Triactis producta (Klunzinger, 1877)
Common throughout the Solitary Islands Marine Park. Distributed throughout the tropical Indo-Pacific region, from the Red Sea and East Africa to French Polynesia and Hawaii.
Habitat includes coral and rocky reef. Often in dense aggregations, sometimes attached to scleractinian corals. Intertidal to subtidal depths, specimens in photograph at 15 m depth.
Individuals of Triactis producta are zooxanthellate, the zooxanthellae continuing to photosynthesize while inside the sea anemone; the sea anemone can then use the sugars as food. Therefore the more zooxanthellae the sea anemone houses and can expose to sunlight, the more sugars the sea anemones can obtain, so the posture of Triactis producta differs depending on the presence of light. When there is light, the pseudotentacles are expanded, therefore exposing the zooxanthellae to the light to photosynthesize while the true tentacles are retracted. Associated with the pseudotentacles are swollen velicles (appear as hemispherical bumps) which are dense with nematocysts. In this photograph the true tentacles in the centre anemone are expanded allowing the sea anemone to actively feed. Crabs of the genus Lybia (also called boxer crabs) establish a mutualistic association with small sea anemones and this species is one previously reported in this association. The specimens in the photograph are approximately 25 - 30 mm across.
Fautin, D. G., Wallace, C. C. and Crowther, A. L. (2008) Revision of the sea anemone fauna of Moreton Bay, S.E. Queensland. Memoirs of the Queensland Museum 54: 35-64. p. 51.
Atlas of Living Australia website at https://bie.ala.org.au/search?q=triactis+producta. Accessed 27/06/2019.
Florida Museum website at https://www.floridamuseum.ufl.edu/science/triactis-producta-sea-anemone/. Accessed 27/06/2019.