Mention the important characteristics of coelenterate and give examples.
The important characteristics of coelenterates are: - (i) They are marine animals that may be solitary or colonial. (ii) The body consists of two germ layers, the ectoderm and endoderm (diploblastic). (iii) Their body is radially symmetrical. (iv) They are acoelomate animals i.e., lack true coelom. They exhibit a blind sac body plan. (v) They have a holozoic form of nutrition. (vi) The body encloses a large central cavity known as coelenteron, which has a single opening to the outside. Coelenterons is also known as a gastrovascular cavity. vii) They have either intracellular or extracellular modes of digestion. (viii) They commonly show polymorphism. There are two types of individuals: a polyp (asexual form) and a medusa (sexual form). (ix) They have tentacles, which are usually thread-like outgrowths. (x) Stinging cells or nematocysts are present. (xi) Their larvae are ciliated and free-swimming. (xii) Example: - Obelia, Aurelia, Hydra, Metridium etc.
