A NEW SPECIES OF CHASMATOPONTIUS (COPEPODA, SIPHONOSTOMATOIDA, DIRIVULTIDAE) FROM A HYDROTHERMAL VENT FIELD IN THE TOFUA ARC, SOUTHWESTERN PACIFIC OCEAN

Abstract

A new species of siphonostomatoid copepod is described from a hydrothermal vent in the Tofua Arc of the southwestern Pacific at a depth of 1018 m. Chasmatopontius inflatus sp. nov. (Copepoda, Siphonostomatoida, Dirivultidae) is defined and illustrated from specimens isolated from washings of invertebrates including gastropods, bivalves, and crustaceans collected from a hydrothermal vent field. A brief description of its habitat is presented. This new species can be distinguished from C. thescalus, the only known congener, by the greatly expanded mediodistal seta of the caudal ramus in the female, the three-segmented endopod of the female maxilliped, the smaller female body, not exceeding 0.9 mm in length, and the unique shape of the female genital double-somite.