Eptatretus goslinei, Mincarone & Plachetzki & McCORD & Winegard & Fernholm & Gonzalez & Fudge, 2021

Mincarone, M. M., Plachetzki, D., McCORD, C. L., Winegard, T. M., Fernholm, B., Gonzalez, C. J. & Fudge, D. S., 2021, Review of the hagfishes (Myxinidae) from the Galapagos Islands, with descriptions of four new species and their phylogenetic relationships, Zoological Journal of the Linnean Society 192, pp. 453-474 : 459-461

EPTATRETUS GOSLINEI SP. NOV.

GOSLINE’ S HAGFISH

( FIGS 1, 2B, 3B, 5; TABLES 1–3)

Z o o b a n k r e g i s t r a t i o n. u r n: l s i d: z o o b a n k. org:act: A0F33266-3F54-4B7E-936B-0766CA231683

H o l o t y p e: S I O 1 9- 7 8, 3 0 0 m m, N W I s a b e l a Island, between Cabo Berkeley and Punta Flores, 00°01’54.47”N, 91°33’02.12”W, 467 m depth, Queen

Mabel, sta. G23, baited trap, Douglas Fudge et al., 7 June 2019, 12:20–15:00 h.

Paratypes: MCCDRS 9403 COI, 16S, 14(234–347 mm) and SIO 19–79 COI, 16S, 2(305–360 mm), taken with the holotype . MCCDRS 9402 COI, 16S, 1(305 mm), NW Fernandina Island, Cabo Douglas, 00°17’43.73”S, 91°39’19.61” W, 478 m depth, Queen Mabel, sta. G21, baited trap, Douglas Fudge et al., 6 June 2019 , 15:06–16:52 h.

Diagnosis: Eptatretus goslinei differs from all congeners, except E. astrolabium Fernholm & Mincarone, 2010 from Papua New Guinea, E. caribbaeus Fernholm, 1982 from the Caribbean Sea, E. carlhubbsi McMillan & Wisner, 1984 from Hawaii, Wake, and Tinian islands, E. cirrhatus (Forster in Bloch & Schneider, 1801) from southeastern Australia and New Zealand, E. cryptus Roberts & Stewart, 2015 from New Zealand, E. goliath Mincarone & Stewart, 2006 from New Zealand, E. laurahubbsae McMillan & Wisner, 1984 from Juan Fernández Island, E. menezesi Mincarone, 2000 from southern Brazil and E. strahani McMillan & Wisner, 1984 from the Philippines and western Australia, by having seven pairs of gill apertures well spaced and arranged in a near straight line. Eptatretus goslinei differs from these seven-gilled congeners by having: 9–12 anterior unicusps (vs. 13–17 in E. carlhubbsi and E. laurahubbsae ); 47–58 total cusps (vs. 61–71 in E. carlhubbsi , 61–68 in E. laurahubbsae ); 65–72 total pores (vs. 83–84 in E. astrolabium , 79–85 in E. caribbeaus , 93–110 in E. carlhubbsi , 82–91 in E. cirrhatus , 78–86 in E. cryptus , 89–95 in E. goliath , 97–105 in E. laurahubbsae , 86–94 in E. menezesi , 76–86 in E. strahani ); and by having two bilaterally symmetrical nasal-sinus papillae (vs. no nasalsinus papillae in E. astrolabium and E. caribbeaus ) ( Fernholm, 1982; McMillan & Wisner, 1984; Mincarone, 2000; Mok, 2001; Mincarone & Stewart, 2006; Fernholm & Mincarone, 2010; Mincarone & Fernholm, 2010; Zintzen et al., 2015).

Description: Body elongated, subcylindrical at p r e b r a n ch i a l a n d b r a n ch i a l r e g i o n s, l a t e r a l l y compressed at trunk and strongly compressed at tail. Rostrum bluntly rounded. Eyespots conspicuous. Two small, bilaterally symmetrical nasal-sinus papillae in the dorsal surface of the nasal sinus (difficult to observe in some specimens). Three pairs of barbels on head, first two pairs subequal in size (1.3–2.4% TL) and adjacent to opening of nasopharyngeal duct; third pair longer (2.0–3.2% TL) and immediately adjacent to mouth. Ventral finfold absent (occasionally represented by a white line) or low (1–2 mm high), beginning within anterior third of trunk, extending with white tip; very distinct eyespots; gill apertures with white margins; ventral finfold appears only as a pale line or, when present, with white margin; caudal finfold occasionally with white margin ( Fig. 3). Colour in alcohol similar to that of live specimens.

Distribution and habitat: Galapagos Islands: known from 18 specimens collected in two localities off north-western Isabela (between Cabo Berkeley and Punta Flores), and north-western Fernandina (Cabo Douglas), at depths from 467 to 478 m ( Fig. 1).

Etymology: This species is named for Dr John M. Gosline (1944–2016), Professor in the Department of Zoology at the University of British Columbia (UBC), Vancouver, Canada, who pioneered work on the biomechanics of hagfish slime.

backwards to cloaca. Caudal finfold well developed, thin, extending around tail to dorsal surface, ending about over cloaca.

Body proportions (in percentage of TL; description of the holotype followed by range of paratypes in brackets): preocular length 6.3 (5.3–7.7); prebranchial length 23.0 (20.0–24.8); branchial length 10.0 (9.2–12.5); preventral length 50.0 (38.5– 55.7); trunk length 52.3 (49.0–55.0); tail length 15.7 (14.2–17.9); body width at PCD 7.0 (5.6–8.1); body depth at PCD 8.3 (6.6–9.4); body depth including VFF 9.3 (7.7–11.7); body depth excluding VFF 8.7 (7.6–10.7); body depth at cloaca 8.3 (6.7–9.2); tail depth 10.0 (7.7–11.0).

Counts (description of the holotype followed by range of paratypes in brackets): multicusp pattern 3/3; anterior unicusps 11 (9–12); posterior unicusps 10 (8–11); total cusps 52 (47–58). Prebranchial pores 11 (10–12); branchial pores 6 (6); trunk pores 42 (37–43); tail pores 13 (10–13); total pores 72 (65–72).

Seven pairs of gill pouches corresponding to seven pairs of gill apertures. Gill apertures well-spaced and linearly arranged. Last branchial duct confluent with pharyngocutaneous duct on left side, forming a larger aperture. Posterior tip of dental muscle reaches gill pouches 4–6. Ventral aorta branches at gill pouch 5–6.

Colour (in life): body dark brown (almost black in some specimens); mouth with white margin; barbels Remarks: Images of an unidentified species of Eptatretus were obtained off the north-eastern coast of Santa Cruz Island during the second expedition to the Galapagos in January 2020 ( Fig. 6). Although no specimens were collected, the colour pattern and the number of gill apertures observed in video are similar to those of E. goslinei .