[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. In some clutches one could observe that the lower the heat resistance level of the clutch at the previous stage the higher its increase during the transfer to the next stage, and vice versa. A suggestion in put forward about the role of changes in heat resistance of tadpole muscles in the maintenance of the population's conservation by this character in poikilotherms.