cnidáriákra

Cnidaria is a phylum of aquatic animals that includes jellyfish, corals, sea anemones, and hydras. These animals are characterized by the presence of cnidocytes, which are specialized stinging cells used for capturing prey and defense. Cnidarians are radially symmetrical and have a simple body plan consisting of a sac-like structure with a single opening that serves as both mouth and anus. This opening leads to a gastrovascular cavity where digestion occurs. They exist in two primary forms: polyps, which are sessile and attached to a surface, and medusae, which are free-swimming and bell-shaped. Many cnidarians exhibit a life cycle that alternates between these two forms. They are found in marine and freshwater environments worldwide, playing important roles in their ecosystems as both predators and prey. Their diversity ranges from the microscopic to large, gelatinous forms.