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Okay so I get that for flexibility I need no bones. My octopeople do live on land so they do have lungs. But they are more amphibious than we are.

So here is my proposed life cycle:

Pregnant octopeople regularly go in the water and long distances on land to make sure they get enough food for their baby to develop properly. Nursing isn't all that useful if you are amphibious so over time breasts have become vestigial, like the only reason for them is to let others know that it is a female they are looking at.

Labor isn't all that hard for the mom because she gives birth in the water. The baby goes up for air and is pretty much independent from its mom. When the baby gets to a certain age, it starts first crawling out with all its suckers on the land. Over time, it learns to balance on only a few suckers on each lower tentacle. Then it is able to walk on its lower tentacles.

That sounds good enough in terms of development but still questioning how the organs would adapt. I guess there could be some mechanism to inflating the GI tract before squeezing through a small space or while squeezing through a small space. And I mean the octoperson could make sure its bladder is empty before squeezing through a small space. Blood vessels and nerves would most likely be cushioned by fat and not be compressed so much because all the fat surrounding it would spread out that force and have elasticity to push back against the compression forces.

But how would the brain be protected? Smaller brains that connect to each other with long neurons to allow for just as much processing or more?

And what about the heart? I know it can withstand a lot but if for example a baby octoperson the size of a newborn human baby squeezed through an area as small in diameter as the birth canal is in its unstretched, unaroused state(which is less than an inch), wouldn't the heart just stop? How would oxygen be transported while the heart stops? Spiracles like what an insect uses to breathe?

And what about the lungs? I mean I guess oxygen could be absorbed into the blood through the skin like in frogs and other amphibians but how could lungs themselves handle the pressure? Maybe they regenerate their lungs so every time they squeeze in a small enough space, those lungs die off, the materials are recycled and while the new lungs form they have to not exert nearly as much because they only would be breathing through their spiracles and/or skin. Thus the water would be a better place to be when the lungs are regenerating than land.

And I'm also wondering how big of a space a pregnant octoperson could squeeze through safely. I know it depends on the stage of the pregnancy but I could imagine that squeezing through too small of a space while in the second or third trimester could cause preterm labor due to all the pressure on the expanded uterus.

So are my proposed adaptations such as regenerating lungs and inflating the GI tract plausible? What would prevent the spiracles from being able to distribute oxygen sufficiently while the heart is stopped for however long it takes to squeeze through a small space?

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  • $\begingroup$ Human babies have bones AND can pass through the birth canal without their heart stopping. $\endgroup$ – L.Dutch Apr 11 '18 at 5:16
  • $\begingroup$ But those bones in a human baby are mostly cartilage and have soft spots whereas if I am going for flexibility here, they would have no bones at all and thus would be at higher risk of their heart stopping. Plus, the birth canal when a human baby passes through it is larger in diameter and more elastic. $\endgroup$ – Caters Apr 11 '18 at 17:09
  • $\begingroup$ Consider that the compression involved with squeezing through this small space could well be evolved into the mechanism of fuel exchange. You have 8 limbs that allow for 8 or more cartilage-lined trachea, the cartilage can be formed of platelets 'designed' to overlap and restrict as compression or shear forces are applied. Not magic, it's a function of the peristalsis mechanism the octopeople normally use compress the internal dimensions in order to breathe. Give the cartilage walls one or two 'spines' and you have a whole-body brain. $\endgroup$ – Giu Piete Dec 2 '18 at 14:27
  • $\begingroup$ then take some tips from the electric eel, but use the power for electrolysis, hydrogen distribution along a dermal membrane reduce muscular requirements (or a natural flamethrower, heh) and oxygen is catalysed from atmospheric or cellular free water. $\endgroup$ – Giu Piete Dec 2 '18 at 14:30
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Spiracles and skin breathing both put extreme size limitations on an organism, far, far smaller than newborn. They work even worse underwater.

Mammalian lungs require a rigid torso. Even avian lungs do to an extent, so your creature has no way to breath.

Balancing implies they can actually support their mass in that position, which without bones they can't. Without hard tissue for the organs to hang from they will squish the tissue below so hard blood will not be able to circulate. Squeezing the lungs is a non-issue compared to cutting off the blood supply to their lower extremities.

Sorry, if you want octo-people that live on land and are bigger than an insect, they need bones or something similar. You could give their tentacles a support structure like the ambulacra in starfish - have them go part way down the tentacles and can disperse the weight when attached to the rest of the skeleton without eliminating the to much flexibility. Think of the ambulacra like a spinal column with lots of very short interlocking vertebrae.

Mice can get through any opening that can fit their heads. Octopus can squeeze through anything that can fit their beak. These creatures will be able to fit through anything that can fit their torso or head depending on how wide you make their torso.

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