Peptidomic Identification of Behaviour-Modulating Putative Neuropeptides in Schistosoma mansoni Miracidia

Neuropeptides regulate diverse physiological and behavioural processes in parasites, yet their functional roles in the infective larval stages of Schistosoma mansoni remain poorly defined. In this study, we identified miracidia-derived putative neuropeptides and examined their roles in regulating miracidial behaviour. Peptidomic analysis revealed ten putative neuropeptides, including five whose proteomic identification in this life stage was previously unreported. Neuropeptide precursor proteins were evaluated for stage-specific expression and Schistosoma genus specificity to prioritise candidates with potential functional and biocontrol relevance. Protein-protein interaction analysis identified Smp_176700 as a highly connected neuropeptide precursor associated with proteins implicated in miracidial structure and infection. Eight putative neuropeptides derived from six precursor proteins were synthesised and externally applied to miracidia in acute (1 min) and prolonged (360 min) behavioural assays. During acute exposure, most peptides induced significant concentration-dependent behavioural changes at 3 mg/mL and 0.1 mg/mL, characterised by reduced swimming velocity and increased directional change, with no significant effects at 0.01 mg/mL. Prolonged exposure revealed peptide-specific effects, with ASLSYF-OH and FLLGLPPSLRQH-OH producing the most pronounced behavioural modulation. These findings demonstrate that S. mansoni miracidia express bioactive neuropeptides capable of modulating larval behaviour, providing insight into schistosome neurobiology and identifying potential targets for transmission-blocking interventions.