923 (Aiyer 1929), (a synonym of A. pigueti), and A. pigueti (present study). Distribution. Widespread. This species has been confused with A. pluriseta. For example, A. pluriseta of Wang & Liang (2001) should be ascribed to A. japonicus. USNM 32648, a California specimen registered as A. pluriseta, is confirmed to be A. japonicus in the present study. This is a common tubificine, at least in Japanese waters. Periodic samplings at a small, shallow pond in Maruyama, Sapporo (type locality) revealed that mature individuals of the present species appeared—in a low proportion (maximum 10%)—only during summer when water temperature was above15 °C (Ohtaka, unpublished data). Van den Hoek & Verdonschot (2005) also noted that mature specimens of A. japonicus were found only in July in the Netherlands., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 9-13, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489, {"references":["Yamaguchi, H. (1953) Studies on the aquatic Oligochaeta of Japan. VI. A systematic report, with some remarks on the classification and phylogeny of the Oligochaeta. Journal of the Faculty of Science, Hokkaido University, Series 6, Zoology, 11, 277 - 342.","Brinkhurst, R. O. (1963) Taxonomical studies on the Tubificidae (Annelida, Oligochaeta). Internationale Revue der gesamten Hydrobiologie. Systematische Beihefte, 2, 1 - 89.","Yamaguchi, H. (1965) Oligochaeta. In: Okada, K., Uchida, S. & Uchida, T. (Eds.), New Illustrated Encyclopedia of the Fauna of Japan. Vol. 1. Hokuryukan, Tokyo, pp. 537 - 548. [in Japanese]","Hrabe, S. (1981) Vodni malostetinatci (Oligochaeta) Ceskoslovenska. Acta Universitatis Carolinae. Biologica, 1979, 1 - 167.","Liang, Y. L. & Xie, Z. C. (1997) Aquatic Oligcochaeta from Wuling Mountains area. In: Song, D. X. (Ed.), Invertebrates of Wuling Mountains area, Southwestern China. Science Press, Beijing, pp. 383 - 394. [in Chinese with English abstract].","Finogenova, N. P. & Arkhipova, N. R. (1994) Morphology of some species of the genus Aulodrilus Bretscher. Hydrobiologia, 278, 7 - 15. https: // doi. org / 10.1007 / 978 - 94 - 011 - 0842 - 3 _ 2","Timm, T. & Vsivkova, T. S. (2007) Freshwater oligochaetes (Annelida, Clitellata) of Lake Hanka (Russia / China). Acta Hydrobiologica Sinica, 31 (Supplement), 25 - 35.","Ohtaka, A. & Chen, R. T. (2010) New records of a branchiobdellidan and four microdrile oligochaetes (Annelida: Clitellata) from inland waters of Taiwan. Taiwan Journal of Biodiversity, 12, 97 - 110. https: // doi. org / 10.7064 / TJB. 201001.0097","Brinkhurst, R. O. (1971) Part 2. Systematics, 8. Family Tubificidae. In: Brinkhurst, R. O. & Jamieson, B. G. M. (Eds.), \" Aquatic Oligochaeta of the World \". Oliver and Boyd, Edinburgh, pp. 444 - 625.","Wang, H. Z. & Liang, Y. (2001) A preliminary study of oligochaetes in Poyang Lake, the largest freshwater lake of China, and its vicinity, with description of a new species of Limnodrilus. Hydrobiologia, 463, 29 - 38. https: // doi. org / 10.1023 / A: 1013126918728","Brinkhurst, R. O. & Wetzel, M. J. (1984) Family Tubificidae. In: Brinkhurst, R. O. & Wetzel, M. J. (Eds.), Aquatic Oligochaeta of the World: Supplement. A catalogue of new freshwater species, descriptions and revisions. Canadian Technical Report of Hydrography and Ocean Sciences No. 44. IOS, Sidney, pp. 39 - 71.","Yabe, K. & Mawatari, S. F. (1998) Two new species of Capitellidae (Annelida: Polychaeta) from Hokkaido, northern Japan. Species Diversity, 3, 201 - 209. https: // doi. org / 10.12782 / specdiv. 3.201","Tomioka, S., Kondoh, T., Sato-Okoshi, W., Ito, K., Kakui, K. & Kajihara, H. (2016) Cosmopolitan or cryptic species? A case study of Capitella teleta (Annelida: Capitellidae). Zoological Science, 33 (5), 545 - 554. https: // doi. org / 10.2108 / zs 160059","Naidu, K. V. (1965) Studies on the freshwater Oligochaeta of South India. II. Tubificidae. Hydrobiologia, 26, 463 - 483. https: // doi. org / 10.1007 / BF 00045539","Stephenson, J. (1923) The Fauna of British India, including Ceylon and Burma. Oligochaeta. Taylor and Francis, London, 518 pp.","Aiyer, K. S. P. (1929) On the sexual organs of the tubificid worm Aulodrilus remex Steph. Records of the Indian Museum, 31, 81 - 85.","Van den Hoek, T. H. & Verdonschot, P. (2005) Distribution and ecology of Aulodrilus japonicus in The Netherlands (Oligochaeta: Tubificidae). Nederlandse Faunistische Mededelingen, 23, 103 - 112."]}

