Cryopreservation of Siberian sturgeon (Acipenser baerii, Brandt, 1869) and sterlet (Acipenser ruthenus, Linnaeus, 1758) semen and its influence on sperm motility parameters assessed using a computer-assisted sperm analysis (CASA) system

Summary Using a computer assisted sperm analysis (CASA) system, sperm motility parameters were determined in semen of the Siberian sturgeon (Acipenser baerii) and sterlet (Acipenser ruthenus) prior to and after cryopreservation. Semen was collected from 15 Siberian sturgeon and 15 sterlet males, diluted 1:1 (sperm:freezing medium) in 23.4 mm sucrose, 0.25 mm KCl, 30 mm Tris (pH of 8.0) and 10% methanol, loaded in 0.25 ml straws and frozen over liquid nitrogen vapor. Post‐thaw sperm motility was activated in 10 mm Tris buffer (pH 8.5), containing 20 mm NaCl and 2 mm CaCl2. A significant decrease in the percentage of motile sperm (MOT: from 41.3% to 25.3%), curvilinear velocity (VCL: from 121.9 to 112.2 μm s−1), amplitude of lateral head displacement (ALH: from 10.4 to 5.4 μm) and momentum (MOM: from 4591 to 1038 m s−1) was observed as effect of the cryopreservation process in the Siberian sturgeon semen. A significant decrease in the values of most CASA parameters, including MOT, VAP, VCL, VSL, ALH and MOM, were also noted following the cryopreservation of sterlet semen. In the sterlet, an additional decrease in VAP (from 102.4 to 80.3 μm s−1) and VSL (from 86.8 to 69.8 μm s−1) values was noted after cryopreservation when compared to fresh semen. Unfortunately, the cryopreservation of semen from both species led to a drop in CASA parameters, which are important to the successful fertilization of eggs. MOT and VCL parameters were the most affected in these species. They can be used as sensitive criteria to check changes in motility.