Perch Liver Research Articles

Development and validation of a LC-MS method for the quantification of microcystins in fish for their monitoring in environmental and food context

Cyanobacterial blooms in aquatic ecosystems can result in the accumulation of cyanotoxins in other organisms. Fish can potentially accumulate large amounts of cyanotoxins through their direct interaction with contaminated water and the ingestion of cyanobacterial cells. As a human food source, this can result in a potential health risk. Investigating and monitoring this risk requires analytical methods sufficiently robust to be suitable for different fish species. This study, therefore, aimed to optimize and validate an UHPLC-MS/MS method for the quantification of eight microcystin congeners and nodularin in five different fish species. The limits of detection and quantification were 1 and 3 μg kg−1, respectively. The linearity of the method was very good, with calculated R2 values above 0.99. The mean recovery of the method was within the acceptable range of 70.0%–120.0 %, the repeatability was not higher than 12.6 %, and the highest intra-laboratory reproducibility was 18.7 %. The estimated range for the expanded measurement uncertainty was between 29 % and 58 %. Moreover, multiple fish from Flemish waters were analyzed to show the method's applicability. Multiple microcystin congeners were detected (up to 88.3 μg kg−1 sum of analyzed microcystins) in the liver and viscera of perch and sander. Small amounts of MC-LR and MC-YR (up to 6.1 μg kg−1) were also detected in perch muscle tissue.

Изменение содержания тяжелых металлов в печени Perca fluviatilis

An assessment of the impact of emissions from the activities of coal mines on the morphology and physiology of perch (Perca fluviatilis) of the Bolshoe and Stolbovoye lakes of the Sorokaozerki tract in the Altai region of the Republic of Khakassia was carried out. Common perch, along with silver carp, are the predominant species in most fishing lakes of Khakassia. The catch of fish was carried out in 2019, 2021 and 2022, the absence of common perch in the catches of 2022 led to the need to analyze this phenomenon. 20 specimens from each reservoir were examined. The regularities of the correlative growth of their internal organs of fish were taken into account, since the living conditions of animals closely correlate with some of their morphological features. Morphophysiological indicators were studied, namely the liver index of perch (Perca fluviatilis), a comparison of this indicator by age and time of capture was carried out. The average index for each age group was calculated taking into account the arithmetic mean error. It was found that the value of the liver index tends to increase over the period from 2019 to 2021 for all age groups, which may indicate the problem of accumulation of heavy metals in the liver. Samples of the liver of the common perch were examined for the content of heavy metals (Pb, Cd, Zn, Cu, Fe, Co, Mn, etc.). The content of lead, arsenic, mercury in the liver of fish does not exceed the MPC. For individual metals (zinc, copper, chromium, iron), there is a large significant excess of MPC: 82% zinc, up to 40% copper, more than 90% chromium, exceeding the MPC of iron by more than 2.4 times.

Preparing for the future offspring: European perch (Perca fluviatilis) biosynthesis of physiologically required fatty acids for the gonads happens already in the autumn.

Long-chain polyunsaturated fatty acids (PUFA) are critical for reproduction and thermal adaptation. Year-round variability in the expression of fads2 (fatty acid desaturase 2) in the liver of European perch (Perca fluviatilis) in a boreal lake was tested in relation to individual variation in size, sex, and maturity, together with stable isotopes values as well as fatty acids (FA) content in different tissues and prey items. ARA and DHA primary production was restricted to the summer months, however, perch required larger amounts of these PUFA during winter, as their ARA and DHA muscle content was higher compared to summer. The expression of fads2 in perch liver increased during winter and was higher in mature females. Mature females stored DHA in their gonads already in late summer and autumn, long before the upcoming spring spawning period in May. Lower δ13CDHA values in the gonads in September suggest that these females actively synthesized DHA as part of this reproductive investment. Lower δ13CARA values in the liver of all individuals during winter suggest that perch were synthesizing essential FA to help cope with over-wintering conditions. Perch seem able to modulate its biosynthesis of physiologically required PUFA in situations of stress (fasting or cold temperatures) or in situations of high energetic demand (gonadal development). Biosynthesis of physiologically required PUFA may be an important part of survival and reproduction in aquatic food webs with long cold periods.

Rapid detection of eugenol in perch utilizing electrochemical method by transition metal substituted polyoxometalates.

