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The seafloor covers some 70% of the Earth’s surface and has been recognised as a major sink for marine litter. Still, litter on the seafloor is the least investigated fraction of marine litter, which is not surprising as most of it lies in the deep sea, i.e. the least explored ecosystem. Although marine litter is considered a major threat for the oceans, monitoring frameworks are still being set up. This paper reviews current knowledge and methods, identifies existing needs, and points to future developments that are required to address the estimation of seafloor macrolitter. It provides background knowledge and conveys the views and thoughts of scientific experts on seafloor marine litter offering a review of monitoring and ocean modelling techniques. Knowledge gaps that need to be tackled, data needs for modelling, and data comparability and harmonisation are also discussed. In addition, it shows how research on seafloor macrolitter can inform international protection and conservation frameworks to prioritise efforts and measures against marine litter and its deleterious impacts.

Tritonia nigritigris sp. nov. (Figs. 2A, 3A, 4–5) Type material. Holotype: Guide Seamount, Pacific Ocean (37.036532, -123.330875), 1733.4 m depth, ROV Doc Ricketts (dive 882), 15 Aug 2016, 82 mm preserved length, dissected (LACM 3553), GenBank accession numbers: MH 756138 (COI), MH 756133 (16S). Description. Body elongate, narrow (Fig. 2A). Notum outline with four invaginations, completely surrounded by numerous, densely packed glandular projections (Fig. 2A), giving the animal a ruffled appearance. Dorsum covered with numerous, densely packed elongate tubercles or projections, oriented in different directions, forming a zigzagging pattern in some areas. Velum wide, forming two triangular lateral projections, with several frontal irregular indentations. Rhinophores short and wide, with 9 simple lamellae, located on anterior end of notum. Rhinophoral sheaths elongate, with 12 branched papillae around distal edges. Foot smooth, rounded posteriorly, visible dorsally at posterior end and in notum invaginations. Genital and anal openings on right side of body. Background color of notum black. Dorsal tubercles primarily white to greyish-brown near posterior notum, giving the body a light appearance, becoming darker towards head, turning completely black on anterior notum; this gives a black and white appearance with a greyish transitional area mid-length, forming a wedge of black pigment. Notum edge primarily white, except for anterior-most end that becomes dark grey. Velum completely black. Rhinophoral sheaths black with grey edges. Rhinophores with black stalks and beige sheath papillae and clubs. Foot dark grey, surrounded by a thin white line. Digestive system with large, muscular buccal bulb (Fig. 4A). Esophagus wide, connecting anteriorly into buccal bulb, where two large, flat salivary glands connect. Intestine emerging dorsally from left side of digestive gland, forming a loop towards the right side of body where it opens into the anus (Fig. 3A). Radular formula 44 × 50.1. 50 in holotype. Rachidian teeth narrow, with a large, sharp central cusp about twice as large as tooth bases and 3 irregular denticles on each side of central cusp (Fig. 5A). Lateral teeth hook-shaped, with sharp, elongate cusps lacking denticles (Fig. 5B). Outer lateral teeth very elongate with reduced bases (Fig. 5C). Jaws elongate, with no differentiate masticatory border (Fig. 5D). Reproductive system with large, highly convoluted ampulla forming several loops (Fig. 4B), opening on female gland complex where the prostate connects. Prostate narrow, elongate, forming a single loop and expanding into a wide and muscular deferent duct, which connects with a simple, conical penis. Vagina elongate, narrow, expanding abruptly in its distal 1/4 th and opening into the spherical bursa copulatrix. The seminal receptacle is a small spherical evagination located close to mid-length in the vagina. Biology. This species was collected at 1733.4 m depth on the Guide Seamount, about 55 nautical miles off Davenport, California (Fig. 1). The specimen was collected on a steep section of volcanoclastic rock. Dense populations of Keratoisis sp. (isidid octocoral) were observed in close proximity. Other organisms included comatulid and hyocrinid crinoids, primnoid octocorals, Evoloplosoma cf. claguei (sea star), additional unidentified sea stars, Acesta sp. (bivalve), Farrea sp. (hexactinellid sponge), and large and abundant Macrouridae (rattail fishes). Phylogenetic position. Based on available sequence data and the phylogenetic analyses conducted, Tritonia nigritigris sp. nov. is sister to the Antarctic species Tritoniella belli Eliot, 1907 (Fig. 6). Etymology. The species name is derived from the unique coloration of the holotype, in particular the broken, black stripes, which are reminiscent of those of a tiger. Remarks. The most common species in relatively deep-waters of the eastern Pacific is Tritonia tetraquetra (Pallas, 1788), previously recognized as T. diomedea Bergh, 1894. Martynov (2006) considered that Pallas (1788) original description of Limax tetraquetra from the Kuril Islands corresponded to a specimen of the species commonly identified as T. diomedea (see Behrens & Hermosillo 2005) and therefore proposed to use the name T. tetraquetra for this species. Here we cautiously follow Martynov’s (2006) opinion, but clarification of the taxonomic status of this species requires comprehensive examination of specimens across its broad range (from the Kuril Islands to Panama), because as in other nominal species with similar ranges, multiple cryptic species may be involved. Tritonia nigritigris sp. nov. is externally different from other species of Tritonia described to date. The most similar species morphologically is the deep-water species T. newfoundlandica Valdés et al., 2016, described from the North Atlantic (Valdés et al. 2016). Both T. nigritigris sp. nov. and T. newfoundlandica have narrow, elongate bodies with the anterior end wider, tapering posteriorly into a pointy, triangular end. However, whereas T. newfoundlandica is uniformly black, with the rhinophores, rhinophoral sheaths, velar appendages, and secondary gills brownish-red and the dorsum is smooth, lacking tubercles. On the contrary T. nigritigris sp. nov. has a more complex coloration of black, white and grey, and the dorsum is tuberculate. The only two other deep-water species of Tritonia (found below 500 m depth) known to date are T. ingolfiana Bergh, 1899 described by Bergh (1899) from the mid-Atlantic ridge based on a single specimen collected at 887 m depth, and T. episcopalis Bouchet, 1977 described from 1035–2170 m depth also in the Atlantic. Bergh (1899) described his preserved specimen T. ingolfiana as grayish blue with yellow rhinophores. This is different from T. nigritigris sp. nov., which has a black to white body and the rhinophores, gills and velum are much lighter even in the preserved specimens. Other differences include the shape of the penis, which is very elongate and tightly packed in the penial sheath of T. ingolfiana (Bergh 1899: pl. 3 fig. 9), whereas the penis of T. nigritigris n. sp. is much shorter and straight. Tritonia episcopalis as well as T. newfoundlandica have a characteristic scoop in the penis, which is absent in T. nigritigris n. sp. The external coloration of T. episcopalis is bright violet with the gills of the same color and the rhinophores red, whereas in T. nigritigris n. sp. the body is black to white. The sister species of Tritonia nigritigris n. sp., Tritoniella belli, is very distinct externally. Tritoniella belli ranges in color from uniform milky-white or translucent to yellow or orange in specimens (Wägele 1989b). As in T. nigritigris n. sp. the mantle edge is wavy and can be smooth or have finger-like processes. However, specimens of T. belli have a smooth dorsum typically with a longitudinal median ridge, whereas T. nigritigris n. sp. has a tuberculate dorsum and no ridge. In the phylogenetic analyses presented here, both T. nigritigris n. sp. and T. belli form a monophyletic group sister to Tritonia, supporting the separation of Tritoniella from Tritonia. Under this scenario, T. nigritigris n. sp. should be considered a member of Tritoniella. However, the phylogeny of Tritonia is poorly understood and several critical species have not yet been sequenced. Also, morphologically, T. nigritigris n. sp. appears more similar to some species of Tritonia than to T. belli making difficult to find morphological synapomorphies for Tritoniella. Until all these issues are resolved, we prefer to maintain T. nigritigris n. sp. in Tritonia., Published as part of Valdés, Ángel, Lundsten, Lonny & Wilson, Nerida G., 2018, Five new deep-sea species of nudibranchs (Gastropoda: Heterobranchia: Cladobranchia) from the Northeast Pacific, pp. 401-433 in Zootaxa 4526 (4) on pages 404-408, DOI: 10.11646/zootaxa.4526.4.1, http://zenodo.org/record/2611755, {"references":["Pallas, P. S. (1788) Marina varia nova et rariora. Nova Acta Academiae Scientiarum Imperialis Petropolitanea, 2, 229 - 249.","Bergh, R. (1894) Die Opisthobranchien. Reports on the dredging operations off the west coast of Central America to the Galapagos, to the west coast of Mexico, and in the Gulf of California, in charge of Alexander Agassiz, carried on by the U. S. Fish Commission steamer \" Albatross \", during 1891, Lieut. Commander Z. L. Tanner, U. S. N., commanding. Bulletin of the Museum of Comparative Zoology, 25, 125 - 233.","Martynov, A. V. (2006) Nudipleura. In: Kantor, Yu. I. & Sysoev, A. V. (Eds.), Marine and brackish water Gastropoda of Russia and adjacent countries: An illustrated catalogue. KMK Scientific Press, Moscow, pp. 267 - 294, pls. 131 - 138.","Behrens, D. W. & Hermosillo, A. (2005) Eastern Pacific nudibranchs. A guide to the Opisthobranchs from Alaska to Central America. Sea Challengers, Monterey, California, 137 pp.","Valdes, A., Murillo, F. J., McCarthy, J. B. & Yedinak, N. (2016) New deep-water records and species of North Atlantic nudibranchs (Mollusca, Gastropoda: Heterobranchia) with the description of a new species. Journal of the Marine Biological Association of the United Kingdom, 97, 303 - 319. https: // doi. org / 10.1017 / S 0025315416000394","Bergh, R. (1899) Nudibranchiate Gasteropoda. In: The Danish Ingolf-Expedition. Bianco Luno, Copenhagen, 2 (3), 1 - 46.","Bouchet, P. (1977) Opisthobranches de profondeur de l'Ocean Atlantique: II-Notaspidea et Nudibranchiata. Journal of Molluscan Studies, 43, 28 - 66.","Wagele, H. (1989 b) On the anatomy and zoogeography of Tritoniella belli Eliot, 1907 (Opisthobranchia, Nudibranchia) and the synonymy of T. sinuata Eliot, 1907. Polar Biology, 9, 235 - 243. https: // doi. org / 10.1007 / BF 00263771"]}

