title: Bimodality in the nocturnal behavior of the giant land snail, Achatina fulica.
abstract: Entrainment and phase advance of the circadian locomotor rhythms in the giant land snail, Achatina fulica, were examined by a running wheel method. The mean activity patterns in three light-dark (LD) cycles (LD 14: 10, LD12: 12, LD 10: 14) were characterized by bimodal peaks, namely an initial major peak 1-2 hr after the onset of darkness and a later peak after nearly 6 hr. The activity rhythms were able to follow a 6 hr phase advance shift of the LD 14: 10 cycle with transients, accompanied by shortening or splitting of the activity time. When splitting occurred, the initial component showed phase advancement in the dark and phased to lights-off whereas the later one phased to lights-on, with post-dawn activity being suppressed by light. These results suggest the presence of multioscillator circadian organization which shows monophasic or biphasic entrainment under the LD cycles.
authors: Department of Physiology, Tohoku University School of Medicine, Sendai.
authors: T
authors: T
authors: Ogasawara
authors: K
authors: K
authors: Tasaki
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003624:Darkness; D008027:Light; D009043:Motor Activity; D012908:Snails / Q000502:physiology*