UV-induced feather color change reflects its porphyrin content.

Pigmentary coloration is widespread in animals. Its evolutionary and ecological features are often attributed to the property of predominant pigments; therefore, most research has focused on predominant pigments such as carotenoids in carotenoid-based coloration. However, coloration results from predominant pigments and many other minority pigments, and the importance of the latter is overlooked. Here, we focused on porphyrin, an "uncommon" pigment found in bird feathers, and investigated its importance in the context of feather color changes in the barn swallow Hirundo rustica. We found that the "pheomelanin-based coloration" of the barn swallow faded after the irradiation of UV light, and this effect was particularly strong in the feathers of young swallows (nestlings and fledglings, here). We also found that it is not the predominant pigment, pheomelanin, but protoporphyrin IX pigment that showed the same pattern of depigmentation after the irradiation of UV light, particularly in the feathers of young swallows. In fact, the abovementioned age-dependent feather color change was statistically explained by the amount of porphyrin in the feathers. The current study demonstrates that a minority pigment, porphyrin, explains within-season dynamic color change, an ecological feature of feather coloration. The porphyrin-mediated rapid color change would benefit young birds, in which feather coloration affects the parental food allocation during a few weeks before independence, but not later. Future studies should not ignore these minor but essential pigments and their evolutionary and ecological functions.

Opposing population trends of fork-tailed swallows and reddish-coloured swallows in our changing world.

Sexual selection can in theory lead to positive and negative effect on population-level fitness and hence population increase/decline in our changing world, but the empirical evidence is scarce. Using a phylogenetic comparative approach, we examined whether and how different sexually selected ornaments affect recent population trends and extinction risk in swallows (Aves: Hirundininae). We found that population trends decreased with increasing depth of male tails, that is a well-known sexually selected trait, and increased with increasing score of reddish plumage coloration, another sexually selected ornament. Similar contrasting patterns were observed for extinction risk. These findings indicate ornament-specific population trends and extinction risk, perhaps due to the differential costs and benefits of ornamentation. Previous studies have mostly focused on the overall effects of sexual selection by combining different kinds of traits, presumed to be sexually selected. However, as predicted by theory, sexual selection would not be a process with the same universal effect on population dynamics as we found here. Divergent ecological consequences would occur through minor differences in sexual selection, which should not be dismissed in future studies.

Fork tails evolved differently in swallows and swifts.

Whether sexual or viability selection drives the evolution of ornamental traits is often unclear because current function does not clarify evolutionary history, particularly when the ornamentation is a modified version of the functional traits. Here, using a phylogenetic comparative approach, we studied how deeply forked tails-a classic example of sexually selected traits that might also be a mechanical device for enhancing aerodynamic ability-evolved in two groups of aerial foragers, swallows (family: Hirundinidae) and swifts (family: Apodidae). Although apparent fork depth, the target of sexual selection, increases with increasing outermost tail feather length, fork depth can also increase with decreasing central tail feather length, which impairs the lift generated by the tail. Thus, we predicted that sexual selection, but not viability selection, should favour the evolution of short central tail feathers in species with deeply forked tails, particularly in swifts, which are less reliant on the lift generated by their tail than in swallows. We found support for these predictions because central tail feather length decreased with increasing tail fork depth, particularly in swifts. Instead, the increase in outermost tail feather length per unit tail fork depth was higher in swallows than in swifts, indicating that a similar sexual ornamentation (i.e. forked tails) differently evolved in these two aerial insectivores perhaps due to the differential cost of ornamentation. We also found support for an optical illusion that changes the relative importance of central and outermost tail feather length in sexual selection.

Small, Variable Sperm in a Barn Swallow Population with Low Extra-Pair Paternity.

Sperm competition can theoretically affect sperm morphology; however, it remains unclear whether and how sperm morphology tracks the intensity of sperm competition in each population. The barn swallow Hirundo rustica is a model species used in the study of sexual selection, and exhibits considerable variation in extra-pair paternity (percentage extra-pair young, ca. 3-30%) among populations. In the Joetsu population of the barn swallow, extra-pair paternity is virtually absent (< 3%), providing a rare opportunity to study sperm morphology under limited sperm competition, and to compare it with those reported in populations with frequent extra-pair paternity (>15%). We found that head, midpiece, and total sperm length were significantly shorter in the Joetsu population than in populations with frequent extra-pair paternity. Moreover, the variability in total sperm length, measured as the coefficient of variation in the Joetsu population, was twice as high as that of populations with frequent extra-pair paternity. These results are consistent with a positive, directional, and stabilizing effect of sperm competition on sperm morphology. Together with previous studies in populations with frequent extra-pair paternity, the current study provides one of few sets of evidence to show a link between the intensity of sperm competition and the mean and variance of sperm morphology within a wild bird species.

