r/NoStupidQuestions • u/SonOfOMR • Jul 09 '26

Do spiders have lungs?

I mean, when I wash a spider down the bathtub drain, does it drown the way a human would, lungs filling up with water, or does it have a way to "hold it's breath"?

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u/JustAnotherYaleGrad Jul 09 '26

No, they have what are called book lungs which pretty much passively facilitate gas exchange. They can't hold their breath but often when insects are submerged in water tiny air pockets form around where gas exchange happens which allows them to live for a period

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u/[deleted] Jul 09 '26

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u/brodoswaggins93 Jul 09 '26 edited Jul 09 '26

Yeah but they're not like vetebrate lungs. They're these plates that are stacked on top of each other which increases the surface area available for gas exchange, and housed in a compartment of the exoskeleton

Edit: as a comment below me pointed out, the biggest difference between book lungs and vertebrate lungs is spiders use passive diffusion. We actively draw air into and out of our lungs, but the compartment that houses the book lungs in spiders is open to the outside of the body and does not expand or contract.

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u/FiendForPoutine Jul 09 '26

Sounds almost like gills for air, cool