Nine Mindless Sea Animals
Jellyfish don't have brains, but they have neurons that carry messages. Jellyfish are heartless and lungless. Thin skin absorbs oxygen. Jellyfish don't have blood or a heart.
Brainless sea urchins. Mouth nerve ring. Simple nerves in sea urchins. Without a brain, the lantern's neural centre is a nerve ring.
The sea cucumber's neural tissue-lined oral canal sends impulses to its mouth and tentacles. They scavenge rotting debris and algae on the seafloor.
Even without blood or a brain, starfish can digest food outside. Even that doesn't make them intriguing. Starfish can regenerate their arms over time.
Primitive sea sponges lack a brain and internal organs. These stationary animals subsist by filtering water for organic particles and organisms.
Corals lack brains but have a nerve net. This system spans the animal's mouth to tentacles. There are 6,000 types of corals that vary in colour, size, and shape.
Clams don't have brains, but their nervous system nevertheless allows them to feel and react. Clams, a type of bivalve mollusk, inhabit both salty and fresh water.
Oysters lack a brain but have a nerve system, organs, and a heart. Oysters are filter feeders and can filter 1.3 gallons per hour.
Anemones are connected to corals and jellies. Sea anemones have no brain, only a nerve system. Their nervous system reacts to stimuli.