Help Desk- Any questions? Or game debates?

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smexyfish45
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Re: Help Desk- Any questions? Or game debates?

Post by smexyfish45 » Wed Oct 04, 2017 10:44 pm

So recently I've been hearing this new theory going around about fish evolution, saying that instead of the lung being derived from the swim blatter, the swim blatter is dirived from the lung. The thinking is that bony fish developed lungs to survive in fresh water and that this allowed them to avoid competition from placoderms. While they were freshwater, tetropods evolved. Then the bony fish with lungs radiated back into the oceans after placoderms went extinct, were there lungs developed into swim blatters. Now if we assume that this is true, wouldn't that open the possibility that their were bony fish that never left the ocean and never evolved lung or a swim blatter? Shouldn't they be considered a different clade then the fish that did?

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Prudentia
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Re: Help Desk- Any questions? Or game debates?

Post by Prudentia » Thu Oct 05, 2017 2:19 am

smexyfish45 wrote:
Wed Oct 04, 2017 10:44 pm
So recently I've been hearing this new theory going around about fish evolution, saying that instead of the lung being derived from the swim blatter, the swim blatter is dirived from the lung. The thinking is that bony fish developed lungs to survive in fresh water and that this allowed them to avoid competition from placoderms. While they were freshwater, tetropods evolved. Then the bony fish with lungs radiated back into the oceans after placoderms went extinct, were there lungs developed into swim blatters. Now if we assume that this is true, wouldn't that open the possibility that their were bony fish that never left the ocean and never evolved lung or a swim blatter? Shouldn't they be considered a different clade then the fish that did?
Yeah, more then likely though, they developed from a single structure that served both functions. In more ancient lineages of fish, the airbladder is directly connected to the esophagus, allowing fish to fill and empty through swallowing and burping. Due to some limited vascualrization, they can do some limited air exchange through them. While Coelacanths possess a swimbladders, the ancestors of lungfish and tetrapods developed lungs.
The different lineages just enhanced different aspects of it. Newer fish lineages have their swimbladders not connected. The bladders are highly vascularized, and filled with hydrogen, not oxygen.
Black Rockfish, Sebastes melanops, ~12 inches, of the coast of Newport, Oregon.

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