Leucon (Crymoleucon) rossi, a new species (Crustacea: Cumacea: Leuconidae) from the shelf waters of the Ross Sea (Antarctica), with a key to the genus Leucon south of 60S

A new leuconid cumacean, Leucon (Crymoleucon) rossi n. sp., is described from depths of 84 to 458 m in the Ross Sea off the Victoria Land coast. Leucon rossi n. sp. is distinguished from other members of the genus by a combination of characters including 1) a blunt, horizontally directed pseudorostrum without a distinctly protruding siphon; 2) strongly developed antennal notch; 3) entire dorsomedian margin of carapace appearing serrate, armed with 14 to 19 anteriorly curved spines in female (up to 21 in subadult males); 4) a small, but distinct, spine behind the frontal lobe; and 5) the uropodal peduncle slightly shorter than the exopod. After Leucon antarcticus Zimmer, 1907, L. rossi was the second most frequently occurring cumacean in the samples collected off Victoria Land. Statistical analyses showed significant differences in the proportion of carapace length and height of adult (all incubating in the present study) and immature females compared to immature males; no adult males were available for study.