Actiniidae Family of True Sea Anemones

Five True Sea Anemones of the Actiniidae Family can be found in this website:

Phylogeny: The True Sea Anemones of the Actiniidae Family, like Jellyfish, and Hydroids,  belong to the phylum Cnidaria. They are in the class Hexacorallia and the order Actiniaria. The Actiniidae Family is the largest family of sea anemones with fifty-five genera and three hundred and forty species. Species in the Actiniidae Family are also commonly known as Actiniids.

Morphology:  Members the Actiniidae Family have radial symmetry, a hollow digestive cavity, and specialized stinging cells within the tentacles that surround their mouth. Their polyps have a flower-like appearance. These solitary hexacorals lack a calcareous skeleton. Their column has a base that is either rounded, or forms an adherent disc and may be smooth or covered with verrucae (warts). These verrucae may be adhesive, often with gravel attached, or non-adhesive. Adults have at least 36 tentacles. There may be one, or more than one, tentacle between mesenteries (sheets of tissue that divide the internal body cavity).  Anemones in this order are often brightly colored. True Sea Anemones reach a maximum of  36 cm (14 inches) in diameter.

Habitat and Distribution: Sea anemones of the Actiniidae Family are generally found attached to hard substrate, though their attachment is not permanent or fixed in one location. They can crawl slowly, while remaining attached. Also, many species can detach from the substrate and drift or roll, to escape predation. They range in depth from the intertidal zone to depths exceeding 1,000 m (3,280 feet). Actiniids are found worldwide, in tropical and temperate waters. Eighteen species from the Actiniidae Family are found in Mexican waters.

Reproduction:  True Sea Anemones may be gonochoric, sequential hermaphrodites, or simultaneous hermaphrodites. They generally reproduce sexually through broadcast spawning, with external fertilization, though some species brood their eggs internally. They can also reproduce asexually, by budding or fission.

Ecosystem Role: True Sea Anemones are predators, using their stinging tentacles to capture crabs, fish, mollusks, sea cucumbers, and other invertebrates. The stinging cells paralyze the prey and the tentacles then pass the prey to the mouth. The stinging tentacles provide defense from some predators, and the anemone can roll its tentacles and disk inward forming an awkward shape that is difficult for predators to attack. Even with these defense mechanisms, sea anemones in the Actiniidae family are preyed upon fish, gastropods, nudibranchs, sea turtles and starfish. This species has a symbiotic relationship with single-cell dinoflagellates, generally referred to as zooxanthellae. With very few exceptions, True Sea Anemones do not form relationships with fish, such as Clownfish or Anemonefish, as other anemones do in the Indo-Pacific.