Coelenterates include jellyfishes, sea anemones, corals, and hydra. They are among the most ancient multicellular organisms, appearing in Late Precambrian time. All coelenterates are aquatic, mostly marine. Coelenterates are animals that have very simple tissue organization, with only two layers of cells, external and internal. They are characterized by a single hollow internal cavity serving for digestion, excretion, and other functions and having tentacles on the oral end. radially symmetrical body arrangement. Coelenterates have a network of nerves is spread throughout the body. Many forms exhibit polymorphism, where individuals with different body arrangements are present in a colony for different functions. Coelenterates generally reproduce asexually by budding, though sexual reproduction does occur in some groups.
|Examples of Coelenterates|
|Figure 15.9. Anemone||Figure 15.10. Anemone||Figure 15.11. Coral polyps||Figure 15.12. Pink soft coral|
|Figure 15.13. Jellyfish||Figure 15.14. Jellyfish||Figure 15.15. Moon jellyfish||Figure 15.16. Elkhorn coral|