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 Gambierdiscus. Here, we describe the identity and toxicology of Gambierdiscus spp. isolated from the tropical and temperate waters of eastern Australia. Based on newly cultured strains, we found that four Gambierdiscus species were present at the tropical location, including G. carpenteri, G. lapillus and two others which were not genetically identical to other currently described species within the genus, and may represent new species. Only G. carpenteri 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 G. carpenteri. Using the Ca2+ influx SH-SY5Y cell Fluorescent Imaging Plate Reader (FLIPR) bioassay we found CTX-like activity in extracts of the unidentified Gambierdiscus strains and trace level activity in strains of G. lapillus. While no detectable CTX-like activity was observed in tropical or temperate strains of G. carpenteri, all species showed strong maitotoxin-like activity. This study, which represents the most comprehensive analyses of the toxicology of Gambierdiscus strains isolated from Australia to date, suggests that CFP in this region may be caused by currently undescribed ciguatoxins and maitotoxins.

Development of a quantitative PCR assay for the detection and enumeration of a potentially ciguatoxin-producing dinoflagellate, Gambierdiscus lapillus (Gonyaulacales, Dinophyceae)

“…The assay was shown to be highly sensitive and accurately detected 0.05 to over 4000 cells for G. lapillus. Although the toxin profile of G. lapillus has not been completely defined, it may produce uncharacterised CTXs congeners [19,48] and therefore is a part of the ciguateric web in Australia. The assay was applied to spatial replicates from 25 sites around Heron Island on the GBR, which found that G. lapillus was commonly present, but had a patchy spatial distribution and abundance.…”

“…More importantly, this assay does not require the operator to rely on melt curves to identify species, or to have access to G. lapillus DNA extracts as a positive control. Due to the potential CTX production of G. lapillus [19,48] the presence and distribution of this species is of interest in Australia where the causative organism(s) for CFP is yet to be established.…”

“…However, due to the complicated presentation of symptoms, the reporting rate is less than 20% [44]. Annually, there have been 7-69 reported cases between 2011 and 2015 (considering the report rate, > 35-345 cases, see [48]. Over 50% of Australia's vast coastline (total 66,000 km) is tropical or subtropical, and may be considered potential habitat for Gambierdiscus spp.…”

“…lapillus [19,48], G. toxicus [52] and two potentially new species [48 ], as well as F. yasumotoi [49]. Using high throughput amplicon sequencing, Gambierdiscus was identified to the genus level in Broome,…”

Ciguatera Fish Poisoning: The Risk from an Aotearoa/New Zealand Perspective

“…Over the last decade these species have been reported not only from tropical and subtropical waters, but also from more temperate regions, including the coastal waters of New South Wales, Australia [20,[25][26][27][28], and additional species have been reported from more sites throughout the Pacific region ( Figure 1) [6,13,23]. Of the eighteen described Gambierdiscus species, only G. silvae and G. carolinianus have not been reported in the Pacific region.…”