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Cnidaria
Classification
JELLYFISH
Kingdom Animalia
Phylum Cnidaria
Class Scyphozoa – larger
jellyfish
 Class Hydrozoa – floating
colonies, Portuguese man-ofwar

Characteristics
Up to 99% water, often less
than 5% solid organic
matter
found all over the world , in
all types of seas, even
freshwater; found at all
depths
Characteristics
range in size from 1 inch
(Caribbean jelly) to the
(Arctic Lion’s Mane) with
tentacles as long as 100 ft.
More complex than
sponges, not as complex as
marine worms
Arctic Lion’s Mane
Presence of specialized
tissues that make it possible to
swim, respond to external
stimulus (light, smell) and
engulf prey; possess an
elementary nervous system or
nerve net.
Simple digestive cavity which
acts as a gullet, stomach, and
intestine w/one opening for the
mouth and anus
Most are found in the
medusa form – gas filled
domed bell
Have a centrally located
mouth surrounded by
tentacles used to capture
and handle food; have 4
to 8 oral arms near the
mouth, used to transport
food to mouth that is
captured by tentacles
Has radial symmetry, allows
jelly to respond to food or
danger from any direction
Have nematocysts on
tentacles and/or oral arms to
string/stun prey
A single tentacle can have
hundreds or thousands or
nematocysts embedded in the
epidermis
Have 2 layers, an epidermis
and gastrodermis with a thick,
elastic jellylike substance
(mesoglea) in between that
expands to form the domed
bell
Most jellyfish have a short
lifespan and may live for only a
few weeks, average lifespan 3
to 6 months
Feed on small plankton
type animals and small fish;
larger species capable of
eating large crustaceans
Jellyfish are preyed upon by
certain fish (spadefish,
sunfish) and loggerhead
turtles; Both fresh and
pickled mushroom jelly are
eaten as a delicacy in China
and Japan
Locomotion – most drift with
the currents with little control
over their horizontal
movement; there is some
ability to navigate vertically
some swim with rhythmic
contractions of the bell;
because jellyfish are sensitive
to light, vertical movement is
important to descend to
deeper depths during the day
Some have bioluminescence
Defense –
transparency helps to reduce
silhouette
 nematocycts

Sea wasp found in
Australia, SE Asia, and
Indian ocean has been
know to cause death in
human
Reproduction
Are either male or female and
reproduce sexually. The
reproductive organs (gonads)
develop in the lining of the gut.
During reproduction the
male releases sperm
through its mouth into the
water column. Sperm
swims into mouth of female
where fertilization occurs.
The larva is, either ‘brooded’
within the gut of the adult or
develops as a free-swimming
planula (larva w/ cilia).
The planula seek a shaded
surface and attaches itself
onto a substrate and develops
into a polyp. These polyps
divide and bud into a young
jellyfish (ephyra). In a few
weeks, and ephyra will grow
into an adult medusa.
Treatment of a Sting
Meat tenderizer, sugar,
vinegar, plant juices and
sodium bicarbonate have
all been used with
varying degrees of
success.
Methylated spirits and other
forms of alcohol formerly
recommended for inhibiting
stinging cells actually stimulate
them and may increase pain
and cause severe skin
reactions. Picric acid and
human urine also cause a
discharge of nematocysts and
should not be used.