First insight in element localisation in different body parts of the acanthocephalan Dentitruncus truttae using TEM and NanoSIMS.

Acanthocephalans, intestinal parasites of vertebrates, are characterised by orders of magnitude higher metal accumulation than free-living organisms, but the mechanism of such effective metal accumulation is still unknown. The aim of our study was to gain new insights into the high-resolution localization of elements in the bodies of acanthocephalans, thus taking an initial step towards elucidating metal uptake and accumulation in organisms under real environmental conditions. For the first time, nanoscale secondary ion mass spectrometry (NanoSIMS) was used for high-resolution mapping of 12 elements (C, Ca, Cu, Fe, N, Na, O, P, Pb, S, Se, and Tl) in three selected body parts (trunk spines, inner part of the proboscis receptacle and inner surface of the tegument) of Dentitruncus truttae, a parasite of brown trout (Salmo trutta) from the Krka River in Croatia. In addition, the same body parts were examined using transmission electron microscopy (TEM) and correlated with NanoSIMS images. Metal concentrations determined using HR ICP-MS confirmed higher accumulation in D. truttae than in the fish intestine. The chemical composition of the acanthocephalan body showed the highest density of C, Ca, N, Na, O, S, as important and constitutive elements in living cells in all studied structures, while Fe was predominant among trace elements. In general, higher element density was found in trunk spines and tegument, as body structures responsible for substance absorption in parasites. The results obtained with NanoSIMS and TEM-NanoSIMS correlative imaging represent pilot data for mapping of elements at nanoscale resolution in the ultrastructure of various body parts of acanthocephalans and generally provide a contribution for further application of this technique in all parasite species.

Effect of Abrasive Grain Size on the Abrasion Volume Loss of Subfossil and Recent Oak Wood in Three Characteristic Sections.

Subfossil wood is a valuable and rare material often used for production of expensive furniture and decorative artistic items of unique beauty. Its mechanical and tribological properties are still being studied and are considered specific due to the particular conditions of its long-lasting formation in aqueous sediment sludge. Various elements that have been impregnated into the wood tissue over many years make the machining and grinding of this type of wood rather difficult compared to normal recent wood. The main objective of this study was to determine the influence of the abrasive grain size of sandpaper on the abrasion volume loss of recent and two subfossil oak samples in three characteristic sections (cross, radial, and tangential). The results showed that the average size of abrasive grains and the orientation of the wood structure have an influence on the abrasion volume loss of all three samples. The phenomenon of the critical size of abrasive grains was observed in all samples and on all sections. As the size of abrasive grains increased to the critical size, the abrasive volume loss of the sample increased simultaneously. The lowest abrasion volume loss was observed on recent oak. In all samples, the lowest volume loss was measured on the cross sections, and the tangential and radial sections had mutually equal values. It was also found that the increase in the size of abrasive grains to a critical value resulted in the increasing value of the absolute difference between the abrasion volume loss of the cross, radial, and tangential section samples, while the relative relations between the abrasive volume loss values of three different sections (C/R, C/T, R/T) within the same grit of sandpaper remained quite similar.

Cafeteria Diet and High-Fructose Rodent Models of NAFLD Differ in the Metabolism of Important PUFA and Palmitoleic Acid without Additional Influence of Sex.

The objective of this study was to evaluate the influence of high-fat (HF) and cafeteria diet (CAF) diets and sex on the metabolism of important fatty acids in the liver and perirenal fat tissue. Dietary treatments induced changes in the fatty acid profile in comparison to the untreated group, but the characteristic differences between treated groups were also observable. The HF diet induced an increase in the content of C16:1n-7 and C18:1n-7 in the liver phospholipids (PL) and triglycerides (TG) and perirenal fat tissue compared to the control and CAF diet. The CAF diet induced a more drastic decrease in both n-3 and n-6 polyunsaturated fatty acids (PUFA), including depletion of eicosapentaenoic acid (EPA). The CAF diet also increased the content of n-6 docosapentaenoic acid (DPAn-6) in the liver and decreased it in the perirenal fat. Sex also had a significant influence on the fatty acid profile, but the variables with the highest differences between the CAF and HF treatments were identical in the male and female rats. In this study, we have established that two dietary models of non-alcoholic fatty liver disease (NAFLD) led to characteristic changes in the hepatic and perirenal fat fatty acid profile, in contrast to the control diet and in comparison with each other. These differences could play an important role in the interpretation of the experimental results of nutritional studies.

