#Aglantha | Explore Tumblr Posts and Blogs

donuts4evry1 · 10 months

Note

hey excuse me. youre the jellyfish guy from the moon jelly stream yeah. one of my friends mentioned this and i was curious if it had any merit or whatever and i remembered i knew one (1) blog who might know that

Heyyy!! Sorry for being incredibly, incredibly late on this (University was hell but I mainly just used that as an excuse to not research neurobiology haha)

Now, to preface... I know nothing about the human brain. Neurobiology is boring and I want nothing to do with it.

But I do know the deal about jellyfish neurobiology... at least a little bit.

Anyways, jellyfish in general do not have brains or any sort of centralized nervous system (with the exception of Salps and other tunicates, which posses a primitive ganglia. Eugh. Chordates). They are known, for the most part, to have a diffuse "nerve net" (the actual application of this really depends on the species though). It's the simplest form of a nervous system we have here in the animal kingdom.

Calling a diffuse nerve net a "brain" is a little suspect to me personally... mostly because our brain is literally just a flub of fat and muscles and would pretty much be useless if it weren't for the organs it has control over. If I were to put it in simpler terms, brains are like the executive committee for a large company, as opposed to a nerve net, which works closer to like, a few high school friends that run your local McDonald's. Like, that McDonald's can get stuff done, sure, but it's nowhere near as efficient as that large company.

Anyways, with that out of the way, I do want to at least get a little ramble about jellyfish nervous systems :). It won't make much sense but I'll try my best, haha.

I'm sure if anyone here has been following me long enough, they'll know that (cnidarian) Jellyfish are divided up into three distinct groups: Hydrozoa, Scyphozoa, and Cubozoa. The nervous systems of the three vary wildly by complexity, so I'll just start rambling about them by least to most complex.

Hydrozoans:

Hydrozoans are actually a sort of a mixed bag.

Some have nerve nets, while others have nerve rings (like the Aglantha digitale). Nerve nets are basically just scattered nerves (though they tend to gather around important sensory organs) while nerve rings are ring-shaped gatherings of neurons. These run around the bell margin, and process sensory inputs like light, gravity, and touch.

The A. digitale uses these to have two different "swimming" modes (something about one nerve ring being able to generate drastic chemical spikes while the other one can only make gentle chemical spikes to create movement). Honestly you should probably just do the recommended reading below, it'll make more sense.

Scyphozoans:

GOD, now we're getting to the good part. Unlike hydrozoans, Scyphozoans have rhopalia, which contain the light sensing organ, the balancing organ, and pacemaker neurons (basically controlling the gentle pulsation of the bell).

As for the nerve nets, they have two types: Motor and Diffuse nerve nets. Motor nerve nets, to no one's surprise, control movement as a whole (which are ultimately controlled by rhopaliar pacemakers), while diffuse nerve nets mostly serve to advise the motor nerve nets on changing conditions (I have no idea what this means but it seems to play more of a support role when it comes to the animal)

Cubozoa:

We've all heard of them. How sophisticated they are and all the delicious behaviours they're able to irk out of their tiny, brainless bodies.

Like Scyphozoans, they have a diffuse nerve net and rhopalia- though that's about where all the similarities end.

Box jellyfish have true eyes, which are proven to see colour and form images (and box jellyfish seem to have targeted behaviours, like hunting). You know, some box jellyfish, like the Chironex fleckeri (sea wasp) and Morbakka virulenta (Hikurage) are known to "tuck" in their tentacles when not actively hunting? I think that's pretty cool. The Copula sivickis (herpes jellyfish) are also known to um. Have sex. Yeah idk how to make it sound any less awkward.

Anyways, it appears that their nervous system is the most sophisticated, but it largely centers around the Rhopalia (I've seen it being referred to as the "Rhopalial Nervous System" or RNS lol). There's even a ring nerve (not Nerve Ring) that connects the rhopalia, which integrates the swim, visual, and tentacle systems as well.

This is the shortest explanation from the article I'm gleaning this off of, but there are countless research papers that study the cubozoan nervous system.