Noah. T. Ashley, professeur au département de Biologie, Western Kentucky University, présentera «Keeping time under the midnight sun: a case study in Arctic-breeding songbirds» le mardi 22 octobre 2024 à 12 h au J-480.

Résumé : Polar environments are characterized by distinct periods of continuous light or darkness during the summer and winter, respectively. Since the light/dark cycle serves as a primary Zeitgeber of circadian rhythms for most organisms, its seasonal absence in polar environments may alter time-keeping mechanisms in arctic-dwelling animals. During the polar summer, two closely-related species of arctic-breeding songbirds, Lapland longspurs (Calcarius lapponicus) and snow buntings (Plectrophenax nivalis) exhibit round-the-clock activity, except for a brief daily 4-h period of quiescence, where they putatively sleep. Captive studies in longspurs reveal that this activity rhythm is circadian, suggesting entrainment to an alternative Zeitgeber. Field studies in Utqiagvik, Alaska (71°N) indicate that manipulating activity (and sleep) using pharmacological drugs modafinil (a stimulant) and melatonin (a hypnotic) have contrasting effects upon these two species. Modafinil treatment reduced parental care in male longspurs, but there was no effect in snow buntings. There was no change in longspur nestling growth rates, but fledging occurred significantly later among modafinil-treated males, suggesting a fitness cost. In contrast, melatonin diminished parental care in male snow buntings, but not in longspurs. Snow buntings are cavity nesters and do not require the same level of vigilance when defending nests compared with ground-nesting longspurs. This life-history difference between the two species highlights the role of predation risk in regulating behavioral modifications to prolonged wakefulness in arctic-breeding songbirds.

La présentation sera en anglais et présentée en mode hybride, par Zoom.

Lien zoom :  Redirection vers le lien zoom de Midis des sciences naturelles du Département de biologie, chimie et géographie https://uqar.zoom.us/j/82760261244?pwd=51IyyVW0tYrMk69hIYahVfU1kiUkqb.1#success Code secret :  300215