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atomfullerene t1_jb6jhma wrote

Reply to comment by CrazyisNSFW in What's the original function of recurrent laryngeal nerve? by CrazyisNSFW

> As my understanding, lung did not evolve from gill

Correct. And as a side note, lots of people will tell you that lungs evolved from swim bladders, but in fact it appears that the reverse is true. Early lungs developed as a pouch off the digestive tract in early fish living in low oxygen waters, and only later did they develop into the specialized swim bladders that many fish have today.

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CrazyisNSFW OP t1_jb7sfrq wrote

That's something new for me. Thanks!

Side question though, can fish absorb oxygen with the swim bladder?

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atomfullerene t1_jb80jaf wrote

Some fish have dual use lung/swimbladders, but a great many common fish have lost the respiration use entirely and the swimbladder often has no open connection at all remaining to the digestive tract. These fish often use other methods if they want to breath air, like the labryinth organ in bettas.

Even fish with totally closed swim bladders can absorb gasses from them into the blood...and push gasses into them from the blood. That's how they inflate and deflate them.

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