Aulodrilus cernosvitovi du Bois Reymond Marcus, 1947 (Figure 15) Aulodrilus cernosvitovi du Bois Reymond Marcus, 1947: pl. 2, figs 15–19, pl. 3. figs 20–21. Aulodrilus cernosvitovi du Bois Reymond Marcus: Howmiller 1974: 9, fig. 2. Aulodrilus pigueti Kowalewski: Brinkhurst 1971: 526, fig 8.23I (in part); Brinkhurst and Marchese 1987: 3157, fig. 1 (in part). Material examined. USNM 102745–102746, two whole-mounted mature specimens. Saladillo River, Santa Fé Province, Argentina, coll. E. de Drago and R. Regner in 1984. R. O. Brinkhurst identified and registered. They were used under the name of Aulodrilus pigueti in Brinkhurst & Marchese (1987). Brief description. Dorsal hairs from VI, 2–6 per bundle. Dorsal crotchets in anterior segments 7–15 per bundle, with upper tooth shorter and thinner than lower one. Dorsal bifid crotchets replaced by 5–9 oar-shaped chaetae from IX to X. Distal parts of oar-shaped chaetae oval to rhombic in shape with midribs (Fig. 15A,B). Ventral chaetae all bifid crotchets with upper tooth shorter and thinner than lower one, 8–14 per bundle in anterior segments. No lateral wings on chaetae. Male ducts in VII with short vasa deferentia and tubular atria, separately opening into male bursae in front of ventral chaetal bundles in VII (Fig. 15C). Ventral chaetae in atrial segment not modified, 6–8 per bundle. Single solid prostates as large and atria. Spermathecae absent in one specimen, USNM-102746, while present in VI in another USNM-102745. In the latter specimen, spermathecae ampullae large and spherical with loose sperms. Remarks. Aulodrilus cernosvitovi had once been regareded as a junior synonym of A. pigueti by Brinkhurst (1971); subsequently it has been regarded as a distinct species by Brinkhurst & Marchese (1989) and Ohtaka & Usman (1997). The present examination of non-type material of A. cernosvitovi from Argentina confirmed midribs on the oar-shaped chaetae, which is unique within the genus, and was described in the original description (du Bois Reymond Marcus 1947) and subsequent redescription (Howmiller 1974). In the present material, the midribs on the oar-shaped chaetae were not developed in anterior segments (Fig. 15A), although they become prominent in posterior segments, where the distal ends changed from oval to rhombic in shape (Fig. 15B). Tubular atria, separate openings of male pores in VII, and absence of penial chaetae, described in the original description were confirmed in the present examination; all of these are different from A. pigueti. In the figures (du Bois Reymond Marcus 1947: figs 20A,B, 21) of the original description of A. cernosvitovi, vasa deferentia are shorter than atria and they join with atria subapically. On the other hand, in the present material, vasa deferentia are as long as or longer than atria, and they join with atria almost apically. These characters could vary depending on the fixation and orientation. In addition, absence of spermathecae was described in the original description of A. cernosvitovi (du Bois Reymond Marcus 1947), while a pair of large spermathecae containing loose sperm was found in one of the two mature Argentine specimens examined in the present study. The presence or absence of spermathecae should be regareded as intraspecific variation in A. cernosvitovi. Distribution. Aulodrilus cernosvitovi has been recorded from Central to South America, including northern Brazil (du Bois Reymond Marcus 1947), Nicaragua (Howmiller 1974), and northern Argentina (Brinkhurst & Marchese 1987, under the name of A. pigueti; Brinkhurst & Marchese 1989; present study). Brinkhurst & Marchese (1989) recorded Aulodrilus pigueti along with Aulodrilus cernosvitovi in South and Central America. It is uncertain whether the record of A. pigueti of Brinkhurst & Marchese (1987) from Peru should be assigned to A.cernosvitovi or not., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 21-22, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489, {"references":["du Bois Reymond Marcus, E. (1947) Naidids and tubificids from Brazil. Comunicaciones zoologicas del Museo de Historia Natural de Montevideo, 47, 1 - 17, pls. I - III.","Howmiller, R. P. (1974) Some Naididae and Tubificidae from Central Africa. Hydrobiologia, 44, 1 - 12. https: // doi. org / 10.1007 / BF 00036152","Brinkhurst, R. O. (1971) Part 2. Systematics, 8. Family Tubificidae. In: Brinkhurst, R. O. & Jamieson, B. G. M. (Eds.), \" Aquatic Oligochaeta of the World \". Oliver and Boyd, Edinburgh, pp. 444 - 625.","Brinkhurst, R. O. & Marchese, M. R. (1987) A contribution to the taxonomy of the aquatic Oligochaeta (Haplotaxidae, Phreodrilidae, Tubificidae) of South America. Canadian Journal of Zoology, 65, 3154 - 3165. https: // doi. org / 10.1139 / z 87 - 474","Brinkhurst, R. O. & Marchese, M. R. (1989) Guide to the freshwater aquatic Oligochaeta of South and Central America. Asociacioin Ciencias natulares del Litoral, Coleccioin CLIMAX No 6. Asociacioin Ciencias natulares del Litoral, Santo Tomei, 179 pp.","Ohtaka, A. & Usman, R. (1997) Records of tubificid oligochaetes from Padang, west Sumatra, Indonesia, with description of a new species of Aulodrilus Bretscher. Species Diversity, 2, 145 - 154. https: // doi. org / 10.12782 / specdiv. 2.145"]}

