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Flight capacity is one of the most important innovations in animal evolution; it only evolved in insects, birds, mammals and the extinct pterodactyls. Given that powered flight represents a demanding aerobic activity, an efficient cardiovascular system is essential for the continuous delivery of oxygen to the pectoral muscles during flight. It is well known that the limiting step in the circulation is stroke volume (the volume of blood pumped from the ventricle to the body during each beat), which is determined by the size of the ventricle. Thus, the fresh mass of the heart represents a simple and repeatable anatomical measure of the aerobic power of an animal. Although several authors have compared heart masses across bird species, a phylogenetic comparative analysis is still lacking. By compiling heart sizes for 915 species and applying several statistical procedures controlling for body size and/or testing for adaptive trends in the dataset (e.g. model selection approaches, phylogenetic generalized linear models), we found that (residuals of) heart size is consistently associated with four categories of flight capacity. In general, our results indicate that species exhibiting continuous hovering flight (i.e. hummingbirds) have substantially larger hearts than other groups, species that use flapping flight and gliding show intermediate values, and that species categorized as poor flyers show the smallest values. Our study reveals that on a broad scale, routine flight modes seem to have shaped the energetic requirements of birds sufficiently to be anatomically detected at the comparative level., Funding Agencies|Fondo Nacional de Desarrollo Cientifico y Tecnologico [1130750, 11160271]; Linkopings Universitet; Svenska Forskningsradet Formas; Direccion General de Investigacion Cientifica y Tecnica [CGL2012-36345]; Comision Nacional de Investigacion Cientifica y Tecnologica

Flight capacity is one of the most important innovations in animal evolution; it only evolved in insects, birds, mammals and the extinct pterodactyls. Given that powered flight represents a demanding aerobic activity, an efficient cardiovascular system is essential for the continuous delivery of oxygen to the pectoral muscles during flight. It is well known that the limiting step in the circulation is stroke volume (the volume of blood pumped from the ventricle to the body during each beat), which is determined by the size of the ventricle. Thus, the fresh mass of the heart represents a simple and repeatable anatomical measure of the aerobic power of an animal. Although several authors have compared heart masses across bird species, a phylogenetic comparative analysis is still lacking. By compiling heart sizes for 915 species and applying several statistical procedures controlling for body size and/or testing for adaptive trends in the dataset (e.g. model selection approaches, phylogenetic generalized linear models), we found that (residuals of ) heart size is consistently associated with four categories of flight capacity. In general, our results indicate that species exhibiting continuous hovering flight (i.e. hummingbirds) have substantially larger hearts than other groups, species that use flapping flight and gliding show intermediate values, and that species categorized as poor flyers show the smallest values. Our study reveals that on a broad scale, routine flight modes seem to have shaped the energetic requirements of birds sufficiently to be anatomically detected at the comparative level.

