It has been found that the intraday dynamics of body temperature in small mammal and bird species on the adjacent day are similar. Therefore, by focusing on the body temperature dynamics of the previous day, it is possible to predict with a high degree of accuracy the periods of increase and decrease in body temperature for the current day. This phenomenon was observed when animals were kept under natural illumination and under artificial illumination when the phase of the intrinsic circadian rhythm shifted by 1-2 h every day. When analyzing this phenomenon in birds, it has been shown that the best match for body temperature dynamics occurs when comparing adjacent days based on sidereal days (a period of 23 h and 56 min). Over time, after several days, the daily patterns of body temperature fluctuation take on a completely different form and frequency. These facts suggest a connection between ultradian rhythms and the rotation of the Earth around its axis, and consequently, the position of animals on the surface of the planet relative to space objects.

A positive correlation was found between the level of global seismic activity and dynamics of cortisol concentration in blood serum of male rabbits (r=0.33, p=0.01) and Campbell’s dwarf hamsters (r=0.38, p=0.04). For a small group of healthy volunteers (n=5), we also found a positive correlation between cortisol levels and the number of major earthquakes, excluding aftershocks (r=0.36, p=0.009) and a negative correlation with IL-18 levels (r=-0.28, p=0.04). The body response to earthquakes is not delayed, and the numerous aftershocks do not seem to affect the biological indicators under study. These facts showed that the earthquakes themselves do not affect the cortisol level via the changes of the environmental parameters. In contrast, the underlying biotropic factor is an unknown trigger responsible for an increase in the number of potent earthquakes. Evidently, it is important to take into account the level of global seismicity as a marker of this trigger provoking the rise of glucocorticoid hormones.

Association was assessed between the data harvested by a long-baseline laser interference deformograph and the dynamics of body temperature (BT) in hamsters deprived of natural daily light-darkness changes. The power spectral data revealed the positive correlation between simultaneous time series of hamster BT and the Earth’s crust deformation (ECD). The superposed epoch analysis established an association between abrupt upstrokes of hamster BT and ECD increments. Thus, the direct relationships between BT dynamics (reflecting predominance of sympathetic part of autonomic nervous system) and ECD (according to long-baseline laser interference deformography) were established. The study observed synchronization of the free-running circadian rhythm of hamster BT with the tidal stress in Earth’s lithosphere. Further studies are needed to find the physical factor underlying the revealed relationships.

The study monitored the long-term body temperature (BT) oscillations of C57BL/6 mice and outbred starlings ( Sturnus vulgaris ) to compare them with fluctuation in decay rate of radioactive natural 40 K isotope. The spectrum analysis revealed simultaneous changes of the predominant periods in BT spectra of the animals and those in fluctuation in 40 K decay rate. A positive correlation was established between BT dynamics and fluctuation in decay rate. The superposed epoch analysis revealed predominant coincidence of the moments of BT and fluctuation in 40 K decay rate. The novel data indicate association between BT ultradian rhythms with quasirhythmic variations of fluctuation in 40 K decay rate.

The multi-day dynamics of the intensity of 40K decay fluctuations was compared with motor activity of laboratory mice, circulating cortisol in rabbits, and proliferation of fibroblast-like cultured cells L-929. A positive correlation was established between the intensity of decay fluctuations on the one hand, and total daily motor activity in mice and plasma cortisol level in rabbits, on the other hand. In addition, a negative correlation was observed between 40K decay fluctuations and proliferative activity of the cultured cells. Interestingly, these close correlations were observed not only against the background 4-day rhythm, but also in the time when any rhythmicity was absent. Thus, the intensity of 40K decay fluctuations is an indicator of a biotropic environmental factor that augments motor activity and raises the circulating cortisol in animals and down-regulates proliferation of cultured cells.

We studied the influence of epiphysectomy and administration of melatonin to epiphysectomized outbred white rats on the level and daily dynamics of damage to the genetic material of developing male germ cells. Epiphysectomy leads to an increase in the level of damage in the DNA structure and the disappearance of the circadian rhythm of the activity of repair enzyme PARP-1 and the apoptosis-inducing enzyme caspase-3. The administration of melatonin to animals after epiphysectomy reduces the level of DNA damage, restores the circadian rhythm of activity of PARP-1 and caspase-3. These fundings suggest that melatonin can indirectly protect DNA of maturing male gametes.

