Sea urchins are spiky creatures that move using a water vascular system and feed on algae by scraping stones. Their mouth is on the underside, and they expel waste from the top of their bodies.
Sea cucumbers, brainless but dangerous, feed on plankton and can release a toxic substance harmful to humans.
Jellyfish, unlike most brainless creatures, can move by squirting water to catch prey and evade predators.
Coral and jellyfish, both Cnidarians, sting enemies and lack brains, with coral often mistaken for a plant but actually an animal.
Starfish, brainless relatives of sea urchins, live on the ocean floor and use tiny eyes on their arms to sense light and danger.
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