Sajeena Muhamed S.., Leji J., Babitha G.S. and Sheeja V.R.
Abstract
The climbing perch Anabas testudineus, a euryhaline air-breathing teleost, encounters wide fluctuations in environmental salinity in its natural habitat. This study investigates the responses of nitrogen metabolism and excretion during acute (0â20 g L-¹) and reverse (20â0 g L-¹) salinity transitions. Fish exposed to increasing salinity exhibited a significant elevation in plasma and tissue urea levels. These findings demonstrate that A. testudineus regulates its nitrogenous waste pathways through modulation of ureogenesis and amino acid metabolism during salinity stress. The species exhibits a flexible nitrogen excretion strategy that supports survival under fluctuating osmotic conditions, highlighting its adaptive metabolic plasticity in variable environments.