The Gulf of Mexico Deepwater Habitats Expedition Architects of the Deep Reef FOCUS SEATING ARRANGEMENT Reproduction in Cnidaria Groups of 2-4 students GRADE LEVEL MAXIMUM NUMBER OF STUDENTS 5-6 (Life Science) 30 FOCUS QUESTION KEY WORDS What reproductive strategies might be used by the Lophelia pertusa deep-sea coral Lophelia pertusa? Cnidaria Nematocyst LEARNING OBJECTIVES Zooxanthellae Students will be able to identify and describe at Medusa least five characteristics of Cnidaria. Polyp Planula Students will be able to compare and contrast the Anthozoa four classes of Cnidaria. Hydrostatic skeleton Students will be able to describe typical reproduc- BACKGROUND INFORMATION tive strategies used by Cnidaria. Deep-water coral reefs were discovered in the Gulf of Mexico nearly 50 years ago, but very little is Students will be able to infer which of these strate- known about the ecology of these communities or gies are likely to be used by the deep-sea coral the basic biology of the corals that produce them. Lophelia pertusa, and will be able to describe the In contrast, deep-water coral reefs near the coasts advantages of these strategies. of Europe have been intensively studied, and scien- tists have found a great abundance and variety of MATERIALS species associated with these communities. Lophelia Drawing materials for making posters pertusa is the dominant coral species in these communities. Technically, Lophelia is ahermatypic AUDIO/VISUAL MATERIALS (non-reef-building), but branches of living coral Chalkboard, marker board with markers, or over- grow on mounds of dead coral branches that can head transparencies for group discussions be several meters deep and hundreds of meters long. Unlike hermatypic corals that produce reefs in TEACHING TIME shallower waters, Lophelia does not have symbiotic One 45-minute class period, plus time for student algae and receives nutrition from plankton and research and for making posters particulate material captured by its polyps from the 1 The Gulf of Mexico Deepwater Habitats Expedition – Grades 5-6 (Life Science) The Gulf of Mexico Deepwater Habitats Expedition – Grades 5-6 (Life Science) Focus: Reproduction in Cnideria oceanexplorer.noaa.gov oceanexplorer.noaa.gov Focus: Reproduction in Cnideria surrounding water. Lophelia mounds alter the flow ductive strategies used by different groups within of currents and provide habitats for a variety of this phylum, and the ecological advantages of filter feeders. Several commercially-important spe- these strategies. cies are associated with Lophelia reefs in European waters, and scientists suspect that the same may LEARNING PROCEDURE be true for deep-water reefs in the Gulf of Mexico. 1. Briefly review background information on the But they don’t know for sure, because most of these Gulf of Mexico Deepwater Habitats Expedition, communities are almost entirely unexplored. and deep-water reefs. Be sure students under- stand that these reefs have a high diversity of Most reports of Lophelia reefs in the Gulf of Mexico species and large number of individual organ- were the result of investigations directed toward isms like coral reefs in shallower water, but hydrocarbon seepage and/or chemosynthetic com- are virtually unexplored in the Gulf of Mexico. munities. Scientists studying deep-water reefs on Compare and contrast deep-water reef corals the Norwegian continental shelf have found that (e.g., Lophelia pertusa) with reef-building corals many large Lophelia banks occur at sites where in shallow water. Visit http://oceanexplorer.noaa.gov/ there were relatively high levels of light hydrocar- explorations/islands01/background/islands/sup10_lophelia.html bons present in the sediments. The reason for this for more background on Lophelia reefs. Explain correlation is not known, nor is it known whether that very little is known about the life history of a similar correlation exists in the hydrocarbon-rich Lophelia pertusa, but this information is very Gulf of Mexico. important to understanding the best ways to protect Lophelia reefs. Discuss how the scientific As scientists have begun to learn more about method could be used to help learn more about Lophelia reefs, there is increasing concern that how these corals reproduce: scientists review these reefs and their associated resources may be what is known about similar organisms, develop in serious danger. Many investigations have report- one or more hypotheses about reproduction in ed large-scale damage due to commercial fishing Lophelia, and then devise experiments to test trawlers, and there is also concern about damage these hypotheses. Tell students that their assign- that might result from exploration and extraction ment will be to work through the first two steps of of fossil