title: Maternal thyroid hormones enhance hatching success but decrease nestling body mass in the rock pigeon (Columba livia).
abstract: Thyroid hormones (THs) - triiodothyronine (T3) and thyroxine (T4) - are essential for embryonic development in vertebrates. All vertebrate embryos are exposed to THs from maternal origin. As maternal TH levels are known to be essential to embryonic development, the natural variation of maternal THs probably represents a pathway of maternal effects that can modify offspring phenotype. However, potential fitness consequences of variation of maternal TH exposure within the normal physiological range and without confounding effects of the mother have never been experimentally investigated. We experimentally manipulated the levels of yolk T3 and T4 within the physiological range in a species in which the embryo develops outside the mother's body, the Rock Pigeon (Columba livia) eggs. Making use of the natural difference of yolk testosterone between the two eggs of pigeon clutches, we were also able to investigate the potential interaction between THs and testosterone. Elevated yolk TH levels enhanced embryonic development and hatching success, and reduced body mass but not tarsus length between day 14 and fledging. The yolk hormones increased plasma T4 concentrations in females but reduced it in males, in line with the effect on metabolic rate at hatching. Plasma concentrations of T3 and testosterone were not significantly affected. The effects of treatment did not differ between eggs with high or low testosterone levels. Our data indicate that natural variation in maternal yolk TH levels affects offspring phenotype and embryonic survival, potentially influencing maternal and chick fitness.
authors: Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands. Electronic address: biyahs@utu.fi.
authors: Bin-Yan
authors: BY
authors: Hsu
authors: Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors: Cor
authors: C
authors: Dijkstra
authors: Laboratory of Comparative Endocrinology, Section of Animal Physiology and Neurobiology, KU Leuven, Naamsestraat 61, B-3000 Leuven, Belgium.
authors: Veerle M
authors: VM
authors: Darras
authors: Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors: Bonnie
authors: B
authors: de Vries
authors: Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
authors: Ton G G
authors: TGG
authors: Groothuis
mesh_terms: D000818:Animals; D001481:Basal Metabolism; D001835:Body Weight; D010856:Columbidae / Q000033:anatomy & histology* / Q000097:blood / Q000254:growth & development* / Q000378:metabolism; D005260:Female; D016014:Linear Models; D008297:Male; D009425:Nesting Behavior; D016019:Survival Analysis; D013739:Testosterone / Q000097:blood; D013963:Thyroid Hormones / Q000097:blood / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D013963:Thyroid Hormones; D014284:Triiodothyronine; D013739:Testosterone; D013974:Thyroxine
keywords: Bird; Hatching asynchrony; Hatching success; Maternal effect; Yolk testosterone; Yolk thyroid hormone