Download File - Zoology with Mrs. Stebbins

Phylum Cnidaria
Jellyfish, Sea Anemones and Coral
Background
 Examples Jellyfish, Sea anemones, etc.
 Soft bodied animals with stinging tentacles
arranged in a circle around the mouth.
 All have radial symmetry
 Specialized cells & tissues
Background
 2 distinct stages of life


polyp-sessile (non-moving) flowerlike
medusa- motile (moving) bell shape
 Have gastrovascular cavity-hollow central
space inside, digestion happens here
Form and Function
 Predators- use
nematocysts (stinging
cells) to stun prey they
eat.


Nematocyst resembles
loaded dart.
“dart” springs into prey
they releases the
poison which paralyzes
victim.
Form and Function
 Predators


prey is then pushed through mouth into
gastrovascular cavity where it’s broken up
slowly.
Anything not digested goes back out through
the mouth.
 Most species of Cnidarians are only a few
cell layers thick. No complicated body
systems.
Form and Function
 Nerve Net



simple system concentrated around the mouth.
Does spread through the body.
Information is transmitted by specialized cells.
• Chemical and touch receptors- medusa and polyp
forms. Also, helps tell which way is up.
Form and Function
 NO muscle cells- but some epidermal cells
act like muscles when stimulated.


Can extend, shrink and move tentacles.
These cause Jellyfish medusa to “open/close”
 Reproduction- Asexual and Sexual


Asexual- polyps can bud, resembles tree buds
Sexual-open water fertilization, ciliated larva
swims around then settles attaching itself to
hard surface.
Specific Cnidarians
 Class Hydrozoa
 Class Scyphozoa
 Class Anthozoa
Class Hydrozoa
 Hydra, Portuguese
Man of War
 Long polyp, short
medusa
 Colonial

Specialized polyps
have specific jobs.
Class Hydrozoa
 Freshwater Hydra



Solitary polyps, no
medusa stage.
Somersault to move.
Separate sexes
(usually) some are
hermaphroditic.
Class Hydrozoa
 Polyp colony



one polyp forms a
balloon to keep colony
floating.
Others form long
stinging tentacles.
Other polyps digest,
others make eggs &
sperm.
Class Scyphozoa
 Same life cycle
 long medusa, short
polyp (larva form
only)
 size varies
 Nematocysts relatively
harmless but a few
species can cause

Australian jellyfish
causes death in 3-20
minutes.
Class Scyphozoa
Jellyfish washed onshore
Underneath View
Class Anthozoa
 Sea Anemones, Coral
 Only polyp form, no
medusa
 Sexual Reproduction



open water external
fertilization
ciliated larva
ciliated larva swims to
bottom and becomes
polyp
Class Anthozoa
 Sea Anemones




solitary polyps
range from low tide
areas to the very deep.
Some are
photosynthetic
All have and use
nematocysts
Class Anthozoa
 Found in shallow
water.
 Have a skeleton make
of calcium carbonate.
 Mostly colonial
 Most produced by
budding.
 Grow very slow
 Form coral reefs
Niche in World
 Symbiotic Relationship- Ex. Clownfish and
sea anemones
 Coral reefs- provide homes for fish, pearls,
protect land from wave actions.
 Medical research- Anti-cancer drugs from
coral reef defense toxins, help deepen
understanding of nerve cell function.