|
|
Interakce spermií a jiker u sladkovodních ryb: vliv prostředí na fertilizační proces
KHOLODNYY, Vitaliy
Fertilization of fresh water fish occurs in an environment which may affect negatively the gametes, therefore the fish male gametes should reach their counterpart, the female gamete, as soon as possible because spermatozoa become damaged within minutes or less due to osmotic shock. Existence of specific mechanism triggering, supporting and guiding the encounter of gametes would be highly expedient in these conditions. The eggs of many externally fertilizing freshwater fish species are released into the external milieu surrounded by a coat of ovarian fluid (OF) with a composition ideal for supporting and protecting eggs and sperm against the deleterious effect of freshwater. The existing data support the idea that the properties of OF and/or the specific compounds contained in it or released by the eggs could significantly affect the behavior of male gametes and consequently influence the outcome of fertilization in terms of the number of fertilized oocytes. The mechanisms which facilitate and trigger gametes' encounter are also highly demanded in terms of natural selection. It was found that presence of OF affected significantly the behavior of rainbow trout spermatozoa, in particular, their motility traits: higher velocity was supported for longer time and trajectories were straightened, comparing to those observed in water. In the microcapillary spermatozoon accumulation test (test of chemotactic response) the rainbow trout OF showed a trapping effect on activated male gametes which depended on osmotic properties of the activating media. Different molecular weight fractions from OF affected the tactic behavior of the cells in a various way. The most significant trapping effect was rendered by low molecular fraction and the possible chemotactic agent was found to be thermostable. The trapped cells showed specific turn-and-run behavior accompanied by asymmetric bending of flagella and burst-like increase of calcium concentration in the bended area. The in vitro fertilization test revealed the enhancement of spermatozoa performance, especially in the samples from the related individuals, which led to the higher embryo development rate. Presence of particular concentration of ovarian fluid (30% solution in water) had inhibiting effect on sterlet spermatozoa motility initiation. Lower concentrations of the ovarian fluid improved the longevity of spermatozoa and did not affect their trajectories. Test of chemotactic response showed no effect of ovarian fluid on spermatozoa behavior, while at the same time the attracting effect of egg conditioned medium was evident (i.e. due to some substances released from the eggs during their contact with fresh water). The results of in vitro fertilization test showed that presence of ovarian fluid prevented the eggs from losing the fertilizing ability due to the contact with water, as well as promoted the spermatozoa to fertilize the eggs during longer period of time. Presence of common carp ovarian fluid in the activation medium caused the decrease of the velocity of spermatozoa comparing to the OF-free medium and significantly altered the motility pattern from straightforward motility observed in the water to the tumbling in the medium with high OF content (50%). Introduction of OF (in the sperm accumulation test) entailed immediate and prominent chemotactic-like reaction of spermatozoa. The environmental conditions which accompany the encounter of gametes, in particular presence of OF, calcium ion content and osmolarity, significantly affect the performance of male gametes in spermatozoa in rainbow trout, sterlet and common carp in terms of changes in velocity, path linearity and ability to response to the external signals, e.g. attractants. The conducted study allowed to conclude that way how the ovarian fluid affects the behavior of spermatozoa in these species may be associated with their reproduction (spawning) strategy.
|
|
|
Morfologie chovaných skupin lososovitých ryb
Halačka, Karel ; Mendel, Jan ; Mareš, J.
Cílem studie bylo sledování vybraných morfologických znaků sledovaných druhů či skupin lososovitých ryb : pstruh duhový (Oncorhynchus mykiss) původem z Dánska, Itálie, Jihoafrické republiky, siven americký (Salvelinus fontinalis), siven arktický (S. alpinus), siven obrovský (S. namaycush), a jejich hybridi (S. fontinalis x S. alpinus). Sledovány byly vybrané morfologické parametry - stavba těla, hmotnost vnitřních orgánů, struktura pokožky a žáber.
