phylum cnidaria
TRANSCRIPT
4 Classes we’ll cover:
• Hydrozoa• Anthozoa• Scyphozoa• Cubozoa
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
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 – Sea Pens
Class Anthozoa – generalities
• Largest group of Cnidarians
• Stay polyps their whole lives
• Solitary or colonial• Example: Sea
Anemones, Corals, Sea Pens
Corals – Special Characteristics
• Hard corals – calcium forming• Contain zooxanthellae, a
symbiotic dinoflagellate• Soft corals – less calcium,
more flexible protein structure• Great Barrier Reef off
Australia-world’s largest living structure.
• Most corals need shallow, salty water
Anatomy of a Coral Polyp
Corals eat (capture food using tentacles) as well as make their own food (via
zooxanthellae)
Coral Reef Issues
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
