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Comparison of individual variation at 24 biochemical loci in members of the species complex of Palearctic green toads showed that the heterozygosity of the tetraploid species Bufo danatensis (Hobs + 0.45) was significantly higher than that of the diploid species B. viridis, B. sp., and B. raddei (Hobs = 0.009 - 0.103). Such difference can be explained only by a hybrid origin of the tetraploid species. Individual electrophoretic variability of the polyploid toad species is associated with an allelic variation that is manifested in constantly heterozygous spectra as the gene dosage effect. At the population level, this phenomenon found in Pamir toads is caused by irregular meiosis in founders of the population or by directional changes in gene regulation. Genotypic distributions in zones of contact of the diploid and tetraploid taxons demonstrate the possibility of restricted introgressive hybridization.
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The mesonephretic blastema is formed by cells with a large nucleus, a dense cytoplasm containing few differentiated organelles. At the contact between the ureter and the mesonephretic blastema, the cells of the primary ureter have special characteristics: existence of an abundant "coat", numerous "villous processes" and a dense network of fibres of collagen.
In early stages of development, the sub-aortic blastema is formed by cells of a uniform appearance filled up with lipidic inclusions. As early as stage 36, four different types of cells are present; numerous leucocytes, cells with mitochondria with tubulo-vesicular saccules, cells with granules, and cells with dense cytoplasm.
A comparative study of proteinograms and zymograms (LDH, MDH) has been carried out at different ontogenic stages, in Ambystoma mexicanum (A.m.), Ambystoma dumerilii (A.d.) and nucleocytoplasmic hybrids 2 n A.d/cytoplasm Am. It appears that 2 n A.d. nucleus, grafted in A.m. cytoplasm expresses only a part of its potentialities, which could account for lethality of the nucleocytoplasmic hybrids.
The formation of myosepts of the toad is characterized by three stages in early development. At the first stage, the somitic cells give off some pseudopods and many collagen fibres. At the second stage, the newwork of collagen fibers grows denser but pseudopods retract. In the end, at the third stage, the collagen fibres disappear and secreting fibroblasts are seen in the myosepts.
The experimental results of cranio-caudal reversal and dorso-ventral reversal of the lateral mesoblast of the toad early neurula prove that, at this stage, the cranio-caudal polarity of this tissue is fixed but not the dorso-ventral one. External factors are responsible for the formation of mesonephric, adrenal and gonadal medullary anlage by the lateral mesoblast.
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The retinal projections of Discoglossus were examined on sixteen adult specimens uniterally deprived of retina. After a post-operative period of nine to one hundred and fifteen days, the degenerating fibers were stained with the Fink-Heimer and Ebbesson-Heimer techniques. The general scheme of primary optic pathways and centres is similar in Discoglossus and Rana. However, after a thorough study, some differences in distribution and density of degeneration suggest the idea that Ranid's visual system is not entirely representative among the Anura. Particularly, degenerative axonic terminals are abundant in ipsilateral Bellonci's neuropil, Corpus geniculatum and pretectal neuropils.
At early neurula stage of the toad, cranio-caudal and dorso-ventral reversal of lateral mesoblast is performed. The genito-urinary system is therefore missing after this intervention. The three following factors of the formation of this system anlage are anlyzed: lateral mesoderm competence, stimulative activites of dorso-caudal endoblast on the one hand, of chordo-mesoderm on the other hand.
Population-genetic analysis conducted in hybrid populations of Rana esculenta complex from neighbourhood of Kiev has shown a high portion of recombinant frogs within Rana esculenta specimens and limitation of gene flows from one species to the other. The mechanisms of limitations are connected with assortative crossings within R. ridibunda and R. lessonae and low viability of frogs with a recombined genotype.
Transfer of cytoplasm had been made between virgin eggs of two species, species with very different times between activation of the eggs and the first cleavage. The first furrow appears on an average of 6 hrs. after activation in Pleurodeles eggs and 2 hrs. 30 min. in Xenopus eggs. Slow cleaving P. waltlii cytoplasm introduced in quickly cleaving X. laevis eggs acted by delaying the formation of the first cleavage furrow, which appeared more than an hour after Xenopus controls. An opposite effect was obtained with Xenopus cytoplasm in Pleurodeles eggs. Cleavage furrows were obtained 2 hrs. before Pleurodeles controls. The cytoplasmic effect involved in the control of rhythms of cleavage could be related to a clock system.
The protein synthesis manifested by aggregates of blastula and gastrula dissociated cells were studied by means of polyacylamide gradient gel electrophoresis. This method permits a comparative analysis of protein electrophoretic mobilities in aggregates and controls. In all cases, the data obtained establish the identity of protein banding and confirm an egg laying polymorphism.
The larval thyroid of Xenopus cultured in an adequate medium, keeps its morphological differentiations at an ultrastructural scale and reacts against TSH added to the culture medium, through the development of apical microvilli, which is a sign of an active pinocytosis of the colloid, and also of ergastoplasmic lamellar and vesicular structures suggesting an active protein synthesis.
The changes motor activity in the frog Rana lessonae in clean water depends on the type amino acids, stimulating chemoreceptors. Reactions orientations (as reaction of recognizing) in adult frog are caused by only amino acids constantly present in ponds water, while amino acids, only periodically appearing in ponds water, are not caused. Amino acids with more short chains of carbon atoms in the molecules (C3-C4) are more effective (with significance p < 0.01) in change motor activity, than amino acids with more long chains (C5-C6) of the molecules. This law is characteristic (on literature by data) for reactions of taste receptors in fishes. It is possible that chemoreceptors of Rana lessonae, perceiving amino acids and initiating changes in behavior this animal, resembles the taste receptors in fishes.
Water homeostasis is ensured in vertebrates through neuroendocrine reflexes involving hormones and specialized exchange organs depending whether the habitat is freshwater, sea or land. Amphibians have a development recapitulating two adaptive programs, first a freshwater fish program as a tadpole, then a land vertebrate program as an adult. The second, however, is imperfect because of the great evaporative water loss through the skin when the animal is in the open air. This loss must be compensated by water reabsorption through the nephron, the urinary bladder and mainly by water uptake through the skin. Water reabsorption by the nephron is not as efficient as in higher vertebrates but water uptake through the skin is crucial because adult amphibians, like tadpoles, do not drink. Adaptation occurred at the level of three organs, nephron, urinary bladder and skin whose permeability is under control of specific hormones. Aside from vasotocin, active on these three organs, differential maturation of provasotocin led to processing-arrested intermediates, namely vasotocinyl-Gly in virtually all anuran amphibians and vasotocinyl-Gly-Lys-Arg in Xenopus laevis. These intermediates result from a down regulation of the alpha-amidating enzyme or carboxypeptidase E, respectively. They have been termed hydrin 2 and hydrin 1 because they are endowed with hydroosmotic properties equal or superior to those of vasotocin on the skin and the bladder. However, in contrast to vasotocin, they are devoid of antidiuretic activity. Adaptive evolution has created, aside from the osmoregulatory vasotocin-nephron system that was preserved in strictly terrestrial nonmammalian tetrapods, additional functions such as the hydrin-skin and the hydrin-bladder rehydrations with specific messengers and organs. The adjuvant systems disappeared in true land vertebrates because the vasotocin-nephron system became more efficient.
Analysis of the genetic structure of two green frog Rana esculenta complex populations from Volyn' was performed for 7 diagnostical loci. Populations of R- and REL-type were detected in which the introgression of Ldh-B allelic gene locus from R. lessonae into genome of R. ridibunda, characteristic for hybrid populations of Dnieper basin, was absent. This may be associated with alterations in gene pools of parental species.