may be the most common ocean animal, but are hard to catch in nets.
sting of some "jellies," such as this sea nettle (left), can be
deadly. Others are harmless to humans, but may cause
Here is a
jellyfish out of water! It looks like blob of jello when washed up on
the beach.Jellyfish breathe over the entire
surface of their bodies. Just as we breathe air, they breathe
water. We cannot breathe water, and they cannot breathe air!
of water Jellies are a gooey mess. So they could not fly through the
air, but in the water jellies are graceful. Some people might say
that jellies fly through the water! But even that would be wrong
since Jellies rely on the current and tides to carry them, they do
not fly at all!
This is an Arctic
Lion's Mane Jelly It is the largest of the Jellies! It can be 8 feet
across its bell, and its tentacles can reach 200 feet
of the smallest is also one of the most deadly. The Irukandji is only
about 1 1/2 inches across yet it is very poisonous. It is very
dangerous because it is transparent (nearly invisible). Sometimes
swimmers do not realize that they have been stung until the get very
Deadly is the Australian Box Jellyfish which can kill a human in 5
The Sea Wasp
(also called the Australian Box Jellyfish) in the ocean off
Australia is one of the deadliest animals on earth. It is
the Australian Box Jelly and one box jelly has enough venom
to kill 60 people! It is called a box jelly because its bell
is shaped like a box.
The one that
is held by the man is found in the Caribbean sea. It is a
smaller and less deadly than its Australian cousin. It is
abaout 2 x 3 inch "cube." Its four tentacles are about 12
inches long, one attached to the four bottom corners of its
The man can
safely hold the bell of the jelly. Only the tentacles that
have the poison!
Jellyfish are not
A jelly has no head,
brain, heart, eyes, nor ears. It has no bones, either. It is 95%
water! Scientists estimate there may be 2,000 species (kinds) of
jellyfish, but we are only familiar with 200. They have been drifting
through the world's oceans for more than 650 million
live where in the oceans. They drift with the currents. They live in
groups because the currents keep them together. Some live very deep
in the ocean and some, like the up-side-down jelly live nearer the
surface. Its tentacles reach up into the sea. It looks like a sea
anemone. The up-side-down jelly has algae growing in its tenticles so
it must live in shallow water. Algae needs sunlight to grow so it
must live near the surface. Jellys live in icy polar seas and warm
capture food, jellies have a net of tentacles that contain poisonous,
stinging cells called nematocysts. They use their tentacles like
harpoons. When you brush up against them they shoot them out and
inject the poison . When the tentacles brush against prey (or,say, a
person's leg), thousands of tiny stinging cells explode, launching
barbed stingers and poison into the victim. Here is a picture showing
the little threads coiled up and ready to unfurl and
carnivorous (eat meat).They eat mostly zooplankton, smaller fish and
sometimes other jellyfish. Bigger jellies eat large crustaceans (like
shrimp) and other sea animals.
are eaten mostly by spadefish, sunfish, and loggerhead turtles.
People in China and Japan like to eat the mushroom jellyfish. Both
fresh and pickled mushroom jellyfish are eaten. Here is a crab eating
a jellyfish. The crab is a crustacean - like the shrimp!
Ha! Fooled you. This is a man eating jellyfish --- hmmm.
jellyfish live only a year or less, but some like that giant
antarctic live 5-10years!.
Some jellyfish can
tigthen their bell and then make it bigger. This pulsating lets them
propel (push) themselves upward through the water. It is similar to
letting a filled balloon empty itself. It propels itself! Mostly they
must depend on the ocean currents and tides to move them about.
Currents are like rivers of water that flow through the ocean.
here and see pictures of a jellyfish "swimming".
Jellyfish do not have
a brain like us. They have a complex network of nerves which respond
to things, but they cannot think about things.
Jellyfish do not
communicate like we do, remember they do not have a brain or
language! BUT Some can flash colorful lights. Scientists think these
may be used to disguise them or even to attract prey. Jellyfish can
signal each other. One jellyfish releases chemicals when it is about
to breed. Other jellyfish then are stimulated to spawn at the same
time, so that the most jellyfish are born.
reproduce (have babies) in different ways. The moon jellyfish, which
is common along U.S. beaches, begins life as an egg in its mother's
mouth. The male jellyfish releases sperm into the water and it
fertilizes the egg. The female lets the larvae go and they attach to
something hard. They are now polyps and look more like sea
anemones than jellyfish. Finally these polyps develop tentacles and
let go of the bottom to become adult (medusa.) jellyfish.
baby jellyfish sting you?
When baby jellyfish
are first born they do not look much like jellyfish. Look at the
picture below. When the baby jellyfish reaches the Medusa stage it
uses its stingers to catch food! So the answer is no. Only as the
baby nears adulthood can it sting you.