Similar developmental outcomes of salamander larvae produced with fresh and cryopreserved sperm: implications for amphibian conservation

Sperm cryopreservation is an important tool for the genetic management of threatened amphibian species within conservation breeding programs. Yet, little is known about the growth and development of offspring generated using frozen-thawed sperm compared to those produced using fresh sperm. The objective of this study was to compare the fertilization rate, embryo development, morphology, and survival of tiger salamander (Ambystoma tigrinum) offspring generated using either fresh or frozen-thawed sperm. Captive male and female A. tigrinum were administered exogenous hormones to stimulate gamete production and release. Eggs were collected from females and fertilized with either freshly collected sperm from captive males or frozen-thawed sperm maintained in the U.S. National Amphibian Genome Bank. Following in-vitro fertilization, egg fertilization rates and early embryo development were monitored through hatching. Larvae from each sperm type were then maintained under standardized rearing conditions and routinely monitored for total length, head width, survival, and development through metamorphosis. Results showed no difference in larval growth (p > 0.42), survival rate (p = 0.72), or size at metamorphosis (p > 0.26) between offspring generated from fresh or frozen-thawed sperm. These findings support sperm cryopreservation as an effective conservation tool for producing viable individuals in amphibian conservation programs.