[Variability of Quantitative Morphogenetic Parameters during Early Morphogenesis of the Loach, Missgurnus fossilis L].

Analysis of normal variation in quantitative morphological characters during the early embryonic development of the loach, based on fixed material and individual developmental trajectories of living embryos, shows that the dorsoventral differentiation of the blastoderm proceeds in two stages. Initially, at the onset of epiboly, the sagittal (short) and transverse (long) blastoderm meridians are marked off, and only then, upon germ ring (GR) formation, differentiation between the opposite poles of the sagittal meridian takes place. The embryonic shield (ES) usually appears in the segment of the blastoderm where the radius of its external curvature reaches a maximum and, therefore, the active surface tension at the blastoderm boundary with the YSL (peri-blast) and yolk is the highest. In this case, the convergence of inner cells toward the future dorsal segment (leading to ES formation) is a mechanical consequence of surface tension anisotropy. The normal course of epiboly is associated with periodic changes in the curvature of the blastoderm external surface, with new structures (the dorsal segment, GR, and ES) are marked off only when the surface curvature becomes maximally uniform. Although the ES in most embryos appears within the initial dorsal segment, individual developmental trajectories have been traced where the GR starts to form at the dorsal pole of the blastoderm but the ES develops on its opposite site, at the point of GR closure. In both cases, GR formation is initiated at the point of convergence of centrifugal cell migration flows that arise in the marginal zone of the blastoderm upon GR initiation or closure.

[Geometry of Movement of the Outer Surface of the Embryo during Xenopus Gastrulation].

The surface of Xenopus laevis embryos was marked with carbon particles, after which the location of mark groups was recorded by time-lapse video imaging and subsequent image analysis until their disappearance in the depth of gastric invagination. Measuring the distances between individually identifiable marks whose size is smaller than the size of a single cell makes it possible to quantitatively analyze the geometry of collective cell movement without any external coordinate system. During the dorsal blastopore lip (DBL) formation, the invagination of surface cells fundamentally differs from the preceding and subsequent lateromedial (LM) intercalation, being associated with a decrease in the meridional distance and an increase in the latitudinal distance between the marked surface sites. The sites that began to move towards the DBL later overtake the areas that started movement earlier, which leads to a "plug" in the movement of cells. Pushing the "plug" into the inner layers by changing the DBL shape becomes the rate-limiting stage of gastrulation; then, the directed cell movement is replaced by epiboly based on LM intercalation when the marks remaining on the outer surface of the marginal zone diverge along its meridians without directed migration towards the blastopore. As a result, directional movement of cells and LM intercalation become successive phases of collective cell movement, and the entire morphogenesis of DBL is the direct consequence of epiboly deceleration occurring upon gastric invagination.

[Morphogenetic consequences of partial removal of blastomere cytoplasm during early embryonic development of the loach, Misgurnus fossilis L].

The development of loach embryos is successfully regulated (normalized) after partial removal of the cytoplasm from one blastomere at the two- or four-cell stage or complete removal of one or two blastomeres at the stage of 8-16 cells. Using time-lapse video imaging and morphometric analysis, it has been shown that this regulation is a two-stage process. At the first stage, the ratio between the volumes of the blastodisk and yolk sac is rapidly (within one or two cell cycles) restored almost to the initial level; at the second stage, morphogenesis of the embryo is modified according to its new structural features acquired after the operation. After several rounds of cytokinesis, the cytoplasm remaining in the operated blastomere fuses with the marginal yolk syncytium (periblast),which at the blastula stage forms a distinct extension at the operation site. This extension marks the site of embryonic shield formation. The results of morphometric analysis show that restoration of the initial blastoderm volume in operated embryos leads to a reduction of active tension at the blastoderm--yolk boundary and an increase in the ratio of blastoderm surface to its volume at the moment of epiboly initiation. As a result, the convergence of blastoderm cells to the operation site and the embryonic shield formation begin at a lesser degree of epiboly, compared to the control.

[Geographic variation of sexual dimorphism in the moor frog (Rana arvalis) as a result of differences in reproductive strategies].

