Echinoderms such as starfish (more accurately referred to as sea stars), brittle stars, sea urchins and sea cucumbers do not have a brain or a brain-like organ in their bodies. The coordination of the nervous system is carried out by the nerves that radiate out from around the mouth and down into each arm or tentacle. This arrangement of nerves is called a nerve net and it coordinates the synchronization on the organism’s tube feet as it moves around the ocean floor. Some echinoderms have structures called ganglia which consist of groups of nerve cells clumped together, but this morphology is not considered to be a brain.
The image above shows the necklace or tiled sea star Fromia monilis which does not have a brain but uses a nerve net to coordinate its movements on the ocean floor.
References
- Echinoderm. (n.d.). In Wikipedia. Retrieved December 3, 2017 from https://en.wikipedia.org/wiki/Echinoderm