Aulodrilus americanus Brinkhurst & Cook, 1966 (Figures 3, 4) Aulodrilus americanus Brinkhurst & Cook, 1966: 19, fig 7R, S. Aulodrilus americanus Brinkhurst & Cook: Brinkhurst 1971: 528, fig 8.23 A, B; 1986: 193. Material examined. Japan: 1 mature specimen, a spring-fed stream in the Hokkaido National Agricultural Experiment Station, Tsukisamu, Sapporo City, Hokkaido, 9 July 1983. Two immature specimens, spring-fed Ushiwatari stream on Mt. Chokai, Yuza Town, Yamagata Prefecture, 29 July 2015. 5 immature specimens, a brook in Ozegahara Mire, Gunma Prefecture, 8 May 1998. North America: 3 immature specimens, Coeur d’Alene Lake, Idaho, 24 June 2004, coll. J. Kuwabara (S. V. Fend collection). Description of Japanese material. A live (incomplete) individual 20 mm long and 0.38 mm wide in preclitellar segments, segments 42+. Body light red when living. Prostomium conical (Fig. 3F). No distinct secondary annulations. Pharynx in II–III, covered with a thin layer of pharyngeal glands. Chloragogen cells from VI on, thinly covering gut. No stomachal dilatation. Transverse blood vessels forming loops in II–VII, thick in VIII and IX. Individuals living in soft mud tube with adherent foreign matter. Chaetae all crotchets, with form, size and number not different between dorsal and ventral bundles. Those in anterior segments (II–V or II–VI, Fig. 3A–C) slightly longer than the following ones, 7–9 per bundle, 80–94 µm long, with distal nodulus and with rudimentary upper tooth or simple pointed distal end; those from VI or VII on (Fig. 3D,E) 4–6 per bundle, 48–62 µm long. Nodulus at 1/3 from distal end, and distal end brush-like with a series of teeth gradually decreasing in size from lower to upper (Fig. 4A,B). No lateral expansions in the chaetal shafts in any segments. No modified genital chaetae. Clitellum surround the segments from beginning of X to end of XII, with the wall 16–30 µm thick. Gonads and copulatory organs paired (Fig. 3G). Testes and ovaries attached respectively to posterior sides of septa 9/10 and 10/11. Male funnels large. Vasa deferentia short and not winding, 240 µm long and 20 µm wide, connected to apical end of atrium. Atria bean-shaped, 150 µm long and 80 µm in maximum diameter. Prostate glands as large as atria. Ejaculatory ducts not detected. Penes 90 µm long, 20 µm wide, two-layered with ordinary cuticular covering, and separate openings lateral to ventral chaetal line at middle of XI. Spermathecae in X, small (Fig. 3G); ampullae ovoid in shape, 70 µm long and 45 µm wide; ducts stout and well-marked off from the ampullae, about 100 µm long, 20–25 µm wide, opening laterally at middle of X. Sperm sac in X. Egg sac observed to extend as far back as XII. Remarks. All essential characteristics of the present Japanese material agree well with the original description (Brinkhurst & Cook 1966), the only account prior to this paper (subsequent accounts summarize data of the original description). Spermathecae were "not observed" (Brinkhurst & Cook 1966: 19) in the original material, whereas the single sexually mature Japanese specimen available to us had one pair of spermathecae. The spermathecal ampullae of the present material were small, but they contained sperm masses (Fig. 3G) and hence can be considered as completely formed. Occasional absence of spermathecae has been observed in other tubificines, for example, in Tubifex tubifex, Ilyodrilus templetoni (Brinkhurst 1971) and in Teneridrilus mastix (Brinkhurst 1978), and absence of spermathecae may be an intraspecific variation also in this species. Furthermore, Brinkhurst & Cook (1966) described eversible pseudopenes in the original description of Aulodrilus americanus, however, the present new material has true penes as defined by Baker and Brinkhurst (1981), because they are two-layered, solid structures, composed of the wall of the penial sac and end of the atrial wall, and have cuticular coverings The segmental position of the genital organs in A. americanus was not originally described, but the present specimen has genital organs located int the normal position of Tubificinae (male pores and spermathecal pores in XI and X, respectively). Unlike many other Aulodrilus species, extra testes were not found in the present specimen. Liang et al. (1998) showed no split of distal ends of chaetae and depicted a membrane between short upper and long lower teeth of chaetae from X on in their Aulodrilus americanus from China. The brush-like form of chaetae in A. americanus can be recognized in observation without high magnifications, and such chaetae appear from VI or VII. A. americanus reported by Liang et al. (1998) might not be A. americanus. The taxonomic position of their A. americanus should be considered provisional until the segmental location and accurate structure of the different types of chaetae has been reinvestigated in the reference material. Distribution. This species has been recorded in North America (Brinkhurst & Cook 1966; Brinkhurst 1967, 1978; Hiltunen 1967, 1969; Stimpson et al. 1975; Spencer 1980) and in Japan (Ohtaka, unpublished data in Timm 1999a), showing circum-Pacific distribution (Timm 1999a). These records are formally the first of this species in Japan. The Japanese habitats were cool waters, including spring-fed streams in Sapporo (water temperature 10.5°C), Ushiwatari stream in Yuza Town (12.3 °C), and a brook in a sphagnum bog of Ozegahara Mire, Gunma Prefecture. Differing from many other Aulodrilus species living in warm waters, the preference of A. americanus for cool-water habitats is apparently unique.

