The occurrence of 90 Biomphalaria straminea shells displaying marked deformation in their last whorl, is reported. The referred to planorbid population originates from a strain collected, about three years ago, in Curvelo, MG (Brazil), and which has been kept in laboratory glass aquarium.

An experiment on the inter-specific mating of B. glabrata and B. tenagophila snails was related. The results led to conclude that the snails prefer intra-specific mates, even though inter-specific ones occur.

Among laboratory-bred Biomphalaria glabrata, a live snail in an anomalous shell was found. The anomaly consisted in changes of level in the whorls. The specimen was isolated for a study on its biological behaviour. Afterwards, another specimen displaying a similar anomaly was joined to it. The results obtained showed their biological functions to be normal, their anomaly being of genetic character. In F1 embryos, the anomaly observed was 0.01%. In a 25-month period of investigation, 13 anomalous embryos were isolated. […]

The fecundity (ratio egg-masses per snail, eggs per snail and eggs per egg-mass) and the fertility (hatchability and viability of eggs) of Biomphalaria glabrata and Biomphalaria tenagophila were compared during one year, in the laboratory. The average of eggs per egg-mass was significantly higher in B. glabrata (19.9) than in B. tenagophila (16.2) and both species showed highest fecundity during April. The influence of temperature was very small. The fecundity defined as egg-mass per snail per day was greater in […]

After experiments with two types of food, lettuce and “aquariol” (i.e., animal protein flour for ornamental fish) both isolated and in association, in the breeding of Helisoma (Seminolina) duryi (Wetherby, 1879), the following results: were obtained: 1. Snails fed on fresh lettuce yielded, at the end of 17 weeks, 826 egglavings or, better, 17,707 eggs. 2. Specimens fed on “aquariol” produced 534 egg clutches or 11,361 eggs. 3. Snails fed on both fresh lettuce and “aquariol” happened to provide 1,355 […]

The susceptibility of descendents of a Biomphalaria straminea sample from Piripiri, Piauí, Brazil was tested with two strains of Schistosoma mansoni: “LE” (Belo Horizonte) and “SJ” (São José dos Campos). The SJ strain infected 12.5% of the surviving specimen of the B. straminea and 63.6% of the B. glabrata, which were used as controls. The B. straminea tested were refractory to the LE strain; whereas, 84% of the B. glabrata were positive.

The efficacy of magnesium thermophosphate (a soil corrective and fertilizer) was tested as food for laboratory planorbids for a period of five weeks, during which time the shell growth of Biomphalaria glabrata (Say, 1818) and Helisoma duryi (Wetherby, 1879) experimental populations was observed. Surprisingly, this mineral product blocked the oviposition of both species from the second week on, when added to the latosoil either isolatedly or associatedly. Consequently, magnesium phosphate, when widely used in new agricultural areas obtained through modern […]

The biological control of planorbids (Biomphalaria straminea Dunker, 1848; B. tenagophila Orbigny, 1835 and B. glabrata Say, 1818) through the predation of their eggmasses by the pilid Pomacea haustrum Reeve, 1856, was observed under laboratory conditions. Of 829 eggmasses laid by B. straminea, 203 (24.5%) were exposed to 10 specimens of P. haustrum and 200 (98.3%) of them were predation. Of 892 eggmasses laid by B. tenagophila, 210 (22.5%) were exposed to 10 specimens of P. haustrum and 194 (97.0%) […]

A malacological survey was carried in the State of Rondônia, Brazil, in order to establish the geographical distribution of aquatic mollusks with special emphasis on the genera Biomphalaria. Eleven counties along the BR-364 highway were studied, totaling 162 limnic ecossistems, of which 77 (48%) were positive for at least one species of mollusk. The following species were found: Gastropoda, Planorbidae: Biomphalaria sp., B. amazônica, B. occidentalis, Drepanotrema anatinum, D. lucidum, D. depressissimum and D. cimex; Physidae: Stenophysa marmorata; Ancylidae: Gundlachia […]

A systematic survey was carried out in the area of the 6th Administrative Region of the State of S.Paulo, in order to discover the distributional patterns of planorbidic snails. Biomphalaria tenagophila is incriminated as the intermediary of Schistosoma mansoni in Bebedouro county where some human cases of the disease have been observed since 1976. Biomphalaria straminea lives at two breeding places – in Serrana and Ribeirão Preto. It is concluded that there is little possibility of schistosomiasis spreading in the […]