Standardization of European eel (Anguilla anguilla) sperm motility evaluation by CASA software

The development of powerful computer-assisted sperm analysis software has made kinetic studies of spermatozoa possible. This system has been used and validated for several species, but some technical questions have emerged regarding fish sample evaluations (i.e., frame rate, sperm dilution, chamber model, time of analysis, magnification lens, etc.). In the present study, we have evaluated the effects of different procedural and biological settings with the aim to correctly measure sperm quality parameters of the European eel. The use of different chambers did not affect the sperm motility parameters. However, regarding lens magnification, 10× was the most accurate lens, showing the least variation in the acquired data. Similarly, the frame rate setting resulted in a dramatic effect in some sperm kinetic parameters, primarily in terms of curvilinear velocity; we therefore recommend using the camera's highest available frame rate setting. Finally, the reduction in sperm motility over postactivation times suggests that sperm analysis should be performed within the first 60 seconds after activation of the European eel sperm. In conclusion, some protocol variables of sperm analysis by computer-assisted sperm analysis software can affect the measurement of eel sperm quality parameters, and should be considered before directly comparing results obtained by different laboratories. Moreover, because marine fish species show relatively similar features of sperm kinetic parameters, these results could be considered in the evaluation of the motility of sperm from other fish species.