Cryopreserved Germplasm Case Study: Frog

Amphibian populations worldwide are experiencing significant declines, with many species facing the threat of extinction. To combat this crisis, conservationists have turned to assisted reproductive technologies, including sperm cryopreservation, to preserve genetic diversity and support breeding programs. A notable example is the successful cryopreservation of sperm from the endangered green and golden bell frog (Litoria aurea), leading to the production of reproductively mature offspring.

Researchers aimed to optimize sperm cryopreservation protocols for L. aurea and demonstrate the feasibility of generating viable, mature individuals from cryopreserved sperm. They tested various concentrations of two cryoprotectants—dimethyl sulfoxide (DMSO) and glycerol—combined with sucrose to determine the most effective solution for preserving sperm viability and functionality.

The study found that DMSO was more effective than glycerol in maintaining sperm motility, vitality, and acrosome integrity post-thaw. Lower concentrations of cryoprotectants (1.4 and 2.1 M) provided better protection compared to higher concentrations. Sperm cryopreserved in 2.1 M DMSO exhibited superior performance in fertilizing eggs, resulting in higher hatching rates and the development of several individuals to sexual maturity.

This achievement marks a significant milestone in amphibian conservation, as it demonstrates that sperm cryopreservation and subsequent in vitro fertilization (IVF) can be effective tools for generating viable offspring in threatened species. The ability to produce reproductively mature individuals from cryopreserved sperm offers a means to maintain genetic diversity within captive populations and provides a safeguard against unforeseen catastrophic events that could impact wild populations.

The implications of this study extend beyond L. aurea, serving as a model for other threatened amphibian species. By refining cryopreservation techniques and demonstrating their practical application, conservationists can enhance the genetic management of captive breeding programs and bolster efforts to reintroduce individuals into the wild. This approach not only aids in preserving biodiversity but also contributes to the long-term resilience of amphibian populations globally.