Aulodrilus paucichaeta Brinkhurst & Barbour, 1985 (Figure 16) Aulodrilus paucichaeta Brinkhurst & Barbour, 1985: 931, fig 1. Material examined. USNM 98228 (holotype), a whole-mounted mature specimen, Piscataway Creek, Maryland, U.S.A. 3 Oct. 1979, coll. M. T. Barbour. USNM 98229, 98230, 98232, 98234, 98236 (paratypes), five whole-mount- ed mature specimens, locality, date and collector the same as for the holotype. USNM 98235 (paratype), a mature specimen sagittally sectioned and mounted on two slides, locality, date and collector the same as for the holotype. Brief description of the type series. Anterior-most six segments distinctly biannulate, each with a short anteri- or and a long posterior annulus, the latter with chaetae (Fig. 16A). Posterior end of 0.3 mm in length without chaetae and unsegmented. Dorsal and ventral chaetae alike, each with distal nodulus and bifid, with the upper tooth shorter and thinner than the lower tooth (Fig. 16B–D). Chaetal bundles consist of 2–3 chaetae in preclitellar segments and single chaeta in postclitellar segments. In the paratype specimen (USNM 98232), ventral chaetae 105 µm long in II, becoming larger in posterior segments, up to 190 µm. A single ventral chaeta in X, no chaetae in XI in mature specimen (USNM 98232). No modified genital chaetae. Spermathecae and male ducts paired in X and XI, respectively. Male funnels large, 200–300 µm in diameter (Fig. 16E). Vasa deferentia (Fig. 16F) more than 2 mm long, uniformly 38 µm wide, winding and connected with atria apically. Atria (Fig. 16G) tubular, 250 µm long, 50–80 µm wide with a tall (up to 50 µm) and glandular inner epithelium and muscular coverings. Prostate glands divided into several distinct lobes, connected with atria entally through a single short stalk (Fig. 16G arrow). Ejaculatory duct not detected, atrium leading directly to a large spherical penis in a large penial sac (Fig. 16E). Male pores located ventrally on chaetal line of XI. Spermathecal ampullae large (Fig. 16E), spherical or ovoid in shape and 500 µm in maximum diameter, opening laterally to ventral chaeta in X without spermathecal duct (Fig. 16H). Within spermathecal ampullae, sperm arranged in ovoid to spindle-shaped spermatozeugmata with hyaline outer layer (Fig. 16I). Remarks. The present examination of the type series of Aulodrilus paucichaeta confirms the original description (Brinkhurst & Barbour 1985) in the following characters: few and robust, bifid chaetae with thick lower tooth, absence of modified genital chaetae and spermathecal ducts, lobed prostate glands and spherical penes in large and muscular penial sacs. On the other hand, the present examination found several differences from the original description. The original description noted the absence of ventral chaetae in IX in mature specimen, whereas a single ordinary chaeta was found in IX in one paratype specimen. The original description depicted a small and fusiform atrium and described prostate glands as attached to atria at one point, but not obviously stalked (Brinkhurst & Barbour 1985). However, the present reexamination confirmed that the atrium is tubular and the prostate gland is connected to the atrium by a short stalk (Fig. 15G). The original description stated that spermathecae are filled with sperm in bundles in mated specimens. However, the present examination suggests that sperms cells are arranged in ovoid to spindle-shaped capsules with a hyaline outer layer, similar to spermatozeugmata in many other tubificines. The very low number of chaetae and the extremely long and winding vas deferens are unique for Aulodrilus paucichaeta among species of the genus, suggesting that A. paucichaeta is not related closely to other congeners; this was also suggested by Finogenova & Arkhipova (1994), who highlighted the absence in this species of two characters which they considered diagnostic for the genus: the forward shift of genital organs and the lateral expansions of some chaetae, both absent in A. paucichaeta., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 23-24, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489, {"references":["Brinkhurst, R. O. & Barbour, M. T. (1985) A new species of Aulodrilus Bretscher (Oligochaeta: Tubificidae) from North America. Proceedings of the Biological Society Washington, 98, 931 - 934.","Finogenova, N. P. & Arkhipova, N. R. (1994) Morphology of some species of the genus Aulodrilus Bretscher. Hydrobiologia, 278, 7 - 15. https: // doi. org / 10.1007 / 978 - 94 - 011 - 0842 - 3 _ 2"]}