Several local populations of the moor frog (Rana arvalis) from the southern part of the range (the Ukraine) were compared by size and age composition and morphological characters in males and females with one of the populations from Moscow Region (Zvenigorod Biological Station-ZBS). In spite of close geographical location of the Ukrainian populations (not more than 40 km), they differ significantly both in mean body size and age. At that, mean value of these parameters turned out to be lower than the corresponding values for the ZBS population. In southern populations, the proportion of females breeding for the first time right after the second hibernation is higher than males; comparing to the ZBS population, the part of two-years-old mature specimens of both sexes is higher while the part of older specimens is lower. This geographical variability of age composition causes significantly lower mean age and body size of specimens from the southern populations. Although in the Ukraine the activity season is longer than in Moscow Region, the growth rate of two- and three-year-old frogs from southern populations is lower, and only at age of four they become larger than specimens from the ZBS population. These differences are caused by higher reproductive effort both in females and males from southern populations. Morphologically, males and females from southern populations differ most significantly by shin and hip length (absolute and relative values of the characters are higher in males). As compared to the Ukrainian populations, both sexes in the ZBS population have lower values of these characters. The overall sex differences by absolute and relative values of these characters are more pronounced in the ZBS population. Meanwhile, concerning body size, males are bigger than females in the ZBS population, and this difference remains and is even more pronounced in the southern populations. Geographic variation in body size is more expressed in females than in males, which corresponds to more significant sex differences in the Ukrainian populations in this regard. The reason behind this lies in dissimilarity in reproductive strategies: males from the ZBS population participate in the breeding for the first time at younger age than females whereas in the Ukrainian populations males take part in reproduction at older age (hence, at bigger size) which ensures their greater reproductive success.

[Geometry and mechanics of the morphogenesis of active membranes on the example of plant trichome cells of the genus Draba L].

The stages of the early morphogenesis of simple (unbranched) and complex (branched) unicellular trichomes are studied in two species of the genus Draba--D. sibirica (Pall.) Thell. and D. daurica DC. The geometry of morphogenesis is estimated by analyzing intraindividual variation of quantitative morphological characteristics of the developing leaf blade and peduncle trichomes. The surface of all types oftrichome cells first acquires a spherical shape, followed by a U-shaped configuration with cylindrical proximal and spherical distal regions. In the development of complex trichomes, the area of the distal zone grows at a higher rate, which leads to separation of its volume into individual spherical regions, the morphogenesis of which repeats the early morphogenetic stages of the overall trichome cell, forming simple (unbranched) or complex (branched) trichome rays. As a rule, the lateral polarity of a trichome cell coincides with the proximodistal polarity of the leaf. Quantitative morphological data make it possible to infer an algorithm of the changes in shape common for all trichome cells, namely, the growth cycle comprising alternation of the phases of increase and decrease in the curvature of the outer cell surface. This surface is an active membrane expanded by the internal pressure and concurrently capable of actively increasing its area by incorporation of new structural elements. A distinctive feature of the proposed model is the geometrical inhomogeneity of the surface movement, changing the radius of curvature and creating internal (active) mechanical stresses in this membrane. A decrease in the ratio of the membrane surface area to the volume deprives the spatially homogeneous shape of its stability; correspondingly, the transition from elastic resistance to internal pressure to active resistance with the help of curvature differentiation becomes more energetically favorable. The source for growth and morphogenesis of the active membrane is alternation of the phases of local curvature leveling, which "charges" the membrane with active mechanical stresses and "discharge" of these stresses, leading to differentiation of the membrane's local curvatures.

[Geographic variation as a result of evolution of the traits with broad and narrow norms of reaction in the moor frog (Rana arvalis)].

Females reproductive, size, and age characteristics were studied in isolated local populations of Rana arvalis in the southern and northern parts of its range. The yearlings of the southern populations used to get larger by their first overwintering due to earlier beginning of the breeding season, as compared with the yearlings of the northern population. As a result, "southern" females become sexually mature at the age of two years while the "northern" ones become mature at the age of three years. This causes geographic differences in age composition among two populations, the "southern" reproductive females being younger on average than the "northern" ones. The earlier female maturation in the first case is not compensated by respective rise of the growth rate; to the contrary, the "southern" females grow more slowly during the first two years of their life and appear to be smaller than the "norhern" ones. These reproduction and growth patterns arise supposedly due to paedomorphosis, which causes specific reproductive characteristics, namely decrease in the egg size, increase in the reproductive effort and more strong correlation between female fertility and body size. Local and geographic differences are expressed not in the extent but in the structure of reproductive pattern, as no negative correlation was revealed between female reproductive age and body size in the southern populations. Southern habitats cannot be considered as "unfavourable with respect to body size", so the geographic differences under consideration cannot be explained by optimization of the reproductive strategies at population level. Paedomorphosis appears as a result of the female maturation rate possessing a wider norm of reaction than the growth rate. At the same time, fixation of the specific growth rate narrows norm of reaction of some other characters important for the phenotype reproductive fitness thus predetermining their subsequent evolution.

