Even with no brains, jellyfish can learn from their mistakes

Enlarge / No brain, but still some smarts. (credit: Bielecki, et. al.)

They don't have a brain or spinal cord. They float around in a way that often appears aimless. Though jellyfish lack a central nervous system, these gelatinous creatures again show that they might think more than we think they do.

Jellyfish, or medusae, belong to the group Cnidaria, members of which are already known to be capable of associative learning. This is how they can maintain awareness of their surroundings (and possible predators). Now, an international team of scientists has found that the cnidarians are capable of a slightly more advanced type of associative learning known as operant conditioning, which entails remembering the positive or negative effects of a previous action. Despite lacking a brain, Caribbean box jellies (Tripedalia cystophora) can still learn from their mistakes to avoid a potentially disastrous outcome.

Damage control

T. cystophora are about the size of a human fingernail, and while they are much less complex than vertebrates such as humans, they still have a rather sophisticated visual system for a jellyfish. The jellies have 24 eyes around their bodies—and they need them. They live in mangrove swamps where crashing into long roots is almost inevitable in murky water, and a jelly might do serious damage to its delicate body in these encounters. Its vision assists it in navigating among the roots and can be especially useful for hunting around these gnarly tangles.