Brainless box jellies learn from experience

Jellyfish have demonstrated that you don’t need a centralised nervous system to learn by association. Tiny Caribbean box jellyfish (Tripedalia cystophora) can be trained to associate the feeling of bumping into an obstacle with a visual cue, and to use the information to avoid future collisions. Learning happens in the jellies’ rhopalia — structures containing rudimentary eyes plus nerve centres that control swimming pulses.