Biomphalaria straminea and other planorbids in the Dominican Republic

In addition to previous records of Biomphalaria glabrata in the Dominican Republic, the southern central communities of Haina Arriba and Boca Chica, in the National District, are reported as new localities for that species; other species collected were Biomphalaria obstructa, B. helophila, Drepanotrema lucidum and Lymnaea viatrix. Biomphalaria straminea, a potential vector of Schistosoma mansoni, was found for the first time in the country, in the River Iguamo, just outside of the community of San Pedro de Macorís.

Ocorrência de planobídeos pleistocênicos no município de Jacobina, Bahia

Registramos, com base em dados paleontológicos e estratigráficos e de acordo com a morfologia da concha, Biomphalaria aff. glabrata (Say,l8l8), do Pleistoceno superior (ou Holoceno) da Gruta das Onças, distrito de Caatinga do Moura, município de Jacobina, Estado da Bahia. Registramos também mais uma evidência da antiga presença de água na referida gruta, que apoia a hipótese levantada por Cartelle & Bohorquez (1982) sobre o local.

Biomphalaria kuhniana (Clessin, 1883), planorbid mollusc from South America

The validity of Biomphalaria kuhniana (Clessin, 1883) is confirmed through morphological study of specimens from Surinam (type locality) and the area of Tucurui (Tocantins river, state of Pará, Brazil) in comparison with B. straminea (Dunker, 1848), and throught crossing experiments which revealed complete reproductive isolation between the two species. The full-grown shell of kuhniana is smaller (about 7.5 mm) than that of straminea (11 mm to 16.5 mm). Anatomically they differ in the degree of corrugation of the vaginal wall (little developed in kuhniana, conspicuous in straminea), number and shape of prostatic diverticula (kuhniana 4 to 9, shorter and less branched; straminea 9 to 18, longer and more branched),number of muscle layers at the middle of the penis (two in kuhniana, three in straminea), distal segment of the spermiduct usually straight or slightly wavy in kuhniana, more or less curly in straminea. Differences between B. kuhniana and B. intermedia (paraense & Deslandes, 1962) are less marked. The latter has a shell up to about 12 mm in diameter, 7 to 15 prostatic diverticula, two muscle layers at the middle of the penis, and a vaginal wall with a combination of a more or less developed corrugation (or sometimes a mere swelling) on the left of the spermathecal duct and a rudimentary pouch on the right of the duct. A Biomphalaria straminea complex is proposed to include that species as well as B. kuhniana and B. intermedia.

A potential vector of Schistosoma mansoni in Uruguay

Susceptibily experiments were carried out with a Biomphalaria straminea-like planorbid snail (Biomphalaria aff. straminea, species inquirenda) from Espinillar, near Salto (Uruguay), in the area of the Salto Grande reservoir, exposed individually to 5 miracidia of Schistosoma mansoni (SJ2 and BH2 strains). Of 130 snails exposed to the SJ2 strain, originally infective to Biomphalaria tenagophila, 30 became infected (23%). The prepatent (precercaria) period ranged from 35 to 65 days. The cercarial output was irregular, following no definite pattern, varying from 138 to 76,075 per snail (daily average 4.3 to 447.5 and ending up with death. Three specimens that died, without having shed cercarie, on days 69 (2) and 80 after exposure to miracidia, had developing secondary sporocysts in their tissues, justifying the prospect of a longer precercarial period in these cases. In a control group of 120 B. teangophila, exposed to the SJ2 strain, 40 became infected, showing an infection rate (33.3%) not significantly different from that of the Espinillar snail (X [raised to the power of] 2 = 3.26). No cercarie were produced by any of the Espinilar snails exposed to miracidia of the BH2 strain, originally infective to Biomphalaria glabrata. Four specimens showed each a primary sporocyst in one tentacle, which disappeared between 15 and 25 days post-exposure, and two others died with immature, very slender sporocysts in their tissues on days 36 and 54. In a control group of 100 B. glabrata exposed to BH2 miracidia, 94 shed cercariae (94%) and 6 remained negative. Calculation of Frandsen's (1979a, b) TCP/100 index shows that "Espinillar Biomphalaria-SJ2 S. mansoni" is a vector-parasite "compatible" combination. Seeing that tenagophila-borne schistosomiasis is prevalent in Rio de Janeiro and São Paulo states and has recently spread sothwards to Santa Catarina state, and the range of B. tenagophila overlaps taht of the Espinillar Biomphalaria, the possibility of schistosomiais establishing itself in Uruguay, although not imminent, is not to be disregarded.

