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- Isaksson, Caroline, 1976, et al.
(författare)
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Carotenoid diet and nestling provisioning in urban and rural great tits Parus major
- 2007
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857 .- 1600-048X. ; 38:5, s. 564-572
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Tidskriftsartikel (refereegranskat)abstract
- Considering the importance of dietary constraints for the widely held view of carotenoid pigmentation as an honest quality indicator, there is surprisingly little data on carotenoid availability in different natural diets or along environmental gradients. Here we investigate the carotenoid availability in the main diet of breeding great tits Parus major, living in urban and rural environments with known differences in carotenoid pigmentation. Carotenoid availability for nestling great tits was investigated in two respects: (1) quantity and quality of diet (i.e., caterpillar abundance and their carotenoid concentration), and (2) parental feeding frequency. First, caterpillars were generally more abundant in the urban environment and the four common Lepidoptera (i.e., caterpillars) genera studied were also heavier here. Second, as determined by HPLC analysis of the caterpillar genera, carotenoid concentration was significantly lower in the urban caterpillars. Furthermore, all except one of the caterpillar genera had higher lutein/zeaxanthin ratio in urban areas, which is in accordance with earlier studies of carotenoid composition in great tit yolk. Third, parental feeding frequency was about twice as high to urban broods compared to rural broods. This result may simply reflect the higher caterpillar abundance (shorter search time) in the urban environment. Poor food quality (low carotenoid concentration) seems therefore to be compensated by quantity in the urban environment. As a consequence the carotenoid availability seems to be similar for nestlings in the two environments.
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| 4. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Egg Yolk Carotenoids in Relation to Habitat and Reproductive Investment in the Great Tit Parus major
- 2008
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Ingår i: Physiological and Biochemical Zoolog. - : University of Chicago Press. - 1522-2152 .- 1537-5293. ; 81:1, s. 112-118
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Tidskriftsartikel (refereegranskat)abstract
- Maternal allocation of antioxidants to egg yolk has been shown to affect early embryonic development and nestling survival. In environments with high levels of anthropogenic pollution, antioxidants (such as carotenoids) are important to protect the body from elevated oxidative stress. Thus, female allocation of antioxidants to yolk may be traded off against self‐maintenance. Here we investigate maternal reproductive investment with respect to yolk carotenoid content and composition in relation to subsequent female condition and carotenoid status in urban and rural great tits Parus major. We found no differences between the urban and rural populations in total yolk carotenoids, egg mass, clutch size, hatching success, or female carotenoid status. Interestingly, however, rural eggs contained more zeaxanthin, a more potent antioxidant than lutein, which suggests that rural embryos have better antioxidant protection than urban embryos. Whether rural females actively transfer more zeaxanthin to the yolk or whether it passively reflects differences in dietary access or uptake needs to be further investigated. This highlights the importance of carotenoid identity and composition in future studies of carotenoid physiology, ecology, and signaling.
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| 5. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Oxidative stress does not influence carotenoid mobilization and plumage pigmentation.
- 2008
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Ingår i: Proceedings of the Royal Society London - Biological sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 275:1632, s. 309-14
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress has been suggested to create a link between 'good genes' and carotenoid coloration via an allocation conflict between external pigmentation and internal antioxidant functions. However, although carotenoid displays have been extensively investigated, there are no experimental tests of the antioxidant efficiency of carotenoids in vivo. We induced oxidative stress in a small passerine (the great tit, Parus major) under both carotenoid deprivation and supplementation, and investigated the effect on carotenoid mobilization (i.e. plasma) and allocation (i.e. deposition in feather incorporation and liver storage). We found no effects of the stressor on either mobilization or allocation of carotenoids. These results reject the previously suggested superior role of carotenoid's function as antioxidant in vivo with important implications for signal content and honesty.
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| 6. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Oxidative stress physiology in relation to life history traits of a free-living vertebrate: the spotted snow skink, Niveoscincus ocellatus.
- 2011
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Ingår i: Integrative Zoology. - 1749-4877. ; 6:2, s. 140-149
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Tidskriftsartikel (refereegranskat)abstract
- Recent research suggests that oxidative stress, via its links to metabolism and senescence, is a key mechanism linking life history traits such as fecundity and growth with survival; however, this has rarely been put under empirical scrutiny within free-living populations. Using a wild population of live-bearing skinks, we explored how plasma antioxidant activity (OXY), reactive oxidative metabolites (ROM), and the estimated oxidative stress index are associated with female and male life history. We found that male skinks have a significantly higher ROM and estimated oxidative stress index than female skinks, but this was not accompanied by a sex difference in mortality. Both sexes showed a non-linear association between OXY and age, indicating that the oldest and youngest individuals had the lowest OXY. Interestingly, female skinks with high OXY showed a decreased probability of survival to the following season. However, we found no significant associations between female reproductive investment (litter size or litter mass) or parturition date (i.e. metabolism) and oxidative status. Combined, our results offer mixed support for a role of oxidative stress in mediating life history traits and suggest that future studies need to explore oxidative stress during vitellogenesis in addition to using an intra-individual approach to understand the cost of reproduction and patterns of aging.