Food safety concerns caused by the application of spice allergens to fish anaesthesia. In this paper, a chitosan-reduced graphene oxide/polyoxometalates/poly-l-lysine (CS-rGO/P2Mo17Cu/PLL) modified electrode was constructed by electrodeposition and successfully applied to the quantitative analysis of eugenol (EU). The detection limit was 0.4490μM in the linear range of 2x10-6 M to 1.4x10-5 M. It was applied to the determination of EU residues in kidney, liver and meat tissues of perch with recoveries ranging from 85.43 to 93.60%. Besides, the electrodes demonstrate high stability (2.56% drop in current value after 70days at room temperature), high reproducibility (RSD of 4.87% for 6 parallel electrodes) and extremely fast response time. This study provided a new material for the electrochemical detection of EU.

METABOLIC ADAPTATION OF FISH INTESTINAL HELMINTHS: INHIBITORY ABILITY TOWARDS PROTEASES IN CESTODES <i>TRIAENOPHORUS NODULOSUS</i>

The inhibitory ability towards proteases was studied in the extracts of plerocercoids from the liver of perch (Perca fluviatilis Linnaeus), as well as in the excretory-secretory products and extracts of mature and immature cestodes Triaenophorus nodulosus (Pallas, 1781) from the intestine of pike (Esox lucius Linnaeus). It was found that excretory-secretory products and extracts of both mature and immature T. nodulosus display varying degrees of inhibitory ability against proteases. A significant decrease in activity was noted under the action of the studied samples on the activity of commercial trypsin. Tapeworm extracts exhibit a greater inhibitory ability compared to excretory-secretory products. At the same time, the extract of immature worms inhibits the activity of proteases more strongly than that of mature ones. The inhibitory ability is more closely associated with the extract of worms lacking the brush border than with the tegumental brush border fraction.

Squalene Supplementation as a Novel to Increase PUFA Content in Fish Tissues.

Squalene is an antioxidant that plays an essential role in fat metabolism. The study aimed to assess the effect of squalene supplied in feed on the growth performance, health status, and fatty acid profiles of muscle and liver of Siberian sturgeon, rainbow trout, and Eurasian perch. The experimental feeds containing 0%, 0.5%, and 1.0% squalene were prepared for each fish species. Hematological and biochemical indices, liver histology, and fatty acid profiling of muscle and liver were analyzed. Squalene supplementation was safe for fish, and no negative influence on growth status was observed. However, changes in the values of hematological and biochemical indicators were found, including the level of triglycerides in the blood of rainbow trout, and cholesterol in the blood of Eurasian perch. The addition of squalene influences the nucleocytoplasmic index values in all fish offered feed containing 1% squalene. The retention of squalene in the liver and muscle of experimental Siberian sturgeon was observed in both 0.5% and 1.0% squalene levels of feed. The PUFA and docosahexaenoic acid increase was observed in all fish in groups with squalene addition. Dietary squalene increases the content of PUFAs in tissues of the examined species.

Lingering Effects of Legacy Industrial Pollution on Yellow Perch of the Detroit River.

We used yellow perch (Perca flavescens) captured at four sites differing in legacy industrial pollution in the Lake St. Clair-Detroit River system to evaluate the lingering sublethal effects of industrial pollution. We emphasized bioindicators of direct (toxicity) and indirect (chronic stress, impoverished food web) effects on somatic and organ-specific growth (brain, gut, liver, heart ventricle, gonad). Our results show that higher sediment levels of industrial contaminants at the most downstream Detroit River site (Trenton Channel) are associated with increased perch liver detoxification activity and liver size, reduced brain size, and reduced scale cortisol content. Trenton Channel also displayed food web disruption, where adult perch occupied lower trophic positions than forage fish. Somatic growth and relative gut size were lower in perch sampled at the reference site in Lake St. Clair (Mitchell's Bay), possibly because of increased competition for resources. Models used to determine the factors contributing to site differences in organ growth suggest that the lingering effects of industrial pollution are best explained by trophic disruption. Thus, bioindicators of fish trophic ecology may prove advantageous to assess the health of aquatic ecosystems. Environ Toxicol Chem 2023;42:2158-2170. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Chronic poly(l-lactide) (PLA)- microplastic ingestion affects social behavior of juvenile European perch (Perca fluviatilis)

