Phylum CnidariaThe Stingers

Classes

• Hydrozoa• Anthozoa• Scyphozoa

Shared Traits

• Radial symmetry• Carnivorous• Reproduce sexually and asexually• Polyp and medusa form– Polyp: sac-like stage with waving tentacles, nonmotile

and benthic– Medusa: bell-like stage, hanging tentacles, motile and

planktonic

Body Layers & Parts

• Ectoderm/Epidermis: outside layer containing stinging cells (nematocysts)

• Tentacles: used for food capture, lined with nematocysts

• Endoderm/Gastrodermis: lines the gut, cells here aid in digestion (absorption of stung prey)

• Mesoglea: jelly-like substance found between the above two layers

• Mouth and anus are the same opeining

Polyp Phase and Medusa Phase

Nematocysts

• Coiled firing cells that shoot toxin into prey• Most not deadly to humans as they aren’t

usually able to penetrate our skin• Some fatal

Class Anthozoa

• Largest group of Cnidarians

• Stay polyps their whole lives

• Solitary or colonial• Example: Sea

Anemones, Corals

Class Anthozoa

Class Anthozoa

Class Hydrozoa• Can have just a polyp stage, just a medusa stage, or both• Can join to form complex colonies, like Portuguese Man O’

War (see next slide)

Class Hydrozoa

Class Scyphozoa

• Medusa is the dominant life stage

• Move with rhythmic contractions

Class Scyphozoa