| extra-hypothalamic brain clocks in songbirds: photoperiodic state dependent clock gene oscillations in night-migratory blackheaded buntings, emberiza melanocephala. | the avian circadian pacemaker system is comprised of independent clocks in the retina, pineal and hypothalamus, as shown by daily and circadian oscillations of core clock genes (per2, cry1, bmal1 and clock) in several birds including migratory blackheaded buntings (emberiza melanocephala). this study investigated the extra-hypothalamic brain circadian clocks in blackheaded buntings, and measured per2, cry1, cry2, bmal1 and clock mrna expressions at 4h intervals over 24h beginning 1h after light- ... | 2017 | 28254568 |
| circadian timing in central and peripheral tissues in a migratory songbird: dependence on annual life-history states. | predictable seasonal change in photoperiod triggers a sequential change in the daily activity-rest pattern, adaptive for migration in several bird species. the night-migratory black-headed bunting (emberiza melanocephala) is day active under short photoperiods (8 h light:16 h dark, short day sensitive). under long photoperiods (16 h light:8 h dark), the buntings are initially day active (long day premigratory) but subsequently become intensely night active (long day migratory) and after few week ... | 2015 | 26103987 |
| nocturnal melatonin levels decode daily light environment and reflect seasonal states in night-migratory blackheaded bunting (emberiza melanocephala). | we proposed two perhaps overlapping hypotheses. hypothesis 1 examined whether daily light information was transduced by a change in the pattern of daily melatonin secretion. hypothesis 2 tested whether the melatonin amplitude peak was contingent upon seasonal states. to test these hypotheses, we performed three experiments on night migratory blackheaded buntings (emberiza melanocephala). the first two experiments measured plasma melatonin levels in buntings exposed to light-dark (ld) cycles, wit ... | 2015 | 25764497 |
| role of light wavelengths in synchronization of circadian physiology in songbirds. | this study investigated whether at identical duration and equal energy level birds presented with short (450nm; blue, b) and long (640nm; red, r) light wavelengths would differentially interpret them and exhibit wavelength-dependent circadian behavioral and physiological responses, despite the difference in their breeding latitudes. temperate migratory blackheaded buntings (emberiza melanocephala) and subtropical non-migratory indian weaverbirds (ploceus philippinus) initially entrained to 12h l ... | 2015 | 25536387 |
| annual life history-dependent gene expression in the hypothalamus and liver of a migratory songbird: insights into the molecular regulation of seasonal metabolism. | birds seasonally switch from one life history state (lhs) to another to maximize their fitness. accordingly, they exhibit distinct differences in their physiological and behavioral phenotypes between seasons. possible molecular mechanisms underlying changes through the seasons have scarcely been examined in migratory birds. the present study measured key genes suggested to be involved in the metabolic regulation of 4 photoperiodically induced seasonal lhss in a long-distance migratory songbird, ... | 2014 | 25252711 |
| light wavelength dependent circadian and seasonal responses in blackheaded bunting. | animals in the wild are exposed to daily variations in sun light, viz. duration, intensity and spectrum. photosensitive blackheaded buntings (emberiza melanocephala) were exposed to photoperiods differing in the length of light period, wavelengths and intensity. the effects of such light changes were measured on locomotor activity rhythm as well as seasonal responses like development of migratory restlessness: zugunruhe, body mass and gonadal growth. the results show that the buntings are differ ... | 2014 | 24851407 |
| photoperiodic induction of pre-migratory phenotype in a migratory songbird: identification of metabolic proteins in flight muscles. | migratory birds need to undergo physiological changes during their preparation for migration. the current study characterized those changes in photoperiodic migratory black-headed buntings (emberiza melanocephala), which initiate their northward spring migration in response to increasing day lengths. we measured differences in body mass, testis size and triglycerides levels in buntings between groups exposed to short (8 h light:16 h darkness, 8l:16d; sd) and long (16l:8d; ld) days, and identifie ... | 2014 | 24760598 |
