Sea anemones

Actiniaria

undefined are predatory marine invertebrates belonging to the order Actiniaria. They are named after the terrestrial flowering plant Anemone due to their colorful appearance. undefined are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. They are related to corals, jellyfish, tube-dwelling anemones, and Hydra. Unlike jellyfish, sea anemones do not have a medusa stage in their life cycle.

A typical sea anemone is a single polyp attached to a hard surface by its base. They can also be found in soft sediment or floating near the water's surface. The polyp has a columnar trunk topped by an oral disc with a ring of tentacles and a central mouth. The tentacles can be retracted or expanded to catch prey, and they are armed with stinging cells called cnidocytes. Many sea anemones have a symbiotic relationship with single-celled dinoflagellates or green algae that provide additional nourishment. Some species live in association with clownfish, hermit crabs, or other animals.

undefined reproduce by liberating sperm and eggs into the water. The fertilized eggs develop into planula larvae, which eventually settle on the seabed and transform into juvenile polyps. They can also reproduce asexually by fragmentation or budding. undefined are sometimes kept in reef aquariums, but the global trade in marine ornamentals poses a threat to their populations.

undefined have a unique anatomy, with a column and tentacles that can change shape and lengthen. They possess a primitive nervous system and specialized cells for defense and prey capture. undefined are primarily predators, capturing prey with their tentacles and immobilizing it with stinging cells. Some species are parasitic, while others form mutualistic relationships with algae or other organisms.

undefined inhabit both deep oceans and shallow coastal waters worldwide. They can be found attached to rocks, shells, or submerged timber, as well as burrowing into sand and mud. While the majority of species are found in tropical areas, there are also adaptations to cold waters.