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I am designing a starfish-like alien and I am wondering if a tube feet like design would work for a large land-dwelling creature?

The creature unlike starfish has strong muscles in its limbs which allow it to leap and crawl at speed but it can also glide across the ground using just its tube feet.

The creatures weight is around 100 kg and is about 3 meters wide. I envisioned them at times with all limbs raised up as their eyes are at the tips of their limbs, so at those times only a small amount of tube feet which are on the underside central body segment and base of the limbs will be supporting the whole weight, but this part is less important than just having functional tube feet.

As it is land-dwelling it wont use the same mechanism of hydraulic pressure the push water to contract the foots muscle but could that mechanism be replaced by something like the papillae of cephalopods skin or another design of muscular protrusions? Would something like papillae or other muscular protrusions acting like tube feet be able to hold up the creatures weight on land and be a main form of locomotion?

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    $\begingroup$ Q: you're talking "alien" and at the same time "terrestrial", which refers to planet Earth. Do you mean "terrestrial" or "land-dwelling", that is an animal living on land ? Also, I would suggest adding a Creature Design tag to this question. $\endgroup$
    – Goodies
    Commented May 5, 2022 at 21:00
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    $\begingroup$ @Goodies I thought terrestrial meant living on dry land as well as being from earth but I have corrected it to your suggestions. $\endgroup$
    – Alan Davies
    Commented May 5, 2022 at 21:17
  • $\begingroup$ @Goodies: The word "terrestrial" has several meanings. The meaning of "related to the planet Earth" (as opposed to extra-terrestrial) is only one of them; another very common meaning is "living on land" (as opposed to aquatic, for example). Other meanings include "rocky" (speaking of planets), and "using ground-level transmitters" (speaking of broadcasts, as opposed to satellite or cable). It was a perfectly understandable word in the context. $\endgroup$
    – AlexP
    Commented May 5, 2022 at 22:18
  • $\begingroup$ @AlexP I am not anglophone, and I must admit Google, Merriam Webster and Wikipedia all agree on the ambiguity you refer to, but "land-dwelling" makes a clearer distinction. Reading this question, I got confused reading the word "terrestrial" which translates in my language as either "aards" (common term for Earth-related) or "terrestrisch" which is a fairly unknown term and also ambiguous. There is no need for ambiguity? $\endgroup$
    – Goodies
    Commented May 5, 2022 at 22:27
  • $\begingroup$ Can you say why such a design should not work in reality, and then why that should be hard to overcome in a built world? What's wrong with muscular protusions or tube feet? $\endgroup$
    – Robbie Goodwin
    Commented May 15, 2022 at 22:15

1 Answer 1

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Consider blood pressure. Typical human blood pressure peaks around 120 mmHg, but giraffes for instance can have blood pressures peaking at 300 mmHg, or 5.8 psi. If papillae were pressurized by this blood like a corporus cavernosum, 38 square inches of contact area are needed to support the 100 kg body (apologies for mixed units here).

As a sanity check, the area of a 5-pointed star with 3 meter diameter is about 522 square inches. So only 7.3% of the bottom of your starfish need be in contact with the ground to be fully supported by an arbitrary-but-reasonable blood pressure. This seems to be a reasonable density of papillae, so I would say yes, this is possible

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