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

highlights

Happy Surfing! 5 Safe Search Engines for Kids
These safe search engines for kids offer pre-screened sites and age-appropriate filters and content, so your child can have the freedom to browse the Internet while you have peace of mind that he's safe online.

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!

Best School Supplies of 2015
It's time to stock up on the latest and greatest school supplies! Make sure your child has all the trendy accessories and must-have classroom staples he needs.

Ready for Kindergarten?
Try our award-winning Kindergarten Readiness app! This easy-to-use checklist comes with games and activities to help your child build essential skills for kindergarten. Download the Kindergarten Readiness app today!

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 Facebook icon Follow Us on Pinterest

editor’s picks