title: Metabolic adjustments in breeding female kittiwakes (Rissa tridactyla) include changes in kidney metabolic intensity.
abstract: Black-legged kittiwakes (BLKIs) reduce self-maintenance cost through reductions in mass-specific basal metabolic rate (BMR), body mass and the size of visceral organs during the chick-rearing period. In the present study, we measured kidney in vitro oxygen consumption and plasma 3,3',5-triiodo-L: -thyronine (T3) levels of incubating and chick-rearing female BLKIs, to test whether the decrease in BMR is caused mainly by decreased metabolic intensity or simply by reductions in the size of organs with high metabolic intensity. Body mass and body condition were lower in chick-rearing birds compared with the incubating birds. In contrast to the previous findings, however, the kidney mass did not differ between the two breeding stages. Plasma T3 levels decreased substantially during the breeding season, indicating a reduction in BMR. Over the same period, kidney mass-specific oxygen consumption decreased (by 17.2%) from the incubating to the chick-rearing stage. Thus, the reduction in BMR found in breeding BLKIs seems partly explained by adjustments in metabolic intensity of visceral organs. Lowered metabolic intensity of visceral organs would permit increased allocation of energy to offspring at the expense of their own self-maintenance.
authors.affiliation: Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway. bernt.ronning@bio.ntnu.no
authors.forename: Bernt
authors.initials: B
authors.lastname: Rønning
authors.forename: Børge
authors.initials: B
authors.lastname: Moe
authors.forename: Olivier
authors.initials: O
authors.lastname: Chastel
authors.forename: Juli
authors.initials: J
authors.lastname: Broggi
authors.forename: Magdalene
authors.initials: M
authors.lastname: Langset
authors.forename: Claus
authors.initials: C
authors.lastname: Bech
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001835:Body Weight; D046091:Charadriiformes / Q000378:metabolism*; D015536:Down-Regulation; D004734:Energy Metabolism; D005260:Female; D007668:Kidney / Q000033:anatomy & histology / Q000378:metabolism*; D008425:Maternal Behavior; D009425:Nesting Behavior; D009929:Organ Size; D010101:Oxygen Consumption; D012098:Reproduction; D014284:Triiodothyronine / Q000097:blood
chemical_list: D014284:Triiodothyronine