The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Geoffrey E. Hill - One of the best experts on this subject based on the ideXlab platform.
-
an experimental test of the role of structural blue and melanin based chestnut coloration in aggressive contests in male eastern bluebirds
Frontiers in Ecology and Evolution, 2014Co-Authors: Austi Mercadante, Geoffrey E. HillAbstract:Male eastern bluebirds (Sialia Sialis) have feathers with either structurally based blue coloration or melanin-based chestnut coloration, and they hold territories during the breeding season that they defend vigorously. We tested whether the melanin pigmentation or structural coloration of feathers serve as signals during intrasexual aggressive encounters by placing color-modified stuffed bluebirds in male territories. We recorded the time to attack and the intensity of attacks on each model, and we then compared the response to color-enhanced versus color-reduced models. Male bluebirds attacked models with brighter and more chromatic blue coloration significantly more often than they attacked models with darker and less chromatic blue coloration. In contrast, the darkness of the chestnut breast coloration did not have a significant effect on the rate at which models were attacked. We conclude that territorial male bluebirds perceive intruding males with brighter blue coloration as a greater threat than males with drabber blue coloration, presumably because blue coloration is a signal of fighting ability. In contrast, the chestnut coloration of breast feathers appears to be a signal of gender and sexual maturity and not a graded signal of social status.
-
Effect of feather abrasion on structural coloration in male eastern bluebirds Sialia Sialis
Journal of Avian Biology, 2011Co-Authors: Adrian Surmacki, Mark Liu, Austin Mercadante, Geoffrey E. HillAbstract:We used observations of male eastern bluebirds captured twice within a breeding season to test whether changes in structural coloration are related to feather abrasion. Between first and second broods, the UV chroma and brightness of feathers decreased, while hue shifted towards longer wavelengths. Observed changes were greatest for feathers on the head, least for feathers on the rump, and intermediate for feathers on the back. For head feathers, we found a significant correlation between reduction in barb length and UV chroma. Plumage coloration at first capture was correlated with change in UV chroma such that the most ornamented males tended to lose more coloration. Moreover, the magnitude of UV color change was positively related to the number of days between color measurements.To test whether these changes were caused by abrasive properties of the nesting sites, we randomly increased or decreased the abrasiveness of nesting-box entrances by attaching sand paper or smooth plastic tape. The type of box entrance had no signicant effect on either coloration or barb length change. Our results suggest that feather abrasion is a factor in the seasonal color changes of bluebirds.
-
do adult eastern bluebird sialia Sialis males recognize juvenile specific traits
Animal Behaviour, 2009Co-Authors: Russell A Ligon, Geoffrey E. HillAbstract:Juveniles of many avian species possess spotted or mottled plumage that is distinct from the plumage of adults. Such plumage has typically been assumed to aid in camouflaging vulnerable immature birds. Here, we propose that spotty plumage signals juvenile status, thereby decreasing aggression from territorial adults. We tested this hypothesis by measuring the aggressive responses of adult eastern bluebird males to different combinations of simultaneously presented taxidermic mounts. We found that territorial males attacked adult models significantly more than juvenile models, and that they attacked adult models with orange breasts (typical of adults) more frequently than they attacked adult models with spotty breasts (typical of juveniles). We found no difference in attack rates when models with white breasts (a novel trait) were presented with models possessing spotty breasts. These observations indicate that breast colour is a cue used by territorial adults when identifying conspecific intruders, but that adults do not recognize juvenile-specific plumage as such. Adults respond aggressively only to orange-breasted intruders.
-
Sex-specific costs of reproduction in Eastern Bluebirds Sialia Sialis.
