✧✦Catherine✦✧
did you know? teleost fish maintain neutral buoyancy with their swim bladder, which they pump with gas as they descend into depths. specifically, they can pump it with hyperbaric oxygen at partial pressures of *several hundred atmospheres*
they also pressurize their eyes in the same way
https://journals.physiology.org/doi/epdf/10.1152/physiologyonline.2001.16.6.287
✧✦Catherine✦✧
they do this using the Root effect: locally acidifying their blood within the swim bladder epithelium causes the solubility of oxygen in their blood to drastically drop as the carrying capacity of hemoglobin changes
✧✦Catherine✦✧
i cannot overstate how bonkers this is. commercially, i can buy oxygen in a thick steel cylinder at pressures of 250 bar, or in a composite gas tank at 400 bar. this requires a complex industrial process. both options are lethal when ruptured
fish just... do it whenever, within seconds, to float up or down
✧✦Catherine✦✧
@ignaloidas NO IDEA
Ignas Kiela
@whitequark@mastodon.social how the fuck do they not spontaneously catch on fire
✧✦Catherine✦✧
@SlicerDicer i just checked with the vendor i last bought from and you're right! they offer 150 bar cheap ones and 300 bar Eurocylinder Systems ones. i've edited the post
I am Water
✧✦Catherine✦✧
@SlicerDicer as for the hazards: yes, I understand the environmental conditions and failure modes are not comparable between fish and industrial gas cylinders. that doesn't make the raw number stand out any less
✧✦Catherine✦✧
@SlicerDicer oh yes, they're absolutely insane. at first when I read the paper I noticed they claimed the oxygen pump continues to work at 50 atm and _even that_ is bonkers high. only later I realized they claim it continues to work several times that pressure, which is just unimaginable
I am Water
✧✦Catherine✦✧
@SlicerDicer the cylinders I looked up have a test pressure of 500 bar and rupture pressure of 1600 bar, so from a purely "ideal gas" physical standpoint it would work. but of course high pressure oxygen--even at "only" 1 bar, which is what fish pump into their eyes--is among the most terrifying things that exist on this planet
I am Water
✧✦Catherine✦✧
@SlicerDicer that's true and entirely fair, but it overlooks one important part: that the thermodynamic activity of oxygen is proportional to partial pressure, and would be extremely high in this case
I am Water
✧✦Catherine✦✧
@tomjennings absolutely, yes. it is fun though
tom jennings
The volumes of gas fish deal with are very small. And with low volume comes low absolute force -- it's force per unit area that matters. So some molecular mechanism at a membrane can put tremendous but tiny force on O2 molecules to pass into a bladder, but the circumstances are nothing like a macroscopically large pressure cylinder. This is an apples vs oranges comparison.
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