There is one little creature that lives in tidal pools and over shallow ocean areas, that has a rather strange and fascinating characteristic: it eats its own brain. The sea squirt is a little undersea animal which is part of the tunicate family.
Whenever poked or threatened, this small animal will squirt water out in an attempt to scare off their predator. Tunicates are little organisms that feed off plankton, normally they hook themselves onto a rock or plant life and then do not move again. Essentially they just strain water through their body all day and feed off any microorganisms that happen to pass through.
Sea squirts would probably best be described as looking like a sponge, funnily enough, they are actually also part of the same group of animals such as birds or reptiles. This is because when they are in their larvae state they do actually contain many of the same anatomical features. Then once formed, they evolve into the spongy looking shapes and actually tend to form whole colonies of sea squirts together.
But the real uncanny feature of the sea squirt is, of course, their ability to eat their own brain, which is just a natural part of their lifespan. You see sea squirts are hermaphrodites meaning they have both female and male reproductive organs, which allows them to simple spawn eggs when it is time to reproduce. When the larvae are born, they can only swim for a small amount of time because they need to feed, so they go head first into the spot that they will spend the rest of their lives in. At this point, the transformation into sponge starts and the larvae need to feed immediately, so it absorbs its own brain as food.
So yes they do eat their own brain, but only because they no longer need it: they are never going to move again.