Ophthalmolycus bothriocephalus ( Pappenheim, 1912 )

M. Eric Anderson, 2006, Studies on the Zoarcidae of the southern hemisphere. X. New records from western Antarctica., Zootaxa 1110, pp. 1-15 : 10-11

Ophthalmolycus bothriocephalus ( Pappenheim, 1912)

Lycodes bothriocephalus Pappenheim, 1912: 178 , pl. X, fig. 2 (type locality: Davis Sea ).

Austrolycichthys bothriocephalus : Regan, 1913: 245; Norman, 1938: 80, fig. 10.

Ophthalmolycus bothriocephalus : Regan, 1914: 32; Anderson, 1988: 84, figs. 26, 27; Anderson, 1990b: 273, fig. 21.

Material examined. South Shetland Islands ( Bransfield Strait ): MCZ 126362 (17 specimens; 145-250 mm SL) and RUSI 48029 (5; 177-215 mm SL), 61°39'S, 58°04'W, 316 m, POLAR DUKE sta. KEH94-OT04, bottom trawl, 24 Oct. 1994, K. Hartel. MCZ 127323 (4; 220-260 mm SL), 61°42'S, 57°31'W, 380 m, POLAR DUKE sta. KEH94- OT03 , K. Hartel. MCZ 127325 (2; 267-277 mm SL), 61°39.3'S, 58°00.2'W, 317 m, POLAR DUKE sta. KEH 94-OT02 , K. Hartel. MCZ 127326 (13; 155-243 mm SL), 61°48'S, 58°48'W, 285 m, POLAR DUKE sta. KEH94-OT06 . Ross Sea: RUSI 56529 (2; 121-181 mm SL), 74°17.7'S, 171°56.9'E, 465 m, NATHANIEL B. PALMER 97-9 , bottom trawl, 30 Dec. 1997, J. Eastman.

Diagnosis. Ophthalmolycus bothriocephalus is distinguished from its congeners by the following combination of characters: pelvic fins present; branchiostegal rays 6; pectoral-fin rays 12-15; lateral line single, mediolateral; pseudobranch absent or reduced; vertebrae 20-24 + 73-88 = 95-111.

Description. Vetebrae 20-22 + 73-84 = 95-106; D 89-99; A 74-85; P 12-15; C 9-11; pelvics 2-3; branchiostegal rays 6; gill rakers 2-4 + 7-10 = 10-13; vomerine teeth 3-6; palatine teeth 2-8; pseudobranch absent or with 2-4 reduced filaments in large adults; pyloric caeca 2. Following proportions as percent SL: head length 15.0-20.2; head width 6.2-9.3; head depth 6.8-8.6; predorsal length 16.0-18.2; preanal length 31.9-39.2; pectoral base depth 3.6-4.5; pectoral-fin length 9.1-11.7; body depth 6.9-8.9; gill slit length 4.3-6.5. Following proportions as percent HL: head width 41.6-51.3; head depth 45.4-47.9; upper jaw length 32.7-37.8 (juveniles and females), 41.0-47.9 (adult males); snout length 26.1-30.2; eye diameter 16.3-19.4; gill slit length 28.8-35.8; pectoral-fin length 53.6-69.3; interorbital width 8.0-10.5; interpupillary width 23.8-24.7; caudal-fin length 15.9-22.2; pelvic-fin length 15.0-21.1. Pectoral base/length ratio: 34.8-38.2.

No variation in head pore pattern from that reported by Anderson (1988): preoperculomandibulars 8; suborbitals 6 + 0; postorbitals 2 (pores 1 and 4); nasals 2; occipitals and interorbital absent. Caudal fin with 1-2 epural, four upper hypural and 4-5 lower hypural rays. Dorsal fin origin associated with vertebrae 2-3, with no free pterygiophores. Anal fin origin associated with ultimate precaudal vertebra, with 2-5 pterygiophores inserted anterior to haemal spine of first caudal vertebra. Pelvic fin with lateral, vestigial ray absent in one specimen ( Anderson, 1988, fig. 27). Lateral line mediolateral, complete. Gill slit extending ventrally to opposite lowermost pectoral ray in largest specimens, slightly above it in smaller fish. Pyloric caeca equal to eye diameter in smaller fish, 56-67% eye diameter in fish over 170 mm SL.

Remarks. Before the 1990s this species was known in museum collections around the world from fewer than 20 specimens, all from the Weddell Sea east to the Davis Sea. Intensive collecting thereafter has shown that it is common off the Antarctic Peninsula (hundreds taken during 1994 WHOI cruise, K. Hartel, pers. comm.), less so in the Ross Sea (N. B. PALMER cruises), and is thus confirmed to be circumantarctic.

Some differences were noted between the Antarctic Peninsula specimens and the remainder of the material ( Anderson, 1988 plus Ross Sea material herein). These had slightly longer gill slits, 3-4 rudimentary pseudobranch filaments and lower counts of axial skeletal elements (vertebrae 20-22 + 73-76 = 95-98; D 89-92; A 74-77). These features alter my previous diagnosis of the species.