Eumelanin levels in rufous feathers explain plasma testosterone levels and survival in swallows.

Pigment-based plumage coloration and its physiological properties have attracted many researchers to explain the evolution of such ornamental traits. These studies, however, assume the functional importance of the predominant pigment while ignoring that of other minor pigments, and few studies have focused on the composition of these pigments. Using the pheomelanin-based plumage in two swallow species, we studied the allocation of two pigments (the predominant pigment, pheomelanin, and the minor pigment, eumelanin) in relation to physiological properties and viability in populations under a natural and sexual selection. This is indispensable for studying the evolution of pheomelanin-based plumage coloration. Pheomelanin and eumelanin share the same pathway only during their initial stages of development, which can be a key to unravel the functional importance of pigment allocation and thus of plumage coloration. Using the barn swallow, Hirundo rustica, a migratory species, we found that plasma testosterone levels increased with increasing the proportion of eumelanin pigments compared with pheomelanin pigments, but not with the amount of pheomelanin pigments, during the mating period. In the Pacific swallow Hirundo tahitica, a nonmigratory congener, we found that, during severe winter weathers, survivors had a proportionally smaller amount of eumelanin pigments compared with pheomelanin pigments than that in nonsurvivors, but no detectable difference was found in the pheomelanin pigmentation itself. These results indicated that a minor pigment, eumelanin, matters at least in some physiological measures and viability. Because the major pigment, pheomelanin, has its own physiological properties, a combination of major and minor pigments provides multiple information to the signal receivers, potentially enhancing the signaling function of pheomelanic coloration and its diversification across habitats.

Males with More Pheomelanin Have a Lower Oxidative Balance in Asian Barn Swallows (Hirundo rustica gutturalis).

Pheomelanin-based plumage pigmentation has been suggested to be an honest signal of individual quality to conspecifics. It has been hypothesized that oxidative stress is an important agent linking pheomelanic pigmentation to individual quality. Using the Asian barn swallow Hirundo rustica gutturalis, a wild passerine, we tested whether the pheomelanin pigmentation in the red throat patch of adult males, a sexually selected trait, is associated with the ratio between reduced and oxidized glutathione (RGSH/GSSG) as an indicator of current oxidative balance during the early breeding season. We found that males with a higher pheomelanin concentration in their throat feathers had a significantly lower RGSH/GSSG ratio (i.e., higher oxidative stress), but exhibited a better body condition, measured as residual body mass on body size, compared to males with a lower pheomelanin concentration. The total GSH level was not significantly related to the pheomelanin concentration. These findings suggest a negative association between the red pheomelanin pigmentation and oxidative balance during mating and reproductive efforts, which might be mitigated by high-quality males. Further research is needed to understand its actual damage and mitigation mechanism.

Sexually dimorphic swallows have higher extinction risk.

The effect of sexual selection on extinction risk remains unclear. In theory, sexual selection can lead to both increase and decrease extinction probability depending on the ecology of the study system. Thus, combining different groups might obscure patterns that can be found in groups that share similar ecological features. Using phylogenetic comparative analysis, we studied sexual plumage dimorphism in relation to the perceived risk of extinction in hirundines (subfamily: Hirundininae), in which all species are socially monogamous aerial foragers. Among the 72 species studied, five species are facing a perceived threat of extinction. Species with sexually dimorphic plumage had a higher risk of extinction than did species with sexually monomorphic plumage. Likewise, when focusing solely on tail ornamentation, species that exhibit a sexual dimorphism in tail length had a higher risk of extinction than did other species. In Hirundininae, which are affected a great deal by severe weather, sexual selection and the resultant sexual dimorphism would increase extinction risk.