Aulodrilus aestivus sp. nov. (Figures 11, 12) Holotype. NSMT-An 628, a mature specimen, 20 July 1984, the anterior part of body sagittally sectioned and mounted on one slide and the posterior one whole-mounted on another slide. Type locality. Paddy field in Takasaki City, Gunma Prefecture, Japan (36.361N, 138.956E). Paratypes. Paratypes. NSMT-An 629, a whole-mounted specimen; NSMT-An 630, a cross-sectioned specimen; locality and date the same as for the holotype. Other material examined. Japan: 10 mature and 2 immature specimens, paddy field in Takasaki City, Gunma Prefecture (type locality), 20 July 1984. 7 mature and 5 immature specimens, paddy field in Gunma Town, Gunma Prefecture, 20 July 1984. 1 mature and 7 immature specimens, paddy field in Tomioka City, Gunma Prefecture, 16 Aug. 1985, 13 Aug. 2017. One mature specimen, paddy field in Izumo City, Shimane Prefecture, 24 July 2015, coll. N. Kado. Etymology. The specific epithet refers to the summers during which all the specimens examined were collected. Description. Fixed mature specimens: 8–15 mm length, 0.20–0.35 mm width, and 45–80 segments. Posterior end of 0.2–0.5 mm in length without septa, devoid of chaetae. Prostomium almost absent (Fig. 11B, C). Epidermis 6–10 µm thick, with glandular cells dense in anterior part. Pharynx in II and III, pharyngeal glands weakly developed (Fig. 11C). Alimentary canal abruptly widening in VIII or IX. Chloragogen cells from VII on, covering gut thinly. Intestinal wall thin in middle and posterior segments. Transverse vessels form loops in II–VI; thick in VII and VIII as hearts (Fig. 11B). Living animals in loose mud tube with mucus and foreign matter. Dorsal chaetal bundles consist of short hairs and bifid crotchets. Dorsal hairs beginning in either of IV–VIII, smooth and weakly curved (Fig. 11D); 2–6 per bundle, 60–90 µm long; the length less than twice that of crotchets in the same respective bundles. Dorsal crotchets in anterior segments (Fig. 11E) 4–13 per bundle and 42–62 µm long, with nodulus slightly distal and with parallel teeth, with the upper tooth 2/3–1/2 times longer and much thinner than the lower (Fig. 11H, I); those in posterior segments 2–5 per bundle and 33–44 µm long, more strongly curved, with nodulus situated at 1/3–1/4 from distal end, and lower teeth thickened more than those in anterior segments. Lower tooth of posterior dorsal crotchets sometimes rounded or divided into some short teeth (Fig. 11J, K). Ventral chaetae (Fig. 11F, G) all bifid crotchets 5–12 per bundle, 44–62 µm long in anterior segments; 3–7 per bundle, 36–42 µm long in posterior ones; distal shape and position of nodulus not different from dorsal crotchets. Number of ventral chaetae decreased in genital segments. No modified genital chaetae. In mature specimens, ventral chaetae in segment with male pore reduced in number or lost completely. No lateral expansions on chaetal shafts in dorsal or ventral chaetae. Clitellum conspicuous, usually extending from chaetal line of IX to slightly behind chaetal line of XI (Fig. 11A), but often shifted anteriorly from 1/2VI to VIII in accordance with shift of other genital organs. Testes and ovaries paired, usually in IX and X (Fig. 12A), sometimes in VI and VII, respectively. Male funnels small, 15–20 µm in diameter. Vasa deferentia 150–200 µm long, hardly winding, connected with atrium apically (Fig. 12A). Atria crescent-shaped, 120 µm long and 36 µm wide, with high and glandular inner epithelium (Fig. 12B). Prostate glands about as large as atria, connected to concave side of atria through short stalks. Penes long when protruded, opening close to each other within a large median male bursa situated in middle to posterior 1/3 of X (or VII) (Figs. 11A, 12A,E). Spermathecae (Fig. 12C) small, separately opening on small papillae anterior to the chaetae of IX (or VIII) and close to ventral nerve cord (Fig. 12D). Ampullae ovoid in shape, 35 µm long by 28 µm wide, with the wall 2–5 µm thick. Spermathecal ducts 30 µm long with thick wall. Loose sperm in the ampullae. Sperm sac extending anteriorly as far as V, with egg sac as far back as XII, both weakly developed. Variation. Two cases were found in the segmental position of genital organs among specimens examined (Fig. 17): one has testes and spermathecae in IX with ovaries and male pores in X (see description), and the other has testes and spermathecae in VI with ovaries and male pores in VII. Among specimens examined from the type locality (n =12), the former case (9 individuals) was more frequent than the latter (three individuals). No intermediate conditions between the two cases above have been found there. The clitellum always covered the segments having spermathecae and male pores, but varied in the segmental position in accordance with the position of genital organs. The beginning of dorsal hairs also varied in accordance with the position of the genital organs: The dorsal hairs began in IV, V, or VI in specimens having male pores in VII, and they began in VI, VII or VIII in those having male pores in X. Distribution. The present species has hitherto been collected in summer seasons from several inundated paddy fields in central and western parts of Japan. A congener, A. limnobius, has been collected in these localities together with another tubificine, Limnodrilus hoffmeisteri Claparède. Remarks. Aulodrilus aestivus sp. nov. is most similar to A. pigueti and A. acutus by the following characteristics: 1) male efferent