Seminal plasma features of Prochilodus lineatus and Brycon orbignyanus throughout two consecutives spawning seasons

This study aims to describe seminal plasma characteristics, detect changes during and between two consecutive spawning seasons (SS), and compare plasma features between two important South American fish species. Prochilodus lineatus and Brycon orbignyanus sperm was collected over two (SS1; SS2). Each season was divided into first and second sampling periods (P1; P2). Thus, the four experimental periods were referred to as SS1P1, SS1P2, SS2P1, and SS2P2. Seminal plasma was analyzed for osmolality, pH, and Na⁺ , K⁺ , and Ca²⁺ concentration. Additionally, sperm concentration, motility rate, and velocities (curvilinear = VCL; straight line = VSL) were determined and correlated with plasma features. In P. lineatus, plasma osmolality was lower in SS1P2, pH was higher in SS2P2, Na⁺ was higher and K⁺ and Ca²⁺ were lower in SS2P1 compared with other experimental periods. Positive correlations were observed between motility and plasma osmolality, motility and Na⁺ , and VCL and Na⁺ . In B. orbignyanus, plasma osmolality was higher in SS2P1 and SS2P2 and K⁺ concentration was higher in SS1P1 compared with other experimental periods; no correlation was observed. Seminal plasma parameters change during SS; therefore, the composition of a sperm extender and artificial fertilization methods should be adapted to maximize fertilization rates.