Plasma Testosterone Levels Increase with Expression of Male Ornaments During Mating, but not Incubation, in Japanese Barn Swallows.

Recent experimental studies involving the manipulation of sexual traits have demonstrated that sexual trait expression feeds back to testosterone levels, perhaps via social interactions, reinforcing the linkage between sexual trait expression and testosterone levels during the mating period. However, information on this reinforcement under the natural variation of sexual traits remains limited. Using Japanese barn swallows, Hirundo rustica gutturalis, in which extra-pair paternity is quite rare (< 3%), we studied the relationship between plasma testosterone level and a male sexual trait, throat patch size, during the mating and incubation periods. Given the importance of social interaction, we predicted that this relationship should be intense during the mating period, but not the incubation period, due to reduced social interaction during the latter. We found low plasma testosterone levels during the incubation period compared with those in the mating period, and plasma testosterone levels were significantly positively related to throat patch area during the mating period, but not the incubation period. Similar relationships were found in another sexual trait, the size of white tail spots. During the incubation period, body condition, instead of male sexual trait expression, was negatively related to plasma testosterone level, indicating that an intrinsic link, rather than reinforcement, is important during this period. These relationships are consistent with the hypothesis that social interaction reinforces the relationship between sexual traits and plasma testosterone levels. The current study provides evidence for a highly variable relationship between testosterone and ornamentation across breeding periods in the natural variation of sexual traits.

Evolution of tail fork depth in genus Hirundo.

A classic example of a sexually selected trait, the deep fork tail of the barn swallow Hirundo rustica is now claimed to have evolved and be maintained mainly via aerodynamic advantage rather than sexually selected advantage. However, this aerodynamic advantage hypothesis does not clarify which flight habits select for/against deep fork tails, causing diversity of tail fork depth in hirundines. Here, by focusing on the genus Hirundo, we investigated whether the large variation in tail fork depth could be explained by the differential flight habits. Using a phylogenetic comparative approach, we found that migrant species had deeper fork tails, but less colorful plumage, than the other species, indicating that migration favors a specific trait, deep fork tails. At the same time, tail fork depth but not plumage coloration decreased with increasing bill size - a proxy of prey size, suggesting that foraging on larger prey items favors shallower fork tails. Variation of tail fork depth in the genus Hirundo may be explained by differential flight habits, even without assuming sexual selection.

Therapeutic effect of hybrid training of voluntary and electrical muscle contractions in middle-aged obese women with nonalcoholic fatty liver disease: a pilot trial.

BACKGROUND: Exercise training is an effective therapy for nonalcoholic fatty liver disease (NAFLD). Hybrid training (HYB) of voluntary and electrical muscle contractions was developed to prevent disuse atrophy during space flight. HYB can be applied to obtain a strength training effect accompanying articular movement. In this pilot study, we aimed to investigate the therapeutic efficacy of HYB in NAFLD. METHODS: A total of 15 middle-aged obese women with NAFLD who had no improvement in serum alanine aminotransferase levels and/or liver fat deposition after 12 weeks of lifestyle counseling participated in an HYB program. HYB of the quadriceps and hamstrings was conducted for 20 minutes twice a week for 24 weeks. RESULTS: NAFLD patients showed attenuated intramyocellular lipid levels in the quadriceps after the HYB intervention (-15.5%). Levels of leptin (-17.4%), tumor necrosis factor-α (-23.2%), and interleukin-6 (-30.5%) were also decreased after the intervention. HYB led to a significant body weight reduction (-4.7%), which in turn was associated with a significant decrease in serum alanine aminotransferase (-35.8%), gamma-glutamyl transpeptidase (-21.6%), ferritin (-16.0%), oxidative stress (-17.8%) levels, and insulin resistance values (-2.7%). CONCLUSION: In NAFLD, HYB exerts an antiobesity effect and attenuates liver dysfunction and insulin resistance in association with an increase in muscle strength and a decrease in ectopic muscle fat. Therefore, HYB has great potential as a new type of exercise therapy for liver disease in patients with NAFLD.

Acceleration training for managing nonalcoholic fatty liver disease: a pilot study.

