Metaphire planatoides Nguyen & Nguyen & Lam & Nguyen 2020, new species

Metaphire planatoides, new species (Figs. 1, 4) Material examined. Holotype: 1 mature (CTU-EW.171. h01), natural forests (10°24′21.7″N, 107°16′18.2″E), Long Hai town, Long Dien District, Ba Ria-Vung Tau Province, 33 m asl, 25 October 2016, coll. Nguyen Phuc Hau. Paratypes: 2 matures (CTU-EW.171.p02), same data as holotype. Diagnosis. Small-sized worm, length 64–67 mm, average diameter 2.4–2.8 mm. Body colourless, pale, except light brown clitellum. Prostomium epilobous. First dorsal pore in 11/12. Two pairs of spermathecal pores in ventral intersegments 6/7/8. Male pores located deeply inside copulatory pouches in the setal ring xviii. Genital markings totally absent. Holandric. Intestinal caeca simple. Septa 8/9/10 absent. Description. Body cylindrical, small size, length 64–67 mm, average diameter 2.4–2.8 mm, weight 0.18–0.32 g, segments 89–96. Body colourless, pale except light brown clitellum. Prostomium 1/2 epilobous. First dorsal pore in 11/12. Preclitellar setae stouter and sparser than post-clitellar ones; setal number 39–41 in viii, 51–55 in xxx, 7–9 between two openings of copulatory pouches in xviii; setal distance aa=ab, zz=zy. Clitellum close, xiv–xvi, with only ventral setae, without dorsal pores. Female pore single, in midventral xiv. Two pairs of spermathecal pores in ventral intersegments 6/7/8. No genital markings in spermathecal region. Male pores located deeply inside copulatory pouches in the setal ring xviii. Ventral distance between two openings of copulatory pouches ca. 0.35× body circumference. No genital markings in male region. Septa 5/6/7/8 thick, 8/9/10 absent, 10/11/12/13 thin. Oesophageal gizzard within viii–ix. Intestinal origin at xv; caeca simple, paired in xxvii–xxv. Last hearts in xiii. Pharyngeal micronephridia developed in 5/6/7. Typhlosole simple, lamelliform. Lymph glands absent. Two pairs of spermathecae in vii and viii. Ampulla mangoshaped; duct small, about ⅓ ampulla length. Diverticula long, but waved and folded, directly attached to the base of ampulla duct; seminal chamber tiny, oval-shaped. Spermathecal ducts without nephridia. Accessory glands absent. Holandric. Testis sacs developed in x–xi, connected. Seminal vesicles developed in xi–xii. Ovaries developed in 12/13. Ovisacs invisible. Prostate glands deeply lobuled, paired in xvii–xx; ducts short, C-shaped. No accessory glands. Etymology. The epithet " planatoides " is used to emphasise its similarity to Metaphire planata (Gates, 1926). Remarks. Metaphire planatoides, new species, is assigned to the Metaphire planata group characterised by having two pairs of spermathecal pores in 6/7/8 and simple intestinal caeca (Sims & Easton, 1972). The planata group currently consists of at least six species, M. planata (Gates, 1926), M. decipiens (Beddard, 1912), M. dunckeri (Michaelsen, 1902), M. ferdinandi (Michaelsen, 1891), M. parvula (Ohfuchi, 1956), and M. sintangi (Michaelsen, 1922). The new species differs from these species except M. planata in the absence of genital markings in both spermathecal and male regions. Metaphire planatoides, new species, is somewhat similar to M. planata, in having the first dorsal pore in 11/12, the absence of genital markings in both spermathecal and male regions, and the shape of the openings of copulatory pouches. However, it is distinguished by the absence of accessory glands in the spermathecal region, spermathecae with thin ducts, strongly waved diverticula, connected seminal vesicles, and its smaller size (length = 67 mm, diameter = 2.4–2.8 mm). On the contrary, M. planata has several accessory glands with long ducts, spermathecae with stout ducts, diverticulum straightly cylindrical, somewhat slightly expanded distally, separated seminal vesicles, and a larger size (length = 125 mm, diameter = 4.8 mm).
Published as part of Nguyen, Tung T., Nguyen, Nam Q., Lam, Dang H. & Nguyen, Anh D., 2020, Six new species of the genus Metaphire Sims & Easton, 1972 (Annelida: Oligochaeta: Megascolecidae) from southeastern Vietnam, pp. 220-236 in Raffles Bulletin of Zoology 68 on page 228, DOI: 10.26107/RBZ-2020-0019, http://zenodo.org/record/4577217
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