Effects of Acid Water on Shells, Embryos, and Juvenile Survival ofPlanorbella trivolvis(Gastropoda: Pulmonata): A Laboratory Study

Abstract

ABSTRACT Adults of the freshwater pulmonate snail Planorbella trivolvis were maintained in aquaria at four pH levels of approximately 4.9, 5.9, 6.8 and 7.8. Adult mortality was moderate over 82 days (10–32%) and not related to the magnitude of pH reduction. Decrease in both shell calcium per unit tissue dry weight and shell calcium per unit maximum shell diameter were significantly related to both time of exposure and pH level. Both measures were significantly reduced after 53 days of exposure to acid water such that for mean Ca mg−1, pH 4.9=5.9 < 6.8 < 7.8 and for mean Ca mm−1, pH 4.9=5.9 < 6.8=7.8. Empty (ashed) shells without a periostracum lost CaCO3 about 4.6 times faster than did shells of live snails with periostracum intact. Fecundity per snail did not differ greatly from one pH treatment to another although at pH 4.9 the embryos developed slowly and showed a high incidence (38.5%) of abnormality compared to embryos reared at pH 7.8 (4.8% abnormality). Juvenile survival at pH 5.1 was poor with 100...