Toxicity prediction and effect characterization of 90 pharmaceuticals and illicit drugs measured in plasma of fish from a major European river (Sava, Croatia).

Chemical analysis of plasma samples of wild fish from the Sava River (Croatia) revealed the presence of 90 different pharmaceuticals/illicit drugs and their metabolites (PhACs/IDrgs). The concentrations of these PhACs/IDrgs in plasma were 10 to 1000 times higher than their concentrations in river water. Antibiotics, allergy/cold medications and analgesics were categories with the highest plasma concentrations. Fifty PhACs/IDrgs were identified as chemicals of concern based on the fish plasma model (FPM) effect ratios (ER) and their potential to activate evolutionary conserved biological targets. Chemicals of concern were also prioritized by calculating exposure-activity ratios (EARs) where plasma concentrations of chemicals were compared to their bioactivities in comprehensive ToxCast suite of in vitro assays. Overall, the applied prioritization methods indicated stimulants (nicotine, cotinine) and allergy/cold medications (prednisolone, dexamethasone) as having the highest potential biological impact on fish. The FPM model pointed to psychoactive substances (hallucinogens/stimulants and opioids) and psychotropic substances in the cannabinoids category (i.e. CBD and THC). EAR confirmed above and singled out additional chemicals of concern - anticholesteremic simvastatin and antiepileptic haloperidol. Present study demonstrates how the use of a combination of chemical analyses, and bio-effects based risk predictions with multiple criteria can help identify priority contaminants in freshwaters. The results reveal a widespread exposure of fish to complex mixtures of PhACs/IDrgs, which may target common molecular targets. While many of the prioritized chemicals occurred at low concentrations, their adverse effect on aquatic communities, due to continuous chronic exposure and additive effects, should not be neglected.

Author Correction: Growth, health aspects and histopathology of brown bullhead (Ameiurus nebulosus L.): replacing fishmeal with soybean meal and brewer's yeast.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Author Correction: Cumulative impact of anti-sea lice treatment (azamethiphos) on health status of Rainbow trout (Oncorhynchus mykiss, Walbaum 1792) in aquaculture.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Growth, health aspects and histopathology of brown bullhead (Ameiurus nebulosus L.): replacing fishmeal with soybean meal and brewer's yeast.

A ten-week feeding trial was carried out to investigate the effects of replacing fishmeal (FM) with soybean meal (SBM) and brewer's yeast (BY) on growth performance, blood parameters, oxidative stress and micromorphology of liver and intestines in brown bullhead (Ameiurus nebulosus L.). Fish were fed nine feeds in which FM was replaced with 25%, 50%, 75% and 100% SBM (K1, K2, K3 and K4) and 17% + 8%, 42% + 8%, 67% + 8% and 92% + 8% of SBM/BY combination (K5, K6, K7, K8). Growth indices showed greater outcomes for the K2 group in comparison to all other groups. A decrease in plasma cholesterol and triglycerides concentrations was found after FM replacement. Activity of SOD was higher in groups K4, K7 and K8. The early inflammatory indications with abnormal vacuolization of lamina propria and basal epithelium were present in diets K4 and K8. Hepatocytes were irregular in shape with signs of inflammatory reaction in diet K8. A decreased perimeter of hepatocyte nuclei was detected in all experimental diets when compared with the control. This study demonstrates that the optimal replacement of FM with SBM/BY in brown bullhead diets contains up to 50% of FM replaced with SBM in order to obtain advantageous growth performance and adequate health condition.

