What's on the mind of a jellyfish? A review of behavioural observations on Aurelia sp. jellyfish.

Aurelia sp. (scyphozoa; Moon Jellies) are one of the most common and widely distributed species of jellyfish. Their behaviours include swimming up in response to somatosensory stimulation, swimming down in response to low salinity, diving in response to turbulence, avoiding rock walls, forming aggregations, and horizontal directional swimming. These are not simple reflexes. They are species typical behaviours involving sequences of movements that are adjusted in response to the requirements of the situation and that require sensory feedback during their execution. They require the existence of specialized sensory receptors. The central nervous system of Aurelia sp. coordinates motor responses with sensory feedback, maintains a response long after the eliciting stimulus has disappeared, changes behaviour in response to sensory input from specialized receptors or from patterns of sensory input, organizes somatosensory input in a way that allows stimulus input from many parts of the body to elicit a similar response, and coordinates responding when stimuli are tending to elicit more than one response. While entirely different from that of most animals, the nervous system of Aurelia sp. includes a brain that creates numerous adaptive behaviours that are critical to the survival of these phylogenetically ancient species.