Abstract:
This study extended over a period of three years, from July 1975 to June 1978. The project was financed by Pakistan Science Foundation and was carried out in the Laboratories of the Zoology Department, University of the Punjab, Lahore.
Eighteen thousand five hundred snail specimens belonging to nine freshwayer species obtained from fifty four localities from all over Pakistan were examined for the presence of larval trematodes. As a result of this survey fifty seven species of cercariac were recovered studied and identified. Out of these thirty eight are new to science and eleven are new records from Pakistan. For every cercaria its behaviour, emergence and the structure of the redia or the sporocyst , as the case may be, was also studied.
An attempt was made to study the life histories of five cercariae but we were able to complete the life histories of only two species in the laboratory.
The histochemistry of five cercariae, three belonging to xiphidiocercous group, one to echinostome group and one to pleurolophocercous group was studied. A comparative assessment of the histochemical nature of different glands has been made and possible functions have been assigned to then.
Two species of cercariae and two species of snails were exposed to various concentrations of some of the commonly used insecticides. Some of these insecticides have been found to be highly toxic to both the cercariae and snails at very low concentrations.
The effect of pH and industrial wastes on cercariae and their snail host was also studied.
