Effect of Chronic Exposure to Methomyl on Tissue Damage and Apoptosis in Testis of Tilapia (Oreochromis niloticus) and Recovery Pattern.

Abstract

Tilapia were exposed to 0, 0.2, 2, 20, 200µg/L methomyl for 30days, and then transferred to methomyl-free water for 18days. Caspase-8 in serum, apoptosis rate, microstructure and ultra-microstructure of testis were checked after methomyl exposure and at 18days after transferring to methomyl-free water. There were no significant changes in Caspase-8 activity, apoptosis rate, and tissue structure in testis exposed to 0.2 and 2µg/L compared with control. However, when tilapia exposed to 20 and 200µg/L, the Caspase-8 activity and apoptosis rate were induced significantly, and tissue damage happened compared with the control. Thus it would appear 2µg/L methomyl might be considered as the no observed adverse effect level. Recovery data showed that the effects produced by lower concentration of 20µg/L were reversible but not at the higher 200µg/L concentration.