Cnidaria & Ctenophora

Cnidaria

• Radially symmetrical

• Tentacles contain nematocysts (stinging cells)

Cnidaria• Medusa: free-swimming

• Polyp: sessile

Class Anthozoa

• 6000 species, including sea anemones, corals and sea fans.

• May be solitary or colonial

• Hexacorallia: 6-part symmetry, hard corals

• Octocorallia: 8-part symmetry, soft corals

Class Hydrozoa

• 2700 species, including Portuguese man-of-war, and fire coral

• Both polyp and medusa

• Polyps may be for feeding, defense, and reproduction

Order Siphonophora

• Drifting colonies that inhabit tropical and sub-tropical regions– Physalia (Portuguese

man-of-war)– blue sail-like float– tentacles may reach

several meters below the float.

Class Scyphozoa

• 200 species of jellyfish• Cold to tropical water• 2-40cm (up to 2m)• Most jellies can swim

horizontally and vertically• Aurelia (Moon jelly)• Cassiopea or upside-

down jellyfish (filter feed / zooxanthellae)

Class Cubozoa

Box jelly or sea wasp (Chironex fleckeri)

• Strong toxin, causes immediate, extreme pain

• Death can occur 3-20 min after a sting

Phylum Ctenophora

• 8 comb rows• Have

colloblasts: sticky ends that are used to capture prey

• Catch food with tentacles

Comb jellies

• Bioluminescent• All marine• Most are pea-size

to golf ball-size