In passerine birds, the coloration of plumage is associated with two groups of pigments (melanins and carotenoids). The physiological bases of the appearance of melanin- and carotenoid-based coloration are fundamentally different, and these types of coloration reflect different characteristics of an individual. It is considered that the expressiveness of melanin-based coloration primarily depends on genetic factors, while the expressiveness of carotenoid-based coloration depends on the state and health of an individual at the moment. Therefore, the individual variability of these two types of coloration should be independent of each other. We studied the coloration of the second (from the distal edge) rectrix in 109 greenfinch males of two age cohorts (one year old and aged two or more years). The relationship between the level of aggressiveness of different birds and their color characteristics was also considered. The feathers we are interested in are two-color; their distal part is black (or blackish), while the proximal part (basis) is yellow. The black color is caused by melanins, while the yellow one by carotenoids. We demonstrated that the saturation of yellow carotenoid-based coloration in greenfinch males has a significant and negative relationship with the length of the black (melanin) spot on the same rectrix (the relationship of the saturation of the yellow coloration with the length of the yellow field is, respectively, positive). Thus, the individual variability of melanin- and carotenoid-based coloration in our case is parallel. This indicates that the roles of these groups of pigments as indicators (markers) of the quality and state of an individual were not as fundamentally different as is commonly thought. However, there are definitely differences in this regard between melanin- and carotenoid-based coloration: the black melanin-based coloration in the greenfinch is associated with aggressiveness, while the yellow carotenoid-based one is not.

Abstract—The dynamics of the concentration of testosterone and thyroxine in the blood serum of nine white-breasted hedgehog males (Erinaceus roumanicus) were studied during the year with a natural seasonal cycle (in winter, hedgehogs were in a state of hibernation in an unheated room; in summer they were in a 100 m2 enclosure under conditions close to natural). Blood samples were taken every 12 days. The hormone concentrations in blood serum were determined using enzyme immunoassays. Both testosterone and thyroxine concentrations showed evident seasonal variations. The maximum level of testosterone was observed immediately after spring awakening of the animals. Two weeks following the awakening the testosterone concentrations were decreased to a medium level, with this level being maintained until the end of June. From August to early December, the hormone level was found in trace amounts. A statistically significant increase in testosterone concentrations started from mid-December. The dynamics of testosterone concentrations were followed by the thyroxine ones, but with a delay of 12–24 days. Two short periods were revealed: the first was against the background of decreasing testosterone, when the concentration of thyroid hormones increased 12–20 days after spring awakening during the transition from an active search for a sexual partner to an increase in food-gathering behavior and a moderate weight gain; the second occurred in early July at the end of the reproductive season and the transition to active fat deposition.

Body temperature rhythms of C57Bl/6 laboratory mice and common greenfinches (Chloris chloris) and feeding periods of common starlings (Sturnus vulgaris) were compared with the intensity of fluctuations in 40К radioactive decay. Body temperature changes in greenfinches and mice were found to positively correlate with the intensity of fluctuations in 40K radioactive decay. Superposed epoch analysis showed that an increase in mouse body temperature, which reflects the start of the active phase in the sleep–wake cycle, and food intake in starlings coincide with an increase in the intensity of 40K radioactive decay. Thus, animal activity in the ultradian range of periods may be related to external quasi-rhythmic physical influences, rather than being determined only by endogenous processes. Given the extremely low dose of natural 40К exposure, a factor responsible for radioactivity fluctuations may act as a biotropic factor.

Simultaneous observations of radioactivity fluctuations from the natural isotope 40K were carried out in Moscow and Ulyanovsk. It was found that the changes in the counting rate from sources in these geographical points were not simultaneous, but were synchronized according to local solar time. Based on this observation and considering that radioactivity fluctuations correlated with body temperature rhythms, a method for short-term prediction of ultradian rhythms of animal activity has been developed and confirmed. An analysis of the consistency of the dynamics of the intensity of decay fluctuations and daily growth rates of an L-929 cell culture was also carried out. It was found that the highest correlation coefficient was recorded when the indicator of proliferative activity of the culture was compared with the intensity of decay fluctuations taken over the previous day. Thus, based on data on fluctuations in the radioactive decay of 40K, which are an indicator of the biotropic factor of the environment, it is possible to make short-term forecasts of ultradian and infradian biological rhythms.