Ziminella vrijenhoeki sp. nov. (Figs. 2 D–E, 11–13) Type material. Holotype: Blue whale skeleton (implanted on 5 Oct 2004), Monterey Bay, California (36.772, - 122.083), 1018 m depth, ROV Tiburon (dive 1072), 13 Jan 2007, 20 mm preserved length (SIO-BIC M12137), GenBank accession numbers: MH 756136 (COI), MH 756130 (16S), MH 756141 (H3). Paratype: Whale skeleton (unknown species, likely naturally occurring), Monterey Bay, California, (36.7721, - 122.0831), 595 m depth, ROV Doc Ricketts (dive 94), 16 Nov 2009, 24 mm preserved length, dissected (SIO-BIC M12135), GenBank accession numbers: MH 756135 (COI), MH 756129 (16S), MH 756140 (H3). Description. Body elongate, narrow (Figs. 2D), with numerous elongate, thin, dorso-lateral cerata. Cerata arranged in densely packed rows, running from behind oral tentacles to posterior end of body (Figs. 2D, 11 C–D). Cerata increase in size in each row, lateral cerata typically shorter, dorsal cerata longer. Oral tentacles short and wide (Figs. 11 A–D, 11E), nearly conical in live animal (Fig. 2D). Foot corners tentacular, short, wide, almost spherical (Figs. 11C, 11D). Rhinophores elongate, smooth (Figs. 2D, 11B, 11E). Reproductive opening on right anterior portion of the body (Fig. 11 C–D), penis smooth and elongate (Fig. 11D). Anal opening dorso-lateral, posterior to pericardium (Fig. 11 C–D). Body color cream to reddish-orange, semi translucent, with viscera visible through skin as a yellowish mass (Fig. 2 D–E). Oral tentacles the same color as body, rhinophores redder and darker. Cerata translucent pale orange, with red digestive branches and white cnidosacs. Digestive system with large, muscular buccal bulb (Fig. 12A). Esophagus narrow, short, connecting anteriorly into buccal bulb. Digestive gland with lateral branches entering cerata. Intestine emerging laterally from right side of digestive gland, forming a loop and opening into anus on right side of body. Radular formula 27 × 1.1. 1 in paratype (SIO-BIC M12135). Rachidian radular teeth narrow (Fig. 13C), with arch-shaped base and a single central, blunt cusp. Each tooth with 6–8 blunt denticles on each side of cusp (Fig. 13D). Lateral teeth triangular, elongate, with numerous minute denticles on inner side. Jaws elongate (Fig. 13A), no denticles on masticatory border (13B). Reproductive system with very elongate, convoluted ampulla forming numerous loops (Fig. 12B), opening into female gland complex next to prostate opening. Prostate tubular, very elongate, forming numerous loops, opening into elongate, muscular deferent duct. Penis simple, elongate. No vagina nor bursa copulatrix were observed, probably an artifact of the dissection. Biology. This species was collected at two different whale-falls in Monterey Canyon at depths of 1018 m (holotype) and 595 m (paratype) in Monterey Bay, California (Fig. 1). The holotype was collected from a vertebra of an implanted Blue Whale carcass that was being surveyed as part of a time-series analysis of whale-fall ecology (Lundsten et al. 2010b). The whale skeleton where the holotype was collected was in the sulphophilic stage of degradation with dense colonies of Osedax sp. (siboglinid polychaete), additional unidentified polychate worms, Tritonia tetraquetra (nudibranch), Neptunea -Buccinum complex (gastropods), Chionoecetes tanneri (crabs), the fishes Sebastolobus sp. and Lycodapus sp. and Vesicomyidae (chemosynthetic bivalves). The paratype was collected from the sediment surface in the vicinity of a presumed natural whale carcass perched upon the edge of the Monterey Canyon, with some bones of the carcass spread down a steep cliff. Two specimens were observed and recorded onto video tape during this dive (Doc Ricketts dive 94), however, only one specimen was collected. Both specimens were observed upon the sediment. A subtle color variation was noticed between the D94 observations, with the first being a darker, bluer color (Fig. 2E) and the second, which was collected, being more of a reddish orange (Fig. 2D). This whale was presumed to be in the early-stages of decomposition with few sulphophilic organisms or Osedax sp. (siboglinid polychaete) worms observed, although flesh was completely removed. Other organisms observed nearby included the fishes Merluccius productus and Sebastolobus sp., the echinoderms Asteronyx sp., Rathbunaster californicus, Pterasteridae, Poraniopsis inflata and the polychaetes Sabellidae and Serpulidae, as well as Eualus macrophthalmus (caridean shrimp), and Caprellidae (amphipods). Phylogenetic position. Based on the phylogenetic analyses here conducted (Fig. 14), Ziminella vrijenhoeki sp. nov. is nested in a polytomy containing Ziminella abyssa Korshunova et al., 2017 and a clade including Ziminella salmonacea (Couthouy, 1838) and Ziminella circapolaris Korshunova et al., 2017. Etymology. The species is named in honor of Robert C. Vrijenhoek, MBARI Senior/Adjunct Evolutionary Biologist. Bob was the Chief Scientist of MBARI’s whale-fall time series surveys, during which these specimens were collected. Remarks. Korshunova et al. (2017) placed Flabellina salmonacea (Couthouy, 1838) and the new species Ziminella abyssa Korshunova et al., 2017 and Ziminella circapolaris Korshunova et al., 2017 in the new genus Ziminella Korshunova et al., 2017. Ziminella constitutes a well-supported clade, and in the analyses conducted by Korshunova et al. (2017) it is nested in a larger, equally well-supported clade. This larger clade, which contains other species previously assigned to Flabellinidae, including the type species of Flabellina, F. affinis (Gmelin, 1791), was not recovered in the analyses here conducted. The decision of Korshunova et al. (2017) to split Flabellina into a number of new genera dramatically increases the taxonomic complexity of the group, makes the placement of species not studied genetically more difficult, and created taxa supported by few synapomorphies. Additionally, several of those clades were not recovered in our analyses, indicating that further work is needed to produce a reliable phylogeny and classification for aeolid nudibranchs. However, based on the results of the analyses here conducted, which clearly show the close relationship between Ziminella vrijenhoeki sp. nov. and other species assigned to Ziminella by Korshunova et al. (2017), we provisionally place this new species in the genus Ziminella, until more reliable phylogenies become available. Based on Korshunova et al. (2017) and the results of the analyses presented here, the closest species to Ziminella vrijenhoeki sp. nov. are Z. salmonacea, originally described from Charles River, Massachusetts (Couthouy, 1838) and subsequently reported from different localities in the North Atlantic (Kuzirian 1979), Z. abyssa, originally described from deep water (2676 m depth) in the Sea of Japan (Korshunova et al., 2017), and Z. circapolaris, originally described from Franz Josef Land, Arctic Ocean (Korshunova et al., 2017). Ziminella salmonacea has also been reported from the North Pacific (Wakeling 2002), but Martynov (2013) proposed the Pacific Ocean animals belong to Flabellina japonica (Volodchenko 1941). According to Korshunova et al. (2017) species of Ziminella are distinguished by their penial morphology, Z. salmonacea possesses a slightly folded penis, whereas Z. abyssa and Z. japonica have conical penises; but no data is provided for Z. circapolaris. The penis of Z. vrijenhoeki is folded and therefore more similar to that of Z. salmonacea. Ziminella vrijenhoeki sp. nov. and Z. salmonacea are genetically and morphologically distinct, the radula of Z. salmonacea as described by Kuzirian (1979) has a much more elongate rachidian tooth, with smaller denticles. Although we had no access to sequence data of F. japonica for comparison, this species is clearly different from Z. vrijenhoeki sp. nov. The body of F. japonica is cream to pinkish externally and the digestive branches in the cerata are cream (Behrens & Hermosillo 2005) whereas Z. vrijenhoeki sp. nov. is reddish-orange, and the cerata are translucent pale orange, with red digestive branches and white cnidosacs. The single specimen of Ziminella circapolaris Korshunova et al., 2017 included in the analyses here presented is nested within Z. salmonacea raising doubts on the validity of the former species., Published as part of Valdés, Ángel, Lundsten, Lonny & Wilson, Nerida G., 2018, Five new deep-sea species of nudibranchs (Gastropoda: Heterobranchia: Cladobranchia) from the Northeast Pacific, pp. 401-433 in Zootaxa 4526 (4) on pages 415-420, DOI: 10.11646/zootaxa.4526.4.1, http://zenodo.org/record/2611755, {"references":["Lundsten, L., Schlining, K. L., Frasier, K., Johnson, S. B., Kuhnz, L. A., Harvey, J. B. J., Clague, G. & Vrijenhoek, R. C. (2010) Time-series analysis of six whale fall communities in Monterey Bay, California, USA. Deep Sea Research Part I: Oceanographic Research Papers, 57, 1573 - 1584. https: // doi. org / 10.1016 / j. dsr. 2010.09.003","Couthouy J. P. (1838) Descriptions of new species of Mollusca and shells, with remarks on several polypi found in Massachusetts Bay. Boston Journal of Natural History, 2, 68 - 69.","Kuzirian, A. M. (1979) Taxonomy and biology of four New England coryphellid nudibranchs (Gastropoda: Opisthobranchia). Journal of Molluscan Studies, 45, 239 - 261.","Wakeling, M. (2002) Flabellina salmonacea from British Columbia. Sea Slug Forum, Australian Museum, Sydney. Available from: http: // www. seaslugforum. net / find / 6488 (accessed 15 March 2018)","Martynov, A. V. (2013) Morphology, taxonomic status and distribution of the opisthobranch mollusc Coryphella (s. l.) japonica from the central deep water basin of the Sea of Japan. Deep Sea Research Part II: Topical Studies in Oceanography, 86, 111 - 118. https: // doi. org / 10.1016 / j. dsr 2.2012.08.012","Behrens, D. W. & Hermosillo, A. (2005) Eastern Pacific nudibranchs. A guide to the Opisthobranchs from Alaska to Central America. Sea Challengers, Monterey, California, 137 pp."]}

Tritonia sp. (Figs. 2B, 3 C–D, 7–8) Material examined. Hydrate Ridge, Oregon, Northeast Pacific Ocean (44.67° N, 125.098° W), 587 m depth, ROV Jason II (dive 593), 6 Sep 2011, 1 specimen 17 mm preserved length (SIO-BIC M12395), GenBank accession numbers: MH 756139 (COI), MH 756134 (16S), MH 756145 (H3). Description. Body elongate, narrow, tapering towards the posterior end (Fig. 2B). Lateral margins with 8 branched appendages (cerata), tripinnate, decreasing in size towards the posterior end (Fig. 2A). Dorsum smooth, lacking tubercles or projections. Velum wide, triangular, with 14 conical, simple projections. Rhinophores elongate, narrow, each with a smooth, long stalk. Rhinophoral clubs with 5 tripinnate papillae, forming a circle closed posteriorly by a much more elongate papilla, covered with lamellae on its posterior end (Fig. 3C), located on anterior end of notum. Rhinophoral sheaths low, with smooth edges. Foot smooth, elongate posteriorly, visible dorsally at posterior end and in notum invaginations. Anal opening on right side of body (Fig. 3D). Background color translucent white, with a concentration of orange pigment on the central dorsum. Body contractions concentrate the pigment, forming an irregular network of red lines. Notum edge translucent white with the lateral appendages (cerata) opaque white to cream. Velum and velar appendages translucent white. Rhinophores with translucent white stalks and beige sheath clubs. Foot uniform translucent white. Digestive system with large, muscular buccal bulb (Fig. 7). Esophagus narrow, connecting anteriorly into buccal bulb, where two large, flat salivary glands connect. Intestine emerging dorsally from the stomach, forming a loop towards the right side of body where it opens into the anus (Fig. 3D). Radular formula 44 × 49.1. 49 in the single specimen examined. Rachidian teeth broad, with a short, wide central cusp, shorter than tooth, and 1–2 denticles or folds on each side of central cusp (Fig. 8A). Lateral teeth hook-shaped, with sharp, elongate cusps lacking denticles (Fig. 8B). Outer lateral teeth very elongate with reduced bases (Fig. 8C). Jaws elongate (Fig. 8D), with a differentiated masticatory border (Fig. 8E). Reproductive system absent, specimen was probably castrated as suggested by damage on the right side of the body visible in the live (Fig. 2B) and preserved (Fig. 3D) specimen. Biology. This species was collected at 587 m, from Hydrate Ridge, an area of methane seeps about 44 nautical miles off Newport, Oregon (Fig. 1). It came from an inactive, experimental rock (Levin Lab E12, rock F), upon which an unidentified soft coral (SIO-BIC Co2330) was growing. Other organisms collected from the soft coral were an unidentified amphipod (SIO-BIC C11265) and the polychaete worm Eusyllis nuchalata (SIO-BIC A2679). Phylogenetic position. Tritonia sp. is placed in a clade including Eastern Pacific species of Tritonia such as T. festiva (Stearns, 1873) and Tritonia tetraquetra (Pallas, 1788), as well as two other unidentified specimens (Fig. 6). Remarks. Tritonia sp. appears to be different from other species of Tritonia described to date. However, the single specimen examined lacked a reproductive system. Damage on the right side of the body may suggest the animal was either harmed during collection or castrated by a parasite. The external morphology of Tritonia sp. resembles that of Tritonia myrakeenae Bertsch & Mozqueira Osuna, 1986, also found in the Eastern Pacific, but the latter lacks red pigment on the dorsum and often has two white pigment patches posterior to the head (Bertsch & Mozqueira Osuna, 1986), absent in Tritonia sp. The radula of T. myrakeenae is also different from that of Tritonia sp. The former has a rachidian tooth with an elongate central cusp and two strong lateral denticles (Bertsch & Mozqueira Osuna, 1986), whereas Tritonia sp. has a much broader rachidian with a shorter central cusp. Unfortunately, no molecular data for T. myrakeenae is available for comparison., Published as part of Valdés, Ángel, Lundsten, Lonny & Wilson, Nerida G., 2018, Five new deep-sea species of nudibranchs (Gastropoda: Heterobranchia: Cladobranchia) from the Northeast Pacific, pp. 401-433 in Zootaxa 4526 (4) on page 410, DOI: 10.11646/zootaxa.4526.4.1, http://zenodo.org/record/2611755, {"references":["Pallas, P. S. (1788) Marina varia nova et rariora. Nova Acta Academiae Scientiarum Imperialis Petropolitanea, 2, 229 - 249.","Bertsch, H. & Mozqueira Osuna, A. (1986) A new species of Tritonia (Nudibranchia) from southern California and Baja California. The Nautilus, 100, 46 - 49. https: // doi. org / 10.5962 / bhl. part. 26492"]}

