Solutions of magnesium metallic and other salts of magnesium were tested in the laboratory to study the action on B. glabrata oviposition. For each solution, 10 adult snails from Pampulha, Belo Horizonte-MG (Brazil), reared in the laboratory, were used. In experiment I solutions, in dechlorinated water, of magnesium (Mg), magnesium chloride (MgCl2. 6H2O), magnesium carbonate [(MgCO3)4.Mg(OH)2.nH2O], magnesium nitrate [Mg(NO3)2.6H2O] and magnesium sulfate (MgSO4.7H2O) were tested; and in experiment II, solutions of Mg, Mg + latosoil, MgCO3, MgCO3 + latosoil, always at concentrations of 500 and 1000 ppm. The snails were kept in dechlorinate water for an adaptation period of two weeks. Then, in the solutions tested, for an exposure period of four weeks, and then in dechlorinated water for a recuperation period of a further two weeks. Each seven days egg-masses were counted and eliminated and the solutions renewed. It was observed that the solutions of Mg and MgCO3 alone or in association with the latosoil were responsible for a significant decrease in the number of egg-masses, but not a complete stopping of oviposition, when adaptation and exposure periods were compared. The solutions of Mg and MgCO3 must not be considered as possible molluscicide for the control of B. glabrata populations, since the activity was detected only when a high concentration of those substances were used.
Biomphalaria glabrata; Oviposition; Magnesium