A New Species of Nototheniid (Perciformes: Notothenioidei) Fish from Mcmurdo Sound, Antarctica

A new species of nototheniid fish, Cryothenia amphitreta, is described from a single gravid female collected in mid-November 2004 by divers in McMurdo Sound in the Ross Sea region of Antarctica. The new species closely resembles the only known congener, C. peninsulae, collected off the west coast of the Antarctic Peninsula, but differs substantially in pelvic-fin length (13.4 vs. 19.3–24.4% SL), total vertebrae (57 vs. 50–53), body size at maturity (261 vs. 100–144 mm), and interorbital-pit morphology. The neutrally-buoyant C. amphitreta is characterized by a wide, well-defined interorbital pit divided by a raised medial ridge, scales anterior to this depression in the interorbital region, and a dark pigmentation of the mouth, gill, and body cavity linings. This species is protected against freezing by high levels of antifreeze proteins in its body fluids. Phylogenetic reconstruction using the mitochondrial NADH dehydrogenase subunit 2 (mtND2) suggests that C. amphitreta falls within the current designation of the nototheniid subfamily Trematominae.

Figure 1

Cryothenia amphitreta, holotype, USNM 385901, gravid female, 261 mm SL, collected by divers at approx. 20 m depth in McMurdo Sound, Antarctica (77°51.033′S, 166°39.759′E).

Figure 2

Arrangement of the pores (shaded grey) of the supraorbital sensory canals, interorbital pit, and head scales in (A) Cryothenia amphitreta, holotype 261 mm SL and (B) Cryothenia peninsulae, based on NYSM 11457 paratype 112 mm SL.

For C. peninsulae, the interorbital pit is surrounded by a depressed area (stippled). Figures are not drawn to the same scale. N = nostril, SC = scales, IP = interorbital pit.

Figure 3

Phylogenetic analysis of mtND2 gene sequence used to gain insight into the evolutionary relationships between Cryothenia and other members of the Nototheniidae.

(A) Phylogram of the maximum-likelihood tree reconstruction; scale bar indicates 10% sequence divergence. (B) Cladogram of the maximum parsimony consensus tree with bootstrap values from 2000 pseudoreplicates. The tree topology within the Trematominae is not particularly well supported by the data. The basal nototheniid D. mawsoni was used as the outgroup. A = Aethotaxis, D = Dissostichus, N = Notothenia, Pa = Pagothenia, Pl = Pleuragramma, T = Trematomus; subfamilies in brackets, TR = Trematominae, NO = Nototheniinae, PL = Pleuragramminae.

Contributor Notes

DEPARTMENT OF ANIMAL BIOLOGY, UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN, 505 S. GOODWIN, URBANA, ILLINOIS 61801.

Received: 16 Feb 2006

Accepted: 05 Jun 2006