ducts open into a median male bursa; and 2) dorsal hairs are absent in some anterior segments. However, the present species has neither oar-shaped chaetae nor blade-shaped chaetae in the dorsal bundles, which are characteristic, respectively, of A. pigueti and A. acutus. The crescent-shaped atrium of the present species is also different from the globular atria of A. pigueti and A. acutus. In contrast, the present species resembles A. pluriseta in having hair chaetae and bifid crotchets in dorsal bundles, and crescent-shaped atria. However, in the latter species, dorsal hair chaetae begin in II and male ducts open in line with the ventral chaetae, thus differing from the present species in which hair chaetae begin in IV–VIII and male ducts open into a median male bursa., Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 16-18, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489

Kahayandrilus gen. nov. Type species. Kahayandrilus tundaiensis sp. nov., fixed by original designation. Etymology. Named Kahayandrilus, referring to that the type species is a ‘worm’ (Greek drilus) from Kahayan River basin (masculine). Diagnosis. Moderate sized tubificines with long and coiled vasa deferentia, ovoid atrial ampullae, and long ejaculatory ducts with uniform width. Penes soπ and thickwalled, devoid of penial sheaths, set in penial pouches. Chaetae sigmoid bifids, similar in dorsal and ventral bundles. No modified genital chaetae. No spermathecae. Remarks. Kahayandrilus resembles Psammoryctides Hrabě, 1964 in having small, globular to ovoid atrial ampulla, long ejaculatory duct, and large penis set in a sac. However, Psammoryctides is defined by having wide and narrow parts in the ejaculatory ducts (Hrabě 1964; Brinkhurst and Jamieson 1971; Loden 1978), while in Kahayandrilus the ejaculatory duct is uniform in width throughout the course. In addition, hair and pectinate chaetae, and spermathecal chaetae were usually present in most Psammoryctides species, while they are absent in Kahayandrilus. Psammoryctides species are distributed in western Palaearctic and Nearctic regions, far from the Oriental Southeast Asia. Kahayandrilus resembles certain members in the genus Aulodrilus Bretscher, 1899, for example, A. pigueti Kowalewski, 1914 and A. acutus Ohtaka and Usman, 1997, in having ovoid atrial ampulla with solid prostate gland (Ohtaka and Usman 1997). However, in Aulodrilus species ejaculatory duct is shorter than atrial length or virtually absent, being different from Kahayandrilus in which ejaculatory duct is more than three times longer than atrial length. Aulodrilus also differs from Kahayandrilus in having shorter and non-winding vas deferens and large number of chaetae with shorter upper teeth (Brinkhurst and Jamieson 1971). Isochaetides Hrabě, 1966 emended by Brinkhurst (1981) resembles Kahayandrilus in having only bifid chaetae and weakly developed cuticle on penis as well as long ejaculatory duct described in I. curvisetosus (Brinkhurst and Cook, 1966) (q.v.). However, most members of Isochaetides have modified spermathecal chaetae and long tubular atria (Hrabě 1966; Brinhurst 1981), both of which are absent in Kahayandrilus. Some species in Varichaetadrilus Brinkhurst and Kathman, 1983, for example, V. fulleri Brinkhurst and Kathman, 1983 and V. psammophilus (Loden, 1977) (q.v.), have only bifid chaetae as in Kahayandrilus. However, Varichaetadrilus spp. have elongate atrium and cuticular sheaths at the distal end of large erectile penes (Brinkhurst and Kathman 1983), which are absent in Kahayandrilus. Several genera in other naidid subfamilies (Paranadrilus, Bothrioneurum, Jolydrilus, some Bacescuella (= Aktedrilus) and some Ainudrilus) lack spermathecae as in Kahayandrilus, but they have very different male ducts and other characters., Published as part of Ohtaka, Akifumi & Wulandari, Linda, 2016, Description of Kahayandrilus tundaiensis gen. et sp. nov. (Annelida: Clitellata: Tubificinae) from Central Kalimantan, Indonesia, pp. 43-47 in Species Diversity 21 (1) on pages 43-44, DOI: 10.12782/sd.21.1.043, http://zenodo.org/record/4583608, {"references":["Hrabe, S. 1964. On Peloscolex svirenkoi (Jarosenko) and some other species of the genus Peloscolex. Spisy Prirodovedecke fakulty University J. E. Purkyne v Brne 450: 101 - 112.","Brinkhurst, R. O. and Jamieson, B. G. M. 1971. Aquatic Oligochaeta of the World. Oliver and Boyd, Edinburgh, 860 pp.","Loden, M. S. 1978. A revision of the genus Psammoryctides (Oligochaeta Tubificidae) in North America. Proceedings of the Biological Society of Washington 91: 74 - 84.","Ohtaka, A. and Usman, R. 1997. Records of tubificid oligochaetes from Padang, West Sumatra, Indonesia, with description of a new species of Aulodrilus Bretscher. Species Diversity 2: 145 - 154.","Hrabe, S. 1966. New or insufficiently known species of the family Tubificidae. Publications de la Faculte des Sciences, de l'Universite J. E. Purkyne, Brno 450: 55 - 77.","Brinkhurst, R. O. 1981. A contribution to the taxonomy