Juvenile perch were exposed to 2 % (w/w) poly(l-lactide) (PLA) microplastic particles (90–150 μm) in food pellets, or 2 % (w/w) kaolin particles, and a non-particle control food over 6 months. Chronic ingestion of PLA microplastics significantly affected the social behavior of juvenile perch, evident as a significantly increased reaction to the vision of conspecifics. PLA ingestion did not alter life cycle parameters, or gene expression levels. In addition to reactions to conspecifics, fish that ingested microplastic particles showed tendencies to decrease locomotion, internal schooling distance, and active predator responses. The ingestion of natural particles (kaolin) significantly downregulated the expression of genes related to oxidative stress and androgenesis in the liver of juvenile perch, and we found tendencies to downregulated expression of genes related to xenobiotic response, inflammatory response, and thyroid disruption. The present study demonstrated the importance of natural particle inclusion and the potential behavioral toxicity of one of the commercially available biobased and biodegradable polymers.

Changes of Activity of Energy and Ion Exchange Enzymes and the Energy Substrates Content in Tissues of Perca fluviatilis and Rutilus rutilus under Toxic Water Pollution

The paper deals with impact of toxic pollution on activity of energy and ion exchange enzymes in roach and perch. Significant changes in content of energy substrates in liver, gills and muscles of perch and roach were established depending on season and toxic load. The glycogen content in liver of perch specimens from the polluted lake (Kyrilivske) was lower than in specimens from the control lake (Babyne). Also, lower activity of SDH in muscles and gills of roach has been established. It should be noted that roach was characterized by higher variability of the studied enzymes' activity. This indicates the species specificity of the metabolic reactions of the studied fishes to counteract toxic pollution.

Molecular Analysis and Sex-specific Response of the Hepcidin Gene in Yellow Perch (Perca Flavescens) Following Lipopolysaccharide Challenge.

Hepcidin antimicrobial peptide (hamp) is active in teleosts against invading pathogens and plays important roles in the stress and immune responses of finfish. The response of hamp gene was studied in yellow perch (yp) (Perca flavescens) challenged with lipopolysaccharides to understand if this immunity response is sex-specifically different. The cloned hamp gene consists of an open-reading frame of 273bp and encodes a deduced protein of 90 amino acids (a.a.), which includes a signal peptide of 24 a.a., a pro-domain of 40 a.a. and a mature peptide of 26 a.a. Yp hamp involves 8 cysteine residues with 4 disulfide bonds, and a protein with an internal alpha helix flanked with C- and N-terminal random coils was modeling predicted. RT-qPCR was used to analyze the relative abundances (RAs) of hamp mRNA in the livers of juvenile female and male yellow perch challenged with lipopolysaccharide. The expression levels of hamp were significantly elevated by 3h (RA = 7.3) and then peaked by 6h (RA = 29.4) post-treatment in females but the peak was delayed to 12h (RA = 65.4) post-treatment in males. The peak mRNA level of challenged males was shown 7.6-fold higher than females. The post-treatment responses in both genders decreased to their lowest levels by 24h and 48h. Overall, female perch had an earlier but less-sensitive response to the lipopolysaccharide challenge than male.

Sea perch (Lateolabrax japonicus) autophagy related gene 5 promotes RGNNV infection via inhibiting RLRs-interferon signaling pathway

Autophagy-related gene 5 (Atg5), an essential component of autophagy machinery, is associated with innate immune responses. Here, the Atg5 of sea perch (Lateolabrax japonicus) (LjAtg5) was cloned and its role in regulating autophagy and interferon (IFN) response during red-spotted grouper nervous necrosis virus (RGNNV) infection was investigated. The LjAtg5 cDNA encoded a polypeptide of 275 amino acids with an APG5 domain, and had the closet genetic relationship with Micropterus salmoides Atg5. Autophagic detection showed LjAtg5 was conserved in inducing cell autophagy. Spatial expression analysis revealed LjAtg5 had a higher expression level in liver, brain, and kidney tissues of RGNNV-infected sea perch compared with the control group. In RGNNV-infected LJB cells, overexpression of LjAtg5 significantly increased the mRNA and protein levels of capsid protein, whereas knockdown of LjAtg5 led to the opposite effect, indicating LjAtg5 played a pro-viral role during RGNNV infection. Furthermore, dual luciferase reporter assay revealed LjAtg5 significantly suppressed the activation of sea perch type I IFN promoter in vitro, and overexpression of LjAtg5 strongly weaken the expression of genes related to the RIG-I-like receptors (RLRs) signaling pathway and IFN stimulated genes. These results suggested LjAtg5 promoted RGNNV infection by negatively regulating RLRs-IFN signaling pathway.

