Possible hybridization of Brazilian planorbid snails and its importance in population dynamics

Abstract

This study focuses on the possibility of experimental hybridization among host snail species forIntraspecific and interspecific crossbreedings among host species have been described in the literature since the 1950s. Paraense (1955) and Paraense and Deslandes (1955) performed experiments based on intra-and interspecific crossbreeding. The former, intraspecific crossbreeding, aimed to establish these species' reproductive preferences, while the latter focused on the possibility of interspecific crossbreeding between B. glabrata and B. tenagophila, which were located 315 km from each other. The authors observed in these respective experiments that cross-fecundation is preferential and that the crossbreeding proposed was not viable, reporting reproductive isolation between the species of Biomphalaria studied. Interspecific crossbreedings between geographically isolated species were described by Barbosa: B. alexandrina (Cairo, Egypt) and B. glabrata (Recife, Pernambuco, Brazil) in 1956; B. straminea (Pernambuco, Brazil) and B. peregrina (Ecuador); B. tenagophila (São Paulo, Brazil) and B. peregrina (Ecuador) (Barbosa et al. 1958). Formation of fertile hybrid offspring was observed in these crossbreedings. The same author in 1964 commented on the natural hybridization of B. glabrata and B. tenagophila, reporting intermediate forms, explained by the proximity of the respective populations. Later on, Barbosa (1973) observed this process of natural hybridization in the Northeast of Brazil, between B. glabrata and B. straminea. Breeding sites previously colonized exclusively by B. glabrata were replaced by B. straminea over the course of three years. During the process of competitive exclusion, mixed forms were found, possibly resulting from interspecific crossbreeding. Such intermediate forms were no longer found during later field studies, showing their inability to persist in nature. This study's objectives were to observe the possibility of experimental hybridization between host species for Schistosoma mansoni in Brazil and to study the reproductive capacity and subsequent morphological characterization of the hybrid forms.

Evolutionary history and phylogeography of the schistosome-vector freshwater snail Biomphalaria glabrata based on nuclear and mitochondrial DNA sequences

“…Note that VE6b and VE13a are also genetically closer to BR1 individuals than to other Venezuelan individuals, when using microsatellite (nuclear) markers (Mavarez et al, 2002b). A possible explanation to such a nuclear-mitochondrial conflict involves interspecific (or inter-clade) mitochondrial gene flow via hybridisation, which is common in animals (Barton and Hewitt, 1985), and has been documented in Biomphalaria (Mello-Silva et al, 1998;Kristensen et al, 1999). However it is also possible that the 16S gene tree is poorly resolved, due to a lower evolutionary rate.…”

Field Application of NIR Spectroscopy for the Discrimination of the Biomphalaria Species That Are Intermediate Hosts of Schistosoma mansoni in Brazil

“…The identification errors found between B. glabrata and B. tenagophila indicate that the chemical phenotypes of the two species are the most similar. This may be related to the morphological and biological similarities of these two species, and their possible potential for hybridization (9,23). However, Vidigal et al (24) found that B. glabrata and B. tenagophila belonged to distinct clades in a phylogenetic analysis of the ITS2 molecular marker, which indicates that there is a considerable genetic distance between the two species.…”

Hybridism between Biomphalaria cousini and Biomphalaria amazonica and its susceptibility to Schistosoma mansoni

“…Crosses between Biomphalaria species that produced fertile hybrids have been reported. Examples include crosses between B. alexandrina and B. glabrata (Barbosa et al 1956): B. straminea and B. peregrine, B. tenagophila and B. peregrina (Barbosa et al 1958) and B. glabrata and B. tenagophila (Mello-Silva et al 1998). Barbosa (1964) (66) 21 (42) 43 (86) 10 ( this process of competitive exclusion were mixed forms found, possibly as a result of crosses between these species.…”

“…Thus, this study confirms that these two species produce hybrids. Mello-Silva et al (1998) commented that the results of fertility and fecundity tests of fertile hybrids revealed that the F2 generation was not as efficient as the F1, involving the formation of normal, vigorous and fertile F1 generation hybrids, but a weak F2 generation with the presence of some sterile individuals. However, further studies are necessary to better understand the biology of these hybrids.…”

“…Crosses between B. glabrata and B. tenagophila were not feasible reporting the reproductive isolation of these species (Paraense & Deslandes 1955). Nevertheless, crosses between Biomphalaria species that produce fertile hybrids have been reported (Barbosa et al 1956, 1958, Mello-Silva et al 1998.…”