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Cnidarians are a group of invertebrates that includes jellyfish, corals, sea anemones, and hydras. There are between 8,000 and 9,000 species of cnidarians alive today. The articles listed below provide information about the characteristics, classification and evolution of cnidarians.

Cnidarians are a group of aquatic invertebrates that includes jellyfish, corals, sea anemones and hydras. This profile explores basic facts about cnidarians including how they are classified, what they eat, where they live and the characteristics that make them different from other invertebrate groups.

Cnidarian Characteristics
Cnidarian characteristics include a gastrovascular cavity has only one opening, a mouth, through which the animal takes in food and releases waste. In this article, we'll learn about the characteristics of cnidarians and what makes them different from other types of invertebrates.

Cnidarian Pictures
Pictures of cnidarians, including cnidarian photos such as bubble tip anemones, button polyp coral, jellyfish, hydrozoa and more.

Jellyfish are delicate, soft-bodied animals. They are invertebrates—they have no bones, exoskeleton, or shell to protect or support them. Instead, the water in which they live provides their body with the structural support it requires.

Facts About Jellyfishes
Learn interesting facts about jellyfish and find out about the characteristics make them different from other cnidarian groups, their life cycle and their evolutionary history.

The Life Cycle of a Jellyfish
The most recognized image of a jellyfish is that of the adult jellyfish, also called a medusa, with its bell-shaped body and long tentacles. But there is more to a jellyfish than a medusa.

Anemones and corals (Anthozoa), also referred to as anthozoans, are a group of cnidarians that includes corals, sea anemones, sea fans, and sea pens.

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