Cumulative impact of anti-sea lice treatment (azamethiphos) on health status of Rainbow trout (Oncorhynchus mykiss, Walbaum 1792) in aquaculture.

Despite its widespread use in aquaculture, the impact of chemical anti-sea lice treatment on salmonids following application in a commercial farm has not been previously reported. This work reports the cumulative effect of three consecutive anti-sea lice treatments using azamethiphos on the health status of aquaculture reared rainbow trout through the investigation of clinical chemistry, histopathology and proteome expression. The serum biomarkers showed decreasing trends in total protein, albumin and potassium concentrations and an average increase of total bilirubin and phosphate concentration towards the end of the treatment period. Principal component analysis clearly distinguished correlated pairs of biomarkers and also demonstrates a shift from acute to chronic effects as treatment progresses. Proteomic analysis confirmed alterations of proteins involved in clot formation, immune reaction and free heme binding. Tissue damage after the series of delousing treatments, exhibited increased deposits of hemosiderin. Results from this study suggest an impact of azamethiphos on trout health through intravascular haemolysis and consequently from pathophysiologic process of haemoglobin metabolism and its products, causing chronic kidney injury from iron deposits. This is the first report to demonstrate in fish the impact of active iron accumulation in different organs from physiological processes that can seriously impair normal function.

Aquatic bacterial contamination associated with sugarplant sewage outfalls as a microbial hazard for fish.

The aim of the study was to compare bacterial composition and load in waters and fish related to the wastewater treatment plant (WWTP), particularly waters and wild fish affected by sugarplant processing (sugar cane and sugar beet). Aeromonads were the most frequently isolated group from water and fish. A. hydrophila was a prevailing species in isolates from water, followed by A. veronii, Rheinheimera soli and Ochrobactrum anthropi. Of indicator bacteria for aquatic contamination from fish tissues, the most prominent were V. cholerae, Enterobacter cloacae and E. sakazakii. Sugar cane processing contributed to high viable cell counts at 37 °C while sugar beet processing contributed to high bacterial counts at 22 °C. Heterotrophs from gills of effluent fish were highest during sugar cane processing. Counts retrieved from fish skin were more uniform between effluent fish and fish from downstream waters. Antimicrobial resistance of bacteria isolated from water was high against amoxicillin, sulfamethoxazole, flumequine, norfloxacin and oxolinic acid in samples from the inflow of raw municipal wastewaters to WWTP, while resistance found in bacteria from the inflow of sugarplant mostly related to sulfamethoxazole and amoxicillin. The PCA analysis associated the occurrence of high heterotroph counts, P. aeruginosa, and intestinal enterococci on skin and gills with sugar cane, and yeasts and molds with sugar beet processing. Fish living in treated wastewaters and related water bodies could pose a microbial hazard if fished for human consumption, possibly causing infection when being handled and processed, as a risk of human pathogens penetrating fish tissues.

Evaluation of architectural and histopathological biomarkers in the intestine of brown trout (Salmo trutta Linnaeus, 1758) challenged with environmental pollution.