|
|
|
Quality of smoked products of economically important fish species
KORYŤÁK, Lukáš
The objective of this thesis was to test the environmental friendly additive substance, in particular sodium caseinate, which is not subject to designation "E" on the label of the product, which is unpopular among the consumers, and which would provide so-called a "higher value" to a product of economically important fish species in the Czech Republic, specifically the common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix) and the rainbow trout (Oncorhynchus mykiss).Determination of the influence of this additive on microbial and biochemical processes, and also on organoleptic properties of the selected smoked fish was another goal of the work. Three concentrations of this product were used for application in total, in particular 25, 50 and 100 g×kg-1. The results of this work confirmed that, due to caseinate (concentration of 100 g×kg-1) such losses of water were avoided, as observed in case of the control group, to which no additive product was applied, and which served for comparison with the groups treated with caseinate. General carp had an average loss of 12.9 % for the samples treated with sodium caseinate and 14 % for the control group. The silver carp white showed similar results. The group treated with caseinate lost 12.4 % in average, and the control group of approximately 14 %. The best results were recorded with the rainbow trout, which, due to caseinate withheld the largest amount of water, respectively, it did not lose so much of weight, in particular 15.9 % for sodium caseinate compared to 19.3 % measured in the control group, however these differences were not confirmed as statistically conclusive. As for the texture of the meat, tougher samples came out for the ones treated with sodium caseinate compared to the more brittle control group. In carp and trout no statistically noteworthy dissimilarity in stiffness of meat was proved between the control group and the group with the applied additive product. While these differences were significant in silver carp. While for silver carp were these differences significant. The control group showed clearly (p<0.05) lower stiffness compared to the group, to which the additive product was applied. Microbiological analysis was performed on the 7th day after smoking, and the values were in the range of 2×10 to 1.9×10^2 CFU×g-1. In the experiment, groups of test fish species did not show any statistically significant difference (p>0.05). Tests for the possible presence of Listeria monocytogenes in all of the smoked fish samples and the control group were negative. Nutrient composition was mainly focused on the basic nutrient components, which were the proteins, fats and carbohydrates. The control group did not show any significant differences compared to the group to which sodium caseinate was applied. The results from the consumers and sensory analysis by a panel of trained persons were very similar. No statistically significant differences between the group treated with caseinate sodium, and the untreated so called control group of smoked species of fish.
|
|
|
Influence of insect´s components in fish feed on production, health and quality of fish.
HLÁVKOVÁ, Markéta
The first part of my work is devoted to review of alternative components in feeds for fish with special focus on insect. The second part of my work is based on the feeding experiment. Rainbow trouts (Oncorhynchus mykiss) were bred in the aquaria at the Faculty of Fisheries and Protection of Water JU in Vodňany. Experiment was performed in three replications, in 300 litre aquaria with 8 - 10 fish per aquarium. Fish were divided into 5 groups according to the type of feed used. Control group was fed the commercial granule feed and the other four groups were served insect in certain percentage. It was a cricket (Acheta domesticus) and the maggots of giant mealworm beetle (Zophobas morio).Weight and length of fish was registered three times during 2 months of experiment. The sensory analysis of fish meat was done for evaluation of aroma, taste, after taste and consistence of fish muscle. The results show that diet containing insect did not significantly influence weight and growth. In the contrast, sensory analysis proved the difference in analysed parameters. The feed containing only insect was identified as an inappropriate alternative feed. In conclusion, the insect can be used as the alternative feed for fish in the aquaculture. Nevertheless, it is recommended to combine the insect with commercial feeds.
