Toxicology of Gambierdiscus spp. (Dinophyceae) from Tropical and Temperate Australian Waters

Abstract

Ciguatera Fish Poisoning (CFP) is a human illness caused by the consumption of marine fish contaminated with ciguatoxins (CTX) and possibly maitotoxins (MTX), produced by species from the benthic dinoflagellate genus <i>Gambierdiscus</i>. Here, we describe the identity and toxicology of <i>Gambierdiscus</i> spp. isolated from the tropical and temperate waters of eastern Australia. Based on newly cultured strains, we found that four <i>Gambierdiscus</i> species were present at the tropical location, including <i>G. carpenteri</i>, <i>G. lapillus</i> and two others which were not genetically identical to other currently described species within the genus, and may represent new species. Only <i>G. carpenteri</i> was identified from the temperate location. Using LC-MS/MS analysis we did not find any characterized microalgal CTXs (P-CTX-3B, P-CTX-3C, P-CTX-4A and P-CTX-4B) or MTX-1; however, putative maitotoxin-3 (MTX-3) was detected in all species except for the temperate population of <i>G. carpenteri.</i> Using the Ca²⁺ influx SH-SY5Y cell Fluorescent Imaging Plate Reader (FLIPR) bioassay we found CTX-like activity in extracts of the unidentified <i>Gambierdiscus</i> strains and trace level activity in strains of <i>G. lapillus.</i> While no detectable CTX-like activity was observed in tropical or temperate strains of <i>G. carpenteri</i>, all species showed strong maitotoxin-like activity. This study, which represents the most comprehensive analyses of the toxicology of <i>Gambierdiscus</i> strains isolated from Australia to date, suggests that CFP in this region may be caused by currently undescribed ciguatoxins and maitotoxins.