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Raci v měnících se biotických a abiotických podmínkách
VESELÝ, Lukáš
Abiotic and biotic factors directly or indirectly influence physiology, behaviour, ecology and the distribution of organisms. This thesis provides unique results in terms of the ability of crayfish to cope with a series of these abiotic and biotic factors. Successful overwintering is key factor facilitating establishment and spread of non-indigenous species. We provide experimental evidence of substantial resistance of three out of four warm water crayfish species to the low water temperatures tested in our study. To sum up, red swamp crayfish together with yabby demonstrated high survival in experimental conditions and exhibited feeding activity even during the coldest part of the experiment. Marbled crayfish suffered high mortality, but a single specimen of survived. Redclaw is expected not to pose a risk for the European temperate zone in the near future. Drought is an important factor for freshwater organisms determining their success in a given ecosystem. One of the strategies how to survive drought are an elevated desiccation capacity and burrowing ability. We evaluated the ability of three European native and five non-native crayfish to survive and burrow in a humid sandy-clayey substrate under a simulated one-week drought. Survival of non-native species was substantially higher, being absolute in the red swamp crayfish and yabby. Red swamp crayfish and marbled crayfish constructed bigger and deeper burrows than yabby and spiny-cheek crayfish. Three native species (noble crayfish, narrow-clawed crayfish and stone crayfish) suffered extensive mortalities. The native species and signal crayfish exhibited no ability to burrow under drought conditions. Marbled crayfish are a successful invader, capable of colonization new habitats. It is also established in the wild of Ukraine and pet-traded in Eastern Europe. If released, it might pose a risk to populations of native crayfish that also inhabit saline ecosystems of the Black, Azov and Caspian Sea. We conducted the first study on salinity tolerance in marbled crayfish. In summary, marbled crayfish are probably unable to invade saline ecosystems due to its low survival, reduced growth and inhibited reproduction. Nevertheless, it showed an ability to withstand the highest salinity for an extended period of time, opening a possibility for its spread to other freshwaters via this corridor. Also, a short generation time might lead to local adaptations to saline environments in the future. Yabby demonstrated an ability to withstand simulated low winter temperatures, opening the question of its potential establishment in the region of Central Europe. To successfully do so, yabby would have to deal with present strains (A, B, and E) of Aphanomyces astaci, a causative agent of crayfish plague, a devastating disease to all crayfish not originating from North America. Our comparative study revealed the ability to survive (strain A) or delay the effects (strains B and E) of crayfish plague compared to native noble crayfish. Our result, highlights a high potential for its establishment in temperate Europe. As a prominent invader, it may cause negative impacts on entire ecosystems and contribute to the spread of crayfish plague in Europe. Nowadays, organisms face multiple global drivers influencing the strength of links in food webs. Altogether, we found that predator identity, prey density, and temperature all affect trophic and non-trophic interaction strengths. Effects of prey density were always independent of temperature and predator identity in trophic as well as non-trophic interaction strength. On the other hand, the magnitude of responses in trophic as well as non-trophic interaction strengths varied strongly across predator pairs and temperatures. Based on the current evidence, we could not find strong support for a general mechanism underlying the dependence of interaction strengths on species traits and environmental conditions. Therefore, other studies are need it.
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Vplyv prostredia a hospodárenia na prezimovanie pavúkov v ulitách suchozemských mäkkýšov
Štempáková, Kristína
The work was aimed at assessing the impact of the environmental characteristics of the site and shells on overwintering spiders in snail shells. Collecting shells took place in winter 2015 and the turn of the year 2015/2016 at eleven anthropogenic and post industrial locations. 889 shells were documented (C. vindobonensis, X. obvia), of which were obtained 146 spiders with the largest representation of interest species: P. tripunctatus, P. nigrociliatus and S. penicillatus. Positive results within the environmental characteristics, brought the presence of low and sparse vegetation, the presence of the bare soil and rock substrate. Sinking shells has proven be negative in this case. Other observed characteristics related to the shells, and management have not been established for determining factors for the selection of shells for the overwintering.
