First South American Phreatogammarid, with Comments on the Arrangement of Coxal and Sternal Gills, and on the Biramous Condition of the Seventh Pereiopod in Amphipods

Abstract

Abstract Ruffia patagonica, a new genus and species of phreatogammarid amphipod, is described from a coastal cave on Madre de Dios Island (Chilean Patagonia). This is the first record of the family outside continental waters of New Zealand and New Caledonia. The new taxon displays some of the more distinctive features of the family, such as gnathopods with the palm margin lined with numerous unicuspid robust setae and with a denticulated inner margin of the dactylus; fifth pereiopod clearly smaller than pereiopod six and seven; “coxal gill” ( = exopod) absent from the seventh pereiopod; oostegites broadened; urosomites with posterodorsal robust setae; and third uropod equiramous with an elongated peduncle and with unsegmented cylindrical rami, the latter provided with numerous robust setae. In addition, the sternites of all pereionites, pleonites, and urosomites show a portion of integument delimited by hyaline frill that is presumably osmoregulatory in function, and is equivalent to the pair of sternal ...