The clocks controlling the tide-associated rhythms of intertidal animals

Unravelling the Ecological Significance of Endogenous Rhythms in Intertidal Crabs

“…The appearance of new periods in translocated crabs (Barnwell, 1968;Morgan, 1996a, b) is readily compatible with the dual-circalunidian oscillator hypothesis. Additional support for circalunidian clocks controlling tidal rhythms has appeared in the literature (Williams, 1998;Palmer, 2000;Mehta & Lewis, 2000).…”

Tidal, Daily, and Lunar‐Day Activity Cycles in the Marine PolychaeteNereis virens

“…Biological rhythmicity in marine organisms has been widely documented (for a general review, see Palmer, 2000) and should be of particular interest to chronobiologists, as it demonstrates the lability of the biological clock, which, in the marine environment, is capable of entraining non-diel periodicities. As in terrestrial organisms, it is adaptively important for marine organisms to be able to anticipate future cyclic events.…”

“…Depending on the reproductive state of the animals, a population cohort may then undergo a synchronized spawning event in the early spring, which will only occur, depending on geographical locality, at a fixed time of day and tide, and only on one or two days a year, after which the animals die (Bentley et al, 2001). Such traits require a highly evolved time-sense, and it is probable that long-period timing in N. virens is dependent on the existence of short-period rhythmic capabilities such as those represented by the putative circatidal and circadian (Reid & Naylor, 1989) and circalunidian (Palmer, 1989(Palmer, , 1997a(Palmer, , 1997b(Palmer, , 2000 clocks.…”

Circatidal rhythm and the veiled clockwork

“…This hypothesis applies to species such as mud crabs (Macrophthalmus hirtipes and Helice crassa), in which two circatidal activity peaks run independently with different periods under constant conditions (termed free-running) [10]. The circalunidian clock is assumed to be a circadian clock or its variation that is tidally-adapted, because the freerunning period of the circalunidian clock is similar to that of the circadian clock [13]. In the circadian clock hypothesis, a single tidally-adapted circadian clock generates two active or inactive phases per day (Figure 2-B).…”