Spotted snow skink (Carinascincus ocellatus) - multiple parks

​Application for Scientific Permit – Available for Public Comment


Public comment on the following application for a Scientific Research (Fauna) Permit is open until the 10th of April 2024.

Applicant: University of Tasmania

Species/Taxon: Carinascincus ocellatus, spotted snow skink

Location: Ben Lomond National Park, Bicheno, Mt Wellington Park, Margate, Lake Echo (Lake St Clair National Park), Lagoon of Islands, Tooms Lake, Ross

Title of research: Sex chromosome differentiation in spotted snow skink

Aim of project: 

Climate change is an increasing threat to global biodiversity, and Australia is expected to experience among the highest extinction rates in the world. Species whose sex determination is influenced by temperature are particularly at risk, as extreme temperature changes can cause (i) debilitating sex ratio skews, and (ii) the emergence of individuals with discordant genotypic and phenotypic sex (so-called ‘sex-reversed’ individuals), with potentially poor fitness. It is still unknown if all species with a temperature-influenced sex determination are equally threatened by climate change, and it is becoming urgent to determine if certain biological features (genetic or behavioural) increase the risks of extinction, to identify the most vulnerable taxa. This project aims to test the importance of one of the sex chromosomes in this context by understanding how the degree of sex chromosome differentiation (i.e., how much X and Y chromosomes are genetically distinct) can impact a species. 

The premise of this project is that when sex chromosome differentiation is greater, the fitness of individuals whose sex has been reversed by temperature will be worse. This is because the process of sex chromosome differentiation involves the partitioning of genes on chromosomes that favour a specific sex. For example, in humans the genes for sperm production are restricted to the Y (male specific) chromosome. 

In this study we will investigate the live-bearing spotted snow skink (Carinascincus ocellatus). This species has been studied for over 20 years at the University of Tasmania and has led to major advancements in the field of sex determination research. Historically, two populations, at the climatic boundaries of the species distribution range (coastal/sub-alpine) have been studied (Orford, Central Plateau). In both populations, sex chromosomes are evident, analogous to the human X and Y sex chromosome system (males XY, females XX). However, the coastal population displays drastic inter-annual sex ratio variation, while in the sub-alpine population, the sex ratio is even and stable across years. This difference could be explained by variation in the production and survival of ‘sex-reversed’ individuals in these populations (XX embryos can develop as males under certain incubation temperatures in the lab). Additionally, these populations also vary in the degree to which their X and Y chromosomes are differentiated, with the coastal population having less differentiated chromosomes. Therefore, the lower sex ratio skews in the subalpine population could reflect lower production and survival of sex-reversed individuals because they would have lower fitness given their greater sex chromosome differentiation.

Justification: 

In addition to addressing fundamental knowledge gaps, the proposed research has strong urgency and translational relevance for conservation of biodiversity. Climate change is identified as a significant extinction risk for species with sex reversal via the production of highly biased sex ratios. For example, high temperatures can override apparently stable GSD systems in central bearded dragon, which results in all-female offspring with only a <1°C increase in incubation temperature. Therefore, there is an urgency to understand the molecular mechanism that enables sex reversal, and hence exposes species to risk of sex ratio shift with climate. In addition, understanding the impact of different sex chromosome morphologies will provide an understanding of how populations can react to changes in the environment.

Maximum likely numbers of individuals involved: 166

Activities undertaken and methods:
FIELD-CAPTURE
Animals are captured by “fishing” or “noosing”. The fishing technique involves baiting the end of a fishing rod with a mealworm (tied on with cotton, no hooks are used). This is presented to lizards, which bite the mealworm and the lizard is raised into a bucket. With the noosing technique, a loop of fishing-line is placed around a lizard’s neck and pulled taut, and lizards are lifted into a bucket (this procedure is a common method for capturing reptiles).
Animals will be sexed in the field by hemipenes eversion, as we seek equal numbers of males and females for each species.
A subset of individuals captured are only required for DNA analysis, and will be tail-tipped in the field
TAIL TIPPING
DNA sampling is possible through taking a small tissue sample from the end of skinks’ tails. These species naturally lose their tails and regenerate them in natural situations – there is negligible blood loss (usually none) as the procedure utilises their natural response to autotomise their tail which is preceded by blood retraction to the body and shutting down of the nerves. Thus tail-tip samples are the least invasive way of obtaining tissues. DNA sampling is crucial to meeting several aims of the study.
EUTHANASIA
6 individuals from a lowland population will be sacrificed for RNA-sequencing.

Fate of animals: All but the 6 individuals sacrificed will be returned to their site of capture

Likely impact on species involved (including any by-catch): No impact on the species



Contact

Scientific Research Permits

Environment Division
GPO Box 44,
Hobart, TAS, 7000.