An Update on Ciguatoxins and CTX-like Toxicity in Fish from Different Trophic Levels of the Selvagens Islands (NE Atlantic, Madeira, Portugal)

Abstract

The Selvagens Islands, which are a marine protected area located at the southernmost point of the Portuguese maritime zone, have been associated with fish harboring ciguatoxins (CTX) and linked to ciguatera fish poisonings. This study reports the results of a field sampling campaign carried out in September 2018 in these remote and rarely surveyed islands. Fifty-six fish specimens from different trophic levels were caught for CTX-like toxicity determination by cell-based assay (CBA) and toxin content analysis by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Notably, high toxicity levels were found in fish with an intermediate position in the food web, such as zebra seabream (Diplodus cervinus) and barred hogfish (Bodianus scrofa), reaching levels up to 0.75 µg CTX1B equivalent kg−1. The LC-MS/MS analysis confirmed that C-CTX1 was the main toxin, but discrepancies between CBA and LC-MS/MS in D. cervinus and top predator species, such as the yellowmouth barracuda (Sphyraena viridis) and amberjacks (Seriola spp.), suggest the presence of fish metabolic products, which need to be further elucidated. This study confirms that fish from coastal food webs of the Selvagens Islands represent a high risk of ciguatera, raising important issues for fisheries and environmental management of the Selvagens Islands.

Ciguatoxin Detection in Flesh and Liver of Relevant Fish Species from the Canary Islands

“…The lack of CP outbreaks due to the intake of this fish species could be explained by the low toxicity found in flesh (with a maximum of 0.051 ng CTX1B Eq•(g flesh) −1 ) and the usual low dietary exposure of consumers to this fish species. These values are quite different from those obtained by Costa et al, [59] in a zebra seabream (Diplodus cervines) captured in the Selvagens Islands (Portugal). In this individual, the toxicity determined by CBA was 0.37 µg CTX1B Eq•(kg flesh) −1 , and the presence of C-CTX1 was not found.…”

Deep-Water Fish Are Potential Vectors of Ciguatera Poisoning in the Gambier Islands, French Polynesia

“…Of note, such discrepancies were also observed between CBA-N2a and LC-MS/MS data in fish from the Selvagens Islands, suggesting the presence of metabolic products, which need to be further elucidated, as well [69]. In this region, C-CTX1 was the most frequently encountered Caribbean CTX analog, although the toxin profile of the zebra bream Diplodus cervinus was free of it [69]. Similarly, our results show that CTX1B was not the main contributor to the toxicity of the E. illustris specimen from the Gambier Islands.…”

“…Overall, the nontoxic (one specimen and one pooled sample) and toxic (three specimens) statuses were confirmed by LC-MS/MS for 6/10 samples showing a 60% agreement between the three biological and the chemical methods. Of note, such discrepancies were also observed between CBA-N2a and LC-MS/MS data in fish from the Selvagens Islands, suggesting the presence of metabolic products, which need to be further elucidated, as well [69]. In this region, C-CTX1 was the most frequently encountered Caribbean CTX analog, although the toxin profile of the zebra bream Diplodus cervinus was free of it [69].…”

Current Trends and New Challenges in Marine Phycotoxins

“…This same case occurs for ciguatoxins, which, in addition to the lack of certified standards, are not yet regulated in Europe in spite of the fact that the dinoflagellates producers of ciguatoxins are found in our coasts today: the presence of CTXs was confirmed in locally sourced fish in Canary Islands or Madeira [ 57 ]. As we and others have demonstrated, ciguatoxins elicited negative shifts in the active potential of voltage gated sodium channels [ 58 , 59 ].…”