Efekat elektromagnetnog polja (50 Hz, 0,25 mT) na komponente adaptivne vrednosti i morfometriju krila kod Drosophila subobscura Collin, 1936 (Insecta, Diptera)
The effect of electromagnetic field (50 Hz, 0.25 mT) on fitness components and wing morphometrics of Drosophila subobscura Collin, 1936 (Insecta, Diptera)
Doctoral thesis (Published version)
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Since its beginning, the life on Earth has been evolved in the presence of natural electromagnetic fields (EMFs) which are relatively simple and and with few EM energy emitters. During their evolution living organisms have well adapted to this constant environmental factor, but in nowadays, they are being increasingly exposed to artificial EMF’s. The intensity and frequency of these fields are far higher than in the fields of natural origin, and includes mostly EMP power frequency (within the spectrum of extremely low frequency (ELF) of 50 or 60 Hz), fields originating from the unit of mass (radio and television transmitters, 100-500 MHz) and mobile communications (800-900 MHz and 1800-2200 MHz). The ELF EMFs have great biophysical significance since they are part of ubiquitous electric power transmission and consumption. The artificial EMF’s have been a subject of various biological studies, focused mainly on the effects to human health. Exposing organisms to ELF EMFs, even for a short period, results in a disturbance of equilibrium of biological systems, as well as in disorder/disturbance on different levels of the organization. Nevertheless, there is no generally accepted theory about the ELF EMF mechanisms and their effects on biological systems. Furthermore, environmental changes caused by ELF EMF can have an effect on ecological and evolutionary processes that affect the level and extent of genetic structure and evolutionary changes within a population. Therefore, it is of utmost importance to not only thoroughly understand the mechanisms that enable organisms to adapt to environmental challenges, but to anticipate and observe populations’ responses to environmental changes. In the last three daecades, there have been numerous biological studies on ELF EMF effects on Drosophila. The results of exposing Drosophila individuals to ELF EMF during different life stages are often contradictory because the ELF EMF effects on growth and metabolism can be either inhibitory or stimulative depending on the complex relations between the frequency, field intensity, exopusre duration, and condiotion and type of cells or organisms. There are many data on ENF EMP effects on development, fecundity, viability, and other fitness components observed on Drosophila in laboratory conditions. Nevertheless, the ENF EMP, being one of the ubiqutous abiotic environmental factors, can affect populations’ genetic structures and levels of populations’ genetic variability. This kind of the genetic variability can serve as a basis for other evolutionary mechanisms within a population. The goal of this research is to analyse the effects of ENF EMP, complex environmental factor, on a populational-genetic level. The experiment evaluates network of phenotypic responses to ELF EMF by using the genetic variability of IF lines whitin population of D. subobscura. Analized phenotypes describe delicate cooperation between genotype and the environment, emphasizing the importance of their interaction for population survival in the conditions of stress, to which the individuals/populations are exposed during the generations. Individuals of D. subobscura were exposed to ELF EMF of 50 Hz and 0,25 mT in embryonal and early post-embryonal developmental stages during three successive generations. The results of fitness components analysis showed that individuals responded to exposure with ELF EMF already in the first generation. The response was reflected in longer embrionic development (egg-to-adult), lower survival, shortening of longevity, and by the trend of fecundity increase in stressful conditions, when compared to individuals of the control group whose development was completed outside of the EMP. In the third generation, individuals exposed to EMF also had lower survival and shorter life span, but their development was faster, while fecundity showed trend of decrease, when compared to control individuals of the corresponding generation. Average values of fitness components decreased through generations, which can be observed in particular by lowered survival through generations of individuals exposed to 50 Hz and 0.25 mT EMF. The results also show that the effect of EMF ELF is cummulative during generations. Phenotypic correlations of fitness components indicate that EMF ELF as an environmental factor affects covariation of the analized traits by changing the direction and by lowering the degree of trait interconnection. Exposed individuals from second and third generation show variation of phenotypic plasticity of developmental time, which can be important for adaptation to artificial EMF ELF. By varying the developmental time, individuals of the analized IF lines, which can differ in sensitivity and physiological mechanisms of response to environmental factors, partially compensate environmental stress caused by EMF ELF. The effect of ELF EMF on individuals of D. subobscura exposed during embryonic and early post-embryonic development, is reflected through the change of wing size as well, but not through the wing shape. Individuals of both sexes exposed to an artificial EMF ELF in first generation had larger wings compared to control group individuals. Contrary to that, in exposed individuals of the third generation there has been a decrease of wing size . Change of wing size of the exposed individuals during three generations is the indicator of the EMF ELF effect on developmental processes during embrionic and larval phase. The results also show that the effect of EMF ELF on developmental mechanisms changes final phenotype of individuals as well. The results showed that EMF ELF represents environmental factor which influence growth, development and fitness of D. subobscura individuals. Therefore, on a population level this factor can represent selection pressure for fitness components, phenotype and population genetic variability. Analized effects of 50 Hz and 0,25 mT EMF on population level are reflected in the decrease of particular fitness components of D. subobscura population, and by that in the ability of population to adequately respond to added and/or future changes in the environment. Based on all the evidence presented here, the conclusion is that ELF EMF can be clasified as a stressongenic factor of the anthropogenic origin.
Keywords:Extremely low frequency (ELF); Electromagnetic field (EMF); Drosophila subobscura; Fitness components; Geometric morphometrics; Phenotypic plasticity
Source:University of Belgrade, Faculty of Belgrade, 2016, 1-170
- Dynamics of gene pool, genetic and phenotypic variability of populations, determined by the environmental changes (RS-173012)
- Program of basic research #143014: "Adaptivni značaj genetičkog polimorfizma populacija Drosophila"