CNIDARIANS

Cnidarians are water animals that have a simple, usually symmetrical, body with a mouth opening. Stinging cells on tentacles around the mouth catch prey. Cnidarians are either bell-shaped and mobile, like the jellyfish, or tubes anchored to one spot, like coral and sea anemones.

BOX JELLYFISH

Jellyfish drift about in the ocean currents, trailing their tentacles through the water. They sting small animals with the cnidoblasts (stinging cells) on their tentacles and push the prey into their mouth. After digestion, waste passes out of their mouth.

CORAL

Most corals live in colonies, but mushroom corals form a single polyp (anchored tube) that may grow 50 cm (20 in) wide. Their hard skeleton is made of chalk (calcium carbonate). Coral skeletons often build up to form a reef.

SEA ANEMONE

Sea anemones are commonly found in coastal rock pools. They catch fish and other small animals in their stinging tentacles. When the tide goes out, they survive out of water by pulling in their tentacles. This helps them to conserve water.

PHYLUM: CNIDARIA

All cnidarians have stinging cells. Many are able to reproduce asexually (without mating) and sexually. There are 9,000 species.

Class: Anthozoa

(corals, sea fans, sea pens, sea anemones)

Features: anchored polyp (tube-like) form, carnivorous (eat flesh), often in groups

Class: Scyphozoa

(jellyfish)

Features: free-living, medusoid (bell-shaped) form, mouth on underside

Class: Hydrozoa

(hydrozoans)

Features: some free-living, others anchored, most in colonies (large groups), mostly carnivorous

Class: Cubozoa

(box jellyfish)

Features: free-living, box-shaped medusoid form, with long tentacles from corners

Copyright © 2007 Dorling Kindersley

stay connected

Sign up for our free email newsletters and receive the latest advice and information on all things parenting.

Enter your email address to sign up or manage your account.

Facebook icon Twitter icon Follow Us on Pinterest

editor’s picks

highlights

7 Home Remedies to Soothe Cold & Flu Symptoms
The AAP does not recommend giving over-the-counter cough and cold medicines to children under 4, so treating children's cold and flu symptoms naturally can be the best course of action. Read about some home remedies that might help.

Kindergarten Readiness App Wins Gold
Our Kindergarten Readiness app won the Gold Award of Excellence in the educational category at the 2014 Communicator Awards. This valuable checklist comes with games and activities to help your child practice the essential skills she needs for kindergarten. Download the Kindergarten Readiness app today!

11 Awesome Thanksgiving Games & Activities for Families
Looking for fun Thanksgiving Day activities for the whole family? Check out 11 kid-friendly indoor and outdoor activities that will bring your family together in the spirit of the holiday.

Find Today's Newest & Best Children's Books!
Looking for newly released books for your child? Try our new Book Finder tool to search for new books by age, type, and theme, and create reading lists for kids!