Sperm morphology, ultrastructure, and motility in pikeperch Sander lucioperca (Percidae, Teleostei) associated with various activation media

Spermatozoa morphology, ultrastructure, and spermatozoa motility traits were studied in pikeperch (Sander lucioperca) after activation in various media (AM 1 - 45mM NaCl, 5mM KCl, 20mM Tris, pH 8.5; AM 2 - 100mM sucrose, 20mM Tris, pH 8.5; AM 3 - 100mM sucrose, 1mM CaCl2, 20mM Tris, pH 8.5) during a 48-hour storage period. The spermatozoon was acrosomeless and differentiated into a spherical nucleus (head), midpiece, and flagellum. The nucleus length and width measured 1.83 ± 0.03 and 1.63 ± 0.02 mm, respectively. The midpiece was located laterally to the nucleus and possessed proximal and distal centrioles and 2-4 mitochondria. Flagellar length was 33.2 ± 0.90 µm, and a pair of lateral fin-like structures projections was observed. The axoneme consisted of nine peripheral doublet microtubules and a single central pair. After a 24 h storage in all activation media at all sampling times post-activation (15, 45, 90, and 120 s), spermatozoa motility was significantly decreased. Spermatozoa were motile after the 48-hour storage at all sampling times post-activation only in AM 3. After the 48-hour storage, no motile spermatozoa were observed in AM 2 and AM 1 at 90 and 120 s post-activation, respectively. Differences in spermatozoa velocity varied with activation medium during storage. After the 48-hour storage in AM 1 and AM 2, decrease of spermatozoa velocity at 15 s post-activation was observed, while in AM 3, velocity was decreased only after the 48-hour storage. Pikeperch spermatozoa morphology and ultrastructure was found similar to that of most freshwater teleosts, with differences in the arrangement of midpiece, number of mitochondria, and position of centrioles. Viable pikeperch sperm was observed after the 48-hour storage. Motility of spermatozoa was improved by addition of Ca2+ to the activation medium, where higher spermatozoa velocity was observed.