Influence of Coconut Husk Retting Effluent on Metabolic, Interrenal and Thyroid Functions in the Air-Breathing Perch, Anabas testudineus Bloch

To understand the physiological mechanism of stress tolerance in fish living in coconut husk retting grounds, we examined the metabolic pattern, and interrenal and thyroidal activities in the air-breathing perch, Anabas testudineus after exposing them to the effluent of coconut husk retting (CHRE). Cortisol, the end product of interrenal axis and triiodothyronine (T₃) and thyroxine (T₄), the primary hormones of thyroid, were measured in the plasma of these fish together with the indices of metabolic regulation. Five days of CHRE exposure increased the plasma cortisol but decreased the plasma T₄ without affecting the plasma T₃. The concentration of plasma glucose, triglycerides and urea were significantly increased in the CHRE-exposed fish. Significant reduction in the concentration of liver total protein, RNA and DNA occurred in the CHRE-treated fish. CHRE treatment, while increasing the alanine aminotransferase and alkaline phosphatase activities, decreased the aspartate aminotransferase activity in the liver. Besides identifying plasma glucose and cortisol as reliable biomarkers of CHRE-induced stress, our results suggest that these fish reallocate their energy resources during stress where both interrenal and thyroid glands have roles to play.