Major Marine Invertebrate Phyla

SYMMETRY

pentamerous radial symmetry

Phylum Porifera

• Example: sponges• No symmetry = asymmetrical• Simplest animals• No organs or true tissues• Many pores

Phylum Cnidaria

• Examples: jellyfish, corals, anemones, hydra• Radial symmetry• The stingers• Two tissue layers• No organs

Phylum Ctenophora

• Examples: comb jellies• Radial symmetry• Harmless bioluminescent jellies

Phylum Platyhelminthes

• Examples: flatworms• Bilateral symmetry• Simple marine worms

Phylum Annelida

• Examples: polychaete worms, earthworm• Bilateral symmetry• Advanced marine worms• Segmented bodies

Phylum Mollusca

• Examples: clam, snail, octopus, squid• Bilateral symmetry• Soft-bodied invertebrates with large “foot”

Phylum Arthropoda

• Examples: crab, shrimp, lobster, insects, arachnids

• Bilateral symmetry• Exoskeleton• Segmented body with jointed appendages

Phylum Echinodermata• Examples: sea stars, sea urchins, sea

cucumbers• Pentamerous radial symmetry• The “stars”• Spiny skin