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Ms Simpson and dunnart.

Some marsupials are born so small they don't need lungs for their first few days of life. Understanding how the lung develops in newborn marsupials is part of awardwinning research by a PhD student in Zoology.

Shannon Simpson recently won the Scholander Prize, the highest award for PhD or postdoctoral research in comparative physiology from the American Physiological Society, and a Journal of Experimental Biology (JEB) Travelling Fellowship.

The awards recognise her research on lung structure and function in the fat-tailed dunnart (Sminthopsis crassicaudata), a small nocturnal insect-eating marsupial.

The dunnart is born after just thirteen and a half days gestation – no bigger than a grain of rice. The immature newborn cannot regulate its body temperature, though the warm pouch of the mother removes the need to do this.

Thanks to the La Trobe research, scientists now know the animal also does not take its first breath until about four days after birth.

'This is remarkable. The newborn marsupial is to date the only example of a mammal that does not rely on its lungs for gas exchange,' says Ms Shannon's supervisor, Dr Peter Frappell.

Dr Frappell's work on newborn marsupials has challenged ideas of respiration in mammals and fascinated many with its insight into life in the marsupial pouch.

Why is it born so young? 'The answer,' he says, 'is that in general, the marsupial placenta is poorly interfaced with the uterine wall and it is possible the foetus has trouble obtaining enough nutrients and oxygen. Marsupials, therefore, are characterised by development in the pouch and prolonged reliance on lactation to raise their young'.

Because most marsupials are born so small – a mere 15 milligrams in weight in the case of the dunnart – they have a large surface area to volume ratio which favours gaseous exchange through their skin.

'They also have a very low metabolic rate and therefore if the skin is sufficient for gas exchange, the newborn dunnart doesn't need to have functioning lungs,' he adds.

In larger newborn marsupials some gas exchange also occurs through the skin. The tammar wallaby, for example, weighs in at 400 milligrams and obtains one third of its oxygen this way.

When Dr Frappell first discovered that the dunnart breathed through its skin, his research captured the public's imagination. How could a newborn marsupial survive without lung function? Did its apparent prematurity provide clues that could help explain lung development in other mammals – and possibly help in understanding problems associated with breathing disorders in preterm babies?

The questions Dr Frappell had to field were a measure of the media's faith in scientists and their willingness to follow them down the path of speculation. Although he commented on these issues, Dr Frappell stresses that the dunnart research is more concerned with fundamental questions in respiratory physiology.

'We are trying to understand how the respiratory system develops,' he says. 'Shannon has taken this work a step further by integrating the physiology with morphology and functional genetics.' She has been involved in 3D reconstruction and calculations of the lung surface area of newborn dunnarts with colleagues from Monash University using Japan's SPring-8 synchrotron facility.

In conjunction with the Victorian Department of Primary Industries, she is also looking at which genes are expressed in the early stages when the immature lung is no more than a collection of simple air-sacs.

The JEB Travelling Fellowship enabled Ms Simpson to further her work in Professor John Greer's laboratory in the Centre for Neuroscience at the University of Alberta, Edmonton, Canada.