Thursday, 19 August 2010

Some really unexpected scientific results

This posting on the Discover Magazine blog discusses two really interesting developments, one about fish and the other about fossils.

The first article is about the relationship between billfishes, like marlin and swordfish, and flatfishes like plaice and flounders.  A guy working in Canada was trying to sort out the relationship between the billfishes and their supposed nearest relatives, the tunas, so he did some DNA sequencing, which is the obvious thing to do these days.

To his amazement, the two groups are only distantly related, some of their similarities work in quite different ways.  For example, both groups can selectively warm up parts of their bodies, certain muscle blocks and their eyes, to well above ambient temperature, which is how they manage to swim so fast.  But the way the warming up works is quite different in the two groups.  <confession>I just believed what it said in the blog posting, rather than doing any research myself to confirm that.</confession>

And the jaw-dropping result was that the flatfishes and jacks are billfishes nearest relatives.  The 'and jacks' bit does make sense.  We were re-watching Blue Planet the other night and saw jacks herding a shoal of small fishes against a coral reef and then picking off the stragglers in much the same way that billfish do with a bait ball in open ocean. But flatfishes?

The other topic in the posting is about a guy who found a fossil leaf with some curious cut marks across some of the veins.  Sometimes insects will cut across the veins of a poisonous leaf to drain out some of the sap, leaving the rest of the leaf rather more tasty, but these marks match marks left by some of today's ants when they're about to die from a parasitic fungus.

This fungus infects the ant and, in the victims last few hours, changes its behaviour.  It makes the ant find a leaf just the right distance above the ground and bite into it across a vein.  The ant then dies, jaws still locked onto the leaf, the fungus sends out a fruiting body from the ant's head and the spores are scattered onto other ants scurrying by.  And this leaf is 48 million years old.


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