FACTORS INFLUENCING TOTAL HEMOCYTE COUNTS IN FRESH-WATER GASTROPODS

Total haemocyte counts were made in two freshwater gastropods. Lymnaea acuminata (Lamarck) f. rufescens (Gray), and Indoplanorbis exustus (D eshayes). Influence of age (shell size) was studied in groups of small , intermediate, and large-sized snails; large snails have significantl y higher haemocyte counts than intermediate and small snails. Effects of changes in ambient circumstances were studied in medium-sized snail s. Decreases in water temperature resulted in a rise in cell counts in both species; temperature increases gives a rise only in L. acuminata f. rufescens. Both increasing and lowering the pH of water influenced total haemocyte counts. Depending on the snail species, and on the ti me of exposure to altered pH levels, increases as well as decreases in cell counts were found. Replacing clean water by snail-conditioned wa ter did not seem to influence total haemocyte counts.