Physiology and biophysics of gas exchange by aestivating snails

Unlocking the mysteries of snail respiratory systems

This research project investigates the exchange of respiratory gases (oxygen, carbon dioxide) and water vapour of pulmonate snails, particularly across the mantle and epiphragm which restrict evaporative water while the snail is aestivating and metabolically depressed during hot, dry (summer) periods.

The diffusion lung of pulmonate snails is opened/closed to gas exchange by the pneumostome during activity, rest and aestivation (summer dormancy).

During aestivation, the aperture of the shell is sealed by the mantle and also by one (or multiple) epiphragms to restrict diffusional loss of water vapour and prevent desiccation. The epiphragm is a mineralised mucous layer that can have a high resistance to gas exchange, but at high humidity its hygroscopic properties decrease the resistance to water vapour exchange.

This project will investigate the dynamics of oxygen, carbon dioxide and water exchange during activity, rest and aestivation, at varying humidity, and with the pattern of pneumostome opening and closing.

This results in a discontinuous gas exchange pattern, akin to the discontinuous gas exchange (DGE) cycle of many insects that is thought to conserve body water during desiccation. You will also use special mixes of air with helium (low density, increased diffusion) and sulphur hexafluoride (high density, reduced diffusion) to manipulate gas exchange rates and examine these diffusional and convective dynamics.

These, or related investigations, would form the basis of your project, depending on your specific interests and skill set. Overall, the project would provide a much clearer understanding of the role and mechanisms of the pneumostome and epiphragm in controlling oxygen, carbon dioxide and water exchange, which has been historically considered to be a passive diffusion consequence of ambient temperature, humidity differential and epiphragm structure, for aestivating terrestrial pulmonate snails.

For more background information, see the suggested readings below.

Research team leader: Professor Philip Withers

I am a comparative animal physiologist, with broad interests in animal structure and function, at the School of Biological Sciences at UWA. My research is focused on the environmental physiology of primarily terrestrial vertebrate animals (amphibians, reptiles, birds, mammals). I am interested in adaptations related to thermoregulation, water and solute balance and metabolism that enable these animals to survive in hostile environments, particularly arid desert environments.

PhD opportunities

Interested in becoming part of this project? Complete the following steps to submit your expression of interest:

Step 1 - Check criteria

General UWA PhD entrance requirements can be found on the Future Students website.

Step 2 - Submit enquiry to research team leader

Step 3 - Lodge application

After you have discussed your project with the research team leader, you should be in a position to proceed to the next step of the UWA application process: Lodge an applicationDifferent application procedures apply to domestic and international students.


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