Melanin-based skin spots reflect stress responsiveness in salmonid fish

• Published in: Hormones and behavior Vol. 56; no. 3; pp. 292 - 298
• Main Authors: Kittilsen, S., Schjolden, J., Beitnes-Johansen, I., Shaw, J.C., Pottinger, T.G., Sørensen, C., Braastad, B.O., Bakken, M., Øverli, Ø.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.09.2009; Elsevier; Elsevier BV
• Subjects: Aging - physiology; Animal behavior; Animal personalities; Animals; Behavior, Animal; Behavioral psychophysiology; Behaviour; Biological and medical sciences; Brackish; Comparative studies; Corticosteroids; Escape Reaction; Feeding Behavior; Fish; Freshwater; Fundamental and applied biological sciences. Psychology; Hormones; Hormones and behavior; Hydrocortisone - blood; Locomotion - physiology; Marine; Melanin; Melanins - metabolism; Neuropsychological Tests; Oncorhynchus mykiss; Oncorhynchus mykiss - physiology; Pigment; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Salmo salar; Salmo salar - physiology; Salmonid fish; Skin Physiological Phenomena; Skin Pigmentation - physiology; Social Isolation; Stress; Stress response; Stress, Physiological - physiology; Stress, Psychological; Syndromes; Teleostei; Time Factors; Pigment; Salmonid fish; Corticosteroids; Behaviour; Syndromes; Stress response; Melanin; Animal personalities; Corticosteroid; Personality; Stress; Animal; Skin; Behavior
• ISSN: 0018-506X; 1095-6867
• DOI: 10.1016/j.yhbeh.2009.06.006

Within animal populations, genetic, epigenetic and environmental factors interact to shape individual neuroendocrine and behavioural profiles, conferring variable vulnerability to stress and disease. It remains debated how alternative behavioural syndromes and stress coping styles evolve and are maintained by natural selection. Here we show that individual variation in stress responsiveness is reflected in the visual appearance of two species of teleost fish; rainbow trout ( Oncorhynchus mykiss) and Atlantic salmon ( Salmo salar). Salmon and trout skin vary from nearly immaculate to densely spotted, with black spots formed by eumelanin-producing chromatophores. In rainbow trout, selection for divergent hypothalamus–pituitary–interrenal responsiveness has led to a change in dermal pigmentation patterns, with low cortisol-responsive fish being consistently more spotted. In an aquaculture population of Atlantic salmon individuals with more spots showed a reduced physiological and behavioural response to stress. Taken together, these data demonstrate a heritable behavioural–physiological and morphological trait correlation that may be specific to alternative coping styles. This observation may illuminate the evolution of contrasting coping styles and behavioural syndromes, as occurrence of phenotypes in different environments and their response to selective pressures can be precisely and easily recorded.