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The emerging threat of ciguatera poisoning (CP) in Europe has been associated with fish captured in the Canary Islands (Spain) and Selvagens Islands (Portugal). The first are heavily populated islands where numerous scientific studies have been carried out. Conversely, the Selvagens Islands as a nature reserve with low human pressure have been rarely surveyed in terms of the marine benthic microalgae, including the epiphytic ciguatera-causing dinoflagellate species. To investigate the harmful microalgal diversity of the Selvagens Islands, a scientific cruise to these remote islands took place in September, 2018. The Gambierdiscus species composition and distribution, and the associated epiphytic dinoflagellate community, were assessed using artificial substrate devices. Gambierdiscus cells were found in all samples, reaching concentrations of up to 725 cells 100 cm–2. G. australes was the only species identified after morphological and molecular analysis of the retrieved cultures. Species identification was confirmed by molecular characterization based on the LSU D8–D10 region. Nevertheless, phylogenetic studies indicated that some strains diverged from the G. australes clade suggesting genetic differentiation. Toxicity was estimated by neuro-2a cell-based assay in four strains, ranging from 2.46–83 fg of CTX1B eq. cell–1. The epiphytic dinoflagellate community that co-occurred with Gambierdiscus comprised other toxic or potentially toxic dinoflagellates, such as Ostreopsis, Prorocentrum, Amphidinium and Coolia species. Oceanographic and meteorological data were also obtained to characterize the occurrence of Gambierdiscus. This study is the first stage in understanding the role of the Selvagens Islands in the incubation and proliferation of the ciguatera-causing dinoflagellates Gambierdiscus in the NE Atlantic. The Selvagens Islands are a ciguatera hotspot in Europe. Gambierdiscus australes was the only species observed in the Selvagens Islands. Strains diverging from the G. australes clade suggest genetic differentiation. [ABSTRACT FROM AUTHOR]

Tetrodotoxin (TTX) is a potent neurotoxin responsible for a human intoxication event in Spain associated with the consumption of trumpet shell Charonia lampas. In Europe, TTX is not regulated or monitored, and there is little knowledge about its presence in seafood. Here, we investigated the tissue distribution of TTX and analogues in three specimens of trumpet shell C. lampas bought in a market in southern Portugal. Toxin concentration was above the EFSA recommended limit in the non-edible tissues of all specimens and within the limit in the edible tissues of two specimens. 4,9-AnhydroTTX and 13 additional TTX analogues were detected in tissues, the most abundant being anhydrotrideoxyTTX and trideoxyTTX. These results suggest that although thorough evisceration may lower the amount of TTX consumed, it may not be sufficient to ensure consumer safety. Regular monitoring of TTX and analogues in trumpet shell and other edible gastropods is therefore recommended to avoid poisoning incidents. [ABSTRACT FROM AUTHOR]

Fish are frequently exposed to paralytic shellfish toxins ( PSTs) derived from harmful algal blooms ( HAB). PSTs are potent neurotoxins with strong effects on fish at multiple trophic levels. Here, we examine the historical and contemporary mass mortality events combining with the available data on response of fish to PSTs' exposure. The data show that fish are negatively affected by these natural toxins on a recurring basis. Transient effects of PSTs have also been observed in fish and although difficult to quantify, these sublethal effects can affect foraging and predation avoidance. Additionally, the spatiotemporal overlapping of fish spawning and HAB can also be critical for fish survival and fisheries recruitment. Exposure of fish in their early life stages to dissolved toxins in the water column has also been identified as a risk factor for fish survival. In the context of global climate change, where PSTs are likely to become increasingly important, new insights and a synthesis of up-to-date information on fish response to PSTs and the risk associated with toxic dinoflagellate blooms are presented. [ABSTRACT FROM AUTHOR]