Download Phylum Cnidaria

Phylum Cnidaria (Coelenterata)
General Characteristics
Has only one
opening
Has 2 tissue layers
– Epidermis
– Gastrodermis
– Mesoglea (mostly
jellifish)
Body Form- Medusa
Bell-shape
u Free swimming
u Mouth and
tentacles face
down
u
Body Forms-­ Polyp
n
n
n
Tube-­shape
Usually sessile
Mouth and tentacles are face up
Polyp vs. Medusa
General Body Parts
► Mouth
§ Surrounded by ring of tentacles
§ Oral disc surrounds mouth
Tentacles
Contain cnidoblasts
Cnidoblasts contain nematocytes
Stinging structures
“Harpoon –like”
Can discharge to
sting
One of the fastest
known cell
movements
Can contain poison
Can be sticky or
tangle prey
Response – Nerve net
Simple nervous
system with no brain
Limited movement of
prey from tentacles to
mouth
Gastrovascular Cavity
n
A blind-­sac where food is digested
Pedal Disc
Pedal disc
Polyps only
– Used for
attachment.
Skeleton
§ Coral only
§ Made of calcium
carbonate (CaCO3)
§ Forms reefs
§ Very important
ecosystem
Reproduction-­ Sexual
► Sperm and egg (mostly separate sexes)
Reproduction- Asexual
Budding (mostly in
polyp form)
Reproduction- Alternation of
Generation
Class Scyphozoa- Jellyfish
About 200 spp.
Made up of gel-like
substance (mesoglea)
Tend to have
separate sexes
Sex cells visible
through bell
More Scyphozoa
n
Move by pulsating bell
n
n
n
n
n
Not strong swimmers
Vertical migration
Fastest of the plankton
Top: Moon jelly
Bottom: Lion’s mane
Class Hydrozoa
About 3000 spp.
May live alone or in
colonies
– Colonies have many
individuals that has
specialized jobs and
can no longer live
alone
– Top: Portugese Man of
War
– Bottom: Hydra
Class Anthozoa
Largest class
About 6000 sp.
Sea Anemones
No skeleton
Sessile
Single polyps
(larger)
Stinging cells
around mouth
Corals
n
n
n
Colonies
Skeleton (CaCO3)
Zooanthalle (below)
n
Photosynthetic friend
Anthozoa Examples
Top: Northern red
anemone
Bottom: Northern Star
coral
Cnidarian Overview