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Fossilised mosquito meal

Sun, 20th Oct 2013

Chris Smith

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Blood from the last meal consumed by a mosquito 46 million years ago has been identified inside a Fossilised Culiseta species female mosquitofossilised mosquito found in Montana.

Writing in PNAS, Dale Greenwalt and his colleagues at Washington DC's Carnegie Institution, initially used X-rays to examine the remains of a female mosquito preserved in a layer of fossilised mud that would have rested on the floor of a pond in what is now north-western Montana.

Consistent with the mosquito's engorged appearance, the X-rays showed a strong signal corresponding to iron, which would be in keeping with the insect having binged on a blood meal not long before it presumably drowned in the pond.

Next, the team cleaned away the surface of the fossil to remove overlying material, and then used a technique called "time of flight secondary ion mass spectrometry" - ToF-SIMS - to probe the chemical composition of the insect itself.

In this system, charged particles are fired at a surface where they knock out molecules that can be sucked up and identified by the analyser.

Stable molecules called porphyrin rings, of which haemoglobin is one, were detected, giving a signature closely matching pig blood tested as a control.

This suggests that blood has been preserved within then fossil, and that some of the chemicals sucked up 46 million years ago by the now-fossilised female mosquito are still preserved within its remains today.

Ironically, this paper, which comes 20 years after the Hollywood blockbuster Jurassic Park in which dinosaur DNA was recovered from mosquitoes preserved in amber, is actually the first such description of a blood-engorged fossilised mosquito!

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It's Sunday :) Skyli, Sun, 20th Oct 2013

Well I'll be damned! Mosquitoes eat blood! Who would have thought it?  Not, apparently,



who spent a fortune discovering what everyone else in Washington DC knows.  alancalverd, Sun, 20th Oct 2013

Of course, the article discusses finding iron (hemoglobin) in the blood, not dino DNA, so we may have to wait a few more years for Jurassic Park.

In fact, if the mosquito had blood & hemoglobin in it when it became trapped in amber, then the iron would not be able to escape.  So the cells could decompose while the iron remained more or less in place.  Not to mention, of course, that mammalian RBC's don't contain DNA. CliffordK, Sun, 20th Oct 2013

Yee-haw! Them folks down DC way done gone an' found iron in hemoglobin! Who says good ole America is a bit slow on the uptake? Where's ma dang banjo?

Seriously, though, chaps, we are still frightfully grateful for all that stuff in the 1940's, even if you did turn up late and claim all the credit, as usual.  alancalverd, Mon, 21st Oct 2013

Proving the mosquito had blood in it would be the fist step for later looking for foreign blood components in the mosquito, especially if it can be proven with a non-destructive method. CliffordK, Mon, 21st Oct 2013

Somehow I doubt that even an American mosquito would survive for long by eating its own blood. 
alancalverd, Mon, 21st Oct 2013

I think insects have hemocyanin, while mammals & birds have hemoglobin.

That is why insects give you such nice pretty colors when splattered on the windshield.

Assuming mosquitoes also have hemocyanin, then the difference between the hemocyanin and hemoglobin would make an easy way to distinguish between ancient mosquitoes that have eaten animal blood, and those that haven't.  I assume the technique in the article has also been tested on modern insects.

Oops,
Maybe it is Hemolymph, and may not be used for oxygen transport.  Nonetheless, one would be more likely to find copper ions than iron ions in insect blood.

One still would need to know how long the iron stays in the mosquito bodies after they've had a nip. CliffordK, Mon, 21st Oct 2013

I thought I would look up iron in mosquitoes.  About 87% of the iron is excreted.  However, the remaining iron is distributed to the eggs, and other tissues in the mosquito. 

Even fruit flies have some iron in their bodies.

So, having a little detectable iron may not indicate fresh ingested blood, although having a heavy load of iron may indicate fresh blood.  Or, at least blood that was fresh when the mosquito died.

A control study would help with determining actual proportions. CliffordK, Mon, 21st Oct 2013

Good questions, Clifford; actually, the way they did this experiment (as described in the PNAS paper) was to compare the signals from male and female mosquitoes, reasoning, quite reasonably, that the male (which doesn't consume blood) reflects ion and atomic species signals intrinsic to the insect, while any differences to the engorged female must reflect what she's eaten. They state the relative abundances of the iron and porphyrin signals in the paper. The female has about 8 times more iron coming up. chris, Mon, 21st Oct 2013

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