Tetrodotoxin Trail: How prey composition and gut microbiome predict contamination in Charonia lampas.

Authors: Smilla Adler1,*, Tânia Aires1, Maria Pais1, Rute Félix1, Aschwin Engelen1, Sandra Lage1

Affiliations: 1Centro de Ciências do Mar do Algarve (CCMAR/CIMAR LA), University of Algarve, Faro, Portugal

* presenting author (sladler@ualg.pt)

Abstract:

The trumpet shell (Charonia lampas) is a predatory marine gastropod from the Western Mediterranean and the northeast Atlantic. It has recently been linked to food poisoning due to the presence of the potent neurotoxin tetrodotoxin (TTX). This study investigated whether differences in diet and gut microbiome are associated with varying TTX levels, testing the hypothesis that the toxin is transferred through contaminated prey. Using metabarcoding, we analysed diet (COI marker) and microbiome composition (16S rRNA V3–V4 region) in 24 specimens. Additionally, TTX-producing bacterial candidates were isolated from non-edible tissues of C. lampas, and the presence of TTX and its analogues was confirmed by LC-HRMS. Our results showed that C. lampas has a diverse diet, mainly feeding on specimens from the phyla Echinodermata, Mollusca, and Cnidaria, with a broader diet in TTX-contaminated individuals that ingested taxa such as Mytilus, Antedonidae, Epizoanthus, and Astropecten. However, no significant effect of TTX contamination on the C. lampas microbiome composition was observed. Finally, we were able to isolate TTX and analogues producing candidates and assigned them as belonging to the genera Vibrio and Acinetobacter. These findings improve understanding of the different cues influencing TTX occurrence in C. lampas and its implications for food safety. Associations with specific dietary patterns and higher toxicity support an exogenous origin of TTX in trumpet shells, while endogenous TTX acquisition is supported by the identification of toxin producing candidates. Conclusively, TTX accumulation in C. lampas results from both exogenous and endogenous toxin acquisition rather than from either route alone.