A rapid behavioral toxicity test using common periwinkle <i>Littorina littorea</i> (Gastropoda: Littorinidae)

Chemical pollution threatens the balance, resilience and health of coastal ecosystems, and there is a need for relevant tools to monitor and assess the sensitivity of these vital ecosystems. The common periwinkle (<i>Littorina littorea</i>) is a key intertidal species of high ecological and biomonitoring relevance. This study aimed to develop a rapid toxicity test to evaluate behavioral responses of <i>L. littorea</i> utilizing 3,4-dichloroaniline (3,4-DCA) as a model compound. The snails were exposed to five concentrations (0.4-15.9 mg/L) over a four-day period, followed by a two-day recovery period. Behavioral endpoints assessed included active suction, righting performance, and feeding response. The exposure resulted in a concentration-dependent decrease in active suction, with snails retracting into their shells, which significantly reduced their oxygen consumption, indicating avoidance behavior. Post-exposure recovery demonstrated impaired righting performance and feeding activity, where higher 3,4-DCA concentrations correlate with reduced responsiveness. Notably, even at the lowest exposure concentration, fewer than 20% of snails were able to right themselves within 24 h, underscoring this as a highly sensitive behavioral endpoint. Feeding assays using <i>Ulva lactuca</i> revealed dose-dependent reductions in feeding activity. In conclusion, our study illustrates that <i>L. littorea</i> displays sensitive and quantifiable behavioral responses to chemical exposure, thereby reinforcing its potential as a non-model species for marine ecotoxicity testing.