All About Cnidarians

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Great video to learn all about the defining characteristics of cnidarians.
Head to ngscience.com for a full range of supplementary interactive resources relating to the classification of organisms.

Cnidarians are animals that live in aquatic environments. Most can be found in the ocean, but some also live in fresh water. Jellyfish are cnidarians with soft jelly-like bodies. They spend the early stages of their life cycle attached to the sea floor and are free-swimming as adults. Jellyfish have tentacles that are used to catch prey.

Corals are cnidarians that spend their lives attached to the ocean floor or other underwater surfaces. Some corals get the energy they need from algae living within their tissue. Others have a series of tentacles that are used to catch small organisms floating by their anchored bodies.

Most cnidarians reproduce sexually, whereby sex cells are released and are fertilized in water. Some corals are also able to reproduce asexually by budding. Unlike sponges, cnidarians have radial symmetry. This means their bodies are arranged around a central point with more than one line of symmetry.

A unique characteristic of cnidarians are stinging cells called cnidocytes. Cnidocytes contain a toxin and are used to stun and capture prey. They are also used for defense against predators. Some jellyfish produce toxins that are harmful to people.