Everyone needs a brain to live, right? Not necessarily! Some of our fellow animals have no such thing, yet manage to survive just fine. Instead of having a brain, some animals have clusters of nerve cells called ganglia to help direct traffic in their bodies. But amazingly, most of the animals on this list don’t even have ganglia to help them out. When it comes to doing what they need to do to survive, these animals don’t give it a second thought. In fact, they don’t even give it a first thought.
Even though they don’t have a brain or even ganglia, sea stars do have some sense of touch, sight and smell. Each of the sea star’s arms can sense the world around it. When one of the arms smells something good to eat, it cuts off power to the other arms and starts pulling the entire creature towards the food source.
Sea cucumbers don’t have grey matter, but they have ingenious defense mechanisms. When under attack, sea cucumbers can startle (and gross out) their attacker by suddenly disgorging their guts and internal organs. Or they can opt to eject long sticky tubes from their anus to ensnare and possibly disable the predator – permanently.