Sea anemonesActiniaria

Sea anemones are predatory marine invertebrates. Each consists of a soft, columnar body, typically anchored by an adhesive base to hard surfaces like rock or coral, or sometimes burrowed into sand. An oral disc, located at the top of the column, bears a ring of tentacles surrounding a central mouth. These tentacles are armed with stinging cnidocytes, used for defence and prey capture. Anemones vary widely in size, with oral discs ranging from a few centimetres (inches) in diameter to over 50 cm (20 in) in large species. Colours are diverse, commonly including browns, greens, or whites, often with bright tips on the tentacles.

They inhabit environments from shallow reef flats down to depths of 40 metres (130 ft). Their diet primarily consists of zooplankton, small crustaceans, and fish, which they ambush with their stinging tentacles. While most species are sessile, remaining in one spot, some possess the ability to detach and slowly relocate across the seafloor. Many anemone species host symbiotic algae, known as zooxanthellae, within their tissues, which provide additional nutrition. Some also form symbiotic relationships with other animals, notably providing shelter for clownfish or hermit crabs.