Vol 85, No 3 (2024)

Many studies have shown that associated microbiota influences the life history traits of Drosophila melanogaster. The increase in bacterial load reduces lifespan but may increase fecundity. Paradoxically, the influence of yeast microbiota, a key food source for fruit flies, on life history traits is much less studied. In this work, we assessed the influence of natural yeast microbiota, as well as individual yeast species, on lifespan, age-related dynamics of fecundity, and mortality in the control fly line and the fly line with depleted yeast microbiota. We used Starmerella bacillaris, Zygosaccharomyces bailii, and Saccharomyces cerevisiae as individual yeast species for testing. We have shown that the decrease in the amount of symbiotic yeast on the medium, on the surface of the body, or in the fly intestine leads to an increase in lifespan and a decrease in fecundity for flies reared on standard medium. It is consistent with the “disposable soma” hypothesis. At the same time, an increase in lifespan does not compensate for the decrease in fecundity; therefore, the decrease in the number of yeasts leads to a decrease in fly fitness. Inoculation of S. cerevisiae on the medium shifts the reproduction of the control flies to an earlier age, while two other yeast species increase fertility significantly. Inoculation of S. bacillaris and S. cerevisiae (not typical for the microbiota of tested fly lines) on the medium reduces lifespan more than yeast Z. bailii, which is typical for the microbiota of the control line. Yeast microbiota reduces the lifespan of the Drosophila males more than the females. The results indicate deep coevolutionary relationships between the components of the yeast microbiota and the host organism, requiring further studies within the hologenome theory of evolution.

The individual variability of morphological features of pollen of 55 species of the genus Cestrum (Solanaceae) was studied using light-optical and scanning electron microscopes. Typical pollen grains of the studied species are 3-colporate; the ora are equatorially elongated; in pollen of some species they form a continuous equatorial oral belt; the sculpture is psilate, striate, tuberculate, rugate. The scope and structure of variability of pollen morphological features (number and location of apertures and surface sculpture) in the studied samples of Cestrum species are described at the individual level and at the level of the genus as a whole. The variability of the studied pollen traits fits into continuous, regular, transitively ordered (taxon-nonspecific and rank-independent; over the boundaries of the relationship of taxa and homology of structures) geometric series. Pollen features are not informative enough to clarify the sectional division of the genus (all sections of the genus are palynomorphologically heterogeneous), although they can be used to diagnose individual species. The studied species cannot be divided into any distinct groups in accordance with the considered genus system — pollen signs overlap, their variability is parallel and transitive. The distinction of discrete features in a continuous variety is rather logical and requires a significant (from a theoretical point of view) reduction of the natural variety — the observed variability. Typical and atypical variability are combined into indivisible (continuous) and integral (ordered) series. Forms that may be typical in different taxa do not belong to different archetypes (body scheme) of different taxa, but together with atypical pollen forms are arranged in continuous and geometrically ordered transitive (parallel) morphological series. Indivisible (continuous) and holistic (ordered) series are combined typical and atypical variability in the forms of aperture arrangement. Different forms of apertures arrangement, which may be typical in different taxa, do not belong to different archetypes (the body scheme of different taxa), but, together with atypical forms of pollen, line up in continuous and geometrically ordered transitive (parallel) morphological series. The described properties of the structure of individual variability are considered from the perspective of a non-typological model of biological form (metamorphoses).

A new version of the description of thermobiological statuses in vertebrates is proposed: primary and secondary ectotherms, primary and secondary endotherms. Primary ectothermal animals are the first amphibian-like tetrapods (among modern animals – fish and amphibians). They had a low level of metabolism, and most of the body temperature for a number of physiological reasons could not rise above 30°C and almost did not differ from the ambient temperatures. Then they developed a complex of biochemical and physiological aromorphoses, which increased their levels of mitochondrial oxidation and basal metabolism, and began to force them to raise their body temperature. This significantly improved the quality of their activity and other functional characteristics, allowed them to go on land and begin to master it. Already the first terrestrial tetrapods (stegocephalians, seymourians) had an increased metabolism about 330 million years ago. These were basic primary endotherms – mesometabolic animals whose body temperature could hardly rise noticeably more than 30°C; they still had insufficiently developed mechanisms of regulation and control over the levels of metabolism and heat production. In the synapsid line, metabolism gradually increased along with body temperature, and through theriodonts led to the appearance of secondary endothermic animals with constantly high, controlled and regulated tachymetabolism and thermometabolism – mammals. Sauropsids also had an increase in metabolism, and in some archosaurs (dinosaurs, etc.) it sometimes rose to the level of modern birds, and body temperature reached 39–44°C. Some of them developed into secondary endothermic tachymetabolic birds, and some other – into secondary ectothermic bradymetabolic modern reptiles with a periodic increase in body temperature to 30–45°C due to external heat. But secondary ectotherms (mainly modern reptiles) are not a “return” to the state of primary ectothermy, but a powerful evolutionary step forward. Having passed through the mesothermic stage of ancient reptiles in their evolution, they acquired the ability, unlike primary ectotherms, to withstand and use high body temperature (>30°C) for their functional and evolutionary benefit. It was by raising their body temperature that vertebrates increased the level of basal metabolism, improved the quality of activity, etc. Thus, the evolutionary function of reptiles is to “teach” primary ectothermic vertebrates to use high body temperature and in this regard become an “elevator” for further evolution of vertebrates. The vast majority of reptiles during their existence were meso- and tachymetabolic endothermic animals, i. e. warm-blooded to varying degrees, and bradymetabolic ectotherms, i. e., classical cold-blooded, turned out to be evolutionarily advanced modern reptiles. In general, ectothermal animals tend in their evolution to “align” with the temperature conditions of the external environment, “fit in” with them, use them. They periodically raise their body temperature due to external heat during periods when it is naturally available, thereby increasing the level of metabolism, the quality of activity and vital activity in the most energetically cheap way. Endothermic animals, on the contrary, try to reliably autonomize themselves from external conditions, raising body temperature mainly due to the endogenous thermogenesis, as a result of which their metabolism reliably and constantly increases, the quality of activity and vital activity improves. This approach is much more energy-intensive, but more reliable, and significantly less dependent on changeable environmental conditions, improving environmental valence and competitiveness. Thus, ectothermy and endothermy are two independent directions of the evolutionary development of vertebrates, each with its own strategy and ways of its implementation. At the same time, ectothermy is not a stage in the development of endothermy, but an independent evolutionary direction of the development of vertebrates, parallel to endothermy.