Palythoa toxica, also referred to by its Hawaiian common name, limu-make-o-Hana ('seaweed of death from Hana'), is a species of zoanthid native to Hawaii.

[5] The polyps are partially embedded in a cushiony mat of coenenchyme which grows across the rock surface, and which incorporates sand grains and fragments of debris.

Its habitat was a shallow pool about 10 in (25 cm) deep which was subject to inflows of fresh water during periods of heavy rainfall, so it would appear to be a euryhaline species.

[10] Other species of Palythoa have also been shown to contain the substance in varying amounts at different times and in different places, and some algae and certain crabs and fish have been found to contain it.

It has been suggested that the toxin is actually produced by a dinoflagellate, Ostreopsis spp., and incorporated into the zoanthid tissues, possibly through a symbiotic relationship similar to that of zooxanthellae in coral.