[The correlation between the heat resistance of the zygotes of the common frog Rana temporaria and its embryos at different developmental stages].

A study has been made of a correlation between the heat resistance of zygotes and embryos of the same clutches at different stages of development of Rana temporaria L. The embryos were incubated at 19 degrees C, the injurious temperature being 37 degrees C. As criterion of heat resistance served the time of the injurious temperature action which leads by the ++stra of cleavage to a 50 per cent elimination of embryos (LD50).

[Effect of the temperature of oocyte maturation on the heat resistance of the body and cells in the progeny of the common frog].

A study was made of the effect of low (4-5 degrees C) and high (17-22 degrees C) temperatures of oocyte maturation on different stages of development: a unicellular stage, early tadpole stage 39 and late tadpole, near the end of metamorphosis stage 52. Different temperatures in the course of oocyte maturation do not lead to reactive shifts in heat resistance of the organism and muscle cells of the progeny on either developmental stage examined.

[Correlation between the heat resistance of the provisional and definitive muscle tissue during the metamorphosis crisis in frogs].

Using tadpoles of the lake frog Rana ridibunda Pall. during metamorphosis, a study was made of the heat resistance of the provisional muscle tissue of the tail and of that of two definitive muscles belonging to low-resistant (musculus iliofibularis) and high-resistant (musculus gastrocnemius) groups. It has been shown that during the late metamorphosis a statistically significant direct relation exists between the heat resistance of the provisional muscle tissue of the tail and definitive m.

[Effect of thermal selection of the male gametes on the resistance to temperature and chlorophos of the body and muscles in tadpoles of the common frog].

A study was made of the effect of thermal selection of parental spermatozoa on the heat resistance of the whole organism and of muscles in progeny of Rana temporaria, as well as of the organismal resistance to pesticides (0.0025 M chlorophos). The thermal selection of spermatozoa was performed by exposing their suspension to 36 degrees C for 30-40 minutes.

[Thermal selection of zygotes and heat resistance of the body and muscle tissue in tadpoles].

A study was made of the group (family) thermal selection of zygotes for heat resistance of the organism and muscles of the grass frog Rana temporaria L. at the initial and final stages of development. The average duration of thermal effect (37 degrees C), followed by a 50% lethality of affected zygotes (LD50), served a criterion of heat resistance of zygotes in each particular single clutch.

[Dynamic study of the level of muscle heat resistance of tadpoles in different clutches of the common frog at various stages of development].

A study was made of the relation between the heat resistance levels of muscles of tadpoles examined from the same clutches at different stages of development: soon after hatching (stage 39), at one of the growth period stage (stage 42), at the completed growth stage (stage 50), and at one stage of the metamorphosis proper (stage 52). As a criterion of the resistance served the time of the loss of tail muscle contraction in response to the electrical stimulus (50 hz frequency) at 38 degrees C. It was found that in 10% of clutches only the pattern of changes in the heat resistance level of tadpole muscles coincided with the average population pattern.

[Relationship between the heat resistance of different muscles and frog viability during heat selection].

An attempt was made to elucidate the relation between the survival of mature frogs Rana temporaria during sudden (unforeseen) thermal selection and the heat resistance of several muscles: m. interfalangealis, m. ileofibularis, m.