Palytoxin found in Palythoa sp. zoanthids (Anthozoa, Hexacorallia) sold in the home aquarium trade

Abstract

Zoanthids (Anthozoa, Hexacorallia) are colonial anemones that contain one of the deadliest toxins ever discovered, palytoxin (LD(50) in mice 300 ng/kg), but it is generally believed that highly toxic species are not sold in the home aquarium trade. We previously showed that an unintentionally introduced zoanthid in a home aquarium contained high concentrations of palytoxin and was likely responsible for a severe respiratory reaction when an individual attempted to eliminate the contaminant colonies using boiling water. To assess the availability and potential exposure of palytoxin to marine aquarium hobbyists, we analyzed zoanthid samples collected from local aquarium stores for palytoxin using liquid chromatography and high resolution mass spectrometry and attempted to identify the specimens through genetic analysis of 16S and cytochrome c oxidase 1 (COI) markers. We found four specimens of the same apparent species of zoanthid, that we described previously to be responsible for a severe respiratory reaction in a home aquarium, to be available in three aquarium stores in the Washington D.C. area. We found all of these specimens (n = 4) to be highly toxic with palytoxin or palytoxin-like compounds (range 0.5-3.5 mg crude toxin/g zoanthid). One of the most potent non-protein compounds ever discovered is present in dangerous quantities in a select species of zoanthid commonly sold in the home aquarium trade.

Figure 1. Zoanthid colony responsible for a severe respiratory reaction, collected from a home aquarium in 2008.

[Referred to as VAZOA in Figure 2A and Virginia zoanthid in text]. Sample was found to contain approx. 600 µg palytoxin/g wet zoanthid. Bar represents 1 cm.

Figure 2. Species identification of zoanthid samples collected from aquarium stores.

Maximum-likelihood (ML) phylogenies of zoanthids showing both the 16S [A] and COI [B] data sets. Support above branches: ML bootstraps/Neighbor-joining bootstraps/Bayesian posterior probabilities. [C-K] Representative specimens for Palythoa spp. (both toxic and non-toxic/weakly-toxic) and Zoanthus spp. (all non- or weakly-toxic) collected from local aquarium stores including: [C] sample 305.11.2, [D] sample 306.37.3, [E] sample 306.39.2, [F] samples 306.39.3 [open arrows] and sample 306.39.4 [closed arrows], [G] sample 305.13.1, [H] sample 306.39.1, [I] sample 305.11.6, [J] sample 305.11.5, and [K] sample 305.11.3. [Red Box] Visually and genetically consistent with Palythoa spp. and containing high concentrations of palytoxins (500–3500 µg/g wet zoanthid). [Green Box] Visually and genetically consistent with Palythoa spp. but non- or weakly-toxic, and [Blue Box] visually and genetically consistent with Zoanthus spp., and non- or weakly-toxic. For [C-K], bar represents 1 cm.

Figure 3. Toxin analysis of zoanthid samples collected from aquarium stores.

High resolution mass spectrometric (left column) and high performance liquid chromatographic (right column) analysis of [A] palytoxin standard, from P. tuberculosa, purchased from Wako Pure Chemicals, Tokyo, Japan, [B] sample 305.11.2 (Figure 2C), purchased from aquarium store #1, which contained approx. 500 µg palytoxin/g wet zoanthid and [C] sample 306.37.3 (Figure 2D), purchased from aquarium store #2, which contained approx. 3500 µg deoxy-palytoxin/g wet zoanthid. For all 3, the inset graph in the right column is the UV spectra for the HPLC peak at 12.4 minutes. All samples contained a 327 Da. fragment and UV maxima at 233 and 263 nm, which are characteristic of palytoxins.