In a long-term (8 months) study, we examined the degree of synchronization of ultradian body temperature oscillations of two isolated groups of mice kept under constant dim illumination. In most cases, the periods of increased activity accompanied by rapid elevation of body temperature coincided in these groups of mice, but in some days, no significant synchronization between the examined parameters was observed. Analysis of the effects of environmental factors on the degree of synchronization of ultradian rhythms in mice revealed association of this parameter with the dynamics of atmospheric pressure (AtmP) and to a lesser extent with the vertical component of interplanetary magnetic field Bz. The loss in synchronicity of ultradian rhythms of mouse activity occurred after a rapid drop of AtmP or during pronounced negative Bz. Therefore, these factors can be viewed as desynchronizers of the biological ultradian rhythms.

In passerine birds, pigment-based feather coloration comes exclusively from carotenoids and melanins. Carotenoids and melanins are fundamentally different classes of biochromes because they are produced through different physiological mechanisms and have frequently been hypothesized to carry out different functions. The expression of melanin ornaments has been shown to be under genetic control, while carotenoid-based traits have traditionally been viewed as reliable indicators of actual body conditions and health. Therefore, melanin- and carotenoid-based traits should be generally unrelated to each other. Here, we considered the coloration of the 2nd rectrices (R2) of 109 Greenfinch males, both subadults and adults. We then linked this trait to aggressiveness studied in captivity. R2 have a melanin-based black tip and a carotenoid-based yellow proximal part. We found that the length of the black tip was related negatively to the saturation of the yellow color. Thus, contrary to expectations, melanin- and carotenoid-based traits were found related to each other. Therefore, melanin-based ornaments may be related to individual conditions and quality somewhat similar to carotenoid-based traits. However, the two differ, because a melanin-based black feather tip was linked to aggression and dominance in Greenfinch males, while the saturation of a carotenoid-based yellow coloration was not.

The study compared the daily mean intensity of one-minute-step fluctuations in intensity of the secondary cosmic rays reflected by neutron count rate and dynamics of body temperature, motor activity, as well as concentration of glucocorticoid hormones in birds and rodents. A positive correlation was established between body temperature oscillations and neutron count rate fluctuations. A similar correlation was observed between physical parameter (neutron count rate), on the one hand, and daily mean motor activity and concentration of glucocorticoid hormones in the animals. The periods and phases of these processes presented in synchronous time series coincided. The facts of simultaneous variations or disturbances of the periods in dynamics of biological and physical parameters attest to their relationships. The study concluded that the infradian rhythms with the periods of 3-5 days depend on some external environmental factor related to fluctuations in intensity of secondary cosmic rays.

The study collated oscillations of body temperature of С57BL/6 mice and Roborovski hamsters (Phodopus roborovskii) in the period range of 100-240 min and fluctuations of the secondary cosmic rays reflected by neutron count rate of a neutron monitor at the Earth’s surface. Cross-correlation of body temperature and neutron count rate data revealed their strong association only for simultaneous measurements. Collation of the phase of neutron count rate fluctuations with maxima of body temperature oscillations revealed the coincidence of the phases of both processes. There was a temporary connection between the periods of body temperature elevation and neutron count rate rise. Thus, not only the spectral parameters of biological and physical processes, but also their phases coincided, which corroborates the hypothesis on stimulating effect of increasing neutron count rate on activity of the animals.

The synchronization of mice motor activity, which reflects the activity–rest cycle, with variations in the X component of the geomagnetic field vector (BOXX) in the range of fluctuations from 10 to 120 min has been studied. The percentage of pixels on the video recording that changed their intensity within 10 s is used as an indicator of motor activity. The experiment was performed simultaneously on 16 males of the C57BL/6 line in October 2019 in Moscow. The mice were kept single in a plastic box (t = 22–26°С) under an artificial 12-h light regime and free access to water and food. The degree of similarity of the rhythm of biological and BOXX indicators is analyzed for each animal by evaluating the degree of similarity of their Fourier spectra for each 12-h day and night intervals. An analysis of the time series averaged over the group showed that almost all harmonics in the interval of 50–120 min correspond to equal harmonics of the BOXX. The cross-correlation function of two series has a statistically significant absolute maximum with a zero time lag between the series. On average, 18% of individual segments show statistically significant correlation between the spectra of activity–rest cycle and BOXX. This result indicates the adjustment of the biological rhythm for the variations of the geophysical one, which corresponds to the effect of adjusting the rhythms of heart and brain human activity to an external rhythm generator, the geomagnetic field.

