title: Nocturnalism induced by scheduled feeding in diurnal Octodon degus.
abstract: Octodon degus, a mainly diurnal rodent, characterized by its ability to shift to a nocturnal locomotor pattern under laboratory conditions, was studied to determine whether restricted food access during the scotophase could induce nocturnalism. To address this question, wheel running activity, feeding, and body temperature rhythms were analyzed for diurnal degus housed with a wheel and subjected to either long (12 h) or short (2 h) food availability periods, in the latter case with random or scheduled food access times. The results show that allowing nocturnal feeding for 2 h, but not 12 h, can shift a previous diurnal phase preference for wheel running activity and body temperature to the scotophase, with random feeding being more effective than scheduled food availability. However, this behavioral inversion proved to be unstable, as the degus returned to the diurnal phase within only a few days after the restricted feeding was discontinued. In addition, the negative masking effect induced by light, which is characteristic of the degus' nocturnal chronotype, was not observed when the animals were forced to feed at night. Thus, neither long, short, random, nor scheduled food-availability during the scotophase was able to induce all the characteristics of the nocturnal chronotype in Octodon degus.
authors.affiliation: 1Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, Murcia, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Vivanco
authors.forename: Antonio
authors.initials: A
authors.lastname: López-Espinoza
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Madariaga
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Rol
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Madrid
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001683:Biological Clocks / Q000502:physiology; D001831:Body Temperature; D002940:Circadian Rhythm / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D005248:Feeding Methods; D008027:Light; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D046329:Octodon / Q000502:physiology*; D017440:Photoperiod