A brain of Tritonia diomedea
The brains of sea slugs have become quite important animals in the study of learning and behavior. These animals have a relatively simple nervous system with extremely large neurons which can be individually recorded and stimulated.
The brain looks like a beaded ring surrounding the esophagus near the buccal mass. There are cerebral, pleural, pedal and buccal ganglia, all are paired. In some groups, the cerebral and pleural ganglia appear to be fused just like Tritonia.
The brain has approximately 8000 neurons.