Exposure of Rosy Barb (Puntius conchonius) Sperm to Abamectin as an In Vitro Assay of Cytotoxicity.

The acute cytotoxicity of abamectin to the sperm of rosy barb (Puntius conchonius) was tested. It was found that 79% sperm remained motile at 30 min after activation by hypo-osmotic sodium buffer (HSB), while the motility of sperm exposed to 0.14, 0.28, and 0.42 mu M abamectin for 30 min was reduced to 60%, 35%, and 15%, respectively. Exposure to abamectin at 0.56 mu M decreased the motility of sperm to an even lower value of 5.67% after 20 min of exposure. This indicates that the toxicity of abamectin to rosy barb sperm is both dose dependent and exposure time dependent. The ultrastructural examination showed that most of the sperm exposed to 0.14 mu M abamectin for 30 min remained morphologically normal, while the midpiece and its surrounding mitochondria of the sperm treated with 0.28 mu M abamectin for 30 min were severely damaged. For the sperm treated with 0.42 mu M abamectin for 30 min, the majority of the sperm were abnormal. Sperm heads were dissolved and the midpiece broken. The mitochondria are located in the midpiece of the sperm and may be the target of abamectin toxicity in rosy barb sperm. The results also suggest that rosy barb sperm are a suitable candidate for rapid screening of the acute toxicities of bioorganic pesticides.