title: Cortisol is responsible for positive and negative effects in the ovarian maturation induced by the exposure to acute stressors in Nile tilapia, Oreochromis niloticus.
abstract: The aim of the present study was to evaluate the effect of acute stress and cortisol injection on oocyte final maturation process in female Nile tilapia (Oreochromis niloticus). Handling followed by a prophylactic treatment (0.3 mL L(-1) H(2)O(2), 5 g L(-1) NaCl solution during 30 min) and an environmental change (transfer from a 2 m(3) fibreglass square tank to 50 L aquaria) were used as acute stressors and compared to a single cortisol injection (0.5 or 5 mg kg(-1) body weight). For both acute stress and cortisol injection (0.5 mg kg(-1) body weight), serum cortisol level was significantly increased from 2.3 to 134.1 ng mL(-1) 1 h post-stress/injection and returned to a resting basal value 24 h after the stress/injection. In fish injected with 5 mg kg(-1) body weight cortisol, mean serum cortisol level reached a peak up to 2500 ng mL(-1) 1 h after injection. 63 % of the females (mean body weight: 242 ± 4 g) submitted to the acute stress ovulated within 72 h after the stress. In the same way, cortisol injection (5 mg kg(-1) body weight) at the 10th day of the maturation cycle led to a twofold reduction of the time before ovulation compared to vehicle injected control fish. Relative and total fecundity were significantly decreased in females submitted to an acute stress or cortisol injected at 5 mg kg(-1) body weight, but not fertilization or hatching rates. In conclusion, acute stress and cortisol induction exert both positive and negative effects on the final reproductive process in O. niloticus, and cortisol is the endocrine mediator causing these changes.
authors.affiliation: Aquaculture Research and Education Centre (CEFRA), University of Liège, 10 Chemin de la Justice, 4500, Tihange, Belgium.
authors.forename: Vincent
authors.initials: V
authors.lastname: Gennotte
authors.affiliation: Direction Générale des Ressources Halieutiques, BP7010, Ouagadougou 03, Burkina Faso.
authors.forename: Philippe
authors.initials: P
authors.lastname: Sawadogo
authors.affiliation: Research Unit in Environmental and Evolutive Biology (URBE), The University of Namur, 61 rue de Bruxelles, 5000, Namur, Belgium.|Unité de Recherche Animal et Fonctionnalités des Produits Animaux, Université de Lorraine, 2 avenue de la Forêt de Haye, B.P. 172, 54505, Vandoeuvre-lès-Nancy, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Milla
authors.affiliation: Research Unit in Environmental and Evolutive Biology (URBE), The University of Namur, 61 rue de Bruxelles, 5000, Namur, Belgium.
authors.forename: Patrick
authors.initials: P
authors.lastname: Kestemont
authors.affiliation: Aquaculture Research and Education Centre (CEFRA), University of Liège, 10 Chemin de la Justice, 4500, Tihange, Belgium.
authors.forename: Charles
authors.initials: C
authors.lastname: Mélard
authors.affiliation: Aquaculture Research and Education Centre (CEFRA), University of Liège, 10 Chemin de la Justice, 4500, Tihange, Belgium. c.rougeot@ulg.ac.be.
authors.forename: Carole
authors.initials: C
authors.lastname: Rougeot
mesh_terms: D000818:Animals; D023681:Cichlids; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006854:Hydrocortisone / Q000378:metabolism / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D010053:Ovary / Q000187:drug effects* / Q000502:physiology; D012741:Sexual Maturation; D013312:Stress, Physiological / Q000502:physiology*
chemical_list: D006854:Hydrocortisone