Paraliparis amerismos, Stein, 2012

Stein, David L., 2012, Snailfishes (Family Liparidae) of the Ross Sea, Antarctica, and Closely Adjacent Waters 3285, Zootaxa 3285, pp. 1-120 : 29-35

Paraliparis amerismos n. sp.

Figs. 19, 20

Holotype. NMNZ P.041444, sex unknown, 36 mm TL, 33 mm SL, 72°08.20´S, 175°38.60´E, Hillary Canyon (near Pennell Bank) Ross Sea, 30 December 2004, F/ V San Aspiring, Stn. OBS 2011/018, 1149–1358 m. Good condition but dorsoventrally flattened.

Diagnosis. V 74, D 66, A 61, P 22 (15+5+2). Dorsal, anal, caudal, and pectoral-fin rays unstriated or with very few striations; pectoral lower lobe rays two; gill opening above pectoral fin or in front of 1–2 rays. Teeth small, simple, thorn-like, forming moderately wide bands. Body pale with scattered melanophores except for black peritoneum showing through abdominal wall. Coronal pore absent.

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042623

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042623

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Paraliparis

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FIGURE

Description. Counts. V 74 (11+63), D 66, A 61, C 7 (3/4), P 22 (15+5+2), pc unknown, pore formula unknown. Ratios. HL 18.6, E 4.2, orbit 4.8, uj 6.9, go 3.9, bd 19.2, preD 23.1, preA 33.0, ma 21.0, aAf 12.7, UPL 12.3, LPL 7.5. In % HL: E 22.6, orbit 25.8, uj 37.1, go 21.0, ma 112.9, bd 103.2, preD 124.2, preA 177.4, aAf 67.7 UPL 66.1, LPL 40.3.

Head small, short, about 1/5 SL, anterior dorsal profile of head flat, sloping gradually down to blunt snout. Nostrils lacking tube or raised rim, about on a horizontal with upper margin of eye. Eye prominent, almost ¼ head. Mouth moderately (~30°) oblique, terminal, oral cleft reaching posteriorly to below front of eye, upper jaw to below mid-eye. Teeth small, sharp, thorn-like simple canines forming bands in both jaws. Premaxillary teeth in about 6–7 rows of 3–4 teeth each on each side of jaw forming a moderately wide band of well-spaced teeth, symphyseal gap present. Lower jaw teeth in 8–9 irregular oblique rows of up to four teeth each, forming narrower band of more closely spaced teeth than in premaxilla, symphyseal gap absent. Sensory pores damaged, pattern not discernible. Chin pores damaged, farther posterior than usual, probably widely separated, suprabranchial pore apparently single, difficult to find, coronal pore absent. Opercular flap small, crescent-shaped, above pectoral fin and extending ventrally over no more than 1–2 rays; opercular spine curved dorsally so tip points a little upwards.

Pectoral fin upper ray on horizontal between lower margin of orbit and posterior end of upper jaw; fin upper lobe moderately short, extending posteriorly almost to end of abdominal cavity above or slightly anterior to first anal fin ray. Lower lobe of only two rays, much shorter than upper. Notch moderately shallow, its rays much more widely spaced than upper and lower lobe rays, all well developed. Pectoral girdle not examined.

In alcohol, body pale with evenly distributed melanophores dorsally and ventrally, but somewhat denser on head; black peritoneum clearly visible through body wall. Orobranchial cavity dotted similarly to head, tongue dotted with melanophores.

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amerismos

Paraliparis

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FIGURE

Distribution. Known only from the holotype, collected at 1149–1358 m near Pennell Bank in the outer Ross Sea, Antarctica.

Etymology. From the Greek a-, absence of something, and merismos, division, denoting the general absence of fin ray segmentation.

Comparisons. The only other known liparid species with unsegmented fin rays is Praematoliparis anarthractae ( Stein and Tompkins 1989) from the Strait of Magellan, Tierra del Fuego. Andriashev (2003) described a new genus for this species based on its low numbers of vertebrae, dorsal and anal fin rays, lack of segmentation in the latter, and presence of a coronal pore. The new species similarly lacks almost all segmentation in the dorsal, anal, and caudal fins, but has no coronal pore and many more vertebrae (74 vs 45–48). Therefore it is described as a Paraliparis rather than Praematoliparis . It reduces the differences between the two genera to a single trenchant character, the presence or absence of a coronal pore. The presence of two lower lobe rays is noteworthy; few liparids ( Rhodichthys regina Collett 1879 and R. melanocephalus Andriashev & Chernova 2010 ) have such a reduced lower lobe, although in them the lower lobe is distinctly separate from the rest of the pectoral fin.

Comments. Owing to the small size and fragility of the specimen, it seemed unwise to try to dissect it to determine the characteristics of either the pectoral girdle or the stomach and internal organs. The lack of segmented fin rays in this specimen is unlikely to be the result of ontogenetic change. P. anarthractae , also a small species (to about 70 mm SL), displays no difference in segmentation between specimens from 25 mm SL to almost three times as long. In addition, the two-rayed lower pectoral fin lobe of P. amerismos is distinctive.

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1989

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Stein andriashevi Paraliparis 11401. – 1

. 21 LACM FIGURE girdle,