Episodes of normothermic levels of body temperature over a short time during hibernation were compared in hedgehogs living in the Moscow region and ground squirrels inhabiting Yakutsk. The results of superposed epoch analysis showed that although the distance between the observation sites was about 5000 km and hedgehogs and ground squirrels lived in different places, there was a connection between episodes of normothermic levels of body temperature in the animals studied: the maximum number of short-term normothermia episodes in hedgehogs  was observed on the same days that ground squirrels woke up. A 4-h biorhythm was established in the diurnal dynamics of wakefulness: the largest number of returns to normothermia was recorded both in hedgehogs and ground squirrels, according to local solar time within the time intervals 0–1 a.m, 4–5 a.m., 8–9 a.m., 12 a.m.–1 p.m., 4–5 p.m., and 8–9 p.m. It was shown that the episodes of normothermia were associated with the intensity fluctuations of secondary cosmic rays recorded by a neutron monitor. The noise intensity of silicon transistor and temperature sensors, which is small enough to be directly affected by extremely low variations in cosmic rays, correlated with the expressiveness of fluctuations in the neutron count. We believe that the magnitude of fluctuations in neutron monitor count rate is only a marker of a biotopic agent that has not yet been identified.

A study of the 4-day rhythm of the proliferative activity of the embryonic fibroblast-like cells in the logarithmic growth phase was carried out. It was shown that in cell cultures obtained on different days from embryos of different ages, the phase of the 4-day rhythm coincides. In vitro the maxima of the proliferative activity were consistent with the minima of the motor activity of mice. Freezing the culture for 2 or 6 days does not cause a shift in the phase of the 4-day rhythm of cell proliferative activity compare with the unfreezing culture. That indicates the existence of an external synchronizer, which determines the 4-day infradian rhythm of the proliferative activity of embryonic cells. Then we daily thawed samples of single L929 culture of mice fibroblast-like cells for 22 and 17 days and researched the dynamics of its proliferative activity. We also showed 4-day rhythm of the simultaneous increase in the number of cells for all thawed samples. Taking into account that deep freezing of a culture leads to the cessation of all life processes, the fact we obtained indicates an exogenous mechanism of the formation of about a 4-day rhythm of the proliferative activity of cell culture. Variations of the Earth's magnetic field could be one of the external synchronizers of the infradian rhythm. We studied the increase in number of L929 cell in conditions of a magnetic permalloy screen and showed that the magnetic shielding no affect the parameters of the infradian rhythm of L929 cell proliferative activity. So further searches of the external synchronizers are need.

Both during hibernation at normothermia and while the animals are active in summer the body temperature of hedgehogs fluctuates significantly in the range from 26 to 38 degrees C. Seasonal variability in body temperature is related to reproduction and ambient temperature. During the breeding season in May and June, the body temperature of hedgehogs is significantly higher in both males and females comparing to other seasons. This is probably due to the period of active reproduction and seasonal variability in the hormones' content in blood. The average daily body temperature in hedgehogs correlates with the ambient temperature in the summer months - May and June, when the night air temperatures do not differ much from those during daytime one and are of the optimal range for hedgehogs. In spring, at the end of summer, and in autumn, the ambient temperature may drop significantly, being out of the optimal range, and the animal body temperature does not always follow the ambient temperature changes, so no reliable correlation between them are observed. The body temperature of hedgehogs during the day is not constant: during the daytime rest in summer period, most hedgehogs have a lower body temperature, which probably saves energy. During the non-hibernation period, females usually have a higher body temperature comparing to males, which may be associated with physiological features and, in particular, with a higher metabolism. The photoperiod affects the duration of activity of hedgehogs and, accordingly, the time during which the body temperature of hedgehogs is elevated at night. During normothermia at the hibernation period, ultradian rhythms are observed for the animal body temperature with periods of 4.0-4.3 h; apparently, they are masked by the influence of other factors during the period of activity of hedgehogs.

The dynamics of proliferative activity of the L-929 cell culture of mouse fibroblast-like cells in the phase of logarithmic growth was compared with some heliogeophysical parameters (Ap and ULF indexes of geomagnetic activity, vertical component of the interplanetary magnetic field, and intensity of fluctuations of secondary cosmic radiation estimated by the neutron monitoring near the Earth's surface). Among the considered heliogeophysical parameters, only the magnitude of fluctuations of minute-to-minute changes in the neutron monitor indicator reliably and negatively correlates with the rate of cell culture reproduction. Considering that the amplitude of secondary cosmic fluctuations is about 5%, which is 0.1% of the total ray flux, and proliferative activity varies in the range of 30-50%, the probability of a direct biotrophic effect of this physical factor is extremely low. It seems likely that proliferative activity of L-929 cell culture is directly affected by another environmental factor, the marker of which is the intensity of neutron counting rate fluctuations.