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Rozhodovací proces u raků: problematika chování a reprodukce
This thesis provides an overview of case studies investigating the behaviour of freshwater crayfish, including social and reproductive interactions, decision making, and channels for recognition or processing of environmental stimuli. We described relationships between the environment and the organism and relationships among conspecifics and heterospecifics. These aspects are important, given that every decision and interaction has consequences for crayfish survival and reproduction, i.e. individual and even species success. For ethological studies in aquatic ecosystems, crustaceans, and especially crayfish, represent practical model organisms. Crayfish are advantageous over other invertebrates given their high level of social interaction in both the field and the laboratory. They exhibit unique eco- ethological behaviour in variety of feeding habits, activity cycles, habitat selection, and resource utilization at the level of species, sex, and age. Similar to vertebrates, crayfish demonstrate unique behaviours throughout their life. Subsequently, pollution impacts on native crayfish stock can result in ecosystem instability. The different reproductive strategies of females and males demonstrate that females rely on some familiarity of sexual partners as a reliable guarantee for successful mating. Crayfish females are choosier than males because of their higher energy costs for reproduction (oogenesis, incubation, parental care). While male reproduction prioritises securing their genetic information by searching for as many mates as possible. Crayfish mate preferences was analysed by facing the choosing crayfish with two equal sized mature counterparts from the same or different origin. Our conclusions could be applied in conservation research, captive breeding, and recovery programs as well as in aquaculture. The success of biological invaders has been described as the outcome from intra- and interspecific interactions. The marbled crayfish, known as parthenogenetic species with high adaptability, fast growth, early maturation, and high fecundity, established dominant status in more cases by interspecific combat victories. Fight intensity and aggressiveness decreased after dominance was established in particular pairs. Marbled crayfish seem to have an ability to conserve energy by increasing activity only at times of danger. Based on known species-specific abilities, the marbled crayfish is capable of outcompeting aggressive species, such as the red swamp crayfish. This parthenogenetic species poses a substantial threat to native ecosystems and biodiversity of aquatic environments, since it can establish not only in crayfish free habitats, but is also capable of outcompeting resident species. Recently, dilute concentrations of contaminants such as pharmaceuticals, daily-care products and pesticides have been reported to indirectly affect aquatic organisms. We found that selected pharmaceuticals can alter the behavioural patterns of crayfish, event at the very low concentration. The risks associated with surface water pollutants stresses the importance of research investigating their ecological impacts and their different/specific mechanisms of action. Prolonged exposure to the low concentrations of two pesticides exhibited changes in crayfish behavioural patterns. Various alterations in locomotion were observed after treatment in pesticide-free water. In the wild, decreased movement and activity can be a challenge for crayfish survival because of predation, even foraging to compensate for energy loss could be very difficult for less active individuals. This study suggests that crayfish behaviour assessment is a practical approach not only for investigating basic biology, or intra- and inter-specific interactions, but also for assessing the risks associated with micro-pollutants.
Study of the reproductive biology of the crayfish - mating, laying eggs and morphological structure of the male and female gametes
In the nature, crayfish are represented like predators or a part of food base of some fish. Also in free waters they acts as detrivors and are an important element in the nutrient and energy circle in aquatic ecosystem. The crayfish weren't able to avoid negative impacts of anthropogenic activities such as water pollution and devastation of habitats. For these reasons reproduction of the crayfish is necessary in hatcheries and farms. The main aim of my work was to study the reproductive biology of the crayfish focused on the process of mating, the interval between mating and laying eggs, fertilization and morphological structure of the male and female gametes. Among the secondary objectives there was included using of repeated electrostimulation of the crayfish and the possibility of hybrids of the noble crayfish (Astacus astacus) and the narrow-clawed crayfish (Astacus leptodactylus). The observation of the period of reproduction was realized on representativies of the noble crayfish and the narrow-clawed crayfish throughout natural mating in the tanks. The structure of gametes was observed on the samples taken from thenoble crayfish (Astacus astacus), the narrow-clawed crayfish (Astacus leptodactylus), the signal crayfish (Pacifastacus leniusculus), the red swamp crayfish (Procambarus clarkii) and spinycheek crayfish (Orconectes limosus). The experiments were carried out during the autumn season in 2012 and 2013. The results of observations of the reproduction of crayfish made us clear as for the period and intervals for all phases of the process of mating crayfish. For females the noble crayfish and the narrow-clawed crayfish was found oviposition without the presence of males. Their individual components have been described by using ultrastructure of males and female gametes. Repeated electrostimulation showed at the family Astacidae as a suitable tool for collecting large mass of sperm material. Hybridization experiment proved that it can occur to mate the two species of crayfish in areas where they occur simultaneously. These experiments helped to further knowledge of reproductive biology of crayfish.
The electrostimulation the spermiation in the crayfish
The crayfish are important and indispensable animals in aquaculture. In the aquatic environment, they have a role as predators, food for other fish, detrivors and they are an important element in the circulation of the energy and the nutrient in the aquatic ecosystem. Today, number of the european crayfish species populations is decreasing. It is caused by unfavourable regulation of streams, water pollution and the occurence of crayfish plague. The main purpose of present study was examining the impact of electrostimulation on the males of the crayfish and obtaining sex products (the sperm). The principle of this research was determining whether the male of crayfish are able to extrude spermatophore with sperm by an electric stimulus. The transformer was used as resource alternating current in experiments. All experiments conducted in a laboratory of experimental device for fish farming in Vodňany. Experiments were conducted in 2011 on a male of the spiny-cheek crayfish (Orconectes limosus), the signal crayfish (Pacifastacus leniusculus) and the red swamp crayfish (Procambarus clarkii). The results of this work and success of the experiments suggest, that electrostimulation could be used for obtaining sex products (the sperm) from crayfish males. Results from a laboratory of electron microscopy confirm the harmlessness of electrostimulation on the shape and structure of sperm. The sperm can be used to artifical insemination of the crayfish eggs in future. However, sperm capacitation is problematic.

See also: similar author names
1 Kubec, Jakub
4 Kubec, Jiří
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