Coelenterata facts for kids

Coelenterata was an old name for a group of animals. Scientists don't use this name anymore. It used to include two main groups: the Cnidaria (like jellyfish and corals) and the Ctenophora (also known as comb jellies).

Scientists changed this name because new discoveries helped them understand how these animals are related. They used special tests that look at the tiny parts inside animals, like their proteins and DNA. This is called molecular evolution. By studying these tiny parts, they found that Cnidaria and Ctenophora are actually different enough to be in their own separate major groups, called phyla.

What are Cnidaria?

Cnidaria are a group of animals that live mostly in the ocean. They include well-known creatures like jellyfish, corals, sea anemones, and hydra.

Key Features of Cnidaria

• Stinging Cells: Cnidaria are famous for their special stinging cells called "cnidocytes." These cells have tiny harpoons that can shoot out to catch food or defend themselves.
• Body Shape: Most cnidarians have a simple body plan. They are usually shaped like a sac or a bell. They have one opening that acts as both a mouth and an anus.
• Radial Symmetry: This means their body parts are arranged around a central point, like the spokes of a bicycle wheel. You could cut them in many ways through the center and get mirror images.
• Habitat: Most live in saltwater, but some, like hydra, can be found in freshwater.

What are Ctenophora?

Ctenophora are another group of ocean animals, often called "comb jellies." They look a bit like jellyfish but are different in important ways.

Key Features of Ctenophora

• Comb Rows: The most unique thing about comb jellies is their "combs." These are eight rows of tiny hairs (called cilia) that they use to swim through the water. When light hits these combs, they often create a beautiful rainbow effect.
• No Stinging Cells: Unlike cnidarians, comb jellies do not have stinging cells. Instead, many use sticky cells called "colloblasts" to catch their food.
• Bioluminescence: Many comb jellies can produce their own light, a process called bioluminescence. This makes them glow in the dark ocean.
• Predators: They are usually predators, eating small plankton and other tiny creatures in the water.

Why the Change?

For a long time, scientists grouped Cnidaria and Ctenophora together because they both have simple body plans and live in water. However, as technology improved, scientists could look at their DNA and proteins more closely.

This deeper look showed that while they might look similar on the outside, their internal structures and genetic makeup are quite different. This is why the old name "Coelenterata" was split into two separate and distinct phyla: Cnidaria and Ctenophora. This helps scientists better understand the true family tree of animals on Earth.