Arrested development as turtle's power thrills scientists
A turtle at Gnaraloo Station in Western Australia. Photo: Fleur Bainger
RESEARCHERS have established how female turtles can hold on to their eggs - laying them only when the conditions are right.
Some species of freshwater turtle can hold on to their eggs for up to two months, while sea turtles can delay laying eggs for between seven and 10 days.
Reproductive and developmental biologist Anthony Rafferty said embryo development stalled in all species of turtle when the egg started to form in the mother's reproductive tract.
Turtle hatchlings make their way to the sea. Photo: Fleur Bainger
To establish how they do it, Dr Rafferty and colleagues studied four species of Australian turtle - the western oblong, eastern longneck, Murray River and green sea turtle.
The team discovered the egg-carrying female had the unique biological ability to create a low-oxygen environment for the developing embryos.
This allowed her to wait to lay her eggs on land until conditions were right, giving her young the best chance of survival.
Females try to nest when they know there will be a spike in food for the young, usually in spring. The western oblong turtle only nests when there is low air pressure, indicating rain is on the way to soften the ground for nest building.
Dr Rafferty said he was surprised how low the oxygen levels were inside the reproductive tract. ''It was really fascinating,'' he said. ''We couldn't believe that it even supported the embryo development to that stage, let alone the mother's tissue.''
Working with Healesville Sanctuary vet Franciscus Scheelings, the researchers used an endoscope and an oxygen sensor to observe the oxygen levels inside four different species of pregnant female turtles.
They found the female secreted a mucus-like substance in the reproductive tract, which coated the eggs and lowered oxygen levels to effectively put the embryos' development ''on hold''.
Published in the American Society of Naturalists, the research could have broader implications, especially for species such as the critically endangered leatherback. The largest of all living turtles, the leatherback has a poor hatch rate with more than half the eggs laid in the nest failing to hatch. ''This research may certainly help improve captive breeding or artificial incubation of eggs,'' Dr Scheelings said.