In-feed additives modulate ionotropic receptor genes from the sea louse Caligus rogercresseyi: A comparative analysis in two host salmonid species

Recently, a group of chemosensory receptors from the ionotropic receptor family was molecularly characterized in the sea louse Caligus rogercresseyi. Nonetheless, understanding the physiological functions of these genes during the sea lice infestation process remains pending. Herein, the aim of this study was to determine the transcriptional modulation of ionotropic receptor genes from C. rogercresseyi while infesting Salmo salar and Oncorhynchus kisutch, as well as to evaluate the effects in-feed additives on sea lice transcriptome. The results revealed significant differences in parasitic load between control diet and the anti-attachment or immunostimulant diet groups. Moreover, there were notable differences in the gene transcription profiles of ionotropic receptors in each group. Under a normal commercial diet, there was a general trend towards higher transcription levels in sea lice infesting S. salar, especially at seven days post-infection. This same tendency occurred in sea lice infesting fish fed an immunostimulant diet, but an opposite trend was found in sea lice infesting fish fed with anti-attachment masking compounds. In this case, sea lice infesting O. kisutch expressed higher ionotropic receptor levels at seven days post-infection. This study advances the knowledge related to ionotropic receptors and the involvement of these in host-parasite interactions, especially in relation to semiochemical signaling detection. This is a contribution to sea lice control in salmon farms. •Ionotropic receptor (IGluR) expression was modulated by in-feed additives in sea lice.•IGluRs were more expressed in lice infesting the susceptible species Salmo salar.•The incorporation of masking compound inverted IGluR expression patterns.•The immunostimulant in-feed additive increased IGluR expression levels.