Sperm motility parameters as indicators of seminal quality: a comparative study between fish species.

This study investigated the patterns of sperm kinetics in two fish species, Piaractus mesopotamicus and Pseudoplatystoma reticulatum and their relationship with seminal quality. Semen samples were collected after hormonal induction, with the aim of identifying indicators of seminal quality and their relationship with reproductive success. The results revealed marked interspecific differences: P. reticulatum exhibited longer-lasting motility (83 ± 31 s) with stable linear movement patterns after activation, while P. mesopotamicus showed more intense but shorter-lasting motility (41 ± 8 s), exhibiting initial circular trajectories that transitioned to linear patterns. In P. reticulatum, positive correlations were found between total motility (MOT), progressivity (PROG), velocities: curvilinear (VCL), straight-line (VSL) and average (VAP), with hatching rate (HR). These are suggested to be reliable predictors of seminal quality. For P. mesopotamicus, multivariate analysis (PCA) indicated that sperm quality was associated with a specific combination of VCL, VAP, and amplitude and lateral displacement of the head (ALH), although no single parameter was directly correlated with HR. These differences reflect distinct evolutionary adaptations to their lotic reproductive environment, associated with effective oocyte fertilization capacity and larval hatching rate. P. mesopotamicus is adapted for rapid fertilization, with higher sperm speed, while P. reticulatum demonstrates more sustained sperm motility. These results highlight the need for species-specific approaches and demonstrate that the simple evaluation of sperm kinetic parameters in fish does not allow seminal qualification, requiring detailed knowledge of sperm movement by species, essential information to optimize the nutritional and reproductive management of breeders, and seminal cryopreservation protocols.