Toxic effect of environmental acid-stress on the sperm of a hill-stream fish Devario aequipinnatus: a scanning electron microscopic evaluation.

Environmental stress due to acidic pH of water was found to be one of the major factors leading to toxic effects on the sperm of a hill-stream fish Devario aequipinnatus of Megha- laya, India. The Scanning Electron Microscopy of the transverse section of testes of the fish col- lected from its natural habitat with acidic pH (5.6-6.0) showed that the sperms were clumped to- gether and their tails were either absent or were of extremely small length. The acrosome and mid- piece were also not well differentiated. When the fingerlings from the natural habitat were reared to maturity in aquarium with water from natural habitat after changing the pH to alkaline range (8.0-8.2), the clumping of the sperm was not observed. The sperm tail was found to be well-devel- oped along with well-differentiated acrosome and midpiece. Since the only change in the water quality parameters of the experimental aquarium as compared to those of the natural habitat was the pH, it is evident that the abnormal features of the sperm observed in fish from natural habitat is mainly because of environmental acid stress. Microsc. Res. Tech. 72:76-78, 2009. V C 2008