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Interspecific sperm competition in sturgeon
ŠACHLOVÁ, Hana
Sturgeon species (order Acipenseriformes) are prone for interspecific hybridization. Anthropogenic activities in river basins influence sturgeon reproduction by destruction of their natural spawning grounds. Consequently, spawning areas, as well as the time of spawning of sturgeon species overlap and different sturgeon species reproduce concurrently. This increases the probability of meeting of heterospecific gametes and pre-zygotic postcopulatory reproductive barriers, comprising of sperm competition and cryptic female choice, may play an important role in preventing undesirable interspecific hybridization. The goal of this study was to evaluate the role of interspecific sperm competition and cryptic female choice during interspecific hybridization of sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baerii). Reproductive characteristics (fertilization rate and hatching rate) were described in each of experimental and control groups showing similar values for competitive and non-competitive trials. Parentage assignment was performed in hatched larvae using combination of mitochondrial DNA and microsatellite DNA markers. Obtained results revealed higher fertilization success of sterlet spermatozoa, when these competed for fertilization with spermatozoa of Siberian sturgeon. Total reproductive success of starlet spermatozoa was 78.9 % and Siberian sturgeon 21.1 %. Contrary, when spermatozoa did not compete for fertilization, males of analysed species showed equal fertilization success. In the trials, where eggs of both studied species were mixed and fertilized by sperm from each species separately, eggs of any species did not show a tendency to bias fertilization by spermatozoa of conspecific males. Probably, there are no pre-zygotic postcopulatory reproductive barriers that prevent interspecific hybridization of sterlet and Siberian sturgeon at the gametic level.
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International trade in the Siberian sturgeon (\kur{Acipenser baerii})
KORUNKOVÁ, Eva
Sturgeon fish (Acipenseriformes) is commercially used to produce high quality fish meat and highly priced caviar. In fact, all species of Sturgeon fish are integrated into CITES appendix. Sturgeon (Acipenser baerii) is the most frequently bred/reared and the most commercial representative of its kind, not only in Europe but also in Asia. The aim of this final project is to evaluate international sturgeon trade while using CITES references from 1998-2012. The source of data(s) was commercial database CITES. Over the last 15 years, we have exported and imported almost 5000 tons and 32 million pieces of all species. During this monitored period the frequency/traffic of the trade increased. The mostly traded forms were fish eggs which were exclusively destined/designated for commercial purpose and came from those specimens which were reared in captivity - (94% from commercial activity). People mostly traded sturgeon in these forms : (1) eggs, (2) caviar, (3) extracts,(4) derivatives, (5) fish meat and others. In the last 3 years, the trade intensity in fish eggs markedly decreased. On the contrary, since 2008 there was an annual growth of/in the sale of caviar. France was not only the country of origin but also the country where there was the largest/greatest/biggest volume of market. Germany was one of the main export countries, while Armenia , if we take the quantity (kg) into account. On the other hand, The U.S. was the main import country. Sturgeon was exported in the greatest quantity to Moldavia. During the period of time mentioned above, The Czech Republic exported only twice (35 000 pieces) and imported (210 pieces) of living specimen.
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The impact of interspecific hybridization on fitness of Sturgeons
ŠACHLOVÁ, Hana
Sturgeons (order Acipenseriformes) are supposed to be one of the oldest groups of vertebrates still living on our planet. Moreover, their polyploid ancestry makes them very susceptible for interspecifc hybridization. These interspecific and intergeneric hybrids have been already described in nature as well as in captivity. Nevertheless, the fitness of sturgeon hybrids in comparison with pure species has not been studied yet even though it can have significant impact on sturgeon aquaculture production. The main goal of this study was to investigate and compare reproductive features (fertilization rate and hatching rate), survival rate and growth rate of artificially produced hybrids of Siberian sturgeon (Acipenser baerii) and Russian sturgeon (A. gueldenstaedtii) with their pure parental species. The experiment was performed till 262 day after hatching. It was supposed that these observed features could have significant impact on fitness of analyzed individual/groups. The highest reproductive features had hybrid between Siberian sturgeon (Acipenser baerii) females and Russian sturgeon (A. gueldenstaedtii) males while purebred group of Russian sturgeon displayed the lowest values of fertilization and hatching rate. At the beginning of the experiment, the highest survival rate was shown by purebred groups of Siberian sturgeon (Acipenser baerii) and Russian sturgeon (A. gueldenstaedtii), but this trend were slightly changed after 37th day post hatching. At the end of the experiment, the lowest value of survival rate was shown by purebred group of Russian sturgeon (A. gueldenstaedtii). Similarly, the lowest growth rate was also owned by purebred group of Russian sturgeon (A. gueldenstaedtii). In contrast, the best total growth rate was observed for hybrids between Russian sturgeon and Siberian sturgeon (A. geuldenstaedtii × A. baerii ) even though they grew slower until 101st day after hatching. Therefore, given the evidence discussed, this kind of hybrid could be suggested for intensive aquaculture and might be also suitable for polycultures stock. Finally, breeding of sturgeon hybrids might be seen as an effective alternative to pure species in sturgeon aquaculture, but suitable kind of hybrid must be selected.
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Acute toxicity of nitrite for sturgeons (Acipenseridae)
BULÍČEK, Vojtěch
The aim of this thesis was to assess and compare the acute toxicity of nitrite for two species of sturgeon fish. In the theoretical part deals with sutrgeons (Acipenseridae), nitrogen compounds, toxicity tests and toxic effects of nitrite to fish. In the experimental part deals with the methodology of tests and evaluation of their results. The results are compared in the discussion and evulated in the conclusion.
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