КОМПЛЕКСНИЙ ПІДХІД ДО ОЦІНКИ ЗАБРУДНЕННЯ ВАЖКИМИ МЕТАЛАМИ ЕКОСИСТЕМ МАЛИХ РІЧОК ЗАХІДНОГО ПОДІЛЛЯ

The metal content (Ferrum, Cobalt, Manganese, Zinc, Copper) in water, bottom sediments and tissues of freshwater fish (carp, crucian carp, pike, perch) from small rivers of Western Podillya (Seret, Strypa, Zolota Lypa) was studied. High concentrations have been found in the water and bottom sediments of the Ferrum and Manganese, which is probably due to the inflow of these metals from the bottom sediments in conditions of oxygen deficiency. The high content of mobile form of Ferrum, Cobalt, Manganese in the bottom sediments of the Zolota Lypa can lead to secondary pollution of the water column and pose a potential danger to aquatic organisms. Individual mechanisms of accumulation and distribution in the body of fish were established for different metals. Higher concentrations in the liver and gills of the studied fish species of Ferrum, Manganese and Zinc and significantly lower contents of Cobalt and Copper were observed. The metal content in fish tissues was characterized by high variability, had a pronounced tissue and species specificity. Correlation relations between metal content in water, bottom sediments and fish tissues from small rivers of Western Podillia are analyzed. Positive correlations have been established between the content of the gross form of Ferrum in the bottom sediments, in the gills of crucian carp, perch and pike and the liver of perch and pike. The amount of Manganese in the water correlated with the metal content in the gills of carp and pike. The increase in the amount of Zinc in the bottom sediments (gross form) led to its accumulation in the gills of all fish species, as well as in the liver of perch and pike, as evidenced by the high positive values of Pearson's coefficients (0.71-0.91). The Copper content in water and bottom sediments (gross form) correlated with their amount in the liver of perch and pike, which may serve as a bioindication of pollution of aquatic ecosystems by this metal.

Comparison of physicochemical properties of different tissues from China climbing perch Anabas testudineus and crucian carp Carassius auratus.

This study aimed to investigate nutrition in climbing perch Anabas testudineus which is an important nutritious economic freshwater fish in Asia and compare with Carassius auratus (crucian carp). Three kinds of tissues, including muscle, livers, and eggs, were isolated, respectively. Physicochemical properties including moisture, ash, protein, amino acids, fat, vitamins, and calcium contents in those tissues were determined. The results showed climbing perch muscle and liver contained less moisture, but more protein, amino acids, and vitamins than crucian carp muscle and liver. While moisture, ash, protein, and total amino acids contents of climbing perch egg were lower than those of crucian carp egg. Climbing perch egg had more fat, vitamins, and calcium than crucian carp egg. The amino acid profile was also performed, and 16 amino acids were identified and quantified in muscle, liver, and egg. Among tissues, the highest and lowest concentration of total amino acid content was found in crucian carp eggs and livers, respectively. Glutamic acid (Glu) and histidine (His) were the most and least amino acids in climbing perch and crucian carp tissues, respectively. Sixteen amino acids in climbing perch egg were less than those in crucian carp egg while it is an opposite case in muscle and liver, which amino acids of climbing perch tissues were more than those of crucian carp muscle and liver. Vitamin A of climbing perch was more than crucian carp in all three tissues, but vitamin E content in climbing perch liver was lower than that of crucian carp liver. Calcium content of muscle had no difference between two species. The abovementioned comparison of physicochemical properties of different tissues from China climbing perch and crucian carp will provide a necessary supplementary of freshwater muscle nutrition research, also was helpful for application of climbing perch.

Toxicity and Functional Tissue Responses of Two Freshwater Fish after Exposure to Polystyrene Microplastics.

