University of Queensland researchers are investigating a freshwater turtle with the highly unusual ability to breathe through both lungs and 'gills'.
Rheodytes leukops, commonly known as the Fitzroy River tortoise, occurs in only four rivers around Rockhampton in Queensland, and little research has been conducted on the animal since it was first described 25 years ago.
The current research by Zoology Department lecturer Dr Craig Franklin and honours student Toni Priest is expected to shed new light on the animal's biology as well as the likely effects of habitat disturbance on its survival - Rheodytes leukops is classified as vulnerable by wildlife authorities.
The unusual turtle was brought to the researchers' attention by Queensland Department of Environment officer Dr Col Limpus, who also works as an adjunct Associate Professor in the Zoology Department.
'As the turtle is found in medium-deep water with a reasonable current, this suggests it requires well-oxygenated waterways. Concern exists therefore as to whether it can adapt to the gradual damming of its habitat as is occurring in the Fitzroy River area,' Dr Franklin said.
One of only about 16 freshwater turtle species Australia-wide, the 25cm-long Rheodytes leukops feeds on small crustacea, water weed and insect larvae.
Ms Priest and Dr Franklin are particularly interested in the turtle's extraordinary ability to extract oxygen from water through special 'gills' lining its rear passage (cloaca). This ability allows the turtle to breathe underwater for extended periods. When not underwater, the turtle breathes air normally through its mouth and lungs.
Dr Franklin said preliminary results of the study suggested that given optimal water conditions, the alternative breathing method allowed the turtle to spend up to five hours underwater without surfacing for air compared to the maximum two hours recorded for other turtle species.
'While this ability has been described in other turtle species, it is not nearly as well-developed as it is in Rheodytes leukops. In the six specimens we have caught, the cloaca appears as a gaping hole about the size of a five-cent coin opening into an abdominal cavity. When the animal is held up to the light, it appears a good part of the abdomen is missing with gill-like structures hanging inside this large cavity,' he said.
Ms Priest said when the turtle was first described in the 1970s, researchers were astonished to see dirt and sand on the bottom of a tank swishing about near the turtles' cloaca.
'Closer observation revealed water was actually being pumped in and out of the passage allowing the turtle to breathe aquatically,' Ms Priest said.
The project is partly funded by a $1500 grant from Australian Geographic Pty Ltd. These funds have so far been used towards two field trips to catch turtles for closer study at the University. Ms Priest said all turtles would be returned to their environment at project's end.
Ms Priest said a third field trip to the turtles' habitat later this year would involve measuring water temperatures and oxygen levels.
'I am studying how cloacal breathing is affected by certain water conditions. For example, it seems the cooler the water, the slower the turtle's metabolism allowing it to remain underwater longer,' she said.
Dr Franklin said the turtle was yet another example of Australia's 'weird and wonderful animals deserving of closer study'.
'The knowledge gained is vital for species conservation as researchers will more accurately be able to predict the effects of environmental change on animal ecology,' Dr Franklin said.
Ms Priest said catching turtles for the study had been a challenge in itself given the animal's rapid swimming ability and it was only with the help of experienced turtle catchers, John Cann and Tony Tucker, that enough turtles could be accessed for the study.
'The turtles rest in shallow water at night so we walk along banks until we spot them then sneak up and grab them,' she said.
For more information, contact Dr Franklin or Ms Priest on telephone (07) 3365 2355.
