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Individual growth and variability of early development stage of creeping water bug Ilyocoris cimicoides (Heteroptera: Nepomorpha:Naucoridae)
PILAŘOVÁ, Simona
This thesis investigates an influence of environmental variables (temperature and food availability) on development and growth of the first three nymphal stages of Ilyocoris cimicoides Linnaeus, 1758 Individuals were housed individually in experimental cages from eklosis into adulthood. Experiments were carried out in a combination of four different temperatures (17 ?, 19 ?, 22 ? and 25 ? C) and two different modes of food availability (full-fed every day, red-fed every other day) (in eight treatments). The temperature significantly influenced the length of nymphal development. According to our expectation, shortest development was achieved in individuals reared at 25° C. Development period was prolonged by decreasing temperatures. Unpredictably, the nymphs of the 3rd instar had longest development at the lowest temperatures (17 ? C) whereas nymphal development of the 1st and 2nd instars ran faster Both, the lowest- (17 ? C) as well as the highest used temperature (25 ? C) are probably very close to the temperature limits, that corresponds to the limits of postembryonic development. The optimum temperature for development was 22 ? C. Furthermore, it has been found that food availability should also significantly affect growth and development. Surprisingly, less mortality was observed in individuals reared in reduced feeding treatment, except the only case - nymphs reared in low temperature (19 ? C), where higher mortality was found in individuals reared at the same food availability.
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Is it possible to demonstrate selection in science teaching? Simulation of natural selection in a model organism.
MARVANOVÁ, Aneta
This thesis examines the effect of natural selection on the rate of development of Microvelia reticulata. Natural selection is an integral part of evolutionary biology. The main task was to determine whether the selection of the developmental rate reflected in the change of development. Selected individuals were reared in the same conditions from egg to imago in a total of three replications in a strain selected for rapid development, slow development and unmanipulated control. There was distinct increase in developmental rate between initial and first selected generation all replications of control strain, followed by slight decrease in all succeeding generations. Similar pattern was present in the strains selected for slow development. A comparably distinct increase in developmental rate appeared also in the strains selected for the fast development, but it was not followed by succeeding slowdown, or the slowdown of the developmental rate was not as remarkable as in other strains. According to not too convincing results and remarkable time and space demands of this research, it is unreal to run similar long-term experiment in school conditions. Research was supported by project of the Grant Agency of the Czech Republic no. P505/10/0096.
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Development, growth and variability of semiaquatic bug Microvelia reticulata (Heteroptera: Gerromorpha: Veliidae)
VOJTOVÁ, Lucie
I investigated the effect of environmental factors (temperature and food availability) on the development and growth of semiaquatic bug Microvelia reticulata Burmeister, 1835. I focused on the developmental rate isomorphy. In a cross-designed experiment, M. reticulata was individually kept over whole juvenile period (eggs to reaching maturity) and subjected to treatments of three temperature (17, 21, 25 °C) and two food availability (full - daily feeding and reduced - 2 days interval) and their interaction. Development and growth was strongly influenced by temperature. Longest postembryonic development measured in individuals kept in the lowest temperature (54 days) contrasted to those kept in the highest temperature (16 days). Mortality was also significantly influenced by temperature; highest mortality rate was found in the 17 °C treatment. Effect of food availability was significant only in low temperature, resulting in the better survival of individuals on the high food level. In other temperature treatments, I found no effect of food on survival rate of M. reticulata. However, the food level influenced development significantly. In the 21 °C and 25 °C treatment, individuals on a full food developed faster than individuals on a reduced food. In 17 °C the food availability had no effect on time required to reach maturity. The best fitness (expressed as combination of low mortality rate and short development) was observed in 21 °C, both other temperature treatment were found stressing. Food availability had stronger effect on female individuals compared to males. In conclusion, I found no evidence of developmental rate isomorphy in M. reticulata. The research was supported by project of the Grant Agency of the Czech Republic GAČR P505/10/0096.
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Cold hardiness of larvae of the fruit fly, \kur{Drosophila melanogaster} (Diptera: Drosophilidae)
KORBELOVÁ, Jaroslava
We assessed survival of larvae of the fruit fly, Drosophila melanogaster at low temperatures (0°C and 5°C) after rearing them under seven different acclimation regimes. Larvae that have developed in a standard diet at 25°C showed 50% mortality after 12,6 min of the exposure to 0°C (Lt50 = 0.21 h). In contrast, larvae that have developed in a diet enriched with glycerol at 15°C, and were cold acclimated at 5°C during last two days of their development, had Lt50 = 38.6 h. It means that it was possible to increase the Lt50 at 0°C more than 180-fold using simple manipulations with rearing temperatures and diet composition. The physiological differences in duration of larval development, fresh mass, dry mass, hydration and total contents of proteins, lipids and glycogen between the larvae belonging to different acclimation variants are described. The samples for future detailed metabolomic analysis were prepared.
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Effect of selected abiotic factors on wing polymorphism of semiaquatic bug Microvelia reticulata Burmeister, 1835.
ČERMÁKOVÁ, Táňa
Wing polymorphism of semiaquatic bugs is affected by environmental factors as temperature, photoperiod, population density or permanency of habitat. The heritability has its own specific part, too. A lot of field studies suggest that crucial effect on wing polymorphism has temperature, but laboratory experiments often do not confirm this hypothesis. The main aim of this thesis was to describe the effect of environmental factors (photoperiod, temperature and permanency of habitat) on wing polymorphism of Microvelia reticulata, additionally of Gerris lacustris. The partial tasks included description of effect of mentioned abiotic factors on mortality and rate of development. The individuals of both species were kept at combinations of two levels of temperature, photoperiod and permanency of habitat (overall at eight treatments) from first larval instar to adult. All adults of Microvelia reticulata emerged as apterous, so there was no response of wing polymorphism to tested environmental factors. The main influence of heritability is presumable. Only ten individuals of G. lacustris developed into the adult stage, so it was impossible to describe the influence of abiotic factors on wing polymorphism, mortality and lenght of development in this species. Mortality of individuals of M. reticulata was significantly influenced by the type of substrate. Only 3.5% of individuals survived when reared on wet filter paper, while 80.5% on the water surface. Both other factors (temperature, photoperiod) had no effect on total mortality. There was no difference between mortality of males and females, so it is impossible to note sexual dependent mortality. The lenght of development did not differ between sexes either. Lenght of development was significantly affected by temperature, as low temperature reduces development of M. reticulata. The fastest development showed nymphs of second instar and slowest development nymphs of fifth instar at all treatments. Since the effect of abiotic factors on wing polymorphism was not found in M. reticulata, it would be sufficient to study the effect of heritability on development of wings in this species in the future.
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