Sea Urchin

Hello from the seafloor. My name is Sea Urchin, which means 'spiny hedgehog.' It’s a pretty good name for me, don't you think? My body is round and hard, covered by a shell called a 'test,' which protects me like a suit of armor. From this test, dozens of long, movable spines stick out in every direction. They might look a little scary, but I use them for important jobs, like walking slowly along the ocean bottom and protecting myself from animals who might want to eat me. I'm not alone in my family, which is called echinoderms. You might know some of my famous relatives, like the beautiful sea stars and the flat, disc-shaped sand dollars. We all have a special kind of symmetry in our bodies. My favorite places to live are on the rocky seafloor, where I can find plenty of food, or among the busy, colorful branches of a coral reef. It’s a wonderful home, full of amazing sea creatures and plenty of places to hide and explore.

Getting around my neighborhood is quite an adventure. I don't have legs like you do, but I have something even better for life underwater: hundreds of tiny, sticky tube feet. They are on my underside, and I can push water through them to move. Each foot has a little suction cup at the end that helps me grip onto rocks, even when the ocean currents are strong. Also on my underside is my mouth. It’s a very special kind of mouth, with a complicated structure that has five sharp teeth. A very smart human philosopher and scientist named Aristotle wrote about my mouth in his studies way back around 343 BCE. Because he was the first to describe it so well, people have called it 'Aristotle's lantern' ever since. I use this amazing tool to scrape my favorite food, algae, off of rocks. I slowly move along the surface, munching away and cleaning the rocks as I go.

My job in the ocean is very important. You could call me the ocean's gardener. By eating algae, I help keep it from growing too much and covering up the beautiful coral reefs. Corals are living animals, and they need sunlight to survive. If too much algae grows over them, it blocks the light, and the coral can get sick. So, by keeping the algae trimmed, I help the whole reef stay healthy and bright. But everything in nature is about balance. Sometimes, if there aren't enough predators to eat us, my family can grow too big. For example, around 2014, in the kelp forests off the coast of California, many of the sea stars that eat us got sick. With fewer predators around, my sea urchin relatives multiplied quickly. There were so many of us that we ate too much kelp, creating areas called 'urchin barrens.' It was a powerful lesson that shows how every single animal, from the smallest to the biggest, is connected in the great web of ocean life.

My family has been around for a very, very long time. Our ancestors first appeared in the oceans about 450 million years ago, during a time scientists call the Ordovician Period. That means we were living on the seafloor long before the first dinosaurs ever walked the Earth. We have survived through many changes on our planet, adapting to different ocean conditions over millions of years. Even though I am just one small, spiny creature moving slowly along the rocks, I am part of this ancient family with a giant role. By grazing on algae and keeping the ecosystem in balance, I help make it possible for coral reefs and kelp forests to thrive. My story shows that every creature, no matter its size, plays a part in keeping our wonderful ocean world healthy for everyone.