[Influence of some medium factors on the fecundity of Biomphalaria glabrata (Say, 1818) Mollusca, Pulmonata) in laboratory conditions].

In different samples of fresh waters we studied the fecundity of Biomphalaria glabrata. We tested, too, the influence of different concentrations of Na, Ca, Mg, and K-salts. The snail, B. glabrata, is not affected by very high rates of those salts but eggs laying is getting down when the amount of NaCl is between 2000 and 4000 mg/1, of MgCl2 between 410 and 763 mg/1 and KCl between 330 and 760 mg/1. The rate in Ca seems inactive in the field of fecundity but, in an other hand, high concentrations of Ca suppressed the inhibiting effect of the high rates in Mg. B. glabrata is not affected by high rates in Mg, when Mg/Ca is Low. The inhibiting effect of Mg begins when Mg/Ca is around 30. The importance of different kinds of substratum for eggs lying on fecundity was also studied.