The Short-term Storage and Cryopreservation of Spermatozoa from Hylid and Myobatrachid Frogs

The short-term storage (at 0°C) and cryopreservation of spermatozoa may be useful for providing gametes for fertilisations performed in programmes for the conservation and management of endangered amphibians. The current study was undertaken to examine the applicability of amphibian spermatozoa storage protocols developed with the cane toad (Bufo marinus) to a wider range of amphibian species, with a view to ultimately using these protocols for endangered species. In Australia, at least 29 species of recently extinct or endangered frogs are from the families the Myobatrachidae and the Hylidae. This study investigated the applicability of short-term storage and cryopreservation protocols developed for cane toad (Bufo marinus) spermatozoa to those of hylid and myobatrachid species. Storage of spermatozoa in intact testes or in suspensions for six days at 0°C showed spermatozoa maintained higher motility in suspensions than those in testes, and hylid spermatozoa maintained greater motility than myobatrachid spermatozoa. However, the protocols for optimal storage at 0°C varied with testis size when spermatozoa were stored in whole testes. Spermatozoa from 13 frog species representing both families were cryopreserved using sucrose as diluent with Me₂ SO or glycerol as cryoprotectants. After cryopreservation hylid spermatozoa showed a greater recovery than myobatrachid spermatozoa and Me₂ SO provided higher recovery than glycerol. The freeze-thaw recovery of spermatozoa was independent of testes weight of the species studied. These results show spermatozoa from the Hylidae and Myobatrachidae may be stored both in the short-term (at 0°C) and long-term by cryopreservation using protocols established for B. marinus.