Perch Liver Research Articles

The fish or the egg: Maternal transfer and subcellular partitioning of mercury and selenium in Yellow Perch (Perca flavescens)

Mercury (Hg) is a trace element of particular concern since it is ubiquitous in the environment and because its methylated form (MeHg) readily bioaccumulates and biomagnifies in food webs. This latter process leads to elevated Hg concentrations in fish and may thus induce toxicity. Maternal transfer of bioaccumulated contaminants to offspring is a suggested mechanism of impaired reproductive success in fish. The purpose of this study was to assess the toxicity potential of Hg during maternal transfer in Yellow Perch from Lake Saint-Pierre (Quebec, Canada) using a subcellular partitioning approach. We also evaluated potential protective effects of selenium, as this element has been shown to alleviate Hg toxicity through sequestration. A customized subcellular partitioning protocol was used to separate liver and gonad of Yellow Perch into various subcellular fractions. Results show that, in the liver, MeHg was primarily (51%) associated to the subcellular fraction containing cytosolic enzymes. Furthermore, 23% and 15% of MeHg was found in hepatic and gonadal mitochondria, respectively, suggesting that Yellow Perch is not effectively detoxifying this metal. There was also a strong relationship (R2 = 0.73) between MeHg bioaccumulation in the liver and MeHg concentrations in gonadal mitochondria, which corroborates the potential risk linked to MeHg maternal transfer. On the other hand, we also found that selenium might have a protective effect on Hg toxicity at a subcellular level. In fact, Se:Hg molar ratios in subcellular fractions were systematically above 1 in all tissues and fractions examined, which corresponds to the suggested protective threshold. This study provides the first assessment of subcellular Se:Hg molar ratios in fish. Since early developmental stages in aquatic biota are particularly sensitive to Hg, this study represents a step forward in understanding the likelihood for toxic effects in wild fish through maternal transfer.

Cumulative effects of municipal effluent and parasite infection in yellow perch: A field study using high-throughput RNA-sequencing

Multiple metabolic, immune and reproductive effects have been reported in fish residing in effluent-impacted sites. Natural stressors such as parasites also have been shown to impact the responses of organisms to chronic exposure to municipal effluent in the St. Lawrence River (Quebec, Canada). In order to comprehensively evaluate the cumulative impacts of anthropogenic and natural stressors on the health of yellow perch, differential mRNA transcription profiles were examined in juvenile females collected from effluent-impacted and upstream sites with low or high infection levels of the larval trematode Apophallus brevis. Transcriptomics was used to identify biological pathways associated with environmental exposure. In total, 3463 isoforms were differentially transcribed between sites. Patterns reflecting the combined effects of stressors were numerically dominant, with a majority of downregulated transcripts (68%). The differentially expressed transcripts were associated with 27 molecular and cellular functions ranging from cellular development to xenobiotic metabolism and were involved in the development and function of 13 organ systems including hematological, hepatic, nervous, reproductive and endocrine systems. Based on RNA-seq results, sixteen genes were measured by qPCR. Significant differences were observed for six genes in fish exposed to both stressors combined, whereas parasites and effluent individually impacted the transcription of one gene. Lysozyme activity, lipid peroxidation, retinol-binding protein and glucose-6-phosphate dehydrogenase were selected as potential biomarkers of effects to study specific pathways of interest. Lipid peroxidation in perch liver was different between sites, parasite loads, and for combined stressors. Overall, results indicated that juvenile yellow perch responded strongly to combined parasite and effluent exposure, suggesting cumulative effects on immune responses, inflammation and lipid metabolism mediated by retinoid receptors. The present study highlight the importance of using a comprehensive approach combining transcriptomics and endpoints measured at higher levels of biological organization to better understand cumulative risks of contaminants and pathogens in aquatic ecosystems.

