How does the Taquari river influence in the Cladoceran assemblages in three oxbow lakes? / Qual a influência do rio Taquari nas assembleias de Cladocera em três lagoas marginais?

This study examined the cladoceran assemblages in three oxbow lakes of the Taquari River floodplain, near the transition between the plateau and the plain. We sought to answer the following questions: does the Taquari River function as a geographical barrier or dispersal corridor for Cladocera? Can different degrees of connection induce different structures in the assemblages in each lake? Cladocerans and limnological variables were sampled every other month for one year. Forty-one species were recorded, four of which were common to all the lakes. Our results indicated that the different degrees of connection between the river and the oxbow lakes favoured environmental heterogeneity and diversification in the cladoceran assemblages. The greatest dissimilarity between the two lakes connected with the river indicates that in this case the river functions better as a barrier than a dispersal corridor.

Assembleias de cladóceros foram avaliadas em três lagoas marginais ao rio Taquari, próximo à transição entre planalto e planície. As seguintes questões foram investigadas: O rio Taquari funciona como barreira ou corredor de dispersão para Cladocera? O grau de conexão induz a diferentes estruturas nas assembleias de cada lagoa? Cladocera e variáveis limnológicas foram amostradas a cada dois dias durante um ano. Foram registradas 41 espécies, apenas 4 comuns em todas as lagoas. Nossos resultados apontam que diferentes graus de conexão entre rio e lagoas favorecem a heterogeneidade ambiental e a diversificação das assembleias de cladóceros. A maior dissimilaridade entre as duas lagoas conectadas com o rio indica que, neste caso, o rio funciona melhor como barreira do que como corredor de dispersão.

Macrothrix flabelligera, a newly-recorded Cladocera Macrothricidae in Brazilian freshwaters

Este artigo apresenta breve caracterização de Macrothrix flabelligera Smirnov, 1992 (Cladocera, Macrothricidae), após o recente registro dessa espécie no Brasil. Os aspectos gerais e os detalhes morfológicos do corpo das fêmeas partenogenéticas e efipiais, bem como dos machos, são descritos e ilustrados.

Cladocera Chydoridae of high altitude water bodies (Serra da Mantiqueira), in Brazil

The diversity of species of Cladocera, Chydoridae in the water bodies belonging to the water management unity of Serra da Mantiqueira, was studied inside the BIOTA/FAPESP Program. A total of 21 water bodies were analyzed and the sampling was carried out between 9th and 11th September, 1999. Horizontal and vertical net hauls were taken at littoral and limnetic region in each lake. Most water bodies in Serra da Mantiqueira unity are small, shallow, and densely colonized by macrophytes. Most species of Cladocera found belong to the Chydoridae family, being typical inhabitants of the littoral zone, living associated with macrophytes. A total of 12 species were found, 9 of the subfamily Aloninae and 3 Chydorinae. In more than half of the water bodies the relative abundance of chydorids reached 100 percent, and they were dominant in most of the others, with few exceptions. Alona rustica was the most frequent species, occurring in 62 percent of the water bodies. The results evidenced the importance of the littoral zone as propitious habitats for the species of Chydoridae and contributing significantly to the diversity of Cladocera as a whole