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Evolution - fingers

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165192.  Thu Apr 12, 2007 7:13 am Reply with quote

Q: What's quite interesting about where the Madagascan aye-aye and the Long-fingered possum stick their fingers?
A: They both use them to pick out insects, larvae and worms from beneath tree bark.

Not that weird, you may think, but these two creatures have very odd fingers. The aye-aye is one of the oddest of lemurs, found on the islands of Madagascar. It has a very elongated, fleshless 3rd finger on each hand, with a sharp, hooked nail on the end with which it rootles around under the loose bark of trees for food.

Similarly, the long-fingered possum of Papua New Guinea has a very elongated, fleshless finger, and does the same thing with it. But it's the fourth finger.

These two animals are not remotely connected on the tree of evolution, but because both their native environments contain no woodpeckers, they have both evolved to fill the niche that's left: a ready source of food. And because evolution often finds similar solutions for the same problem (called convergence), these two creatures have ended up with a remarkably similar adaptaion. It just happens to have centred on a different digit in each case.


Can't find a picture of the long-fingered possum...

Source: many, including Adams/Carwardine Last Chance To See

165193.  Thu Apr 12, 2007 7:14 am Reply with quote

According to a lecture I heard recently, humans (and other vertebrates) didn't always have five digits per limb: it was three and four for a while. I'll dig up some fossil evidence.

165202.  Thu Apr 12, 2007 7:20 am Reply with quote

Chris, I think this one is going to depend very heavily on getting good pictures - I can't make out the ayae-aye one at all. Could you get on to the picture researchers, explain what you're after and see what they can find?

165209.  Thu Apr 12, 2007 7:28 am Reply with quote


165217.  Thu Apr 12, 2007 7:37 am Reply with quote

Ugh! It's Joan Collins!

165235.  Thu Apr 12, 2007 7:58 am Reply with quote

Ooh - well spotted, eggers.

I can see the bony aye-aye finger quite clearly, although I suppose I know what I'm looking for. I'm sure we can get a clearer picture...

Perhaps I can find other creatures that have convergent adaptations. The commonest one is eyes, but there are others that are likely to be similar. The 'fingerprints' on the inside loop of the spider-monkey's tail is another.

165239.  Thu Apr 12, 2007 8:04 am Reply with quote

link to extra-terrestrials

165244.  Thu Apr 12, 2007 8:12 am Reply with quote

LOL. He's even got a 'torch' to see what he's doing...

165370.  Thu Apr 12, 2007 11:43 am Reply with quote

Which links in turn to egg's illuminated earwax device.

165396.  Thu Apr 12, 2007 1:16 pm Reply with quote

It's uncanny, that.

165398.  Thu Apr 12, 2007 1:20 pm Reply with quote

I think a big problem could be the fact that the Long-fingered possum is seemingly camera-shy - or at least doesn't like his picture appearing on the internet.

165399.  Thu Apr 12, 2007 1:27 pm Reply with quote

You know what. Ignore me. That picture which I posted above belongs to a possum, a striped possum to be precise, not an aye-aye. The clue is in the fact that it's the fourth finger that's long.

It's been a VERY LONG day. I think I deserve a beer.

168207.  Fri Apr 20, 2007 7:59 am Reply with quote

We could use other unrelated creatures that have converged together by their ecological niche, and 'way of life':

* Australian Sugar Gliders and North American Flying Squirrels
* New Zealand Kakapos and Eurasian Rabbits
* Thylacines and wolves
* Marsupial mice and (regular) eutherian mice, which are practically indistinguishable.
* Bats and birds.
* Cetaceans and fish.



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