Abstract
The invasion of the tetrodotoxin (TTX)-bearing silver-cheeked toadfish and potential poisoning due to its consumption (tetrodotoxication) threatens public safety in the Mediterranean Sea. In this study, TTX and TTX analogues of Lagocephalus sceleratus (Gmelin, 1789) were measured using liquid chromatography tandem mass spectrometry (LC-MS/MS) in fish collected off the island of Crete (Southern Mediterranean). We tested the synergistic effect of a suite of factors potentially affecting toxins’ levels and tetrodotoxication risk using general and generalized linear models, respectively. The type of tissue, geographic origin (Cretan Sea, Libyan Sea), sex, and fish maturity stage were significant predictors of toxin concentrations. Mean TTX was higher in gonads and lower in muscles, higher in the Libyan Sea and in female fish, and lower in juvenile (virgin) fish. The concentration of TTX was also significantly and positively correlated with the concentration of several TTX analogues (4-epiTTX, 4,9-anhydroTTX, 11-deoxyTTX, 5,11/6,11-dideoxyTTX, 5,6,11-trideoxyTTX, 11-norTTX-6-ol). The analysis showed that fish originating from the Libyan Sea had significantly higher probability to cause tetrodotoxication in case of consumption. The variability explained by the models developed in this study was relatively low, indicating that toxin levels are hard to predict and the consumption of L. sceleratus should therefore be avoided.
Highlights
Tetrodotoxin (TTX) is a potent, non-protein, water-soluble, and heat-stable neurotoxin [1]that acts as a blocker in voltage-gated sodium channels, inhibiting nerve and muscle conduction [2]
Many studies conducted in the Mediterranean Sea have detected/quantified TTX levels in L. sceleratus tissues by using various analytical instruments and methods. Those based on liquid chromatography and mass spectrometry are the most common, as LC-MS is recognized as the state of the art in the analysis of TTX and its analogues
This study showed that the type of tissue, geographic area, sex, and maturity stage are significant sources of variation in TTX and TTX analogues’ concentrations
Summary
That acts as a blocker in voltage-gated sodium channels, inhibiting nerve and muscle conduction [2]. It is present in a variety of aquatic and terrestrial organisms with pufferfishes (family: Tetraodontidae) being the most widely known TTX bearers [3]. TTX has been found to coexist with 26 TTX analogues, many of which have been detected in pufferfishes [15] These can be grouped into the following: (1) chemical equilibrium analogues (4-epiTTX and 4,9-anhydroTTX), (2) deoxy analogues (5-deoxyTTX, 11-deoxyTTX, 5,11-dideoxyTTX, 6,11-dideoxyTTX, and 5,6,11-trideoxyTTX), (3) 11-CH2OHoxidized analogues (11-oxoTTX), and (4) C11-lacking analogues (11-norTTX-6(S)-ol and 11-norTTX-6(R)-ol) [16]. The detection and quantification of TTX and its analogues have been conducted using liquid chromatography tandem mass spectrometry (LC-MS/MS) [18], which has progressively replaced the mouse bioassay method (MBA) [19], as a more accurate and ethical alternative for toxicity assessments [20]
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