FIGURE 29.10
Representatives of the cnidarians classes. (a) Polyps of a colonial species belonging to the class Hydrozoa. (b) jellyfish of the class Scyphozoa. The medusa is the conspicuous stage of the scyphozoan life cycle. The largest scyphozoan species have tentacles over 30 m long dangling from umbrellas 2 to 3 m in diameter. (c) Sea anemones and other members of the class Anthozoa exist only as polyps. (d) A colony of colony of coral polyps (class Anthozoa). Many corals harbor symbiotic algae that contribute to the food supply of the polyps. Coral reefs, which provide habitats for an enormous variety of invertebrates and fishes, are restricted to warm, shallow seas. This is a star coral.