Relationships between contaminants and hormones involved in breeding decisions in polar seabirds

• Main Author: Tartu, Sabrina
• Other Authors: La Rochelle, Chastel, Olivier
• Format: Thesis
• Language: English
• Published: 2014
• Subjects: POPs d’héritage; Mercure; Perturbation endocrinienne; Valeur sélective; Oiseaux marins; Arctique; Antarctique; Legacy POPs; Mercury; Endocrine disruption; Fitness; Seabirds; Arctic; Antarctica; envir; socio; Antarctic; Antarc*; Antarctique*; Arctique*
• Online Access: http://www.theses.fr/2014LAROS022/document

In order to maximise fitness, individuals will have to take several decisions that shall match with environmental conditions (whether to breed or not, when to breed, what level of parental investment). These decisions are mediated by hormones : such as luteinizing hormone (LH), a pituitary hormone involved in the onset of breeding, stress hormones (corticosterone, CORT) and prolactin (PRL) a pituitary hormone involved in the expression of parental care. Environmental contaminants are present world-wide, and also in Polar Regions. Since many contaminants are endocrine disruptors, they may impair breeding decisions, but evidences are scarce for wildlife. The aim of this thesis was to assess the relationships between some legacy persistent organic pollutants (POPs : PCBs, organochlorine pesticides), mercury (Hg) and hormones (LH, CORT, PRL) in different Arctic and Antarctic seabird species. Results show that POPs and Hg clearly interact with LH, CORT and PRL secretion. These contaminants appear to target different hormones : increasing Hg was related to decreasing pituitary hormone secretion (LH and PRL) whereas increasing PCBs were linked to an exacerbated CORT response to an acute stress. Hg disrupted LH secretion by probably suppressing GnRH input to the pituitary PCBs seem to act at the adrenal level by probably stimulating ACTH receptors. Legacy POPs and Hg are therefore able to disrupt reproductive decisions and to impact fitness : elevated Hg levels were linked to skipped reproduction and poor incubation behavior elevated PCB levels may make individuals more susceptible to environmental perturbations. The long-term consequences of contaminant exposure for seabirds are discussed in the context of the environmental challenges affecting polar regions. De façon à maximiser leur valeur sélective, les individus doivent prendre différentes décisions qui doivent concorder aux conditions environnementales (se reproduire ou pas ? quand ? quel investissement parental ?). Ces décisions sont fortement influencées ...