Pseudomesochra T.Scott 1902 as a member of the ParanannopidaePor 1986 (Copepoda, Harpacticoida) with a description of three new species

Abstract

Three new species of the genusPseudomesochraT. Scott 1902 from the Antarctic Weddell Sea and the Arctic Laptev Sea are described. The male CV stage specimen ofPseudomesochra meridianensis s.n. found in the Weddell Sea is regarded as the first true record of a male ofPseudomesochra. It is shown that the genus has to be removed from the family DiosaccidaeSars 1906 and instead has affinities with the ParanannopidaePor 1986. The Paranannopidae includingPseudomesochra share a Mxp with only 2 syncoxal and 1 basal seta, a deeply incised anal somite with a pseudoperculum instead of a well developed anal operculum, a lost or vestigial caudal seta I, a similar structure of the female genital field and a segmental apophysis on the male P3 enp2, a non-prehensile and 2-segmented Plenp, only 4 endopodal setae and a spine-like pinnate seta on the proximal syncoxal endite of the Mx. The latter 3 characters seem to separate the Parannopidae from closely related taxa of the thalestrid subfamilies Pseudotachidiinae sensuLang 1936 and DonsiellinaeHicks 1988. Showing several autapomorphies,Pseudomesochra has an isolated position within the Paranannopidae, therefore a new subfamily Pseudomesochrinae is proposed containing only the type genusPseudomesochra. An amended key to the species is given.