Changes in ionic composition of media during culture of Bulinus tropicus and the relationship between ion concentrations and inhibition of growth and egg-laying.
Changes in media composition were monitored during conditioning by B. tropicus, B. truncatus, B. globosus and Biomphalaria glabrata maintained under adverse conditions in closed systems. Oxygen and calcium ion concentrations fell progressively with time, while potassium, magnesium and ammonium ions increased. Dose-response relationships were established for the major ions, using growth and egg-laying bioassays. Comparison of the inhibitory thresholds of individuals inorganic ions with their concentrations in snail-conditioned water suggested that changes in these ions alone were insufficient to account for the observed inhibitions. There was evidence to suggest that ammonia acted in combination with an unidentified factor in the conditioned medium to limit growth and fecundity.