In the present study novel histopathological approach, using fish intestine as a sensitive bioindicator organ of pollution impact in the freshwater ecosystem, was proposed. Histopathological alterations were compared between native brown trout (Salmo trutta Linnaeus, 1758) from the reference (Krka River spring) and pollution impacted location (influence of technological/municipal wastewaters and agricultural runoff near the Town of Knin) of the karst Krka River in Croatia. In brown trout from both locations, severe parasitic infestation with acanthocephalan species Dentitruncus trutae was found, enabling evaluation of acanthocephalan infestation histopathology, which indicated parasite tissue reaction in a form of inflammatory, necrotic and hyperplastic response that extended throughout lamina epithelialis mucosae, lamina propria, and lamina muscularis mucosae. New semi-quantitative histological approach was proposed in order to foresee alterations classified in three reaction patterns: control tissue appearance, moderate (progressive) tissue impairment and severe (regressive and inflammatory) tissue damage. The most frequent progressive alteration was hyperplasia of epithelium on the reference site, whereas the most frequent regressive alterations were atrophy and necrosis seen on the polluted site. Furthermore, histopathological approach was combined with micromorphological and macromorphological assessment as an additional indicator of pollution impact. Among 15 observed intestinal measures, two biomarkers of intestinal tissue damage were indicated as significant, height of supranuclear space (hSN) and number of mucous cells over 100 µm fold distance of intestinal mucosa (nM), which measures were significantly lower in fish from polluted area compared to the reference site. Obtained results indicated that combined histological and morphological approach on fish intestinal tissue might be used as a valuable biological tool for assessing pollution impact on aquatic organisms. Therefore, semi quantitative scoring and multiparametric morphological assessment of intestinal tissue lesion magnitude should become a common approach to handle environmental pollution impact.

Assessment of river sediment toxicity: Combining empirical zebrafish embryotoxicity testing with in silico toxicity characterization.

Quantitative chemical analyses of 428 organic contaminants (OCs) indicated the presence of 313 OCs in the sediment extracts from Sava River, Croatia. Pharmaceuticals were present in higher concentrations than pesticides thus confirming their increasing threat to freshwater ecosystems. Toxicity evaluation of the sediment extracts from four locations (Jesenice, Rugvica, Galdovo and Lukavec) using zebrafish embryotoxicity test (ZET) accompanied with semi-quantitative histopathological analyses exhibited correlation with cumulative number and concentrations of OCs at the investigated sites (10.05, 15.22, 1.25, and 9.13 µg/g respectively). Toxicity of sediment extracts and sediment was predicted using toxic unit (TU) approach and persistence, bioaccumulation and toxicity (PBT) ranking. Additionally, influential OCs and genes were identified by graph mining of the prior knowledge informed, site-specific chemical-gene interaction models. Predicted toxicity of sediment extracts (TUext) was similar to the results obtained by ZET and associated histopathology with Rugvica sediment being the most toxic, followed by Jesenice, Lukavec and Galdovo. Sediment TU (TUsed) favoured OCs with low octanol-water partition coefficients like herbicide glyphosate and antibiotics ciprofloxacin and sulfamethazine thus indicating locations containing higher concentrations of these OCs (Galdovo and Rugvica) as the most toxic. Results suggest that comprehensive in silico sediment toxicity predictions advocate providing equal attention to organic contaminants with either very low or very high log Kow.

Embryotoxic and genotoxic effects of sewage effluents in zebrafish embryo using multiple endpoint testing.

Wastewater treatment plant (WWTP) effluents are often complex mixtures of various organic and inorganic substances. Quality control of wastewaters and sludges has been regulated with measuring several physico-chemical parameters and sometimes using biological methods with non-specific responses, while synergistic action mechanisms of contaminants in such complex mixtures is still unknown. Toxic effects of wastewaters within and downstream of the WWTP in City of Virovitica, Croatia, were tested on zebrafish Danio rerio using a set of biomarkers that enabled an insight in wastewaters toxic potential on embryos at the cellular, tissue and the whole organism level during an early ontogenesis (24 and 48 hpf). Exposure of embryos to the wastewater samples from WWTP Virovitica increased mortality and abnormality rate. Heart rate, spontaneous movements and pigmentation formation were also markedly affected. Biochemical markers confirmed the presence of MXR inhibitors in all tested wastewater samples, indicating the increase of pollutant accumulation in the cell/organism. Also, a tendency of DNA damage decrease measured with Comet assay was evident in wastewater samples downstream from WWTP although control levels were not reached in any environmental sample. Histopathological analysis showed that exposure to tested samples resulted in impaired muscle organization, notochord malformation and retardation in eye and brain development at embryos 48 hpf. Furthermore, semi-quantitative histopathology assessment indicated increased percentage of embryo defects in river water sampled several kilometers downstream from the WWTP, confirming toxic potential of WWTP effluents. Extension of the zebrafish embryotoxicity test (ZET) with biochemical and histopathological biomarkers could serve as a guiding principle in biomonitoring of wastewater contamination.