Dispersão de Biomphalaria straminea no estado de Sergipe: um estudo comparativo com dezenove anos de intervalo

No presente trabalho, realizado no Estado de Sergipe, procurou-se determinar a distribuição geográfica e as interrelações entre populações naturais de duas espécies do gênero Biomphalaria, os caramujos vetores do Schistosoma mansoni no nordeste do Brasil. Dados coletados em 1969 mostraram que B. straminea, com uma única exceção, estava limitada à região semi-árida, enquanto B. glabrata habitava a região litoral/mata, ambas no Estado de Sergipe. Esta distribuição espacial parecia indicar que as espécies acima denominavam territórios exclusivos. Coletas de caramujos feitas em 1988, nas mesmas 37 localidades pesquisadas anteriormente (1969), evidenciaram que B. straminea havia invadido territórios previamente ocupados por B. glabrata. Estes resultados sugerem que as duas espécies estão interagindo em processo de deslocamento competitivo. Foram ainda determinadas as taxas de infecção natural dos caramujos, assim como foram registrados alguns aspectos ecológicos de seus criadouros.

Potential schistosome-vector snails and associated trematodes in ricefields of Corrients province, Argentina: preliminary results

Considering the possibility of introduction of schistosomiasis mansoni into Argentina as a consequence of dam construction on the Rio De La Plata basin, preliminary studies have been carried out on agrosystems such as ricefields in Corrientes province with the following purposes: 1) to survey and estimate the relative abundance of planorbids and identify potential vector species; 2) to identify environmental factors capable of influencing Biomphalaria population dynamics; and 3) to find out snail-parasite associations and estimate snail infection rates in order to detect possible competitive interactions between larval stages of native trematodes that could be used in biological control of Schistosoma mansoni. Three potential schistosome vectors were detected in ricefields, namely Biomphalaria straminea, B. tenagophila and B. peregrina, although B. orbignyi, a species refractory to infection with S. mansoni, proved the most frequent and abundant. Positive correlations (P<0.05) were found between Biomphalaria abundance and some environmental parameters: conductivity, hardness, calcium, nitrites plus nitrates, ammonium and bicarbonates. Water temperature correlation was negative (P<0.05). No correlation (P>0.05) was found in total iron, phosphates (SRP), pH and soil granulometry. Echinocercariae developed from rediae and belonging to Petasiger sp., Paryphostomum sp., and other undetermined species were found.

Spatial and seasonal trends of a natural population of Biomphalaria occidentalis in northeastern Argentina

This study aims to analyze the age of a population of Biomphalaria occidentalis on a pound of Riachuelo river basin, wich is one of the three most important Middle Paraná river affluents in Corrientes province. Samples were drawn from three stations, were spatial and temporal numerical variations of the snail, as well as its relation with different environmental parameters, mainly temperature, rainfall, pH and conductivity, were analyzed. Snail abundance is given in number of individuals/hour. The differences between the three sampling stations, estimated by nonparametric tests, was nonsignificant. A relative scale to the greatest shell diameter was employed to build the age pyramids. Temporal fluctuations of snail abundance correlated negatively with the highest monthly accumulated temperatures (P < 0.05). Although different floristic compositions were observed at the three stations, no significant numerical variations were detected in B. occidentalis spatial distribution. Reproductive activity took place between March-April and November with overlapping cohort system. During summer (December-Febuary) mortality increased along with temperature and reproductive activity was not evident.