| neural correlates of migration: activation of hypothalamic clock(s) in and out of migratory state in the blackheaded bunting (emberiza melanocephala). | many vertebrates distinguish between short and long day lengths using suprachiasmatic nuclei (scn). in birds particular, the mediobasal hypothalamus (mbh) is suggested to be involved in the timing of seasonal reproduction. this study investigated the response of scn and mbh to a single long day, and the role of mbh in induction of the migratory phenotype in night-migratory blackheaded buntings. | 2013 | 24204554 |
| food availability affects circadian clock-controlled activity and zugunruhe in the night migratory male blackheaded bunting (emberiza melanocephala). | this study investigated the functional linkage between food availability and activity behavior in the palaearctic indian night migratory blackheaded bunting (emberiza melanocephala) subjected to artificial light-dark (ld) cycles. two experiments were performed on photosensitive birds. in the first one, birds were exposed to short days (ld 10/14; experiment 1a), long days (ld 13/11; experiment 1b), or increasing daylengths (8 to 13 h light/d; experiment 1c) and presented with food either for the ... | 2012 | 22217097 |
| phase inversion of neural activity in the olfactory and visual systems of a night-migratory bird during migration. | olfactory and visual sensory mechanisms seem to play a critical role in migratory orientation and navigation. how these two mechanisms are functionally linked with other migratory processes is unknown. we investigated this, in relation to the profound behavioural shift that occurs during migration in the night-migratory blackheaded bunting (emberiza melanocephala). photosensitive unstimulated birds singly housed in activity cages were subjected to long days (ld 16/8). the activity of each bird w ... | 2011 | 21676040 |
| regulation of seasonality in the migratory male blackheaded bunting (emberiza melanocephala). | the present study was carried out on a palearctic-indian migratory species, the blackheaded bunting (emberiza melanocephala), to understand the importance of photoperiodism and circannual rhythms in determining seasonality in changes in body mass and testis size in birds. an initial experiment determined the effects of duration and intensity of light on photoperiodic induction. the birds were exposed to different photoperiods (hours of light:hours of darkness; 11.5l:12.5d, 12l:12d, 12.5l:11.5d a ... | 2006 | 15535466 |
| wavelength dependency of light-induced effects on photoperiodic clock in the migratory blackheaded bunting (emberiza melanocephala). | the effects of light wavelength on photoperiodic clock were determined in the migratory male blackheaded bunting (emberiza melanocephala). we constructed an action spectrum for photoperiodic induction (body fattening, gain in body mass, and gonadal recrudescence) by exposing birds for 4.5 weeks to 13 h light per day (l:d = 13:11 h) of white (control), blue (450 nm), or red (640 nm) color at irradiances ranging from 0.028 to 1.4wm(-2). the threshold light irradiance for photoinduction was about 1 ... | 2004 | 15332443 |
| the photoperiodic entrainment and induction of the circadian clock regulating seasonal responses in the migratory blackheaded bunting (emberiza melanocephala). | the properties of the circadian photoperiodic oscillator have been investigated in detail only in the japanese quail. while the study of the quail is clearly very important, one cannot simply assume that other species, especially passerines that seem to have a different circadian organization than quail, function the same way. the current set of experiments was conducted to understand the entrainment and photoinduction of the circadian photoperiodic oscillator in a passerine species, the blackhe ... | 2002 | 12405550 |
| the influence of light wavelength on reproductive photorefractoriness in migratory blackheaded bunting (emberiza melanocephala). | there are two effects of long day length on reproductive responses in birds, one is the photoinduction of gonadal growth and maturation and the other is the induction of gonadal regression and photorefractoriness. although it is likely that the same photoreceptors are involved in the photoinduction of gonadal growth and the onset and maintenance of photorefractoriness. and so the influence of wavelength should be similar, this has not been investigated. therefore, we investigated the influence o ... | 2006 | 11789885 |
