Quantitative semen parameters of Atlantic cod (Gadus morhua) and their physiological relationships with sperm activity and morphology

Aspects of sperm motility and metabolism are important for understanding gamete quality. The objectives of this study were to investigate changes in adenosine 5′-triphosphate (ATP), and lactate dehydrogenase (LDH) of Atlantic cod sperm over time following activation, and to determine if initial semen parameters (ATP, LDH, Na+, K+, Ca2+, total protein, osmolality, pH, and spermatocrit) are indicative of sperm quality. Analyses of ATP and LDH were also performed on sperm cells at 0.5, 2, and 90 min post-activation, while sperm activity was recorded at 0.5 and 2 min. Initial semen parameters did not appear to be strong indicators of sperm quality but some correlations were observed between pH, LDH, K+, and protein and motility parameters in the first two min post-activation. The lack of significant correlation may be attributed to the low variability of almost all parameters observed between males in this study. There was a significant effect of post-activation time on sperm ATP and LDH with both ATP and LDH decreasing with time after activation. The decrease in ATP levels during the course of sperm motility suggests that the metabolic activity is too low to substitute the energy consumed. Continued research on sperm motility and metabolism will lead to a better understanding of fertilization and gamete quality in this species.