Native Prussian carp (Carassius gibelio) health status, biochemical and histological responses to treated wastewaters.

The aim of this study was to assess the impact of treated wastewaters on native wild Prussian carp inhabiting effluent-receiving waters (ERC) receiving municipal and sugar plant treated wastewaters, further downstream waters (DW), and a detached canal unaffected by the WWTP activities. To that end, general fish health status was determined, including plasma biochemical, haematological, oxidative stress and tissue histopathological indices, over three seasons. The greatest tissue alterations were in fall in ERC during sugar beet processing, as hypertrophy of gill epithelial and interlamellar cells, necrosis and lymphocytic infiltration, hyperplasia and hypertrophy of renal tubules, distention of hepatic sinusoids. In fall the lowest leukocytes, lymphocytes and granulocytes (2467 ± 565, 1333 ± 264, 1133 ± 488 cells/µL respectively), as well as highest plasma ALP (52.7 ± 19.39 U/L) were measured. ERC in fall had the highest ammonium (20 mg/L), nitrite (1.48 mg/L), nitrate (13.4 mg/L), and lowest dissolved O2 (1.23 mg/L). Gill, kidney and liver alterations, and the highest plasma cholesterol (9.1 ± 1.98 mmol/L) were noted in DW fish in fall. Tissue morphology during sugar cane processing seems a consequence of cellular and structural tissue integrity loss. Structural heterogeneity of gills and spleen was enhanced with increasing concentrations of heavy metals and correlated with oxidative stress (SOD 392.5 ± 77.28 U/L). Monogenean infestation was moderate in ERC fish in all seasons compared with DW fish. Prussian carp biological responses to multiple stressors, measured by the effects of WWTP on blood and tissue parameters, reached far downstream and were not of localized nature. This study demonstrated that in aquatic environments impacted with complex contaminants acting synergistically, causal relationships between biological responses and environmental stressors should be interpreted. Integrated histopathological, haematological and biochemical findings are valuable biomarkers for native fish adaptive patterns and monitoring of water quality/pollution of freshwater ecosystems.

Multilevel ecotoxicity assessment of environmentally relevant bisphenol A concentrations using the soil invertebrate Eisenia fetida.

Bisphenol A (BPA) presents a serious threat to soil ecosystems, yet its effects on soil-inhabiting organisms are mostly unexplored. Therefore, the impact of environmentally relevant BPA concentrations on a terrestrial model organism, the earthworm Eisenia fetida, was assessed. Animals were cutaneously exposed to 100nM and 10µM BPA up to 10days (10-d). Next, a battery of biomarkers was used for ecotoxicological evaluation on a cellular, tissue and behavioural level. HPLC analysis showed that after a 10-d exposure, BPA accumulation reached a maximum of 2.50µg BPA per g of wet tissue weight. On the cellular level, up to 3-d BPA exposure caused increased lipid oxidation indicating oxidative stress. Histopathological assessment of cell wall and ovaries after 7- and 10-d BPA exposure showed multiple abnormalities, i.e. hyperplasia of epidermis, increased body wall thickness and ovarian atrophy. Detection of these changes was facilitated by a newly proposed semi-quantitative scoring system. Finally, behavioural changes were detected after only 3days of exposure to 100nM BPA. Altogether, the presented multilevel toxicity evaluation indicates high sensitivity of earthworms to low BPA doses.

Impact of treated wastewater on organismic biosensors at various levels of biological organization.

