Vol 54, No 2 (2023)

Comparative and ecological aspects of the reorganizations of early development in the class Amphibia are analyzed. We used data on the developmental diversity in a number of families belonging to the orders Anura and Caudata, in which many species had lost their connection with the aquatic environment. Model representatives of the class Amphibia (Ambystoma mexicanum, Rana temporaria, and Xenopus laevis) have small eggs (no more than 2.5 mm in diameter). In these species, the slowdown in the rate of cell divisions and the loss of synchrony occur at the midblastula stage. However, phylogenetically basal amphibian species (Ascaphus truei, Cryptobranchus alleganiensis) are characterized by the large (4–6 mm in diameter) yolky eggs and a short series of synchronous blastomere divisions (the synchrony is already lost at the 8-cell stage of cleavage). They do not have a “midblastula transition”, which is characteristic of the above model species. On the other hand, many evolutionarily advanced non-model species of caudate and anuran amphibians (for example, Desmognathus fuscus, Gastrotheca riobambae, Philoria sphagnicolus), as well as the basal species, are characterized by the large, yolk-rich eggs and the early loss of cell division synchrony. Phylogenetic analysis suggests that the cleavage pattern of the most extensively studied amphibians, the Mexican axolotl (Caudata) and the African clawed frog (Anura), represents a homoplasy. The midblastula transition, which is characteristic of these two species, might have evolved convergently in these two orders of amphibians as an embryonic adaptation to development in lentic water.

Fishes of the Barbus (=Labeobarbus) intermedius complex (Actinopterigii, Cyprinidae), known in Russian-language literature as Large African Barbs, are widely distributed in Africa water bodies. A special feature of the morphological diversity of this group of fish is the sympatric coexistence of morpho-ecological forms in local populations. The most famous example of such coexistence takes place in Lake Tana located in the north of Ethiopia, where, according to different authors, up to 15 morpho-ecological forms (morphotypes) live. The diagnostic features of the barbs of Lake Tana morphotypes are clearly manifested upon reaching a standard length (SL) of about 15 cm. With a shorter length, representatives of most morphotypes are indistinguishable from each other. This suggests that in ontogenesis, the main vectors of morphological variability of the Tana Lake barbs may be different before and after individuals reach a length of 15 cm. The aim of this study was to test this assumption. The results obtained confirm that in this population, the standard length (SL), equal to about 15 cm, delimits two stages of postnatal ontogenesis in the studied group of fish. In individuals with SL < 15 cm, the main vector of variability is a consequence of changes in morphological proportions as the individual grows. In individuals with SL > 15 cm, the main vector of variability is most likely associated with the trophic resource partitioning. The original approach used in the study is considered promising in analyzing the peculiarities of variability at different stages of ontogenesis not only of the studied group, but also of other systematic groups.

The effect of constant and natural lighting modes in combination with different feeding regimes on the activity of energy and carbohydrate metabolism enzymes in the muscles and liver of salmon under-yearlings artificially grown in aquaculture in the southern region of Russia was investigated. The revealed differences in the activity of the studied enzymes in under-yearlings indicate changes in the level of energy metabolism and the use of carbohydrates in the processes of ATP synthesis and other biosynthesis pathways in muscles and liver, depending on lighting conditions and in combination with the feeding regime. The high level of aerobic metabolism in the muscles and the increased use of carbohydrates in glycolysis in the liver in salmon fingerlings raised under constant light corresponded to their highest average weight gain. In individuals from all experimental groups, changes in the activity of the studied enzymes were found in dependence on the time after the start of the experiment, that indicated an increase in the levels of aerobic and anaerobic metabolism in muscles and glycolysis in the liver, necessary for the biosynthesis processes during growth.

Here for the first time, the organization of promoters of developmental gene promoters and promoter of genes necessary for general cellular functions—the “houskeeping” of the cell in the complete genome of Drosophila melanogaster were studied. Using bioinformatic methods, it has been shown that the genes whose promoters are located in the interbands of polytene chromosomes are enriched in functions associated with general cellular processes, while the rest of the genes (about half of the Drosophila genome) are associated with highly specialized processes occurring during development. In the promoter zone of the housekeeping genes, four specific motifs were found that can be present in different genes individually or in various combinations. A significant part of interband promoters do not contain identified motifs. The analysis carried out using Gene Ontology showed that certain groups of interband genes containing one motif in promoters or their combinations are characterized by the performance of certain functions.