Automated sperm morphology analysis in fishes: the effect of mercury on goldfish sperm

Abstract

This study is the first to examine the morphology of fish sperm using automated sperm morphology analysis (ASMA). The technique was applied to investigate the effect of an environmental pollutant, mercury, on the sperm morphology of goldfish Carassius auratus, and the effects on sperm morphology were compared with those on sperm motility. Goldfish sperm flagellar length was significantly shortened after instant exposure to 100 mg l−1 (368 µM) mercuric chloride, while curvilinear velocity (VCL) and the percentage of motile sperm were significantly decreased at mercuric chloride concentrations of 1 and 10 mg l−1 (3·68 and 36·8 µM), respectively. After 24 h exposure to 0·001 mg l−1 (0·0037 µM) mercuric chloride, flagellar length was significantly reduced in 38% of the spermatozoa. Following exposure to 0·1 mg l−1 (0·37 µM) mercuric chloride for 24 h, however, the majority of spermatozoa (98%), had significantly shortened flagella and increased sperm head length, width and area. Sperm motility was also significantly decreased at 0·1 mg l−1 (0·37 µM) mercuric chloride, probably due to the significantly reduced flagellar length at this concentration. This study shows that the morphological examination of fish sperm by ASMA provides, not only, an excellent tool for monitoring reproductive disruption caused by environmental pollution, but also has applications to other areas of fish reproductive biology, such as cryopreservation and aquaculture.