I’ve been watching Deadliest Catch, which brought on my question. Crabs, lobsters, et al are bottom feeders, correct? And the pressure at the bottom of the sea/ocean is pretty strong, right? So why aren’t the crabs leaking out of their shells when they are hauled topside? Are their shells that strong? If so, why? If they are meant to stay on the bottom of the ocean why are they able to exist up here? And why can’t I make a diving suit out of crab shells and take a walk on the bottom? (Assuming I can’t. Which seems to be a safe assumption since it hasn’t been done yet. And I have no sewing skills to speak of.)
Quick and crude answer: Gas is compressible, liquid is not. (Not perfectly incompressible, but close.) An air-filled bag brought up from the ocean floor would expand dramatically and probably explode. A liquid-filled bag would only expand by a tiny amount.
Fish, in general, have swim bladders. These are gas filled sacs that allow them to adjust their boyancy. If they are down deep the gas in the sac is compressed. If they are brought to the surface too quickly, the gas expands and can rupture the sac.
Imagine your bladder full of air at a pressure equal to 400 feet below the waters surface. Now you rise to the surface faster than your body can get rid of the gas. :eek:
AFAIK, crabs and lobsters don’t have swim bladders.
I shortly may learn otherwise.
:: Assumes an air of authority ::
You are correct, GaryM, Crabs and lobsters, and invertibrates in general, do not have swim bladders.
:: Holds breath hoping nobody with any real knowledge of such things comes in and says “What about the chambered naughtylass?” ::
What about the Chambered Nautilas (Naughtylass)?