Microplastics (MPs)’ ingestion has been demonstrated in several aquatic organisms. This process may facilitate the hydrophobic waterborne pollutants or chemical additives transfer to biota. In the present study the suitability of a battery of biomarkers on oxidative stress, physiology, tissue function and metabolic profile was investigated for the early detection of adverse effects of 21-day exposure to polystyrene microplastics (PS-MPs, sized 5–12 μm) in the liver and gills of zebrafish Danio rerio and perch, Perca fluviatilis, both of which are freshwater fish species. An optical volume map representation of the zebrafish gill by Raman spectroscopy depicted 5 μm diameter PS-MP dispersed in the gill tissue. Concentrations of PS-MPs close to the EC50 of each fish affected fish physiology in all tissues studied. Increased levels of biomarkers of oxidative damage in exposed fish in relation to controls were observed, as well as activation of apoptosis and autophagy processes. Malondialdehyde (MDA), protein carbonyls and DNA damage responses differed with regard to the sensitivity of each tissue of each fish. In the toxicity cascade gills seemed to be more liable to respond to PS-MPs than liver for the majority of the parameters measured. DNA damage was the most susceptible biomarker exhibiting greater response in the liver of both species. The interaction between MPs and cellular components provoked metabolic alterations in the tissues studied, affecting mainly amino acids, nitrogen and energy metabolism. Toxicity was species and tissue specific, with specific biomarkers responding differently in gills and in liver. The fish species that seemed to be more susceptible to MPs at the conditions studied, was P. fluviatilis compared to D. rerio. The current findings add to a holistic approach for the identification of small sized PS-MPs’ biological effects in fish, thus aiming to provide evidence regarding PS-MPs’ environmental impact on wild fish populations and food safety and adequacy.

Adult female European perch (Perca fluviatilis) from the Baltic Sea show no evidence of thiamine deficiency

Deficiency of thiamine (vitamin B1) has been demonstrated in several species in the northern hemisphere and is suggested as a cause for declining populations. European perch from the Baltic Sea show negative temporal trends for several health biomarkers and poor recruitment of unknown cause. In this study, thiamine status of perch liver from the Baltic Sea was studied with emphasis on seasonal variation. During spring the thiamine concentration increased, reached a higher level during the summer and then decreased again during autumn. Despite this variation the thiamine concentration was always sufficient in the perch liver. These results indicate that direct thiamine deficiency is an unlikely explanation for the health effects observed in adult female perch from the Baltic Sea.

Bioaccumulation of metals in tissues of Rutilus rutilus and Perca fluviatilis from lakes with poor ecological status – human health risk assessment

The aim of this study was to determine the levels of Na, K, Ca, Mg, Fe, Zn, Cu, Pb and Cd in the muscle, liver and gills of roach (Rutilus rutilus) and perch (Perca fluviatilis) from three polymictic and eutrophic lakes in poor ecological condition in north-western Poland. Metals in the waters of the lakes, as well as in the muscle, gills and livers of fish, were determined by atomic absorption. Oxygen deficits in summer and high concentrations of Cd and Pb were responsible for the low water quality of the lakes studied. Perch and roach showed a potential to accumulate metals from the water (bioconcentration factor >1). The lowest concentrations of Na, Fe, Zn, Cu, Pb and Cd were found in the fish muscle. The highest concentrations of Cd and Pb were recorded in the liver of both species. Differences in metal concentration between the species were mainly due to significantly higher levels of Fe, Cu and Zn in the muscle of the roach than in the perch (p < 0.05). A portion of 100 g/day of roach or perch muscle can be a complementary source of elements essential to the human diet, because Dietary Reference Intakes were below 2% for Fe, 5% for Na, Ca and Cu, and 10% for K, Mg and Zn. With regard to Pb and Cd levels, consuming the muscle of these fish from the studied lakes should not pose a health risk (Acceptable Daily Intake less than 1%).

Fluorinated Precursor Compounds in Sediments as a Source of Perfluorinated Alkyl Acids (PFAA) to Biota.

The environmental behavior of perfluorinated alkyl acids (PFAA) and their precursors was investigated in lake Tyrifjorden, downstream a factory producing paper products coated with per- and polyfluorinated alkyl substances (PFAS). Low water concentrations (max 0.18 ng L-1 linear perfluorooctanesulfonic acid, L-PFOS) compared to biota (mean 149 μg kg-1 L-PFOS in perch livers) resulted in high bioaccumulation factors (L-PFOS BAFPerchliver: 8.05 × 105-5.14 × 106). Sediment concentrations were high, particularly for the PFOS precursor SAmPAP diester (max 1 872 μg kg-1). Biota-sediment accumulation factors (L-PFOS BSAFPerchliver: 22-559) were comparable to elsewhere, and concentrations of PFAA precursors and long chained PFAA in biota were positively correlated to the ratio of carbon isotopes (13C/12C), indicating positive correlations to dietary intake of benthic organisms. The sum fluorine from targeted analyses accounted for 54% of the extractable organic fluorine in sediment, and 9-108% in biota. This, and high trophic magnification factors (TMF, 3.7-9.3 for L-PFOS), suggests that hydrophobic precursors in sediments undergo transformation and are a main source of PFAA accumulation in top predator fish. Due to the combination of water exchange and dilution, transformation of larger hydrophobic precursors in sediments can be a source to PFAA, some of which are normally associated with uptake from water.

