Dieidolycus leptodermatus Anderson 1988

Dieidolycus leptodermatus Anderson, 1988

Dieidolycus leptodermatus Anderson, 1988: 72, fig. 15 (type locality: eastern Scotia Sea); Anderson, 1990b: 257, fig. 1.

Material examined. Scotia Sea: USNM 356650 (3 specimens; 115-150 mm SL) and RUSI 60087 (2; 88-171 mm SL): off Candelmas Isl., 57°00.4'S, 26°10.1'W, ISLAS ORCADAS coll. UMO 38, 10 ft beam trawl, 2744-2745 m, 22 May 1975, H. H. DeWitt. USNM 356655 (1; 134 mm SL): W of South Orkney Islands, 60°45.5'S, 48°13.5'W, ISLAS ORCADAS coll. UMO 116, 10 ft beam trawl, 2511-2542 m, 18 Feb. 1976, H. H. DeWitt.

Diagnosis. Dieidolycus leptodermatus is distinguished from its two congeners by the following combination of characters: suborbital pores 6, occipital and interorbital pores absent, pectoral-fin rays 16-17; dorsal fin origin associated with vertebrae 2-3 (not 23' as mistakenly given in Anderson, 1990b).

Description. Vertebrae 22-23 + 55-58 = 78-81; D 73-77; A 55-59; P 16-17; C (6) 8-10; pelvics 2; branchiostegal rays 6; gill rakers 2-3 + 9-11 = 12-13; vomerine teeth 6-15; palatine teeth 6-17; pseudobranch absent. Following proportions as percent SL: head length 21.3-24.7; head width 9.5-11.3; head depth 11.0-11.6; predorsal length 23.2-24.6; preanal length 46.6-48.4; pectoral base depth 4.4-5.2; pectoral-fin length 12.9-14.0; body depth 9.2-10.9; gill slit length 7.5-8.4. Following proportions as percent HL: head width 40.7-52.9; head depth 49.1-52.1; upper jaw length 34.5-38.5; snout length 26.5-33.0; eye diameter 12.4-15.5; gill slit length 33.4-37.4; pectoral-fin length 58.1-62.4; interorbital width 6.6-7.9; interpupillary width 20.3-27.2; caudal-fin length 20.9-25.4; pelvic-fin length 7.2-24.4. Pectoral base/depth ratio: 31.7-40.1.

Head roughly triangular, eye (spectacle) small, head pores prominent, with whitish outline. Flesh gelatinous, but lateral line present (usually absent in gelatinous zoarcids; Anderson, 1994). Lateral line originating just above upper end of gill opening and coursing midlaterally to tail tip (lateral line said to be absent in original description owing to faded specimens; Anderson and Pequeno-R, 1998). Pelvic-fin length highly variable, as dermal sheath covering rays extends distally with growth. Smallest specimen (88 mm SL) with pelvic length 24.4% HL, two largest (150-171 mm SL) with pelvic length 7.2-9.2% HL respectively. Caudal fin rays also quite variable, with usually 2 epural and 7-8 hypural rays, but one fish with 0 + 6 rays and one with 1 + 8 rays. Preoperculomandibular pores 8, suborbital pores 5 + 0, supraorbital (nasal) pores 2, postorbital pores 2 (1 and 4 present except one in USNM 356650, 115 mm SL, with left postorbitals 1, 3 and 4 present), interorbital and occipital pores absent.

Remarks. This rare eelpout was originally described from three specimens taken in the Scotia and Ross seas at depths of 2273-3040 m by the U.S. Antarctic Research Program in 1966-1967. The present six specimens include four smaller and one larger than the type series, including the largest known, a 171 mm SL juvenile female. The size of the immature ovary of this specimen indicates the species probably attains more than 300 mm.