coelenterate

Coelenterates are a phylum of marine animals that includes jellyfish, corals, and hydroids. They are characterized by their simple, radial symmetry and lack of a distinct head or brain. Coelenterates are sessile or free-swimming, and their bodies are composed of two primary layers: the outer epidermis and the inner gastrodermis. Between these layers lies the mesoglea, a gelatinous matrix that provides structural support.

The phylum Coelenterata is divided into two main classes: Hydrozoa and Scyphozoa. Hydrozoa includes hydroids, which are colonial or solitary, and siphonophores, which are colonial and often form complex structures. Scyphozoa includes true jellyfish, which are free-swimming and have a bell-shaped body with tentacles surrounding an oral opening.

Coelenterates reproduce both sexually and asexually. Sexual reproduction involves the release of gametes, which are fertilized to form a planula larva. Asexual reproduction can occur through budding or fragmentation. Coelenterates play important roles in marine ecosystems, serving as prey for many animals and contributing to the structure of coral reefs.