Vol 9, No 5 (2019)

I suggest a common population genetic mechanism that explains persistence of biological species as consistently reproducing groups of similar organisms: genetic renewal due to genetic drift or selection, which restricts genetic diversity of populations. In contrast to concepts explaining species integrity via interbreeding, the concept of drift- and selection-induced genetic renewal explains species existence not only for sexually reproducing organisms, but also for asexual, or agamous, organisms. I redefine concepts of population, isolation and species in terms of genetic renewal. The proposed concept of renewing species develops Alan Templeton’s cohesion species concept.

Wolbachia are intracellular symbiotic bacteria of terrestrial arthropods and some nematodes. They are found in most insect orders; however, there are insufficient data on symbiont distribution patterns for some taxonomic groups. Here, we examined a collection of Siphonaptera species by conventional and nested polymerase chain reaction. A total of 722 specimens from 30 species were sampled in three regions of Russia: Southern Russia, Ural and the Far East. Wolbachia infection was found in half of the species, which confirmed previous data on the widespread nature of the infection in Siphonaptera. No statistical differences in Wolbachia incidence in flea species from Southern Russia and the Far East were detected, although species lists of these regions completely differed. We did not find totally infected flea species, although high infection rates were detected for Frontopsyllaelatabotis (64.5%) and Ctenophthalmuswagneri (66%) with sample size exceeding 30 specimens. Our results are in agreement with the data from other regions of the world. Combined data of our study and other authors indicate that Wolbachia symbionts are found in all 11 studied families of Siphonaptera and in 45 out of about 120 studied species in the world.

The dependence of the growth and functioning of the transport system of colonial organisms on water temperature has been studied. Time-lapse microvideo recording was used to measure the coenosarc pulsations of the stolon and shoot in the colonial hydroid Dynamena pumila (L., 1758) reared in seawater at 10, 15, 20, 25, and 28°C. As a result, it was possible to determine that microvideo recording of coenosarc pulsations made it possible to track the colony reaction to temperature change for 2 h. The reaction of growth pulsations, lateral pulsations, and hydroplasmtic flows to the changes in the water temperature turned out to be nonlinear. The reaction of the stolon to the changes in the water temperature was more pronounced than those in the shoot. The optimal temperature range was 10–20°C, which displayed the highest growth rate, the most intensive hydroplasm movements, and the largest volume of transferred hydroplasm. At 28°C, the pulsations of the stolon coenosarc became unstable, the growth tended to slow, and the hydroplasm movements were less active. Consequently, according to the results of analysis of coenosarc pulsations, the upper temperature limit of normal life activity for D. pumila colonies inhabiting the White Sea was 25–28°C.

Symbiotic microbes affect many aspects of the life of multicellular organisms and may favor their adaptation to a changing environment, but there is little direct experimental evidence of such a contribution. To assess the possible role of the microbiome in the adaptation of Drosophila melanogaster to a high-NaCl feed substrate, we used two laboratory lines of salt-adapted flies (C1, C2) and two control lines cultivated on a standard feed without salt (H1, H2). We have already shown that the presowing of homogenate of flies C1 on the surface of a saline feed increases the breeding efficiency and enhances the development of drosophila larvae in comparison with a homogenate of H1 flies. We repeated this experiment for lines C2 and H2 and obtained similar data, which proves the reproducibility of the revealed effect. In addition, we found contrasting differences in the number and taxonomic composition of yeast in drosophila homogenates of the salt-adapted and control lines. The results correspond to the assumption that changes in the symbiotic microbiome, including its yeast component, may contribute to the adaptation of drosophila to unfavorable feed substrates. The possible evolutionary consequences of such a contribution are discussed in this work.