Sean Williamson

PhD Candidate 

Email –

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Co-supervised by Associate Professor Roger Evans, Monash University

Even though the vast majority of crocodilians and turtles are predominately aquatic, they still rely on returning to land to lay eggs. Other reptilians, specifically the squamates (snakes and lizards), have evolved from egg-laying to viviparity live-birth over 100 times. From my PhD research, I am hoping to contribute new knowledge on the physiological constraints that have prevented the transition from egg laying to live-birth in crocodilians and turtles. I am examining maternal physiology and experimentally manipulating egg incubation environments for several model reptilian species of crocodilians, turtles and squamates.

I will Identify how variation in oxygen availability during incubation affects embryonic development and investigate how oxygen levels in the reproductive tract of the mother varies between each species. I hypothesize that this will provide further evidence that oxygen concentration in the reproductive tract is a crucial constraint restricting the evolution of live-birth