Condition and Sperm Characteristics of Perch Perca fluviatilis inhabiting Boreal Lakes Receiving Metal Mining Effluents

One of the world’s largest, but low-grade, sulfide nickel deposits in northeastern Finland has been exploited by a bioheapleaching technology since 2008. Bioheapleaching is a relatively new, cost-effective technology, but humid climate, e.g., in boreal temperate environments, causes challenges to the management of the water balance in the ore heaps with wide catchment area, and the mining effluents have caused substantial metal and salting contamination of the receiving waterbodies. In our study, the impacts of metal-extracting bioheapleaching mine effluents on muscle and liver element concentrations, body condition, liver and testes mass, and sperm count and motility of male perch Perca fluviatilis were analysed. Liver, testes, and carcass mass of perch in relation to their length were lower in the mining-impacted lakes than in the reference lake, which may be due to the metal contamination, food availability, and energy demand under multistressor conditions. The sperm counts of the males in the mining-impacted lakes were lower, but the endurance of their sperm motility was longer than the endurance of sperm of the reference males. These findings suggested that the condition and sperm characteristics of perch were altered in lakes receiving metal mining effluents. Measured variables seem to be useful indicators for metal mining impacts on freshwater fish but only if high natural variation in these characteristics can be controlled by multiyear monitoring scheme.

Optimization of an MMPB Lemieux Oxidation method for the quantitative analysis of microcystins in fish tissue by LC-QTOF MS

Microcystins are toxic heptapeptides produced by cyanobacteria in marine and freshwater environments. In biological samples such as fish, microcystins can be found in the free form or covalently bound to protein phosphatases type I and II. Total microcystins in fish have been quantified in the past using the Lemieux Oxidation approach, where all toxins are oxidated to a common fragment (2-methyl-3-methoxy-4-phenylbutyric acid, MMPB) regardless of their initial amino acid configuration or form (free or protein bound). These studies have been carried out using different experimental conditions and employed different quantification strategies. The present study has further investigated the oxidation step using a systematic approach, to identify the most important factors leading to a higher, more robust MMPB generation yield from fish tissue in order to reduce the method detection limit. Field samples were quantified using an in-situ generated MMPB matrix matched calibration curve by isotope dilution with d3-MMPB via liquid chromatography coupled to time-of-flight mass spectrometry (LC-QTOF MS). This approach improves method's accuracy by taking into account of potential matrix effects that could affect the derivatization, sample prepation and instrumental analysis steps. The validated method showed 16.7% precision (RSD) and +6.7% accuracy (bias), with calculated method detection limits of 7.28 ng g−1 Performance of the method was assessed with the analysis of laboratory exposed Rainbow Trout (Oncorhynchus mykiss) to cyanobacteria as a positive control, where no microcystins were detected in the pre-exposure fish liver and fillet, low levels in the exposed fillet (65.0 ng g−1) and higher levels in the exposed liver (696 ng g−1). Finally, the method was employed for the analysis of 26 fillets (muscle) and livers of Walleye (Sander vitreus) and Yellow Perch (Perca flavescens) from Lake Erie, showing very low concentrations of microcystins in the fillet and higher concentrations in liver, up to 3720 ng g−1.

A study of the endohelminths of the European perch Perca fluviatilis L. from the central region of the Danube river basin in Slovakia.

The European perch Perca fluviatilis L. serves as a host of different endohelminths of Trematoda, Cestoda, Nematoda, and Acanthocephala. Its natural range covers freshwater basins throughout much of Europe, including the Danube. Since information about endohelminths of European perch from this international river basin has been rather sporadic, the parasitological examinations of 700 perch from the central region of the Danube river basin in Slovakia were performed in October 2017 and April 2018. The larval stages of Triaenophorus nodulosus (Cestoda) were found in cysts located in the perch liver and adults of Proteocephalus percae (Cestoda) were isolated from the intestine. The larval stages of Eustrongylides sp. (Nematoda) and metacercariae of Clinostomum complanatum (Trematoda), both potential causative agents of fish-borne zoonoses, were found in the musculature. Spatial and seasonal differences in the occurrence of currently detected helminths were discussed with data on biological and environmental conditions of particular sampling site.