The three-fingered skink is one of the few rare species of “bimodal breeding” in which some individuals lay eggs and others give birth to live babies. But so far, it has not been observed that any vertebrate does both at the same time.
“This is a very unusual discovery,” said Camilla Whittington, of the School of Life and Environment Sciences and the School of Veterinary Science of Sydney at the University of Sydney.
The three-finger skink is native to the east coast of Australia. In the highlands of northern New South Wales, animals often give birth to young animals, but those living around Sydney lay their eggs.
“We were studying the genetics of these tops when we noticed that one of the live females laid three eggs,” said Dr. Whittington. “A few weeks later, she gave birth to another baby, seeing that the baby was a very exciting time!
The sighting will be published in Biology Letters this week, with advanced microscopy of eggshells.
According to Dr. Whittington, who led the study along with Dr. Melanie Laird, a postdoctoral researcher at the University of Otago, and Professor Emeritus Mike Thompson, there are at least 150 evolutionary transitions from egg laying to reproduction. Invertebrates.
“The first vertebrates were laying hens, but for thousands of years, the development of embryos in some species was maintained for longer in the body, until some animals began to give birth.” People generally think of humans and the other mammals that give birth, but there are many species of reptiles that also give birth. “
Dr. Whittington stated that the unusual observation of spawning and live birth in a single litter shows that the effect of three fingers is an ideal model to understand pregnancy. “This makes Australia one of the best places in the world to study the evolution of live birth because we can see evolution in action,” he said.
“In the context of the biology of evolution, being able to switch between spawning and live birth could allow animals to protect themselves,” said Dr. Whittington.
This observation makes it possible to make the three-toed thumb, which looks like a baby with small legs, one of the “strangest lizards in the world,” he said.
Additional research on this small lizard, which seems to occupy a gray area between live birth and egg laying, will help determine how and why species make significant jumps in reproduction.