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Cnidarians are a large group of animals that all have things in common.
They include jellies, corals and anemones.
Cnidaria 1

2. Jellyfish or Jelly…not a fish
01/16/13
Jellyfish or Jelly…not a fish
Jellies are cnidarians-- jellies have soft bodies made up mostly of water, and often are surrounded by venomous tentacles (that can be long or short) that they use to capture prey in the ocean water.
Some jellies eat plankton and others eat fish. 2

3. Looks like, but isn’t a jelly!
01/16/13
Looks like, but isn’t a jelly!
Here is a close up of the tentacles of something that looks like a jelly, but actually is not a jelly at all. It is another type of cnidarian, a siphonophore. Siphonophores are colonies of very specialized organisms that function together. This siphonophore is called a Portuguese man-of-war because its float looks a bit like the old sailing ships. It is a colony of organisms--4 separate organisms working together….one serves as the float, one as tentacles, one ingests food that provides energy to all four, and the last serves as the reproductive organs.
The man of war floats on the surface of the ocean and dangles its tentacles below to attract curious fish. If a fish gets too close, the venom from the tentacles paralyzes the fish and then the siphonophore will eat it. 3

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Sea Anemones
Sea anemones are cnidarians too! They are different than jellies because instead of floating in the water, they stick themselves to hard surfaces.
They have sticky tentacles around their mouths that they use to capture prey.
Sea anemones are omnivores– they will eat almost anything that comes across their tentacles. 4

5. Corals
01/16/13
Corals are another member of the cnidarians. They are grouped in with jellies and anemones because they have the same life cycle.
Corals are soft animals living in a hard skeleton that they make themselves.
When you touch coral it feels hard, but if you look closely you can see holes inside the skeleton, which is where the soft bodied animal lives.
Corals form reefs, which are important habitats for fish and other animals. 5

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L- anemone
R- jelly
These two animals are in the same family because they have similar body plans--just one is upside down from the other! 6

7. Lifecycle
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Egg
Cnidarians have a variety of reproductive strategies, but most follow a basic pattern: they start off as a fertilized egg, and then change into a kind of plankton called a planula that eventually chooses a place to settle, where it grows into a colony. A bud grows off of the colony and turns into a free swimming medusa which then releases eggs and sperm. The medusa stage is larger for some groups, such as jellies. 7

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Budding
Some cnidarians also reproduce in a very special way called budding. This means that they can split their body into two identical copies! 8

9. Nematocyst (stinging cell)
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Nematocyst (stinging cell)
You may have heard that touching a jellyfish can cause a sting.
These animals have special cells in their body that get triggered when touched, to release a long spring with a tiny (but sharp) end that pokes.
They use this adaptation to capture prey and to avoid getting eaten. 9

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MORE Jellies
Cnidarians come in all shapes and sizes. Here are some more interesting kinds of jellies! 10

11. Moon Jelly
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The moon jelly has short tentacles, that it uses to capture tiny plankton from the water. 11

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Comb Jelly
The comb jelly has rows of tiny combs along its body that it uses to move around.
This animal is a very weak swimmer though, and is usually at the mercy of ocean currents. 12

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By-the-wind Sailor
This is another colony of organisms. The By-the-Wind Sailor’s curved sail catches wind at the surface of the water to move around like a sailboat. The wind often concentrates large groups. During spring and early summer, groups are sometimes found washed ashore along Charleston beaches. 13

14. 01/16/13
Nomura’s Jellyfish
These are some of the biggest jellyfish in the world– they live in Asia.
They often get caught in fishing nets, causing lots of trouble for fishermen. 14

15. Brown Sea Nettle Jellyfish
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Brown Sea Nettle Jellyfish
This is a jelly that sometimes can be found right here in Charleston! 15

16. 01/16/13
Red Eye Medusa
This jelly is also found in Charleston. It moves by closing and opening its bell, which pushes water out, shooting it forward. 16

17. Arctic Lion’s Mane Jelly
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Arctic Lion’s Mane Jelly
The lions mane jellyfish is the largest cnidarian in the world!
It uses its tentacles to capture fish and even other jellies!
Up to 120 feet long, 7 feet wide 17

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MORE Anemones
Anemones come in different shapes and sizes too. 18

19. 01/16/13
Giant Green Anemone
This anemone is green because it has a kind of algae in its body that helps it get energy from sunlight. It also feeds on bits of algae and small animals that get stuck to its tentacles. So it is an animal with plants growing inside it!
These animals can be found in tidepools in Charleston. 19

20. 01/16/13
Brooding Anemone
This anemone grows its babies on itself, at the base of its tentacles. 20

21. Pink-tipped Anemone 01/16/13 Does this look farmiliar? 21 21

22. Merten's carpet sea anemone
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Merten's carpet sea anemone
This is a tropical anemone that is a very different shape than the round anemones we saw earlier. 22