Dendronotus claguei sp. nov. (Figs 2C, 3B, 9–10) Type material. Holotype: Alarcón Rise, Gulf of California, Northeast Pacific Ocean (23.4549, -108.485405), 2369 m depth, ROV Doc Ricketts (dive 394), 24 Apr 2012, 7 mm preserved length (LACM 3554), GenBank accession number: MH 756144 (H3). Paratype: Alarcón Rise, Gulf of California, Northeast Pacific Ocean (23.4549, -108.485405), 2368.8 m depth, ROV Doc Ricketts (dive 394), 24 Apr 2012, 18 mm preserved length, dissected. Description. Body long, narrow, with 4-6 pairs of simple, elongate, dorso-lateral cerata (Fig. 2C). Velum composed of 4 narrow and elongate papillae. Rhinophores with very elongate stalks. Rhinophoral sheaths with 4 elongate, simple papillae on distal edges, the innermost papilla being much larger than the other three. Rhinophoral clubs elongate, with 11 simple lamellae. Color uniformly translucent white with some internal organs visible through the body wall as beige or yellowish areas. Digestive system with large, muscular buccal bulb (Fig. 9A). Esophagus narrow, short, connecting anteriorly into buccal bulb. Intestine emerging dorsally from left side of digestive gland, forming a loop towards the right side of body where it opens into the anus (Fig. 3B). Radular formula 32 × 7–8.1.7– 8 in the paratype. Rachidian teeth triangular, with arch-like basal end and blunt central cusp, with 11–13 sharp denticles on each side (Fig. 10A). Lateral teeth elongate, with up to 10 apical, sharp denticles, the innermost being the longest. Teeth typically decreasing in size and number of denticles towards outer edge of radula. Jaws elongate with a masticatory border bearing rows of low, irregular denticles (Fig. 10B). Reproductive system with large, convoluted ampulla forming three loops (Fig. 9B), merging with distal end of the prostate before connecting to female gland complex. Prostate short, composed of ~9 large follicles, connecting to a tubular, elongate and convoluted muscular deferent duct, which progressively expands distally and connects to a long and narrow penis. Vagina wide, elongate, opening into spherical bursa copulatrix. The seminal receptacle is a small, spherical, opening directly into the vagina close to its proximal end. Biology. This species was collected at 2369 m depth on an inactive hydrothermal chimney of the Alarcón Rise, approximately 53 nautical miles east of Cabo Pulmo, Baja California Sur, Mexico (Fig. 1). Although the inactive chimney itself was mostly devoid of life, other organisms seen in the vicinity of the collection site included Aldrovandia sp. (halosaurid fishes), Biremis sp. (terebellid polychaete), Bonellidae (echiuran), Galatheidae (squat lobster), Liparidae (snail fishes), Synallactidae (holothurian), and dense Xenophyophoroidea (benthic foraminifera). Phylogenetic position. According to the phylogenetic analyses here conducted (Fig. 6), Dendronotus claguei sp. nov. appears to be sister to a clade containing several specimens identified as D. robustus and also including D. patricki. Etymology. The species is named in honor of David A. Clague, MBARI Senior Scientist and Volcanologist. Dave was the Chief Scientist of the expedition to Alarcón Rise, where the specimens were collected. Remarks. Dendronotus claguei sp. nov. is morphologically very different from most other species of Dendronotus. The only exception is the Atlantic deep-sea species D. comteti Valdés & Bouchet, 1998, described from a hydrothermal vent site at 1685 m depth in the mid-Atlantic Ridge, which also has a simple dorso-lateral cerata, with no branching pattern. Additionally, both D. comteti and D. claguei sp. nov. have similarly shaped rachidian teeth, but in D. claguei sp. nov. they are more triangular than in D. comteti. Unfortunately, the reproductive anatomy, external coloration and sequence data of D. comteti remain unknown, therefore it could not be included in the phylogenetic analyses. Dendronotus claguei sp. nov. is the only Eastern Pacific species of Dendronotus with a uniform white background color and simple dorso-lateral cerata. The only other species of Dendronotus reported from deepwaters in the Northeast Pacific is D. patricki Stout, Wilson, and Valdés, 2011, described from 1819 m depth in the Monterey Canyon, California. These two species are easily differentiated by their radular and reproductive anatomy. Although D. claguei sp. nov. has a triangular rachidian tooth with 11–13 sharp, similar sized denticles on each side, running from the tip of the cups to the base, in D. patricki the teeth are elongate with about 20 denticles on each side, and the cusp is clearly differentiated from the rest of the tooth, with very small denticles. Additionally, D. patricki has simple lateral teeth, devoid of denticles, whereas D. claguei sp. nov. has up to 10 apical, sharp denticles on the lateral teeth. The reproductive system of D. patricki has a very elongate prostate and a large bursa copulatrix in relation to the width of the vagina, whereas in D. claguei sp. nov. the prostate is much shorter and the bursa copulatrix is not much wider than the vagina. Externally, D. claguei sp. nov. is characterized by having a uniformly white body with simple lateral appendages, while D. patricki is reddish brown, with ramified dorsal appendages in a fan-shaped branching pattern.

Cuthona methana sp. nov. (Figs. 2 F–G, 15A–D, 16–17) Type material. Holotype: Hydrate Ridge, off Oregon (44.67012, -125.0987), 587–610 m depth, ROV Jason II (dive 593), 4 Sep 2011, 4 mm preserved length (SIO-BIC M12413). Paratype: Hydrate Ridge, off Oregon (44.67012, -125.0987), 587–610 m depth, ROV Jason II (dive 593), 4 Sep 2011, 6 mm preserved length, dissected (SIO-BIC M12412). Description. Body elongate, wide (Figs. 2E), with several elongate, dorso-lateral cerata. Cerata arranged in densely packed rows, running from behind oral tentacles to posterior end of body (Figs. 2E, 15B, 15D). Cerata increase in size in each row, lateral cerata typically shorter, dorsal cerata longer. Oral tentacles elongate and wide (Figs. 15A, 15C). Foot corners tentacular, very small (Figs. 15A, 15C). Rhinophores elongate, smooth (15B, 15D). Reproductive opening on right anterior portion of body (Fig. 15B, 15D). Anal opening lateral, posterior to pericardium (Fig. 15B, 15D). Body color cream-white, semi translucent, with viscera visible through skin as a palepinkish mass (Fig. 2 F–G). Oral tentacles same color as body, with pink-orange bases, rhinophores pink-orange. Cerata translucent white, with cream digestive branches and opaque white cnidosacs. Digestive system with large, muscular buccal bulb (Fig. 16A). Esophagus narrow, short, connecting anteriorly into buccal bulb. Digestive gland with lateral branches entering cerata. Intestine emerging dorsally from left side of digestive gland, forming a loop towards right ventral side of body and running posteriorly to open into anus. Radular formula 25 × 0.1.0 in paratype (SIO-BIC M12412). Radular teeth narrow (Fig. 17A), with arch-shaped base and single central, elongate, sharp cusp. Each tooth with 3 elongate denticles on each side of cusp (Fig. 17B). Jaws elongate (Fig. 17C), masticatory border with a row of denticles bearing a series of tubercles (Fig. 17D). Reproductive system with very short, oval ampulla (Fig. 16B), opening into female gland complex next to prostate opening. Prostate tubular, short, forming two loops, expanding into oval, muscular deferent duct. Penis simple, elongate. No vagina nor bursa copulatrix were observed, probably due to the small size of the specimen dissected. Biology. This species was collected at 587 m depth on Hydrate Ridge, an area of methane seeps about 44 nautical miles off Newport, Oregon (Fig. 1). Both animals were collected off inactive rocks around seep areas. The holotype was collected from E7 sterile rock 8 and the paratype from E7 large rock 20a (Levin lab experiments). Etymology. This species is named for the methane seep environment where it was found. Remarks. Molecular data could not be generated for Cuthona methana, but this species is morphologically different from all other species of Cuthona described from the Eastern Pacific. Cella et al. (2016) proposed a new taxonomy for species previously assigned to Cuthona including the resurrection of Tenellia A. Costa, 1866 and the introduction of several new genera. Although this classification scheme is not as complex as that by Korshunova et al. (2017), it also based on poorly resolved trees and makes the placement of species not studied genetically, such as Cuthona methana sp. nov., more difficult. The phylogenetic relationships of aeolids are in a state of flux due to lack of resolution for lower branches, and only next generation sequencing techniques appear to provide resolution for critical nodes (Goodheart et al. 2017). Because it is virtually impossible for us to determine the phylogenetic position of Cuthona methana sp. nov. in Cuthona, Tenellia, or any of the new genera described by Cella et al. (2016), it is here conservatively regarded as a member of Cuthona. Among the known Eastern Pacific species, Cuthona methana sp. nov. is only externally similar to C. divae (Ev. Marcus, 1961), but lacks the brown to pink pigment digestive branches in the cerata and the rhinophores are pinkish, instead of translucent white (Behrens & Hermosillo 2005). Internally, the radula of C. divae (described by MacFarland, 1966 —under the name Cuthona rosea MacFarland, 1966) has a triangular rachidian tooth with numerous lateral denticles, very different from that of C. methana, which has a much narrower rachidian tooth with only 3 denticles on each side of the cusp., Published as part of Valdés, Ángel, Lundsten, Lonny & Wilson, Nerida G., 2018, Five new deep-sea species of nudibranchs (Gastropoda: Heterobranchia: Cladobranchia) from the Northeast Pacific, pp. 401-433 in Zootaxa 4526 (4) on pages 420-424, DOI: 10.11646/zootaxa.4526.4.1, http://zenodo.org/record/2611755, {"references":["Cella, K., Carmona, L., Ekimova, I., Chichvarkhin, A., Schepetov, D. & Gosliner, T. M. (2016) A Radical Solution: The phylogeny of the nudibranch family Fionidae. PLoS ONE, 11, e 0167800. https: // doi. org / 10.1371 / journal. pone. 0167800","Goodheart, J. A., Bazinet, A. L., Valdes, A., Collins, A. G. & Cummings, M. P. (2017) Prey preference follows phylogeny: evolutionary dietary patterns within the marine gastropod group Cladobranchia (Gastropoda: Heterobranchia: Nudibranchia). BMC Evolutionary Biology, 17, 221. https: // doi. org / 10.1186 / s 12862 - 017 - 1066 - 0","Behrens, D. W. & Hermosillo, A. (2005) Eastern Pacific nudibranchs. A guide to the Opisthobranchs from Alaska to Central America. Sea Challengers, Monterey, California, 137 pp.","MacFarland, F. M. (1966) Studies of opisthobranchiate mollusks of the Pacific coast of North America. Memoirs of the California Academy of Sciences, 6, 1 - 546, pls. 1 - 72."]}