of the Tubificinae (Oligochaeta: Tubificidae). Proceedings of the Biological Society of Washington 94: 1048 - 1067.","Brinkhurst, R. O. and Cook, D. G. 1966. Studies on the North American aquatic Oligochaeta III: Lumbriculidae and additional notes and records of other families. Proceedings of the Academy of Natural Sciences of Philadelphia 118: 1 - 33.","Brinkhurst, R. O. and Kathman, R. D. 1983. Varichaetadrilus Brinkhurst, a new name for Varichaeta Brinkhurst, 1981, non Speiser, 1903, (Diptera) with a description of a new species V. fulleri. Proceedings of the Biological Society of Washington 96: 301 - 306.","Loden, M. S. 1977. Two new species of Limnodrilus (Oligochaeta: Tubificidae) from the southeastern United States. Transactions of the American Microscopical Society 96: 321 - 326."]}

Kahayandrilus tundaiensis sp. nov. (Figs 1–2) Type series. Holotype. MZB Oli. 0005, a whole-mounted unstained specimen from profundal bottom of Lake Tundai, depth 6 m, 3 May 2004. Paratypes, all from the type locality: MZB Oli. 0006, a whole-mounted unstained specimen, 3 May 2004; USNM 1283362–1283363, two wholemounted unstained specimens, 21 September 2004; ICHUM 5107–5111, two whole-mounted unstained, and one sagittally and two cross sectioned specimens, stained in hematoxylin and eosin, 3 May and 21 September 2004. Other material. Seventeen whole-mounted, six sagittally and two cross sectioned specimens from the type locality and nearby sites in Lake Tundai, depth 3–6 m, 3 May and 21 September 2004. Type locality. Profundal of Lake Tundai, Central Kalimantan, Indonesia. Etymology. The specific epithet is derived from the type locality, Lake Tundai, Central Kalimantan, Indonesia. Description. Body reddish in color when alive, not coiling up when stimulated. In mature and fixed state, body 13–18 mm long, 0.35–0.46 mm wide in segment VIII, and 0.50–0.63 mm in segment XI, with ventral side of XI flattened and oπen swollen laterally (Fig. 1A). Segments up to 110. Body wall naked and without pigments. No secondary annulation. Prostomium bluntly conical, 140–160 µm long and 90–120 µm wide in fixed individuals. Clitellum formed by a single layer of glandular cells 24–32 µm in height, extended from beginning of XI to the end of XII and less developed around male pores (Fig. 1A). One pair of male pores opening ventrally on the chaetal line at mid-XI (Fig. 2F). All chaetae bifurcated crotchets, their shape and number not different in ventral and dorsal bundles. Chaetae in preclitellar segments (Fig. 1B) 4–7 per bundle, 80–96µm long, with nodulus at 1/3 from distal end and with upper tooth longer and as thick as the lower; those in postclitellar segments (Fig. 1C) 1–3 per bundle (mostly 2 in middle segments and mostly 1 in posterior segments), 64–85 µm long, with nodulus at 1/3–1/4 from distal end and with upper tooth a little longer or slightly shorter and thinner than the lower. No intermediate teeth. In fully mature worms, both dorsal and ventral chaetae decreased to 1–3 per bundle in X and oπen entirely missing in XI. No modified genital chaetae. Coelomocytes not observed. Commissural blood vessels connecting dorsal and ventral vessels from I through VII, forming loops in each segment. Pharynx in II and III, with high epithelium and several clusters of glandular cells dorsally (Fig. 2A). Pharyngeal glands dorsally in IV and V. Chloragogen cells on gut from VI on. Intestine from VIII on, not abruptly widening. Male genitalia paired. One pair of testes in X and one pair of ovaries in XI. Sperm sac from IX to XI, containing complete sperms. Egg sac extending backwards to XIII. Sperm funnel large, 150 µm in diameter, located in ventral part of septum 10/11. Vas deferens long and coiled up, 12–16 µm wide throughout course, with lumen 6–8 µm, ciliated, entering atrium apically (Fig. 1D). Atrial ampulla ovoid, 110 µm long, maximum 80 µm wide, with thick (16–30 µm) and granulated inner epithelium and with thin (less than 3 µm) outer muscle layer (Fig. 2C). A solid prostate gland almost as large as atrium, connected with that at 1/3 of ental portion through short stalk (Figs 1D, 2B). Ejaculatory duct long (420µm long), not winding and non-glandular, almost uniform in width (14–19 µm) throughout course with lumen about 10 µm in diameter. Large penis set in deep and narrow penial pouch opening ventrally in XI (Fig. 2F). Penis conical, 110–120 µm long, 50–105 µm wide at base, with thin (1.6–3 µm) inner epithelium and with thick (10–12 µm) subepithelial layer of connective tissue staining well with eosin (Fig. 2D, E). Cuticle layer on penis a little thicker than integumentary cuticle but not forming any distinct penial sheath. None of 19 specimens examined with male ducts had completely or partially developed, nor vestigial spermathecae. Distribution and habitat. The present species was collected from muddy bottom in Lake Tundai, an oxbow lake in Kahayan River system in Central Kalimantan. The lake water is acidic and brownish in color due to high amount of