| effects of duration and time of food availability on photoperiodic responses in the migratory male blackheaded bunting (emberiza melanocephala). | the effects of the duration and time of food availability on stimulation of the photoperiodic responses (fattening and gain in body mass, and growth and development of testes) were investigated in the migratory blackheaded bunting (emberiza melanocephala). two experiments were performed. experiment i examined the effects of a reduction in the duration of food supply in buntings that were subjected to long day lengths (16h:8h l:d) and received food ad libitum (group i) or for restricted durations ... | 2001 | 11683439 |
| photoperiodic induction of ovarian growth and plasma estradiol secretion in a migratory finch, emberiza melanocephala: involvement of circadian rhythm. | to demonstrate the involvement of circadian rhythm in photoperiodic time measurement, photosensitive female blackheaded buntings were kept under different photoperiodic schedules consisting of 6 h of main photophase coupled with scotophases of various durations. ovarian mass and circulating plasma estradiol concentration were found to be elevated in cycles of 6l:6d, 6l:36d, 6l:54d and in control 15l:9d groups. but cycles of 6l:18d, 6l:42d and 6l:66d did not stimulate ovarian growth or elevate ci ... | 2000 | 10866358 |
| involvement of threshold photoperiod in control of reproductive rhythmicity in migratory blackheaded bunting, emberiza melanocephala. | to explore the need for minimum threshold photoperiodicity in regulation of metabolic and reproductive activities of a migratory finch, various programmed light-dark (ld) schedules, such as p1 (3l/21d), p2 (6l/18d), p3 (9l/15d), p4 (12l/12d), p5 (15l/9d), p6 (18l/6d), p7 (21l/3d), and p8 (24l/0d), have been used on photosensitive female blackheaded buntings for 42 days. results indicate that the photoperiodic thresholds of 3 h, 6 h, and 9 h completely failed to have any response on buntings, whi ... | 1999 | 10023576 |
| involvement of circadian rhythm in response to ultrashort photoperiods in blackheaded bunting, emberiza melanocephala. | groups of photosensitive adult female blackheaded buntings were exposed to various ultrashort days photoperiodic regimes for 60 days in which a fixed 3 h photophase was coupled with dark phases in cycles of 22 to 32 hours duration. one group of buntings was kept in long days (15l:9d) as control. significant increase in ovarian weight and circulating plasma estradiol concentration was marked in the cycles of 30 h (3l:27d), and 32 h (3l:29d) photoperiodic schedules as well as in control group (15l ... | 1997 | 9847458 |
| the photoperiodic clock is blackheaded buntings (emberiza melanocephala) is mediated by a self-sustaining circadian system. | three experimental protocols were employed to clarify whether the circadian system is involved in photoperiodic time-measurement in the blackheaded bunting, emberiza melanocephala. in a single-pulse paradigm, one 8-h light pulse was delivered at different times to groups of birds across three days of constant darkness (dd). photoperiodic induction, as measured by a rise in plasma luteinizing hormone (lh), showed clear circadian rhythmicity. the second experiment examined the lh responses in bird ... | 1996 | 8965259 |
| plasma levels of luteinizing hormone in intact and castrated photosensitive blackheaded buntings (emberiza melanocephala) exposed to stimulatory and nonstimulatory photoperiods. | experiments were performed to investigate the effects of castration and/or photostimulation on plasma luteinizing hormone (lh) in photosensitive blackhead buntings. castration evoked a significant rise in plasma lh in birds held under 8 h light: 16 h darkness (8l:16d). on exposure to 18l:6d for 24 d, both the intact birds and the castrates exhibited a significant rise in plasma lh, although the change in lh levels in the castrates was approximately 8 times greater than in the intact birds. when ... | 1993 | 8363738 |
