Master of Music - Music / The Czech guitarist and composer Stepan Rak (b.1945) has produced major works for the guitar, many of which stretch the boundaries of guitar technique and composition in new directions. This research report provides a musical transcription of one of Rak’s most ambitious pieces, Tracy (1994), based on the cyclone of that name which devastated the town of Darwin, Australia on Christmas Eve 1974. Rak uses rasgueado and tremolo techniques exclusively in Tracy. This report also contextualises the composition in terms of Rak’s life and musical output, and provides a detailed description on the execution of these techniques and a general analysis of the pieces technical, formal and compositional characteristics.

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The ultrastructure of spermatozoa from six crayfish species were described. The acrosome complex and nucleus are located at the anterior and posterior of the spermatozoon, respectively. The acrosome complex organelle is divided into two main parts: the main body of the acrosome that is a dense inverted cup-shaped structure and organized into three layers of differing electron densities and extended parallel filaments, and the sub-acrosome zone occupying the central part of the acrosome complex, which is divided into two electron dense areas. The spermatozoon of Orconectes limosus is described for the first time. In addition, an acrosome spike in the spermatozoon of Procambarus clarkii is described. Despite a well conserved general structure and similarity of pattern among these spermatozoa, differences in the dimensions of the acrosome within the studied species may be useful to help distinguish the different crayfish. The ultrastructure of the spermatozoon and spermatophore wall of the narrow clawed crayfish Astacus leptodactylus during three stages including freshly ejaculated, post-mating, and after release of the spermatozoon were described and compared. The crayfish spermatophore consists of a sperm mass enveloped by a three layered spermatophore wall. After mating, the thickness of the outer layer of the spermatophore is increased. The matrix in the middle layer of the spermatophore becomes reticulated, and granules inside this layer release their contents. Fibers in the inner layer degrade to small particles. The spermatozoon capsule swells and space between the capsule and the spermatozoon appears. The area of the plasma membrane is increased by wrinkling of the surface and alteration from a single to a multilayered structure at the anterior part of the acrosome. The density of the subacrosome zone increases in the vicinity of the main body of the acrosome. With the onset of fertilization, the layers of the spermatophore are dissolved by female glair glands secretions. The capsule, plasma membrane, and membranous lamellae are eliminated, and bundles of filaments are released. The subacrosome zone loses electron density and retracts. The electron-dense material of the innermost layer of the acrosome is discharged and, together with filaments, forms a filament/droplet structure at the anterior part of the spermatozoon. The most important change is observed in the subacrosome zone, which may play a key role in the fertilization. Also, morphological changes of the spermatozoon after release from the capsule, especially formation of the filament/droplet structure, may contribute to the mechanism of egg-spermatozoon binding in the crayfish.

Human activities have largely impacted the environment and its biota to the extent that biodiversity declines can be seen worldwide. Biological invasions significantly contribute to these processes. Slovakia is a rapidly developing country stretching along the northern parts of the Pannonian basin and western Carpathian Mountains. Geological characteristics predetermine its extraordinarily high species richness thanks to largely preserved regions and habitats of high biological and conservational value. As a result, a strong population of the stone crayfish occurs in the western part of the country, while there is a countrywide distribution of the noble crayfish. On the contrary, the country's narrow-clawed crayfish is on the edge of extinction. The main reason behind the decline of this species is the expansion of the non-indigenous crayfish species transmitting the crayfish plague pathogen. Although sites of the stone and the noble crayfish occur in the upper parts of the river basins, there is a high risk of crayfish plague outbreaks, since the established spiny-cheek crayfish population are confirmed chronic carriers of the causative agent. Aquarist trade is increasingly recognized as an important pathway for the non-indigenous species introductions, out of which some may establish and become invasive. Freshwater crayfish, shrimp and crab species were recorded in the aquarist trade in Slovakia, counting altogether 26 different species. The marbled crayfish was one of the most frequently traded species. We identified several new sites of the marbled crayfish occurrence with established reproducing populations in very close vicinity of major rivers in the country. One of the newly identified flourishing spiny-cheek crayfish populations is located close behind a bank with a pumping station, i.e. critically close to a sidearm of the Danube River, with a confirmed crayfish plague infection. Marbled crayfish can become a crayfish plague carrier acquiring the pathogen from the infected spiny-cheek population in the Danube and rapidly spreading the disease along the river, thereby endangering the remaining populations of the narrow-clawed crayfish. More sites with the marbled crayfish are expected to occur in the country. Given their parthenogenetic reproduction, theoretically, a single individual is sufficient to establish a new sustaining population. Considering the high availability of the marbled crayfish in the pet trade industry and the rising numbers of established populations in the wild, research clarifying its potential impacts on the invaded ecosystems was warranted. We provide the first study investigating the trophic position and food preferences of the marbled crayfish in its well-established populations. Based on carbon 13C and nitrogen 15N stable isotopes analysis marbled crayfish were identified in the middle of the trophic chain with polyphagic diets. Marbled crayfish were found to utilize algae, allochthonous and autochthonous detritus, zoobenthos and macrophytes, thus being a strong competitor to a wide scale of organisms depended on the same food sources. The marbled crayfish transmit the energy from the bottom of the trophic pyramid to higher trophic levels as it was found to be a prey for top fish predators. This species can form dense populations and become a dominant component of the benthic fauna, thus affecting the entire invaded ecosystem. Its trophic niche width confirms high plasticity of the species, sustaining its populations in a wide range of different habitats. The marbled crayfish is thus a highly adaptable invader that can threaten not only the indigenous crayfish species by means of competition and the spread of crayfish plague, but also entire freshwater ecosystems and their biota.