Dendronotus claguei sp. nov. (Figs 2C, 3B, 9���10) Type material. Holotype: Alarc��n Rise, Gulf of California, Northeast Pacific Ocean (23.4549, -108.485405), 2369 m depth, ROV Doc Ricketts (dive 394), 24 Apr 2012, 7 mm preserved length (LACM 3554), GenBank accession number: MH 756144 (H3). Paratype: Alarc��n Rise, Gulf of California, Northeast Pacific Ocean (23.4549, -108.485405), 2368.8 m depth, ROV Doc Ricketts (dive 394), 24 Apr 2012, 18 mm preserved length, dissected. Description. Body long, narrow, with 4-6 pairs of simple, elongate, dorso-lateral cerata (Fig. 2C). Velum composed of 4 narrow and elongate papillae. Rhinophores with very elongate stalks. Rhinophoral sheaths with 4 elongate, simple papillae on distal edges, the innermost papilla being much larger than the other three. Rhinophoral clubs elongate, with 11 simple lamellae. Color uniformly translucent white with some internal organs visible through the body wall as beige or yellowish areas. Digestive system with large, muscular buccal bulb (Fig. 9A). Esophagus narrow, short, connecting anteriorly into buccal bulb. Intestine emerging dorsally from left side of digestive gland, forming a loop towards the right side of body where it opens into the anus (Fig. 3B). Radular formula 32 �� 7���8.1.7��� 8 in the paratype. Rachidian teeth triangular, with arch-like basal end and blunt central cusp, with 11���13 sharp denticles on each side (Fig. 10A). Lateral teeth elongate, with up to 10 apical, sharp denticles, the innermost being the longest. Teeth typically decreasing in size and number of denticles towards outer edge of radula. Jaws elongate with a masticatory border bearing rows of low, irregular denticles (Fig. 10B). Reproductive system with large, convoluted ampulla forming three loops (Fig. 9B), merging with distal end of the prostate before connecting to female gland complex. Prostate short, composed of ~9 large follicles, connecting to a tubular, elongate and convoluted muscular deferent duct, which progressively expands distally and connects to a long and narrow penis. Vagina wide, elongate, opening into spherical bursa copulatrix. The seminal receptacle is a small, spherical, opening directly into the vagina close to its proximal end. Biology. This species was collected at 2369 m depth on an inactive hydrothermal chimney of the Alarc��n Rise, approximately 53 nautical miles east of Cabo Pulmo, Baja California Sur, Mexico (Fig. 1). Although the inactive chimney itself was mostly devoid of life, other organisms seen in the vicinity of the collection site included Aldrovandia sp. (halosaurid fishes), Biremis sp. (terebellid polychaete), Bonellidae (echiuran), Galatheidae (squat lobster), Liparidae (snail fishes), Synallactidae (holothurian), and dense Xenophyophoroidea (benthic foraminifera). Phylogenetic position. According to the phylogenetic analyses here conducted (Fig. 6), Dendronotus claguei sp. nov. appears to be sister to a clade containing several specimens identified as D. robustus and also including D. patricki. Etymology. The species is named in honor of David A. Clague, MBARI Senior Scientist and Volcanologist. Dave was the Chief Scientist of the expedition to Alarc��n Rise, where the specimens were collected. Remarks. Dendronotus claguei sp. nov. is morphologically very different from most other species of Dendronotus. The only exception is the Atlantic deep-sea species D. comteti Vald��s & Bouchet, 1998, described from a hydrothermal vent site at 1685 m depth in the mid-Atlantic Ridge, which also has a simple dorso-lateral cerata, with no branching pattern. Additionally, both D. comteti and D. claguei sp. nov. have similarly shaped rachidian teeth, but in D. claguei sp. nov. they are more triangular than in D. comteti. Unfortunately, the reproductive anatomy, external coloration and sequence data of D. comteti remain unknown, therefore it could not be included in the phylogenetic analyses. Dendronotus claguei sp. nov. is the only Eastern Pacific species of Dendronotus with a uniform white background color and simple dorso-lateral cerata. The only other species of Dendronotus reported from deepwaters in the Northeast Pacific is D. patricki Stout, Wilson, and Vald��s, 2011, described from 1819 m depth in the Monterey Canyon, California. These two species are easily differentiated by their radular and reproductive anatomy. Although D. claguei sp. nov. has a triangular rachidian tooth with 11���13 sharp, similar sized denticles on each side, running from the tip of the cups to the base, in D. patricki the teeth are elongate with about 20 denticles on each side, and the cusp is clearly differentiated from the rest of the tooth, with very small denticles. Additionally, D. patricki has simple lateral teeth, devoid of denticles, whereas D. claguei sp. nov. has up to 10 apical, sharp denticles on the lateral teeth. The reproductive system of D. patricki has a very elongate prostate and a large bursa copulatrix in relation to the width of the vagina, whereas in D. claguei sp. nov. the prostate is much shorter and the bursa copulatrix is not much wider than the vagina. Externally, D. claguei sp. nov. is characterized by having a uniformly white body with simple lateral appendages, while D. patricki is reddish brown, with ramified dorsal appendages in a fan-shaped branching pattern., Published as part of Vald��s, ��ngel, Lundsten, Lonny & Wilson, Nerida G., 2018, Five new deep-sea species of nudibranchs (Gastropoda: Heterobranchia: Cladobranchia) from the Northeast Pacific, pp. 401-433 in Zootaxa 4526 (4) on pages 412-414, DOI: 10.11646/zootaxa.4526.4.1, http://zenodo.org/record/2611755, {"references":["Valdes, A. & Bouchet, P. (1998) Naked in toxic fluids: A nudibranch mollusc from hydrothermal vents. Deep Sea Research Part II: Tropical Studies in Oceanography, 45, 319 - 327. https: // doi. org / 10.1016 / S 0967 - 0645 (97) 00075 - 1","Stout, C. C., Wilson, N. G. & Valdes, A. (2011) A new species of deep-sea Dendronotus Alder & Hancock (Mollusca: Nudibranchia) from California, with an expanded phylogeny of the genus. Invertebrate Systematics, 25, 60 - 69. https: // doi. org / 10.1071 / IS 10027"]}

Aeolidia libitinaria sp. nov. (Figs. 2H, 15 G–H, 18–19) Type material. Holotype: Gray whale skeleton (implanted on 10 Apr 2005), Monterey Bay, California (36.772, - 122.083), 382 m depth, ROV Doc Ricketts (dive 96), 17 Nov 2009, 23 preserved length, dissected (SIO-BIC M12138), GenBank accession numbers: MH 756137 (COI), MH 756132 (16S), MH 756143 (H3). Description. Body elongate, wide, with numerous elongate, dorso-lateral cerata (Fig. 2H). Cerata arranged in densely packed rows, running from behind oral tentacles to posterior end of body (Fig. 2H). Cerata increase in size in each row, lateral cerata typically shorter, dorsal cerata longer (Fig. 2H, 15G). Oral tentacles tentacular, narrow, elongate (Figs. 2H, 15G). Foot corners absent (Figs. 15G). Rhinophores elongate (Figs. 2F), with low irregular swellings (Fig. 15H). Body color brown-ochre, covered with densely arranged yellowish spots (Fig. 2H). Rhinophores and oral tentacles same color as body but two distal thirds yellowish-white. Cerata also with same color as body (Fig. 2H), with digestive gland branches partially visible, particularly in smaller cerata, giving them a reddish tinge; cnidosacs white. Digestive system with very large, muscular buccal bulb (Fig. 18A). Esophagus inflated, large, occupying nearly half of visceral volume, connecting anteriorly into buccal bulb. Digestive gland with lateral branches entering cerata. Intestine emerging dorsally from left side of digestive gland, forming a loop towards right side of body where it runs further posteriorly until it opens into anus on dorso-right side of body (cleioproctic). Intestine with several tubercles near proximal end. Radular formula 19 × 0.1.0 in holotype. Radular teeth broad, arch-shaped (Fig. 19B), with 43–52 elongate acutely pointed denticles, lacking central cusp. Teeth progressively smaller towards the posterior end of radula. Jaws elongate (Fig. 19A), no denticles on masticatory border. Reproductive system with very elongate, convoluted ampulla forming numerous loops (Fig. 18B), opening into female gland complex next to prostate opening. Prostate tubular, very elongate, forming numerous loops, expanding into elongate, muscular deferent duct. Penis simple, elongate. No vagina or seminal receptacle were observed, probably an artifact of the dissection. Biology. This species was collected at 382 m depth on an implanted Gray Whale carcass that was being surveyed as part of a time-series analysis of whale-fall ecology (Lundsten et al. 2010b) in Monterey Bay, CA. The carcass of this whale was in the mid-sulphophilic stage, however, the 382 m site was heavily sedimented and the carcass was exposed to a changing regime of bone movement, burial, and re-exposure. Other organisms seen at this site included dense populations of Osedax sp. (siboglinid polychaete), the anenomes Actiniaria unid., and Metridium farcimen, Chorilia longipes (crabs), the echinoderms Ophiuroidea spp., Rathbunaster californicus, and Strongylocentrotus fragilis and many species of fish including Anoplopomia fimbria, Lycodes cortezianus, Lycodes diapterus, Merluccius productus, and Sebastolobus sp. Phylogenetic position. Aeolidia libitinaria sp. nov. is sister to A. loui and this relationship is well supported (Fig. 14). Etymology. The species name is derived from the Latin word for undertaker, owing to the type specimen being found among the bones of a deceased cetacean. Remarks. Aeolidia libitinaria sp. nov. is distinguishable from other species of Aeolidia by its external coloration, no other species has a brown-ochre, covered with densely arranged yellowish spots. The morphology of the reproductive system of Aeolidia libitinaria sp. nov., with a wide and elongate penial sheath, resembles that of A. papillosa as described by Kienberger et al. (2016), but it is different from all other species of the genus including A. loui, its sister taxon, which has a much shorter, triangular penial sheath. The radular teeth of A. papillosa, A. loui and Aeolidia libitinaria sp. nov. are different. In A. papillosa and A. loui the teeth are wide and delicate, whereas in Aeolidia libitinaria sp. nov. are more robust, generally narrower. Additionally, these three species are genetically distinct as shown in the phylogenetic analysis results (Fig. 14). No seminal receptacle was observed in Aeolidia libitinaria sp. nov. but this could be an artifact of the dissection.

