Biomphalaria occidentalis sp.n. from South America (Mollusca basommatophora pulmonata)

Abstract

A new species of South American planorbid snail, Biomphalaria occidentalis, is described. It is indistinguishable from B. tenagophila (Orbigny, 1835), by the characteristics of the shell and of most organs of the genital system. In B. tenagophila there is a pouch on the ventral wall of the vagina (Fig. 4A, vp), absent in B. occidentalis (Fig. 3A), and on the ventral wall of the vagina (Fig. 4A, vp), absent in B. occidentalis (Fig. 3A), and the prepuce is much wider than the penial sheath, its width increasing distalward (Fig. 4, ps,pp), whereas in B. occidentalis the prepuce is wider than the penial sheath but keeps about the same width all along (Fig.3, ps, pp). The two species are biologically separate by absolute reproductive isolation. The geographical distribution of B. occidentalis is shown in Fig. 14. So far it has been found in the Brazilian states of Acre, Amazonas (?), Mato Grosso, Mato Grosso do Sul and Paraná, and in Paraguay. Its type-locality is Campo Grande, state of Mato Grosso do sul, where it was collected from several biotopes related to affluents of the Aquiduana river, chiefly Córrego Prosa and Córrego Ceroula. Specimens were deposited in the following malacological collections: Instituto Oswaldo Cruz, Rio de Janeiro; Academy of Natural Sciences, Philadelphia; Museum of Zoology, University of Michigan; and British Museum (Natural History).<br>É descrita uma nova espécie de molusco planorbídeo sul-americano, Biomphalaria occidentalis, indistinguível da b. tenagophila (Orbigny, 1835) pelos caracteres da concha e da maioria dos órgãos do sistema genital. Na B. tenagophila existe uma bolsa na parede ventral da vagina (Fig. 4A, vp), ausente na B. occidentalis (Fig. 3A), e o prepúcio é muito mais grosso que a bainha do pênis, aumentando de largura na direção distal (Fig.4, ps, pp), ao passo que na B. occidentalis o prepúcio é mais grosso que a bainha do pênis porém seu diâmetro pouco se altera em toda sua extensão (Fig.3, ps, pp). As duas espécies são biologicamente separadas por isolamento reprodutivo absoluto. A Fig. 14 mostra a distribuição geográfica da B. occidentalis, que até agora foi encontrada nos Estados brasileiros do Acre, Amazonas (?), Mato Grosso, Mato Grosso do Sul e Paraná, e no Paraguai. Sua localidade-tipo é Campo Grande, Estado de Mato Grosso do Sul, onde foi coletada em vários biótopos relacionados e afluentes do rio Aquidauana, principalemente nos córregos Prosa e Ceroula. Foram depositados exemplares nas seguintes coleç~eos malacológicas: Instituto Oswaldo Cruz, Rio de Janeiro; Academy of Natural Sciences, Philadelphia; Museum of Zoology, University of Michigan; British Museum (Natural History)

The schistosome vectors in the Americas

“…Realizing later that the name confusus had been given by Rochebrune (1882) to an Oriental planorbid, he changed it to immunis (Lutz 1923) for obvious reason. Now it is known that P. immunis is a synonym of B. tenagophila (see Paraense 1961b), which ceased being immune to transmit at least a race of the schistosome (Paraense & Corrêa 1963, 1981.…”

“…Till then the consensus of the specialists was that B. tenagophila ranged westward from São Paulo to Paraguay through the state of Mato Grosso do Sul. Coincidentally I was then collecting snails in Mato Grosso do Sul, verifying that the so-called tenagophila was really a new species -B. occidentalis -reproductively isolated from B. tenagophila (Paraense 1981) and insusceptible to infection with the SJ race of S. mansoni (Paraense & Corrêa 1982). I extended the survey to the westernmost area of São Paulo, identifying B. occidentalis in five localities.…”

“…Outside South America (Figs 1, 2) B. straminea has been recorded in Martinique (Paraense 1970), Grenada (Richards 1973), Costa Rica (Paraense et al 1981), Dominican Republic (Sodeman Jr et al 1985), Dominica (Noblet & Damian 1991) and Guadeloupe (Pointier et al 1993).…”

Biomphalaria molluscs (Gastropoda: Planorbidae) in Rio Grande do Sul, Brazil

“…The molluscs collected were sent to our laboratory to obtain their F1 progeny. Morphological and molecular identification of Biomphalaria was undertaken according to Paraense (1975Paraense ( , 1981Paraense ( , 1984 and Vidigal et al (2000) (Fig. 1).…”

Molecular identification of similar species of the genus Biomphalaria (Mollusca: Planorbidae) determined by a polymerase chain reaction-restriction fragment length polymorphism

“…It is caused by Schistosoma mansoni (Sambon 1907), the intermediate hosts of which are freshwater snails of the genus Biomphalaria. Ten species and one subspecies of this genus are known in Brazil (Paraense 1975(Paraense , 1981(Paraense , 1984(Paraense , 1988, of which only B. glabrata, B. tenagophila e B. straminea have been found with natural infections. Two other species (B. amazonica and B. peregrina), can also be infected experimentally and are considered to be potential hosts of the trematode (Corrêa & Paraense 1971, Paraense 1973.…”