Paramisophria walteri a new Arietellidae (Copepoda, Calanoida) from Midway Island

A new species of the genus Paramisophria T. Scott 1897 (Copepoda: Calanoida) was collected from coastal waters off Midway Island. Paramisophria walteri sp. nov., along with Paramisophria variabilis, Paramisophria platysoma and Paramisophria bathyalis, are the only representatives of the genus sharing four armature elements on the third exopod article of the male left leg 5. The new species can be easily distinguished from P. variabilis by differences in the armature elements on third exopod article of the male left leg 5 (terminal spine pinnate, plus three subequal spines, compared with terminal spine naked, plus two subequal spines and one short process in P. variabilis). The new species can be easily distinguished from P. platysoma by its symmetrical prosome (prosome asymmetrical in P. platysoma), and the endopodal lobes of the female leg 5 each bearing one long plumose seta (setae are lacking in P. platysoma). Significant differences between the new species and P. bathyalis include the 4 + 1 armature elements of the maxillulary praecoxal arthrite (5 + 1 in P. bathyalis); and the third exopod article of the male right leg 5 with three distal stout spines, compared with one slender inner seta plus two thin subequal outer setae in P. bathyalis. Phylogenetic relationships within the genus Paramisophria are re-examined and discussed.