Toxicity Characterisation of Gambierdiscus Species from the Canary Islands.

Araceli E Rossignoli,Pilar Riobó,Isabel Bravo,Angels Tudó,Jorge Diogène,Patricio A Díaz

doi:10.3390/toxins12020134

Abstract

In the last decade, several outbreaks of ciguatera fish poisoning (CFP) have been reported in the Canary Islands (central northeast Atlantic Ocean), confirming ciguatera as an emerging alimentary risk in this region. Five Gambierdiscus species, G. australes, G. excentricus, G. silvae, G. carolinianus and G. caribaeus, have been detected in macrophytes from this area and are known to produce the ciguatoxins (CTXs) that cause CFP. A characterization of the toxicity of these species is the first step in identifying locations in the Canary Islands at risk of CFP. Therefore, in this study the toxicity of 63 strains of these five Gambierdiscus species were analysed using the erythrocyte lysis assay to evaluate their maitotoxin (MTX) content. In addition, 20 of the strains were also analysed in a neuroblastoma Neuro-2a (N2a) cytotoxicity assay to determine their CTX-like toxicity. The results allowed the different species to be grouped according to their ratios of CTX-like and MTX-like toxicity. MTX-like toxicity was especially high in G. excentricus and G. australes but much lower in the other species and lowest in G. silvae. CTX-like toxicity was highest in G. excentricus, which produced the toxin in amounts ranging between 128.2 ± 25.68 and 510.6 ± 134.2 fg CTX1B equivalents (eq) cell−1 (mean ± SD). In the other species, CTX concentrations were as follows: G. carolinianus (100.84 ± 18.05 fg CTX1B eq cell−1), G. australes (31.1 ± 0.56 to 107.16 ± 21.88 fg CTX1B eq cell−1), G. silvae (12.19 ± 0.62 to 76.79 ± 4.97 fg CTX1B eq cell−1) and G. caribaeus (<LOD to 90.37 ± 15.89 fg CTX1B eq cell−1). Unlike the similar CTX-like toxicity of G. australes and G. silvae strains from different locations, G. excentricus and G. caribaeus differed considerably according to the origin of the strain. These differences emphasise the importance of species identification to assess the regional risk of CFP.

Highlights

Gambierdiscus is a genus of marine benthic dinoflagellates that produces maitotoxins (MTXs) and ciguatoxins (CTXs) [1,2,3]
CTXlike toxicity was attributed to microalgal extracts when the addition of a sample extract to neuroblastoma cells exposed to O/V+ treatment resulted in 20–80% viability decrease
The addition of the same extract to neuroblastoma cells exposed to O/V− treatment did not affect the cell viability (>80% viability)

Summary

Introduction

Gambierdiscus is a genus of marine benthic dinoflagellates that produces maitotoxins (MTXs) and ciguatoxins (CTXs) [1,2,3]. These cyclic polyether neurotoxins are among the five most potent natural toxins isolated to date [4]. Because they accumulate in coral reef fish, they can be transferred through the marine food web [5,6,7,8]. CTXs are the main toxins responsible for ciguatera fish poisoning (CFP) [9], a clinical syndrome caused by eating CTX-contaminated fish. CFP is widespread in tropical and sub-tropical marine areas, including the Caribbean Sea, Indian Ocean, Polynesia and other areas of the Pacific Ocean [11]

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Discussion

Conclusion