Central nervous system (CNS) of gastropods is extensively studied for its pathology and immunocytology; there is scanty information on histochemical alterations in neuronal cells due to heavy metal. This study was designed to investigate histochemical alterations in cerebral neurons of freshwater snail Bellamya bengalensis after intoxication with mercuric chloride (HgCl2) and zinc chloride (ZnCl2). As per chemical components cerebral ganglia of Bellamya bengalensis showed three different zones, namely, periganglionic connective tissue sheath, interperikaryonal space, and neuropil. After intoxication, increased acidic content in extracellular matrix (ECM) of neuronal cells was found. These alterations were directly proportional to time of exposure period. From results, HgCl2 proved its highly toxic nature over chemical composition of cerebral neuronal cells of freshwater snail Bellamya bengalensis compared to ZnCl2 intoxication. 1. Introduction A wide range of inorganic and organic compounds caused aquatic contamination including heavy metals, combustible and putrescible substance, hazardous wastes, explosives, petroleum products, and phenol and textile dyes [1]. The major component of inorganic contaminants has some different problems than organic contaminants [2, 3]. Notably aquatic ecosystems are often polluted with anomalously high levels of toxicants (organic and inorganic substances), which find their way into the aquatic systems with waste and effluents generated from industrial enterprises [4]. Heavy metals are highly active contaminants of biotic material, which enters the aquatic environment through a number of routes [5]. Aquatic poisoning by metals has increased during last decades due to their extensive use in agricultural, chemical, and industrial processes resulting in threat to living organisms [6]. As a result, inorganic contamination has increased level of transfer across food chain/web leading to health hazards [7]. Heavy metal pollution of terrestrial and aquatic ecosystems has long been recognized as a serious environmental concern [8]. From the invertebrates, aquatic and terrestrial molluscs are measurably affected by heavy metal pollution. Heavy metal continued to be common pollutant in aquatic ecosystem and proved toxic to aquatic organism [9, 10]. Bivalve and gastropod molluscs are excellent sentinel organisms for the study of toxic effects of metals in aquatic ecosystems [11]. Maximum concentration of heavy metal in aquatic or terrestrial media affects numerous phenomena involved in the development and maintenance of molluscan
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