Evaluation of Russian sturgeon (Acipenser gueldenstaedtii) Semen Quality and Semen Cryopreservation

SIMPLE SUMMARY: The decline in sturgeon populations, including Russian sturgeons, has reached alarming levels, threatening these species with extinction. The requirements for the meat of these fish, caviar and other products used in the textile, medical and food industries are constant or even on the rise. Reproductive biotechnologies seem to be the main solution to these problems, but the many unknowns related to the particularities of the species still place them far from the efficiency reached in some species of domestic animals. The development of fish farms for sturgeons and the intensification of reproductive biotechnologies is the main way in which the natural habitats affected by depopulation can be repopulated and to respond to the consumption and industrial requirements of the population. Our purpose is to contribute with additional novel information on the cryopreservation of sturgeon spermatozoa, as well as the evaluation of semen quality with the aim of developing a cryopreservation technique suitable for commercial breeding facilities. ABSTRACT: The alarming decline in sturgeon populations doubled by growing demands for sturgeon products, urge us to prevent the loss of these species. Fish stocking in natural habitats and developing fish farms are viable solutions, which can be successfully implemented with the help of reproductive biotechnologies. Despite the fact that semen cryopreservation is admittedly an important step for saving the Russian sturgeon, a reproducible standard method with good results has yet to be identified. Sperm quality assessment is essential for quantifying the impact of cryopreservation on spermatozoa. The purpose of our study was to provide additional information regarding semen cryopreservation and semen quality evaluation for the Russian sturgeon. Our study method is based on the use of two yolk-free extenders (with different cryoprotectants: DMSO and methanol) for freezing semen, using a simple freezing protocol. Parameters such as volume, concentration, motility, morphology and membrane integrity were evaluated. In conclusion, cryopreservation of Russian sturgeon spermatozoa using an extender containing methanol as cryoprotectant led to high egg fertilization percentages (72.67 ± 5.4%) even if the total motility values recorded for thawed semen were quite low (18–25%). Additionally, we identified two optimal stains for morphological studies and morphometry (Spermac stain kit and Trypan Blue Solution).