Description of Genesis vulcanoctopusi gen. et sp nov (Copepoda : Tisbidae)parasitic on a hydrothermal vent octopod and a reinterpretation of the life cycle of cholidyinid harpacticoids

Juveniles and adult females of Genesis vulcanoctopusi gen. et sp. nov. (Cop epoda: Harpacticoida) are described from the deepwater octopus Vulcanoctopu s hydrothermalis, collected from a hydrothermal vent in the East Pacific Ri se. The new genus is placed in the Tisbidae and is readily distinguishable from other Cholidyinae by the combination of body shape, structure of oral appendages and segmentation of legs 1-5. All stages were found embedded in the integument of the head and mantle of the cephalopod host, suggesting an endoparasitic copepodid phase. The generalized life cycle of cholidyinid h arpacticoids is reinterpreted in the light of this discovery. Aspects of pa rasitism and pathological effects of G. vulcanoctopusi on the octopod host are discussed.