Espécies de Rhipidodontini das bacias do alto rio Paraná, rio São Francisco e rios costeiros do Atlântico Leste, Norte e Nordeste (Bivalvia: Unionoida: Hyriidae)

Abstract

Rhipidodontini (Rhipidodonta Mörch, 1853 + Diplodon Spix in Wagner, 1827) is a tribe of freshwater bivalves with a complicated taxonomy, mainly due to the poor original descriptions, sometimes without illustrations, thereby a group needing a careful revision. The lack of information created a great variation in species considered valid by deferent authors, complicating the study of other aspects like distribution and biology. Therefore, were proposed in this study the taxonomic revision of Rhipidodontini in watersheds of Paraná River, São Francisco River and Coastal Atlantic rivers of East, North and Northeast. In order to achieve this goal museum collections were visited in Brazil and in other countries. Fields surveys were done in several localities to obtain fresh specimens to describe soft parts and glochidium. The information obtained added to information available in the literature were used to present and overview about distribution and conservation of the species. The main shell characteristics were employed to prepare an identification key to aid species differentiation. A morphometric analysis was used to distinguish species based on shell measurements. Diplodon and Rhipidodonta were recognized as valid genus included in tribe Rhipidodontini. Inside Diplodon were identified six species in the surveyed watersheds: Diplodon ellipticus Spix in Wagner, 1827; Diplodon fontainianus (d Orbigny, 1835); Diplodon jacksoni Marshall, 1928; Diplodon multistriatus (Lea, 1831); Diplodon paulista (Ihering, 1893) and Diplodon rhombeus Spix in Wagner, 1827. Despite Diplodon granosus (Bruguière, 1792) has extensive records in the studied region, this species was restricted to Amazonian region in our evaluation. In the genus Rhipidodonta were recognized only one species Rhipidodonta garbei (Ihering, 1910). Among these species, there are some traditionally accepted as valid (e.g. D. ellipticus e D. granosus), however other were revalidated and redefined based on analysis of type material, soft parts and glochidium (e.g. D. jacksoni e R. garbei). It was impossible to choose only one morphologic characteristic to discriminate the species, but details of gills, stomach, shell outline and umbonal sculpture were among the most important. The genera of Rhipidodontini were separate using attributes of glochidium (e.g. gloquidial hook, protuberance and shape of glochidium) and gills (e.g. gills shape and lamellar connections). The identification key based on shell characteristics helped to distinguish the species of Rhipidodontini. The morphometric analysis was considered a useful tool to separate the species, supporting the previous identification. The evaluation presented here should be expanded to other South American hydrographic catchments for determining the real diversity of these freshwater mussels