fuels. The primary objectives of the Gulf of this process. Mexico Deepwater Habitats Expedition are: • to locate deep-water coral reefs in the Gulf of 2. Tell students that corals are members of the phy- Mexico; lum Cnidaria, and that their assignment is to: • to describe biological communities and geolog- ical features associated with these reefs; and (a) Prepare a written report that will include: • to improve our understanding of the ecology of • at least three characteristics of cnidarians; Lophelia and deep-water reef communities. • descriptions of the four classes of this phylum, with drawings or photographs of a typical ani- One of the secondary objectives of this expedi- mal of each class; tion is to begin to gather information about how • descriptions of different reproductive strategies Lophelia corals reproduce. This information is criti- used by cnidarians; and cal to finding possible ways to restore damaged • a discussion of the most likely reproductive reefs, as well as to understanding interactions strategy or strategies used by Lophelia pertusa, between Lophelia pertusa and other organisms in and what advantages this strategy or strategies deep-reef communities. This lesson is intended to might offer to this species. introduce students to the phylum Cnidaria, repro- 2 3 The Gulf of Mexico Deepwater Habitats Expedition – Grades 5-6 (Life Science) The Gulf of Mexico Deepwater Habitats Expedition – Grades 5-6 (Life Science) Focus: Reproduction in Cnideria oceanexplorer.noaa.gov oceanexplorer.noaa.gov Focus: Reproduction in Cnideria (b) Prepare a poster illustrating the life history on small particles of detritus and plankton, but that they hypothesize for Lophelia pertusa. others are able to capture and eat large prey; • some cnidarians, including many corals, have You may want to suggest that students visit http:// symbiotic single-celled algae called zooxan- www.vims.edu/bridge/otherinverts.html as a starting point thellae that produce food by photosynthesis; for their research. the cnidarians are able to use this food, and provide the zooxanthellae with protection and 3. Have each group present a summary of their simple minerals; findings. Tabulate key facts about Cnidaria on a • many cnidarians, including many corals, are chalkboard, marker board, or overhead trans- colonial, with many individual animals living parencies. These facts should include: together as one organism; • ‘Cnidaria’ means ‘stinging nettle’ in Greek; • cnidarians maintain their shape with fluids • there are four classes of Cnidaria: Anthozoa inside their bodies (this is called a hydrostatic (corals, anemones, and sea pens), Cubozoa skeleton); (highly toxic box jellies), Hydrozoa (hydroids, • some cnidarians also produce a hard internal fire corals, and animals resembling jellyfish like skeleton of limestone (this is what makes some the Portuguese man-of-war), and Scyphozoa of the “rocks” that form coral reefs); (true jellyfish); • some corals are used to make jewelry; coral • all cnidarians live in water; reefs protect many coastal areas from erosion • cnidarians are radially symmetrical; and storm damage, provide habitat and nurs- • there are two body plans among the Cnidaria: ery areas for fishes that provide food for many the medusa is the “jellyfish plan” with an people around the world, and support tourist umbrella-shaped body having the mouth fac- industries in many countries; some reef-dwell- ing downwards, surrounded by tentacles; the ing organisms are the source for important polyp is the “flower plan” with a mouth facing pharmaceuticals; upwards and also surrounded by tentacles; the • the life cycle of many cnidarians includes a other end of the polyp is usually attached to a polyp phase as well as a medusa phase; in fixed surface; Anthozoa (which include Lophelia pertusa), • cnidarians have a distinct upper and lower though, there is never a medusa phase; surface; the surface with the mouth is called the • most cnidarians release eggs and sperm oral surface, and the opposite side is called the simultaneously into the water, so fertilization is aboral surface; external; • cnidarians have nerve cells and muscles, but • in many corals, ova and sperm are located in do not have organs such as brains, hearts, cir- the same polyp; fertilization takes place inside culatory or excretory systems; the gastrovascular cavity, and the larvae are • cnidarians have simple digestive systems with- ejected through the mouth; out an anus; the mouth is used for output as • a fertilized cnidarian egg develops into a free- well as input; swimming larva called a planula; • cnidarians have stinging cells called nema- • planula larvae are pear shaped and fringed tocysts (which are the primary distinguishing with cilia that give them limited