Toxicity screening of 13 Gambierdiscus strains using neuro-2a and erythrocyte lysis bioassays

The genus Gambierdiscus is constituted by benthic dinoflagellates that produce ciguatoxins (CTXs) and maitotoxins (MTXs), which are among the most potent marine toxins known to date. CTXs are bio-accumulated and biotransformed along the marine food chain and are involved in Ciguatera Fish Poisoning (CFP). An increasing number of species has recently been discovered in this genus and CFP has recently been reported from areas previously not considered endemic, namely the Canary Islands. Little is known about how toxicity varies among species and isolates of Gambierdiscus. This study examined the toxicity of 13 strains of Gambierdiscus, seven from the Pacific Ocean (G. pacificus CCMP1650, G. sp. VGO917, G. australes CCMP1653, G. scabrosus KW070922_1, G. sp. Vietnam, G. caribaeus BILL HI Gam8, G. carpenteri PAT HI Jar7 Gam11), one from the Mediterranean Sea (G. carolinianus GreeceGam2), and five from the North-Eastern Atlantic Ocean (G. australes VGO1178, G. australes VGO1181, G. silvae VGO1167, G. silvae VGO1180, G. excentricus VGO791). Algal cells were extracted with methanol and extracts were partitioned between dichloromethane (DCM) and aqueous methanol (aq.MeOH). The toxicity has been evaluated on the pre-purified extracts using an ouabain/veratridine (O/V) neuro-2a (N2a) assay and a human erythrocyte lysis assay (ELA). In general terms, all strains showed hemolytic activity in the aq.MeOH fraction in the range of pg MTXeq/cell, and N2a cytotoxicity in the DCM fraction in the range of fg P-CTX-3C eq/cell. G. excentricus (Canary Islands) was an exception, with N2a cytotoxicity in the range of pg P-CTX-3C eq/cell, in accordance with data previously reported by Fraga et al. (2011).