Abstract
BackgroundLuteinizing hormone-releasing hormone (LHRH) is an exogenous hormone commonly used to induce spermiation in anuran amphibians. Over the past few decades, the LHRH dose administered to individuals and the frequency of injection has been highly variable. The sperm-release responses reported have been correspondingly diverse, highlighting a need to quantify dose-response relationships on a species-specific basis. This study on the Australian anuran Pseudophryne guentheri first evaluated the spermiation response of males administered one of five LHRHa doses, and second, determined whether AVT administered in combination with the optimal LHRHa dose improved sperm-release.MethodsMale toadlets were administered a single dose of 0, 1, 2, 4 or 8 micrograms/g body weight of LHRHa. A 4 micrograms/g dose of AVT was administered alone or in combination with 2 micrograms/g LHRHa. Spermiation responses were evaluated at 3, 7 and 12 h post hormone administration (PA), and sperm number and viability were quantified using fluorescent microscopy.ResultsLHRHa administration was highly effective at inducing spermiation in P. guentheri, with 100% of hormone-treated males producing sperm during the experimental period. The number of sperm released in response to 2 micrograms/g LHRHa was greater than all other doses administered and sperm viability was highest in the 1 microgram/g treatment. The administration of AVT alone or in combination with LHRHa resulted in the release of significantly lower sperm numbers.ConclusionOverall, results from this study suggest that in P. guentheri, LHRHa is effective at inducing spermiation, but that AVT inhibits sperm-release.
Highlights
Luteinizing hormone-releasing hormone (LHRH) is an exogenous hormone commonly used to induce spermiation in anuran amphibians
Effect of LHRHa dose on spermiation response Urine samples were successfully collected from all individuals at each sampling period (3, 7 & 12 h) post administration (PA), with urine volumes ranging from 2 -152 μL
Peak sperm-release occurred at 7 h post hormone administration (PA) for males administered 8 μg/g LHRHa, while all remaining dose treatments produced the highest number of spermatozoa at 12 h PA (Tab. 2)
Summary
Luteinizing hormone-releasing hormone (LHRH) is an exogenous hormone commonly used to induce spermiation in anuran amphibians. The sperm-release responses reported have been correspondingly diverse, highlighting a need to quantify dose-response relationships on a species-specific basis. Collection of anuran spermatozoa has been facilitated by the removal and maceration of testes from euthanized individuals [3] This method has been widely used because of the ease and reliability at which high concentrations of spermatozoa can be obtained, but research in reproductive biology is favouring the use of non-invasive techniques that can be applied to live individuals [4]. LHRH has been used to induce spermiation over the past few decades the dose applied to individuals, as well as the method and frequency of LHRH administration, has been highly variable [14]. The resultant spermiation responses have been correspondingly diverse, highlighting a need to quantify dose-response relationships
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