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I have a (moderately) hard sci-fi, in which there is a species (the Bethin) who are based on squids. They have the biological equivalent of a space suit for their skin, and use the mantle cavity as an air tank.

The problem I have is: How will the beaks of the Bethin stay airtight?

  • If the beaks aren’t airtight, the Bethin will be sucked out of their bodies, due to the pressure difference.
  • the beaks can’t be squishy like an O-ring on a mason jar, because they need to be able to rip and tear with the beak to eat.
  • the Bethin need to go into the vacuum of space in order to do things (e.g. build more spaceships, fight, etc.)
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    $\begingroup$ Two questions: 1. Are the beaks being used to eat in a pressurised environment or in vacuum? 2. Are the Benthin (or at least their bio-spacesuits) genetically engineered or naturally evolved? $\endgroup$
    – KerrAvon2055
    Commented Jul 2 at 1:15
  • $\begingroup$ I second @KerrAvon2055's questions. I can think of one or two ways to rationalize an airtight beak if the "suit" is bio-engineered. But it's frankly impossible from a "hard science" perspective if a consequence of evolution. Maybe not impossible - it's just that the problem is the timelines. Starting with a space-faring civilization, by the time the millions of years needed for evolution pass, they'd be a Kardeshev type VII civilization and wouldn't need it (or would have bioengineered a solution long before evolution). $\endgroup$
    – JBH
    Commented Jul 2 at 3:17
  • $\begingroup$ How long do the Bethin spend in space in one trip? There is no such thing as an "air tight seal in the vacuum of space. The ISS loses 2 pounds of air every day. For short trips, this is a minor concern, but for longer trips this could be a major limitation. $\endgroup$
    – Cort Ammon
    Commented 2 days ago
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    $\begingroup$ Why does a squid need air? $\endgroup$
    – Daniel Darabos
    Commented 2 days ago
  • $\begingroup$ @DanielDarabos they need to breathe, presumably. Our earth squid have gills, but they still need to breathe and gills are as useless as lungs in vacuum. $\endgroup$
    – terdon
    Commented yesterday

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just make a diffrent part of the mouth seal.

birds get around the problem by having a flap behind the beak that seals. Crocodiles do the same thing with a palatal valve, which is why they can attak underwater without choking. some burrowing mammals that use their teeth and beavers do the same thing. You likely want it behind the radula, since that is a large part of their food processing aparatus.

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If they have muscles strong enough to keep their mantle from inflating like a balloon and sealing their siphon, they can easily seal such a flap.

If you design it right, it might even seal automatically, with them unable to swallow until they are back in a pressured environment. They are not going to be able to eat in space unless you have a long tube capable of sealing along its whole length anyway otherwise swallowing will blow out their stomach.

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The hard outer beak doesn't need to be airtight and honestly I can't, offhand, think of a reasonable explanation, or mechanism for it being so. What I would suggest is that the beak either has a mechanical lock to keep it closed, similar to what we see in a number of dog species (particularly bull species) jaws that can't reopen under tension, and a softer lining that swells up behind the, locked, hard sections to seal in their air supply. Alternatively have the beak be entirely uninvolved in the sealing process and have a membrane of the same skin material they use for their outer, spaceworthy, carapace that seals their mouth/throat when needed. I can see either of these mechanisms being an outgrowth of moisture retention adaptations that took them out of the sea and onto land (I'm assuming they have a planet-bound origin even if they don't remember it anymore) but a full vacuum seal screams deliberate tampering; either in the form of a long-term selective breeding program and/or out-and-out genetic engineering.

I would point out that there is going to be quite a limit on their space endurance, especially with factoring in physical exertion, unless they have other adaptations, biological or technological, that allow them to carry an unusually large amount of life support with them during their EVA activities. The rule of threes says humans are able to survive 3 minutes without air, three hours without shelter, three days without water and three weeks without food. That is a mix of best and worst case scenarios that is species specific but it makes the point; a creature carrying all it's air internally is going to have sharp limits on how long it can carry on at normal levels of activity.

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Frame challenge: Why would the beaks be connected to the air-circuit?

If their ingestion apparatus is completely disconnected from the air-circuit, and one-way, then there's no air leak when opening the beak, or swallowing.

In fact, instead of leaving the "tube" to the stomach open by virtue of being semi-rigid, and having an air pocket in the stomach, you can just eliminate all air here! Their esophagus is flexible, with muscles clamping down on anything shoved down and pushing it towards the stomach, and the stomach is likewise flexible, shrinking down to only contain its nominal amount of acids once the nutrients are digested and passed down further.

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  • $\begingroup$ stomach acid needs to be a liquid so you need to seal the stomach anyway. also if you are basing it on real squid the digestive track connects to the mantle cavity. $\endgroup$
    – John
    Commented 10 hours ago
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They glue their beaks shut

Probably the most simple and foolproof solution. Before EVA they seal their beaks airtight. After return they dissolve the glue in some solvent, preferably water, or by heating.

As sibling noted there are other serious issues with the biology. Not only the air supply. The prehensile limbs required for any work are poorly solved problem with human space suits too. The internal pressure makes all joints very stiff. Possible solution is to have some kind of biological exoskeleton or armored mandibles or something like that to avoid exposing soft tissues to vacuum.

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  • $\begingroup$ Squids don't really have bones or joints, so stiffening joints shouldn't be a problem. $\endgroup$
    – The_spider
    Commented yesterday

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