Wednesday, September 16, 2009

That snake with a leg...?

There's been a report of a snake with a legs and toes in the media recently. The blogosphere has some interesting comments on it, too. Most notably, there is skepticism. Take a look at our snake in question here:

In a comment on Pharyngula, Jerry Coyne notes:
I suspect that this snake ingested a lizard, and that the lizard's limb simply burst through the side of the snake. I may be wrong, and I hope so, because this is great evidence for evolution.

Some graphic images below the fold illustrate why this is not unreasonable speculation.

Snakes sometimes consider their prey choices poorly. Here's a snake with legs and two tails:

(Hat tip to Febble)

Oops! I sort of skipped the first comment at Pharyngula. This commenter noted first that it was probably something the snake ate. Moreover, they note a fact I forgot to mention in my haste: the limb is quite far from where we'd expect the hindlimb to be, if one were to show up. It would be much closer to the tail, not at mid-length of the body. It should be at approximately the same level as the cloaca. There's the unlikely case that it's an atavistic forelimb however, which would raise the issue of where a snake's neck begins or ends.


Anonymous said...

The only problem with the "the snake ate something" is the lack of a high resolution image. This could be easily confirmed/refuted by a dissection of the animal OR a really good high-res image. The location of the limb indicates it to be an example of the "revenge of the prey," along with the scar-like growth around the area. These instances, however, are more often than not fatal for the snake.

If it was something the snake ate which punctured the lining of the stomach, one would expect to see a limb noticeable similar to the limbs of lizard species living in the area.

Another problem with the "snake ate something" hypothesis involves the question of why is it still attached. The immune system will normally destroy such tissue because of the antigens expressed on the surface of the other animal's cells. I cannot see it becoming incorporated (as it appears to be) into the circulatory system of the organism.

A careful dissection or high-res photos could easily solve this.

frank said...

At first I couldn't make heads or tail of that sheep-snake pic, but now that my brain clicked in, that image is fated to haunt my dreams forever.