General and Comparative Endocrinology 145 (2006) 247–253 www.elsevier.com/locate/ygcen 0016-6480/$ - see front matter  2005 Elsevier Inc. All rights reserved. doi:10.1016/j.ygcen.2005.09.010 The acute stress response of red porgy, Pagrus pagrus, kept on a red or white background A.L. Van der Salm a,b,¤ , M. Pavlidis c,d , G. Flik b , S.E. Wendelaar Bonga a a Department of Animal Ecology and Ecophysiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands b Department of Animal Physiology, Institute for Neuroscience, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands c University of Crete, Department of Biology, P.O. Box 2208, GR-71409 Heraklion, Crete, Greece d Hellenic Centre for Marine Research, Institute of Aquaculture, P.O. Box 2214, GR-71003 Heraklion, Crete, Greece Received 22 October 2004; revised 18 August 2005; accepted 2 September 2005 Available online 25 October 2005 Abstract The skin colour of red porgy, Pagrus pagrus, can be modiWed by exposure to diVerent background colours. Red and white background colours brighten the dark skin colour that develops under common culture conditions in red porgy. To assess whether skin colour is also modiWed by aquaculture related handling stress, we subjected red porgy to 5 min of netting stress combined with air exposure. Fish kept on a white background have: (1) a lighter skin colour, which is not inXuenced by an acute stressor, (2) a less saturated red colour, which signiWcantly decreases 24 h post-handling, and (3) a similar hue as Wsh kept on a red background. The Wrst plasma parameters to rise after application of the stressor are cortisol, lactate and Na + ; then, glucose levels rose. Other plasma ions (Ca 2+ , Cl ¡ , K + ) were not aVected up to 2 h post-stressor, but had decreased at 8 and 24 h after handling. Plasma pH decreased over the Wrst 2 h post-handling, indicative of plasma acidosis upon air exposure. The acidosis then coincided with increases in plasma lactate levels. As MSH levels were not signiW- cantly aVected by the stressor while cortisol levels showed a Wve to tenfold increase, we suggest that following acute stress in red porgy, plasma cortisol release is controlled by ACTH, perhaps in combination with a sympathic stimulation.  2005 Elsevier Inc. All rights reserved. Keywords: Red porgy; Pagrus pagrus; MSH; Acute stress responses; Teleosts; Background adaptation 1. Introduction In Wsh, exposure to harmful or potentially harmful stim- uli causes an integrated stress response similar to that in mammals. The chromaYn cells in the head kidney receive signals from the hypothalamus via the sympathetic nervous system to produce and release catecholamines. The hypo- thalamus further releases neuroendocrine factors that can induce the release of corticotrope signals from the pituitary gland that stimulate the interrenal steroid producing cells of the head kidney to produce and release cortisol into the bloodstream. These two pathways are called hypotha- lamic–sympathetic–chromaYn (HSC) cell axis and hypo- thalamic–pituitary–interrenal (HPI) axis, respectively (Wendelaar Bonga, 1997). In aquaculture, Wsh are frequently exposed to stressful situations such as handling and conWnement. For red porgy, Pagrus pagrus, a relatively new species in aquacul- ture belonging to the Sparidae (Kentouri et al., 1995; Pavlidis et al., 2000), it was demonstrated that stress evoked by crowding results in moderately elevated cortisol levels (Rottlant et al., 1997; Rottlant and Tort, 1997). During handling-induced stress these values doubled. In a study by Arends et al. (1999), the stress response of the gilthead sea bream (Sparus auratus), another sparid Wsh, was tested by exposure of the Wsh to handling. The response of Wsh that * Corresponding author. E-mail addresses: A.vanderSalm@science.ru.nl, angesalm@sci.kun.nl (A.L. Van der Salm).