| carry-over effects of long and short photoperiods on body fattening and gonadal weight of blackheaded bunting (emberiza melanocephala). | a study was made of the carry-over effect of long photoperiods followed by short photoperiods ou the fattening and gonadal response in a photoperiodic migratory species, the blackheaded bunting (emberiza melanocephala). the effect was studied in photosensitive and then in photostimulated birds. two experiments were performed: experiment i with photosensitive males and experiment ii with photosensitive males exposed to 30 long photoperiods. in both of them, five groups were submitted to the follo ... | 1986 | 3739742 |
| the photoperiodic entrainment and induction of reproductive rhythms in male blackheaded buntings (emberiza melanocephala). | groups of photosensitive, unstimulated or stimulated, male blackheaded buntings were subjected to photoregimes of 15 hr of green light of three intensities and 9 hr of dark per day. in some groups green light was interrupted with 90 min of bright fluorescent light at different times in the subjective day. while gonads did not develop or regressed in some groups, birds in others behaved as if exposed to long daylengths. the results besides suggesting the involvement of endogenous circadian rhythm ... | 1986 | 3677199 |
| hypothalamic and liver transcriptome from two crucial life-history stages in a migratory songbird. | what is the central question of this study? what are the molecular underpinnings of the seasonal adaptation in a latitudinal migratory songbird? what is the main finding and its importance? we found changes in mrna levels after a photoperiod-induced alteration of seasonal state in a captive long-distance latitudinal avian migrant. the hypothalamus and liver transcriptomes revealed genes involved in the regulatory and functional pathways between non-migratory and migratory states. our results pro ... | 2018 | 29380464 |
| temporal expression of genes coding for aryl-alkamine-n-acetyltransferase and melatonin receptors in circadian clock tissues: circadian rhythm dependent role of melatonin in seasonal responses. | we investigated at the transcriptional level the role of daily rhythm in melatonin secretion in seasonal responses in the migratory blackheaded bunting (emberiza melanocephala), which when exposed to short (sp) and long (lp) photoperiods exhibits distinct seasonal life-history states (lhss). we reproduced the seasonal lhs by subjecting buntings to sp (8 h light: 16 h darkness, 8 l:16d), which maintained the nonmigratory/ nonbreeding phenotype, and to lp (16 l:8d), which induced the premigratory/ ... | 2019 | 31082443 |
| transcriptome-wide changes in testes reveal molecular differences in photoperiod-induced seasonal reproductive life-history states in migratory songbirds. | we investigated the molecular basis of seasonal testicular states in black-headed buntings (emberiza melanocephala), in which seasonal migrations limit reproduction to a narrow time-window during the year. we examined testicular gene expressions in buntings during short day-induced photosensitive nonreproductive state (sdse), and during long day-induced early (ldes) and late (ldls) gonadal maturation and regressed photorefractory (ldrf) seasonal states. using kallisto, we pseudoaligned the rna-s ... | 2019 | 31025439 |
| transcriptional signatures in liver reveal metabolic adaptations to seasons in migratory blackheaded buntings. | the molecular underpinnings of metabolic adaptation to seasons are poorly understood in long- distance migrants. we measured changes in physiology and performed de novo sequencing of rna extracted from liver samples collected at 4-h intervals over a period of 24 h from a long-distance avian migrant, the blackheaded bunting (emberiza melanocephala), during two states: photostimulated vernal migratory (m) state and photorefractory non-migratory (nm) state. the m state was differentiated from the n ... | 2018 | 30538637 |
| temporal expression of c-fos and genes coding for neuropeptides and enzymes of amino acid and amine neurotransmitter biosynthesis in retina, pineal and hypothalamus of a migratory songbird: evidence for circadian rhythm-dependent seasonal responses. | this study investigated whether, in photoperiodic songbirds, the circadian pacemaker system (cps) connects to the seasonal photoperiodic responses, by changes at transcriptional level in the level and 24-h rhythm of its constituent neurotransmitters. we used black-headed buntings (emberiza melanocephala), which exhibit distinct seasonal states in captivity under appropriate photoperiods and hence served as a useful model system. under short days, buntings remain in the photosensitive state (pse) ... | 2018 | 29273324 |