Biomphalaria occidentalis paraense, 1981 in the state of Minas Gerais, Brazil

A population of Biomphalaria occidentalis was found for the first time in the State of Minas Gerais. It was probavly introduced into the Várzea das Flores dam, in the municipality of Contagem, the area o0f study, during fish stocking in 1985. There is possibility of "competitive exclusion"between that species and B. glabrata, previously the only Biomphalaria found in the region. The present geographical distribution of B. occidentalis in Brazil is listed.

Egg-laying induced by insemination in Biomphalaria snails

Contrasting with many populations of Biomphalaria glabrata and B. straminea previously dealt with in this laboratory, which when reared in isolation deposit self-fertilized eggs without apparent restraint, isolated individuals of the former species from São Sebastião do Passé, Bahia state, and of the latter from Porto Alegre, Rio Grande do Sul state, show a high degree of self-sterility, laying egg capsules with a few usually abortive, rarely viable egg cells, or just jellylike masses without egg cells. When two individuals are paired they readily copulate, usually withing 24 hr deposit one of more egg capsules containing many eggs, and egg-laying continues up to exhaustion of stored allosperm. So far this aspect of reproductive biology has been only observed in a number of populations of the planorbid species Helisoma duryi, and should be viewed as a populational rather than specific characteristic. Since sterility is not overcome by courtship, copulation and insemination by individuals of a different species, the stimulating factor that causes ovulation in the studied self-sterile individuals is considered to be present in the conspecific allosperm.

Neotropical planorbid snails with apertural lamellae: I. Biomphalaria helophila (Orbigny, 1835)

A definition of Biomphalaria helophila (Orbigny, 1835) is presented, based on examination of the shell and reproductive system of topotypic specimens and extended to a number of samples from other localities. The following nominal species and subspecies, collected from type localities, proved junior synonyms of B. helophila: Planorbis albicans Pfeiffer, 1839; Planorbis dentatus Gould, 1844; Planorbis dentiferus CB Adams, 1845; Planorbis dentiferus edentatus CB Adams, 1851; Planorbis dentiens Morelet, 1849; Planorbula dentiens edentula Fischer & Crosse, 1880; Planorbis stagnicola Morelet, 1851; and Tropicorbis shimeki FC Baker, 1945. B. helophila was also identified in samples from Costa Rica, Guatemala, Haiti, Dominican Republic, Puerto Rico and Barbados.

Genetic variability in Brazilian populations of Biomphalaria straminea complex detected by simple sequence repeat anchored polymerase chain reaction amplification

Biomphalaria glabrata, B. tenagophila and B. straminea are intermediate hosts of Schistosoma mansoni, in Brazil. The latter is of epidemiological importance in the northwest of Brazil and, due to morphological similarities, has been grouped with B. intermedia and B. kuhniana in a complex named B. straminea. In the current work, we have standardized the simple sequence repeat anchored polymerase chain reaction (SSR-PCR) technique, using the primers (CA)8RY and K7, to study the genetic variability of these species. The similarity level was calculated using the Dice coefficient and genetic distance using the Nei and Li coefficient. The trees were obtained by the UPGMA and neighbor-joining methods. We have observed that the most related individuals belong to the same species and locality and that individuals from different localities, but of the same species, present clear heterogeneity. The trees generated using both methods showed similar topologies. The SSR-PCR technique was shown to be very efficient in intrapopulational and intraspecific studies of the B. straminea complex snails.

Plesiophysa guadeloupensis ("Fischer" Mazé, 1883)

A description is presented of the shell and anatomic characters of the planorbid mollusk Plesiophysa guadeloupensis ("Fischer" Mazé, 1883), based on topotypic specimens from a pond in Borricaud (Grande Terre, Guadeloupe). Comparison with previous descriptions of nominal species of Plesiophysa points to its identity with P. ornata (Haas, 1938), of which it is a senior synonym.