Paraliparis longicaecus, Stein, 2012

Stein, David L., 2012, Snailfishes (Family Liparidae) of the Ross Sea, Antarctica, and Closely Adjacent Waters 3285, Zootaxa 3285, pp. 1-120 : 60-64

Paraliparis longicaecus n. sp.

Figs. 41, 42

Holotype. NMNZ P.043691, male, 274 mm TL, 254 mm SL, 71°55.80' S, 173°18.08' E, NW edge of Mawson Bank, R / V Tangaroa, Stn. IPY / CAML TAN 0802 /144, 23 February 2008, 1431– 1658 m. NMNZ P.043691/1, cleared and stained right pectoral girdle.

Diagnosis. V 69, P 21, C 7. Radials 4 (3+1), R1, R3 notched; scapula with helve, coracoid with basal notch. Chin pores paired, surrounding tissue fold probably present. Teeth sharp canines. Premaxillary teeth about 30, decreasing in size anteriorly, uniserial except near symphysis, where irregularly bi-or tri-serial for about12 teeth; mandibular teeth smaller, uniserial, about 50. HL 19% SL, upper jaw about 43% HL, preanal fin length about 230, anus-anal fin origin about 130, chin pore interspace 4% HL. Pyloric caeca ~70% HL. Body color pale rosy white.

Description. Counts. V 69 (14+55), D 59, A 52, C 7, P 21 (14+3+4), radials 4 (3+1), pc 7, pore formula unknown. Ratios. HL 18.6, HW na, sn 5.3, E 3.7, orbit 5.6, io 8.4, uj 7.9, go 2.8, bd na, preD ~33, preA 43.3, sna 16.2, ma 13.3, aAf 25.5, UPL 13.0, LPL 16.2, pcl 13.1. In % HL: HW na, sn 28.8, E 19.7, orbit 29.9, io 45.1, uj 42.6, go 15.0, ma 71.4, preD ~180, preA 232.8, sna 87.3, aAf 137.1, UPL 70.1, LPL 87.5, LLD 21.2, cp 3.8, pcl 70.8.

Head short and deep, dorsal profile rising steeply through flat interorbital region. Snout short. Nostrils with thickened raised rim, larger than nasal pores; anterior to orbit by about half eye diameter, on horizontal through mid-pupil. Mouth horizontal, inferior, oral cleft reaching below anterior third of orbit. Teeth simple, sharp canines, uniserial posteriorly in both jaws. About 30 premaxillary teeth in upper jaw, much smaller anteriorly; about 12 irregularly biserial inner teeth near symphysis. Mandibular teeth uniserial, about 50, becoming smaller anteriorly, extending much farther posteriorly than premaxillary teeth. Symphyseal gap present in both jaws. Eye prominent, pupil very large, almost equal to eye diameter. Interorbital space slightly less than half head length. Gill opening completely above pectoral fin base and directly above base of dorsal pectoral fin ray but not reaching it, its length less than1/6 head; opercular flap small, in shape an angle formed by opercle tip, its posterior margin vertical. Chin pore pair well separated, slightly smaller than those more posterior, the distance separating them about equal to two pore diameters. Surrounding skin damaged on left side, right side with clear tissue fold, possibly completely surrounding pore pair. Pore formula unknown.

Pectoral fin moderately short, upper lobe less than 3/4 HL, its longest ray not reaching midpoint of abdominal cavity. Uppermost ray on horizontal with middle of eye. Upper lobe rounded, of 14 rays, notch deep, notch rays three, well developed and long, but rudimentary (unsegmented, filamentous); lower lobe of four rays, insertion of lowest ray below cheek. Lower lobe longer than upper but not reaching to below tip of upper lobe. A wide gap equal to about 1/5 HL present between lower pectoral fin lobes. Right pectoral girdle with four (3+1) round radials; R2, R4 similar in size, larger, R1 and R3 slightly smaller. R1 with a small ventral notch, R3 dorsally notched. No fenestrae evident. Scapular helve well developed, blade larger and broader. Coracoid helve stout, broad, a deep basal notch present.

Body thick, deepest behind head above abdominal cavity. Dorsal fin insertion between vertebrae 9–10, anal fin insertion between vertebrae 15–16. Dorsal and anal fins deepest at about 4/5 of SL towards tail. Anus well behind bases of lower pectoral fin lobes, below upper lobe base and anterior to gill flap. Peritoneum visible through body wall. Pyloric caeca seven, very long, longest about ¾ HL. Hypural complex fused, slit absent. Caudal fin of seven rays (3/4), auxiliary rays absent. SECM apparently not well developed. Skin thick, fibrous.

Color of body in alcohol purplish brown, head, distal part of upper pectoral fin lobes, and lower lobe rays blackish brown, anal region blackish. Orobranchial cavity dusky-blackish. Peritoneum black, stomach and pyloric caeca pale.

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Distribution. Known only from the type, collected between 1431–1658 m on the northwest edge of Mawson Bank.

Etymology. Longicaecus from Latin longus, long, and caecus, blind, to denote the unusually long pyloric caeca of the holotype.

Comparisons. Most similar to P. alius in counts (except for caudal fin rays, 7 vs 6) and many proportions, and in having long pyloric caeca (71 and 63% HL respectively). It differs from P. alius in having a more posterior dorsal fin insertion (V 9–10 vs 6–7), longer lower pectoral lobe (16 vs 12% SL), the anus farther forward, resulting in a shorter mandible to anus distance (71 vs 93% HL), shorter snout to anus (87 vs 109), shorter preanal fin length (233 vs 283), and shorter anus to anal fin length (137 vs 174). Although the P. longicaecus specimen is an adult male, and that of P. alius an adult female, it’s unlikely that the preceding differences are the result of sexual dimorphism because P. longicaecus not only differs in caudal ray number but also in pectoral girdle structure, having notched R1 and R3 (vs unnotched) and notched coracoid (vs unnotched). It is also similar to P. plicatus in counts and proportions (see below) and may lack a chin pore fold, which can’t be positively determined owing to damage. P. longicaecus can also be distinguished from P. plicatus and from most other species by its very long pyloric caeca (almost ¾ HL). It differs from P. epacrognathus in having three well developed but unsegmented (rudimentary) pectoral notch rays (vs reduced to bases only), rounded lower jaw symphysis (vs sharply angled), chin pores farther posterior (vs at jaw tip), longer gill opening of about 15% HL (vs 11%), and longer snout to anus distance of about 87% HL (vs 80).

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