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 Gambierdiscus produces CTX precursors. The presence of Gambierdiscus 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 Gambierdiscus cells were conducted in this area during 2016 and 2017. Gambierdiscus cells were isolated and identified as G. australes, G. excentricus, G. caribaeus, and G. belizeanus by molecular analysis. In this study, G. belizeanus is reported for the first time in the Canary Islands. Gambierdiscus isolates were cultured, and the CTX-like toxicity of forty-one strains was evaluated with the neuroblastoma cell-based assay (neuro-2a CBA). G. excentricus exhibited the highest CTX-like toxicity (9.5-2566.7 fg CTX1B equiv. cell^-1) followed by G. australes (1.7-452.6.2 fg CTX1B equiv. cell^-1). By contrast, the toxicity of G. belizeanus was low (5.6 fg CTX1B equiv. cell^-1), and G. caribaeus did not exhibit CTX-like toxicity. In addition, for the G. belizeanus strain, the production of CTXs was evaluated with a colorimetric immunoassay and an electrochemical immunosensor resulting in G. belizeanus producing two types of CTX congeners (CTX1B and CTX3C series congeners) and can contribute to CP in the Canary Islands.

Keywords: Ciguatera; Gambierdiscus; ciguatoxins (CTXs); immunoassay; immunosensor; neuroblastoma cell-based assay.

Figure 1

Phylogenetic tree of the LSU D8-D10 region (rDNA) using Maximum Likelihood analysis. Sequences in bold represent the strains of this study. The number of clones (n) with the same haplotypes is shown in parentheses. Values at nodes represent bootstrap values (≥70) and the Bayesian posterior probability (≥0.95) (bt/pp).

Figure 2

SEM images of G. belizeanus (IRTA-SMM-17-421): apical (A), antapical (B), ventral (C) views, detail of Po plate and pores (D).

Figure 3

Distribution of each species in the stations of the Canary Islands during 2016–2017. Station numbers are represented in bold. The presence of Gambierdiscus species determined with molecular analysis is presented with a circle and includes the number strains identified for each species. The asterisk represents the presence of Gambierdiscus sp. Colors of circles are for G. australes (blue), G. excentricus (red), G. caribaeus (green), and G. belizeanus (yellow). EH (El Hierro), FV (Fuerteventura), GC (Gran Canaria), LG (La Gomera), LP (La Palma), LZ (Lanzarote), and TF (Tenerife).

Figure 4

Distribution of CTX-like toxicity of G. australes and G. excentricus according to island of origin. EH (El Hierro), FV (Fuerteventura), GC (Gran Canaria), LG (La Gomera), LP (La Palma), LZ (Lanzarote) and TF (Tenerife).

Figure 5

Sampling stations in the Canary Islands for the current study. Numbers correspond to locations described in Table 1. EH (El Hierro), FV (Fuerteventura), GC (Gran Canaria), LG (La Gomera), LP (La Palma), LZ (Lanzarote), and TF (Tenerife).

Figure 6

Structure of CTX1B and CTX3C congeners recognized by the antibodies used in this work.