The successful production of "sterbel" hybrids using beluga (Huso huso) cryopreserved sperm

This is the first report of the production of viable "sterbel" hybrids using cryopreserved beluga (Huso huso) sperm. In the present study, beluga cryopreserved sperm were used for fertilization and activation of eggs collected from four females of sterlet (Acipenser ruthenus). Sperm were cryopreserved with the use of a glucose methanol extender with the application of an automatic freezer. The mean sperm concentration of beluga was 1.54 × 10⁹ mL^-1. Cryopreservation did not significantly change sperm velocity and trajectory parameters (VCL, VSL, VAP, LIN, STR, ALH, BCF). Cryopreservation affected only the values of percentage of motile sperm (MOT) and progressive motility (PRG). The frozen/thawed sperm were subsequently used for the fertilization of the sterlet ova. The fertilized and activated eggs from each female were incubated in separate experimental incubation cages in the RAS system (at 15 °C). This experiment resulted in the production of inter-generic hybrids that were incubated until hatching. Experimental hybridization was characterized by 20-35% hatching rates and normal development of "sterbel" larvae. Experimental hybrids were verified using molecular and cytogenetic analyses. All produced specimens were characterized by sterlet maternal and beluga paternal genomes and were diploids with 120 chromosomes. This study presents the procedure of hybridization of the sterlet with beluga cryopreserved sperm that can be applied in sturgeon aquaculture or research focused on the biology of sturgeon reproduction.