title: Circatidal activity rhythm in the mangrove cricket Apteronemobius asahinai.
abstract: Mangrove forests are influenced by tidal flooding and ebbing for a period of approximately 12.4 hours (tidal cycle). Mangrove crickets (Apteronemobius asahinai) forage on mangrove forest floors only during low tide. Under constant darkness, most crickets showed a clear bimodal daily pattern in their locomotor activity for at least 24 days; the active phases of approximately 10 hours alternated with inactive phases of approximately 2 hours, which coincided with the time of high tide in the field. The free-running period was 12.56+/-0.13 hours (mean+/-s.d. n=11). This endogenous rhythm was not entrained by the subsequent 24 hours light-dark cycle, although it was suppressed in the photophase; the active phase in the scotophase continued from the active phase in the previous constant darkness, with no phase shift. The endogenous rhythm was assumed to be a circatidal rhythm. On the other hand, the activity under constant darkness subsequent to a light-dark cycle was more intense in the active phase continuing from the scotophase than from the photophase of the preceding light-dark cycle; this indicates the presence of circadian components. These results suggest that two clock systems are involved in controlling locomotor activity in mangrove crickets.
authors.affiliation: Faculty of Science, University of the Ryukyus, Nishihara-cho, Okinawa 903-0213, Japan. ayasatoh@sci.u-ryukyu.ac.jp
authors.forename: Aya
authors.initials: A
authors.lastname: Satoh
authors.forename: Eiji
authors.initials: E
authors.lastname: Yoshioka
authors.forename: Hideharu
authors.initials: H
authors.lastname: Numata
mesh_terms: D000204:Activity Cycles / Q000502:physiology*; D000818:Animals; D006135:Gryllidae / Q000502:physiology*; D007564:Japan; D008124:Locomotion / Q000502:physiology*; D013997:Time Factors; D014197:Trees; D014872:Water Movements; D053833:Wetlands