Investigating the underlying mechanisms of temperature-related skin diseases in Atlantic salmon, Salmo salar L., as measured by quantitative histology, skin transcriptomics and composition

Skin integrity is recognized as of vital consideration for both animal welfare and final product quality of farmed fish. This study examines the effects of three different rearing temperatures (4, 10 and 16 °C) on the skin of healthy Atlantic salmon post-smolts. Changes in skin condition were assessed by the means of skin composition analyses, quantitative histology assessments and transcriptome analysis. Level of protein, vitamin C and vitamin E was significantly higher at 16 °C compared with 4 °C. Quantitative histology measurements showed that the epidermal thickness decreased from low to high temperature, whereas the epidermal area comprising mucous cells increased. The difference was only significant between 4 and 16 °C. Both high and low temperature exhibited significant changes in the skin transcriptome. A number of immune-related transcripts responded at both temperatures. Contrary to well-described immunosuppressive effects of low water temperature on systemic immunity, a subtle increase in skin-mediated immunity was observed, suggesting a pre-activation of the mucosal system at 4 °C. Upregulation of a number of heat-shock proteins correlating with a decrease in epidermal thickness suggested a stress response in the skin at high temperature. The results demonstrate distinctive temperature-related effects on the skin of Atlantic salmon.

Combining animal personalities with transcriptomics resolves individual variation within a wild-type zebrafish population and identifies underpinning molecular differences in brain function

Resolving phenotype variation within a population in response to environmental perturbation is central to understanding biological adaptation. Relating meaningful adaptive changes at the level of the transcriptome requires the identification of processes that have a functional significance for the individual. This remains a major objective towards understanding the complex interactions between environmental demand and an individual's capacity to respond to such demands. The interpretation of such interactions and the significance of biological variation between individuals from the same or different populations remain a difficult and under-addressed question. Here, we provide evidence that variation in gene expression between individuals in a zebrafish population can be partially resolved by a priori screening for animal personality and accounts for >9% of observed variation in the brain transcriptome. Proactive and reactive individuals within a wild-type population exhibit consistent behavioural responses over time and context that relates to underlying differences in regulated gene networks and predicted protein-protein interactions. These differences can be mapped to distinct regions of the brain and provide a foundation towards understanding the coordination of underpinning adaptive molecular events within populations.