The Ibis, 2008Co-Authors: Lynn Siefferman, Geoffrey E. HillAbstract:In species with bi-parental care, individuals must partition energy between parental effort and mating effort. Typically, female songbirds invest more than males in reproductive activities such as egg-laying and incubation, but males invest more in secondary sexual traits used in attracting mates. Animals that breed more than once within a season must also allocate time and energy between first and subsequent breeding attempts and between current and future breeding seasons. To investigate strategies of reproductive investment by males and females and the consequences of such strategies, we manipulated the size of broods of Eastern Bluebirds Sialia Sialis. Pairs with enlarged first broods were less likely to produce a second clutch or took longer to initiate one than pairs with reduced broods. After rearing enlarged broods, females were less likely than males to survive to the following year. Although plumage coloration is a sexually selected trait in Eastern Bluebirds that is influenced by nutritional stress, we did not detect an effect of brood-size manipulation on female coloration. Past research, however, demonstrates that, in males, plumage colour is negatively affected by increasing brood size. We suggest that there are sex-specific strategies of reproductive investment in Eastern Bluebirds, and that researchers should incorporate measures of residual reproductive value in studies of life-history evolution.
-
The effect of rearing environment on blue structural coloration of eastern bluebirds (Sialia Sialis)
Behavioral Ecology and Sociobiology, 2007Co-Authors: Lynn Siefferman, Geoffrey E. HillAbstract:We used a brood-size manipulation to test the effect of rearing environment on structural coloration of feathers grown by eastern bluebird ( Sialia Sialis ) nestlings. Ultraviolet (UV)-blue structural coloration has been shown to be sexually selected in this species. Our experimental design took advantage of the growth of UV-blue wing feathers in nestlings that are retained as part of the first nuptial plumage. We cross-fostered nestlings to create enlarged and reduced broods with the purpose of manipulating parental feeding rates and measured the effect on nestling growth and plumage coloration. Brood size influenced feeding rates to offspring, but the effect varied with season. In general, male nestlings reared in reduced broods were fed more often, weighed more, and displayed brighter structural plumage compared to nestlings reared in enlarged broods. Female nestlings appeared to experience less adverse affects of brood enlargement, and we did not detect an effect of brood-size manipulation on the plumage coloration of female nestlings. Measures of plumage coloration in both males and females, however, were correlated to hatching date and nestling mass during feather development. These data provide empirical evidence that environmental quality can influence the development of the blue structural coloration of feathers and that males may be more sensitive to environmental fluctuations than females.
Lynn Siefferman - One of the best experts on this subject based on the ideXlab platform.
-
interspecific competition influences fitness benefits of assortative mating for territorial aggression in eastern bluebirds sialia Sialis
PLOS ONE, 2014Co-Authors: Morgan R Harris, Lynn SieffermanAbstract:Territorial aggression influences fitness and, in monogamous pairs, the behavior of both individuals could impact reproductive success. Moreover, territorial aggression is particularly important in the context of interspecific competition. Tree swallows and eastern bluebirds are highly aggressive, secondary cavity-nesting birds that compete for limited nesting sites. We studied eastern bluebirds at a field site in the southern Appalachian Mountains that has been recently colonized (<40 yr) by tree swallows undergoing a natural range expansion. The field site is composed of distinct areas where bluebirds compete regularly with tree swallows and areas where there is little interaction between the two species. Once birds had settled, we measured how interspecific competition affects the relationship between assortative mating (paired individuals that behave similarly) and reproductive success in eastern bluebirds. We found a strong tendency toward assortative mating throughout the field site. In areas of high interspecific competition, pairs that behaved the most similarly and displayed either extremely aggressive or extremely non-aggressive phenotypes experienced higher reproductive success. Our data suggest that interspecific competition with tree swallows may select for bluebirds that express similar behavior to that of their mate. Furthermore, animal personality may be an important factor influencing the outcome of interactions between native and aggressive, invasive species.
-
Sex-specific costs of reproduction in Eastern Bluebirds Sialia Sialis.
The Ibis, 2008Co-Authors: Lynn Siefferman, Geoffrey E. HillAbstract:In species with bi-parental care, individuals must partition energy between parental effort and mating effort. Typically, female songbirds invest more than males in reproductive activities such as egg-laying and incubation, but males invest more in secondary sexual traits used in attracting mates. Animals that breed more than once within a season must also allocate time and energy between first and subsequent breeding attempts and between current and future breeding seasons. To investigate strategies of reproductive investment by males and females and the consequences of such strategies, we manipulated the size of broods of Eastern Bluebirds Sialia Sialis. Pairs with enlarged first broods were less likely to produce a second clutch or took longer to initiate one than pairs with reduced broods. After rearing enlarged broods, females were less likely than males to survive to the following year. Although plumage coloration is a sexually selected trait in Eastern Bluebirds that is influenced by nutritional stress, we did not detect an effect of brood-size manipulation on female coloration. Past research, however, demonstrates that, in males, plumage colour is negatively affected by increasing brood size. We suggest that there are sex-specific strategies of reproductive investment in Eastern Bluebirds, and that researchers should incorporate measures of residual reproductive value in studies of life-history evolution.
