Histological and transcriptomic analysis of muscular atrophy associated with depleted flesh pigmentation in Atlantic salmon (Salmo salar) exposed to elevated seawater temperatures

• Published in: Scientific Reports
• Main Authors: Vo, TTM, Amoroso, G, Ventura, T, Elizur, A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2023
• Subjects: Agricultural; Veterinary and Food Sciences; Fisheries sciences; Aquaculture; Atlantic salmon; Salmo salar
• Online Access: https://doi.org/10.1038/s41598-023-31242-2; http://www.ncbi.nlm.nih.gov/pubmed/36918611; http://ecite.utas.edu.au/155766

Tasmania is experiencing increasing seawater temperatures during the summer period which often leads to thermal stress-induced starvation events in farmed Atlantic salmon, with consequent flesh pigment depletion. Our previous transcriptomic studies found a link between flesh pigmentation and the expression of genes regulating lipid metabolism accompanied by feeding behavior in the hindgut. However, the impact of prolonged exposure to elevated water temperature on muscle structural integrity and molecular mechanisms in muscle underlying pigment variation has not been elucidated to date. In this study, we investigated the effect of prolonged exposure to elevated water temperature on the farmed salmon flesh pigmentation and structural integrity, using muscle histological and transcriptomic analysis. On April 2019, after the end of the summer, two muscle regions of the fish fillet, front dorsal and back central (usually the most and least affected by depletion, respectively), were sampled from fifteen fish (weighing approximately 2 kg and belonging to the same commercial population split in two cages). The fish represented three flesh color intensity groups (n = 5 fish per group) categorized according to general level of pigmentation and presence of banding (i.e. difference in color between the two regions of interest) as follows: high red color-no banding (HN), high red color-banded (HB) and Pale fish. Histological analysis showed a distinction between the flesh color intensity phenotypes in both muscle regions. Muscle fibers in the HB fish were partly degraded, while they were atrophied and smaller in size in Pale fish compared to HN fish. In the Pale fish, interstitial spaces between muscle fibers were also enlarged. Transcriptomic analysis showed that in the front dorsal region of the HN fish, genes encoding collagens, calcium ion binding and metabolic processes were upregulated while genes related to lipid and fatty acid metabolism were downregulated when compared to HB fish. When comparing the back central ...