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Phylum
Cnidaria
Hydras, Jelly-fish, Sea
Anemones & Coral
Gastrovascular
Cavity
Cnidarians get
their name
from….
Polyp
Medusa
Cnidarians are soft-bodied,
carnivorous animals, that
have stinging tentacles
arranged in circles around
their mouths. They are the
simplest of animals to have
body symmetry &
specialized tissue. They have
radial symmetry in both the
polyp and medusa stages.
A digestive chamber with a
single opening in which
cnidarians, flatworms, &
echinoderms digest food (an
internal space).
“Cnidocytes”-stinging cells
that are located along their
tentacles. They help a
cnidarian survive by
paralyzing their prey.
POLYP- usually the SESSILE
stage in the life cycle of a
cnidarian that has a cylindrical
body with arm-like tentacles.
The mouth points upward. In
jelly-fish the polyp reproduces
asexually.
MEDUSA- MOTILE stage of the
life cycle of a cnidarian that
has a bell-shaped body with a
mouth on the bottom. In the
jelly-fish the medusa
reproduces sexually & most
sexual reproduction is by
EXTERNAL reproduction.
3 Classes of
Cnidarians
Schyphozoa
“Cup Animals”
Anthozoa
Jelly-fish which live
most of their lives
as medusas
Sea anemones &
corals have only the
polyp stage in their
life cycle.
“Flower Animals”
Hydrozoa
Fresh water hydra lacks the
medusa stage & lives as
solitary polyps. Other hydra
live as POLYP COLONIES
with each colony specialized
to perform a different
function. EX: Portuguese
Man Of War