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Low-temperature injury in insect tissues and mechanisms of its repair
ŠTĚTINA, Tomáš
While physiological adjustments accompanying insect cold acclimation prior to cold stress have been relatively well explored, processes of recovery after cold stress received much less attention. Using a broad array of physiological, molecular biological and microscopic techniques, I aimed to capture the complexity of processes occurring after the exposure to cold stress in the larvae of two drosophilid species - freeze tolerant Chymomyza costata and freeze sensitive Drosophila melanogaster. Several lines of evidence pointed toward impaired mitochondrial functions in lethally frozen larvae. The freeze-tolerant phenotypes of C. costata retain integrity of mitochondria even after deep freezing.
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Development of resistant life stages and mechanisms of passive dispersal of freshwater copepods
Šliková, Adéla ; Juračka, Petr Jan (advisor) ; Fott, Jan (referee)
Copepods are an important part of metacommunities in freshwater and marine ecosystems. Freshwater copepods occur at all continents and are found in almost every water habitat. These small invertebrates cannot actively disperse among habitats and therefore have to rely on vectors of passive dispersal. Copepods can produce diapause life forms and are therefore able to survive unfavorable conditions during the transport. Throughout the ontogenetic development from an egg to adult stage, they have to pass naupliar and copepodit life stages. Various evolutionary lineages of copepods developed diapause phase at different life stage. Hence it is possible to observe both diapausing eggs as well as diapausing adults. Discussed vectors of passive dispersal are wind, floods, animal fur, animal gut, but also human recreational and industrial activity. This work summarizes basic knowledge about the mechanisms of development of copepods diapausing life stages and about their passive dispersal. Key words: passive dispersal, freshwater copepods, diapause
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Development of resistant life stages and mechanisms of passive dispersal of freshwater copepods
Šliková, Adéla ; Juračka, Petr Jan (advisor) ; Fott, Jan (referee)
Copepods are an important part of metacommunities in freshwater and marine ecosystems. Freshwater copepods occur at all continents and are found in almost every water habitat. These small invertebrates cannot actively disperse among habitats and therefore have to rely on vectors of passive dispersal. Copepods can produce diapause life forms and are therefore able to survive unfavorable conditions during the transport. Throughout the ontogenetic development from an egg to adult stage, they have to pass naupliar and copepodit life stages. Various evolutionary lineages of copepods developed diapause phase at different life stage. Hence it is possible to observe both diapausing eggs as well as diapausing adults. Discussed vectors of passive dispersal are wind, floods, animal fur, animal gut, but also human recreational and industrial activity. This work summarizes basic knowledge about the mechanisms of development of copepods diapausing life stages and about their passive dispersal. Key words: passive dispersal, freshwater copepods, diapause
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Influence of experimental conditions on hatching of diapausing stages of the cladoceran Daphnia obtusa
Sailerová, Martina ; Petrusek, Adam (advisor) ; Vaníčková, Ivana (referee)
Diapause is often an adaptation for survival during periods of harsh environmental conditions. Some diapausing stages do not terminate the dormancy once the favourable conditions are restored. Such prolonged diapause may be enforced by environment if a diapausing stage cannot be reached by the cues inducing termination of dormancy. However, it may also be an advantageous bet-hedging strategy to allow only a fraction of dormant stages produced in any given season to hatch the next time conditions become favourable. I tested whether such strategy can be observed in hatching patterns of dormant eggs of Daphnia obtusa - a cladoceran occurring in small Central European temporary waters. I investigated the influence of intensity of illumination on hatching success, and effect of isolating the eggs encased in ephippia from the sediment. Fraction of eggs terminating diapause, fraction of embryos successfully leaving the egg membranes, and timing of the response were assessed at 15 ˚C under four intensities of illumination (100% = 35µmol.m2 .s-1 , 75%, 50%, 25%; photoperiod 12h light: 12h dark) and in complete darkness for 21 days. My results support previous suggestions that there is no genetically-fixed bet-hedging strategy in D. obtusa. I observed high proportion of eggs which terminated diapause in all...
