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M. C. Subhash Peter ¹, Elizabeth K. Joshua ¹, Vijayamma Rejitha ¹, Valsa S. Peter ¹

Affiliations
1 Department of Zoology, University of Kerala, Kariavattom 695581, Thiruvananthapuram, Kerala, IN

Abstract

The action of thyroid hormones on metabolite regulation of nimbecidine-exposed climbing perch was studied to understand the role of these hormones in tolerance mechanisms of fish to nimbecidine exposure. Anabas testudineus, the climbing perch, was treated with nimbecidine, a neem-based biopesticide, at nominated concentrations (60 and 600 μgL^-1) for 48 h, with or without THs, and the levels of triiodothyronine (T₃) and thyroxine (T₄), metabolite and nucleic acid were quantified. The treatment of THs along with nimbecidine produced a different metabolite pattern. A significant rise in serum T₃ occurred in the nimbecidine-treated fish but the serum T₄ level remained unaffected. Nimbecidine exposure increased the serum triglycerides and the serum urea but the serum glucose and liver total protein, RNA and DNA remained unchanged. Significant reduction in the aspartate aminotransferase and alkaline phosphatase activities occurred in the serum and liver of nimbecidine-treated fish but the lactate dehydrogenase and alanine aminotransferase activities remained unaffected. The data indicate that TH modifies the metabolite pattern of climbing perch during its exposure to nimbecidine and, thus, suggest that TH is involved in the mechanism of stress tolerance in fish.

Keywords

Anabas testudineus, Climbing Perch, Fish, Metabolism, Neem, Nimbecidine, Thyroid.

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M. C. Subhash Peter ¹, Janardhanan Leji ¹, Vijayamma Rejitha ¹, Joseph Ignatius ², Valsa S. Peter ²

Affiliations
1 Department of Zoology, University of Kerala, Kariavattom, Thiruvananthapuram 695581, Kerala, IN
2 Department of Zoology, Fatima Matha National College, Kollam 695001, Kerala, IN

Abstract

With a view to understand the mechanism associated with the tolerance of excess water-borne iron, thyroidal, hydromineral and metabolic responses were studied in the freshwater African catfish Clarias gariepinus after exposing them to nominated concentrations (6.2 and 62 μM) of ferric iron [Fe(III)] for 48 hr. Plasma triiodothyronine (T₃) and thyroxine (T₄) concentrations and the indices of metabolic and hydromineral regulations were analyzed in the iron-treated fish. Plasma T₄ (P<0.001) and T₃ (P<0.05) decreased in catfish after Fe(III) treatment. On the contrary, an elevated (P<0.001) plasma T₄ occurred in the fish kept for recovery in clean freshwater after iron-treatment. A significant (P<0.01) hyperglycemia was observed in 62 μM Fe(III)-treated fish whereas plasma urea concentration remained unchanged. Ouabain-dependent Na⁺, K⁺-ATPase activity increased (P<0.05) in the branchial tissue of 6.2 μM iron-treated fish but decreased in the renal (P<0.05), intestinal (P<0.01) and hepatic (P<0.01) tissues. Plasma Na⁺ and PO₄^2- decreased (P<0.05), whereas plasma K⁺ and Ca^2- increased (P<0.05) after Fe(III) treatment. Our results indicate that despite the modification in the metabolic and hydromineral regulation, water-borne Fe(III) suppresses the thyroid activity, and withdrawal of Fe(III) activates the thyroid function in African catfish, thus supporting the hypothesis that thyroid hormones are involved in iron handling in fish.

Keywords

Catfish, Clarias gariepinus, Ferric Iron, Osmoregulation, Thyroid, Fish.

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