Wednesday, November 3, 2010

Girl Power: Female Boa Constictors Reproduce Alone

New evidence shows that boa constrictors can reproduce without sex. But one boa constrictor had babies asexually and the old-fashioned way. Her sexually produced snake (left) is shown beside one of the asexually produced females (right). [NCSU]

Scientists in the US have made a discovery which revolutionises the way we thought reptiles reproduced, by showing that female boa constrictor snakes can produce offspring without mating.

It was found that a so called "super mom" could produce large litters of all-female babies which show no evidence of male influence. The offspring has no genetic fingerprint that males were involved in the reproductive process and they all retained the distinctive recessive colour mutation.

This is the first time that asexual reproduction (producing offspring without mating) has been seen in boa constrictors.

Dr. Warren Booth, lead author of a paper just published in Biology Letters describes why boa constrictors may use both sexual and asexual forms of reproduction: "Reproducing both ways could be an evolutionary ‘get-out-of-jail-free card’ for snakes. If suitable males are absent, why waste those expensive eggs when you have the potential to put out some half-clones of yourself? Then, when a suitable mate is available, revert back to sexual reproduction.”

Whereas mammals are well-known for having X and Y sex chromosomes (males have one X and one Y; females have two X chromosomes), snakes have Z and W chromosomes.

Male snakes have two Z chromosomes and females have a Z and W. The female babies produced asexually in this study all had two copies of the W chromosome. This has never been seen before and was previously believed to be impossible.

Booth pointed out that the "super mom" snake had the opportunity to reproduce the "old-fashioned way", as there were a number of male snakes available. He also doubts that environmental changes triggered this rare change in behaviour in the snake.

Further studies will look at the development of the new offspring to determine how they reproduce when they reach sexual maturity.


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