Osmolality and composition of the activating solution affects motility of fresh and frozen Prochilodus lineatus sperm differently

- Activating solution osmolality affects motility of fresh and frozen prochilod sperm.
- Activating solution composition affects motility of fresh but not frozen sperm.
- Prochilod sperm show short period of motility which decreases fast after activation.

Osmolality and composition of the activating solution on motility of fresh and frozen Prochilodus lineatus sperm were evaluated. Sperm was triggered in 11 solutions prepared with reverse osmosis (RO) water (∼0 mOsm kg−1), and glucose or NaCl adjusted to 50, 100, 150, 200 and 250 mOsm kg−1. Sperm motility rate and velocities (curvilinear = VCL, among others) were evaluated in fresh sperm at 10, 30 and 50 s post-activation (spa), and in frozen sperm at 10 spa only. Sperm was frozen under a standardized methodology for this species. Fresh sperm motility was higher in samples triggered in RO (91%), in glucose at all osmolalities (90-92%) and in 50-150 mOsm kg−1 NaCl (88-91%) than that in 200-250 mOsm kg−1 NaCl (74-80%). Motility decreased (P < 0.05) as a function of time after activation in samples activated in RO and in NaCl but not in glucose. Samples activated in 100-250 mOsm kg−1 glucose yielded motility above 80%, at 50 spa. Curvilinear velocity was higher (P < 0.05) in glucose-activated samples (322-357 μm s−1) compared to that activated in NaCl (192-283 μm s−1) and in RO (298 μm s−1). Frozen sperm motility and velocities were similar when triggered in RO, glucose or NaCl and were higher at 0-150 mOsm kg−1 (69-78% motility; 163-208 μm s−1 VCL) than at 200-250 mOsm kg−1 (34-59% motility; 127-168 μm s−1 VCL). High sperm motility with fast velocity for a long period is achieved at 100-150 mOsm kg−1, in glucose solution for fresh sperm and in glucose or NaCl for frozen sperm.