Recently, Jonathan Deeds and his collaborators published a very interesting study about one of our favourite animals in the open access journal ‘Plos One’. They reported the case of a zoanthid colony from a home aquarium which was responsible for a severe respiratory reaction due to palytoxin when a hobbyist attempted to eliminate the colonies using boiling water. Sample from the home tank was found to contain approx. 600 mg of palytoxin per g of wet zoanthid, which is enough to kill several thousands of mice!
Some of the deadliest toxins known to man such as palytoxin or maitotoxin come from the sea and are often produced by tropical marine dinoflagellates. However, these toxins can also be found in many more species due to accumulation through trophic chain or symbiosis relationships, such as in fishes, crustaceans or zoanthid corals. This is the reason why palytoxins are one of the few marine compounds that pose a risk to humans through ingestion (consumption of contaminated seafood), inhalation (exposure to palytoxin containing aerosols), and dermal (exposure to select marine zoanthids) routes of exposure.
Thus, to assess the availability and potential exposure of palytoxin to marine aquarium hobbyists, Deeds and coll. analyzed zoanthid samples collected from local aquarium stores for palytoxin using liquid chromatography and high resolution mass spectrometry. In addition, because zoanthids are proved difficult to identify to the species level on the basis of their appearance, specimens were also identified through genetic analysis of 16S and cytochrome c oxidase genes.
During this investigation, it was shown that many of the zoanthids commonly sold in the home aquarium trade are non-toxic or weakly-toxic, but a highly toxic variety of Palythoais indeed available. The authors found four specimens of the same apparent species which was responsible for a severe respiratory reaction in a home aquarium available in three aquarium stores. The most closely related species to the toxic specimens based on DNA analysis were Palythoa heliodiscus, showing that the most potent non-protein compounds ever discovered is present in dangerous quantities in a species of zoanthid commonly sold in the home aquarium trade.
Numerous poisonous and venomous animals are traditionally available at your local pet store for instance the lionfish (family Scorpaenidae), puffer fish (family Tetraodontidae), sea urchin (Astropyga spp.)and the blue ringed octopus (Hapalochlaena spp.). However, well documented cases of human poisonings due to exposure to zoanthids in home aquaria are limited, leaving hobbyists often unaware of the deadly poisons they are being exposed to. We therefore encourage everybody to take all necessary precautions when handling zoanthids.
Representative specimens for Palythoa spp. (both toxic and non-toxic/weakly-toxic) and Zoanthus spp. (all non- or weakly-toxic) collected from aquarium stores. [Red Box] Visually and genetically consistent with Palythoa heliodiscus and containing high concentrations of palytoxins. [Green Box] Visually and genetically consistent with Palythoa mutuki and Palythoa tuberculosa but non- or weakly-toxic. [Blue Box] visually and genetically consistent with Zoanthus sansibaricus, close to Zoanthus sociatus, and non- or weakly-toxic. Bar represents 1 cm.