|
|
|
Extending of shelf life of chilled fish products
PFLUG, Róbert
This diploma thesis was focused on the possibilities of extending the shelf-life of fish products by dipping containing seven commercial additives. ANTIBAK, MIC STAB, Bakont, SEA-F75, Misocarine LR, SAFE A Plus and AMX liquid. The effectiveness of these substances on the extending of shelf-life was evaluated on the basis of tests of TVC (total viable count), level of fat and protein oxidation, determination of nutritional parameters of muscle, and finaly sensory analysis. Experimental species were 2 important commodities for the Czech aquaculture rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio). The project was divided into 6 sub-stages. During testing was the initial number of aditives (7) limited by stepwise selection for 2 preparations. Namely Bakont and AMX liquid, which were tested further on trout (filet with skin and scales) and carp (filets with skin without scales) chilled bulk and chilled packaged under vakuum. For trout was studied antimicrobial effect of dipping on eviscerated fish with the head with- or without gills. Treated trout fillets in bulk and vakuum-packed showed significantly less abundance of muscle mikroflora. In the case of carp fillets chilled bulk we can not say that the bath had influence on the CMP in meat. However, the combination of dipping and vakuum packaging was singnificantly different between the control and product Bakont. AMX liquid was not applied in this case in sufficient dose or in sufficient time to carp muscle. A positive finding is that the application of the aditives to the product "eviscerated trout with head" it does not matter, whether the gills are left in fish or not. However, in all cases the analysis of the presence of pathogens Escherichia coli, Salmonella spp. or Listeria monocytogenes were negative. From the results of sensory analysis can be concluded, that the substances contained in aditives are not reflected in the sensory properties of tested fish.
|
|
|
Hematological changes in fish exposed to nitrites
FRANĚK, Roman
The aim of the thesis was to determine the effect of nitrite on hematological indices of rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus). After the fish were exposed to various concentrations of nitrites were determined 48hLC50. For the main test only fractional concentrations of these values were used. For rainbow trout it was 8 mg.l-1 NO2?, for Nile tilapia 11 mg.l-1 NO2?. The exposure of both species lasted for 48 hours. From fish blood were made blood smears to determine the influence of nitrite on size changes of erythrocytes and hematological parameters were set also. The effect of nitrite on changes in the ultrastructure of erythrocytes was determined by the electron microscopy. The erythrocyte nuclei of rainbow trout showed significant (p <0.05) shrinkage. The images of the electron microscope showed an increased amount of changes, especially in the form of various units within the cytoplasm of erythrocytes, was also visible nuclei shrinkage. There was significant (p < 0.01) reduction in the amount of hemoglobin and significant (p < 0.01) increase in the concentration of methemoglobin levels of the exposed groups. In the number of erythrocytes and hematocrit were not detected any changes. Hematological parameters of Nile tilapia did not show any size changes in the measured parameters, no changes were detected in the count of erythrocytes, hemoglobin and hematocrit values.
|
|
|
Changes of biochemical parameters in fish after nitrite exposure
PODLESNÝ, Martin
The aim of this thesis was to assess the effects of long-term nitrite exposure on mortality, growth rate and blood biochemistry in rainbow trout (Oncorhynchus mykiss). Furthermore, acute toxicity tests with nitrite were performed on rainbow trout (Oncorhynchus mykiss) and sheatfish (Silurus glanis). The theoretical part focuses on aquatic toxicology including toxicity evaluation of substances and preparations for water organisms. Detailed information on nitrite are summarized there, namely information on nitrite occurrence and sources in aquatic environment and the mechanism of their uptake and toxic influence on fish including factors influencing their toxicity. The practical part consists of methodology and results of acute toxicity tests on rainbow trout and sheatfish and sub-chronic test on rainbow trout. According to the acute toxicity tests results, 96hLC50 values were estimated at 11.2 mg.l-1 NO2- for rainbow trout and 15.3 mg.l-1 NO2- for sheatfish. Sub-chronic exposure of rainbow trout to nitrite concentrations ranging from 0.01 to 3.0 mg.l-1 lasting 28 days caused an increase of glucose concentration and a decrease of potassium concentration in the blood plasma among all experimental fish compared to control. Elevated nitrite levels were found in the plasma of the fish exposed to concentrations of 0.6 mg.l-1 NO2- and greater. The plasma nitrite levels did not reach those applied in any experimental group in the present study. At highest nitrite concentration (3.0 mg.l-1 NO2-), 42 % growth inhibition and 65 % mortality among fish was noticed. On the basis of growth rate inhibition data, the values of NOEC and LOEC were estimated at 0.01 mg.l-1 and 0.2 mg.l-1 NO2-, respectively.
|
guest ::