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Vliv podmínek prostředí na pěstování Stévie sladké (Stevia rebaudiana Bertoni)
HAVLOVÁ, Martina
Stevia or Stevia rebaudiana Bertoni are two of the numerous names of this subtropical plant with a sweetening power as much as 300 times higher than in case of sucrose. Stevia is a plant with a very interesting, but up to this date not very utilised potential. The fields of its application, processing, cultivation and wintering options have not been explored very extensively, and therefore I have decided to elaborate this topic related to the impact of the environmental conditions for growing of Stevia rebaudiana. The resources for the text of the diploma thesis were formed by available specialised publications and the Internet. The first part of the thesis represents a brief overview of the whole issue concerning the topic of Stevia rebaudiana. The objectives, hypotheses and methodology of the conducted research, including the findings based on the plant growing as well, and the evaluation of the experiment results have been included in the second part. The purpose of the thesis was to expand the knowledge regarding cultivation, reproduction methods and wintering options of the stevia plants. A field and a greenhouse experiments were staged with a focus on temperature indicators during the growing season and their impact on the total number of wintered plants. Simultaneously, an evaluation of the dry matter yield of the plants per an area unit and statistical processing and evaluation of the experiment results have been performed. Further, a determination of seed germination for Stevia rebaudiana in laboratory conditions has been conducted. The research results have shown that the plants obtained vegetatively are more suitable for cultivation due to a higher yield of the dry matter in both greenhouse as well as field conditions. The only pests invading stevia were the whiteflies appearing only in the greenhouse environment. Variable conditions were arranged for the wintering of the Stevia rebaudiana plants within the experiment; and in spite of the various materials and thermal insulation layers, the plants have not successfully wintered in an unheated environment. On the contrary, in the heated greenhouse space, most of the plants have successfully wintered. The stevia seed germination was low and proves the opinion of the majority of authors. The dry matter yields also matched the yields mentioned in the specialised literature.
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Hibernation of anuran larvae: occurrence, causes and consequences
NOWAK, Rudolf
The bachelor thesis deals with hibernation of amphibians and describes its process in each larval phase. The thesis furthermore describes factors on which hibernation depends and the reasons, which cause it. The main factors for hibernation of animals are temperature and lack of food. Animals have to slow down their metabolism and they survive thanks to their energy reserves. When temperature drops below zero, amphibians protect themselves from freezing with concentration cryogenic compounds, water crystallization in extracellular spaces and preservation liquid cytoplasm inside cells. Hibernation of tadpoles depends on season length, which decreases with increasing altitude and longitude together with decreasing temperature. It is partially caused by thyroid hormones, which controls metamorphosis, because thyroid slows down its function with decreasing temperature. Another stimulation for hibernation of tadpoles is food shortage tadpoles cannot properly grow and develop without food. Dormancy of tadpoles is classified as obligatory and facultative. Metamorphosis after hibernation produces lower risk of mortality during winter and ensures bigger size of a specimen in the following year.
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Comparison of survival, growth rate and overall breeding of grass carp (Ctenopharyngodon idella) juveniles in pond and recirculating aquaculture system during winter time.
PECHER, Petr
The study compared survival and growth rate in grass carp (Ctenopharyngodon idella) juveniles in pond and recirculation aquaculture system (RAS) during winter time. The juveniles of grass carp were stocked to 5 tanks and three ponds during 2013 and 2014. In the RAS, the fish were fed by dry pellets and rearing was in constant temperature. In the pond, the temperature and feeding were only natural. In the RAS, the survival rate was significantly higher 97.79 % 0.52 % compared to 10.94 % 11.42 % in the pond. At the end of experiment, the weight of fish, Specific growth rate (SGR) and Fulton coefficient (FK) was significantly higher in RAS in comparison with the pond. The results showed that the rearing of grass carp is more effective in RAS in comparison with pond during winter time.
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Bezstavovce prezimujúce v ulitách suchozemských mäkkýšov v širšom okolí Vranova nad Topľou (Slovensko)
Štempáková, Kristína
The main aim of this work was the overwintering of spiders in land -- snail shells in vicinity of town Vranov nad Topľou. Collecting of these shells was carried out in the wintertime at the turn of 2012/2013 and 2013/2014. For the detection what species of spiders are overwintering there, were shells stored at room temperature. The outgoing species were caught, inserted into tubes with alcohol and determined later. From 1085 collected shells (Xerolenta, Cepaea, Helix), 116 spiders were obtained about 11% of the shells were inhabited. Thus, shells represented important refuge, as well as a way to hibernate, and oftentimes these shells are inhabited by rare or endangered species.
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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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