My intelligent alien species looks like a Koosh Ball:

enter image description here

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They use biological "Flashlights" based on bioluminescence which uses sulfur as an oxidizing agent instead of oxygen.

This species lives on a hypothetical moon of Epsilon Eridani b which has a subsurface ocean. They live 50km deep in this ocean, where the pressure is about 0.5 GPa. This happens to also be at the seafloor of such an ocean.

They have 4 different types of tendrils. About half of them are "feelers" which are mainly used for four senses: "hearing" which is really just feeling vibrations, a sense of smell caused by the olfactory sensors which cover the tendrils, magnetoreception caused by a small amount of magnetized iron in some of the feelers which pulls them ever so slightly to the north, and finally a sense of touch which is quite literally just nerves running down the length of all of the tendrils.

Two types of tendrils are dedicated to catching prey: the "sticky" tendrils, which have a slight static charge, pulling in small particles such as bits of algae, and the "twisty" tendrils which are designed to trap larger prey by wrapping around them, and preventing them from intaking vital resources.

The final type of tendril is the "flashlight" tendrils, which have fiber-optic properties and a bioluminescent bulb at their base, which illuminates whatever the tendril is pointed at.

The species also have rudimentary light sensors on the "flashlight" tendrils. At the base of the tendril where the bioluminescent bulb is, there is also a rudimentary eyeball which uses similar mechanisms to that of Earth eyeballs, but with a much lower resolution than a human's, and that don't have any cone cells for detecting color. They only have rod cells which detect brightness.

This is mostly based on real-life evolution and science, along with answers to a few other questions on SE, with only a few deviations that I think are quite plausible.

What do you think? Is my idea plausible given real world science and biology? Don't hesitate to point out flaws just because it's well-developed. I want honest answers.

  • $\begingroup$ Unrelated to your question, but how does "have a slight static charge" work underwater? The (conductive) water would instantly neutralize any static charge ... $\endgroup$
    – brhans
    Commented Nov 20, 2022 at 14:37
  • $\begingroup$ @brhans Oh crap, you're totally right! The static charge would instantly neutralize if it were underwater... oh well, it's not necessarily essential, maybe I can just say they are covered in a layer of an underwater adhesive? $\endgroup$
    – isdi0
    Commented Nov 20, 2022 at 16:00
  • $\begingroup$ I think that the eyes evolved way back when unicellular life ruled the ocean, the bacteria were bioluminescent and developed light-sensitive protein afterwards. This is my idea for how eyes evolved, through random mutation, many of the animals produced bioluminescence with no purpose. When things started to evolve eyes, they were able to see due to the amount of light just cast by the bioluminescent creatures and bacteria. $\endgroup$
    – isdi0
    Commented Nov 20, 2022 at 22:52

3 Answers 3


Your creature is described as a predator but does not have a predatorial body. It looks soft and fluffy and unspecialised.


Your Koosh has only rudimentary eyeballs. This is bad. Your Koosh needs super eyeballs to see its prey in such limited light. It needs eyes miles better than everything else on the seafloor. Otherwise the prey will see the Koosh long before the Koosh sees the prey and then the prey escapes.

If you ever cycle your bike at night you will know what I mean. A strong headlight gives visibility to a dozen metres. But you can see other riders approaching from hundreds of metres away. The advantage is to the prey.

This is the hardest part to believe. That the Koosh can see so well compared to everything else that the prey will not see the Koosh coming.

Powerful eyeballs cost a lot of energy. So specialized predators tend to have only one set of eyes. Not eyes all over their body like your Koosh. If the predator needs to see some direction they just turn their body to point that way. This is easy because they have powerful. . .


or at least some way to move around. This is good for chasing down the prey. You need to find the prey and catch it too. Your Koosh falls down here as well. The thing is far from aerodynamic. It is not clear how the thing moves at all.

Of course it might be an ambush predator like the angler fish. But ambush predators tend to stay in one place. This meshes with using light to attract prey but not with using light to find prey.

I will not comment on using sulfur as an oxidizing agent. Putting complex organisms at the bottom of the seafloor under miles of ice is already a stretch in my eyes. I say if you want bioluminiscent aliens under the ice then put them there. Don't worry about the chemical biology.

enter image description here

How do we fix it?

To make the Koosh ball a predator, stick an eyeball to the front and a tail on the back. To not alter the Koosh design too much, make it radially symmetric. The tail could be one or many flagellums (note: check can large creatures use flagellums) or a skirt. The skirt can be in one part or many parts. We only need flashlight tentacles on the top of course.

enter image description here

Keep the normal Koosh balls in your world. They are grazers. They eat plankton or moss or something that doesn't move. Maybe the predatory Koosh eats them.

Instead of a tail you could also go with a siphon, like an octopus or pyrosome. The Koosh sucks in air and spits it out behind to propel itself. In that case there is a ring of smaller eyes around the siphon and a frilly thing at the back for steering.

enter image description here

  • $\begingroup$ Oh... Yeah, I'm sorta new to this, apparently that design that I came across here was uh... more for scavenger-type sorta organisms... thanks for explaining all the flaws. In that case... back to the drawing board. (Besides, I don't like the idea of life under 50km of water either, it was just what I could come up with, so tidal heating is the answer!) $\endgroup$
    – isdi0
    Commented Nov 19, 2022 at 21:11
  • $\begingroup$ I don't think this organism is as unrealistic as Daron makes it sound. If you change the function of the light from seeing prey to attracting prey, then you basically have a bioluminescenct anemone. Although this has never been seen (so far), fluorescent anemone have been found and one explanation for why they light up is in order to attract prey (nature.com/articles/srep23493). $\endgroup$
    – E Tam
    Commented Nov 20, 2022 at 1:56
  • $\begingroup$ @ETam Agreed if you change the question the answer is an easy yes. But the question is about finding prey not attracting it. $\endgroup$
    – Daron
    Commented Nov 20, 2022 at 9:01
  • $\begingroup$ @isdi0 See edits for how to modify the friendly Koosh into something more deadly. $\endgroup$
    – Daron
    Commented Nov 20, 2022 at 12:17
  • $\begingroup$ @Daron Ooh I like those ideas! Thanks! I couldn't really get anywhere interesting with the regular planet, so I'll probably use them! I think I like the idea of the Koosh with the siphon! I might actually try and draw some as well, just for fun. Once again thanks so much for the ideas! $\endgroup$
    – isdi0
    Commented Nov 20, 2022 at 12:22

There is a real life fish that projects red light in order to detect prey in the dark Red light is the first wavelength to disappear in water, so most fish, and especially deep sea fish cannot see it. But the dragon fish can in fact see red light and projects it with bioluminescence so it can see prey without being detected.

  • $\begingroup$ <holds pinky finger up to lips> $\endgroup$
    – Mazura
    Commented Nov 21, 2022 at 0:04


This is an anglerfish an actual thing in the oceans of Earth that does what you describe.

enter image description here

  • 3
    $\begingroup$ I thought that an anglerfish uses light to attract prey, not see it, although correct me if I'm wrong. Edit: whoops! Just realized the title does not reflect the exact way they use light, which is to say, they use it to see their prey, not lure it like an anglerfish does. $\endgroup$
    – isdi0
    Commented Nov 19, 2022 at 19:43

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