Histochemical Insights into Brain Protein and Lipid Alterations in Aquatic and Terrestrial Molluscs under Heavy Metal Stress
S. R. Londhe *
Department of Zoology, Bharatividyapeeths Matoshri Bayabai Shripatrao Kadam Mahavidyalya, Kadegaon, India.
N. H. Shaikh
Department of Zoology, Dattajirao Kadam Arts, Commerce Science College Ichalkaranji, Kolhapur, India.
N. A. Kamble
Department of Zoology, Shivaji University, Kolhapur, India.
*Author to whom correspondence should be addressed.
Abstract
Background: Heavy-metal contamination can disturb neural biomolecules and compromise nervous-system integrity in molluscs.
Aim: This study compared time-dependent histochemical alterations in brain proteins and lipids between the freshwater snail Bellamya bengalensis and the terrestrial slug Semperula maculata following mercuric chloride exposure.
Study Design: A laboratory-based comparative histochemical study of two molluscan species.
Place and Duration of Study: The study was conducted in the Department of Zoology under controlled laboratory conditions during the experimental period. Healthy specimens of both molluscan species were collected, acclimatised, and exposed to the heavy metal for the planned duration.
Methodology: Healthy specimens of Bellamya bengalensis and Semperula maculata were exposed to a sublethal concentration of mercuric chloride (1.5 ppm) under controlled laboratory conditions. Following exposure, brain tissues were dissected, fixed, processed, and subjected to histochemical analysis. Mercury bromophenol blue staining was used to demonstrate total proteins, whereas Sudan Black B staining was used to detect lipids. Histochemical alterations were examined microscopically and compared between the aquatic and terrestrial species to assess heavy-metal-induced neurotoxicity.
Results: Heavy-metal exposure produced marked neurochemical changes in the brain tissues of both species. Bellamya bengalensis showed a marked reduction in protein-staining intensity within the cerebral ganglia, accompanied by moderate lipid depletion. In contrast, Semperula maculata exhibited more extensive lipid loss, localised vacuolisation, and greater structural disruption of brain tissue, indicating greater susceptibility to heavy-metal toxicity. The differences in histochemical responses suggest that habitat and physiological characteristics influence the extent of neurotoxic damage caused by heavy-metal exposure.
Conclusion: Heavy-metal toxicity alters brain protein and lipid composition in both aquatic and terrestrial molluscs. The greater neurochemical damage observed in Semperula maculata indicates species-specific sensitivity to heavy-metal stress. These findings support the potential use of molluscs as bioindicators for monitoring environmental heavy-metal contamination and contribute to an understanding of heavy-metal-induced neurotoxicity in invertebrates.
Keywords: Histochemistry, mercuric chloride, cerebral ganglia, protein depletion, lipid depletion, neurotoxicity, Bellamya bengalensis, Semperula maculata, aquatic molluscs, terrestrial molluscs