title: Diapause induction and clock mechanism in the cabbage beetle, Colaphellus bowringi (Coleoptera: Chrysomelidae).
abstract: Photoperiodic control of diapause induction was investigated in the short-day species, Colaphellus bowringi, which enters summer and winter diapause as adult in the soil. Photoperiodic responses at 25 and 28 degrees C revealed a critical night length between 10 and 12 h; night lengths > or =12 h prevented diapause, whereas night lengths <12 h induced summer diapause in different degree. Experiments using non-24-h light-dark cycles showed that the duration of scotophase played an essential role in the determination of diapause. Night-interruption experiments with T=24 h showed that diapause was effectively induced by a 2-h light pulse in most scotophases; whereas day-interruption experiments by a 2-h dark break had a little effect on the incidence of diapause. The experiments of alternating short-night cycles (LD 16:8) and long-night cycles (LD 12:12) during the sensitive larval period showed that the information of short nights as well as long nights could be accumulated. Nanda-Hamner experiments showed three declining peaks of diapause at 24 h circadian intervals. Bünsow experiments showed two very weak peaks for diapause induction, one being 8 h after lights-off, and another 8 h before lights-on, but it did not show peaks of diapause at a 24 h interval. These results suggest that the circadian oscillatory system constitutes a part of the photoperiodic clock of this beetle but plays a limited role in its photoperiodic time measurement.
authors.affiliation: Institute of Zoology, Chinese Academy of Science, Beijing 100080, China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Ge
authors.forename: Fangsen
authors.initials: F
authors.lastname: Xue
authors.forename: Lanshao
authors.initials: L
authors.lastname: You
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D001517:Coleoptera / Q000502:physiology*; D003624:Darkness; D007814:Larva / Q000502:physiology; D008027:Light; D008675:Metamorphosis, Biological / Q000502:physiology*; D017440:Photoperiod; D013696:Temperature