Cable, J. | Search bioRxiv

bioRxiv2018

Contrasting effects of acute and chronic stress on the transcriptome, epigenome, and immune response of Atlantic salmon

Early-life stress can have long-lasting effects on immunity, but the underlying molecular mechanisms are unclear. We examined the effects of acute stress (cold-shock during embryogenesis) and chronic stress (absence of tank enrichment during larval-stage) on the gill transcriptome and methylome of Atlantic salmon four months after hatching. While only chronic stress induced pronounced transcriptional effects, both acute and chronic stress caused lasting, and contrasting, changes in the methylome. Crucially, we found that acute stress enhanced immune response to a pathogenic challenge (lipopolysaccharide), while chronic stress suppressed it. We identified stress-induced changes in promoter or gene-body methylation that were associated with altered expression for a small proportion of genes, and also evidence of wider epigenetic regulation within signalling pathways involved in immune response. Our study suggests that early-life stress can affect immuno-competence through epigenetic mechanisms, a finding that could open the way for improved stress and disease management of farmed fish.

genomics↗

bioRxiv2018

Simultaneous detection of invasive signal crayfish, endangered white-clawed crayfish and the crayfish plague pathogen using environmental DNA

Aquatic Invasive Species (AIS) are important vectors for the introduction of novel pathogens which can, in turn, become drivers of rapid ecological and evolutionary change, compromising the persistence of native species. Conservation strategies rely on accurate information regarding presence and distribution of AIS and their associated pathogens to prevent or mitigate negative impacts, such as predation, displacement or competition with native species for food, space or breeding sites. Environmental DNA is increasingly used as a conservation tool for early detection and monitoring of AIS. We used a novel eDNA high-resolution melt curve (HRM) approach to simultaneously detect the UK endangered native crayfish (Austropotamobius pallipes), the highly invasive signal crayfish (Pacifastacus leniusculus) and their dominant pathogen, Aphanomyces astaci, (causative agent of crayfish plague). We validated the approach with laboratory and field samples in areas with known presence or absence of both crayfish species as well as the pathogen, prior to the monitoring of areas where their presence was unknown. We identified the presence of infected signal crayfish further upstream than previously detected in an area where previous intensive eradication attempts had taken place, and the coexistence of both species in plague free catchments. We also detected the endangered native crayfish in an area where trapping had failed. With this method, we could estimate the distribution of native and invasive crayfish and their infection status in a rapid, cost effective and highly sensitive way, providing essential information for the development of conservation strategies in catchments with populations of endangered native crayfish.

ecology↗