Short-Term Low-Temperature Storage and Cryopreservation of Qihe Crucian Carp (Carassius auratus) Sperm

Qihe crucian carp <i>Carassius auratus</i> is one of the major economic aquacultural fish species in China. Due to environmental degradation and the impact of the reproduction mode of gynogenesis, the wild population of Qihe crucian carp exhibits an extremely low proportion of males. Therefore, it is imperative to develop the sperm preservation technology for Qihe crucian carp. In this study, the indicators, including sperm motility, sperm movement time, and sperm lifetime, were applied to evaluate the preservation effects of various extenders, cryoprotectant types and concentrations, and preservation manners, thus establishing the techniques of sperm short-term storage and cryopreservation for Qihe crucian carp. The results showed that HBSS was the most suitable extender solution, in which the sperm motility reached 93.00%. Under room temperature (26 °C), the sperm motility showed no significant differences across six different cryopreservation solutions. Under low temperature (4 °C), a 15% MeOH solution presented the most effective preservation effects of sperm in the short-term low-temperature storage. For cryopreservation in liquid nitrogen, the sperm activity in 20% DMSO was significantly higher than that in other solutions, representing the optimal cryopreservation solution. Furthermore, it was found that the sperm activity preserved by liquid nitrogen was significantly higher than that preserved by the ultra-freezer (-80 °C), indicating that the ultra-freezer cannot substitute for liquid nitrogen in cryopreservation. This is the first study to investigate the preservation of Qihe crucian carp sperm, providing valuable technical support for both genetic resource conservation and artificial breeding programs.