Another, Sometimes, Asexual Vertebrate

When most people think about asexual reproduction they typically think about single celled organism. While rare it has been observed in some more complex animals as well but seems to get even more rare as we get to more derived forms with an occasional appearance in some lizards. Science Daily has an article today about a new paper that discusses asexual reproduction in a Boa constrictor. But there are some weird things about this as well.

Snake sex chromosomes are a bit different from those in mammals -- male snakes' cells have two Z chromosomes, while female snakes' cells have a Z and a W chromosome. Yet in the study, all the female babies produced by asexual reproduction had WW chromosomes, a phenomenon Booth says had not been seen before and was believed to be impossible. Only through complex manipulation in lab settings could such WW females be produced -- and even then only in fish and amphibians, Booth says.

Adding to the oddity is the fact that within two years, the same boa mother produced not one, but two different snake broods of all-female, WW-chromosome babies that had the mother's rare color mutation. One brood contained 12 babies and the second contained 10 babies. And it wasn't because she lacked options: Male snakes were present and courted the female before she gave birth to the rare babies. And the versatile super-mom had previously had babies the "old-fashioned way" by mating with a male well before her two asexual reproduction experiences.

So for some odd reason she choose not to mate with the available males so obviously this is something that needs to be studied more in depth. I would like to see if more cases can be documented and if a reason for her choosing not to mate with the males can be found.