Further Advance of Gambierdiscus Species in the Canary Islands, with the First Report of Gambierdiscus belizeanus

Abstract

Ciguatera Poisoning (CP) is a human food-borne poisoning that has been known since ancient times to be found mainly in tropical and subtropical areas, which occurs when fish or very rarely invertebrates contaminated with ciguatoxins (CTXs) are consumed. The genus of marine benthic dinoflagellates <i>Gambierdiscus</i> produces CTX precursors. The presence of <i>Gambierdiscus</i> species in a region is one indicator of CP risk. The Canary Islands (North Eastern Atlantic Ocean) is an area where CP cases have been reported since 2004. In the present study, samplings for <i>Gambierdiscus</i> cells were conducted in this area during 2016 and 2017. <i>Gambierdiscus</i> cells were isolated and identified as <i>G. australes</i>, <i>G. excentricus</i>, <i>G. caribaeus,</i> and <i>G. belizeanus</i> by molecular analysis. In this study, <i>G. belizeanus</i> is reported for the first time in the Canary Islands. <i>Gambierdiscus</i> isolates were cultured, and the CTX-like toxicity of forty-one strains was evaluated with the neuroblastoma cell-based assay (neuro-2a CBA). <i>G. excentricus</i> exhibited the highest CTX-like toxicity (9.5-2566.7 fg CTX1B equiv. cell^-1) followed by <i>G. australes</i> (1.7-452.6.2 fg CTX1B equiv. cell^-1). By contrast, the toxicity of <i>G. belizeanus</i> was low (5.6 fg CTX1B equiv. cell^-1), and <i>G. caribaeus</i> did not exhibit CTX-like toxicity. In addition, for the <i>G. belizeanus</i> strain, the production of CTXs was evaluated with a colorimetric immunoassay and an electrochemical immunosensor resulting in <i>G. belizeanus</i> producing two types of CTX congeners (CTX1B and CTX3C series congeners) and can contribute to CP in the Canary Islands.