http://www.edhelperblog.com/cgi-bin/vspec.cgi
Jellyfish
1
Shaped like umbrellas, jellyfish are free-spirited
swimmers. Sometimes they swim by contracting
their muscles to push them forward, but other times
they just drift to wherever the water currents take
them. While nearly all jellyfish live in the ocean, a
number of them take up residence in freshwater
lakes.
2
Despite their name, jellyfish are actually not
fish! Jellyfish are made up of over 95% water, and
they do not have brains, hearts, gills, bones, or
blood. So, if jellyfish are not fish, what are they?
Jellyfish belong to an animal group called
invertebrates, because they do not have backbones. Fish are vertebrates, because
they have backbones.
3
There are more than 200 different species of jellyfish in the world. They come in a
variety of sizes and colors. Lion's mane jellyfish are the largest species of jellyfish their bells (jellyfish's round, umbrella-like bodies) can reach 8 feet across and their
tentacles can be more than 200 feet long! Most jellyfish have see-through bells in all
sorts of colors. Some even glow in the dark!
4
A jellyfish starts its life as a larva. It floats around until it attaches to a hard
surface, such as a rock. Once settled, it begins its second stage of life - the polyp
stage. In this stage, a polyp looks nothing like a jellyfish, and two amazing cloning
processes take place -
5
First, each polyp reproduces new polyps, just like a tree grows new branches.
New polyps eventually detach from the "parent" polyp and settle nearby to form
colonies of polyps.
Then, each polyp begins to form horizontal grooves. These grooves get deeper as
time goes on until they cut through the polyp. At this time, a polyp looks like a
stack of coins with each coin representing a baby jellyfish.
6
Stacks of baby jellyfish break off and swim away during the third stage, the
ephyrae (pronounced "e-FIE-ruh") stage. After they form their tentacles and oral
arms, they are in their last and final development stage, the medusa stage.
7
Jellyfish feed on small, floating animals such as baby shrimps, fish larvae, or other
jellyfish. Collectively, these small creatures are known as zooplankton. Jellyfish use
their tentacles, covered with "sting cells", to trap and capture prey. Each sting cell has
a highly sensitive trigger and a hollow capsule called nematocyst (pronounced
"nee-MAT-o-sist"). Inside the nematocyst is a coiled, barbed thread that looks like a
1 of 3
24/10/2006 8:43 PM
http://www.edhelperblog.com/cgi-bin/vspec.cgi
harpoon. When the prey moves around and touches the trigger, the nematocyst
uncoils and fires from the capsule, pierces the victim's skin, and injects the toxin.
Small animals stand no chance when being stung by hundreds or even thousands of
nematocysts. Jellyfish use their tentacles and oral arms to bring the paralyzed or dead
animals into their mouths. In fact, what make jellyfish so famous (or fearful) are their
stings. Although not all jellyfish are harmful to humans, several are quite poisonous or
even deadly! For example, we may die within minutes after being stung by sea wasps
(or Australian box jellyfish). Because sea wasps are transparent, it is difficult to avoid
them. We don't have the slightest clue that a sea wasp is around until we have the
fatal encounter!
Copyright © 2006 edHelper
2 of 3
24/10/2006 8:43 PM
http://www.edhelperblog.com/cgi-bin/vspec.cgi
Name _____________________________
Date ___________________
Jellyfish
1. What do jellyfish and fish have in common?
Both have gills.
Both live in the water.
Both have hearts.
Both have backbones.
2. Which of the following is the world's largest
jellyfish species?
Lion's mane jellyfish
Common jellyfish
Moon jellyfish
Australian box jellyfish
3. How many life stages does a jellyfish go
through?
Four
Five
Three
Two
4. Jellyfish can only be found in the ocean.
True
False
5. Which of the following is the right sequence of a 6. Jellyfish have hundreds or thousands of sting
jellyfish's life cycle?
cells on their tentacles.
Larva ==> Polyp ==> Medusa ==>
True
Ephyrae
False
Medusa ==> Ephyrae ==> Polyp ==>
Larva
Polyp ==> Larva ==> Ephyrae ==>
Medusa
Larva ==> Polyp ==> Ephyrae ==>
Medusa
7. Which of the following do jellyfish use to inject
the toxin into their prey?
Mouths
Oral arms
Nematocysts
Tentacles
8. Which of the following jellyfish species is so
poisonous that it can kill humans?
Common jellyfish
Lion's mane jellyfish
Moon jellyfish
Sea wasps
9. Which of the following statements about a
10. Which of the following best describes jellyfish?
jellyfish's life cycle is true?
There are no jellyfish in freshwater lakes.
A jellyfish clones itself during the ephyrae
Lion's mane jellyfish are the world's
stage.
deadliest jellyfish.
Stacks of jellyfish break off and swim away
Jellyfish use their tentacles and oral arms
during the medusa stage.
to bring food to their mouths.
A jellyfish clones itself during the polyp
Sea wasps are the world's largest jellyfish.
stage.
A jellyfish's last and final development
stage is the larvae stage.
3 of 3
24/10/2006 8:43 PM