Relating the treated wastewater quality and its impact on organismic biosensors (Prussian carp, Carassius gibelio and earthworm, Eisenia fetida) was the main objective of the study. The impact on health status of fish living downstream, microbiological contamination and antimicrobial resistance, fish tissue structure, blood biochemistry, oxidative stress, genotoxic effects, as well as multixenobiotic resistance mechanism (MXR) was assessed. Treated wastewater discharged from the WWTP modified the environmental parameters and xenobiotic concentrations of the receiving surface waters. Potential bacterial pathogens from fish and respective waters were found in relatively low numbers, although they comprised aeromonads with a zoonotic potential. High resistance profiles were determined towards the tested antimicrobial compounds, mostly sulfamethoxazole and erythromycin. Histopathology primarily revealed gill lamellar fusion and reduction of interlamellar spaces of effluent fish. A significant increase in plasma values of urea, total proteins, albumins and triglycerides and a significant decrease in the activity of plasma superoxide dismutase were noted in carp from the effluent-receiving canal. Micronucleus test did not reveal significant differences between the examined groups, but a higher frequency of erythrocyte nuclear abnormalities was found in fish sampled from the effluent-receiving canal. Earthworms indicated to the presence of MXR inhibitors in water and sludge samples, thus proving as a sensitive sentinel organism for environmental pollutants. The integrative approach of this study could serve as a guiding principle in conducting evaluations of the aquatic habitat health in complex bio-monitoring studies.

Detection and diversity of aeromonads from treated wastewater and fish inhabiting effluent and downstream waters.

A two-season investigation of the wastewater treatment plant (WWTP) effluent, of related waters, sludge and fish across a wide area and 11 stations, with emphasis on Aeromonas spp. was conducted. Aeromonas veronii was the prevailing aeromonad isolated by MALDI TOF MS in the summer period. A rise of Aeromonas hydrophila was observed in summer in raw sewage, treated wastewater and effluent-carrying canal. The ratio of aeromonad species retrieved from fish tissues did not correspond with the water and sludge findings, as in spring in the effluent-carrying canal fish carried Aeromonas salmonicida ssp. salmonicida and Aeromonas bestiarum, while in summer mainly A. veronii and Acinetobacter johnsonii were isolated from fish tissues in the same location. No correlation was established between fecal coliforms/enterococci and aeromonad occurrence. All retrieved Aeromonas species demonstrated a distinct spectral pattern, with peaks showing unique mass distribution ranging from 4000 to 10,000Da. Hierarchical clustering separated aeromonads of all isolated species and clustered closely related strains together. Resistance was determined towards amoxicillin, and frequently towards sulfamethoxazole and erythromycin. In summer, a high proportion of water and sludge Aeromonas species demonstrated multiple resistance patterns towards five or more antimicrobials. The quinolone resistance of water aeromonads was mostly related to A. veronii. There are potential health concerns regarding aeromonad exposure amongst recreational fishermen who come into contact with fish inhabiting waters downstream from the WWTP, and WWTP workers who are occupationally exposed to wastewaters and their aerosols.

Indication of metal homeostasis disturbance in earthworm Eisenia fetida after exposure to semi-solid depot sludge.

Treated sewage sludge is commonly used in agriculture as fertilizer. It is, therefore, necessary to determine possible detrimental influences of sludge application on soil contamination and accumulation of contaminants in tissues of terrestrial animals, which in the long run could also have undesirable effects on humans. With that aim, the study was performed using earthworm Eisenia fetida as test organism and semi-solid depot sludge from a wastewater treatment plant as exposure media. The concentrations of 26 metals/metalloids were determined in depot sludge, and their bioaccumulation was estimated in whole tissue of E. fetida, and for the first time in the soluble tissue fraction, which represents metal fraction available for metabolic requirements and toxic effects. Obtained results have revealed acceptable levels of several elements (Cd, Cr, Cu, Ni, Pb, Zn) in depot sludge, when compared to currently valid regulations, and only moderate accumulation of some elements (e.g. As, Ba, Cd, Co, Fe, Tl, V, and Zn) in earthworms, as a consequence of exposure to depot sludge. However, a concentration increase after exposure to depot sludge was observed in E. fetida for several elements (Cd, Mo, and Zn), which were present in lower concentrations in the exposure mixtures than in soil. Contrary, a concentration decrease was observed for Cs, Mn, and Rb, although they were present in higher concentrations in depot sludge than in soil. It was an indication of disturbance in metal homeostasis in earthworms, possibly caused by exposure to complex mixture of contaminants present in depot sludge. The cumulative effect of exposure to a number of various contaminants (inorganic, organic, microbiological and pharmaceutical), even if each of them was not present in very high concentrations, could have caused distress in earthworms exposed to depot sludge.