-
The effect of rearing environment on blue structural coloration of eastern bluebirds (Sialia Sialis)
Behavioral Ecology and Sociobiology, 2007Co-Authors: Lynn Siefferman, Geoffrey E. HillAbstract:We used a brood-size manipulation to test the effect of rearing environment on structural coloration of feathers grown by eastern bluebird ( Sialia Sialis ) nestlings. Ultraviolet (UV)-blue structural coloration has been shown to be sexually selected in this species. Our experimental design took advantage of the growth of UV-blue wing feathers in nestlings that are retained as part of the first nuptial plumage. We cross-fostered nestlings to create enlarged and reduced broods with the purpose of manipulating parental feeding rates and measured the effect on nestling growth and plumage coloration. Brood size influenced feeding rates to offspring, but the effect varied with season. In general, male nestlings reared in reduced broods were fed more often, weighed more, and displayed brighter structural plumage compared to nestlings reared in enlarged broods. Female nestlings appeared to experience less adverse affects of brood enlargement, and we did not detect an effect of brood-size manipulation on the plumage coloration of female nestlings. Measures of plumage coloration in both males and females, however, were correlated to hatching date and nestling mass during feather development. These data provide empirical evidence that environmental quality can influence the development of the blue structural coloration of feathers and that males may be more sensitive to environmental fluctuations than females.
-
bacteria as an agent for change in structural plumage color correlational and experimental evidence
The American Naturalist, 2007Co-Authors: Matthew D Shawkey, Lynn Siefferman, Geoffrey E. Hill, Shreekumar R Pillai, Sharon R RobertsAbstract:Recent studies have documented that a diverse assem- blage of bacteria is present on the feathers of wild birds and that uropygial oil affects these bacteria in diverse ways. These findings suggest that birds may regulate the microbial flora on their feathers. Birds may directly inhibit the growth of harmful microbes or promote the growth of other harmless microbes that competitively exclude them. If keratinolytic (i.e., feather-degrading) bacteria degrade col- ored feathers, then plumage coloration could reveal the ability of individual birds to regulate microbial flora. We used field- and lab- based methods to test whether male eastern bluebirds (Sialia Sialis) with brighter blue structural plumage coloration were better able to regulate their microbial flora than duller males. When we sampled bluebirds in the field, individuals with brighter color had higher bacterial loads than duller individuals. In the lab, we tested whether bacteria could directly alter feather color. We found that keratinolytic bacteria increased the brightness and purity, decreased the ultraviolet chroma, and did not affect the hue of structural color. This change in spectral properties of feathers may occur through degradation of the cortex and spongy layer of structurally colored barbs. These data suggest that bacteria can alter structural plumage color through degradation.
-
Egg coloration is correlated with female condition in eastern bluebirds (Sialia Sialis)
Behavioral Ecology and Sociobiology, 2006Co-Authors: Lynn Siefferman, Kristen J Navara, Geoffrey E. HillAbstract:Egg coloration has been hypothesized to reflect female condition. Because of the proposed physiological costs associated with deposition of biliverdin pigments and because of their conspicuousness, eggs with blue-green coloration may reliably convey information about female or brood quality. We tested the hypothesis that expression of blue-green coloration of eastern bluebird (Sialia Sialis) eggs positively correlates to female condition. First, we documented the incidence of egg color polymorphism within the population. We observed that 98% of females laid blue-green eggs while less than 2% laid white eggs and less than 1% laid pink eggs. In a subset of clutches, we used full spectrum reflectance spectrometry (300-700 nm) to compare eggshell coloration to measures of female condition. We found that the color of eggs within clutches was more similar than the color of eggs from different clutches, and that the blue-green eggs have spectral peaks that are consistent with the characteristic absorbance spectra of biliverdin pigmentation. Females in better body condition and older females laid more colorful eggs. Moreover, individual females laid more colorful eggs later in the laying sequence. Overall, these data indicate that egg coloration covaries with female condition, suggesting that egg coloration could function as a reliable signal of female quality or that egg coloration may allow females to recognize eggs laid by conspecific brood parasites.
