Relationship between spermatozoa motility parameters, sperm/egg ratio, and fertilization and hatching rates in pufferfish (Takifugu niphobles)

• Sperm quantity and quality are factors strongly linked during IVF trials.
• CASA system was able to provide a good number of sperm quality biomarkers.
• Spermatozoa motilities and velocities showed high correlations with FR and HR.
• Spermatozoa velocities appear to be a key factor in the fertilization success.

The use of high quality gametes from both males and females during in vitro fertilization (IVF) trials is an essential step in order to achieve high fertilization and hatching rates. Although aquaculture hatcheries have focused more on egg rather than spermatozoa quality, some studies have demonstrated that sperm quantity and quality have a great influence both on fertilization/hatching success and the subsequent development of the embryo and larvae.In this study we have demonstrated that sperm/egg ratio and sperm quality are factors strongly related to each other in the pufferfish (Takifugu niphobles). Our results suggest that both factors should be taken into account as unique interrelated elements, making possible to obtain high fertilization rates using a successful combination of small amount of high quality sperm or high amount of low quality sperm.In addition, coefficients of correlation and determination among all the sperm motion parameters provided by a CASA system and fertilization/hatching rates were estimated for the first time in a marine species. Positive significant correlations were found in some parameters such as total and progressive motility (0.68 and 0.7 respectively). However, curvilinear velocity (VCL), straight line velocity (VSL) and average velocity (VAP) showed the highest coefficients of correlation (0.82, 0.8, and 0.81, respectively). In this respect, spermatozoa velocity appears to be a key factor in the fertilization process, especially when the number of spermatozoa per egg is limited in the aqueous environment.