[Spatial-temporal dynamics of morphogenetic blastoderm potencies in early embryogenesis of the loach].

The degree of differentiation of axial structures (notochord, neuroectoderm, and somites) in 24-hour explants (a total of 380) of the loach embryonic blastoderm was determined on histological sections according to a developed scale of estimates. Before the beginning of epiboly, axial structures were formed only from fragments of the dorsal sector of the blastoderm marginal zone. Its other sectors acquired the capacity of forming axial structure only with the beginning of epiboly, as the germ ring was formed in the marginal zone, unlike the cells outside the germ ring. The degree of differentiation of axial structures in the dorsal sector of marginal zone increased reliably with the appearance of embryonic shield, i.e. area of the convergence of cell flows. Here, statistically significant regional differences in morphogenetic potencies of the marginal zone first appeared, which corresponded to the differences in prospective significance of its materials; notochord and neuroectoderm better differentiate from the dorsal sector material, while somites better differentiate from the ventral sector material. Thus, distribution of morphogenetic potencies reflects precisely the spatial-temporal dynamics of collective movement of the blastoderm cells during the normal course of morphogenesis.

[Dynamics and variability of early morphogenesis in the loach according to observations of individual developmental trajectories].

The dynamics and variability of quantitative morphological characters (morphological variables), which undergo changes upon epiboly, were studied by means of vital observations and measurements of developing loach (Misgurnus fossilis L.) embryos within equal time intervals. None of morphological variables, which characterize the dynamics of blastoderm shape, had monotonous dependence on time. In each individual embryo, the intervals of changes in morphological variables in the "normal" direction corresponding to the change of their mean values during the normal course of epiboly alternated with arrests, as well as with the changes of morphological variables in the reverse direction. The dynamics of morphological variables in time, which reflect the sequence of morphological states of the same embryo, and those of individual variations (variations of morphological states of different embryos on the same temporal section) had identical structure. This suggests instability of individual trajectories of morphogenesis or, strictly speaking, their actual absence. It was shown for the first time on the basis of analysis of individual trajectories of morphogenesis that its dynamics corresponded to so-called "determined chaos", which was previously discussed only as a theoretical possibility. The data obtained suggest that upon approach to the equatorial area of the embryo, the blastoderm marginal zone was elongated in the longitudinal direction and contracted across the axis of its movement. As a result, a positive feedback arises between the cooperated cell movement and the change of shape of the surface, over which the cells move. This leads, due to unstable radial symmetry of this movement, to the formation of embryonic shield.

[An experimental study on the formation of anterior-posterior polarity in the early development of the marine hydroid Dynamena pumila]. / Eksperimental'noe izuchenie formirovaviia perednezadnei poliarnosti v rannem razvitii morskogo gidroida Dynamena pumilia.

Elements of evolutionarily initial morphogenesis providing for the formation of main body axes could have been preserved in embryogenesis of lower Metazoa animals, Cnidaria. However, the information on the morphological bases of axes formation in their normal development is not yet complete. When studying the normal development of Dynamena pumila (Hydrozoa, Thecaphora, Sertulariidae), it has been proposed that the region, where the embryonic ectoblast remained unclosed for the longest time, determines the position of the posterior pole of the larval anteroposterior axis. In the experiments, the formation of closed ectoblast in an arbitrarily chosen region of the embryonic surface was delayed artificially, for example, by incisions. The fate of this region was traced with the help of a mark consisting of carmine particles. It was shown that the posterior pole did differentiate near the region of surface, which was the last to epithelize and redetermination of the anteroposterior axis orientation was only possible before the formation of closed ectoblast in the normal development. The morphogeneses involved in the formation of anteroposterior axis and its poles in Dynamena embryos were reconstructed by means of observations over the displacement of mark particles. It was shown that the establishment of this axis and appearance of morphological differences between the anterior and posterior planula poles are morphogenetic consequences of the closed ectoblast formation. The region, in which the closure of ectoblast is delayed, is a functional analog of the blastopore of higher Metazoa.

[Cytoembryologic aspects of evolution of specialized electric organs of fishes]. / Tsitoémbriologicheskie aspekty évoliutsii spetsializirovannykh élektricheskikh organov ryb.