Roseline Froissart - One of the best experts on this subject based on the ideXlab platform.
-
amino acids bearing aromatic or heteroaromatic substituents as a new class of ligands for the lysosomal sialic acid transporter sialin
Journal of Medicinal Chemistry, 2020Co-Authors: Lilian Dubois, Nicolas Pietrancosta, Alexandre Cabaye, Isabelle Fanget, Cecile Debacker, Pierreandre Gilormini, Patrick M Dansette, Julien Dairou, Christophe Biot, Roseline FroissartAbstract:Sialin, encoded by the SLC17A5 gene, is a lysosomal sialic acid transporter defective in Salla disease, a rare inherited leukodystrophy. It also enables metabolic incorporation of exogenous sialic ...
Frans W Verheijen - One of the best experts on this subject based on the ideXlab platform.
-
elevated csf n acetylaspartylglutamate in patients with free sialic acid storage diseases
Neurology, 2010Co-Authors: Fanny Mochel, Udo F H Engelke, Julie Barritault, B Yang, Nathan Mcneill, Jerry N Thompson, Adeline Vanderver, Nicole I Wolf, Michel A A P Willemsen, Frans W VerheijenAbstract:Mutations in the SLC17A5 gene encoding the lysosomal transporter sialin are associated with the free sialic acid storage diseases (SASD): Salla disease (or the Finnish type of sialuria), the more severe infantile free sialic acid storage disease (ISSD), and intermediate phenotypes with clinical findings of both Salla disease and ISSD.1 SASD are characterized by the abnormal retention of free sialic acid in the lysosome (Online Mendelian Inheritance in Man 604369 and 269920). Patients with SASD usually present with nystagmus, progressive cerebellar ataxia, spasticity, and severe psychomotor delay. These symptoms are associated with diffuse supratentorial hypomyelination, thin corpus callosum, and cortical and cerebellar atrophy. The increase of free sialic acid in urine has been considered the biochemical hallmark of the disease.1 However, we have recently reported that patients with SASD can present without sialuria.2 The mechanisms leading to hypomyelination in SASD remain largely unknown. Here, we report the increase of N- acetylaspartylglutamate (NAAG) in the CSF of patients with SASD, which may provide new insight into the pathophysiology of the disease.
-
a new gene encoding an anion transporter is mutated in sialic acid storage diseases
Nature Genetics, 1999Co-Authors: Frans W Verheijen, Elly Verbeek, Nina Aula, Cecile E M T Beerens, Adrie C Havelaar, Marijke Joosse, Leena Peltonen, Pertti Aula, H Galjaard, Peter J Van Der SpekAbstract:Sialic acid storage diseases (SASD, MIM 269920) are autosomal recessive neurodegenerative disorders that may present as a severe infantile form (ISSD) or a slowly progressive adult form, which is prevalent in Finland1,2 (Salla disease). The main symptoms are hypotonia, cerebellar ataxia and mental retardation; visceromegaly and coarse features are also present in infantile cases3. Progressive cerebellar atrophy and dysmyelination have been documented by magnetic resonance imaging (ref. 4). Enlarged lysosomes are seen on electron microscopic studies and patients excrete large amounts of free sialic acid in urine. A H+/anionic sugar symporter mechanism for sialic acid and glucuronic acid5 is impaired in lysosomal membranes from Salla and ISSD patients6. The locus for Salla disease was assigned to a region of approximately 200 kb on chromosome 6q14–q15 in a linkage study using Finnish families7,8. Salla disease and ISSD were further shown to be allelic disorders9. A physical map with P1 and PAC clones was constructed to cover the 200-kb area flanked by the loci D6S280 and D6S1622, providing the basis for precise physical positioning of the gene10. Here we describe a new gene, SLC17A5 (also known as AST), encoding a protein (sialin) with a predicted transport function that belongs to a family of anion/cation symporters (ACS). We found a homozygous SLC17A5 mutation (R39C) in five Finnish patients with Salla disease and six different SLC17A5 mutations in six ISSD patients of different ethnic origins. Our observations suggest that mutations in SLC17A5 are the primary cause of lysosomal sialic acid storage diseases.
