Gambierdiscus and Fukuyoa as potential indicators of ciguatera risk in the Balearic Islands

Abstract

Gambierdiscus and Fukuyoa are genera of toxic dinoflagellates which were mainly considered as endemic to marine intertropical areas, and that are well known as producers of ciguatoxins (CTXs) and maitotoxins (MTXs). Ciguatera poisoning (CP) is a human poisoning occurring after the consumption of fish or more rarely, shellfish containing CTXs. The presence of these microalgae in a coastal area is an indication of potential risk of CP. This study assesses the risk of CP in the Balearic Islands (Western Mediterranean Sea) according to the distribution of both microalgae genera, and the presence of CTX-like and MTX-like toxicity in microalgal cultures as determined by neuro-2a cell based-assay (neuro-2a CBA). Genetic identification of forty-three cultured microalgal strains isolated from 2016 to 2019 revealed that all of them belong to the species G. australes and F. paulensis. Both species were widely distributed in Formentera, Majorca and Minorca. Additionally, all strains of G. australes and two of F. paulensis exhibited signals of CTX-like toxicity ranging respectively between 1 and 380 and 8-16 fg CTX1B equivalents (equiv.) • cell^-1. Four extracts of F. paulensis exhibited a novel toxicity response in neuro-2a cells consisting of the recovery of the cell viability in the presence of ouabain and veratridine. In addition, G. australes showed MTX-like toxicity while F. paulensis strains did not. Overall, the low CTX-like toxicities detected indicate that the potential risk of CP in the Balearic Islands is low, although, the presence of CTX-like and MTX-like toxicity in those strains reveal the necessity to monitor these genera in the Mediterranean Sea.

Keywords: Ciguatera; Ciguatoxins; Fukuyoa; Gambierdiscus; Maitotoxins; Neuro-2a cell-based assay.