[Heat resistance of the skeletal muscle in western palearctic green frogs (Rana esculenta complex)].

Heat resistance of the gastrocnemius muscle was studied in five species of the Rana esculenta complex. It was similar in R. bedriagae, R. lessonae, and in the European form of R. ridibunda; while North African R. saharica demonstrated a lower heat resistance. No heterosis was expressed in R. esculenta, a clonal hybrid of R. lessonae and R. ridibunda, for the heat resistance of the muscle. Moreover, this species demonstrated low heat resistance at the highest test temperatures (42 degrees C). Comparison of diploid and triploid R. esculenta syntopically occurring in the same water bodies demonstrated no heat resistances between them, thus, suggesting that polyploidy has no effect on this parameter at least in this case.

[Variation of microsatellites BM224 and Bcal7 in populations of green toads (Bufo viridis complex) with various nuclear DNA content and ploidy].

We studied variation of microsatellites BM224 and Bcal7 in three species of the Bufo viridis diploid-polyploid complex. We found that locus Bcal7 in all examined samples was monomorphic. Three alleles of microsatellite BM224 were found. Among tetraploid toads, the western species B. oblongus had only one allele variant, whereas the eastern species B. pewzowi had two other alleles. Similar distribution of alleles was observed in triploid specimens, collected in the area borders of tetraploid and diploid species. Among samples of diploid toad B. viridis, we found all three allele variants of microsatellite BM224. Their distribution was geographically determined. A comparison of allele distribution with genome size variation in diploid toads showed very similar patterns.

[Genetic variation in two forms of the common spadefoot toad Pelobates fuscus (Pelobatidae, Anura, Amphibia) distinguished by genome size]. / Geneticheskaia izmenchivost' u dvukh form obyknovennoi chesnochnitsy Pelobates fuscus (pelobatidae, anura, amphibia), razlichaiushchikhsia po razmeru genoma.

Genetic differences (presumed 23 loci) between two cryptic forms of Pelobates fuscus, differing in genome size, were examined by means of polyacrylamide-gel electrophoresis. This method allowed to discriminate between these forms. Average genetic distance (DN) between both the forms was equal to 0.311, ranging from 0.055 to 0.563. As a rule, differences within these groups were smaller (0.021-0.388). The data show obvious genetic differentiation between these two cryptic forms of P. fuscus. Differences between these forms and P. syriacus were significantly higher (in average 0.943). Genetic distances in relation to speciation and species concepts are discussed.

[Differences in muscle thermostability between diploid and tetraploid species of green toads (Bufo viridis complex) of Middle Asia]. / Razlichiia v termorezistentnosti skeletnykh myshts mezhdu diploidnym i tetraploidnym vidami zelenykh zhab (Bufo viridis complex) Srednei Asii.

Significant differences were found between diploid (Bufo viridis) and tetraploid (B. danatensis) toad species in their skeletal muscle thermostability. The lower muscle thermostability in tetraploids may be associated with the adaptation of B. danatensis to colder conditions of arid mountain area in the Middle Asia.

[RNA and protein content in cells of diploid and tetraploid toads of the Bufo viridis group]. / Soderzhanie RNK i belka v kletkakh diploidnykh i tetraploidnykkh zhab gruppy Bufo viridis.

Nucleic acids and total protein contents in hepatocytes and erythrocytes of diploid (Bufo viridis, 2n = 22) and tetraploid (B. danatensis, 2n = 44) green toads were measured cytophotometrically. The RNA (table 1) and protein (table 2) contents in the tetraploid cells are twice as much as that in diploid ones. According to these results tetraploidy in green toads may have a recent origin. The relation between structural and functional polyploidization in tetraploid amphibian species is discussed.

[Elimination of the genome of one of the parents prior to premeiotic DNA synthesis in a hybridogenic species of Rana esculenta]. / Eliminatsiia genoma odnogo iz roditelei do premeoiticheskogo sinteza DNK u gibridogennogo vida Rana esculenta.

A DNA-cytometric study was made of spermatogenesis of the hybridogenic European green frog R. esculenta, whose somatic cells have the ridibunda + lessonae genome. The DNA amount in the ridibunda genome is by 16% more than the lessonae one. The DNA content of esculenta somatic cells is exactly intermediate between those of both the parental species. On the contrary, the sperms (1c) and the primary spermatocytes (4c) of R. esculenta have the DNA content which corresponds to the size of the ridibunda genome. These findings are in a good agreement with the hypothesis of semiclonal inheritance. Furthermore, some hybridogenic males have also spermatogonia (2c) with only the ridibunda genome size, whereas the others have altogether diploid cells with the esculenta (i.e. ridibunda + lessonae) genome size. So, it can be suggested that the selective elimination of the lessonae genome and compensatory doubling of the ridibunda one may occur in spermatogonia of R. esculenta males before the premeiotic DNA synthesis. Meiosis, as it can be inferred from the DNA-cytometry data, proceeds in a usual way on the basis of the ridibunda genome.

[Structural differences in the collagens of Rana frog species with dissimilar temperature ecology. The contribution of carbohydrate components to collagen molecular thermostability]. / Strukturnye razlichiia kollagenov u nekotorykh vidov liagushek roda Rana s neodinakovoi temperaturnoii ékologiei. Vklad uglevodnykh komponentov v termostabil'nost' molekul kollagena.

Skin procollagens in two species groups of frogs of the genus Rana - brown frogs (4 species) and green frogs (3 species) distributed in European and Asiatic parts of the USSR have been compared. A geographic intraspecific variation in collagen characteristics (two geographic populations of the pond frog Rana nigromaculata) is revealed. Intergroup differences in the thermal denaturation of collagens established by means of methods of circular dichroism and microcalorimetry are significant. Such differences within both the groups are not so visible. With the species studied, carbohydrate components contents in procollagen vary. Interspecific differences in the procollagen thermostability correlate with the thermal ecology of frogs and seem to be associated with the availability of carbohydrates.