Aeolidia libitinaria sp. nov. (Figs. 2H, 15 G���H, 18���19) Type material. Holotype: Gray whale skeleton (implanted on 10 Apr 2005), Monterey Bay, California (36.772, - 122.083), 382 m depth, ROV Doc Ricketts (dive 96), 17 Nov 2009, 23 preserved length, dissected (SIO-BIC M12138), GenBank accession numbers: MH 756137 (COI), MH 756132 (16S), MH 756143 (H3). Description. Body elongate, wide, with numerous elongate, dorso-lateral cerata (Fig. 2H). Cerata arranged in densely packed rows, running from behind oral tentacles to posterior end of body (Fig. 2H). Cerata increase in size in each row, lateral cerata typically shorter, dorsal cerata longer (Fig. 2H, 15G). Oral tentacles tentacular, narrow, elongate (Figs. 2H, 15G). Foot corners absent (Figs. 15G). Rhinophores elongate (Figs. 2F), with low irregular swellings (Fig. 15H). Body color brown-ochre, covered with densely arranged yellowish spots (Fig. 2H). Rhinophores and oral tentacles same color as body but two distal thirds yellowish-white. Cerata also with same color as body (Fig. 2H), with digestive gland branches partially visible, particularly in smaller cerata, giving them a reddish tinge; cnidosacs white. Digestive system with very large, muscular buccal bulb (Fig. 18A). Esophagus inflated, large, occupying nearly half of visceral volume, connecting anteriorly into buccal bulb. Digestive gland with lateral branches entering cerata. Intestine emerging dorsally from left side of digestive gland, forming a loop towards right side of body where it runs further posteriorly until it opens into anus on dorso-right side of body (cleioproctic). Intestine with several tubercles near proximal end. Radular formula 19 �� 0.1.0 in holotype. Radular teeth broad, arch-shaped (Fig. 19B), with 43���52 elongate acutely pointed denticles, lacking central cusp. Teeth progressively smaller towards the posterior end of radula. Jaws elongate (Fig. 19A), no denticles on masticatory border. Reproductive system with very elongate, convoluted ampulla forming numerous loops (Fig. 18B), opening into female gland complex next to prostate opening. Prostate tubular, very elongate, forming numerous loops, expanding into elongate, muscular deferent duct. Penis simple, elongate. No vagina or seminal receptacle were observed, probably an artifact of the dissection. Biology. This species was collected at 382 m depth on an implanted Gray Whale carcass that was being surveyed as part of a time-series analysis of whale-fall ecology (Lundsten et al. 2010b) in Monterey Bay, CA. The carcass of this whale was in the mid-sulphophilic stage, however, the 382 m site was heavily sedimented and the carcass was exposed to a changing regime of bone movement, burial, and re-exposure. Other organisms seen at this site included dense populations of Osedax sp. (siboglinid polychaete), the anenomes Actiniaria unid., and Metridium farcimen, Chorilia longipes (crabs), the echinoderms Ophiuroidea spp., Rathbunaster californicus, and Strongylocentrotus fragilis and many species of fish including Anoplopomia fimbria, Lycodes cortezianus, Lycodes diapterus, Merluccius productus, and Sebastolobus sp. Phylogenetic position. Aeolidia libitinaria sp. nov. is sister to A. loui and this relationship is well supported (Fig. 14). Etymology. The species name is derived from the Latin word for undertaker, owing to the type specimen being found among the bones of a deceased cetacean. Remarks. Aeolidia libitinaria sp. nov. is distinguishable from other species of Aeolidia by its external coloration, no other species has a brown-ochre, covered with densely arranged yellowish spots. The morphology of the reproductive system of Aeolidia libitinaria sp. nov., with a wide and elongate penial sheath, resembles that of A. papillosa as described by Kienberger et al. (2016), but it is different from all other species of the genus including A. loui, its sister taxon, which has a much shorter, triangular penial sheath. The radular teeth of A. papillosa, A. loui and Aeolidia libitinaria sp. nov. are different. In A. papillosa and A. loui the teeth are wide and delicate, whereas in Aeolidia libitinaria sp. nov. are more robust, generally narrower. Additionally, these three species are genetically distinct as shown in the phylogenetic analysis results (Fig. 14). No seminal receptacle was observed in Aeolidia libitinaria sp. nov. but this could be an artifact of the dissection., Published as part of Vald��s, ��ngel, Lundsten, Lonny & Wilson, Nerida G., 2018, Five new deep-sea species of nudibranchs (Gastropoda: Heterobranchia: Cladobranchia) from the Northeast Pacific, pp. 401-433 in Zootaxa 4526 (4) on pages 424-425, DOI: 10.11646/zootaxa.4526.4.1, http://zenodo.org/record/2611755, {"references":["Lundsten, L., Schlining, K. L., Frasier, K., Johnson, S. B., Kuhnz, L. A., Harvey, J. B. J., Clague, G. & Vrijenhoek, R. C. (2010) Time-series analysis of six whale fall communities in Monterey Bay, California, USA. Deep Sea Research Part I: Oceanographic Research Papers, 57, 1573 - 1584. https: // doi. org / 10.1016 / j. dsr. 2010.09.003","Kienberger, K., Carmona, L., Pola, M., Padula, V., Gosliner, T. M. & Cervera, J. L. (2016) Aeolidia papillosa (Linnaeus, 1761) (Mollusca: Heterobranchia: Nudibranchia), single species or a cryptic species complex? A morphological and molecular study. Zoological Journal of the Linnean Society, 177, 481 - 506. https: // doi. org / 10.1111 / zoj. 12379"]}

Cladorhiza mexicana sp. nov. Figs. 4���5, Table 1 Type material. Holotype: CASIZ Cat. No. 219700, MBARI D741-A1, Alarcon Rise, Gulf of California, Mexico, 23�� 32' 40.7682" N, 108�� 25' 52.7304" W, 2473 m, ROV Doc Ricketts dive 741 from R/ V Western Flyer. Date of collection April 5, 2015. Fixed in 95% ethanol. Type locality. Alarcon Rise, Gulf of California, Mexico. Etymology. The species name, mexicana, alludes to the country where the holotype was discovered. Diagnosis. Crinorhiza form, parasol-shaped sponge, on long stalk and presumed basal holdfast. Three size classes of megasclere styles and three microsclere categories including tridentate unguiferate anisochelae, contort sigmancistras, and asymmetrical pseudoamphiasters. Description. Holotype: Long, parasol-shaped sponge measuring 30 cm in total length with a stalk width of 1 mm. Parasol diameter of 2.6 cm with seventy-six long filaments, 3.3���4.2 cm in length, radiating out in all directions from the parasol edge. Spheroid top-knot on apical surface of parasol measures 9 mm in length and 7.3 mm in diameter with dense, small filaments radiating in all directions in lengths from 4���9 mm. On the stalk 6.9 cm below the parasol is an oocyte swelling, containing numerous visible oocytes, 2.5 cm in length and 3 mm at its widest dimension. Basal holdfast (presumed) broke off during collection. Creamy yellow in preserved state, bright white living specimen. Spicules. Large style 1 length 3845 �� 268 ��m, n=46, width 66.5 �� 7.3 ��m, n=46; large style 2 length 2948 �� 298 ��m, n=39, width 54.2 �� 8.9 ��m, n=40; large style 3 length 1612.3 �� 319 ��m, n=46, width 31.4 �� 7.4 ��m, n=44; tridentate unguiferate anisochelae 34.5 �� 1.5 ��m, n=67; pseudoamphiaster with 5 alae each side, alae slightly longer on one end 108.8 �� 6.4 ��m, n=53; sigmancistra 51.2 �� 3.8 ��m, n=58 and occur only in the apical surfaces and small filaments of the parasol. Habitat and associated fauna. The holotype was collected from a pillow basalt with a thin sediment veneer in a heterogeneous habitat of pillow basalt interspersed with sedimentary deposits. The covering of sediment was thick enough to conceal the mode of basal attachment of the holotype, however, upon retrieval, the base of the specimen broke and we interpret this as evidence of basal holdfast attachment, as has been observed for other hard rock attached species. In addition, when rooted in the sediment with rhizoids, these sponges generally release quite easily and are retrieved intact by ROV manipulator or trawl. Other taxa observed in low abundance in the vicinity of the holotype include Actiniaria, Aldrovandia sp., Bonellidae, Galatheidae, Heteropolypus ritteri, Laetmogonidae, Lycenchelys sp., Megalodicopia hians, Ophidiidae, Peniagone sp., and Xenophyophoroidea. Remarks. Of the 43 previously described species of Cladorhiza, very few have been described that have the parasol morphology of the species described herein. Those Cladorhiza species that are most similar include C. corona Lehnert et al., 2005, C. longipinna Ridley & Dendy, 1886, and C. mirabilis Ridley & Dendy, 1886. Cladorhiza corona is quite distinct and differs from C. mexicana sp. nov. both in having the ���crown��� morphology and in lacking pseudoamphiasters. Cladorhiza longipinna differs morphologically and in its lack of pseudoamphiasters. Cladorhiza mirabilis was described from a specimen collected in the South Pacific and its description differs greatly both in size and spiculation. For example, Cladorhiza mirabilis has a longitudinal length (measured from end to end of parasol edge filament) of 6 mm, whereas this longitudinal length on C. mexicana is ~ 8.8 cm. Similar to C. mexicana sp. nov., C. mirabilis does have pseudoamphiasters but they are of a much larger size (230 ��m in C. mirabilis vs. 109 ��m in C. mexicana sp. nov.). Pseudoamphiasters in C. mirabilis also appear to be symmetrical with alae length on each end of the pseudoamphiasters being equal whereas they appear asymmetrical in C. mexicana sp. nov. owing to the difference in alae length on each side. In general, sigmas appear to be larger in C. mirabilis as well. Finally, C. mexicana sp. nov. was collected from basaltic pillow lavas and, presumably, was attached via a holdfast disc whereas C. mirabilis was retrieved from abyssal sediments and has root-like rhizoids as its point of attachment., Published as part of Lonny Lundsten, Henry M. Reiswig & William C. Austin, 2017, Three new species of Cladorhiza (Demospongiae, Poecilosclerida, Cladorhizidae) from the Northeast Pacific Ocean, pp. 247-260 in Zootaxa 4317 (2) on pages 253-255, DOI: 10.11646/zootaxa.4317.2.3, http://zenodo.org/record/884256, {"references":["Lehnert, H., Watling, L. & Stone, R. (2005) Cladorhiza corona sp. nov. (Porifera: Demospongiae: Cladorhizidae) from the Aleutian islands (Alaska). Journal of the Marine Biological Association of The United Kingdom, 85, 1359 - 1366. https: // doi. org / 10.1017 / S 0025315405012531"]}

Genus Cladorhiza Sars, 1872 Type species: Cladorhiza abyssicola Sars, 1872. Diagnosis: Cladorhizidae with only anchorate unguiferate anisochelae (Lopes & Hajdu, 2013)., Published as part of Lonny Lundsten, Henry M. Reiswig & William C. Austin, 2017, Three new species of Cladorhiza (Demospongiae, Poecilosclerida, Cladorhizidae) from the Northeast Pacific Ocean, pp. 247-260 in Zootaxa 4317 (2) on pages 249-250, DOI: 10.11646/zootaxa.4317.2.3, http://zenodo.org/record/884256, {"references":["Sars, G. O. (1872) On some remarkable forms of animal life from the great deeps off the Norwegian coast. I. Partly from posthumous manuscripts of the late professor Dr. Michael Sars. Brogger & Christie, Christiania, pp. 62 - 82. http: // dx. doi. org / 10.5962 / bhl. title. 11274"]}