BACKGROUND: While aerobic training is generally recommended as therapeutic exercise in guidelines, the effectiveness of resistance training has recently been reported in the management of nonalcoholic fatty liver disease (NAFLD). Acceleration training (AT) is a new training method that provides a physical stimulation effect on skeletal muscles by increasing gravitational acceleration with vibration. AT has recently been indicated as a component of medicine. In this study, we evaluated the effectiveness of AT in the management of NAFLD in obese subjects. METHODS: A total of 18 obese patients with NAFLD who had no improvement in liver function test abnormalities and/or steatosis grade after 12 weeks of lifestyle counseling were enrolled in an AT program. These patients attended a 20-minute session of AT twice a week for 12 consecutive weeks. RESULTS: During the AT program, the NAFLD patients showed a modest increase in the strength (+12.6%) and cross-sectional area (+3.1%) of the quadriceps, coupled with a significant reduction in intramyocellular lipids (-26.4%). Notably, they showed a modest reduction in body weight (-1.9%), abdominal visceral fat area (-3.4%), and hepatic fat content (-8.7%), coupled with a significant reduction in levels of aminotransferase (-15.7%), γ-glutamyltransferase (-14.4%), leptin (-9.7%), interleukin-6 (-26.8%), and tumor necrosis factor-α (-17.9%), and a significant increase of adiponectin (+8.7%). On a health-related quality of life survey, the patients showed an improvement in physical functioning (+17.3%), physical role (+9.7%), general health (+22.1), and social functioning (+6.0%). CONCLUSION: AT reduced hepatic and intramyocellular fat contents and ameliorated liver function test abnormalities in obese patients with NAFLD, which was coupled with improved physical function and body adiposity. AT is clinically beneficial for the management of NAFLD.

Differential female access to males with large throat patches in the Asian barn swallow Hirundo rustica gutturalis.

Intersexual selection results from several processes, such as differential allocation and differential access, in addition to mating skews by mate choice. These processes can contribute to the evolution, maintenance, and geographic differentiation of male ornamentation, although the importance of these processes in male ornamentation remains poorly understood. The Asian barn swallow Hirundo rustica gutturalis is a socially monogamous songbird that exhibits biparental care and has red throat patches twice as large as those of the nominate H. r. rustica. Our previous study showed that females paired to males with large throat patches had higher reproductive output in terms of multiple broods, although the underlying process resulting in selection for a large throat patch remained unclear. In the present study, we analyzed differential female access to males with large throat patches in H. r. gutturalis. We observed that males with large throat patches acquired older and fatter females, independent of male age class. In addition, females that mated to males with large throat patches returned to the study site more compared with others, indicating the high viability of these females, supporting differential access but not differential allocation. No other measures of male ornaments (i.e., tail length, white tail spots, or throat color value) were linked to female qualities. As these female qualities were associated with female reproductive output, males with large throat patches would obtain reproductive advantages, as found in our previous study. The current findings suggest the importance of differential access for the evolution of a large throat patch in this subspecies.

Assessing muscle vasodilation using near-infrared spectroscopy in cardiac patients.

BACKGROUND: In patients with chronic heart failure, an inadequate increase in muscle blood flow resulting from impaired vasodilation plays a key role in their exercise intolerance. However, no non-invasive methods to assess muscle vasodilation during dynamic exercise were available. We investigated whether the changes in tissue hemoglobin and myoglobin content (total-Hb + Mb) determined by non-invasive measurement using near-infrared spectroscopy (NIRS) reflect vessel conductance of working muscle during exercise. METHODS AND RESULTS: Sixteen patients (10 patients with normal cardiac systolic function, 6 with cardiac dysfunction) performed incremental bicycle exercise testing. Total-Hb + Mb from the right vastus lateralis muscle was monitored using NIRS. Leg blood flow (LBF) in the right femoral vein was measured using a thermodilution technique every 30-60 s. Leg vessel conductance was calculated as LBF/mean arterial pressure at each time of the measurement. In all cases except 1, the levels of total-Hb + Mb showed significant correlation with the leg vessel conductance (r=0.792 to 0.980). Intra-subject reproducibility of the NIRS measurement was also confirmed in 6 patients. CONCLUSIONS: Total-Hb + Mb from NIRS reflected muscle vasodilation during sub-maximal dynamic exercise in patients with and without cardiac dysfunction, indicating that NIRS provides a valuable method to assess the working muscle vasodilation.