Station 1

THE STINGING CELLS

Jellyfish, sea anemones, and corals all have cells in the epidermis tissue layer of their tentacles called cnidocytes (“stinging cells”). Coiled within these cnidocytes ready to be explosively launched are nematocysts (“stinging threads”). When a mechanical or chemical stimulus reaches the cnidocyte, the cell opens, releasing the venomous nematocyst. The animal can also coordinate the firing of many nematocysts at one time using nerve impulses. On average, the animal loses 25% of its stinging cells with each capture or attack. Since the nematocysts are only used once, the cnidarian regenerates the cells in about 48 hours.

There are three types of stinging threads in cnidarians. The first is called penetrating, because it actually enters the victim’s skin and releases its toxin inside the animal. The second type of nematocyst is non-penetrating. This type of stinging thread coils around and entangles its victim. The third kind of stinging cell is adhesive, sticking to the surface of its victim. Almost all nematocysts have some type of barbs or hooks.

Station 2

PORTUGUESE MAN-OF-WAR

The Portuguese Man-of-War is called a Siphonophore. It is a member of Class Hydrozoa in Phylum Cnidaria. This impressive animal is actually a colony of thousands of polyps and medusas. Various polyps in the Man-of-War form the feeding tentacles with nematocysts, the “feeling” tentacles, and reproductive structures. The medusas in the animal form the gas-filled lfoat, as well as the other reproductive structures.

The Man-of-War has a special gland within its float that secrete carbon monoxide (CO) gas. Some siphonophores (but not the Man-of-War) can regulate the amount of gas in the float so they can sink below violent waves during a storm. This cnidarian has a powerful sting that affects the nerve cells of its victim. In humans, the sting produces burning, blistering, and muscle cramps. Incredibly, there are certain kinds of fish that appear to have a tolerance for the Man-of-War’s toxin. These fish live unharmed within the jellyfish’s tentacles.

Station 3

SEA ANEMONE ANATOMY

The sea anemone is a member of Class Anthozoa in the Phylum Cnidaria. These animals are usually around 2-4 inches in length, but can reach 1 meter in width!! The sea anemones are usually brightly colored, living in coastal waters attached to rocks or other hard surfaces. They live in both warm and cool waters. Some sea anemones live attached to other animals, such as crabs, in symbiotic relationship.

The sea anemone is one of the most complex cnidarians, with well-developed muscles and nerve cells. The base of the anemone, where it attaches itself to a surface, is called the basal or pedal disc. The animal uses a mucus substance as glue. The mouth is on top of the anemone, surrounded by tentacles. The mouth is slit shaped, with a ciliated groove at each end called a siphonoglyph. The siphonoglyph helps circulate water into the anemone for support and gas exchange. The mouth leads into the anemone’s pharynx or digestive chamber. The anemone has a thick mesoglea for extra support since it does not have a hard skeleton.

Station 4

THE SEA ANEMONE

The sea anemone is a member of Class Anthozoa in Phylum Cnidaria. It lives in the polyp form, attached to a surface with its tentacles pointing up. These cnidarians usually feed on fish or small invertebrates. Their prey becomes paralyzed from the nematocyst’s toxin and caught in the tentacles. Then the anemone carries the food to its mouth using the tentacles.

Sea anemones frequently form symbiotic relationships with small reef animals, such as cleaning shrimp, clown fish, brittle stars, and snapping shrimp. Scientists believe that these animals coat themselves in the anemone’s mucus. The tentacles then “recognize” the symbiotic animal as part of the anemone, and the animal does not get stung. Usually, the reef animal benefits by eating the anemone’s leftovers. The anemone benefits because the reef animal acts as a decoy, attracting other animals that the anemone will eat.

Station 5

THE CNIDARIAN COLLECTION

Station 6

SEXUAL REPRODUCTION IN CORALS

Coral gonads produce enormous amounts of eggs and sperm that are usually released directly into the water. After fertilization, a free-swimming larva forms. The larva finds a hard surface to attach to. It then begins dividing to form a colony. A coral is actually made of many polyps that are all divided from one original fertilized egg.

Coral spawning (releasing eggs and sperm) is sometimes synchronized with the tides to achieve a wide dispersal of their offspring. Also, some coral species have an annual mass spawning, when the water literally fills with their eggs and sperm. At this time, one can see a blanket of floating eggs and a musky odor fills the air.

Station 7

THE CORAL COLLECTION

Coral is a member of Class Anthozoa in the Phylum Cnidaria. These spectacular “flower animals” form the reefs along tropical coasts around the world. The coral is actually a colony of tiny (1-3 mm) polyps. The reefs are formed by the calcium carbonate (limestone—CaCO3) skeletons that the coral animals secrete. This skeleton serves two purposes for the animal. First it provides a surface for the polyp to attach to. Second, the animal can withdraw into the limestone, giving it plenty of protection. This skeleton is constantly being added to. The polyps are connected by a tissue that lays over the hard surface.

Corals come in a great variety of shapes: branching, plate-like, flat, round, brain-like, and mushroom-like. The different forms grow at different rates, with the branching growing the fastest. The coral polyps eat zooplankton and small fish, feeding mostly at night.

Station 8

VARIOUS CORAL SAMPLES

A. Tongue coral—large polyp stony, has many mouths, with larger mouth around central furrow, short tentacles (<2 cm) usually forked, active during the day.

