Arctic charr were allowed to interact in groups of three for 5 days. Skin darkness was quantified by measuring the mean brightness of individual fish before and after social interaction. Brain levels of monoamines and monoamine metabolites and plasma concentrations of cortisol, adrenocorticotropic hormone (ACTH), N-acetyl-(beta)-endorphin and alpha-melanocyte-stimulating hormone (alpha-MSH) were analysed. The results show that social subordination resulted in a significant skin darkening. Furthermore, plasma concentrations of alpha-MSH, ACTH and cortisol were elevated in subordinates, and these fish also displayed elevated levels of 5-hydroxyindoleacetic acid (5-HIAA) in the telencephalon. The ratio of [5-HIAA] to serotonin [5-HT] was increased in several brain areas. In addition, the ratio of 3-methoxy-4-hydroxyphenylglycol (MHPG) to norepinephrine (NE) concentrations was significantly increased in the optic tectum of subordinate fish. Skin darkness following social interaction showed a significant positive correlation with plasma levels of alpha-MSH. Plasma levels of ACTH and alpha-MSH were both positively correlated with that of cortisol. Brain [5-HIAA]/[5-HT] ratios were positively correlated with circulating plasma levels of ACTH, and a similar positive correlation was seen between [MHPG]/[NE] ratios in the optic tectum and plasma levels of ACTH, alpha-MSH and N-acetyl-beta-endorphin. In contrast, hypothalamic [MHPG]/[NE] ratios displayed a negative correlation with plasma alpha-MSH concentrations. The present study demonstrates that social stress induces skin darkening in Arctic charr and that this effect could be mediated by a stress-induced increase in the levels of alpha-MSH in the circulation. Furthermore, the results suggest that 5-HT and NE in the central nervous system could be factors regulating the pituitary release of ACTH and alpha-MSH.
Applications open for Workshop on vertebrate gut physiology
(update)-GutWorkshop2.jpg?versionId=4191)
Applications are now open for Inside Out: New Frontiers in the Comparative Physiology of the Vertebrate Gut, a Workshop organised by Carol Bucking and Chris M. Wood that will examine the function of the vertebrate gastro-intestinal tract. Funded places are available for early-career researchers.
In the field: an interview with Chris Wood
-Conversation.png?versionId=4191)
Professor Chris Wood talks about his experiences on the legendary R/V Alpha Helix expedition to the Amazon in 1976, his development of the Tusker Chamber in Kenya and more recent adventures on Vancouver Island, Canada.
Docile raccoons are likely trash can criminal masterminds
-Raccoons.jpg?versionId=4191)
Raccoons are notoriously adaptable to city dwelling, but it's not the bold proactive animals that you need to be wary of; it's the docile animals which are the best learners and likely trash can raiding criminal masterminds.
Finding the right thermal limit
-Review.png?versionId=4191)
In this Review, Michael Ørsted, Lisa Bjerregaard Jørgensen and Johannes Overgaard present a framework to reconcile methodological measurements and mechanisms related to the physiology of heat stress tolerance limits, thermal injury and repair in ectotherms.
Resources for early-career researchers
Social media
