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Learning Guides |
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The material below is a pre/post visit activity guide
for parents and teachers. |
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Jellies |
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Jellies
are not really fish at all. Instead,
they are floating plankton -- creatures that ride the ocean's currents.
They have no eyes, no brain and no heart.
In fact, they are almost 97% water, which makes them nearly
transparent, and practically invisible to predators. There
may be very little to a jelly -- but there are plenty of jellies in the
sea. All in all, there are
about 200 species of jellies, and they live in every ocean on Earth.
Although they seem (and are) fragile animals, they are protected
from harm by their watery surroundings which support them and carry them
along. Getting
Around Most
of the time, jellies just float along on the ocean's currents.
In this way, they use very little energy to travel long
distances, collecting food as they go. Sometimes, hitching a ride on a wave can be dangerous -- as
you may know if you have ever seen jellies stranded on a beach. Jellies
can swim on their own, too, through a form of jet propulsion.
Each time they pulse, they send a stream of water out of their
bells, shooting them forward. Jellies may swim to the surface of the ocean at night to eat,
and then back to the darker regions to hide during the day.
They may also swim to gather together to mate, or just to stay
warm in the sunlight. Jelly
Food Most
people are aware that jellies can sting.
In fact some jellies, like the Portuguese Man of War, can sting
with enough venom to make a person sick.
Jellies keep their stings on their long tentacles, and use them
to paralyze or kill their prey. The
Portuguese Man of War has more than 2,000 stinging cells per inch of
tentacle. Jellies' favorite
foods include larval fishes and invertebrates, tiny shrimplike animals,
and even other jellies. Jelly
Babies An
adult jelly, also called a medusa, looks like the jellies in the
tank at the Aquarium: they have a bell, long tentacles, and a belly.
These adults gather together and reproduce sexually, by combining
the sperm of the male with the egg of the female. Jelly
babies, however, look nothing at all like their parents.
They begin as larvae, tiny creatures whose sole purpose is
to attach themselves firmly to a solid surface like rock.
Soon, the larvae grow to resemble tiny flowers; these flowers, or
polyps, are so hard to find and identify that many species have
yet to be discovered. The
amazing polyps reproduce themselves many times through a process called cloning.
Then, these clones produce free-swimming baby jellies called ephyrae.
Polyps may keep producing jellies for years, sending the tiny new
ephyrae out to make their way in the ocean. Jellies
at the Aquarium All
of the jellies at the New Jersey State Aquarium are Moon Jellies, found
off the coast of New Jersey. Moon
Jellies can grow to be over a foot in diameter, and they may be found in
the water near New Jersey's beaches late in the summer.
They have horseshoe-shaped sex organs, where there eggs or sperm
are formed. It
can be difficult to provide a home for jellies, because they are so
easily damaged. The jelly
tank must be engineered with currents that keep the jellies from
striking the walls and injuring themselves. Do
It! Recreate the life cycle of the jelly in a shoebox diorama as a science project or for fun. First, create an undersea landscape using rocks, sand and plants. Then, place your jellies in their home. Remember, a larva is a tiny creature attached to a rock, and a polyp looks like a little flower growing out of the rock. Polyps reproduce themselves very fast, so your diorama might include many polyps. A new jelly, called an ephyra, looks something like a flattened plastic bag, and a medusa looks very much like a half-full plastic bag with streamers. Finally, make sure your ephyrae and medusae swim clear of rocks and other hazards. |