Scyphozoa

Scyphozoa: The True Jellyfish

Scyphozoa are a special group of animals called true jellyfish. They live only in the ocean and belong to the phylum Cnidaria. These creatures have been swimming in the sea for millions of years, since the Cambrian period.

The name Scyphozoa comes from an ancient Greek word, skyphos, meaning a kind of drinking cup. People chose this name because these jellyfish often look like little cups floating in the water.

Most true jellyfish have two important stages in their life. One stage is called the medusa, which is the floating part you might see in warm summer months. The other stage is a tiny polyp that lives on the ocean floor. Many of the big, colorful jellyfish you see near coasts are Scyphozoa. They can be as small as a few centimeters or as big as two meters across!

These jellyfish live in oceans all around the world, from the surface to deep waters. They never live in freshwater or on land. True jellyfish eat small animals like tiny crabs and fish using special stinging cells on their tentacles. Some also eat plankton by straining it from the water.

Inside, jellyfish have a soft, gel-like material called mesoglea that helps them keep their shape. They swim by using muscles around their edges to push through the water. Even though they don’t have heads, skeletons, or special organs, they can move and sense their surroundings. Their bodies are mostly water, which makes them float easily and look almost transparent sometimes.