Tetrodotoxins in the horseshoe crab <i>Carcinoscopius rotundicauda</i> pose a threat to seafood safety in Vietnam

Abstract Tetrodotoxin (TTX) and two of its derivatives were detected in two horseshoe crab specimens that were leftover poisonous food in Vietnam using hydrophilic interaction liquid chromatography linked to tandem mass spectrometry (HILIC‐MS/MS) analysis. According to the results, TTX accounted for almost 90% of the total toxicity in both specimens (4.2 and 30.3 g g −1 ). This was followed by 4,9‐anhydroTTX (anh‐TTX) (2.8 and 17.1 g g −1 ) and 4‐ epimer TTX (4‐TTX) (1.9 and 11.4 g g −1 ). By the phylogenetic analysis based on COXI, two specimens were subsequently identified to be Carcinoscopius rotundicauda , a horseshoe crab that is known to be found across Vietnam and occasionally regarded as local seafood in coastal regions. Together with its strong lethal potency, it was suggested that TTX was the source of food poisoning in Vietnam brought on by the consumption of C. rotundicauda . At 146.2 MU g −1 , specimen 2′s toxicity was almost seven times greater than specimen 1′s (20.3 MU g −1 ). The fact that poisoning symptoms were only observed in those who consumed specimen 2 could be explained by individual differences in TTX toxicity in this horseshoe crab species. To the best of our knowledge, TTX caused by eating horseshoe crabs was originally reported in Vietnam. According to the study, TTX in horseshoe crabs poses a threat to seafood safety in Vietnam.