Biological and biochemical studies on Biomphalaria Alexandrina snails showing overgrowth and their infection with Schistosoma mansoni

ABSTRACT

The growth, egg-laying capacity, susceptibility to infection with Schistosoma mansoni and some biochemical parameters were-determined for Biomphalaria alexandrina snails which showing overgrowth compared to those of the same age having normal growth. During the period of 14 weeks, the growth rate of snails with overgrowth was significantly higher than those with the normal size. At the first week of observation the mean shell diameter of overgrowth snails was 5.75 +/- 0.8 mm and reaching 9.03 +/- 0.6 mm by the end of the 14[th] week, compared to 2.9 +/- 0.6 mm and 7.2 +/- 0.7mm for snails with normal size. The rate of increasing growth [relative to snails with the normal size] in the overgrowth snails was comparatively very high during the 1[st] week [ranged between 64.5% and 98.3%]. It was found that B. alexandrina snails with overgrowth laid higher number of eggs than those with the normal size. Their onset of egg-laying was at the first week of observation [1.42 eggs/snail/week] until reaching to the highest peak at the 15[th] week [18.7egg/snail/week]. Comparing with snails of the same age and normal size, the egg-laying started at the 5[th] week with a very low number of eggs [0.5 eggs/snail /week], reaching to 4.3 eggs/snail/week at the 15[th] week. There was a very highly significant reduction [p< 0.001] in the infection rate of snails with overgrowth [ranged between 5.0% and 8.3%] compared to those of snails with normal size [ranged between 52.4% and 52.9%]. The hemolymph glucose concentration of B. alexandrina with overgrowth was significantly [P<0.05] and highly significant [p<0.01 and p<0.001] higher than those of the corresponding snails with the normal size in Set I [snails from egg-masses of individual snails], Set II [snails from individual egg-masses] and Set III [snails from groups of egg-masses of groups of snails]. The total protein concentrations in hemolymph of snails which showing overgrowth were increased than those of normal size of Sets I and II, but urea concentrations were decreased in Sets I and III