Today’s Wonder of the Day was inspired by Nathan. Nathan Wonders, “How can starfish eat if they dont have a brain?” Thanks for WONDERing with us, Nathan!
Have you ever wished you could follow the Yellow Brick Road to Oz to meet the Wizard? It would surely be an amazing trip full of memorable meetings with interesting characters. Where else would you be likely to bump into a scarecrow singing "If I Only Had a Brain"?
We human beings can certainly sympathize with the Scarecrow. It would be awful to be brainless, wouldn't it? In addition to not being able to think, your body would quickly shut down and die without a brain to control all its functions.
The Scarecrow lived without a brain for quite a while, because he was a fictional character. But most living creatures need a brain to survive. However, there are several interesting creatures that seem to do just fine without a brain.
For example, jellyfish are interesting sea creatures that have managed to survive on Earth for around 650 million years without a brain, heart, or blood. Some of the other animals that survive without brains include the sea star, sea cucumber, sea lily, sea urchin, sea anemone, sea squirt, sea sponge, coral, and Portuguese Man-O-War.
A brain is basically what results when a large group of nerve cells called neurons form one large cluster. Acting together, these neurons control the bodily functions of an animal. So how can any animal survive without a brain?
If you look at the types of creatures that survive without a brain, you'll notice that they're fairly simple creatures compared to a human being or other animals you might be more familiar with. Many of these creatures only need the most rudimentary biological devices to sense things, such as food and danger.
Think about how far technology has come. We have all sorts of "smart" devices around us. These devices don't have brains, but they do contain a wide variety of sensors that can detect various things, including movement, light, and even chemicals. Many of the creatures without brains contain simple mechanisms that allow them to do all the things they need to do to survive.
Jellyfish, for example, have a system of nerve cells, known as a neural net, throughout their bodies. Sea anemones have a similar system. Sea stars, on the other hand, don't have a neural net. Instead, their arms contain sensors that allow them to touch, see, and smell what's around them.
It's commonly thought that jellyfish simply drift aimlessly through the sea. However, a recent study suggests that at least one species of jellyfish can detect ocean current direction using sensors on its body and orient itself to move towards the most optimal ocean area for nutrients.
A few scientists now believe that some simple creatures, such as the sponge, may have had a simple brain at some point millions of years ago. Instead of developing a more complex brain, however, they evolved to get rid of their brain, because they didn't need it. Brains require a lot of energy, and many of these simple creatures couldn't survive if they had to supply a brain with energy.
In the case of sponges, they don't have brains or digestive, nervous, or circulatory systems. They simply filter the water for nutrients with fingerlike structures called cilia. Recently, scientists discovered that sponges can "sneeze" thanks to their cilia. When a foreign particle irritates the cilia, it triggers a reaction that causes the sponge to take in more water and then contract its body to "sneeze" out the foreign particle.