Simple, porous organisms called sea sponges filter nutrients out of water. They have no brain; they rely only on biological functions.
Because their basic movements and nutrition are controlled by a dispersed nerve net, jellyfish may survive with a central brain.
Without a brain, starfish travel and sense their surroundings with the help of radial and nerve rings.
Sea anemones live in watery habitats without a central brain because they use a nerve net to regulate their tentacles and feeding.
Corals are mindless creatures that create colorful reefs in oceans through symbiotic interactions with algae.
This polyp colony uses specialized cells for defense, nutrition, and mobility in ocean waters instead of a brain.
Ancient marine creatures known as sea lilies filter, feed, and navigate their undersea habitat using a basic nervous system.