Comparative Studies on the Structural Changes in Some Kind of Snails During the Estivation and Trematoda Infection

Abstract

This study was undertaken to elucidate 'the changes and differences in Biomphalaria glabrata, the most important snail host of Schistosoma mansoni in Western Hemisphere, during the process of estivation. The growth rate (increase in shell diameter and wet weight), survival rate and histopathology were observed during the 22 weeks of experimental period in comparison with the control snails. Two groups of snails, each group consisted of 36 snails, were used for the present experiment One group of snails was undergone artificial estivation, and other group was applied as normal control reared in the water. The results obtained were as follows: 1. The growth rate of estivating snails (Group n) was consistently lower than that of control snails (Group I) kept in the water. 2. The growth rate rose rapidly when the estivating snails were put into water again after 12 weeks of estivation. 3. Survival rate of the estivating snails was lower than that of their controls. 4. During the estivation, the reduction of parenchyme and degenerative pictures were prominently observed in the hepatopancreas, ovotestes, seminal vesicle and saccular portion of kidney. And little change was observed in the rectal ridge and tubular portion of kidney in the estivating snails. 5. After return of the estivating snails into water, they almostly restored their normal • structures within 4 weeks.