Abstract
A new species of the amphipod family Ampithoidae Stebbing, 1899 is described from the northeastern Brazilian waters. The new described taxon is grouped in the genus Cymadusa Savigny, 1816, since it presents all the diagnostic characteristics of the genus. The examined material was collected by scuba diving in the Rocas Atoll, off Rio Grande do Norte state coast, Camamu Bay and Todos os Santos Bay, Bahia state. The new species described here is close to C. filosa Savigny, 1816, type species of the genus, by presenting anterior margin of gnathopod 1 poorly setose, male gnathopod 2 densely setose, with palmar corner not defined by a spine and dactylus subequal in length to palm, being considered part of the C. filosa complex. Among the species of this complex, the one which most resembles to the new taxon is C. imbroglio Rabindranath, 1972, which is distinguished by the absence of both the trapezoid process in the palm and spine at the palmar corner in the gnathopod 2. This is the second species of the genus Cymadusa recorded from Brazilian waters.
Highlights
The Amphipoda belong to the Superorder Peracarida, a crustacean group with direct development, incubating the eggs in a marsupium ventral to the thorax formed from thin plates called oostegites
We describe a new species of Cymadusa, the second one recorded from Brazilian waters, and the first one known from the Rocas Atoll, as for the northeastern Brazilian coast
Morphological differences among the species grouped in the C. filosa complex, including the new species described in this paper, are restricted to few characters, such as number of segments in the accessory flagellum of antenna 1, setation on antenna 2 and gnathopods 1 and 2, length and shape of merus and carpus of gnathopod 1, presence of a spine defining the palmar corner of gnathopod 2, and length ratio between dactylus and palm of gnathopod 2 (Tab. 1)
Summary
The Amphipoda belong to the Superorder Peracarida, a crustacean group with direct development, incubating the eggs in a marsupium ventral to the thorax formed from thin plates called oostegites. Brazil, grouped in three genera: Ampithoe Leach, 1814, Cymadusa Savigny, 1816 and Sunampithoe Bate, 1857 (Wakabara and Serejo, 1998; Serejo and Licínio, 2002). It shows the paucity of taxonomic studies about the group in Brazil. As concerns the genus Cymadusa, only C. filosa Savigny, 1816 (type species of the genus) is recorded from Brazilian waters. Another species, Grubia sardenta Oliveira, 1953, described with material from Guanabara Bay, 1 m depth, was synonymized to C. filosa by Peart (2004), despite some morphological differences between the two species. It is still necessary to analyze materials of collections from this species type locality, to confirm or not the validity of the species described by Oliveira
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