The embryonic and early postembryonic development of all crayfish occurring open water of the Czech Republic were studied under controlled conditions.

Biological invasions of non-native species are one of the most serious factors threatening global biodiversity. Their negative impacts are particularly evident in the case of freshwater ecosystems and native crayfish populations that live there. Generally, the higher dominance of non-native crayfish species over the native species is relatively well known, but the interactions between non-native crayfish species are significantly less investigated. Although their distribution is increasingly more important and it is obvious that non-native crayfish species will dominate in European waters. However, it is not yet clear which of these crayfish will be more successful. The aim of this diploma thesis was to create a literature review on the topic of interspecific interactions in crayfish with emphasis on native and non-native crayfish species occurring in Europe. The experimental part of the thesis was focused on the comparison of direct interactions and competition for shelter between the widespread spiny-cheek crayfish Faxonius limosus (Rafinesque, 1817) and the newly increasingly occurring marbled crayfish Procambarus virginalis Lyko, 2017. These species are becoming increasingly common in the European wild, but about their mutual direct interactions and competition is largely unknown. During agonistic interactions the marbled crayfish won in significantly more fights than the spiny-cheek crayfish in the absence as well as presence of the shelter. The marbled crayfish established a significantly greater dominance over the females of the spiny-cheek crayfish in the absence and in the presence of shelter, but not over the males. It is also important to say that the presence of the shelter reduces the number of fights and their total duration. There was no significant difference in dominance established by occupation of shelter between the marbled crayfish and the spiny-cheek crayfish. Still, thanks to its aggressiveness, marbled crayfish is able to compete with other non-native species or displace them from freshwater ecosystems.

Signal crayfish (Pacifastacus leniusculus) is important invasive species in European freshwaters. Its influence on other freshwater organisms is well known from the literature, as well as direct and indirect impact on fish assemblages. This work was focused on the experimental evaluation of non-indigenous signal crayfish as a predator of salmonids compared to indigenous noble crayfish (Astacus astacus). Moreover, the possible importance of young-of-the-year signal crayfish as a prey for salmonids was assessed. There were carried out experiments using eggs and hatchings of grayling (Thymallus thymallus) as a prey for adult and subadult specimens of both, signal and noble crayfish. Next experiment used young-of-the-year signal crayfish as a prey for young-of-the-year of brown trout (Salmo trutta). Results showed that the danger of signal crayfish for grayling eggs is slightly higher. However, detected differences were surprisingly lower and in the majority of parameters even insignificant. In the case of grayling hatchings, was not detected any significant difference at all. The abilities of both tested species to prey on eggs and hatchings are therefore very similar, comparable. Even so, the effect of signal crayfish can be importantly higher in natural conditions because of its more dense populations, higher growth rate and fast maturation. In accordance to our findings, it is evident that brown trout has no so high effect of crayfish juveniles compared with crayfish effect on salmonids early developmental stages. Crayfish are therefore more likely able to limit salmonids than conversely.

This thesis is composed of two parts - research part, focused on field research of occurence and abundance of the Stone Crayfish and the Noble Crayfish in the basin of Zákolanský stream, and a pedagogical part, project Crayfish in the Czech Republic and their protection, aimed for grammar school students. The literature outline summarizes contemporary knowledge about all five species of crayfish in the Czech Republic. Our native species are the Stone Crayfish (Austropotamobius torrentium) and Noble Crayfish (Astacus astacus). The non-native are Narrow-clawed Crayfish (Astacus leptodactylus), Spiny-cheek Crayfish (Orconectes limosus) and Signal Crayfish (Pacifastacus leniusculus). Aside from the chapters concerning the particular species and their determination, the literature outline also contains general information about the life and endangerment of crayfish. I have conducted the field research from April to September 2009. I also noted and evaluated the environmental conditions of the crayfish habitats. Based on the adjusted AOPK ČR methodology, I selected eight 100-meter long brook-sections of the Europe-important locality of Zákolanský stream, with the previously confirmed occurrence of crayfish. From the eight sections, I found crayfish only in three. All the captured specimens were of the...

This thesis deals with monitoring the occurrence of crayfish in selected river basins in the western Bohemia, considering the human impact on freshwater ecosystems and his influence on crayfish and other aquatic organisms. The selected river basin territory was Úhlava, Úslava and Otava. In the localities, numerical and species-wise representation of crayfish was monitored by finding data from the Agency for Nature Conservation and Landscape of Czech Republic database. The flow and environment characteristics were also monitored. This thesis focuses on water quality in streams of selected major river basins, Úhlava, Úslava and Otava rivers in the period from 2006 to 2011. Results of the findings show a sympatric occurrence of original species, stone crayfish (Austropotamobius torrentium), noble crayfish (Astacus astacus) and part of the original danube crayfish (Astacus leptodactylus) with invasively spreading species of spiny-cheek crayfish (Orconectes limosus) and signal crayfish (Pacifastacus leniusculus). With respect to this fact, the sensitivity of spiny-cheek crayfish (Orconectes limosus) and signal crayfish (Pacifastacus leniusculus) are evaluated in a form of own test results on acute toxicity. The thesis compared current results of occurrence and the protection of crayfish in the Czech Republic and abroad. The conclusion of this thesis is a proposal of a freshwater biomonitoring system, using the crayfish.

The aim of this thesis was to verify the success of previous reintroduction of noble crayfish (Astacus astacus) in main streams and selected reservoirs in the protected area Třeboňsko. Further expansion took place monitoring invasive signal crayfish (Pacifastacus leniusculus) and spiny cheek crayfish (Orconectes limosus) in these streams. Both are a carrier of crayfish plague. Thus, where they already exist, would not make sense to try to strengthen further the population of noble crayfish.