Lundsten, Lonny, Reiswig, Henry M., Austin, William C. (2014): Four new species of Cladorhizidae (Porifera, Demospongiae, Poecilosclerida) from the Northeast Pacific. Zootaxa 3786 (2): 101-123, DOI: http://dx.doi.org/10.11646/zootaxa.3786.2.1

Family Cladorhizidae Dendy, 1922 Diagnosis. Sponges, typically small, symmetrical, usually from deep water, with diagonal, radiating supporting processes and basal root adaptations for those living in soft sediments. Axial skeleton composed of monactinal or diactinal megascleres, from which radiating extra-axial tracts diverge to lateral processes. Microscleres include (an)isochelae, sigmas, forceps or micro(subtylo)styles (microspined, spear-shaped in a few cases). Considerable reduction to complete loss of the choanocytes being associated with an adaptation to carnivory (Hajdu & Vacelet, 2002)., Published as part of Lundsten, Lonny, Reiswig, Henry M. & Austin, William C., 2014, Four new species of Cladorhizidae (Porifera, Demospongiae, Poecilosclerida) from the Northeast Pacific, pp. 101-123 in Zootaxa 3786 (2) on page 104, DOI: 10.11646/zootaxa.3786.2.1, http://zenodo.org/record/4913404, {"references":["Dendy, A. (1922) Report on the Sigmatotetraxonida collected by H. M. S. \" Sealark \" in the Indian Ocean. Transactions of the Linnean Society of London, 18, 1 - 164.","Hajdu, E. & Vacelet, J. (2002) Family Cladorhizidae Dendy, 1922. In: Hooper, J. N. A. & van Soest. R. W. M. (Eds.), Systema Porifera: A guide to the classification of sponges. Kluwer Academic / Plenum Pub., N. Y., pp. 636 - 641."]}

Asbestopluma monticola sp. nov. Figs. 2 & 3 Type material. Holotype: CASIZ 192095; MBARI 941 -A1; January 27, 2006, Davidson Seamount off central California, USA; latitude: 35.722787, longitude: -122.722553, depth: 1280 m. The holotype was recovered from the summit of Davidson Seamount using the MBARI’s ROV Tiburon. Paratype: CASIZ 194901; MBARI V3745 - A1, Monterey Canyon, November 14, 2013; latitude: 36.72559, longitude: -122.01423, depth: 1323.28 m. The paratype was recovered from steep rock outcrop of the Monterey Canyon. Type locality. Holotype: Davidson Seamount, California, USA. Paratype: Monterey Canyon, USA. Etymology. The species name (Latin mont = mountain + - cola = dweller), mountain dweller, is descriptive of the type locality, where dense stands of this beautiful sponge thrive. Diagnosis. Branching Cladorhizidae with three size classes of megasclere styles and three microsclere types of a single size class including acanthose tylostyles, sigmas, and palmate anisochelae. Description. Holotype : an arborescent, dichotomously-branching sponge with bottle-brush arrangement of filaments 19.37 cm tall and 13 cm wide, but was likely wider as several branches were broken off before measuring (Fig. 2A–E). Filaments are 1–9 mm in length (Fig. 4A). At the base, the stalk is 7 mm wide and branches all taper to approximately 1 mm width distally. Attached to hard substrate via conic holdfast disk, 1.3 cm in width. Sponge is white in situ and in preserved state. Paratype: matching description above for holotype, 28 cm tall, 9 mm wide at conical base, 6 mm stalk width, and 2 mm branch tip width, tapering distally. Spicules. Large styles 1 (Fig. 3A, Table 1), fusiform, straight, often with pointed end rounded, in axes of branches and stem: L 751 ± 46 µm (n=53), W 25.5 ± 1.4 µm (n=53). Large styles 2 (Fig. 3B), fusiform, straight or slightly curved, in filaments and their inserts in branch axes: L 687± 69 µm (n=103), W 17.5 ± 2.8 µm (n=66). Large styles 3 (Fig. 3C), fusiform, thick, strongly bent, mainly in basal cone: L 462.1± 79.7 µm (n=85), W 39.97 ± 7.7 µm (n=67). Microacanthotylostrongyle (Fig. 3D) thin, rough, mostly curved, occurs in basal cone and sparsely throughout branch axes: L 98.1 ± 10.7 µm (n=50), W 1.7 ± 0.4 µm (n=50). Sigma (Fig. 3E) robust, contort, without profile discontinuity near ends (not clearly sigmancistroid), occurs throughout specimen: L 22.9 ± 1.5 µm (n=50). Palmate anisochelae (Fig. 3F) foot with frontal tooth bearing two broad lateral flukes and distal medial spine extending toward spicule center, lateral wings short and never meet the frontal tooth; without spurs; occurs throughout the specimen: L 11.8 ± 0.5 µm (n=50). Habitat and associated fauna. Asbestopluma monticola was first observed while conducting ROV dives at Davidson Seamount off central California in 2002. A single specimen was collected in 2006 while surveying Davidson Seamount once more. A dense population of A. monticola was observed there and they were noted as living attached to both the seafloor and, also, dead hexactinellid sponges. Since 2006, hundreds of additional observations of this species have been made. They are abundant in Monterey Canyon off northern California and central Oregon, a range of ~ 1000 km. They co-occur with numerous species of sponges (Staurocalyptus sp., Farrea sp., Chonelasma sp.), corals (Anthomastus ritteri Verrill, Paragorgia arborea Linnaeus, Keratosis sp., Corallium sp., Clavularia sp.), crustaceans (lithodid crabs, pandalid shrimps, amphipod), echinoderms (comatulid crinoids, Gorgonocephalus sp. ophiuroids, Hippasteria sp. asteroids), and vertebrates (Careproctus sp., egg case of Rajiformes, and Psychrolutes phrictus Stein & Bond). Small crustaceans like the pandalid shrimp were observed to be actively climbing upon and around the branches of A. monticola. The average depth of observation was 1236 m (±211; n=428). Oxygen concentration is low (0.85 ±0.3 ml/L; n=428) and temperature averages 3.18 °C (±0.54; n=428). Small crustacean prey were observed in various states of decomposition on A. monticola (Fig. 4A–D). Remarks. Among the 42 known species of Asbestopluma, eight species branch. These are compared with A. monticola below. Asbestopluma monticola differs from A. formosa (Vacelet 2006), in that it lacks the characteristic embryo-containing branching enlargements, they differ in branching patterns— A. formosa has fan shapedbranches that divide dichotomously three or four times in a single plane with long, thin, and parallel terminal branches, and A. monticola also lacks microstrongyles. Asbestopluma monticola resembles A. desmophora (Kelly and Vacelet, 2011), however, it lacks desmas and sigmancistras and has bent fusiform styles in its basal cone. Asbestopluma monticola differs from A. bitrichela (Lopes et al., 2011) in a lack of desmas and anchorate/ unguiforate anisochelae. This new species differs from A. delicata (Lopes et al., 2011) in the absence of microstrongyles and palmate isochelae. Asbestopluma monticola d iffers from A. magnifica (Lopes et al., 2011) in being much smaller (~50% less) in total length, in having a single size class of anisochelae, and having a microtylostrongyle. When compared to A. furcata (Lundbeck, 1905), A. monticola has larger megascleres and only one size class of anisochelae (A. furcata has two size classes of anisochelae). Asbestopluma monticola is very similar to A. ramosa Koltun, however, A. ramosa has a flabelliform branching pattern, with vertical branches emanating from a single point and much thicker branches averaging 1.2 cm. Asbestopluma ramosa has larger spicules, especially when comparing anisochelae (Koltun, 1959; Stone et al., 2011). Asbestopluma ramosa also does not appear to have the robust, bent fusiform styles of A. monticola. Asbestopluma monticola superficially resembles A. rickettsi (described below), however, A. monticola differs in having only one size class of anisochelae. In situ, A. rickettsi is more transparent and much more delicate looking than A. monticola. A comparison of spicule data for all known Asbestopluma species through 2011 is published in Lopes et al. (2011).

Genus Asbestopluma Topsent, 1901: 23 Type species. Cladorhiza pennatula Schmidt, 1875 (by subsequent designation). Diagnosis. Cladorhizidae with palmate and/or arcuate (an)isochelae and, in some cases, the latter in combination with tridentate anchorate anisochelae (Lopes & Hajdu, 2013)., Published as part of Lundsten, Lonny, Reiswig, Henry M. & Austin, William C., 2014, Four new species of Cladorhizidae (Porifera, Demospongiae, Poecilosclerida) from the Northeast Pacific, pp. 101-123 in Zootaxa 3786 (2) on page 104, DOI: 10.11646/zootaxa.3786.2.1, http://zenodo.org/record/4913404, {"references":["Topsent, E. (1901) Spongiaires. Resultats du voyage du S. Y. ' Belgica' en 1897 - 99 sous le commandement de A. de Gerlache de Gomery. Expedition antarctique belge. Zoologie, 4, 1 - 54, pls. I - VI.","Lopes, D. A. & Hajdu, E. (2013) Carnivorous sponges from deep-sea mounds in the Campos Basin (SW Atlantic), with the description of six new species (Cladorhizidae, Poecilosclerida, Demospongiae). Marine Biology Research, 10, 329 - 356. http: // dx. doi. org / 10.1080 / 17451000.2013.797587"]}

