Two new bathyal species of Pseudotachidius (Copepoda: Harpacticoida) from the Beaufort Sea (Alaska, U.S.A.)

During the summer of 1977, the Oregon State University Benthic Group participated in a USCGC GLACIER cruise off the northeastern coast of Alaska, U.S.A. Two new species of Harpacticoida (Copepoda) were found from several of the bathyal stations occupied. Pseudotachidius brevisetosus sp. nov. occurred in 15 samples from 4 stations. Pseudotachidius bipartitus sp. nov. co-occurred with P. brevisetosus in 5 samples from 3 stations. The areal extent was not great, hut the depth ranged from 659-1144 m for the 3 stations where both species occurred. A single P. brevisetosus female was found at the fourth station, where the depth was 403 m. Pseudotachidius bipartitus is .most similar to Pseudotachidius vikingus Drzycimski, but differs from it and other members of the genus in that the endopod of the first leg is 2-segmented. Pseudotachidius brevisetosus is most nearly related to Pseudotachidius coronatus T. Scott, but differs from it in the setal arrangement of the fourth and fifth legs, and most importantly in the transformed endoped of the male second legs. The setal arrangements ofP. coronatus and Pseudotachidius similis T. Scott are in question, due to differing interpretations of the original descriptions. A re- examination of the literature is discussed so that the relationships of the new species are clearly defined. All figures were made with the aid of a camera lucida. The nomenclature and descriptive terminology are adopted from Lang (1948, 1965) and Coull (1977). The following abbreviations are used throughout the text: R = rostrum, A 1 -- antennule, A 2 = antennae, Md = mandible, Mxl = maxillula, Mx = maxilla, Mxp = maxilliped, P1-P6 = legs 1-6, CR = caudal rami, GF = genital field, Bend. = baseoendopodite. Body length measurements are from the base of the R to the base of the CR, excluding both. CR L/W (=length to width ratio) is measured from the inner proximal edge to the inner distal edge for length, and at the widest points for width.