THERMAL REQUIREMENTS FOR DEVELOPMENT AND SEASONAL PHENOMENA: IS THE BLUNK FORMULA
APPLICABLE TO THE PHENOLOGY OF AMPHIBIANS? 

Ushakov Mikhail Vasil'evich, Leading engineer, Voronezh State University (1 Universitetskaya square, Voronezh, Russia); “Galichya Gora” Nature Reserve (Donskoe post office, Zadonskii district, Lipetsk region, Russia), E-mail: ushakov@dev-reserve.vsu.ru 

574.24:597.6(470.320) 

DOI

10.21685/2307-9150-2019-2-17 

Background. The Blunk formula describes the dependence of development poikilothermic and ectothermic organism from the temperature. It calculates the amount of heat required for this process. The formula defines a hyperbolic form of the dependence of the duration of development on temperature, which is given by two constants – threshold temperature and the sum of effective temperatures. The herpetological researches show that the relationship of the duration of the embryogenesis stages in amphibians and reptiles from the incubation temperature has a hyperbolic character. It is possible to find the hyperbolic dependence for seasonal phenomena in this group of animals, and therefore the existence of constants. The goal of the study was to establish the thermal requirements for seasonal development on the example of one of the species of amphibians – smooth newt, Lissotriton vulgaris (Linnaeus, 1758).
Materials and methods. The material was the dates of phenological observations of three seasonal phenomena of a smooth newt (“First meeting in spring”, “Spawning start”, “The appearance of young”) and the table of daily average of daily air temperatures collected in 1992–2005 on the territory of the Voronezhsky State Nature Biosphere Reserve. Threshold temperature for seasonal phenomena was determined by the author’s original method presupposing a hyperbolic relationship between the duration of the development and ambient temperature for the “true” threshold temperature and linear relationship in other cases are. Value of the second constant extrapolated when fitting the curve calculated by the Blunk formula to observable data.
Results and conclusions. For all three studied seasonal phenomena was the threshold temperature is set to 0 °C. At the same time, received results show that during the wintering of an amphibian the temperature in shelters apparently was above the threshold. Threshold temperature allowed to calculate regional parameters of seasonal development of newt and the sum of the effective temperatures for each of the phenomena. In this way, phenological events that are a reflection of the seasonal development of amphibians can be described using the Blunk formula. 

Key words

amphibian, smooth newt, Lissotriton vulgaris, seasonal phenomena, threshold temperature, sum of effective temperatures, ecology 

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