Internal constraints on energy processing and their consequences: an integrative study of behaviour, ornaments and digestive health in greenfinches
Date
2022-07-06
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Abstract
Evolutsioonilise ökoloogia üks peamisi eesmärke on mõista, millest tulenevad isenditevahelised erinevused ning kuidas need mõjutavad sigimisedukust ja ellujäämist. Toitainete omastamine, energia tootmine mitokondrites ja energiavarude mobiliseerimine mõjutavad organismi sisemist energiakäitlust. Looma energiavajadus varieerub sõltuvalt kellaajast, aastaajast (nt migratsioon, paljunemine) ja keskkonnatingimustest, seega on oluline tagada, et energia tootmine vastaks vajadusele. Doktoritöö eesmärgiks oli uurida organismi sisemisi piiranguid energiakäitlusele ning piirangute mõju ellujäämisele, käitumisele ja sugulise valiku signaalidele rohevindil. Sooleparasiidid võivad vähendada toitainete imendumist seedesüsteemis. Esmakordselt kasutati seedefektiivsuse hindamiseks lindudelsteatokriti meetodit, mis on laia kasutuspotentsiaaliga ökoloogilistes uuringutes. Steatokriti meetod on lihtne, odav ja mitteinvasiivne ning võimaldab hinnata rasvade hulka väljaheidetes. Organismi energiavahetuse ning stressivastuse reguleerimisel mängivad olulist rolli hormoonid. Lindude peamise glükokortikoidhormooni kortikosterooni (KORT) tase oli keskmiselt 20% madalam laboris kasvanud sulgedes kui looduses kasvanutes. Isenditel kel oli kõrgem sulgede KORT tase looduses oli see kõrgem ka laboris. Kuna KORT seostus ka ellujäämise ja käitumisega, võib KORT peegeldada energiavajaduste varieeruvust isendite vahel. Kollane ja punane karotenoidsetel pigmentidel põhinev sule- või nahavärvus on paljudel loomadel sugulise valiku tunnus. Rohevintide kollasemad suled ei olnud seotud mitte ainult toitainete imendumisega seedesüsteemis, vaid ka parema võimega karotenoide muundada või sulgedesse ladustada. Toidust omastatud karotenoidide modifitseerimine toimub arvatavalt mitokondris ning karotenoidsed signaalid võivad seega signaliseerida isendi võimekust energiat toota. Samuti on võimalik, et mikrobioomi toodetud ained võivad mitokondrite tööd mõjutades mõjutada karotenoidseid tunnuseid. Kokkuvõttes selgus, et energiakäitluse ning ellujäämist ja paljunemisedukust mõjutavate tunnuste üheaegne uurimine aitab paremini mõista isenditevaheliste erinevuste põhjuseid.
Explaining the reasons why individuals differ in their performance is a central question in evolutionary and ecological research. Ability to absorb nutrients from food, produce energy in the mitochondria and energy mobilisation pose major internal constraints to energy processing. Energetic needs can vastly differ depending on the time of the day, season, individual’s life history stage and environmental conditions. Thus, organism's energy demands should be matched with energy output. The main goals of this thesis were to study the internal constraints to energy processing and its impact on survival, behaviour and production of sexually selected ornaments. Parasitic infections can reduce nutrient absorption in the digestive system. In this thesis, the application of the steatocrit method for birds was described for the first time. The steatocrit method enables to asess digestive effieciency nonivasivly and has wide potential for the use in ecological studies. Glucocorticoid hormones are important regulators of energy metabolism and stress response. Levels of the predominant glucocorticoid in birds, corticosterone (CORT), were on average 20% lower in lab-grown feathers than in wild-grown feathers, and birds who deposited more CORT into the feathers in one situation did the same in another, despite vastly different environmental conditions. CORT was also related to survival and behaviour. Therefore, CORT could indicate variation of energy requirements between individuals. Red and yellow carotenoid based integument coloration is sexually selected signal in many animals. Yellower feathers in greenfinches were not only related to absorption of nutrients in the gut, but also to carotenoid modification and deposition into signals. Biotransformation of carotenoids supposedly takes place in mitochondria. Thus, carotenoid signals might indicate the individual's capacity to produce energy. It is also possible that the gut microbiome could affect carotenoid colouration via modulation of mitochondrial function. In conclusion, an integrative view that incorporates animals' energetic needs, internal constraints to energy processing, and traits related to survival and reproductive success can help to understand why individuals differ in their performance and fitness.
Explaining the reasons why individuals differ in their performance is a central question in evolutionary and ecological research. Ability to absorb nutrients from food, produce energy in the mitochondria and energy mobilisation pose major internal constraints to energy processing. Energetic needs can vastly differ depending on the time of the day, season, individual’s life history stage and environmental conditions. Thus, organism's energy demands should be matched with energy output. The main goals of this thesis were to study the internal constraints to energy processing and its impact on survival, behaviour and production of sexually selected ornaments. Parasitic infections can reduce nutrient absorption in the digestive system. In this thesis, the application of the steatocrit method for birds was described for the first time. The steatocrit method enables to asess digestive effieciency nonivasivly and has wide potential for the use in ecological studies. Glucocorticoid hormones are important regulators of energy metabolism and stress response. Levels of the predominant glucocorticoid in birds, corticosterone (CORT), were on average 20% lower in lab-grown feathers than in wild-grown feathers, and birds who deposited more CORT into the feathers in one situation did the same in another, despite vastly different environmental conditions. CORT was also related to survival and behaviour. Therefore, CORT could indicate variation of energy requirements between individuals. Red and yellow carotenoid based integument coloration is sexually selected signal in many animals. Yellower feathers in greenfinches were not only related to absorption of nutrients in the gut, but also to carotenoid modification and deposition into signals. Biotransformation of carotenoids supposedly takes place in mitochondria. Thus, carotenoid signals might indicate the individual's capacity to produce energy. It is also possible that the gut microbiome could affect carotenoid colouration via modulation of mitochondrial function. In conclusion, an integrative view that incorporates animals' energetic needs, internal constraints to energy processing, and traits related to survival and reproductive success can help to understand why individuals differ in their performance and fitness.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
evolutionary ecology, energia metabolism, birds, glucocorticoids, corticosterone, hormones