A new species of Nannastacidae, Styloptocuma darwini n. sp., is described from three hydrothermal sites in the back-arc basins of the southwestern Pacific: White Lady (North Fiji Basin), Hine Hina and Tu’i Malila (Lau Basin). Styloptocuma darwini n. sp. resembles S. pleonserratum Mühlenhardt-Siegel, 2005, from the Angola Basin and S. spinosum Petrescu, 2006, from the southeastern Australian slope, but differs from both by having a serrate antennal notch margin and transverse rows of spines on pereonites. The new species is associated with hydrothermal vent assemblages known from the southwestern Pacific back-arc basins. Affiliation to known families tends to indicate that the modern vent cumacean fauna may have originated from the surrounding deep-sea environment but also from the shallow-water vents or cold seeps, which acted as refugia during past global anoxic events in the deep sea.
Crustacea, Cumacea, Nannastacidae, Styloptocuma, deep-sea, hydrothermal vents, back-arc basins, southwestern Pacific, new species.