Phylum Cnidaria Cnidos =

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Phylum CnidariaCnidos Stinging Needle
www.onacd.ca
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4 Classes of Phylum Cnidaria
HYDROZOA Obelia, Hydra (above), Portuguese Man
O War
SCHYPHOZOA - Jellyfish
ANTHOZOA anemones (above), corals, sea fans
CUBOZOA box jellies (sea wasps)
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Identifying Characteristics of the members of
Phylum Cnidaria

• Non-coelomates therefore do not possess any
  true body systems or organs. 3 germ layers
  include ectoderm (protection), endoderm (inner
  lining) and mesoglea
• Exhibit radial symmetry
• Possess tentacles used in transportation and for
  capturing food and stinging cells called
  nematocysts.
• Possess a Gastrovascular Cavity (GVC)
• Primitive Nervous System
• 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
• Found in marine habitats

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Gastrovascular Cavity (GVC)

• The inner cavity responsible for digestion,
  circulation, respiration and excretion.
• Disadvantages of having a GVC include
• There is only one opening.. The mouth is the
  anus..
• Body systems of digestion, circulation,
  respiration and excretion are not separated or
  specialized

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2 Body Types Present in Phylum Cnidaria

• Polyp
• Sessile (no movement as they are anchored to the
  ground)
• Tentacles face up
• asexual
• Ex. Hydra, sea anemones, coral
• Medusa
• Motile
• Tentacles face down
• sexual
• Ex. Jellyfish, sea wasps

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The stinging cells Nematocysts

• Nematocysts are most commonly located at the end
  of tentacles
• Are composed of special cells called cnidocytes
  that have special organelles (cnidocysts) that
  produce a toxin
• When a trigger is stimulated it releases a barbed
  needle that penetrates the flesh and injects
  toxins.
• Nematocysts are used to ward off predators or
  attack prey

A discharged nematocyst
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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 jellyfishs 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
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Brooding Anemones From a single anemone other
polyps are forming which will eventually break
off and settle on the ocean floor to form new
anemones. This is why many of the same type of
anemone are often observed in the same area as
the new polyps are not capable of traveling far
distances.
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Ecological Importance of Cnidarians

• Filter and clean the water
• Form symbiotic relationships with other ocean
  life
• Examples.
• Clownfish and anemone (remember Finding Nemo?)
• Coral and many types of algae
• Coral will die as the water temperature
  increases. Death of coral often precedes death
  of entire ecosystems

The clownfish are immune to the stinging cells of
the clownfish anemone. Therefore the anemone
provides protection and shelter for the clownfish
and in turn the clownfish clean the anemone.
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Super Cool Killer Cnidarians

• The Portuguese Man O War
• Looks like a jellyfish but is actually a colony
  of specialized polyps and medusas
• The sting from their tentacles 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
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A common sign to observe near Australian Beaches
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• 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
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Jelly FISH OUT OF WATER