title: Role of light wavelengths in synchronization of circadian physiology in songbirds.
abstract: 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 light:12h darkness (12L:12D; L=0.33μM/m(2)/s, D=0μM/m(2)/s) in two groups of each, groups 1 and 2, were subjected to constant light (LL, 0.33μM/m(2)/s), which rendered them arrhythmic in the activity behavior. They were then exposed for about two weeks each to 12B:12R and 12R:12B (group 1) or 12R:12B and 12B:12R (group 2) at 0.33μM/m(2)/s light energy level. Blue and red light periods were interpreted as the day and night, respectively, with activity and no-activity in non-migratory weaverbirds or activity and intense activity (Zugunruhe, migratory night restlessness) in the migratory buntings. Consistent with this, plasma melatonin levels under B:R, not R:B, light cycle were low and high in blue and red light periods, respectively. A similar diurnal pattern was absent in the cortisol levels, however. These results show an important role of light wavelengths in synchronization of the circadian clock governed behavior and physiology to the photoperiodic environment, and suggest that photoperiodic timing might be a conserved physiological adaptation in many more birds, regardless of the difference in breeding latitudes, than has been generally envisaged.
authors.affiliation: DST-IRHPA Centre for Excellence in Biological Rhythms Research, Department of Zoology, University of Lucknow, Lucknow 226 007, India.
authors.forename: G
authors.initials: G
authors.lastname: Yadav
authors.affiliation: DST-IRHPA Centre for Excellence in Biological Rhythms Research, Department of Zoology, University of Lucknow, Lucknow 226 007, India.
authors.forename: S
authors.initials: S
authors.lastname: Malik
authors.affiliation: DST-IRHPA Centre for Excellence in Biological Rhythms Research, Department of Zoology, University of Lucknow, Lucknow 226 007, India.
authors.forename: S
authors.initials: S
authors.lastname: Rani
authors.affiliation: DST-IRHPA Centre for Excellence in Biological Rhythms Research, Department of Zoology, University of Delhi, Delhi 110 007, India. Electronic address: drvkumar11@yahoo.com.
authors.forename: V
authors.initials: V
authors.lastname: Kumar
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology / Q000528:radiation effects*; D004797:Enzyme-Linked Immunosorbent Assay; D006854:Hydrocortisone / Q000097:blood; D008027:Light; D008550:Melatonin / Q000097:blood; D009043:Motor Activity / Q000528:radiation effects*; D017440:Photoperiod; D020308:Songbirds / Q000097:blood / Q000502:physiology*; D013045:Species Specificity; D013223:Statistics as Topic
chemical_list: D008550:Melatonin; D006854:Hydrocortisone
keywords: Activity; Bunting; Cortisol; Light wavelength; Melatonin; Weaver bird