Asbestopluma rickettsi sp. nov. Figs. 5 & 6 Type material. Holotype: CASIZ 192771; MBARI specimen D472-A13b; collected by ROV Doc Ricketts May 19, 2013, northwest of La Jolla, California, USA; latitude: 32.90433, longitude: -117.78224, depth 1020 m. Paratype: CASIZ 192772; MBARI specimen D472-A13a; collected by ROV Doc Ricketts May 19, 2013, northwest of La Jolla, California, USA; latitude: 32.90433, longitude: -117.78224, depth 1020 m. Type locality. Northwest of La Jolla, California, USA. Etymology. Named in honor of Edward F. Ricketts, marine biologist and ecologist made popular as ���Doc Ricketts��� in John Steinbeck���s Cannery Row. He is best known as co-author of Between Pacific Tides, a pioneering book on intertidal ecology. Coincidentally, the type specimens were collected by MBARI���s ROV Doc Ricketts. Diagnosis. Branching Cladorhizidae with three size classes of megascleres and three microscleres including an acanthose tylostyle, and sigma of one size class, and palmate anisochelae of two size classes. Description. An arborescent, dichotomously-branching sponge with bottle-brush arrangement of filaments (Fig. 5A���C). Holotype: Sponge is 21.78 cm tall and 12.38 cm wide (Fig. 5D). At the base, the stalk is 4.5 mm wide and branches all taper to approximately 1 mm in width distally. Filaments are 0.9���1.2 mm in length (Fig. 5E���F). Attached to hard substrate via conic holdfast disk, 1.26 cm in width. Paratype: Filaments are 1.5 ��� 5 mm in length. Sponge is 21.78 cm tall and 12.38 cm wide (Fig. 5G). At the base, the stalk is 3.4 mm wide and branches all taper to approximately 1 mm width distally. Sponge is white in situ and in preserved state. Spicules. Large styles 1 (Fig. 6A, Table 1) fusiform, straight, often with pointed end rounded, in axes of branches and stem: L 956 �� 50 ��m (n=50), W 19.8 �� 1.8 ��m (n=50). Large styles 2 (Fig. 6B), fusiform, straight or slightly curved, in filaments and their inserts in branch axes: L 642.6 �� 62.6 ��m (n=50), W 14.0 �� 2.5 ��m (n=66). Large styles to anisostrongyles 3 (Fig. 6C), fusiform, thick, strongly bent, mainly in basal cone: L 555 �� 53 ��m (n=50), W 26.6 �� 6.4 ��m (n=50). Microacanthotylostrongyle (Fig. 6D) thin, rough, mostly curved, occurs in basal cone and sparsely throughout branch axes: L 102.6 �� 9.8 ��m (n=50), W 1.5 �� 0.4 ��m (n=50). Sigma (Fig. 6E) without profile discontinuity near ends (not clearly sigmancistroid), rare throughout specimen: L 17.06 �� 1.3 ��m (n=50). Anisochelae 1 (Fig 6F) robust, palmate with wide lateral wings and narrow tooth slightly wider than shaft: L 53.5 �� 5.3 ��m (n=50), occurs rarely throughout. Anisochelae 2 (Fig. 6G) palmate head, foot with frontal tooth bearing two broad lateral flukes, lateral wings short and never meet the frontal tooth; narrow lower foot shaft looks like a short blunt spur but true spur is lacking; occurs abundantly throughout the specimen: L 9.3 �� 0.7 ��m (n=50). Habitat and associated fauna. Asbestopluma rickettsi was observed and collected while surveying a chemosynthetic community in a low-oxygen basin off southern California, northwest of La Jolla. Twenty-one individuals were observed in an area of active fluid flow. The substrate was composed of outcrops of authigenic carbonate with a thin sediment veneer. Other organisms observed include vesicomyid clams, siboglinid tube worms, and mats of flocculent bacteria. Average depth of observation was 1031 m (��48.5; n=21), oxygen concentration was low at 0.33 ml/L (��0.001; n=21), and temperature averaged 3.93 ��C (��0.02; n=21). No evidence of crustacean prey capture was observed in A. rickettsi. This specimen was collected in an area with an active chemosynthetic community and was found to be utilizing methane-oxidizing bacteria as a food source (V. Orphan, California Institute of Technology, pers. comm.). It remains to be seen whether these bacteria are true symbionts, as has been demonstrated in one other species of Cladorhizidae. Remarks. Asbestopluma rickettsi differs from A. formosa (Vacelet, 2006), in that it lacks the characteristic embryo-containing branching enlargements, it does not have fan shaped branches divided dichotomously three or four times in a single plane with terminal branches being long, thin, and parallel, and it does not have microstrongyles. It differs from A. desmophora (Kelly and Vacelet, 2011) as it lacks both desmas and sigmancistras. This new species differs from A. bitrichela (Lopes et al., 2011) in a lack of desmas and anchorate/ unguiferate anisochelae. Asbestopluma rickettsi differs from A. delicata (Lopes et al., 2011) in absence of microstrongyles and palmate isochelae. It differs from A. magnifica (Lopes et al., 2011) considerably in size (A. magnifica is ~50% longer), in size classes of megascleres (A. rickettsi has larger styles), a larger anisochelae 1 size (~ 34 ��m vs. 52 ��m) and presence of large alae of large anisochelae. Asbestopluma rickettsi differs from A. furcata (Lundbeck, 1905) in having larger megasclere style sizes. A comparison of spicule data for all known Asbestopluma species through 2011 is published in Lopes et al., (2011). A. rickettsi differs from A. monticola in that it has two size classes of anisochelae., Published as part of Lundsten, Lonny, Reiswig, Henry M. & Austin, William C., 2014, Four new species of Cladorhizidae (Porifera, Demospongiae, Poecilosclerida) from the Northeast Pacific, pp. 101-123 in Zootaxa 3786 (2) on pages 109-112, DOI: 10.11646/zootaxa.3786.2.1, http://zenodo.org/record/4913404, {"references":["Vacelet, J. (2006) New carnivorous sponges (Porifera, Poecilosclerida) collected from manned submersibles in the deep Pacific. Zoological Journal of the Linnean Society, 148, 553 - 584. http: // dx. doi. org / 10.1111 / j. 1096 - 3642.2006.00234. x","Kelly, M. & Vacelet, J. (2011) Three new remarkable carnivorous sponges (Porifera, Cladorhizidae) from deep New Zealand and Australian (Macquarie Island) waters. Zootaxa, 2976, 55 - 68.","Lopes, D. A., Bravo, A. & Hajdu, E. (2011) New carnivorous sponges (Cladorhizidae: Poecilosclerida: Demospongiae) from off Diego Ramirez Archipelago (south Chile), with comments on taxonomy and biogeography of the family. Invertebrate Systematics, 25, 407 - 443. http: // dx. doi. org / 10.1071 / is 11015","Lundbeck, W. (1905) Porifera. (Part II.) Desmacidonidae (pars.). In: The Danish Ingolf-Expedition, 6 (2), pp. 1 - 219, pls I - XX."]}

Cladorhiza evae sp. nov. Figs. 10���12 Type material. Holotype: CASIZ 192773; MBARI sample D399-A4a; collected by ROV Doc Ricketts April 28, 2012, in the newly found Alarcon Rise hydrothermal vent field, east of Cabo Pulmo, BCS, Mexico; latitude: 23.37753, longitude: -108.53125, depth: 2299 m. Paratypes: MBARI sample D399-A4b (CASIZ 192774) and c (CASIZ 192775); collected by ROV Doc Ricketts April 28, 2012, in the newly found Alarcon Rise hydrothermal vent field, east of Cabo Pulmo, BCS, Mexico; latitude: 23.37753, longitude: -108.53125 bottle-brush filament arrangement, depth: 2299 m. Type locality. Alarcon Rise hydrothermal vent field, east of Cabo Pulmo, BCS, Mexico. Etymology. Named in honor of Eve Lundsten, beautiful wife of the first author whose commitment and support have endured through the years. Eve���s love for the Gulf of California also inspired this naming as the type specimen was collected in the deep sea, east Cabo Pulmo, Baja California Sur, Mexico, near where we honeymooned in 2006. Diagnosis. Cladorhizidae unbranched, with three size classes of megaslere styles and four microsclere categories including sigmas of two size classes, contort sigmancistra, and unguiferate anisochelae. Description. A stipitate sponge with filaments arranged in four or five discreet longitudinal rows, with valleys or depressions between rows (Fig. 10A���E). All three specimens with partial rhizoids (Fig. 10D); filaments long and fragile on specimens a (holotype) and b (paratype), shorter on the smaller and, presumably, younger, c (paratype). Holotype: 18.7 cm long, 3.2 mm wide at base, filaments up to 1.97 cm long. Paratypes: (b) 17.9 cm long, 3.4 mm wide at base, filaments up to 1.8 cm long, (c) 13.7 cm long, 1.7 mm wide at base, filaments up to 5.4 mm long. White in situ and in preserved state. Spicules. Large styles 1 (Fig. 11A, Table 1) fusiform, straight, often with pointed end rounded, found throughout: L 2243 �� 460 ��m (n=13). Large style 2 (Fig. 11B) fusiform, straight, often with pointed end rounded, found throughout: L 1224.36 �� 432.3 ��m (n=263), W 26.13 �� 11.07 ��m (n=50). Large style 3 (Fig. 11C) fusiform, straight, often with pointed end rounded, found throughout, however, smaller styles more abundant in filaments: L 825 �� 132.7 ��m (n=21). Sigma 1 (Fig. 11D) robust, not contort, nor sigmancistroid; abundant in filament and axis: L 170.35 �� 9.7 ��m (n=170). Sigma 2 (Fig. 11E) most 15�� contort, some 90�� contort, few flat, abundant in filament and axis: L 72.08 �� 11.76 ��m (n=111): Sigmancistras (Fig. 12A) 90�� contort, abundant in filament and axis: L 42.3 �� 2.3 ��m (n=50). Multidentate unguiferate anisochelae (Fig. 12B) five teeth on head and three on foot, abundant in filaments and axis: L 22.6 �� 1.6 ��m (n=50). Habitat and associated fauna. Cladorhiza evae was collected from an inactive hydrothermal chimney that was covered in hydrothermally altered sediment. Galatheid and bythograeid crabs were observed in close proximity to C. evae on this inactive chimney. Nearby active chimneys had much richer communities of organisms with dense populations of siboglinid worms, galatheid and bythograeid crabs, and Thermarces sp., a zoarcid fish. Average depth of observation was 2373 m (��154; n=8), oxygen concentration was 1.54 ml/L (��0.27; n=8), and temperature averaged 2.02 ��C (��0.23; n=8). Numerous crustacean prey were observed in various states of decomposition on C. evae (Fig. 4F���G). Remarks. Of the thirty-six other species of Cladorhiza currently recognized (Lopes and Hajdu, 2013; van Soest et al., 2013), C. evae differs from even the most similar in spicule size classes and suites. For example, C. evae differs from C. rectangularis (Ridley and Dendy, 1887) in having greater style width, larger sigmas of two size classes, and the presence of a sigmancistra. Cladorhiza linearis (Ridley and Dendy, 1887) differs from C. evae in having larger styles (to 3000 ��m), small, non-contort sigmas of one size class, and larger anisochelae. Cladorhiza septemdentalis (Koltun, 1972) has smaller styles, larger anisochelae, and smaller sigmancistras than C. evae. Similarly, C. thompsoni (Topsent, 1909) has smaller styles, larger anisochelae, and no sigmancistras. Cladorhiza segonzaci (Vacelet, 2006) has smaller styles, sigmas, and sigmancistras. Cladorhiza evae differs from C. caillieti in the presence of a large (~ 2500 ��m) size class of megascleres, a single size class of anisochelae, and no small, thin, contort sigmas., Published as part of Lundsten, Lonny, Reiswig, Henry M. & Austin, William C., 2014, Four new species of Cladorhizidae (Porifera, Demospongiae, Poecilosclerida) from the Northeast Pacific, pp. 101-123 in Zootaxa 3786 (2) on pages 116-120, DOI: 10.11646/zootaxa.3786.2.1, http://zenodo.org/record/4913404, {"references":["Lopes, D. A. & Hajdu, E. (2013) Carnivorous sponges from deep-sea mounds in the Campos Basin (SW Atlantic), with the description of six new species (Cladorhizidae, Poecilosclerida, Demospongiae). Marine Biology Research, 10, 329 - 356. http: // dx. doi. org / 10.1080 / 17451000.2013.797587","van Soest, R. W. M., Boury-Esnault, N., Hooper, J. N. A., Rutzler, K., de Voogd, N. J., Alvarez de Glasby, B., Hajdu, E., Pisera, A. B., Manconi, R., Schoenberg, C., Janussen, D., Tabachnick, K. R., Klautau, M., Picton, B., Kelly, M., Vacelet, J., Dohrmann, M. & Diaz, M. C. (2013) World Porifera Database. Available from: http: // www. marinespecies. org / porifera (accessed 19 November 2013)","Ridley, S. O. & Dendy, A. (1887) Report on the Monaxonida collected by H. M. S. ' Challenger' during the years 1873 - 1876. Report on the Scientific Results of the Voyage of H. M. S. ' Challenger', 1873 - 1876. Zoology, 20 (59), i - lxviii, 1 - 275, pls. I - LI, 1 map.","Topsent, E. (1909) Etude sur quelques Cladorhiza et sur Euchelipluma pristina n. g. et n. sp. Bulletin de l'Institut oceanographique, Monaco, 1909 (151), 1 - 23, pls I - II.","Vacelet, J. (2006) New carnivorous sponges (Porifera, Poecilosclerida) collected from manned submersibles in the deep Pacific. Zoological Journal of the Linnean Society, 148, 553 - 584. http: // dx. doi. org / 10.1111 / j. 1096 - 3642.2006.00234. x"]}

