Transcript Cnidaria

Phylum Cnidaria
The Cnidarians
•
•
•
•
•
9000+ species
Jellyfish
Sea anemones
Corals
Hydra
Characteristics
• Entirely aquatic,
mostly marine
• Radial symmetry, no
definite head
• Nematocysts: stinging
cells used for
predation and
protection
Two Body Forms
Polyp
Medusa
Sessile, attached,
cylindrical
Bell or umbrella
shaped, can swim
with jet propulsion
More Characteristics
• Tissue level of
organization
• No coelom
• Gastrovascular cavity
with one opening for
digestion and
circulation
• Reproduction is both
sexual and asexual
• Asexual: budding in
polyps
• Sexual: gametes in all
medusa and some
polyps
Phylum Cnidaria
Phylum Cnidaria
Class Hydrozoa
Class Scyphozoa
Class Cubozoa
Class Anthozoa
Class Hydrozoa
• “water serpent”
• Solitary or colonial
• Hydra: basal disc for
attachment
• Obelia
• Portugese man-of-war
Class Scyphozoa
• “Cup Animal”
• Solitary
• Bell shaped medusa:
bell may 2 meter
diameter, tentacles up
to 70 meters long
• jellyfish
Class Cubozoa
• Cube jellyfish
• Bell is square
• Used to be
considered a subclass of Scyphozoa
Class Anthozoa
• “Flower Animal”
• All polyps
• Flower like
appearance
• Coral
• Sea anemones
• Sea fans
Sea Fan
Sea Anemone
Coral Reefs
• Coral reefs are formations of calcium
carbonate (limestone)
• Deposited over thousands of years
• Living plants and animals are on the top
layer
• More is being constantly deposited