Deltamethrin (AlphaMax™) reveals modulation of genes related to oxidative stress in the ectoparasite Caligus rogercresseyi: Implications on delousing drug effectiveness

Abstract

Abstract Deltamethrin is an insecticide authorized for use against the ectoparasite Caligus rogercresseyi in salmon aquaculture. The biodegradation of this insecticide is principally catalyzed through P450 enzymes, carboxylesterases, and glutathione-S-transferase, increasing the amount of free radicals that could promote the activation of oxidative stress response. The present study identified and evaluated the transcriptomic expression of genes related to the antioxidant system in male and female C. rogercresseyi exposed to deltamethrin (AlphaMax™). Herein, thirty-three transcripts were identified from an EST-database, including Cr GST, Cr GST-kappa 1, Cr SOD, Cr CAT, Cr SE-GPx, Cr PHGP1, Cr PHGP2, Cr PRX6, Cr PRX2, Cr PRX4, and Cr FERR. The transcription patterns during the life cycle of C. rogercresseyi revealed conspicuous clusters of gene expression, which was composed by Cr GST and Cr PRX2 associated with the early stages of larval development, and Cr SE-GPx and Cr PHGP1 mainly related to adults. Moreover, the transcript expression for 11 genes of the antioxidant system exposed to deltamethrin revealed that at 2 ppb the transcriptional activity of Cr SOD, Cr CAT, Cr PRX6, Cr PHGP1, and Cr PHGP2 was significantly up-regulated. These results suggest that deltamethrin modulates the expression of genes belonging to the antioxidant system in salmon lice, promoting the generation of free radicals for the biodegradation of the insecticide. The implications of this antioxidant activity on the effectiveness of delousing drugs in controlling C. rogercresseyi are discussed.