The Atlantic salmon (Salmo salar) antimicrobial peptide cathelicidin-2 is a molecular host-associated cue for the salmon louse (Lepeophtheirus salmonis)

Abstract

Chemical signals are a key element of host-parasite interactions. In marine ecosystems, obligate ectoparasites, such as sea lice, use chemical cues and other sensory signals to increase the probability of encountering a host and to identify appropriate hosts on which they depend to complete their life cycle. The chemical compounds that underlie host identification by the sea lice are not fully described or characterized. Here, we report a novel compound - the Atlantic salmon (Salmo salar) antimicrobial peptide cathelicidin-2 (Cath-2) – that acts as an activation cue for the marine parasitic copepod Lepeophtheirus salmonis. L. salmonis were exposed to 0, 7, 70 and 700 ppb of Cath-2 and neural activity, swimming behaviour and gene expression profiles of animals in response to the peptide were evaluated. The neurophysiological, behavioural and transcriptomic results were consistent: L. salmonis detects Cath-2 as a water-soluble peptide released from the skin of salmon, triggering chemosensory neural activity associated with altered swimming behaviour of copepodids exposed to the peptide, and chemosensory-related genes were up-regulated in copepodids exposed to the peptide. L. salmonis are activated by Cath-2, indicating a tight link between this peptide and the salmon louse chemosensory system.

Effect of handling and crowding on the susceptibility of Atlantic salmon (Salmo salar L.) to Lepeophtheirus salmonis (Krøyer) copepodids

“…Núñez‐Acuña et al. (2018) recently showed that the antimicrobial peptide cathelicidin‐2 present in Atlantic salmon skin and mucus is a molecular host‐associated cue for the salmon louse L. salmonis, as it is detected by the parasite which can then modify its swimming behaviour. For instance, it could be of interest to study the effect of cortisol and/or stressing procedures on the production of this molecule in skin mucus to test our hypothesis.…”

“…Regarding the infestation stage, copepodid attachment behaviour is triggered by a combination of visual, mechanosensory and chemosensory stimuli (Fields et al., 2018; Mordue & Birkett, 2009). Some of the semiochemicals released by the mucus of fish have already been demonstrated to be involved in host‐parasite interactions (Bailey et al., 2006; Delfosse & Pageat, 2014; Ingvarsdóttir et al., 2002; Mordue & Birkett, 2009; Núñez‐Acuña et al., 2018; Pageat & Delfosse, 2014; Pino‐Marambio et al., 2007).…”

Salmo salar fish waste oil: Fatty acids composition and antibacterial activity

“…Marine organisms are a very important source of antimicrobial agents (Richards et al, 2001;Schillaci et al, 2010;Schillaci et al, 2013;Spinello et al, 2018;Vazzana et al, 2018;Núñez Acuña et al, 2018) and, among them, the PUFAs are normally present at high levels in Salmo salar (Linder, Fanni & Parmentier, 2005;Morais et al, 2009). Different studies have shown the antimicrobial activity of the salmon PUFAs against Gram-positive bacteria due to their specific components such as eicosapentaenoic acid (Desbois, Mearns-Spragg & Smith, 2009;Desbois & Lawlor, 2013), docosahexaenoic acid (Coonrod, 1987;Feldlaufer et al, 1993;Gladyshev et al, 2009), γ-linolenic acid (Asthana et al, 2006) and dihomoγ-linolenic acid (Feldlaufer et al, 1993).…”

Chromosome-scale genome assembly of the sea louse Caligus rogercresseyi by SMRT sequencing and Hi-C analysis

“…Host identification via detection of semiochemicals has also been reported 16 . In C. rogercresseyi, the presence of advanced chemoreceptors that are capable of identifying specific molecules of different host species has recently been described [17][18][19] . Herein, the gene family of ionotropic receptors (IRs) are pivotal molecular components for the salmon-louse interaction 20,21 .…”