THE EFFECT OF SODIUM CHLORIDE CONCENTRATION ON GROWTH AND EGG LAYING OF HELISOMA DURYI, BIOMPHALARIA ALEXANDRINA AND BULINUS TRUNCATUS (GASTROPODA: PLANORBIDAE)

Abstract

Helisoma duryi, Biomphalaria alexandrine and Bulinus truncatus were maintained in media with seven different sodium chloride concentrations ranging from 0.6 to 32 mM. Growth of H. duryi was significantly reduced only in the 32 mM NaCl treatment, while no significant effects were observed in the net reproductive rate or in egg-laying rates. Bulinus truncatus showed optimal growth within the range of 1 to 8 mM NaCl and the net reproductive and egg-laying rates were reduced in the 32 mM NaCl treatment. Growth of B. alexandrina was reduced in the 16 and 32 mM NaCl treatments, while the net reproductive rate was reduced in the 16 and 32 mM NaCl treatments, while the net reproductive rate was reduced in media with more than 2.0 mM NaCl. Hatching of B. truncatus eggs was not affected by the high NaCl concentrations, while the hatchability of H. duryi eggs was reduced in the 32 mM treatment. Survival of newly-hatched H. duryi was best in the 1 mM NaCl treatment while for B. truncatus survival was reduced only in the 32 mM treatment.