A Brief Review of Parasitic Castration in Aquatic Snails and Its Contribution in Control of Diverse Vector Snail Populations and Trematodiases in Man and Animals

Abstract

Snails are invertebrate gastropod molluscs inhabited both the terrestrial and aquatic habitats. Most of these animals are dioeciously and their sexes are separated. In many monoecious (hermaphrodite) snail species, individuals have both male and female gonads. But in pulmonate monoecious snail species individuals have only single gonad called “ovotestis” which contains both testicular and ovarian tissues. In general, aquatic snail species are intermediate hosts of digenean trematode parasites of vertebrates including man and animals. In addition, aquatic snails are also act as vector of diverse trematodiases, such as schistosomiasis, clonorchiasis, opisthorchiasis, fascioliasis, amphistomiasis, etc. The prevalence of these digenetic trematode parasitic diseases in diverse geographical provinces is depending on the population of vector or intermediate host snail species. In fact, the various larval stages of digenean trematode parasites, such as sporocysts, rediae and cercariae are developed and multiplied asexually in the organ of hepatopancreas and/or gonads of host snails. These parasitic trematode larvae also act as castrators for snails and potential to prevent or block partially or completely their reproduction called “parasitic castration”. In this biological process, trematode larvae destroy the gonads in two ways, one is mechanically and the other physiologically. Parasitic castration is also induces sex conversion, gigantism and alteration the gene expression in brain of snails. In present communication, the most common vector snail species, different forms of trematode larvae and their basic biology and mode of parasitic castration in aquatic snails and its contribution in control of diverse vector snail populations and spreading of trematodiases are considered and brief and critically reviewed. Simultaneously, research gaps have also been highlighted for further advance research work. This review is helpful in understanding of biology or mechanism of parasitic castration and its contributory role the balancing of aquatic ecosystem.