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Jellyfish, Coral, Sea Anemone, and
• Stinging cell animals
• Also Known As: Coelenterates: “Hollow
• Radial Symmetry: similar body parts
surrounding a central axis
Body Plan
• No segments: oral and aboral sides
• Hydrostatic Skeleton: fill body cavity with water
to remain upright.
• Shrink down as defense
• Organized at tissue level. (No true organs)
• Epidermis: outer cells (ectoderm)
• Gastrodermis: lines stomach (endoderm)
• Mesoglea: middle layer of gelatinous material; can
be thick or thin.
• Food is digested in the sac-like digestive
cavity (only one opening)
• Extracellular and intracellular digestion
• Extracellular: outside of cells
• Intracellular: inside of cells
• Waste is expelled out of the mouth
Unique Features
• Cnidoblasts: stinging cells
• Inside each cell is a nematocyst, coiled thread with
barb at the end.
• The nematocyst can be discharged by either
physical or chemical stimulus.
• Physical- cnidocil (modified flagella) acts as a
• Contain a poisonous neurotoxin, varies by species
Nervous System
• Nerve cells interconnect to form a nerve net
Life Cycle
• Jellyfish have separate sexes
• Both sexual and asexual reproduction
• Sexual: external or internal (depending on
species), sperm and egg form a zygote
which grows into a swimming larva called
the planula.
• In some cases the planula attaches to a hard
substrate and develops into a polyp.
Life Cycle cont.
• The polyp resembles an upside-down
jellyfish medusa.
• Small umbrella like medusas break off from
the polyp by budding (asexual)
Classification of Cnidarians
• Class Hydrozoa- Hydra, Physalia, and
• Class Scyphozoa- True Jellyfish
• Class Cubozoa- box jellyfish
• Class Anthozoa- Corals and Sea Anemones
Class Hydrozoa
• Usually colonial, except Hydra
• Composition of colonies- 3 types
1. Gastrozoid- responsible for feeding
2. Gonozoids- responsible for sexual
3. Dactyliozoids- responsible for defense;
have numerous nematocysts.
Class Scyphozoa
• All marine; medusa is dominant life cycle
• Mesoglea is a large part of the body (mostly
dead matter)
• Gastroderm have nematocysts; food may be
eaten alive
• More toxic than hydrozoans
• Well developed sensory organs and glands
- eyespot and chemoreceptors
Class Cubozoa
• Cube-like jellyfish
• Have four flattened, blade-like structures
called pedalia
• Complex eyes with lenses and retinas (no
brain though)
• Only 16 species: Irukandji and Chironexdeadly box jellyfish. Can kill a human in
Irukandji: Carukia barnes
• One of, if not the
deadliest box
• 2.5 cm (1 inch) in
Box Jellyfish Sting
Chironex- Sea Wasp
Class Anthozoa
• No medusa stage in life cycle
• Polyps produce eggs and sperm that
develop into planula larva
• Solitary: sea anemone
• Colonial: coral
Tube Sea Anemone
Sea Anemone
Soft Coral
Corals and Coral Reefs
• Corals are colonial cnidarians
• Dominant form is the polyp
• Coral reef is a massive structure composed
of calcium carbonate built by coral polyps
and the organisms that live with in them
• The polyps take up calcium in the sea water
and zooxanthellae, which live inside the
polyp, take up CO2, which make limestone
Hard Coral
Coral Reefs
• Found only in tropical areas
• Warm and clear water
• Shallow water- zooxanthellae require
sunlight to photosynthesize
• Zooxanthellae are the primary producers of
the coral reef
Coral Reef Formation
• Fringing Reef: occurs when a seamount pierces
the sea surface to form an island and provides a
base on which the coral can grow
• Barrier Reef: occurs if a seamount subsides
slowly enough and the coral continues to grow
upward at a rate that is not exceeded by the rising
water. A lagoon is formed.
• Atoll- occurs if the seamount disappears below the
surface and the coral reef is left as a ring.
Atafu Atoll: South Pacific
Symbiosis and Cnidarians
• Symbiosis: literally means to live together
1. Mutualism: both organisms benefit from
living together
2. Commensalism: one organism benefits,
the other is unaffected
3. Parasitism: one organism benefits, one is
Clownfish and Anemones
Sea Anemones and Clownfish
• Usually, fish the size of clownfish are stung and
eaten by an anemone
• Clownfish become immune to the anemones
nematocysts because of a mucus coating
• The mucus inhibits the anemone’s sting
• The anemone provides protection and scraps of
food for the clownfish
• The clownfish lures prey into the anemone and
cleans the anemone
• What kind of relationship is this?______________
Coral and Zooxanthellae
Corals and Zooxanthellae
• Zooxanthellae are dinoflagellates that are taken up
by the coral polyps.
• Zooxanthellae contain chloroplasts
• Coral use the glucose made by the zooxanthellae
as an energy supplement
• The zooxanthellae benefit because they are
protected and receive nutrients from the coral
• What type of relationship is this? _____________
Phylum Ctenophora
Comb Jellies
Take notes on your own sheet of
paper, only write down what is
Group of 100 species
Oval shaped with radial symmetry
Resemble cnidarians but are NOT!
Swim with 8 rows of ciliary combs (long
cilia fused at the base)
• Cilia refract light which
cause a rainbow effect.
• Body length varies from a few centimeters
to 2 m long.
• Exclusively marine
• Can be found in cold or warm water
• Carnivores
• Consume fish larvae and plankton
• Can expand stomach to eat organisms twice
their size.
• Capture prey with two long tentacles armed
with sticky cells called colloblasts
• A few species have nematocysts
• Sexual reproduction
• Hermaphrodites
• No polyp form; only medusa
Life Cycle
Deep Sea Comb Jelly
On a sheet of paper do the following
1) Title the paper: Porifera, Cnidaria, and
Ctenophora Lab
2) Number your paper from 1-22
3) Leave space on #11, #14 and #16 for
drawings (about 5 lines)
4) Use your Porifera Notes and Cnidaria
Notes to answer the questions (answers
only, don’t worry about writing the