Taxonomic Review of the Hydrothermal Vent Shrimp Genera Rimicaris Williams & Rona and Chorocaris Martin & Hessler (Crustacea: Decapoda: Caridea: Alvinocarididae)

A taxonomic review of the two genera of the family Alvinocarididae (Decapoda: Caridea), RimicarisWilliams and Rona, 1986 and ChorocarisMartin and Hessler 1990, is presented based on study of type materials and/or supplemental material from recent collections. Two species of Rimicaris, R. exoculataWilliams and Rona 1986 and R. kaireiWatabe and Hashimoto 2002, and three species of Chorocaris, C. chaceiWilliams and Rona 1986, C. vandoveraeMartin and Hessler 1990, and C. paulexaMartin and Shank 2005, are recognized. All species are exclusively associated with deep-water hydrothermal community. Close relationship between the two genera is confirmed by morphological characters, but the monophyly of Chorocaris is not corroborated. An examination of a good series of material from the Mid-Atlantic Ridge shows that juveniles of Rimicaris exoculata can be arranged in four sequential ontogenetic stages based on morphology. A dramatic change occurs at the size of 7.0 to 9.0 mm in the carapace length. The synonymies of Iorania concordia Vereshchaka 1996 and Rimicaris aurantiacaMartin, Signorovitch & Patel 1997 with Rimicaris exoculata, indicated from molecular evidence by Shank et al. (1998), are confirmed. Morphological differences between R. exoculata and R. kairei and those among C. chacei, C. vandoverae, and C. paulexa, are reassessed.