Morphology and distribution of the freshwater mussel Diplodon granosus, a rare and poorly understood species

Diplodon granosus was one of the first freshwater mussels to be described for South America. However, the status of the species was confusing for a long time, receiving different taxonomic treatments. In this paper, we redescribe the shell, with new data on the soft parts and information on the distribution and conservation of D. granosus, a rarely recorded species. The shell is thin, not inflated; the macrosculpture is composed only by granules that cover the whole shell, not forming bars; the microsculpture comprises short spikes. In the soft parts we highlight the few, weak and irregularly distributed lamellar connections of the outer demibranch and some features of the stomach, such as the distally enlarged minor typhlosole. There are records of D. granosus over a large area of South America, from Guiana to Argentina. However, most of these records are related to other species and the distribution of D. granosus is restricted to the north of South America in the basins of the Amazonas and Orinoco rivers, and coastal rivers in between. Despite this wide distribution, the species occurs in specific habitats, mainly streams (igarapés), resulting in an extremely fragmented occurrence. Thus, any disturbance to these habitats can threat this freshwater mussel. (AU)

Freshwater mussels from South America: state of the art of Unionida, specially Rhipidodontini / Bivalves de água doce da América do Sul: estado da arte de Unionida, especialmente Rhipidodontini

Abstract Unionida is the most diverse clade of freshwater bivalves. Among the groups occurring in South America, one with the highest number of species is Rhipidodontini (Hyriidae, Unionida, Paleoheterodonta, Bivalvia). However several issues remains on taxonomy and systematic of this group, leading to problems on species identification, description, as also as a limiting factor to other type of studies (e.g., ecology, conservation,…). In this paper is presented a synthesis of available knowledge about Diplodon Spix in Wagner, 1827 and Rhipidodonta Mörch, 1853 in South America, as a first step in order to a better understating of Rhipidodontini. The evaluation of different authors exposes the little agreement between them that resulted in a sort of divergent taxonomical opinions. Some comments on ecology, conservation and habitat preferences were made. This work can also encourage future research on taxonomy, systematic, ecology and conservation of freshwater mussels in South America.

Resumo Unionida é o clado mais diverso de bivalves de água doce. Entre os grupos que ocorrem na América do Sul, um dos com maior número de espécies é Rhipidodontini (Hyriidae, Unionida, Paleoheterodonta, Bivalvia). Porém, diversas questões taxonômicas e sistemáticas ainda incidem sob este grupo, levando a problemas de identificação de espécies, descrição, entre outros, como também tem atuado como limitador de outros tipos de estudos (e.g., ecologia, conservação,..). Neste trabalho é apresentada uma revisão do conhecimento acerca dos gêneros Diplodon Spix in Wagner, 1827 e Rhipidodonta Mörch, 1853 na América do Sul como um primeiro passo para a melhor compreensão de Rhipidodontini. Avaliando-se diferentes autores, se torna claro a pouca concordância entre eles, resultando em opiniões taxonômicas divergentes. São feitos também alguns comentários sobre ecologia, conservação e preferências ambientais. Este trabalho também deve encorajar futuros trabalhos sobre a taxonomia, sistemática, ecologia e conservação de bivalves de água na América do Sul.

Chave pictórica para identificação dos bivalves do baixo Rio Aripuanã, Amazonas, Brasil (Sphaeriidae, Hyriidae e Mycetopodidae) / Pictorial key for identification of bivalves of the lower River Aripuanã, Amazonas, Brazil, (Sphaeriidae, Hyriidae and Mycetopodidae)

A partir de moluscos bivalves coletados principalmente nos períodos de seca de 2004 e 2007, no curso inferior do Rio Aripuanã, afluente do Madeira na região amazônica, foi elaborada uma chave pictórica para identificação das espécies. Foram identificados 11 táxons, sendo dez até o nível específico.

Starting from freshwater mussels sampled mainly during low water seasons of 2004 and 2007, on the lower Aripunã River, a tributary from Madeira River, from the Amazon Basin, a pictorial key for the species identification is presented. Eleven taxa, ten to species level, were identified.