B. Staghorn coral—can grow to 10 feet in height and 60 inches wide, yellow or purple, found around the Caribbean.

C. Star coral—can grow to 60 inches wide, actively feeds on plankton, green or yellow-brown.

D. Brain coral—polyps are interconnected in rows making it look like a human brain.

E. Mushroom coral— solitary, does not live in colonies, can withdraw into ‘mushroom’ one polyp.

B

A

C

D

Station 9

THE BOX JELLYFISH AND THE LION’S MANE

Station 10

THE GORGONIANS

The members of the Order Gorgonacea in Class Anthozoa, Phylum Cnidaria include the pipe-organ coral and the sea fan. These are very common along the coral reef. These flexible animals move with the water and look like plants. The sea fan usually grows so that it is arranged at right angles to the water current.

Station 11

ZOOXANTHELLAE

Many cnidarians “farm” plants within their own tissues. By having zooxanthellae (photosynthetic cells) living symbiotically in their bodies, they can directly benefit from the products of photosynthesis. Remember,

Coral animals that form the reef are especially in need of the zooxanthellae. These microorganisms provide materials needed to make the limestone skeleton, as well as nutrition from the sugar byproducts of photosynthesis.

THE CNIDARIANS LAB

Station 1- The Stinging Cells

1. Examine the pictures of cnidocytes/ nematocysts. Draw and label both.

2. Define cnidocyte. ____________________________________________________________________________

3. Define nematocyst. __________________________________________________________________________

4. List three things that may cause the stinging cells to fire off. __________________________________________

___________________________________________________________________________________________

5. List the three kinds of nematocysts in cnidarians. ___________________________________________________

___________________________________________________________________________________________

Station 2- The Portuguese Man-of-War

6. The Man-of-War is a _______________ in the Class ______________ in the Phylum ___________________.

7. Polyps in the Man-of-War form: _______________________________________

8. Medusas in the Man-of-War form: _____________________________________

9. _______________________ is the gas in the float of the Man-of-War.

10. List the effects of a Man-of-War sting on humans. ___________________________________________________

___________________________________________________________________________________________

Station 3- Sea Anemone Anatomy

11. Examine the sea anemone specimen. Locate and draw the mouth, pedal disc, siphonoglyph, pharynx, and tentacles in the box to the right.

12. List three general characteristics of sea anemones. __________________

____________________________________________________________

13. How do you think a crab and a sea anemone could both benefit from their symbiotic relationship? _________________________________________

____________________________________________________________

14. Why is water circulation necessary for the sea anemone? _____________________________________________

15. Why is the sea anemone’s mesoglea extra thick? ___________________________________________________

___________________________________________________________________________________________

Station 4- The Sea Anemone

16. Describe the steps in sea anemone feeding. ________________________________________________________

___________________________________________________________________________________________

17. Why aren’t the animals that live in the anemone stung by the tentacles? ________________________________ ___________________________________________________________________________________________

18. How do the anemone and a small reef animal both benefit from a symbiotic relationship? _________________ ___________________________________________________________________________________________

19. What type of symbiotic relationship is it when both organisms benefit? _________________________________

Station 5- The Cnidarian Collection

20. Examine the cnidarian collection compare and contrast in the venn diagram to the right.

21. Cnidarians have __________ symmetry. All the cnidarians have _____________ around their mouths.

22. Draw the horseshoe shaped reproductive structures on the bell of the Aurelia jellyfish below.

23. Another name for gastrovascular cavity is __________.

Station 6- Sexual Reproduction in Corals

24. A coral is actually made of many ___________________ that are all ___________________.

25. Define spawning. _____________________________________________________________________________

26. List two ways coral animals try to improve their chances of successful reproduction. _______________________ ___________________________________________________________________________________________

Station 7- The Coral Collection

27. The coral is actually a ____________________ of tiny _____________________.

28. Calcium carbonate is also called ___________________________ or _______________________________.

29. List the two functions of the coral skeleton. ________________________________________________________ ___________________________________________________________________________________________

30. How are the polyps connected? _________________________________________________________________

31. List 5 different coral shapes. ____________________________________________________________________ ___________________________________________________________________________________________ ___________________________________________________________________________________________

32. List 3 types of corals in the specimen box. _________________________________________________________ ___________________________________________________________________________________________

Station 8- Various Coral Samples

33. Examine the mushroom coral. The photograph on the information sheet shows a mushroom coral also. The coral on the left has its tentacles withdrawn. The one on the right has them extended. How is the mushroom coral different from most other corals we have studied? _____________________________________________ ___________________________________________________________________________________________

34. The staghorn coral can grow up to __________ in height and is _________________ in color.

35. How are the polyps of the brain coral arranged? ____________________________________________________

Station 9- The Box Jellyfish and the Lion’s Mane

36. Examine the National Geographic article called “A Killer Down Under.”

a. P. 116- Contact with box jellyfish’s tentacles can bring death within ________ minutes.

b. P. 120- When fully grown, the box jellyfish may stretch _________ feet.

c. P. 122- They are about ________% water.

d. P. 122- Swimmer in Australian waters are urged to use only _______________ and to wear __________.

e. P. 130- The ___________________________________ snacks on the box jellyfish.

37. Examine the handbook’s photo and information about the lion’s mane jellyfish.

a. What is the size of the lion’s mane jellyfish? ____________________________

b. Where does this jellyfish live? _______________________________________________

Station 10- The Gorgonians

38. How is the sea fan different from the other types of coral we have studied? ______________________________ ___________________________________________________________________________________________

39. Why do you think the sea fan usually grows at right angles to the direction of the water current? _____________ ___________________________________________________________________________________________

Station 11- Zooxanthellae

40. Define zooxanthellae. _________________________________________________________________________

41. Write the chemical equation for photosynthesis. ____________________________________________________

42. What are two things that the zooxanthellae provide for reef-building coral animals? _______________________ ___________________________________________________________________________________________

43. What benefit do you think the zooxanthellae receive from the coral animal? _____________________________ ___________________________________________________________________________________________

polyp

medusa