Evaluation of histopathological alterations in the gills of Vardar chub (Squalius vardarensis Karaman) as an indicator of river pollution.

Quantification of histopathological alterations in the gills of Vardar chub (Squalius vardarensis Karaman) was performed in 2012 in rivers of north-eastern Macedonia, with the aim to examine the effects of water quality in the rivers (Zletovska and Kriva River-impacted by active Pb/Zn mines; Bregalnica River-contaminated by agricultural waste). The biological alterations in chub were classified as: circulatory disturbances, regressive and progressive changes, but their severity differed. Altogether the mildest changes were observed in the gills of chub from the Bregalnica River, a less polluted river, whereas mining impacted rivers were characterized by more severe alterations. In the gills of chub from the Zletovska River, which is highly contaminated with numerous metals, sulphates and chlorides, the highest lesion indices were found for the regressive changes of both epithelium and supporting tissue, with typical lesions referring to atrophy, thinning and lifting of epithelial cells, necrosis of epithelium and chloride cells, as well as deformations of lamellar cartilaginous base. Gill damages of chub from the Kriva River were overall milder compared to the Zletovska River, in accordance with pollution status. In the gills of chub from that river, progressive changes were more pronounced, specifically severe hyperplasia of mucous cells and epithelium in the interlammellar space, leading to fusion of lamellae, as well as hypertrophy of chloride cells. The comparison between seasons indicated higher intensity of progressive changes in all three rivers in autumn, when water level was very low, and consequently, water contamination was more pronounced due to concentration effect. The pattern and severity of histopathological alterations in the chub gills reflected differences in contamination levels and type of contaminants in different rivers and sampling periods, and thus have been proven as a valuable indicator of water quality.

The effect of artificial feed on blood biochemistry profile and liver histology of wild saddled bream, Oblada melanura (Sparidae).

Floating fish farms attract a great number of wild fish species, changing their behaviour and physiology. The saddled bream, Oblada melanura, sampled from populations aggregated around the Adriatic fish farm and from natural/control populations, were analysed for differences in eleven blood biochemistry parameters and liver histomorphology. The levels of lactate dehydrogenase (LDH), alkaline phosphatase (ALKP) and urea (URE) in cage-associated saddled bream (428.00±SD 321.56 U/L, 86.13±SD 39.87 U/L and 0.05±SD 0.16 mmol/L, respectively) were significantly lower than those observed in the control specimens (1047.06±SD 505.56 U/L, 125.75±SD 34.70 U/L and 1.99±SD 0.73 mmol/L, respectively). In contrast to that, concentrations of aspartate aminotransferase (AST) in cage-associated fish (87.63±SD 132.34 U/L) were higher than values noted for the control population (6.55±SD 5.90 U/L). URE and AST presented the main variables contributing to the discrimination between two analysed populations. One-way ANOSIM based on the blood parameters showed significant difference between saddled bream that fed around cages and those from the remote waters (R=0.697; P < 0.01). Hepatocytes of cage-associated fish contained large cytoplasmatic clear spaces indicating excessive accumulation of fat in the hepatocyte cytoplasm. All observed differences can be attributed to contrasting feeding behaviour of sampled populations but basic nutritional differences between them should be quantified in the future. Moreover, further research is necessary to detect their impact on the health status of the fish.