Investigating patterns in the spermiation response of eight Australian frogs administered human chorionic gonadotropin (hCG) and luteinizing hormone-releasing hormone (LHRHa)
Exogenous LHRHa and hCG are routinely employed to induce spermiation in vivo in anurans. To date, however, few studies have directly compared the efficacy of these two hormones. The aim of this study was threefold. First to quantify the spermiation response of eight Australian anuran species (Crinia glauerti, Crinia georgiana, Crinia pseudinsignifera, Geocrinia rosea, Heleioporus albopunctatus, Heleioporuseyrei, Neobatrachus pelobatoides and Pseudophryne guentheri) administered LHRHa and hCG. Second, to determine whether variance in spermiation responses is related to a species’ reproductive mode (aquatic vs. terrestrial) or family (Limnodynastidae vs. Myobatrachidae). Third, to compare the quantity and quality of spermatozoa obtained via hormone administration (LHRHa and hCG) to spermatozoa obtained via testis removal and maceration. There was no significant difference in the viability of spermatozoa obtained from hCG or LHRHa administration in any of the eight study species. The sperm viability of samples ranged from 28–84% in C. georgiana and G. rosea, respectively. The hormone that induced the release of the highest number of spermatozoa differed among species, with all five species belonging to the family Myobatrachidae responding better to LHRHa, and the three species from the family Lymnodynastidae releasing a greater number of spermatozoa in response to hCG. Importantly, these results provide the first preliminary evidence that hCG and LHRHa efficacy in anurans may be predicted by phylogeny. Understanding such broad-scale patterns in the response of anurans to exogenous hormones will expedite the application of assisted reproductive technologies to novel species.