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| 7. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Parental effects on carotenoid-based plumage coloration in nestling great tits, Parus major
- 2006
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 60:4, s. 556-562
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Tidskriftsartikel (refereegranskat)abstract
- Carotenoid pigments have attracted much interest in behavioural and evolutionary ecology because of their dual function in immune physiology and as color signals. In vertebrates, carotenoids must ultimately be obtained from the diet, and the mechanisms and magnitude of this environmental dependence are central for understanding carotenoid signal functions and evolution. In the present cross-fostering experiment with great tits Parus major, we investigate pre- and postnatal parental effects (egg yolk carotenoids, parental coloration) on nestling size and carotenoid coloration, using HPLC analysis of egg yolk carotenoids, and a reflectance-based measure of 'chroma' that reflects the plumage pigment concentration. Both rearing environment and origin influenced offspring size and plumage chroma. Maternal allocation of carotenoids to eggs had a weak positive effect on nestling plumage chroma, whereas we found no prenatal maternal effects (egg size or yolk carotenoid concentration) on size. Nestling plumage chroma was also significantly predicted by the chroma of the rearing father, but not by the color of the rearing mother or either of the original (genetical) parents. Thus, both prenatal maternal effects and postnatal paternal effects influence the carotenoid-based plumage coloration of nestling great tits. Future studies will reveal if parental effects have long-term consequences for plumage development and associated fitness components.
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| 8. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Plasma Glutathione and Carotenoid Coloration as Potential Biomarkers of Environmental Stress in Great Tits
- 2005
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Ingår i: EcoHealth. - : Springer Science and Business Media LLC. - 1612-9202 .- 1612-9210. ; 2, s. 138-146
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Tidskriftsartikel (refereegranskat)abstract
- Measures of oxidative stress in animals may be useful biomarkers of environmental stressors, such as anthropogenic pollution. In birds, studies of oxidative stress have focused on dietary antioxidants, primarily carotenoids, which are interesting due to their multiple physiological and pigmentary functions but therefore also unspecifically related to oxidative stress. A useful complementary biomarker may be the glutathione system, commonly used in human medicine, but rarely applied to wild, terrestrial vertebrates. In this study of urban versus rural adult and nestling great tits Parus major, we investigated both the carotenoid-based yellow plumage (by reflectance spectrometry) and the plasma levels of glutathione, the latter measured as total glutathione (tGSH) and as the ratio between oxidized and reduced glutathione (GSSG:GSH), respectively. We found that urban adults had higher current oxidative stress (GSSG:GSH) and paler yellow plumage compared to rural adults, suggesting elevated stress in the urban environment. Total glutathione levels (tGSH), however, which may indicate long-term up-regulation of the GSH reservoir, did not differ between the environments. Nestlings did not show any consistent pattern between environments in either tGSH or GSSG:GSH and, among individuals, glutathione levels were uncorrelated with carotenoid coloration. The results thus suggest some population-level correspondence between the two stress biomarkers in adult birds, but more work is obviously needed to understand how the two antioxidant systems interact in different individuals and in response to different environmental disturbances.
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| 9. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Sex and age differences in reflectance and biochemistry of carotenoid-based colour variation in the great tit Parus major
- 2008
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 95:4, s. 758-765
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Tidskriftsartikel (refereegranskat)abstract
- The plumage coloration in great tits (Parus major) is the subject of much behavioural and ecophysiological research, yet there is a lack of analyses of the natural colour variation and its mechanisms. We used reflectance spectrometry and high-performance liquid chromatography to explore individual, sexual and age-related variation in carotenoid coloration and pigmentation, paramount to the often presumed, but rarely substantiated, costs and 'honesty' of carotenoid displays. In adults, we found that sex was the strongest predictor of 'brightness' (higher in males) and of 'hue' (longer wavelength in females). There was no sex difference in 'carotenoid chroma' or carotenoid content of feathers which also was unrelated to adult age (1 or 2+ years) and condition. Similar patterns were revealed for nestlings. Regarding the biochemical 'signal content', 'carotenoid chroma', but not 'hue', was significantly related to the carotenoid content (lutein and zeaxanthin) of feathers. These results refute the previously assumed exaggeration of carotenoid pigmentation in male great tits, and question the condition-dependence of carotenoid coloration in this species. However, the sexual dimorphism in total reflectance or 'brightness', most likely due to melanins rather than carotenoids, may have implications for signalling or other adaptive explanations that need to be explored.
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| 10. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Sexual, seasonal, and environmental variation in plasma carotenoids in great tits, Parus major
- 2007
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 92:3, s. 521-527
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Tidskriftsartikel (refereegranskat)abstract
- In many birds, carotenoids have dual functions as irreversible plumage pigments and as physiologically essential vitamins and antioxidants. They must be obtained through the diet and may therefore be a limiting resource, a constraint that is likely to vary with factors such as sex, habitat, and time of year. In the present study, we investigated signs of carotenoid limitation in great tits, Parus major, in relation to sex, season, year, and within an urban versus a rural habitat. The two main carotenoids, lutein and zeaxanthin, were analysed by high-performance liquid chromatography in the plasma and in the yellow carotenoid-based breast feathers. We found that plasma carotenoid concentrations were significantly influenced by sex, season, and year, but not by urban versus rural habitat. At moult, plasma concentration was positively correlated with feather pigmentation, independent of body condition and sex. During the breeding season, however, circulating carotenoid concentrations were negatively related to the feather pigmentation (i.e. from previous autumn moult). We suggest that great tits are carotenoid deprived before leaf emergence, and that carotenoid utilization and limitations are sex-specific, but that there are neither any obvious honesty-maintaining costs of pigmentation, nor any fitness consequences of the colour variation.
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