Abstract | Thyroid hormones secreted from thyroid gland has vital role for all living organisms such as mammals, vertebrates etc., for their regular growth and development. The secretion of thyroid hormones may get disrupted in marine organisms due to environmental pollution. Heavy metal (chromium, beryllium etc.,) or trace metal (lithium, titanium etc.,) pollution alters the thyroid hormone secretion not only in human beings; but also affects the aquatic species such as fish. Low or nil secretion of thyroid hormone will leads to metabolic stress that in turn breakdown the basic metabolic processes that eventually ends in disturbing the marine ecosystem. The current research work deals with observed alteration in the thyroid metabolism (causes hypothyroidism) and morphological (histology) changes occurred in fish species (selected organism– Channa punctatus and Oreochromis niloticus) exposed to sublethal concentration of Lithium [30%] for a chronic period of 60 days. The levels of FT3, FT4 and TSH tested were significantly decreased in treated groups when compared to the normal. Thus, it is evident that determination of thyroid hormone secretion and histological studies (FESEM – field emission scanning electron microscopy) were useful in determining the effect of trace metal pollution and its effect in freshwater fish species.
Novelty Statement | The study is based on the hypothesis that the deposition and exposure of heavy metal lithium is arising as environmental threat. Lithium exposed fresh water fishes can accumulate the ingested lithium in their vital organs. Further, it can cause acute toxic effects to both fresh water biota and humans upon feeding on these lithium exposed fishes. Thus, by eliminating the exposure of heavy metal into the water bodies, we can save the ecosystem.