Phyllodiscus semoni Kwietniewski, 1897

Phyllodiscus semoni does not look like much during the day. However, it is a rather bizarre sea anemone that packs an extremely powerful and potentially dangerous sting. Dangerous Marine Animals by Bergbauer, Myers & Kirschner calls the "sting severe, followed by inflammation and long-term discoloration" and they note it has been reported to have caused a human death in the Philippines. A paper by Mizuno et al (2007) studying the venom of this anemone states that it targets the kidney and can cause severe renal injury. Yikes! Don't bump into them. Unfortunately, they are not easy to recognize. Retracted into a fuzzy mass of irregular tentacles, it looks like some sort of variably colored clump of algae. At night, alien-like, a disk of more typical anemone tentacles erupts from the top of the clump, and the stalk stretches upward with the cluster of tentacles at the top. It is no wonder Dangerous Marine Animals calls it the "Jack-in-the-box anemone." The anemones come in various colors, as seen in the photo links below. We have not seen, or perhaps should say, not recognized many specimens. We have perhaps eight recorded, but because of their cryptic appearance, they are probably a lot more common than this low number would indicate. Most were out on the oceanside reef, but at least two have been seen in the lagoon, one on the reef north of Bigej and another on the slope of the pinnacle at Victor buoy. Several of these we were able to see multiple times by returning to the same spots over a period of a year or so, but all eventually vanished, as though they do not live a very long time.


Each thumbnail links to a larger photo.

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Bergbauer, Matthias; Robert F. Myers & Manuela Kirschner. 2009. Dangerous Marine Animals. A&C Black Publishers Ltd. London. 384pp.

Mizuno, Masashi; Masatoshi Nozaki; Nobuya Morine; Norihiko Suzuki; Kazuhiro Nishikawa; B. Paul Morgan; & Seiichi Matsuo. 2007. A protein toxin from the sea anemone Phyllodiscus semoni targets the kidney and causes a severe renal injury with predominant glomerular endothelial damage. The American Journal of Pathology 171(2):402-414.