Transcript What do these animals have in common?

What do these animals have in
common?
Phylum
Cnidaria
“the jellies”
What is a cnidarian?
•invertebrates
•more than 9000 species
•jellyfishes, corals, sea anemones, and hydras.
•worldwide
•all but a few are
marine
• two distinct body forms during their life
cycles
Medusa
Polyp
• polyp = sessile form
•mouth surrounded by tentacles.
- sea anemones, corals, and hydras.
• medusa = free-swimming form
- jellyfish
Body Form
The Medusa
-an umbrella-shaped,
- floating body = a bell,
with mouth on underside.
Tentacles
Body Form
mouth
The Polyp
Attached to substrate,
mouth on top
surrounded by
tentacles
Body form
One body form may be more often seen than the
other.
In jellyfishes, the
medusa form is usually
observed.
In hydras, polyp
form is most
common form of
hydras.
http://www.microscope-microscope.org/gallery/Mark-Simmons/pages/hydra2.htm
Body form
Most cnidarians undergo a change in
body form during their life cycles.
Medusa
Polyp
At some point, most Cnidarians exist as
both a polyp and a medusa.
Body structure
Mouth
Tentacle
• radially symmetrical
• one body opening
• two cell layers
How is this similar to
sponges?
Cavity
Inner cell
layer
Bud
Jellylike
layer
Outer cell
layer
Disc
Body structure
• cell layers are
organized into tissues
with specific functions
- true tissues
- inner layer mainly
assists in digestion
-surrounds the
GASTROVASCULAR
CAVITY
Mouth
Tentacle
Cavity
Inner cell
layer
Bud
Jellylike
layer
Outer cell
layer
Disc
Body structure
• two cells layers allows easy diffusion of:
- Oxygen - dissolved in
water, it can diffuse
directly into body cells.
- Carbon dioxide /other
wastes - moves out of the
body cells directly into the
surrounding water.
Reproduction in cnidarians
• sexual and asexual reproduction
Sexual reproduction
•occurs in only in the Medusa phase if it has
both forms in life cycle
IF there is NO medusa stage, then the
polyp can reproduce sexually.
Sexual Reproduction in Cnidarians
Both the
medusae and
Eggs
polyps are
Fertilization diploid
Female
Male
(2n)
Asexual
Reproduction
animals.
Blastula
Bud
Larva
Diploid =
2 full sets of
Polyp
chromosomes
Per body cell
Nematocyst
before discharge
Nematocyst
after discharge
Digestion in cnidarians
• Predators
- capture or poison prey using nematocysts
- a capsule that contains a coiled, threadlike tube.
-tube may be sticky or barbed, and
may contain toxins
- located in stinging cells that are on
tentacles
Digestion in cnidarians
Once captured by nematocysts, prey is brought
to the mouth by contraction of the tentacles.
Mouth
Polyp
Gastrovascular
cavity
Mouth
Medusa
• Food enters
gastrovascular
cavity
• digestive cells release enzymes to break down prey
•undigested materials are ejected back out through
the mouth.
Diversity of Cnidarians
There are four classes of cnidarians:
• Hydrozoa
•Anthozoa
•Scyphozoa
•Cubozoa
Class Hydrozoa
•2 groups
- hydroids (hydra)
- siphonophores (Portuguese man-of-war)
• marine animals
•Most hydrazoans go through both stages
• Hydra - polyp stage only
•reproduce by budding
•found attached to piers, shells, and other
surfaces.
daphnia
Sea monkey
development
budding
#1
Class Hydrozoa
The siphonophores - floating colonies
-drift about on ocean’s surface.
The Portuguese manof-war, Physalia, is an
example of a
siphonophore
hydrozoan colony
Different functions for
different individuals
Class Anthozoa
• exhibit only the polyp form.
• Corals
• Sea anemones
• Sea fans
Sea apple
feeding
Corals
• live in colonies of polyps in warm ocean waters
around the world.
• secrete protective, cuplike calcium
carbonate shelters around their soft bodies.
•Colonies of many coral species build
the coral reefs
•provide food and shelter for many other
marine species.
Corals
Corals that form reefs are
= hard corals.
• soft corals= do not build
calcium carbonate
structures – not reef
builders.
Corals
Living portion of a coral reef is a thin,
fragile layer
•grows on top of the shelters left behind by
previous generations.
Often found in
•shallow,
•nutrient-poor waters,
•thrive because of symbiotic relationship with
microscopic, photosynthetic protists called
zooxanthellae.
Bleaching Worldwide
•Zooxanthellae
•produce oxygen and food that corals use,
•Uses carbon dioxide and waste materials produced
by the corals
•cause bright colors found in coral reefs.
•free-swimming, sometimes leave the corals
•Caused by warming ocean temperatures and
•Increasing acidity due to increased CO2 in
atmosphere
•Corals die without them = “bleaching”
•70% bleached in 20-30 yrs; 35 million acres so far
• Coral reefs provide habitat for 25% of
marine fish
• About 1 billion people rely on fish as their
primary food source
• Tourism – over a billion dollars is spent
every year in the Caribbean, Australia (3.9
billion/year), and the Pacific Islands
• 1.2 Billion in Florida each year
• Most diverse ecosystem – “Ocean
Rainforest”
• 4000 species of fish, 800 species of coral
• Corals are used for pharmaceuticals
• Chemical extracts from corals have helped
create drugs to treat AIDS, Cancer, Arthritis,
Inflammatory disorders, and pain killers
• Beneficial for patients with heart, kidney,
and liver transplants.
Class Scyphozoa = jellyfish
•Fragile
•sometimes luminescent bodies
• Some are transparent
•May be pink, blue, or
orange.
Medusa form is
the dominant stage in
this class.
Class Scyphozoa
• muscle-like cells in outer cell layer can
contract
• When these cells contract , the bell contracts
• propels the animal through the water.
Class Cubozoa
• Box jellyfish
• Originally included in Class Scyphozoa.
• Differences:
–
–
–
–
–
Their bells are square-shaped, instead of round
They have primitive brians
They have eyes
They swim, not float
They sleep
Class Cubozoa
• The Irukandji in Australia is one of the most
dangerous animals
• It is very small, only 2.5 cm from bell to
tentacles
Giant Jellyfish
• Japan has been invaded by Nomura’s
jellyfish – the giant jellyfish.
Research:
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What are Nomura’s Jellyfish?
Where are they found? Just Japan?
What causes them to get so big?
Are they dangerous?
Are they new? Or are they only now getting
noticed?
Giant Jellyfish
• 6.5 ft wide
and 450 lbs
• More
common in
China and
Korea
• Only recently
in Japan
Giant Jellyfish
• Not much is known, Japan studying
mating/migration habits
• Choking fishing nets
• Possible warmer seas (global warming)
causes increase in population
•
http://video.google.com/videoplay?docid=2208948115892996006&q=giant+jellyfish&t
otal=103&start=0&num=10&so=0&type=search&plindex=0
Where did they come from?
The earliest known cnidarians also date to the
Precambrian, about 630 million years ago.
The earliest coral species were not reef
builders, so reefs cannot be used to date
early cnidarians.
The larval form of cnidarians resembles
protists, and because of this, scientists consider
cnidarians to have evolved from protists.