Download Jellyfish

PHYLUM CNIDARIA
HYDRAS, JELLYFISH,
SEA ANEMONES,
CORAL, BOX JELLYFISH
I.
General Information
1. “Cnido” means nettle (stinging cell)
2. Ex: hydras, jellyfish, sea anemones, coral
3. Symmetry: Radial
4. Found in marine & freshwater
5. Diploblastic: two tissue layers
a. Ectoderm- develops into epidermis(skin)
b. Endoderm- develops into gastrodermis(gut cavity)
General
Body
Plans:
Basal disk
Polyp &
Medusa
II. Body Forms
1. Polyp
a. Cylindrical, column-like body
b. Mouth points up, surrounded by tentacles
c. Sessile, attached to surface by basal disc
2. Medusa
a. Bell or cup shaped body
b. Mouth points downward surrounded by
tentacles.
c. Free swimming- moves by gently pulsating
body
III. Digestion/Feeding
1.
Use cnidocyte containing
nematocyst on tentacles to
sting/stun prey
2.
Eat daphnia, protists, larva,
etc
3.
Stuff food into mouth using
tentacles at oral end.
4.
Food is digested by special
cells in the gastrodermis
that line the gastrovascular
cavity.
5.
Wastes leave thru mouth.
1. The cnidocyte contains the nematocyst- fluid filled
capsule with coiled thread.
2. Prey trigger the cnidocil (trigger hair), operculum (lid)
opens & thread containing barbs stabs/entangles
prey.
3. Cnidocyte degenerates & a new one takes its place
IV. Respiration
1. DIFFUSION through cell membranes directly
exposed to water.
-Cnidarians obtain oxygen from water
and it diffuses directly through tissues
-Wastes are also eliminated by diffusion
but solid wastes are discharged through
the mouth
-The gastrovascular cavity functions as a
transport system; cavity circulates fluid
through the organism by squeezing the
body wall which pushes water in and
out of the body.
V. Skeleton/support
1. Hydra & sea anemones have
a hydrostatic skeleton- fill
gastrovascular cavity
w/water. Gives support
2. Aids in movementsomersaults, (inchworm)
3. Jellyfish mostly float
w/currents
4. Coral are sessile
VI.Nervous System
1. Nerve net- layer of
nerve cells in mesoglea(gelatinous middle layer)
that react to stimuli.
2. Most primitive form of
nervous system in
animal kingdom.
3. Jellyfish consist of cells
called statocystssenses gravity, aids in
balance, coordinates
movement
VII. Excretion
1. Through mouth or directly into water from
cells.(diffusion)
VIII. Reproduction
1.
Asexual
a. Budding- hydra, coral, anemones
2.
Sexual
a. Monoecious- hermaphrodite, “one
house” Ex. hydra
b. Dioecious- sperm & egg are
produced in separate sexes.
Ex. jellyfish
IX. Jellyfish Life Cycle
1. Sperm released by male medusa.
Egg released by female.
2. Sperm & egg join to form zygote.
3. Zygote goes through several cell
divisions & forms a hollow ball of
cells called a blastula.
4. Blastula eventually forms into a free
swimming larva called a planula.
5. Planula lands on a structure &
begins to grow into a polyp.
6. Polyp buds break off & grow into
free swimming medusa.
X. Classification
Craspedacusta sowerbyi
Class Hydrozoa
* marine & fresh water
* can live as single animal or colony
* may be polyp or medusa
* gametes made on outside of body
* Ex. hydra, Portuguese man-o-war
Class Scyphozoa
* all marine
* predominant medusa stage
* gametes made internally & released
thru mouth
* called “true jellyfish”
* Ex. Aurelia
Lions Mane Jelly
Class Anthozoa
* all marine
* solitary or colonial polyps
* budding or can be monoecious or
dioecious
* anthozoa means “flower animal”
* Ex. sea anemone, coral
Class Cubozoa
* all marine; found in warm tropical water
* medusae are cube shaped; tentacles
hang down from each corner
* have deadly poison
each tentacle has 500,000 cnidocytes;
deaths in Japan, Australia, Malaysia,
Gulf of Mexico; victims suffer severe
physical and psychological symptoms )
* Ex. sea wasp (box jelly)
XI. Economic/Environmental
Significance
1. Part of food chain
2. Control animal
populations
3. Coral provide habitat for
other animals in reefs
4. Some corals provide
medicines & jewelry
Ex. Cancer, arthritis,
histamines, antibiotics
1. The stinging cell of the cnidarian is called
a. cnidocyte
b. amoebocyte
c. gland cell
2. Jellyfish have both a sexual & asexual stage
to their life cycle. a. True
b. false
3. Jellyfish are an example of which body form?
a. polyp
b. medusa
4. The place where food is digested & gases are
exchanged is called the
a. spongocoel b. gastrovascular cavity c. gland cell
5. The sticky adhesive base of a sea anemone is
a. spongocoel
b. gastrodermis
c. basal disc
DAILY QUIZ
• JOURNAL #2:
– Describe what a cnidocyte is AND how it
works.