Domesticering är en urvalsprocess för önskvärda egenskaper hos djur som över tid förändrar deras utseende, beteende och genetik. Några exempel av djur som genomgått denna riktade avel är vargen, mufflon, uroxen, vildsvinet och den röda djungelhönan som vi idag känner som hunden, fåret, kon, grisen och slaktkycklingen. Några gemensamma egenskaper hos domesticerade djur är minskad rädsla för människor, och att de troligen har en högre stresstolerans jämfört med sina vilda förfäder. Det finns två huvudsakliga fysiologiska mekanismer som styr dessa responser, en hormonell och en nervös. Nervsystemet är i sin tur uppdelat i sympatiska och parasympatiska nervsystemet vilka har motsatta roller för kroppens funktioner. Under stress ger det sympatiska den så kallade ”Fight-and-flight”-responsen, och det parasympatiska aktiveras under vila och kallas ”rest-and-digest”-systemet. Det verkar troligt att domesticeringen agerat på dessa system för att minska rädsla och stress hos våra tamdjur. Den här avhandlingen studerar stressresponser hos höns. Dessa används i stor skala inom livsmedelsindustrin, slaktkycklingen för köttproduktion samt värphöns för äggproduktion. De har avlats hårt för snabb tillväxt och hög äggproduktion. En slaktkyckling ökar sin vikt till 50 gånger kläckvikten på sex veckor! Det sympatiska nervsystemet, samt stresshormoner, agerar för nedbrytande och energifrisläppande mekanismer, och det parasympatiska samt låg stress verkar för uppbyggande och energisparande mekanismer. Därför bör avel på låg stress och låg sympatisk aktivitet vara fördelaktigt för hög tillväxt. Experimenten i avhandlingen undersöker utvecklingen och mognaden av det autonoma nervsystemet hos kycklingar, domesticeringseffekter samt om stress tidigt i livet påverkar höns som vuxna. Vi fann att kycklingfoster redan vid 75 % av fosterutvecklingen har en funktionell parasympatisk stimulering på hjärtat och att dess inverkan ökar närmare kläckningen. Efter kläckning styrs hjärtat i huvudsak av, Domestication, the rapid man-driven evolution propelled by heavy selection for desirable traits, has changed a variety of species including the wolf, mouflon, auroch, wild boar and Red Junglefowl dramatically. Despite the polyphyletic origin of these species, they all demonstrate, after years of selection, features of surprising similarity that have been coined the domestic phenotype. The domesticated versions of these species are now commonly known as the dog, sheep, cattle, pig and broiler chicken. A common feature among domesticated animals is a reduced fearfulness towards humans, and plausibly higher stress tolerance and reduced stress response compared to their wild ancestors. The major physiological machinery controlling these behavioral modifications is the hypothalamic-pituitary-adrenal axis (HPA-axis) and the autonomic nervous system. The fight-and-flight response is mostly regulated by the sympathetic nervous system, both by increased adrenergic tone and by secretion of epinephrine from the adrenal medulla. These pathways are clear targets for domestication to reduce the stress response and fearfulness. In this thesis, the development and maturation of the autonomic nervous system, domestication effects in regard to stress, and developmental programming of early postnatal stress in chickens have been investigated. During development, chicken fetuses already had a functional cardiac cholinergic tone at 75% of development, and it progressively increased to hatch. Postnatally, heart rate was predominantly under adrenergic control, and at five weeks of age heart rate appears to reach maturity. Furthermore, we found a specific domestication effect in broiler chickens, demonstrated by a reduced cardiac frequency. Previous studies scanning for target genes explaining domestication in multiple chicken strains, in comparison to the Red Junglefowl, suggested an alteration in the gene coding for a receptor controlling epinephrine release from the adrenal medulla. Thi

Fetal development of autonomic cardiac control has been thoroughly investigated in chickens, but the maturation of the autonomic nervous system after hatching has gained little attention. At hatch the heart is under a feeble nervous control and there are indications suggesting a rapid maturation process during the first two weeks of postnatal life. We aimed to characterize the maturation by measuring heart rate at baseline and stressful conditions during the first 5 weeks of life in the Red Junglefowl and using autonomic antagonists to quantify the contribution of sympathetic and parasympathetic activity. We also compared the Red Junglefowl to the domestic broiler chickens at hatch to investigate the impact of domestication processes on heart rate regulation. During the first two postnatal weeks, baseline and stress heart rate progressively increased. After two weeks baseline heart rate decreased while heart rate during acute stress remained high. Adrenergic tone in Red Junglefowl increased as well early suggesting that the increase in heart rate was driven predominantly by adrenergic contributions. The adrenergic tone decreased by age after postnatal week one explaining the concomitant reduction in basal heart rate during this period. Broiler chickens possessed a strong cholinergic tone at hatch indicating that parasympathetic control has been favored perhaps due to heavy selection for somatic growth.

