Phylogeny, morphology, and haplotypic distribution of Biomphalaria straminea populations from the five geographic regions of Brazil.

Biomphalaria straminea is one of the three snails that act as the intermediate hosts of Schistosoma mansoni and is responsible for maintaining high rates of schistosomiasis in some areas of northeastern Brazil. The principal morphological characteristic of B. straminea is the marked vaginal wrinkling, although it is also present in congeneric species, a group known as the B. straminea complex. Based on the morphological and molecular analyses, we investigated the intraspecific variation of B. straminea. The specimens were obtained from 10 sites in Brazil, and the shells were analyzed, as well as 16 morphological structures of the reproductive system. The COI and ITS2 sequences were used for phylogenetic analysis, genetic divergence, and haplotype network (COI). We observed a large intraspecific variation in the morphological structures examined. The genetic divergence also demonstrated significant intraspecific variability in B. straminea: 0-3% in ITS2 sequences, and 0-6% in COI sequences. Analysis of the distribution of COI haplotypes recovered 16 haplotypes and haplotype diversity of 0.9088. These results indicate phenotypic variability that is not constrained to a locality or strictly controlled genetically by B. straminea, which may have driven a misidentified of these species.