Myxine greggi, 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 : 463-464

MYXINE GREGGI SP. NOV.

GREGG’ S HAGFISH

( FIGS 1, 2F, 4A, 5, 6D; TABLES 4–6)

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: 309DFFDD-9C79-42F6-AB51-4B43E1BAFB6C

Holotype: SIO 19-82, 408 mm, off NE Santa Cruz Island, 00°30’57.68”S, 90°10’17.90”W, 688 m depth, Valeska Yamile, sta. G24, baited trap, Douglas Fudge et al., 11 June 2019, 07:59–11:10 h.

Paratypes: MCCDRS 9404 , 11 (293-445 mm) and SIO 19–83 , 1 (515 mm), taken with the holotype . MCCDRS 9399 COI, 16S, 1 (457 mm), off NE Santa Cruz Island , 00°29’21.27”S, 90°10’22.48”W, 789 m depth, Valeska Yamile, baited trap, Douglas Fudge et al., 29 May 2019 , 10:16–11:37h. MCCDRS 9401 COI, 16S, 10 (181–485 mm) and SIO 19-84 COI, 16S, 1 (437 mm), off north-eastern Santa Cruz Island , 00°29’46.47”S, 90°12’00.73”W, 815 m depth, Valeska Yamile, sta. G5, baited trap, Douglas Fudge et al., 29 May 2019 , 09:21–12:39h.

Diagnosis: Myxine greggi differs from all congeners, except M. affinis Günther, 1870 and M. australis Jenyns, 1842 from southern South America, M. glutinosa Linnaeus, 1758 from the eastern North Atlantic and Mediterranean, M. limosa Girard, 1859 from the western North Atlantic, M. hubbsi Wisner & McMillan, 1995 from the eastern Pacific, M. hubbsoides Wisner & McMillan, 1995 from Chile, M. jespersenae Møller et al., 2005 from Greenland and Iceland, M. knappi Wisner & McMillan, 1995 from southern Argentina, M. kuoi Mok, 2002 from Taiwan, M. mcmillanae Hensley, 1991 from the Gulf of Mexico and Caribbean Sea, M. paucidens Regan, 1913 from Japan, M. sotoi Mincarone, 2001 from southern Brazil, and M. martinii from the Galapagos, by having six pairs of gill pouches and a 2/2 multicusp pattern of teeth. Myxine greggi differs from these congeners by having: 34–40 total cusps (vs. 30–32 in M. kuoi , 42–88 in M. mcmillanae and 26 in M. paucidens ); 22–26 prebranchial pores (vs. 30– 31 M. hubbsoides, 28–37 in M. jespersenae , 30–38 in M. knappi and 28–38 in M. sotoi ); 58–66 trunk pores (vs. 68–71 in M. hubbsoides and 52–54 in M. martinii ); 91–102 total pores (vs. 111–116 in M. hubbsoides and 107–121 in M. jespersenae ); and by having one single conspicuous nasal-sinus papilla in the mid-dorsal surfaceofthenasalsinus(vs.twobilaterallysymmetrical nasal-sinus papillae in M. jespersenae ). Myxine greggi can be also distinguished from the congeners with sixgill pouches by its colour pattern (body dark brown with white head vs. body entirely pigmented, without white head, in M. affinis , M. australis , M. hubbsoides , M. knappi , M. kuoi and M. paucidens ). Myxine greggi can be further distinguished from M. hubbsi by having a well-developed ventral finfold [3–7 mm high vs. vestigial to low (1–2 mm high)] ( Hensley, 1991; Wisner & McMillan, 1995; Mincarone, 2001; Mok, 2001, 2002; McMillan & Wisner, 2004; Møller et al., 2005).

Description: Body elongated, subcylindrical at prebranchial and branchial regions, laterally compressed at trunk and strongly compressed at tail. Rostrum triangular with rounded tip. One single conspicuous nasal-sinus papilla in the mid-dorsal surface of the nasal sinus. Eyespots absent. Three pairs of barbels on head: first two about equal in size (0.6– 1.4% TL) and adjacent to opening of nasopharyngeal duct; third pair longer (1.0–1.9% TL) and immediately adjacent to mouth. Ventral finfold well developed (3–7 mm high), beginning within anterior 10% of trunk, extending backward to the cloaca. Caudal finfold thin, rounded, beginning immediately posterior to edge of cloaca, 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): prebranchial length 25.7 (23.2–28.3); preventral length 27.5 (24.9–31.1); trunk length 62.3 (56.9–64.8); tail length 12.0 (8.7–13.9); body width at PCD 2.5 (2.6–3.6); body depth at PCD 3.6 (3.3–4.4); body depth including VFF 5.4 (3.3–5.5); body depth excluding VFF 3.7 (2.9–5.0); body depth at cloaca 3.4 (2.6–4.3); tail depth 4.2 (2.9–4.8).

Counts (description of the holotype followed by range of paratypes in brackets): multicusp pattern 2/2; anterior unicusps 6 (6–8); posterior unicusps 7 (7–8); total cusps 34 (34–40). Prebranchial pores 24 (22–26); trunk pores 66 (58–66); tail pores 10 (9–12); total pores 100 (91–102).

Six pairs of gill pouches, with efferent branchial ducts on either side combined into a single external gill aperture posterior to the gill pouches. Gill aperture on the left side confluent with the pharyngocutaneous duct aperture. Dental muscle overlies the first pair of gill pouches. Ventral aorta not branched.

Colour (in life): body dark brown, its dorsal region lighter than ventral (more evident in juveniles); head white, becoming gradually darker backwards; mouth and barbels white; gill apertures with white margin; ventral finfold the same colour as or even darker than body; caudal finfold the same colour as body ( Fig. 4). Colour in alcohol similar to that described for live specimens.

Distribution and habitat: Galapagos Islands: known from 25 specimens collected in three stations off northeastern Santa Cruz Island, between 688 and 815 m depth ( Fig. 1).

Etymology: This species is named for John Gregg, founder and president of the Western Flyer Foundation. John is an ardent supporter of marine biology research and a hagfish enthusiast. He joined the team during part of the Galapagos expedition and was on the boat when the specimens were collected.