hexacorals

Hexacorallia, commonly known as stony corals or true corals, is a subclass of Anthozoa, a class of marine invertebrates belonging to the phylum Cnidaria. The name hexacorallia refers to their characteristic radial symmetry, with polyp tentacles typically arranged in multiples of six. These animals are typically found in marine environments, forming the foundational structure of coral reefs, which are diverse and biologically rich ecosystems.

Hexacorals are colonial or solitary polyps. The colonial forms secrete a hard, calcareous exoskeleton, or corallite, which accumulates over time to form the complex structures of coral reefs. Each polyp within a colony lives in its own corallite. Solitary hexacorals, such as sea anemones, do not form colonies and their skeletons are less substantial. Their tissues contain symbiotic algae called zooxanthellae, which provide them with nutrients through photosynthesis, and in turn, the coral provides the algae with a protected environment and compounds needed for photosynthesis. This symbiosis is crucial for the growth and survival of most reef-building corals.

The subclass includes a wide variety of species, such as reef-building corals, soft corals (though technically not all soft corals are hexacorals, some are in the subclass Octocorallia), sea anemones, and black corals. They are important for marine biodiversity and coastal protection. Many species face threats from climate change, pollution, and overfishing.