Morphology of the deep-sea copepod Bobkabata kabatabobbus (Lernaeosoleidae: Poecilostomatoida) and amended diagnosis of Lernaeosoleidae.

New morphological information on the deep-sea parasitic copepod Bobkabata kabatabobbus Hogans and Benz, 1990 (Lernaeosoleidae: Poecilostomatoida) is provided based on 2 newly discovered, complete specimens collected from a pallid sculpin, Cottunculus thomsoni (Gunther, 1882), captured in water 1,463 m deep in Welker Canyon off Rhode Island (western North Atlantic). The first antennae of both specimens were tiny, indistinctly segmented, and armed with spiniform setae. Terminal segments of the second antennae were robust hooks and were impossible to disengage from the host without severing them from their basal sockets. A simple orifice without any associated appendages may have represented the mouth. Both specimens were transformed adult females and each was embedded in the flesh of their scaleless host up to where the pregenital trunk began to broaden into its characteristic horseshoe shape. Whereas each copepod's bulbous cephalothorax appeared to be the primary attachment device, the powerfully hooked second antennae seemed positioned to facilitate the application of the presumed mouth to the host. A revised family diagnosis for Lernaeosoleidae Hogans and Benz, 1990 is provided that primarily differentiates Lernaeosoleidae from the closely allied Chondracanthidae H. Milne-Edwards, 1840 and other poecilostomatoids based on the absence of mandibles, first and second maxillae, maxillipeds, and thoracic legs 1-4 in lernaeosoleids.