Matthew D Shawkey - One of the best experts on this subject based on the ideXlab platform.
-
bacteria as an agent for change in structural plumage color correlational and experimental evidence
The American Naturalist, 2007Co-Authors: Matthew D Shawkey, Lynn Siefferman, Geoffrey E. Hill, Shreekumar R Pillai, Sharon R RobertsAbstract:Recent studies have documented that a diverse assem- blage of bacteria is present on the feathers of wild birds and that uropygial oil affects these bacteria in diverse ways. These findings suggest that birds may regulate the microbial flora on their feathers. Birds may directly inhibit the growth of harmful microbes or promote the growth of other harmless microbes that competitively exclude them. If keratinolytic (i.e., feather-degrading) bacteria degrade col- ored feathers, then plumage coloration could reveal the ability of individual birds to regulate microbial flora. We used field- and lab- based methods to test whether male eastern bluebirds (Sialia Sialis) with brighter blue structural plumage coloration were better able to regulate their microbial flora than duller males. When we sampled bluebirds in the field, individuals with brighter color had higher bacterial loads than duller individuals. In the lab, we tested whether bacteria could directly alter feather color. We found that keratinolytic bacteria increased the brightness and purity, decreased the ultraviolet chroma, and did not affect the hue of structural color. This change in spectral properties of feathers may occur through degradation of the cortex and spongy layer of structurally colored barbs. These data suggest that bacteria can alter structural plumage color through degradation.
-
mechanisms of evolutionary change in structural plumage coloration among bluebirds sialia spp
Journal of the Royal Society Interface, 2006Co-Authors: Matthew D Shawkey, Geoffrey E. Hill, Susa L Alenge, Sco L Johnso, Ambe J Keyse, Ly SieffermaAbstract:Combinations of microstructural and pigmentary components of barbs create the colour displays of feathers. It follows that evolutionary changes in colour displays must reflect changes in the underlying production mechanisms, but rarely have the mechanisms of feather colour evolution been studied. Among bluebirds in the genus Sialia, male rump colour varies among species from dark blue to light blue while breast colour varies from blue to rusty. We use spectrometry, transmission electron microscopy and Fourier analysis to identify the morphology responsible for these divergent colour displays. The morphology of blue rump barbs is similar among the three species, with an outer keratin cortex layer surrounding a medullary ‘spongy layer’ and a basal row of melanin granules. A spongy layer is also present in blue breast barbs of mountain bluebirds Sialia currucoides and in rusty breast barbs of western Sialia mexicana and eastern bluebirds Sialia Sialis. In blue barbs melanin is basal to the spongy layer, but is not present in the outer cortex or spongy layer, while in rusty barbs, melanin is present only in the cortex. The placement of melanin in the cortex masks expression of structural blue, creating a rusty display. Such shifts in microstructures and pigments may be widespread mechanisms for the evolutionary changes in the colours of feathers and other reflective structures across colourful organisms.
-
nanostructure predicts intraspecific variation in ultraviolet blue plumage colour
Proceedings of The Royal Society B: Biological Sciences, 2003Co-Authors: Matthew D Shawkey, Lynn Siefferman, Anne M Estes, Geoffrey E. HillAbstract:Evidence suggests that structural plumage colour can be an honest signal of individual quality, but the mechanisms responsible for the variation in expression of structural coloration within a species have not been identified. We used full-spectrum spectrometry and transmission electron microscopy to investigate the effect of variation in the nanostructure of the spongy layer on expression of structural ultraviolet (UV)-blue coloration in eastern bluebird (Sialia Sialis) feathers. Fourier analysis revealed that feather nanostructure was highly organized but did not accurately predict variation in hue. Within the spongy layer of feather barbs, the number of circular keratin rods significantly predicted UV-violet chroma, whereas the standard error of the diameter of these rods significantly predicted spectral saturation. These observations show that the precision of nanostructural arrangement determines some colour variation in feathers.
