What are starfish made of?

Starfish, while called "fish," aren't fish at all! They are echinoderms, a group of marine animals that also includes sea urchins and sea cucumbers. Here's a breakdown of what they are made of:

* Calcium Carbonate Skeleton: Starfish have a hard, internal skeleton made of calcium carbonate plates called ossicles. These plates are connected by flexible tissues and muscles, giving the starfish its unique ability to move and change shape.

* Water Vascular System: This is a network of canals and tubes that are filled with seawater. The water vascular system helps the starfish move, grip prey, and even breathe.

* Muscles: The starfish has muscles that control its movement, its arms, and its ability to open its mouth.

* Skin: The starfish's skin is covered in small spines and has a thin layer of tissue that helps it breathe.

* Digestive System: Starfish have a simple digestive system that includes a stomach, intestines, and anus. They have the remarkable ability to push their stomach out of their mouth to digest prey!

* Nervous System: Starfish have a decentralized nervous system, meaning they don't have a brain in the traditional sense. They have a ring of nerves around their central disk and a network of nerves running through their arms.

* Sensory Organs: Starfish have simple eyespots on the tips of their arms that can sense light, as well as sensory organs on their skin that can detect changes in water pressure and temperature.

So, while they might look simple, starfish are incredibly complex creatures with unique adaptations that allow them to thrive in their marine environments.