humic substances derived from a tropical bog, with the pH ranging from 3.9 to 4.6 (Ohtaka et al. 2014). The lake is 3–6 m deep, the bottom temperature ranged from 27 to 29°C and the concentration of dissolved oxygen in the bottom waters ranged from 0.7 to 1.1 mgl −1 (Ohtaka et al. 2014). Chiromonid larvae were predominant in the zoobenthos of Lake Tundai, followed by oligochaetes (Iwakuma et al. 2008). Aulophorus, Dero, Branchiura, Limnodrilus, and two more, uncertain oligochaete taxa were recorded from the lake bottom (Iwakuma et al. 2008)., Published as part of Ohtaka, Akifumi & Wulandari, Linda, 2016, Description of Kahayandrilus tundaiensis gen. et sp. nov. (Annelida: Clitellata: Tubificinae) from Central Kalimantan, Indonesia, pp. 43-47 in Species Diversity 21 (1) on pages 45-46, DOI: 10.12782/sd.21.1.043, http://zenodo.org/record/4583608, {"references":["Ohtaka, A., Uenishi, M., Wulandari, L., Liwat, Y., Ardianor, Gumiri, S., Nagasaka, M., and Fukuhara, H. 2014. Structure and abundance of \" Interrhizon \" invertebrates in an oxbow lake in the peat swamp area of Central Kalimantan, Indonesia. Limnology 15: 191 - 197.","Iwakuma, T., Yulintine, and Gumiri, S. 2008. The importance of zoobenthos in the ecosystems of tropical oxbow lakes. Verhandlungen der Internationalen Vereinigung fur Limnologie 30: 35 - 41."]}

Ohtaka, Akifumi, Wulandari, Linda (2016): Description of Kahayandrilus tundaiensis gen. et sp. nov. (Annelida: Clitellata: Tubificinae) from Central Kalimantan, Indonesia. Species Diversity 21 (1): 43-47, DOI: 10.12782/sd.21.1.043, URL: http://dx.doi.org/10.12782/sd.21.1.043

尾瀬ヶ原のアカシボ雪中に貧毛類が豊富に出現する理由を探るために, 貧毛類の生物学的特性を湿原や雪の環境特性と対比させて議論した. 無雪期の尾瀬ヶ原湿原で見られる貧毛類群集は, ヒメミミズ科やミズミミズ科を主体とした比較的少数の種類からなり, 半水生種や無性繁殖が可能な種類が多くを占める. 貧毛類は本来, 低温環境を好む傾向があり, 尾瀬ヶ原湿原に生息している貧毛類の多くは, 本来の生理生態学的性質でアカシボ雪の環境に対応できているものと考えられる. アカシボの後半に, 小型で細長い間隙性の貧毛類が水分含量の高い雪下部で豊富に出現したのは, この時期の雪が, 海浜や河川で見られる砂礫間隙に匹敵する環境になったためと解釈される., To elucidate the reason for abundant occurrence of oligochaetes (Annelida, Citellata) in the red snow“Akashibo”at Ozegahara mire, central Japan, ecological and reproductive features of oligochaetes are briefly reviewed, and the faunal characteristics in oligochaetes in Sphagnum mires and snows were discussed from the viewpoints of habitat preference of oligochaetes. Along with Sphagnum mire itself, the snow on the mire is a kind of ecotone in which content of liquid water varies drastically and enable to harbor both terrestrial and aquatic forms. The Akashibo snow found in the snowmelt season consisted of granular ice particles and saturated water, providing interstitial habitats for small aquatic animals. The water bearing Akashibo snows harbored many enchytraeid and naidid oligochaetes which are primarily aquatic and small enough to move in the wet snow.

赤雪発生の調査を東北地方の47地点について行った. 原因の多くは尾瀬において見られるアカシボ現象と同様に, 多量の酸化鉄を含む粒子であった. 発生地域は融雪時期に積雪下層部と湿原もしくは土壌との境界面に融雪水の流れのある地点あるいは融雪水のとどまる地点であった. 赤雪消滅後の土壌には多量のSiと次いでFeおよび少量のAl, Mgなどが存在した., Vertical distribution and activities of intranivean invertebrates were studied in snowmelt season in northern Japan. The intranivean invertebrates were dominated by copepods, dipteran larvae and oligochaetes,and they increased toward the bottom. High structural similarity between snow and soil animals strongly suggested that the intranivean invertebrates were derived from subnivean fauna. All the harpacticoids recovered from the less wet snow in the middle layers were died often with seriously damaged in their appendages. On the other hand, most of those in the lower and waterbearing layers of the snow showed active movement. Many precopulating pairs were found in the harpacticoids there. It is suggested that inundated granular snow in the late snowmelt season can provide interstices which harbor many small aquatic animals such as copepods and oligochaetes.

尾瀬ヶ原のアカシボ地帯には,アカシボの発達段階に応じて, 雪上, 雪中に多様な無脊椎動物が出現する. 大型の分類群では, Oligochaeta（貧毛類）, Tipulidae（ガガンボ類）, Chironomidae（ユスリカ類）, Ceratopogonidae（ヌカカ類）などが出現し, 小型ではNematoda（線虫類）, Cyclopoida（ケンミジンコ類）, Harpacticoida（ソコミジンコ類）, Turbellaria（ウズムシ類）, Tardigrada（クマムシ類）などであった. 大型のガガンボ類幼虫, ユスリカ類幼虫, 貧毛類は雪中の比較的上部に分布するのに対し, 小型の線虫類, ケンミジンコ類は下部に分布した. 運動性の高いソコミジンコ類は雪の上部まで分布した. これらのアカシボ動物相は, 融雪期の雪―泥界面の湛水状態と貧酸素状態の発達により湿地性の土壌動物が雪中を移動して形成されていると推定される. アカシボ動物を起点とする食物連鎖を雪生態学の観点から論じた., Various invertebrates including nematodes, oligochaetes, harpacticoids, tardigrades, cladocerans, acarina, larvae of tipulids, ceratopogonids and chironomids,appeared as internivean and supranivean fauna in Akashibo snow, a kind of red snow in the Ozegahara Mire. In these animals, larger ones such as tipulids,chironomids and oligochaetes were distributed in comparatively upper part of snow, whereas smaller tardigrades,cyclopoids and nematodes in lower part. These invertebrates were seemed to migrate up from peat surface into snow due to inundation and decrease in oxygen concentration at subnivean environments during the development of Akashibo. Food web on Akashibo snow is discussed from the point of snow ecology.