Résumé
Biogeographic and taxonomic knowledge on planktonic mollusks, specifically on Pterotracheoidea (also known as heteropods or sea elephants) in tropical oceans, is still incomplete. In this paper we report the first record of the heteropod Firoloida desmarestia Lesueur (1817) on waters off the Northeast Brazilian continental slope and Fernando de Noronha Archipelago and extend its geographic distribution in the tropical Atlantic. We provide new detailed digital image and descriptions of this highly fragile and transparent gelatinous species. Samples were taken in the context of the ‘ABRACOS’ (Acoustic along the Brazilian Coast) project using bongo nets. Out of 96 samples analyzed, six specimens were recorded in five samples, three at Fernando de Noronha, and three off the Northeast Brazilian coast. The present study extends the range of distribution of F. desmarestia to 3°S-9°Sin the western the Tropical Atlantic and highlights the importance of detailed studies on large-sized gelatinous plankton biodiversity in tropical oceans. Keywords: Tropical oceanic islands, Continental slope, zooplankton, heteropods, Pterotracheidae.