Marine Invertebrates Amazing Diversity of Life

Phylum Porifera

Porifera (pronounce: pore-if-er-a) are commonly called the sponges.  These are structurally simple animals with no distinct organs.  Porifera means “pore-bearing,” and the pores are openings through which water and the microorganisms they eat enter, and wastes leave.

Phylum Cnidaria

Organisms in Phylum Cnidaria (pronounce: nigh-dare-e-ah) include the corals, hydras, jellyfish, and anemones.  Some cnidarians are single organisms, others are colonies of many small organisms.  Cnidarians have cnidocytes (pronounce: nigh-doh-cites), stinging cells that can stun prey or a potential predator.  These cnidoctes are typically at the end of tentacles that surround the mouth. 

Phylum Echinodermata

Animals in Phylum Echinodermata (pronounce: ee-kine-o-derm-ah-tah) generally have a spiny surface, echinoderm means “spiny skin.”  All echinoderms have small and flexible tube-like feet for movement.  Echinoderms include sea stars, brittle stars, sea urchins, sand dollars, and sea biscuits.

Phylum Mollusca

Animals in Phylum Mollusca (pronounce: mul-usk-ah) are animals with soft bodies (mollusk means soft), a muscular foot for locomotion, a mass of internal organs, and a heavy tissue called the mantle which can in many species produce a hard shell.  Mollusks include snails, slugs, nudibranchs, clams, limpets, squid, and octopuses.

Phylum Annelidia

Organisms in Phylum Annelidia (pronounce: an-el-eh-dah) are segmented worms that lay eggs.  The best known terrestrial annelid is the earthworm.  Marine annelids include bristle worms, tube worms, spaghetti worms, and feather dusters.

Phylum Arthropoda

Organisms in Phylum Arthropoda (pronounce: arth-rah-pod-ah) are animals that have body segments and jointed appendages (legs and antennae).  The word “arthropod” means “jointed feet.”   Marine arthropods include shrimp, crabs, hermit crabs, barnacles, amphipods, and krill.