An investigation of sex identification methods in New Zealand reptiles

Abstract

Sex is the fundamental biological difference between males and females, and causes the most disparity in physiology, behaviour and ecology within a species. Techniques that identify sex are useful as they give insight into a species’ population dynamics, aiding the implementation of conservation strategies. For reptiles, sex identification is required for estimating sex ratios of wild populations and ensuring correct captive housing to avoid fighting between conspecifics. This study attempted to identify a genetic technique for sexing the Otago (Oligosoma otagense) and grand (O. grande) skinks as well as the Otago-Southland gecko (Woodworthia “Otago/Southland”). Random amplification of polymorphic DNA (RAPD), using 40 10-mer primers, did not reveal a sex-specific genetic marker in any of the study species. Applying a Y chromosome marker from the lizard Bassiana duperreyi also did not reveal a sex-specific marker in the Otago and grand skinks, nor the Otago-Southland gecko. Further research into the genome of the study species is needed to develop a reliable sex test. This study also involved morphometric investigation into the hemipenes (male intromittent organs) of preserved juvenile McCann’s skinks (O. maccanni). The hemipenes were measured while inverted in the tail base and revealed that males have a significantly larger longitudinal area and length than females. As this study was conducted on preserved skinks the results need to be tested on the everted hemipenes of live McCann’s skinks before being used to sex juveniles. This morphometry study also explored the influence of maternal basking regime in McCann’s skinks on the offspring’s hemipene width, length and longitudinal area. Despite previous studies indicating maternal basking regime can affect morphology in McCann’s skinks, results showed that basking regime did not significantly influence these hemipene measures. In light of this discrepancy, continued study of the effect of gestation temperature on offspring morphometry could clarify this relationship, helping to inform effective conservation strategies including those addressing effects of climate change.