2010年2月3日水曜日

【Old rotten fish】:by TIMES ONLINE

【出展引用リンク】: http://timesonline.typepad.com/science/

以下の通り
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02/02/2010

Old rotten fish

Fish
Scientists put up with all sorts of discomfort for the sake of curiosity. At a mosquito lab at Queen Mary University London, some of the mosquitoes have to be fed on fresh blood (the malaria researchers' blood). Neuroscientists at the lab I used to work at were constantly taking part in each others pain, drug or gas experiments. But, a study that came out yesterday in Nature, involving the gradual decomposition of fish has got to have been one of the worst.
In order to work out how different tissue structures in ancient fish would have changed during decomposition (and before fossilisation) the team observed the gradual rotting of lamprey fishduring a period of six months.
"When we set-up the experiments we had difficulty finding an out of the way room where any smells would be less potentially disruptive to the rest of the building," says Mark Purnell, who led the research. "Shortly after we started the work a nearby lecture theatre had to be evacuated because of unbearably bad smells thankfully it turned out to have nothing to do with us."

Thankfully too, the grim experiment has thrown up some interesting results. The study suggests that neglecting the effect of decay prior to fossilisation may have lead many fossils to be misinterpreted. Previously, a common assumption among palaeontologists was that as specimens decayed, they lost defining characteristics in a fairly random order. Purnell and his team found that in the case of fish, they tended to lose their most recently evolved characteristics first.
Effectively, as fish decay they are shunted back down the tree of life into an earlier phase of the species' evolution. "As they decayed the more primitive characteristics became more prominent," says Purnell.
The finding is particularly relevant to the interpretation of chordates — fish that lived about half a billion years ago, and featured a characteristic rod-like support structure, which was a precursor to the backbone. With no bone structures to rely on, palaeontologists are dependent on tissue which is vulnerable to decay. The latest study places new stricter boundaries on the extent to which these fossils can be interpreted. A fossil may look primitive, but researchers will now have to also consider the possibility that the fish was just very, very rotten.

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