Stelloides Sea Anemone, Isoaulactinia stelloides

Stelloides Sea Anemone, Isoaulactinia stelloides. Underwater photograph taken in coastal waters off Cozumel Island, Quintana Roo, March 2021. Photograph and identification courtesy of Marina Sutormina, Stockholm, Sweden.

Phylogeny:   The Stelloides Sea Anemone,  Isoaulactinia stelloides (McMurrich, 1889), is a member of the Actiniidae Family of True Sea Anemones. The Genus Isoaulactinia is one of fifty-seven genera in that family, and there are two species in this genus. There is no widely accepted common name for this species.

Morphology:  The Stelloides Sea Anemone has a stout column that can measure 2.25 cm (0.8 inch) in height and 1.5 cm (0.6 inches) in diameter. The oral disk is wider than the column, up to 3.8 cm (1.5 inches) in diameter. The oral disk is rimmed with 48 – 96 tentacles. The column and disk are tan to light brown or light olive in color. There are white to cream colored lines radiating from the mouth and banding the tentacles. The column is often buried in sand though the pedal based is attached to rocky substrate.

Habitat and Distribution: The Stelloides Sea Anemone are found on rocks, jetties, other hard substrates, and coral rubble. They live in the lower portions of the intertidal zone and at  depths up to 6 m (20 feet). The Stelloides Sea Anemone are a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico and the east coast of the Yucatán Peninsula in the Caribbean.

Diet:  The Stelloides Sea Anemone  are nocturnal predators. They feed on small fish,  invertebrates, and larger zooplankton, which they capture with their tentacles. Warty Sea Anemones are also zooxanthellate, meaning that they have a symbiotic relationship with single-cell dinoflagellates, known as zooxanthellae. Zooxanthellae live within certain Coral Polyps, Sea Anemones, Jellyfish, and Nudibranchs. The zooxanthellae produce energy, during daylight, by means of photosynthesis. This energy is passed along to their hosts.

Predators:  The Stelloides Sea Anemone have stinging tentacles that provide defense from some predators. Even with this defense mechanism they are eaten by fish, starfish, gastropods, and Loggerhead Sea Turtles.

Reproduction: The Stelloides Sea Anemone are simultaneous hermaphrodites (having both male and female sex organs). Brooding takes place internally. The zygote (fertilized egg) develops into a planktonic larva. The larva metamorphizes, forming tentacles, pharynx, and septa, and settles to the bottom to begin benthic life. This species is not known to reproduce asexually as many sea anemones do.

Ecosystem Interactions:   As zooxanthellate organisms the Stelloides Sea Anemone have a symbiotic relationship with zooxanthellae dinoflagellates. These zooxanthellae provide energy for the anemones and the anemone provides nutrients, carbon dioxide, and a secure, sunlit, platform for the zooxanthellae. These anemones do not form relationships with fish, such as Clownfish or Anemonefish, as other Anemones do in the Indo-Pacific.

Human Interactions: The Stelloides Sea Anemone have no direct impact on human activities. They are not targeted by fisheries or the aquarium trade. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Aulactinia stelloides, Bunodactis stelloides, and Bunodella stelloides.