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Phylum Cnidaria
Cnidos = “Stinging Needle”
www.onacd.ca
BC jellyfish
and sea pen
Coral
• Water temperature must be at least
25 degrees Celsius to survive!!!
• The Great Barrier Reef in Australia can be
seen from outer space!
• The remains of billions of individual
creatures!
• Some coral reefs are 300 metres thick
• Some coral reefs are 25000 years old!
Coral
• Water temperature must be at least
25 degrees Celsius to survive!!!
• The Great Barrier Reef in Australia can be
seen from outer space!
• The remains of billions of individual
creatures!
• Some coral reefs are 300 metres thick
• Some coral reefs are 25000 years old!
OUCH!
Stings from a Portuguese
Man-of-War
4 Classes of Phylum Cnidaria
HYDROZOA – Obelia, Hydra (above),
Portuguese Man O War
ANTHOZOA – anemones (above),
corals, sea fans
SCHYPHOZOA - Jellyfish
CUBOZOA – box jellies (sea wasps)
Characteristics - Phylum Cnidaria
• Acoelomates & therefore do not possess
any true body systems or organs.
• 2 germ layers include ectoderm
(protection), endoderm (inner lining)
• and mesoglea (not a germ layer-it’s the
jelly!!!)
• Radial symmetry
Characteristics - Phylum Cnidaria
• Tentacles
• Capturing food with stinging cells
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(cell:cnidocyte with nematocysts)
• Transportation
Possess a Gastrovascular Cavity (GVC)
Primitive Nervous System (nerve net)
Hermaphroditic : can reproduce sexually
(do not self fertilize) or asexually by
regeneration or budding
Have a motile (medusa) and a sessile
(polyp) stage in their lives
NERVE NET
• The first animals to
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have nerve cells.
The nerves form a
“nerve net”
There is no brain
There is no
cephalization (a
bunching of nerve
cells to form a brain)
2 Body Types
Polyp
Medusa
Gastrovascular Cavity (GVC)
• digestion, circulation, respiration and excretion.
• Cons:
– only one opening….. The mouth is the anus…..
– Body systems - not separated or specialized
Mouth and Anus
Tentacle
Tentacle
Gastrovascular Cavity
Calcified Shell (Coral)
Note: This diagram shows the
GVC in the polyp body type.
GVC
• Digestion: glands release enzymes into
body cavity
• Circulation: via currents generated by
body movements & flagella on
endodermal cells
• Respiration & Excretion: via diffusion
because ectoderm & endoderm are in
direct contact with the water
Cnidocyte with the
Nematocyst
The stinging cells: Nematocysts
• Function: to ward off
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predators and attack
prey
Location: end of
tentacles
Special cells called
cnidocytes
Contain organelle called
nematocyst
Produce a toxin
Action: Releases a
barbed needle that
penetrates the flesh and
injects toxins when
stimulated
A discharged
nematocyst
Life cycle of a typical Jellyfish
#1-10 exhibit the formation of the
polyp life form.
#11 shows the polyp undergoing
asexual reproduction in the form of
budding. The top of the polyp
breaks off and goes on to form the
medusa stage of the jellyfish’s life.
(if this was an anemone the polyp
would settle on the ocean floor and
become a new polyp…. See picture of
brooding anemone on next slide)
#12-14 shows the formation of the
adult medusa
The medusa will then go on to
produce and release egg and sperm
into the water. The eggs will be
cross fertilized by the sperm of
another medusa and eventually
develop into a new polyp
This alternating between two life forms is termed
ALTERNATION OF GENERATIONS
Brooding Anemones - very common – Other polyps form
off existing polyps, break off and then settle on the ocean
floor –Asexual reproduction!
Ecological Importance of Cnidarians
• Filter and clean the water
• Coral die as water
temperature increases or
decreases.
– Death of coral often
precedes death of entire
ecosystems
Symbiotic relationships of
cnidarians
• Coral – a colony of
polyps in symbiosis
with algae
• Clownfish and
anemone
.
Benefit
to clownfish: stinging cells do not harm the
clownfish, but make the fish toxic to other fish…provide
protection and shelter
Benefit to anemone: clownfish clean the anemone
Killer Cnidarians
The Portuguese Man O’ War
• a colony of specialized
polyps and medusas (not a
single jellyfish)
• sting - causes excruciating
pain and sometimes death
• Named for its air bladder
which looks like the sails of
a Portuguese fighting ship
Super cool fact: Loggerhead
turtles are actually immune
to their toxins and feed on
the Portuguese Man O’ War
Portuguese Man O’ War
Physalia physalis
A common sign to
observe near
Australian Beaches
Box Jellyfish
• Possess the most deadly
venom (toxins) in the
animal kingdom which
cause anaphylaxis shock
and death
• In Nov. – April they are
abundant in Australian
waters but it is not known
where they go for the
winter
• Through ultrasonic tagging
it has been found that they
sleep on the ocean floor
between 3pm and dawn to
conserve energy and avoid
predators
• Possess 22 very simple
light sensing eyes as well
as a more developed eye
0.1 mm across
Box Jellyfish Chironex flecker
This jellyfish has had an ultrasonic
tag attached (very carefully!) to it
in order to help learn more about
the migration patterns of these
cnidarians
Jelly FISH OUT OF WATER
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http://ca.youtube.com/watch?v=Fm3EmkWMeHY (part 1 cnidaria)
http://ca.youtube.com/watch?v=QvUZJh9MHt8 (part 2 cnidaria)
http://ca.youtube.com/watch?v=6zJiBc_N1Zk (nematocyst firing)
http://ca.youtube.com/watch?v=Dm98n3908QM (swimming
anemone)
• http://ca.youtube.com/watch?v=_jNwWQtLeY4 (fighting anemone)
• http://ca.youtube.com/watch?v=JoMCTvRkvxo (national geographic
jellyfish)
• http://ca.youtube.com/watch?v=JoMCTvRkvxo(anemone/clownfish
partnership)
• http://www.youtube.com/watch?v=grTN7
BIbzfY comb jellyfish