Almost all fish electric organs (EO) developed from the skeletal muscles or from its embryonic rudiments. The only exception is the definite (in contrast to larval) EO of Apteronotidae, formed by motoneurons, whose loss of relation with muscles is secondary. The main feature of all EO of the muscle genesis is cooperative morphological and electrophysiological polarity of their electrocyte cells anterioposteriorly or (in Torpedo, Uranoscopus) of the dorso-ventral axes of the body. In particular, for the EO of muscular origin, unilateral asymmetric innervation of electrocytes by electromotoneurons is characteristic. Such innervation is a prerequisite condition for the summation of electric discharges. It is one of the main distinctions of EO from definitive skeletal muscles. However, in the emryogenesis of all vertebrates the initial innervation of muscle rudiments by the so-called pioneer motoneurons occurs. In teleosts (according to data on Brachidanio rerio available) extending to every myotome are outgrowths of three pioneer motoneurons referred to after their position in the nerotubule as "rostral", "medial" and "caudal". The former two innervate dorsally with the dorsal compartment of the myotome. The third approaches the ventral compartment of the same myotome caudally. In the gymnotic fish the innervation of EO formed from the axial skeletal muscles retains the same nature. The electrocytes of EO from the dorsal and ventral compartments of the myotome, are approached by electromotoneurons, respectively, rostrally and caudally. In compartments, the antipolarity of the innervation of the dorsal and ventral EO compartments leads to a paradoxical effect of generation of anti-polar pulses. The summation of these pulses creates a very short difference electric charge. In Mormyridae the antipolarity of the innervation of the rostral and ventral compartments of EO formed from the axial muscle is not pronounced. However, electroneurons resemble pioneer motoneurons by the following characters: the large size of the bodies and their localization near the central tube, absence of dendrities, electrosynaptic connection, polar (asymmetrical) pattern of electrocyte innervation. Outside EO, the cooperative polarity of the cells is only characteristic of epithelia, particularly, ciliated. At the same time, in some electric fish, the electrogeneratory tissue is similar to epithelium in a number of morphological characters, or the genes expressed in it show the gene of keratin AE-1, typical of epithelia. The above gives grounds to believe that EO of muscle origin are a product of fixation and aggravation by natural selection of hereditary anomalies, manifested in the recovery or in the retaining of the embryonic (i.e., polar nature) of the efferent innervation of some parts of skeletal muscles. Another distinction of EO from the muscles appears to lie in the expression of some individual components of the gene epithelial complex. A method is proposed for electromyographic recording of such anomalies and molecular-genetic approachers to analysis of their nature. The causes of the absence of EO epithelial genesis are discussed and also of the fact that these organs developed only in the evolution of fish.

[Microfolds in the suprablastoporal zone of the frog gastrula and their relationship to the geometry and mechanics of gastrulation]. / Mikroskladki v suprablastoral'noi zone gastruly liagushki i ikh otnoshenie k geometrii i mekhanike gastruliatsii.

Spatial distribution and orientation of microfolds arising during invagination of the outer layer of suprablastoporal zone into the blastopore dorsal lip and changes of the lip shape were studied in Rana ridibunda embryos using statistical analysis of a normal individual variability. Active invagination of the cells into the lip correlated with deviation of the orientation of microfolds from the normal in the points of their intersection with the zone of dorsal lip inflection and their orientation is normalized upon transition of the cells across the inflection zone. Frequency distribution of the angle of microfold deviation from the normal is close to the exponential and, therefore, the angle of deviation is an analog of the potential energy of cells-components of the microfold: the bigger the deviation angle, the higher the potential energy. The minimum potential energy is observed at the normal orientation of microfolds, i.e., when it coincides with the radius of the dorsal lip curvature at the point of intersection with the microfold. The following mechanism of dorsal lip formation has been proposed: equatorial contraction of cells upon their invagination into the dorsal lip causes deviation of cell flux orientation from the normal orientation and the normal orientation is restored through an increase in the local curvature of dorsal lip. When the orientation of cell fluxes is normalized, invagination of cells in the dorsal lip ceases. The wave of normalization overtakes the wave of cell invagination into the dorsal lip at the lip angle length 120 degrees. At this moment, the archenteron roof is mechanically detached from the superficial cells of the suprablastoporal zone and lateral blastopore lips and this determines separation of the presumptive notochord.

The morphological basis of self-organization. Developmental and evolutionary aspects.

Developmental self-organization is usually considered as a matter of reaction-diffusion systems. These systems, however, require a specification that can arise only from natural selection. Meanwhile, in the evolutionary context, self-organization is equivalent to the origination of evolutionary novelties: this implies that new structural patterns emerge before they acquire a definite biological function, so that selection is of no relevance in this case. It follows that self-organization should be inherent to the macroscopic (morphological) level of the developing system. Our idea is that the morphogenetic process can emerge on the macroscopic scale only provided that the temporal sequence of events is realized as a spatial sequence of morphological states, and vice versa.

