Name: Jelly Fish
Scientific Name: Aurelia aurita (Common jellyfish)
are members of the phylum Cnidaria, a structurally
simple marine group of both fixed and mobile animals: sea
anemones, sea whips, corals and hydroids are polyps that grow
attached to rocks or other hard surfaces; jellyfish and colonial
siphonophores like the Portuguese man-of-war are mobile
(either actively swimming or subject to winds and currents).
a brain, jellyfish possess an elementary nervous system, or
nerve net, which consists of receptors capable of detecting
light, odor and other stimuli and coordinating appropriate
are composed of an outer layer (epidermis), which covers the
external body surface, and an inner layer (gastrodermis),
which lines the gut. Between the epidermis and gastrodermis
is a layer of thick elastic jellylike substance called mesoglea
("middle jelly"). Jellyfish have a simple digestive cavity,
(coelenteron), which acts as a gullet, stomach and intestine,
with one opening for both the mouth and anus. Four to eight
oral arms are located near the mouth and are used to transport
food that has been captured by the tentacles to the mouth.
inhabit every major oceanic area of the world and are capable
of withstanding a wide range of temperatures and salinities.
Most live in shallow coastal waters, but a few inhabit depths
of 12,000 feet!
are carnivorous, feeding mostly on a variety
of zooplankton, comb jellies and occasionally other jellyfish.
Larger species, however, are capable of capturing and devouring
large crustaceans and other marine organisms.Some species,
including the mushroom and cannonball jellyfish, are even
considered a delicacy by humans. Pickled or semi-dried mushroom
jellyfish are consumed in large quantities in Asia,
where they constitute a multimillion-dollar part of the seafood
Types of Jellyfish
Moon Jelly(Aurelia marginalis)
adult jellyfish drifts in the water with limited control over
its horizontal movement. It is, however, endowed with muscles
that allow it to contract its bell, reducing the space under
it and forcing water out through the opening. This pulsating
rhythm allows for regulation of vertical movement. Because
jellyfish are sensitive to light, this vertical movement can
be important. Some jellyfish, like the sea wasp, descend to
deeper waters during the bright sun of the midday and surface
during early morning, late afternoon and evening.
Special Features or Habits
are equipped with a specialized venom apparatus (cnidoblast)
for defense and feeding. A capsule (nematocyst) inside the
cnidoblast contains a trigger and a stinging structure. The
stinging structure varies according to species but generally
consists of a hollow coiled thread with barbs lining its length.
Nematocysts are concentrated on the tentacles or oral arms.Nematocysts
are activated when tentacles make contact with an object.
usually paralyze or kill only small creatures (fish, small
crustaceans), but some jellyfish are harmful to humans. Although
jellyfish do not "attack" humans, swimmers and beachcombers
can be stung when they come into contact with the jellyfish
tentacles with functional nematocysts.
Treatment of Sting
first aid for any jellyfish sting should be to minimize the
number of nematocysts discharging into the skin and to reduce
the harmful effects of the venom.A variety of substances have
been used to reduce the effects of jellyfish stings. Meat
tenderizer, sugar, vinegar, plant juices and sodium bicarbonate
have all been used with varying degrees of success.
should be taken when swimming in areas where dangerous jellies
are known to exist or when an abundance of jellies of any
type is present. Keep in mind that tentacles of some species
may trail a great distance from the body of the organism and
should be given lots of room.Rubber skin-diving suits offer
protection against most contact.