title: Effects of acute stress on aggression and the cortisol response in the African sharptooth catfish Clarias gariepinus: differences between day and night.
abstract: African sharptooth catfish Clarias gariepinus were housed under continuous dim light (1 lx) or 12L:12D (350-0 lx) cycles. The number of skin lesions, as indicator of aggressive acts, and plasma cortisol levels, as indicator of stress-axis activity, were measured at baseline as well as following a stressor (given in the light or dark phase). Results showed that (1) baseline plasma cortisol levels were not different between photoperiods, (2) the number of baseline skin lesions was highest for C. gariepinus housed under continuous dim light, (3) stressor-induced peak levels of plasma cortisol were highest in the light phase and (4) the number of skin lesions following a stressor was highest in the dark phase. The higher number of stressor-related skin lesions in the dark (active) phase suggests increased stressor-induced aggression while in the active phase. In addition, the data suggest that housing under continuous dim light does not result in higher stress-axis activity, as measured by baseline levels of cortisol, but does result in more stressor-induced aggression, as measured by the higher number of skin lesions. The latter may be related to the fact that the continuous dim light photoperiod has twice the number of dark-phase (active) hours in which stressor-induced aggression is stronger compared to the 12L:12D photoperiod, which has a light phase in which stressor-induced aggression is lower.
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, 6525 AJ, Nijmegen, the Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Manuel
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, 6525 AJ, Nijmegen, the Netherlands.
authors.forename: J G J
authors.initials: JG
authors.lastname: Boerrigter
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, 6525 AJ, Nijmegen, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Cloosterman
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, 6525 AJ, Nijmegen, the Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Gorissen
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, 6525 AJ, Nijmegen, the Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: Flik
authors.affiliation: Radboud University, Institute for Water and Wetland Research, Department of Animal Physiology, Heyendaalseweg 135, 6525 AJ, Nijmegen, the Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: van den Bos
authors.affiliation: IMARES, Wageningen UR, P. O. Box 77, 4401 NT, Yerseke, the Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: van de Vis
mesh_terms: D000374:Aggression; D000818:Animals; D001522:Behavior, Animal / Q000528:radiation effects; D002397:Catfishes / Q000502:physiology*; D006854:Hydrocortisone / Q000097:blood*; D008027:Light; D017440:Photoperiod; D013312:Stress, Physiological
chemical_list: D006854:Hydrocortisone
keywords: Clarias gariepinus; behaviour; photoperiod; skin lesions