[Embryonic cell aggregation in the loach Misgurnus fossilis L. in vivo and in vitro. The agonist of sigma opiate receptors SKF 10,047 as a regulator of the aggregation]. / Agregatsiia émbrional'nykh kletok v'iuna Misgurnus fossilis L. in vivo i in vitro. Sigma-agonist opiatnykh retseptorov SKF 10.047 kak reguliator agregatsii.

SKF 10,047, known as an agonist of sigma opiate receptors of the brain, specifically interacts with the surface of embryonic cells of the loach inducing clustering of concanavalin A receptors, changing rheological properties of the membrane and causing the detachment of the cultivated cells from the glass. Both, in situ and in vitro, the rate of cellular aggregation increases together with the increase in the local density of aggregates; aggregation looses its spatial homogeneity. Therefore, there is a direct relationship between destabilization of spatially homogeneous condition at the cellular and supracellular levels.

[Structure of the morphogenetic movements of gastrulation in Anura. I. Destabilization of ooplasmic segregation and cleavage under the action of clinostatic rotation]. / Struktura morfogeneticheskikh dvizhenii gastruliatsii u beskhvostykh amfibii. Soobshchenie I. Destabilizatsiia ooplazmaticheskoi segregatsii i drobleniia pod deistviem klinostatirovaniia.

The yolk segregation in the developing Rana temporaria egg was studied both in vivo and under the effect of clinostate rotation, i. e. slow rotation around the horizontal axis imitating the state of weightlessness. From the moment of fertilization and during the whole period of cleavage the yolk was shown to subdivide succesively in distinct phases which differ by the characteristic value of yolk granules. During the normal development, in spite of the marked variability of form and mutual position of phases, the main elements of their animal-vegetative order are preserved. Under the effect of clinostate rotation the process of normal segregation becomes destabilized and variations in the egg structure are expressed by the beginning of gastrulation in the diversity of variants of distribution of the cellular material competent to different morphogenetic movements.

[Structure of the morphogenetic movements of gastrulation in Anura. II. The elementary morphogenetic processes]. / Struktura morfogeneticheskikh dvizhenii gastruliatsii u beskhvostykh amfibii. Soobshchenie II. Elementarnye morfogeneticheskie protsessy.

The clinostate rotation causes a wide range of gastrulation abnormalities in the Anura. A special investigation has shown that all gastrulation variants may be represented as various spatial-temporal compositions of the same morphogenetic processes isolated by means of formal experimental procedure. These processes are structurally stable rearrangements of tissue morphology and are spread in the tissue as a wave embracing more and more cells. The change of one local morphology for another may proceed either in the form of "shock wave", a moving distinct border between the cells already switched and not yet switched to the new automorphous movement, or in the form of "deployment" when the transition from one local morphology to another is continuously deployed in space.

[Spatial deployments of morphogenetic movements as elements of the oral field in anuran amphibians. I. Structurally stable morphogenetic movements]. / Prostranstvennye razvertki morfogeneticheskikh dvizhenii kak élementov rotovogo polia beskhvostykh amfibii. Soobshchenie I. Strukturno ustoichivye morfogeneticheskie dvizheniia.

The movements of cells in the oral field of anuran embryos were followed by means of orto- and heterotopic transplantations of the ectoderm fragments. To mark individual ectoderm regions, the embryos were used which differed from each other by colour. The cells polarize along the apical-basal layer axis and the polarization spreads along the layer as a waver embracing consecutively new and new cells. The waves of morphogenetic rearrangements from the spatial deploiments of morphogenetic movement, i. e. the transition between the local morphologies of the layer which replace one another in time is swept continuously in space. The presence of spatial sweep is the necessary condition for the structural stability of morphogenetic movements.

[Spatial deployments of morphogenetic movements as elements of the oral field in anuran amphibians. II. The structure of the oral field]. / Prostranstvennye razvertki morfogeneticheskikh dvizhenii kak élementov rotovogo polia beskhvostykh amfibii. Soobshchenie II. Struktura rotovogo polia.

The structure of morphogenetic movements in the oral field of Anura was studied. The movement of any region of the oral field depends on several "elementary waves" of morphogenetic rearrangements, each of them being swept in space along the same cell layer. The waves of morphological rearrangements of cells from different layers are coupled with each other in a stable manner. The cells of the given layer are involved in their morphogenetic movements consecutively, whereas the morphogenetic movements of cells in the interrelated layers are developed in parallel. The waves of morphological rearrangements are those of contact polarization of the cells and, under certain conditions, are spread within several minutes.