Ecological Aspects of Circadian Rhythms in Six Species of Omni-Seasonal Beetles (Coleoptera, Tenebrionidae) Inhabiting Kara Kum Desert (Turkmenistan)

Circadian rhythms of activity were compared in ground-dwelling Tenebrionid beetles from the Kara Kum sand desert: Trigonoscelis gigas Reitter, Trigonoscelis sublaevicollis Reitter, Pisterotarsa gigantea Fish.-W., Sternodes caspicus Pall, Blaps faustii Seidlitz, and Ocnera imbricata Fish.-W. For the observations, artificial pens (enclosures) 60 × 60 cm and 80 cm deep were arranged in field conditions and filled with various kinds of sand to simulate natural habitats as closely as possible. The activity of individually marked beetles was assessed visually and recorded every 30 min. The beetle species studied had different types of behavior, from strictly crepuscular to strictly nocturnal. Closely related species sharing one habitat differed in activity pattern — they occupied different time niches; hence their circadian rhythms contribute to reproductive isolation. In contrast, non-closely related species could have similar circadian patterns as a result of convergent evolution. In experiments with T. gigas, we failed to stimulate individual variability among beetles in circadian pattern by applying additional light and heat at night. Therefore, the circadian rhythms in field conditions were found to be remarkably stable, which can be explained by our model of the beetle circadian system consisting of two strongly coupled oscillators. However, in laboratory conditions, we previously observed a wide range of individual variability in free-running circadian rhythms. The strong coupling between two putative endogenous circadian oscillators is a crucial tool for beetles to survive in a harsh arid environment. Such organization of the circadian system ensures synchronous activity of beetles despite individual differences, thus preserving the variability of circadian clock properties in a population, which increases chances for survival of a population in a changing environment.     

Effect of kyotorphin on the reactivity of hippocampal neurons

The effects of kyotorphin (Tyr-Arg) on CA1 and CA3 field responses were studied on rat hippocampal slice preparations. Slice perfusion with 10(-6)-10(-4) M of kyotorphin resulted in reactivity changes both in mossy fibers (CA3) and Schaffer collaterals (CA1). The principal effect was the increase in pop-spike amplitude. Kyotrophin (10(-6)-10(-5) M) and metenkephalin (10(-7)-10(-6) M) were found to produce similar reactivity changes (facilitation) in CA1 region of most preparations. However, kyotorphin effect, in contrast to enkephalin-induced facilitation was not blocked by naloxone. The data suggest that the mechanisms of kyotorphin action in the hippocamp are not related to endogenous enkephalin release.     

The parasitic wasp <Emphasis Type="Italic">Baryscapus crassicornis</Emphasis> (Erdös) (Hymenoptera,Eulophidae) developing in larvae of the weevil genus <Emphasis Type="Italic">Larinus</Emphasis> germar (Coleoptera,Curculionidae)

Baryscapus crassicornis (Erdös) was reared from the last instar larvae of three species of Curculionidae: Larinus idoneus Gyllenhal, developing in the inflorescences of Jurinea cyanoides (L.), L. turbinatus (Gyllenhal), developing in Cirsium arvense (L.) in Russia (Ul’yanovsk Province), and L. latus (Herbst), developing in Onopordum acanthium L. and O. leptolepis DC. (Asteraceae) in Iran. Data on the parasitoid and its hosts biology, variation of morphological characters, and diagnostic notes are provided. The 3rd instar larva and the pupa of B. crassicornis are described for the first time.     

Influence of Low-Intensity Electromagnetic Field on Some Biological Parameters of Freshwater Crustaceans <Emphasis Type="Italic">Daphnia magna</Emphasis> Straus

We have studied the effects of a low-intensity electromagnetic field (EMF) with a frequency of 30 MHz in continuous-wave and amplitude-modulation modes on Daphnia magna in a laboratory culture. The exposure range is from 10 to 10000 s. We examine the parental generation (irradiated) and three subsequent (F₁–F₃) generations (nonirradiated). It is found that irradiation does not affect the total fertility of any specimen in four generations (P–F₃), except for continuous EMF exposure for 10000 s, which increases the total fertility in generations F₂ and F₃ by 23 and 43%, respectively. Electromagnetic radiation has a significant impact on offspring quality and causes fetal abnormalities in the offspring of all generations.     

The effect of infrared laser irradiation on the growth of human melanoma cells in culture

Biophysics - Low-intensity laser irradiation exerts effects on various biological objects and is currently exploited in various branches of medicine. From a practical point of view, irradiation in...     

Circadian rhythm of activity as a factor of reproductive isolation in closely related species of sand-desert tenebrionid beetles (Coleoptera,Tenebrionidae)

The results of long-term studies of the circadian rhythms of activity in Trigonoscelis gigas and T. sublaevicollis, typical and abundant representatives of the tenebrionid fauna in the Kara Kum desert are given. T. gigas and T. sublaevicollis are omni-seasonal species: their adults are observed on the sand surface from spring till late autumn. They spend their resting period in soil. Adults of both species are similar in morphology, ecology, and behavior, strongly differing in the circadian rhythm pattern. T. gigas are active only at twilight, whereas T. sublaevicollis are characterized by nocturnal activity. Therefore, inhabiting the same habitat, T. gigas and T. sublaevicollis never meet each other under natural conditions, independently of the season and weather. Hence, the circadian rhythm of activity can serve as a reliable mechanism of reproductive isolation in closely related tenebrionid species.     

Regulation of hemodynamics in sympathectomized rats after adaptation to tail suspension

The organism adapts to actual or simulated microgravity by complex interactions of nervous, hormonal and local control mechanisms. Sympathetic nervous system is believed to play the leading role in this adaptation (Robertson et al. 1994). However, this conclusion seems to be rather deductive, as it has not been proved directly. Chronic sympathectomy provides a straightforward approach to this problem. We have studied the role of sympathetic nervous system in adaptation of cardiovascular system to simulated microgravity by tail suspension in intact and sympathectomized rats.     

Circadian rhythm of light sensitivity in the beetle <Emphasis Type="Italic">Coccinella septempunctata</Emphasis> (Coleoptera,Coccinellidae): Effects of illumination and temperature

Beetles Coccinella septempunctata L. are active only during daylight. It is demonstrated that sensitivity to light, the photopreferendum, and locomotor activity are regulated by endogenous circadian oscillators. The percentage of beetles that became active during the first 10 min after light-on was determined. Sensitivity to light (100, 1000 or 7000 lx) reached the maximum in the daytime (period of activity) and the minimum at night (resting period) irrespective of temperature (17 or 26°C). Illumination and temperature serve as modifying factors for the pattern and amplitude of the circadian rhythm of light sensitivity.     

Hydrogen Sulfide Donor NaHS Protects Mesenchymal Stem and Melanoma Cells from the Negative Effects of Infrared Laser Irradiation

Molecular Biology - We have established earlier that 835-nm infrared laser irradiation results in a dose-dependent growth inhibition of human mesenchymal stem and melanoma cells and is able to...     

Marking activity of common beaver (<Emphasis Type="Italic">Castor fiber</Emphasis> L.) in the settlements of channel type. Dynamic aspect

Features of the marking activity of beavers in the channel-type settlements are considered. On the basis of statistical data it was determined that the signal hillocks may be recommended for investigation of dynamic indexes of scent marking by beavers. On the basis of quantitative methods the role of the level mode of water streams in the appearance of olfactory marks is demonstrated; as a result, the inversely proportional dependence between these parameters has been revealed.