Fish out of water: Gene clue to evolutionary step

Jun 24, 2010
Two genes controlling a tissue protein may have played a role in the key period when fish shed their fins and became limbed land-lovers, a study published by Nature on Thursday said.

Two genes controlling a tissue protein may have played a role in the key period when fish shed their fins and became limbed land-lovers, a study published by Nature on Thursday said.

Fossil evidence suggests that around 365 million years ago, fish, or fish-like creatures, emerged from shallow seas, moving onto land with the help of primitive, eight-fingered limbs, which later simplified to five digits under evolutionary pressure.

The newly-found genes control proteins called actinotrichia, whose tough, thin fibrils form a scaffold on which pectoral fins develop.

They were spotted by a team led by Marie-Andree Akimenko, from the University of Ottawa in Canada, as it was scanning development in the , a highly-studied lab animal.

Neither of the genes are present in four-limbed vertebrates known as tetrapods, which became the basis for terrestrial animals, the researchers realised.

When the two genes were switched off in zebrafish through , the fish developed only truncated fins, without bony rays.

The switchoff also unleashed a pattern of gene activity seen in research elsewhere, in the development of limbs and digits in terrestrial animals.

Further work is needed to confirm the theory, as it is unclear whether the fin genes were knocked out to help make the transition to land -- or whether they were eliminated after the transition, as they were no longer needed.

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kevinrtrs
1 / 5 (7) Jun 24, 2010
Fossil evidence suggests that around 365 million years ago, fish, or fish-like creatures, emerged from shallow seas, moving onto land with the help of primitive, eight-fingered limbs, which later simplified to five digits under evolutionary pressure

I'm glad to see it reported as being "suggests" rather than is a fact.
It's only certain expedient human beings who have assumed that they can now make it into a fact.
Why on earth would a fish want to leave it's nice and cosy watery home to eek out a struggle on land? And have to develop lungs in the process? Just how did those lungs develop?
OK, so it could have been the other "fish-like" creature that decided to get out....maybe it already had lungs and was just living in the water, like an otter....

Go ahead heap your scorn. Just remember the word: "suggests".

Rute
4.7 / 5 (3) Jun 24, 2010
Why on earth would a fish want to leave it's nice and cosy watery home to eek out a struggle on land? And have to develop lungs in the process? Just how did those lungs develop?

The waters were full of creatures predating the fish, unlike the case with land, where the largest animals were insects.

At the moment the view on lung evolution is that lungs evolved in the pine swamps populated by fishes because the swamp water was likely to have been low in oxygen, unlike the land.

Lungs are separate from gills, so their evolution didn't hinder the gill funtion. In fact, most fishes today have the evolved forms of ancient lungs, called swim bladders, and some fishes, like mudskipper, have lungs.
lengould100
not rated yet Jun 24, 2010
Yeah eh? See a school of Piranah coming and anybody with even close to lungs is gonna get out of the water fast.
Skeptic_Heretic
5 / 5 (6) Jun 24, 2010
Why on earth would a fish want to leave it's nice and cosy watery home to eek out a struggle on land? And have to develop lungs in the process? Just how did those lungs develop?

This is like asking, why would you want to drive a car or ride a bike, when you have an awesome set of legs already.

Environmental benefit, no matter how slight, is always selected for within nature.

Go ahead heap your scorn. Just remember the word: "suggests".
I'd like you to tell us what meaning of the word you think the context refers to. Please put it in sentence form.
Ethelred
5 / 5 (6) Jun 24, 2010
Why on earth would a fish want to leave it's nice and cosy watery home to eek out a struggle on land
Because sometimes the water dries up and a fish that moves on to another source of water is a fish that lives and reproduces to produce more fish that are similar but not exactly the same.
And have to develop lungs in the process
Lungs could have come first or second. Second seems more likely. Walking catfish don't have lungs but lungfish do. Catfish in general have some ability to extract oxygen from the air.
Just how did those lungs develop?
You don't really like to think about the things you ask about do you? Fish, including catfish and almost all bony fish, have air bladders. Such a bladder is what is called a pre-adaptation. Something that evolved for one purpose can later evolve for new needs.
maybe it already had lungs and was just living in the water, like an otter
Or the lungfish.

Would you like to discuss this? Or just keep going on faith alone.

Ethelred

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