The domestication process in chickens has involved strong selection for productive traits. There is a broad understanding of phenotypic differences between domestic breeds and their ancestor, the Red Junglefowl (RJF), on fear related behaviors, genetic architecture, physiology and productive traits. Some of these characters can potentially be explained by changes in the activity of the autonomic nervous system. To address these questions we measured heart rate as a proxy for autonomic activity in the Red Junglefowl and compared it with two domestic strains, a broiler (BRO) (meat production) and a White Leghorn strain (HY) (egg production) at two and six weeks of age. Autonomic tones were pharmacologically manipulated in broilers to assess heart rate regulation during maturation. To investigate the dynamics of autonomic control animals were measured during baseline conditions and during acute stress. At two weeks of age baseline heart rate was high in all strains (RJF: 541.2±18.3, HY: 506.8±38.8, BRO: 456.0±22.3) and progressively decreased with age (RJF: 491.3±10.9, HY: 386.8±25.1, BRO:_296.8±26.9). BRO had a lower heart rate compared to RJF and HY, and the differences could not be explained by allometry alone. There was a domestication effect in BRO but not HY, which were in general more similar to RJF. These findings suggest that positive selection for somatic growth has changed heart rate regulation in broilers. During acute stress heart rate did not decrease with age in the same way than baseline values, which means that there is an increased scope for raising heart rate above baseline with age. At least in broilers the increased heart rate scope is due to a recruitment in adrenergic control in absence of a patent cholinergic tone.

Analysis of selective sweeps to pinpoint causative genomic regions involved in chicken domestication has revealed a strongselective sweep on chromosome 4 in layer chickens. The autoregulatory a-adrenergic receptor 2C (ADRA2C) gene is theclosest to the selective sweep and was proposed as an important gene in the domestication of layer chickens. The ADRA2Cpromoter region was also hypermethylated in comparison to the non-selected ancestor of all domesticated chicken breeds,the Red Junglefowl, further supporting its relevance. In mice the receptor is involved in the fight-or-flight response as itmodulates epinephrine release from the adrenals. To investigate the involvement of ADRA2C in chicken domestication, wemeasured gene expression in the adrenals and radiolabeled receptor ligand in three brain regions comparing the domesticWhite Leghorn strain with the wild ancestor Red Junglefowl. In adrenals ADRA2C was twofold greater expressed than therelated receptor gene ADRA2A, indicating that ADRA2C is the predominant modulator of epinephrine release but no straindifferences were measured. In hypothalamus and amygdala, regions associated with the stress response, and in striatum,receptor binding pIC50 values ranged between 8.1–8.4, and the level was not influenced by the genotyped allele. Becausechicken strains differ in morphology, physiology and behavior, differences attributed to a single gene may be lost in thenoise caused by the heterogeneous genetic background. Therefore an F10 advanced intercross strain between WhiteLeghorn and Red Junglefowl was used to investigate effects of ADRA2C alleles on fear related behaviors and fecundity. Wedid not find compelling genotype effects in open field, tonic immobility, aerial predator, associative learning or fecundity.Therefore we conclude that ADRA2C is probably not involved in the domestication of the stress response in chicken, and thestrong selective sweep is probably caused by selection of some unknown genetic element in the

Stress during early life can profoundly influence an individual’s phenotype. Effects can manifest in the short-term as well as later in life and even in subsequent generations. Transgenerational effects of stress are potentially mediated via modulation of the hypothalamic-pituitary-adrenal axis (HPA) as well as epigenetic mechanisms causing heritable changes in gene expression. To investigate these pathways we subjected domestic chicks (Gallus gallus) to intermittent social isolation, food restriction, and temperature stress for the first three weeks of life. The early life stress resulted in a dampened corticosterone response to restraint stress in the parents and male offspring. Stress-specific genes, such as early growth response 1 (EGR1) and corticotropin releasing hormone receptor 1 (CRHR1), were upregulated when chicks were tested in the context of restraint stress, but not under baseline conditions. Treatment differences in gene expression were also correlated across generations which indicate transgenerational epigenetic inheritance, possibly mediated by differences in maternal yolk estradiol and testosterone. In an associative learning test early stressed birds made more correct choices suggesting a higher coping ability in stressful situations. This study is the first to show transgenerational effects of early life stress in a precocial species by combining behavioural, endocrinological, and transcriptomic measurements., funding agencies|Swedish Research Council||Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning