Zjawisko rytmu rocznego u płazów

Abstract

In Part I the author discusses the importance of studies on the annual rhythm in amphibians from the point of view of General Biology, and the main difficulties in the carrying out of investigations. These investigations require special methods which ensure that they are carried out on suitable material coming directly from a natural environment and corectly representing the population of a particular species at appropriate intervals of time during the whole year. Then, on the basis of the annual rhythm in the amphibian, a biological and ecological description of the amphibians living in Poland is given. Here are discussed the main vital environment, the mating season ,the period of active life and hibernation in amphibians, and especially in the common frog (Rana temporariia L.) which is the standard subject of investigations on the annual rhythm in these animals. Many biological and ecological groups among Polish amphibians are distinguished on the basis of this description. One of the main elements of investigations on the annual rhythm in amphibians is the description of the climate and meteorological conditions which prevail during the year in the area from which the population of the amphibian species investigated comes. In this connection the main climatic factors are presented, viz., the atmospheric temperature, rainfall, insolation, and also the water temperature in the case of the interpretation of the life processes of the amphibian, which take place in a natuural reservoir of surface water (ponds, streams). The annual course of the mean decadal atmospheric temperatures, the amplitude between the mean decadal maximal and minimal atmosferic temperatures, and the mean decadal snowfall and rainfall were analysed over the twenty-five year period of investigation, and the connection between the occurrence of these factors and the life of an amphibian was shown. Such life processes as waking from the „winter sleep”, the mating season, migration (especially in the autumn), and the beginning of hibernation are primarily taken into consideration. A time-table of the periods of study in investigations on the annual rhythm in amphibians has been established on the basis of these phenomena. This includes the main life processes of the amphibian and facilitates the comparison of the results of studies made on various species of these animals. In Part II are given the results of investigations on the annual rhythm in the common frog (Rana temporaria L.) and in some other amphibians, on the basis of the literature and the author’s own experiments. The results cited are presented as graphs, supplementing the curves with a corresponding standardized ecogram of the comon frog. The experiments discussed are concerned with the cyclic changes of such organs as the lungs, skin, haematopoietic system, thyroid gland, ovaries and oviducts, testicles, and alimentary canal. These investigations show that that in the organism of an adult amphibian there occur characteristic morphological and physiological changes in various organs, but for each of them these take a specific course in the annual cycle. These changes are shown in the regular appearance of a maximal and minimal degree of development or functioning of a particular organ at certain periods of the year peculiar to it. The functioning of the vegetative organs shows, in general, a directly proportional dependence to the typical course of the atmospheric temperatures during the year, which is in accordance with van t’Hoff’s law; the functioning of the reproductive organs shows an inversely proportional dependance, and so is not in accordance with van t’Hoff’s law. The course of the cyclic, changes in the organism of the amphibian is clearly and basically connected with mating season and the laying of the eggs, because it is at this time that most of the organs examined reach their maximal development, or the intensification of their functioning in the yearly cycle. Hibernation in the amphibian is not a state of complete rest of the organism, for some organs, especially the reproductive glands, reach their maximal development at this time. The cyclic changes in the organs are regulated by a specific hormonal „physiological clock”, and stimulated by some external factors, such as the temperature of the surroundings, the amplitude of these temperatures rainfall, insolation, etc. The annual rhythm is the main biological regularity of the whole metabolism of the amphibian.