Australian Lizard Moves From Egg Laying To Birth Giving

Posted in News | December 2, 2010 | Comment Now

This is perhaps an example of evolution being caught in the act. Scientists are baffled by the fact that one species of the Australian lizard that used to lay eggs has now abandoned the act. It is now giving live births.

The yellow-bellied and three-toed skin is said to be found around the warm coastal lowland areas around New South Wales. They have always been known to lay eggs in order to reproduce. However, a startling revelation has been that the giving birth to its young ones.

There have been only two other modern reptiles who have been capable of this phenomenon. This would include another species of skin and a lizard from Europe.

According to records maintained about species evolution, it has been seen that almost a hundred lineages of reptiles have independently made the transition from laying eggs to giving birth. In today’s date, only 20% of them are known to give birth to their young ones.

Given the fact that these skinks are indulging in dual behavior (some are laying eggs, while others are giving birth); the scientists are excited about researching them. This is a rare opportunity. If they get a chance to study the differences among these populations, they will be able to put together the subtle nuances of this transition from one style of birth to another.

One of the biggest mysteries surrounding such a transition is about how the young ones get their nutrition and nourishment before they’re born. When it comes to mammals, there is the placenta in place, which is what connects the fetus to the uterus wall. This will allow the baby to take up the nutrients and oxygen that it needs from the blood of the mother; and there is also a provision for passing back the waste.

In some reptiles and fish, there is a mix of both the birth styles. In such cases, the mother will form eggs within her, but she will retain them inside her until the very end of the embryonic development. The shells of the eggs have been seen to thin out so dramatically that the embryos can breathe through it. Eventually when the babies are born, they’re covered with membranes, and these membranes are the only proof that the shells ever existed.

In the case of the mothers who have recently turned from egg-laying to birth giving, there has been proof to show that they secrete calcium from the uterus. This is what gets incorporated into the embryo. Experts point out that this is the early stages of the evolution of a placenta.

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