Survey of Tetrodotoxins (TTXs) in Gastropods, Sea Urchins, and Blue Crabs from the Adriatic Sea: First Report in Paracentrotus lividus.

The detection of tetrodotoxins (TTXs) in European shellfish led the European Union to request a risk assessment from the European Food Safety Authority (EFSA). EFSA set a reference limit of 44 µg TTX equivalents kg-1 and called for more data on TTX occurrence, especially in gastropods, which can accumulate in TTXs but remain poorly studied. Recently, preliminary monitoring has revealed the recurrent presence of TTXs in mussels in three areas along the North-Central Adriatic coast of Italy, while research on non-bivalve organisms has not yet been carried out. This study presents a preliminary survey, conducted from January 2023 to March 2025, on the presence of TTXs in gastropods, echinoderms, and arthropods collected from this area. A method in Hydrophilic Interaction Liquid Chromatography coupled with tandem Mass Spectrometry (HILIC-MS/MS) for detecting TTXs in bivalve mollusks was first tested through an international proficiency test, then optimized for the other invertebrates, the object of this study. TTX levels in all gastropods and arthropod samples were undetectable, while traces (~5 µg kg-1) were found in one echinoderm sample (Paracentrotus lividus), marking the first reported occurrence of TTX in this species. Sea urchins are widely consumed in Italy; therefore, this finding is of particular importance from a public health perspective and deserves further investigation. Some gastropod genera or species sampled (e.g., Nassarius, Rapana venosa) have been identified as TTX carriers in other regions; therefore, the negative results obtained in this study may be related to seasonal or geographic variability. These results provide valuable data to EFSA's call for monitoring emerging risks, particularly as climate change may increase TTX prevalence in European waters as well as worldwide.