Invest more and die faster: The life history of a parasite on intensive farms

Abstract

Organisms are expected to respond to alterations in their survival by evolutionary changes in their life history traits. As agriculture and aquaculture have become increasingly intensive in the past decades, there has been growing interest in their evolutionary effects on the life histories of agri‐ and aquacultural pests, parasites, and pathogens. In this study, we used salmon lice (Lepeophtheirus salmonis) to explore how modern farming might have affected life history evolution in parasites. We infected salmon hosts with lice from either farmed or unfarmed locations, and monitored life history traits of those parasites in laboratory conditions. Our results show that compared to salmon lice from areas unaffected by salmon farming, those from farmed areas produced more eggs in their first clutch, and less eggs later on; they achieved higher infestation intensities in early adulthood, but suffered higher adult mortality. These results suggest that salmon lice on farms may have been selected for increased investment in early reproduction, at the expense of later fecundity and survival. This call for further empirical studies of the extent to which farming practices may alter the virulence of agricultural parasites.

Rich resource environment of fish farms facilitates phenotypic variation and virulence in an opportunistic fish pathogen

“…Combined with the higher growth rate of the rough morphotype at fish farms, morphotype reversibility is likely to increase the probability of columnaris epidemics at fish farms. Our results contribute to the growing evidence of the crucial role of intensive aquaculture in driving evolution in microbial pathogens (Mennerat et al, 2010;Pulkkinen et al, 2010;Sundberg et al, 2016;Mennerat et al, 2017).…”

Genetic fingerprinting of salmon louse (Lepeophtheirus salmonis) populations in the North-East Atlantic using a random forest classification approach

“…(Bricknell et al 2006)), for example, can have profound effects on sea louse survival and development. Furthermore, a combination of drug treatment and increased host density is shown to influence the evolution of reproductive and life history traits (Mennerat et al 2017), as well as virulence in sea lice (Mennerat et al 2012) among different populations. However, such local adaptation is most likely linked to subtle allele frequency differences, compared to strong selective sweeps caused by drug treatments, as the selective pressure is comparably low.…”

The planktonic stages of the salmon louse (Lepeophtheirus salmonis) are tolerant of end-of-century pCO2 concentrations

“…Salmon lice will inevitably experience a variable environment that features pH regimes far below that predicted from OA. Considering the tolerance of L. salmonis to elevated p CO 2 demonstrated here, and their adaptability documented elsewhere (e.g., Aaen et al, 2015; Mennerat et al, 2017; Ljungfeldt et al, 2017), we should expect them to readily adapt to future OA scenarios.…”