Ask Ms. Jessica Issue 32 – Tentacles, Tongues, and the Muscular Hydrostat

 (The content for Ask Ms. Jessica comes from real questions from real people sent to AskMsJessica@gmail.com)

Hey Ms. Jessica,

Can you explain to me how tentacles work?

A fairly straightforward question! Tentacles are what’s known as a muscular hydrostat. It is, essentially, a large mass of muscle, or series of muscles, with no skeleton, that gets its form and rigidity by fluid inside it. 

You have a muscular hydrostat on you right now! Yes you! Anyone reading this! Guess what it is? It’s your tongue! Yes your tongue has no bones in it. It’s just a large muscle, and the fluid inside it, the fluid in your muscle fibers that is, is non compressible, that’s where it gets its form.

Now when I say noncompressible I mean noncompressible at physiological pressures. You can, for example, pinch your tongue, but you can’t pinch it flat. Eventually it gets to a point where the fluid becomes to compressed and you feel pain.

But since there is no skeleton inside your tongue it can wriggle around, stretch out, curl back, and take on all different shapes. 

Tentacles and really all muscular hydrostats move by using their muscles to move around the fluid inside. Stick out your tongue right now. You see how the farther it gets the more narrow it gets. That’s because when you decrease the circumference of a muscular hydrostat the fluid inside had to go somewhere. In this case it spreads out horizontally making the tongue, or in this case, tentacle, get longer. 

For a tentacle to bend, one side of it needs to contract while another releases. Curl back your tongue. You’ll notice that you push the bottom part forward while the top part constricts. This is how a tentacle bends as well.

Tentacles can also stiffen, twist, and perform all sorts of gymnastics which, once again, you can perform with your tongue. They are both muscular hydrostats. 

It’s just that the difference between your tongue and a tentacle is the amount of muscle and the amount of fluid contained within, as well the shape of the hydrostat to begin with. Tentacles tend to be much longer and much thicker and have much more fluid in them than a standard human tongue, which equates to more force and dexterity. Note, this is why people who mutate to have long tongues can almost immediately use them as tentacles. They are the same thing!

And in fact, tongues and tentacles are not the only muscular hydrostats out there. The feet of mollusks like slugs and snails are muscular hydrostats, as are the trunks of elephants. Some caterpillars and worms have entire bodies that are muscular hydrostats. You can find muscular hydrostatic systems in your lips, in the feet of a starfish, in eyestalks and antennae, and much much more. It’s a very common biological construct. It’s just that tentacles are the most obvious implementation, is all. 

So if you think about it, mutants with tentacles aren’t really all that strange. They just trade one form of biomechanical locomotion for another that they already have and are familiar with. It was just hiding in their mouth the whole time.

Dr. Jessica Park

AskMsJessica@gmail.com