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The studies were carried out on 67 fish coming from six breeding stations. It was found that the fish were a potential reservoir of A. hydrophila and therefore might be a source of infections and alimentary poisonings in humans. From the surface of fish there were isolated 17 strains of A. hydrophila (25.3%), from the homogenates of internal organs — 10 strains (14.9%) and from muscles — 2 strains (2.9%). All the examined strains were susceptible to streptomycin, neomycin, gentamycin, chloramphenicol and nalidixic acid. They were resistant to penicillin, ampicillin and tylosin. As to other antibiotics: 83% strains were susceptible to oxytetracycline, 25% to sulphonamides, 55% to trimethoprin plus sulphametozazol and 25% to nitrofurantoin.
Crayfish accumulate trace metals, which is why they often serve as environmental indicators. Among heavy metals, Hg, Cd and Pb are considered toxic substances, while Fe, Zn, Cu, Cr, Ni, Mn, V, Al and Li are involved in vital functions, which makes them essential elements in animal organisms. The study objective was to determine concentrations of the above metals in the abdominal muscles, hepatopancreas and exoskeleton of spinycheek crayfish (Orconectes limosus Raff.) and signal crayfish (Pacifastacus leniusculus Dana) from Dga³ Wielki Lake and Pob³êdzie Lake in the Mazurian Lake District, Poland. The analyses were carried out with the use of the following methods: CV AAS (Hg), GF AAS (Cd, Pb) and ICP-AES (Al, Cr, Cu, Fe, Li, Mn, Ni, V, Zn) after wet digestion in HNO3 and HClO4 concentrated acid mixture. Regarding mean concentrations (mg kg-1 wet weight) in crayfish, metals formed the following order: Al (14.8-123.4) > Mn (0.26-91.3) > Fe (0.54-81.1) > Zn (6.80-51.91) > Cu (1.21-4.34) > Ni (0-0.782) > Cr (0.032-0.606) > V (0-0.245) > Li (0.011-0.215) > Pb (0.018- 0.079) > Hg (0.004-0.045) > Cd (0.001-0.017).Metal concentrations in crayfish organs were varied, and for different metals they decreased in different order: Al, Mn, Cu, Ni, Cr, V and Li – exoskeleton > hepatopancreas > muscles; Zn and Hg – hepatopancreas > muscles > exoskeleton; Fe – hepatopancreas > exoskeleton > muscles, while for lead and cadmium no overall correlation was observed. The comparison of metal concentrations in the organs of spinycheek crayfish from Dga³ Wielki Lake and Pob³êdzie Lake did not prove any statistically significant discrepancies. Also, some minor interspecies differences in the metal content proved insignificant. According to the European Union regulations, concentrations of toxic heavy metals (Hg, Cd, Pb) in the muscles of both species of the tested crayfish were significantly below the maximum levels.
European eel Anguilla anguilla L. is a fish species highly valued in European fisheries, currently reared under controlled conditions (Aquatic Recirculation System – RAS). In order to protect the health of fish, regular check-ups are carried out in specialized veterinary laboratories. Health hazards are recognized on the basis of clinical, pathological, microbiological, and parasitological surveys. The aim of the study was to analyze the results of health assessment of eels reared under controlled conditions, which was performed in the Diagnostics Laboratory of Fish and Crayfish Diseases, Department of Veterinary Hygiene, Voivodeship Veterinary Inspectorate in Olsztyn, in the period from 2010 to 2014. The results are presented according to the etiologic agents, divided into bacterial and parasitic diseases. In this period, 73 samples (100%) were examined, including 5 samples (6.85%) from glass eels and 68 (93.15%) from elvers. Microorganisms isolated from the collected material were mainly conditionally pathogenic, such as Pseudomonas fluorescens, Aeromonas hydrophila, Shewanella putrefaciens, Aeromonas sobria, Flavobacterium spp., and Chryseobacterium indologenes. The parasitological examination revealed infection with Trichodina spp., Ichthyophtirius multiphilliis, and Pseudodactylogyrus spp. The most frequently diagnosed were gill monogeneans, detected in 34 cases (75.55% of all positive parasitological test results). In 21 cases (61.8%) the infestation manifested itself as a disease. The remaining 13 cases were asymptomatic carriers (38.2%). The analysis shows that the main problem in the controlled rearing of eel are parasitic infestations, which may be endemic and pose a constant threat. Systematic monitoring and preventive measures are necessary throughout the rearing and fattening of fry to maintain a good health status of eels.
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