Single nucleotide polymorphisms in cuticle and secretome-related genes are associated with hydrogen peroxide sensitivity in the sea louse Caligus rogercresseyi

The sea louse Caligus rogercresseyi is the main ectoparasite species affecting the salmon industry in Chile. Hydrogen peroxide (H2O2) is a chemotherapeutant frequently used for lice control, and currently considered as a non-pharmacological method. The H2O2 molecules cause the formation of bubbles in the louse's hemolymph, inducing mechanical paralysis and detaching the parasite from the host. However, the molecular mechanisms underlying the response and potential resistance of the ectoparasite to this chemotherapeutant remains poorly understood. This study aimed to expand the knowledge of candidate genes and single nucleotide polymorphisms (SNPs) involved in the response of C. rogercresseyi to H2O2. Taken the accumulative molecular evidence concerning the molecular responses of lice exposed to delousing compounds, immune-related, antioxidant system, chemosensory receptors, secretome, and cuticle formation genes were evaluated. Herein, lice were experimentally exposed to three concentrations of H2O2 composed by 360, 744, and 1080 mg L−1. Then, novel SNPs in catalase, superoxide dismutase, serpin, cuticle-7, cuticle-19, and trypsin-5 genes were validated in samples from four lice populations with contrasting sensitivity to H2O2. Upregulation of genes related to the antioxidant system, secretome, and cuticle formation in exposed lice was observed. Notably, SNP allele frequencies and transcription analyses suggest that Cuticle-7 and Cuticle-19 genes can be applied for H2O2 sensitivity surveillance in C. rogercresseyi populations. This study contributes to a better understanding of the response to H2O2 in C. rogercresseyi and provides new insights into the potential molecular mechanisms as a chemical treatment. •Novel markers for hydrogen peroxide sensitivity are described for the sea louse.•SNPs are associated with gene expression patterns in lice exposed to H2O2.•Differential heterozygosity in SNPs on cuticle genes on lice population was found.