Watching the “High Seas” episode of Our Planet and watching camera crews in these special pressure-resistant submarines capture footage of some pretty fragile looking fish, some of them are pretty sizable too. How are they not crush by the weight of the depths?
In: Biology
Because a submersible is filled with a gas that is at a pressure that humans can tolerate. So the submersible has to withstand an insane level of crushing pressure.
Deep sea fish don’t have a gas filled swim bladder, so there is nothing to compress and crush. Deep sea fish are basically a gel that is the same density of the water. Water doesn’t compress significantly so they can handle that pressure
The same reason why you don’t get crushed be the enormous weight of the atmosphere above you. When you are filled with a fluid, the outward pressure of that fluid equalizes to the inward pressure.
If you filled the submarine with water then you’d basically have the same as a fish, they aren’t hollow on the inside like a submarine full of air.
All organisms are mostly water. Even your individual cells are mostly filled with water. That water inside you and those fish doesn’t compress any more than the surrounding water does.
Gas-filled cavities like lungs and swim bladders on the other hand don’t handle compression so well. That’s why deep-sea creatures have many adaptations to prevent hollow areas in their bodies.
And pressure changes remain a problem. Gas compresses really well. That means that at depth, a body can contain more gas, for instance, dissolved oxygen in the blood, than it can contain at the surface.
If you pull a deep-sea fish up out of the depths too quickly, it’ll die because all of the gas dissolved in its tissues will expand.
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