The clocks controlling the tide-associated rhythms of intertidal animals

Abstract

The living clock that governs tide-associated organismic rhythms has previously been assumed to have a fundamental period of approximately 12.4 h, an interval that reflects the average period of the ebb and flow of the tide. But, in 1986, marine chronobiologists began to accumulate laboratory results that could not be explained by the action of such a clock. Prime among these findings was the discovery that, occasionally, one of the two daily peaks in an organism's rhythm assumed a different period from its partner. Similar results have since been observed in a host of different organisms. These data led to the circalunidian-clock hypothesis that envisions two basic 24.8 h clocks, coupled together in antiphase, as the driving force for these rhythms. There is, however, only a slight difference (50 minutes) in running times between a solar-day clock with a period of approximately 24 h and a lunar-day clock with a period of approximately 24.8 h, both of which display "circa" periods that overlap. Here, I postulate that the two clocks are fundamentally one and the same. BioEssays 22:32-37, 2000.

Spawning time of two shallow-water brittle stars

“…Palmer 2000). Many investigators have suggested sperm limitation as an ultimate cause for species with external fertilization (e.g.…”

“…The 2 low tides each day may each entrain an endogenous clock of an intertidal organism, i.e. there are 2 tide-entrained endogenous clocks (see Palmer 2000).…”

“…Endogenous rhythms controlling the behavior of organisms, including spawning activities, are certainly likely adaptations to these fluctuations (e.g. Palmer 2000).…”

Preliminary evidences of circadian fan activity rhythm in <i>Sabella spallanzanii</i> (Gmelin, 1791) (Polychaeta: Sabellidae)

“…In invertebrates, weakness in the detected circadian regulation is due to the splitting of activity peaks into submultiple units when animals are transferred to the laboratory (e.g. Dowse and Palmer, 1990;Warman and Naylor, 1995;Palmer, 2000;. The animals showed a measurable fan activity rhythm in both photoperiod treatments.…”

Short-lived intertidal midge Pontomyia oceana have semilunar eclosion rhythm entrained by night light

“…Bünning & Müller 1962, Christy 1978, Saigusa & Hidaka 1978, Neumann 1981, Palmer 2000, Hsueh 2002, Lüning et al 2008, Oliveira et al 2009). For example, the reproductive activities of many marine species, such as corals (Harrison et al 1984), echinoderms (Kubota 2000, Morgan 2009), crustaceans (Morgan 1996), or fishes (Hsiao & Meier 1986, Susilo et al 2009) all exhibit lunar or semilunar cycles.…”