The activity of several antioxidant and detoxifying enzymes, superoxide dismutase SOD, GSH peroxidase GSHPx, GSSG reductase GSR and GSH S transferase GST, the contents of thiobarbituric acid reactive substances TBARS, and the SOD and GST isoenzyme patterns were studied in the livers of chubs Leuciscus cephalus from reference river areas and polluted urban sites. Livers of polluted fish contained higher concentrations of transition metals, especially copper and iron. Total GSHPx activity was 1.8 fold higher in the polluted fish than in reference animals, while the SOD and GSR activities and the TBARS content were not significantly changed. Three new SOD isoforms pI 4.45, 5.1, 5.2 and a higher intensity of the band pI 4.2 were observed after isoelectrofocusing of polluted fish extracts. Total GST activity was higher in fish from polluted areas. The GST isoenzyme pattern was studied using subunit specific substrates DCNB, EPNP, EA, NPB, NBC and by Western blot using antibodies specific to rat GST subunits 1, 8 Alpha class, 3 Mu class and 7 Pi class. Reference and polluted fish lacked cross reactivity towards Alpha class GSTs. Reference fish displayed weaker cross reactivity towards CST 7 and 2.3 fold lower activity with EA, while higher cross reaction with GST 3 was observed in polluted fish.

Six non-native invasive fish species from the Slovak part of the Tisa River basin, namely Carassius gibelio, Pseudorasbora parva, Ameiurus melas, A. nebulosus, Lepomis gibbosus, Perccottus glenii, and three gobiid species from the Danube River, namely Neogobius melanostomus, N. fluviatilis and N. kessleri, were investigated for endohelminth parasites. The expanding Asian cestode Nippotaenia mogurndae (syn. Amurotaenia perccotti) (Nippotaeniidea) has been introduced to Europe with its invasive host P. glenii. Pumpkinseed, Lepomis gibbosus, is a new definitive host of Proteocephalus percae and it is reported as the second intermediate host of the bothriocephalidean cestode Triaenophorus nodulosus in Slovakia.

SummaryData on prevalence and current distribution of the cestode Nippotaenia mogurndae Yamaguti and Miyata, 1940 (Nippotaeniidea) in Slovakia, are provided. A total of 163 fish from 8 localities of different types in the Tisa River basin were infected with N. mogurndae. The mean intensity of infection was 1.8 with a maximum of 5 tapeworms. The expansion of the distribution of the cestode corresponds well with the spreading of its host, the invasive fish Amur sleeper Perccottus glenii Dybowski, 1877. The Spearmann correlation coefficient was used to test the relationship between the intensity of infection and standard length of the fish (r = 0.36; n = 163; P < 0.05), condition coefficient of the fish (r = 0.22; n = 115; P < 0.05) and season (r = -0.37; n = 355; P < 0.05). A significant correlation was confirmed for each pair of variables. There is a statistically significant difference between the prevalence of the cestode in two functional size groups (t = 3.28; n = 163; P < 0.05). The prevalence of the cestode increased with the standard length of fish. The potential risk of further expansion of N. mogurndae to other countries is discussed.

Abstract:Freshwater fishes recorded in the territory of Slovakia include 95 fish species. As many as one third of these are allochthonous fish species belonging to 14 families, among which several have not occurred in Slovakia recently. Historically, there were three main periods of introduction: the first is the beginning of the 20 th century, the second includes two decades between 1955 and 1975 and the third period is from the year 1990 up to the present time. The origins of the exotic species seen in Slovakia are the four continents -Africa (3), North America (7), Central America (3), and Asia (13) and ten of them are from different regions in Europe. The purpose of intentional introductions of non-native species was to occupy vacant ecological niches in the ecosystems reshaped by human activities, fish stocking, angling or fish farming. Some of these species spread from their original ranges or they penetrated spontaneously from the adjacent countries via the river network system. At the present time, 76 fish species in total form populations in Slovakia. There are 54 autochthonous and 22 allochthonous species, 14 of them are exotic fishes. The invasive characters in 13 fish species were considered, the recent native/total fish ratio is 0.71.

SummaryThe Asian fi sh tapeworm, Bothriocephalus acheilognathi Yamaguti, 1934, was detected for the fi rst time in breeding of discus fi sh Symphysodon discus (Perciformes, Cichlidae), a popular South American cichlid. In examined samples, the adult and juvenile cestodes of B. acheilognathi with mean intensity of infection 30 (range 19 -47) individuals per fi sh were found. The infected fi sh displayed acute behavioral symptoms. Mortality was signifi cant; it reached almost 80 % in youngest age categories. As treatment, praziquantel immersions in dose 2 mg per liter were well tolerated and effi cacious. The risk of spreading pathogens via imported fi sh is actual menace for ornamental breeding fi sh, therefore, thorough quarantine and prophylactic measures needs to be done by all fi sh imports and introductions. Import and subsequent release of infected ornamental fi sh into freshwater ecosystems may represent serious risk for spread and establishment of the parasite in native fi sh species. This case study illustrates that ornamental fi sh play also a key role in national and international movements of parasites in freshwater habitats.