Biomphalaria Tenagophila Guaibensis ssp. n. from Southern Brazil and Uruguay (pulmonata: Planorbidae). I. Morphology

Abstract

A new subspecies of planorbid snail, biomphalaria tenagophila guaibensis, is described. It has been found along the coastal belt of the Brazilian state of rio grande do Sul and the middle part of Uruguay, from Porto Alegre to Mercedes. It differs from the nominate subspecies, Biomphalaria tenagophila tenagophila, in the appearance of the penial complex (prepuce longer and proportionally slenderer in B. t. guaibensis, shorter and proportionally stouter in b. t. tenagophila), in the ratio between the lengths of the penial sheath and the prepuce, in the ratio between the lengths of the uterine complex and the penial complex, and in a coefficient of difference of 2.44 for the ratio between the penis sheath and prepuce and of 2.02 for the ratio between the uterine complex and penial complex. The shell and the other organs of the genital system are similar in both subspecies. B. t. guaibensis is very similar to Biomphalaria occidentalis Paraense, 1981, but is readily separated from it by the presence of a vaginal pouch, which is lacking in the latter, besides showing highly significant difference in the penis sheath: prepuce and uterine complex: penial complex ratios. Crossbreeding experiments which lend additional support to the recognition of B. t. guaibensis as a subspecies will be reported elsewhere.<br>É descrita uma nova subespécie de molusco planorbídeo, Biomphalaria tenagophila guaibensis, que tem sido encontrada ao longo da faixa costeira do Estado do Rio Grande do Sul e da parte média do Uruguai, de Porto Alegre a Mercedes. Distingue-se da espécie nominativa, Biomphalaria tenagophila tenagophila, pelo aspecto do complexo peniano (prepúcio mais longo e proporcionalmente mais delgado em B. t. guaibensis, mais curto e proporcionalmente mais grosso em b. t. tenagophila0, pela razão entre os comprimentos da bainha do pênis e do prepúcio, pela razão entre os comprimentos do complexo uterino e do complexo peniano, e por um coeficiente de diferença de 2.44 para a razão entre a bainha do pênis e o prepúcio e de 2.02 para a razão entre o complexo uterino e o complexo peniano. A concha e os outros órgãos do sistema genital são semelhantes nas duas subespécies. A B. t guaibensis tem grande semelhança com a Biomphalaria occidentalis Paraense, 1981, mas dela se distingue facilmente pela presença de uma bolsa vaginal, que falta na B. occidentalis, além de apresentar diferença altamente significante nas razões bainha do pênis: prepúcio e complexo uterino: complexo peniano. Experiências de cruzamento que trazem apoio adicional ao reconhecimento da B. t. guaibensis como subespécie serão relatadas em outra publicação

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

“…In some B. t. guaibensis specimens from different populations than those analysed in our study, a dark pigmentation was observed on the renal tube, which had not been reported by Paraense (1984). Among the planorbid species described in Brazil, the only species known to have a pigmented renal tube is B. glabrata, the main S. mansoni transmitter species in Brazil (Paraense 1975).…”

“…Although a survey by Teles et al (1991) showed no evidence of such species in RS, Paraense (1984) had reported its occurrence in Arroio Grande, Jaguarão and Pelotas (RS).…”

“…In Rio Grande do Sul (RS), Brazil, there have been reports on the occurrence of B. tenagophila (Paraense & Deslandes 1959), B. straminea (Cunha Neto 1972), Biomphalaria oligoza (Paraense 1974), B. peregrina (Paraense 1966), Biomphalaria tenagophila guaibensis (Paraense 1984) and B. glabrata . The presence of S. mansoni in the state has been associated with the occurrence of B. glabrata in water collections surrounding Rio dos Sinos, in the municipality of Esteio (Graeff-Teixeira et al 1999).…”

“…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).…”

Dominant character of the molecular marker of a Biomphalaria tenagophila strain (Mollusca: Planorbidae) resistant to Schistosoma mansoni

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Biomphalaria tenagophila is a planorbid with a wide distribution in South America (Paraense 1984), and has epidemiological importance, since this species maintains the cycle of the trematode Schistosoma mansoni in some areas in Brazil. In spite of its dominance in some areas, B. tenagophila is found in the nature with low rates of infection, however, it is responsible for the majority of the autochthonous cases of schistosomiasis in the state of São Paulo, as well as for the foci of the disease in the states of Minas Gerais and Santa Catarina (Paraense 1986).

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