QUANTITATIVE TESTS OF A DUAL CIRCALUNIDIAN CLOCK MODEL FOR TIDAL RHYTHMICITY IN THE SAND BEACH ISOPOD CIROLANA COOKII

Abstract

In constant conditions (constant darkness [DD], 20°C), the sand beach isopod Cirolana cookii exhibits spontaneous rhythmic swimming activity with an average free-running period of 12.5h. The rhythms are seen as temporal adaptations to a complex intertidal environment. These results support a dual circalunidian clock model for tidal rhythms in which two components of the rhythm have characteristic periods and active phase lengths and are hypothesized to be controlled by separate circalunidian clocks. A quantitative model successfully simulates many of the properties of endogenous swimming rhythms of C. cookii, including free-running behavior, entrainment, and phase-response curves (PRCs). (Chronobiology International 17 (1), 29–41, 2000)

• Circalunidian clocks
• Cirolana cookii
• Entrainment
• Model
• Phase-response curve (PRC)
• Tidal rhythms