Cladorhiza caillieti sp. nov. Figs. 7���9 Type material. Holotype: CASIZ 194449; MBARI specimen D266-A1d; collected by ROV Doc Ricketts August 1, 2011, at Endeavor Segment, Juan de Fuca Ridge hydrothermal vent field, Canada; latitude: 47.95685, longitude: -129.08485, depth 2071 m. Paratypes: MBARI specimen D266-A1a (CASIZ 192776),b (CASIZ 192777),c (CASIZ 192778); collected by ROV Doc Ricketts August 1, 2011, at Endeavor Segment, Juan de Fuca Ridge hydrothermal vent field, Canada; latitude: 47.95685, longitude: -129.08485, depth 2071 m. Type locality. Endeavor Segment, Juan de Fuca Ridge hydrothermal vent field, Canada. Etymology. Named in honor of Gregor M. Cailliet, Ph.D., Professor Emeritus, Moss Landing Marine Laboratories for his contributions to ichthyology and deep-sea biology and for providing mentorship and inspiration to graduates of Moss Landing Marine Laboratories, including the first author. Diagnosis. Cladorhizidae unbranched, with bottle-brush filament arrangement, two size classes of fusiform megasleres, four microsclere types including flat sigmas in two size classes, a third, thin, contort sigma, a sigmancistra, and two size classes of unguiferate anisochelae. Description. A stipitate sponge with bottle-brush filament arrangement (Fig. 7A���C). One collected specimen with partial rhizoid (Fig. 7D); three others broken but assumed to have had rhizoid as well. Holotype: 7 cm long, 2.1 mm wide, filaments up to 1.72 cm long (Fig. 7C left & D). Paratypes (a) 9.13 cm long, 2.6 mm wide at base, (b) 8.7 cm long, 2.3 mm wide at base; specimen, (c) 5.4 cm long (appears broken), 3.6 mm wide at base. Long, fragile filaments, up to 1.72 cm long, which break off easily. White in situ and in preserved state. Spicules. Large styles 1 (Figs. 8A, Table 1) fusiform, straight, often with pointed end rounded common in axis and filament: L 1371.58 �� 104.91 ��m (n=155), W 34.38 �� 6.92 ��m (n=155). Large style 2 (Fig. 8B) fusiform, straight more abundant in filament and rhizoid: L 807.22 �� 174.02 ��m (n=237), W 18.04 �� 5.62. Large style 3 (Fig. 8C) non-fusiform, straight common throughout but more abundant in filaments and rhizoid: L 381.9 �� 87.04 ��m, W 10.74 �� 2.14 ��m (n=103). Sigma 1 (Fig. 8D) robust, ���flat back���, common in filaments, rare in axis: L 160.1 �� 11.87 (n=105). Sigma 2 (Fig. 8E) flat, small abundant in filaments but rare in axis: L 95.58 �� 18.55 ��m (n=89). Sigma 3: (Fig. 9A) thin, contort common in axis, filaments, and rhizoid: L 96.17 �� 16.61 (n=60). Sigmancistras (Fig. 9B) small, contort abundant in filaments and axis: L 44.05 �� 2.28 ��m (n=150). Multidentate unguiferate anisochelae typically five teeth on head, 3���4 teeth on foot, abundant on filaments and axis. Anisochelae in two size classes: anisochelae 1 (Fig. 9C): L 33.98 �� 2.24 (n=150); anisochelae 2 (Fig. 9D): L 18.88 �� 1.67 (n=150). Habitat and associated fauna. Cladorhiza caillieti was observed and collected on the Endeavor Segment of the Juan de Fuca Ridge where lava flows had very little sediment cover, if at all. They were often observed in a downward facing position, hanging from the underside of overhanging ledges of basalt (Fig. 7A���B). Other organisms observed in this community included Primnoidae and Swiftia sp. of Gorgonacea, Anthomastus sp. of Alcyonacea, serpulid polychaete worms, comatulid crinoids, and numerous unidentified species of sponges. Average depth of observation was 2149 m (��172; n=5), oxygen concentration was 1.46 ml/L (��0.11; n=5), and temperature averaged 1.87 ��C (��0.05; n=5). Numerous crustacean prey were observed in various states of decomposition on C. caillieti (Fig. 4E). Remarks. Thirty-six other species of Cladorhiza are currently recognized (Lopes and Hajdu, 2013; van Soest et al., 2013) from sublittoral (110 m) to hadal (7295 m) depths. Cladorhiza caillieti differs from all other Cladorhiza in several ways including having different shape and two size classes of anisochelae, three different sigmas (including large flat-backed sigmas, smaller smooth sigmas, and even smaller thin, contort sigmas), and one size of sigmancistra. Cladorhiza caillieti differs from C. evae sp. nov. (described below) in spicule size classes and types. Cladorhiza caillieti has two size classes of anisochelae, the presence of a small, contort sigma, and nonfusiform small styles., Published as part of Lundsten, Lonny, Reiswig, Henry M. & Austin, William C., 2014, Four new species of Cladorhizidae (Porifera, Demospongiae, Poecilosclerida) from the Northeast Pacific, pp. 101-123 in Zootaxa 3786 (2) on pages 112-116, DOI: 10.11646/zootaxa.3786.2.1, http://zenodo.org/record/4913404, {"references":["Lopes, D. A. & Hajdu, E. (2013) Carnivorous sponges from deep-sea mounds in the Campos Basin (SW Atlantic), with the description of six new species (Cladorhizidae, Poecilosclerida, Demospongiae). Marine Biology Research, 10, 329 - 356. http: // dx. doi. org / 10.1080 / 17451000.2013.797587","van Soest, R. W. M., Boury-Esnault, N., Hooper, J. N. A., Rutzler, K., de Voogd, N. J., Alvarez de Glasby, B., Hajdu, E., Pisera, A. B., Manconi, R., Schoenberg, C., Janussen, D., Tabachnick, K. R., Klautau, M., Picton, B., Kelly, M., Vacelet, J., Dohrmann, M. & Diaz, M. C. (2013) World Porifera Database. Available from: http: // www. marinespecies. org / porifera (accessed 19 November 2013)"]}

HIPPASTERIA NOZAWAI GOTO, 1914 Goto, 1914: 344. Occurrence: Hokkaido, northern Japan. (No depth information available.) Material examined: None., Published as part of Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, pp. 266-301 in Zoological Journal of the Linnean Society 160 (2) on pages 286-287, DOI: 10.1111/j.1096-3642.2010.00638.x, {"references":["Goto H. 1914. A descriptive monograph of Japanese Asteroidea. 1. Journal of the College of Sciences, Imperial University of Tokyo 29: 1 - 808."]}

HIPPASTERIA HEATHI FISHER, 1905 Fisher, 1905: 319; 1911: 231; Krieger & Wing, 2002: 86. Occurrence: Alaska, Gulf of Alaska. 377–454 m. Material examined: HOLOTYPE: USNM 22338, Guard Island, Behm Canal, Alexander Archipelago, Alaska, 55°N, 131°W, 377–454 m, coll. USFC Albatross, 9.vii.1903 (1 dry spec. R = 7.8, r = 3.9)., Published as part of Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, pp. 266-301 in Zoological Journal of the Linnean Society 160 (2) on page 286, DOI: 10.1111/j.1096-3642.2010.00638.x, {"references":["Fisher WK. 1905. New starfishes from deep water off California and Alaska. Bulletin of the Bureau of Fisheries 24: 291 - 320.","Fisher WK. 1911. Asteroidea of the North Pacific and adjacent waters. 1. Phanerozonia and Spinulosida. Bulletin of the US National Museum 76: xiii + 420 pp. 122 pls.","Krieger KJ, Wing BL. 2002. Megafauna associations with deepwater corals (Primnoa spp.) in the Gulf of Alaska. Hydrobiologia 471: 83 - 90."]}

HIPPASTERIA MAMMIFERA DJAKONOV, 1950 Djakonov, 1950: 54 (1968: 45), 1952: 409. Occurrence: Okhotsk Sea. 97 m. Comments: This species was described by Djakonov (1950) as a separate species based on extremely swollen and hemispherical marginal and abactinal plates. This character is plesiomorphic to H. spinosa (and to a certain extent, H. phrygiana), which undermines the distinctiveness of this species and further lends support to its synonymy with H. spinosa. Material examined: None., Published as part of Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, pp. 266-301 in Zoological Journal of the Linnean Society 160 (2) on page 286, DOI: 10.1111/j.1096-3642.2010.00638.x, {"references":["Djakonov AM. 1950. Sea stars (asteroids) of the USSR seas. Izdatel'stvo Akademii Nauk SSSR Moskva-Leningrad 34: 1 - 203.","Djakonov AM. [Translated as Dyakonov] 1968. Sea stars (asteroids) of the USSR seas. In: Strelkov AA, ed. Keys to the fauna of the USSR 34. Zoological Institute of the Academy of Sciences of the USSR. Jerusalem: Israel Program for scientific translations Ltd. 183 pp."]}

STHENASTER GEN. NOV. Description: As for species., Published as part of Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, pp. 266-301 in Zoological Journal of the Linnean Society 160 (2) on page 274, DOI: 10.1111/j.1096-3642.2010.00638.x

HIPPASTERIA FALKLANDICA FISHER, 1940 Fisher, 1940: 125; Bernasconi, 1973: 287; Clark & Downey, 1992: 247; Stampanato & Jangoux, 2004: 6; McKnight, 2006: 97 Occurrence: Falkland Islands (=Islas Malvinas), northern Argentina, Marion and Prince Edward Islands region to south of Tasmania, approx. 49°S, 150°E. 225–1148 m. Material examined: None., Published as part of Mah, Christopher, Nizinski, Martha & Lundsten, Lonny, 2010, Phylogenetic revision of the Hippasterinae (Goniasteridae; Asteroidea): systematics of deep sea corallivores, including one new genus and three new species, pp. 266-301 in Zoological Journal of the Linnean Society 160 (2) on page 286, DOI: 10.1111/j.1096-3642.2010.00638.x, {"references":["Fisher WK. 1940. Asteroidea. Discovery Reports 20: 69 - 306.","Bernasconi I. 1973. Los equinodermos colectados por el Walther Herwig en el Atlantico Sudoeste. Revista del Museo Argentino de Ciencias Naturales 3: 287 - 334.","Clark AM, Downey ME. 1992. Starfishes of the Atlantic. London: Chapman and Hall.","Stampanato S, Jangoux M. 2004. The asteroid fauna (Echinodermata) of Marion and Prince Edward Islands. Annals of the South African Museum 112: 1 - 16.","McKnight DG. 2006. The Marine Fauna of New Zealand: Echinodermata: Asteroidea (sea stars). 3. Orders Velatida, Spinulosida, Forcipulatida, Brisingida with addenda to Paxillosida, Valvatida. NIWA Biodiversity Memoir 120: 1 - 187."]}