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Regulation of diapause in the western corn rootworm (\kur{Diabrotica virgifera virgifera} LeConte)
HOUFKOVÁ, Kateřina
The thesis aims to optimize the methods of laboratory culture and to fill in the gaps in knowledge of D. virgifera virgifera ecophysiology. The experiments on embryology and development proved that the diapause of D. virgifera virgifera is of obligatory type and can be terminated by exposure to long-day conditions (20:4; photo : scotophase) and constant temperature of 25 °C. Approximately 10% of eggs completed the development to adults within 4 months. Besides numerous other environmental conditions that are discussed, temperature seems to be a key factor influencing longevity in this pest. Higher temperature of 25 °C prolonged survival by more than 20 days in 2015, compared to 22 °C in 2014.
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Novel roles for the corpus allatum hormone in the cost of sexual interactions in the linden bug Pyrrhocoris apterus
PROVAZNÍK, Jan
The decrease of lifespan by mating is a common, yet poorly understood occurrence. Juvenile hormone (JH) is widely believed to mediate shortened lifespan in insect, caused by mating. In this study we tested the role of JH in the linden bug (Pyrrhocoris apterus) by removal of the corpus allatum gland and thus the JH source. We then proceeded to study the lifespan of mated animals vs. virgin animals. Virgin animals without JH live longer as was expected. The effect on mated animals is however different between males and females. Surprisingly in females, JH seems to lower the cost of mating. In males, on the other hand, the cost of mating seems to be independent on JH levels. Another surprising conclusion is that the level of JH in females affects the lifespan of males that mate with such females.
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Selected ecophysiological characteristics of the new invasive pests in agriculture.
HOUFKOVÁ, Kateřina
The aim of this thesis was to gather and review information on biology and ecophysiology of four invasive species that are considered to be important pests in agriculture. Following species were chosen for the review: Tuta absoluta, Epitrix spp., Ostrinia nubilalis and Diabrotica virgifera virgifera. Experimental part of the thesis consists of ecophysiological and survival experiments conducted on one of the selected species ? Diabrotica virgifera virgifera. The influence of temperature and photoperiod on egg diapause termination was tested in the laboratory. A comparison of adulta survival on three different diets is also included.
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Cold resistance of the water cricket Velia caprai: the influence of acclimation age class and food availability on the supercooling point
NOVOTNÁ, Iveta
Recently, the cold resistance becomes a common topic in scientific articles. If we focus on order Heteroptera, we can find a lot of studies dealing with the cold resistance or with the supercooling point (SCP) and also with the factors that influence them. According to the general rule, the acclimation at low temperatures increases the cold resistance. Therefore, the main goal of this thesis is to find out, whether the acclimation also increases the cold resistance of the water cricket Velia caprai Tamanini, 1947 (Veliidae), with the intention to measure SCP of the water crickets depending on the acclimation temperature and the length of exposure. Due to the high mortality (the 284 individuals remained alive of total 1300) and due to the technical difficulties in measuring of SCP (measured only 36 individuals) it was necessary to modify the original goal of the thesis. The new goal was to test the influence of acclimation (during one month vs. one week) and the influence of different temperatures (0°C, 5°C, 10°C) on SCP of V. caprai. The individuals used for this measurement were collected during the year 2010 and in March 2011. The results of this thesis did not confirm the hypothesis that the acclimation at low temperatures increases the cold resistance. The individuals who were acclimated at a higher temperature have the values of SCP demonstrably lower than the individuals who were acclimated at low temperatures. The individuals who overwinter for the first time have arguably higher cold resistance than the individuals who overwinter for the second time. Probable cause of these results is the fact that the water cricket V. caprai does not start with diapause in the fall but it overwinters in quiescence.
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