ON TWO CUMACEANS FROM THE SOUTH-WEST ATLANTIC: DIASTYLIS N. SP. AND DIASTYLIS HAMMONIAE ZIMMER, 1902

NATALIA A. ALBERICO; DANIEL ROCCATAGLIATA

Bahía Blanca

Jornada; VII Jornadas Nacionales de Ciencias del Mar; 2009

IADO

Abstract In order to improve our knowledge on the diastylids fauna from the South-West Atlantic, a new species of the genus Diastylis is fully described and a partial description of the adult male of Diastylis hammoniae Zimmer, 1902 is presented. Diastylis n. sp. has been collected in large numbers from off São Paulo State (Brazil) to northern Patagonia (Argentina), whereas D. hammoniae has a Magellan distribution. The samples examined in this study were collected during the surveys carried out by the R/V "Aldebarán", R/V "Eduardo Holmberg" and R/V "Victor Hensen", among others, and also by individual researchers. The new species of Diastylis herein reported can be distinguished from the other members of the genus by the following combination of characters: (1) the integument is strongly calcified, (2) the sides of the carapace show a large curved tooth (horn) and three longitudinal rows of conspicuous tubercles, (3) the uropod endopod consists of two articles. Until now it was considered that Diastylis hammoniae lacked reduced exopods on the third and fourth pereopods, but a careful examination of the type specimens revealed to us that these exopods were overlooked by former authors. Thus, the absence of such exopods, the most important criterion used until now to distinguish D. hammoniae from the closely related South-West Atlantic species Diastylis manca (Sars 1873) and Leptostylis (?) mancoides Bacescu-Mester, 1967, is no longer valid. Moreover, the descriptions of these three diastylids are inappropriate and based on different stages. Two or all three of these species could be conspecific; however, the lack of a large number of specimens prevents us from arriving at a firm conclusion about their taxonomic status. Key words: Diastylis, Cumacea, South-West Atlantic. This research was partially supported by the Universidad de Buenos Aires (UBACyT X190) and the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). This research was partially supported by the Universidad de Buenos Aires (UBACyT X190) and the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). This research was partially supported by the Universidad de Buenos Aires (UBACyT X190) and the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).