A note on Biomphalaria straminea (Dunker, 1848) from Manaus, State of Amazonas, Brazil

Abstract

Biemphalaria straminea ( — centimetra lis), an important intermediate host of Schistosomiasis in Brazil, has large geographical distribution. It is known from Venezuela, Guianas and Brazil, reaching south to about 20° latitude. In Northeastern Brazil B. straminea is a most important vector of the disease. It is the only vector known it the State of Cea­ ra as w ell as in most of the territories of the State of Pernambuco, Paraiba and Rio Orande do Norte. B. straminea is also known from North­ ern Brazil. It occurs in several areas of the carboniferous formation of the Amazon basin (Sioli, 4 ) . This species was incriminated as the vector of Schistoso­ miasis in a limited focus localized in Belterra, Fordlandia, State of Para. The material used in the current paper was received from Dr. Mario Morais of the Instituto Nacional de Pesquisas aa Amazo­ nia” in September 1965. It consisted of 56 snails from which 42 were alive. Collected outside the town of Manaus, State of Ama­ zonas, Brazil, the snails, were found in lake Rei in center of Careiro and in a small “igarape” afluent of the “igarape” Cachoeirinha. The snails, kept in tanks, were used for observations on morphology, Crossing experiments and exposition to the infection with a Northeastern strain of Schistosoma mansoni. Prior to the experiments ali the snails were exposed to sun light during few hours for several days and none of them shed cercariae of the mansoni type. Six snails were preserved and the animais dissected. The morphology of the animais dissected, particularly genitals, kidney and radula, was the same as compared with typical specimens of B. straminea from several places in Brazil. Crossing experiments were performed between pigmented snails from Manaus and an albino strain of B. straminea from Quixeramobim (State of Ceara, North­ eastern Brazil) according to techniques previously described (Barbosa et a l., 1). Two couples were used. Each couple (Ma­ naus x Quixeramobim) was put to mate in a small glass Container for 30 days. After that period the albino snails were tsolatsd from its partners and followed during another 30 days. Results of those expe­ riments show that the two snails are conspecific. In both experiments pigment­ ed snails were produced exclusively. Couple 1 produced 69 pigmented F1 snails while couple 2 produced 94 snails of the same type. No albino snails were obtained dur­ ing the 30 days of observation. Hybrids obtained were fertile and produced prosperous colonies. Snails from Manaus were exposed to miracidia of a Northeastern strain of S. mansoni. Each snail was exposed to 5 miracidia, and examined daily for cerca­ riae after the 20 th day of the infection Negative results were obtained of the