Meiobenthic Harpacticoida (Crustacea, Copepoda) from the Deep Sea off North Carolina I. The Genera Hemimesochra Sars, Paranannopus Lang, and Cylindronannopus n. g.
This first paper on the deep-sea harpacticoids off North Carolina revises and gives keys to two known genera, Hemimesochra Sars and Paranannopus Lang. A new species is described in each genus. H. trisetosa n. sp. differs from all the previously known species by having three setae on the A2 exopod and swimming leg setation. P. atlanticus n. sp. and P. philistinus Por are the only known Paranannopus to exhibit 3-segmented A2 exopods and 1-segmented P2-P4 endopods. The two species differ in number of antennal segments and swimming leg setation. A new genus, Cylindronannopus n. g., distinct in its body form and lacking the usual sexually dimorphic characters is also described. Possible reasons for this unique dimorphism include a new evolutionary line within the Harpacticoida, intersexuality and morphologically similar females and sub-adult males as known with some amphipods. The low number of males known from the deep-sea literature is discussed and may be a function of misidentifying males as females.