zoanthid

Zoanthid is a common name for colonial anthozoan cnidarians belonging to the order Zoantharia. These marine invertebrates are found in shallow, tropical, and subtropical waters around the world. Zoanthids typically form dense colonies, often encrusting rocks, corals, or other substrates. Individual zoanthids, known as polyps, are small and can range in size from a few millimeters to several centimeters in diameter. They are characterized by their soft, fleshy bodies and a ring of tentacles surrounding a central mouth. The tentacles are used for capturing small prey, such as plankton.

The coloration of zoanthids can be highly variable, with many species displaying vibrant shades of green, brown, blue, yellow, and orange. This coloration is often due to symbiotic algae called zooxanthellae living within their tissues, which provide energy through photosynthesis. Zoanthids reproduce both sexually, releasing sperm and eggs into the water column, and asexually through budding and fragmentation within the colony. Their classification is complex, and many species are still undergoing revision. In the aquarium hobby, zoanthids are popular for their beauty and relative hardiness, though some species can be toxic and require careful handling. They are an important part of reef ecosystems, providing habitat and food for other marine organisms.