It’s an example to illustrate the concept. The submarine has more extreme density variations than a biological creature: the metal parts are much more dense than water, while the air is much less dense, while the human is of similar density. So the human can experience very little buoyant force even if the sub as a whole is neutrally buoyant. The same principle applies to internal organs, just less so.
We can. But we also get confused at conflicting visual inputs, and it wouldn’t surprise me if “light source equals up” is almost as ingrained in us as it is in fish. So the sensation of gravity might be overwhelmed by these other things for cave divers or other examples.
I don’t know what would happen with an octopus. Invertebrates might do better in this environment due to being a little more homogeneous than vertebrates. Worth an experiment!
Even out of water, humans are notoriously unable to maintain level flight in an aircraft for even a few minutes without a visual horizon, so I find it quite plausible that we might be able to feel these internal forces in water without being able to “use the information” from the forces to orient ourselves.
But I think the hypothesis is still valid that for aquatic creatures these internal forces can be much less than 1g, so they might find it easier than terrestrial creatures to adapt to 0g.
Agreed. And in fact this thread was spawned from a post where I wondered the same thing. Humans need gravity (or a simulacrum) just to maintain decent muscle mass, since our muscles are constantly working against our weight. That doesn’t apply to a creature with zero weight. Still, there are going to be differences, and we need more experimental data to say how relevant they are.
Humans can get disoriented in water without visual references in large part because our vestibular system mostly detects rapid changes in acceleration (jerk), and we use visual sense and proprioception for orientation, which are attenuated when diving (both because of the pressure of the water and all of the gear). (We teach divers who feel disoriented to actually look at the bubbles which always go up to get correct orientation.) This makes sense because we spend the vast amount of our working time upright. Most fish, on the other hand, are able to maintain orientation by the use of buoyant sensation alone.
Shrimp are bottom-feeders which scuttle along the seafloor; I don’t know if they would find freefall conditions problematic but they’d be challenged to feed. Octopuses and other cephalopods would probably be most adaptable because they don’t seem to have much difficulty in various orientations and as noted above have a means of propulsion that doesn’t really rely on pressure gradients or buoyancy.
No, the ‘sensed acceleration’ in the water on Earth is always 1 gee even if the water is supporting all of the weight external (true neutral buoyancy). Some large aquatic animals use distributed buoyancy to help support their weight in the ocean (and cannot live long when landed) but nearly all fish and aquatic mammals strongly prefer to maintain an upright orientation even in abyssalpelagic regions where no light penetrates. This is not to say that a fish cannot live in a freefall condition if provided with aerated water and sufficient nutrients, but it would not be a comfortable environment or one that they are naturally adapted to.
There’s been a colony of turkeys in my neighborhood for at least ten years – the street was laid out in an almost circle, with the lots being pie-shaped wedges, wide on the street, tapering away atop a useless, scrubby, rocky hill. The turkeys live atop the hill, and come out and wander about the yards looking for food/water/whatever turkeys crave pretty much every day. We see them perched on fairly tall tree branches late evenings/early mornings, so they get up there somehow, and I’ve never seen any ladders in the area, so…
You would also have to realize that the turkeys being yeeted from a helicopter have to be adults from a domesticated breed that are too hypertrophic and heavy to fly.
If they had been wild turkeys, it wouldn’t have turned out to be a poultry bombing.
Ants, of course.
