The rhythmic activity of biological organisms, plant or animal, is closely associated with gravitational tides generated by the orbital mechanics of the Sun-Earth-Moon system. This truth, to some extent neglected by scientific research, has now been highlighted by a new study conducted by Cristiano de Mello Gallep, at Unicamp (State University of Campinas), and Daniel Robert, at the University of Bristol (United Kingdom). An article about it was published in the Journal of Experimental Botany.
“All matter, inert or alive, on Earth experiences the effects of the gravitational forces of the Sun and Moon, expressed in the form of tides. The periodic oscillations have two daily cycles and are modulated monthly and annually by the movements of these two stars. context that all organisms present on the planet have evolved. What we tried to show in the article was that the gravitational tides constitute a perceptible and powerful force that shaped and shapes the rhythmic activities of these organisms”, says Gallep to the FAPESP Agency.
The study was carried out in the form of an extensive literature review and also a meta-analysis, interrogating data from three cases previously published, but whose gravitational causality had not been properly explored: the locomotor activity of isopods, small shelled crustaceans whose appearance on Earth dates back to at least 300 million years; reproductive effort in coral colonies; and the modulation of sunflower shoot growth, inferred by autoluminescence. In the latter case, the researchers added to the literature data results obtained in their own investigations.
“The data show that, in the absence of other rhythmic influences, such as lighting and temperature, the local gravitational tide is sufficient to organize the cyclical behavior of these organisms. This evidence therefore questions the validity of so-called free-run experiments, in which several Environmental factors are controlled, but gravitational oscillations are not taken into account. These oscillations continue to exist and possibly modulate the behavior of living beings”, argues Gallep.
Among the rhythmic patterns exhibited by organisms, the most studied and known are the circadian cycles, which vary with the succession of day and night and are closely linked to the alternation of light and dark on Earth. There are, however, rhythmic fluctuations that remain when the lighting factor is isolated under laboratory conditions. And the contribution of other environmental variables has been investigated and demonstrated, even if their effects are comparatively very weak. The present study considered, among other evidence, the persistence of tidal cycles in the behavior patterns of coastal organisms, such as crustaceans, removed from their habitats.
“These animals modulate their behavior in tune with the descent and rise of the tides, in a cycle of approximately 12.4 hours, resulting from the lunisolar dynamics, even when taken to laboratories with stable and controlled aquatic conditions. This pattern is maintained for several years. days, coinciding with the tidal time of the place where the organisms were collected,” says Gallep.
Although the combined gravitational effect of the Sun and Moon is only a millionth of Earth’s gravity, it is sufficient not only to cause the large tidal fluctuations in oceans, rivers and lakes, but also to move tectonic plates. And the Large Hadron Collider (LHC), of the European Organization for Nuclear Research (CERN), with a circumference of 27 km, moves up to one millimeter vertically due to this gravitational fluctuation — so much so that the calculations of the experiments there performed need to be adjusted to compensate for this factor.
Gallep initially noticed such peridiocities in his experiments with self-luminescence resulting from seed germination, carried out in Limeira, in the State of São Paulo. “I found that changes in the collected signal appeared every 12 hours or 24 hours, however, in a different way for each germination test. Looking for support in the literature, I found studies that indicated a possible correlation with the gravitational tide. We explored this fact in tests with different types of seeds, and we also aggregated results obtained in collaborators’ laboratories in Prague, Czech Republic, Leiden, Netherlands, and Hamamatsu, Japan.”
The gravitational effect doesn’t just affect simpler organisms. It was found that humans, isolated from light, tend to establish a cyclical fluctuation of 24.4 to 24.8 hours, in line with the lunar cycle. The phenomenon, observed in people who spend a lot of time inside caves, conditions the alternating periods of wakefulness and sleep, feeding times and other metabolic functions.
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