why do fish or other underwater creatures yawn in a similar way to humans? If they breathe through gills shouldn’t yawning be done more by flairing their gills wider instead of opening their mouth?
In: Biology
They aren’t really yawning, they’re just breathing. Gills are where the water goes out, not in. Fish breathe in water, then force it through their gills to take in oxygen
Fish do not yawn, at least not the way we do. They do open their mouths sometimes, but that is typically to attract mates or deter aggressors.
Stickleback fish open their mouths sometimes very wide and move their bodies in a way that looks like stretching. Meanwhile Siamese fighting fish seems to be yawning upon seeing another fish, sometimes even of its own species. However, then it jumps into an aggressive attack, which kind of shows that it is not really yawning, even if it looks like that for us.
Siamese fighting fish may look like they are yawning, but they are actually just warning their competitors about an incoming attack.
I’ve seen a few different cases where fish open their mouths wider than usual:
* After eating, to stretch out their jaws and maybe clear food fragments from their teeth?
* When they smell something, I guess cause they want a bigger breath of it to figure out whether it’s food
* Social signaling to other fish, depending on species…but I’ve only seen this from bettas and cichlids
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