Occurrence and bioconcentration of micropollutants in Silver Perch (Bidyanus bidyanus) in a reclaimed water reservoir

This study examined the occurrence of 49 micropollutants in reclaimed water and Silver Perch (Bidyanus bidyanus) living in a reclaimed water reservoir. The numbers of micropollutants detected in reclaimed water, Silver Perch liver, and Silver Perch flesh were 20, 23, and 19, respectively. Concentrations of all micropollutants in reclaimed water, except benzotriazole, were well below the Australian Guideline for Recycled Water (AGRW) values for potable purposes. The concentration of benzotriazole in reclaimed water was 675 ± 130 ng/L while the AGRW value for this compound was 7 ng/L. Not all micropollutants detected in the water phase were identified in the Silver Perch flesh and liver tissues. Likewise, not all micropollutants detected in the Silver Perch flesh and liver were identified in the reclaimed water. In general, micropollutant concentrations in the liver were higher than in the flesh. Perfluorooctane sulfonate (PFOS) was detected at a trace level in reclaimed water well below the AGRW guideline value for potable purposes, but showed a high and medium bioconcentration factor in Silver Perch liver and flesh, respectively. In addition, the risk quotient for PFOS was medium and high when considering its concentration in Silver Perch liver and flesh, respectively. Results reported here highlight the need to evaluate multiple parameters for a comprehensive risk assessment. The results also single out PFOS as a notable contaminant of concern for further investigation.

Temporal variations in kidney metal concentrations and their implications for retinoid metabolism and oxidative stress response in wild yellow perch (Perca flavescens)

The objective of this study was to determine if temporal variations in tissue metal concentrations are related to biomarkers of retinoid metabolism and oxidative stress responses in juvenile yellow perch (Perca flavescens). To this end, kidney metal (Cd, Cu and Zn) concentrations were measured in fish sampled in spring and fall 2012 in four lakes representing a wide range of water and sediment metal contamination in the Rouyn-Noranda (Quebec) region. Lakes Opasatica and Hélène were considered as reference lakes while lakes Dufault and Marlon were metal-contaminated. Kidney concentrations of Cd, Cu and Zn varied widely between spring and fall in fish from both clean and metal-contaminated lakes. An inter-lake difference in renal metal concentrations was only observed for Cd, with fish from Lake Marlon consistently displaying higher concentrations. In the spring, the concentrations of liver dehydroretinol, dehydroretinyl palmitate and total vitamin A esters were higher in fish sampled in the most contaminated lake. Strong temporal variations in the concentrations of these metabolites, as well as in the percentage of liver free dehydroretinol and the epidermal retinol dehydrogenase 2 transcription levels, were observed in fish living in the most metal-impacted lake, with generally higher values in the spring. In contrast to liver, in muscle, no clear seasonal variations in the concentrations of dehydroretinol, dehydroretinyl stearate or in the percentage of free dehydroretinol were observed in fish captured in the most contaminated lake. Temporal variations of traditional biomarkers of oxidative stress response were also observed in the most metal-impacted lake. For example, the transcription level of the gene encoding Cu/Zn superoxide dismutase-1 in liver and muscle catalase activity of perch sampled in the most contaminated lake were higher in spring than in fall. Positive relationships were found between kidney Cd concentrations and the transcription level of the gene encoding glucose 6-phosphate dehydrogenase, and all forms of retinoid concentrations in liver in spring, except with the percentage of free dehydroretinol where the correlation was negative. Our results translate to a state of stress caused by Cd and illustrate that temporal variations in tissue metal concentrations affect retinoid metabolism and antioxidant capacities in juvenile wild yellow perch. Overall this study contributes to highlight the importance of considering temporal variations when investigating the consequences of metal contamination on the physiology of wild fish.

Fish as a bioindicator of heavy metals pollution in aquatic ecosystem of Pluszne Lake, Poland, and risk assessment for consumer's health

Heavy metals content (Zn, Cu and Hg) were measured in gills, liver, gonads and muscles of perch, Perca fluviatilis (L.) and roach, Rutilus rutilus (L.) from Lake Pluszne (north-eastern Poland). Correlations between heavy metals levels and total length, weight, HSI, GSI and FCF were examined. As expected, muscles contained the significantly highest values of Hg (P ≤ .05). The concentrations of Zn were significantly higher in gills of roach and gonads of perch (P ≤ .05), while the liver of fish accumulated significantly more Cu than other organs (P ≤ .05). In all organs of perch the higher content of mercury was found (P ≤ .05). The value of Zn and Cu was highest in organs of roach (P ≤ .05) (with the exception of Zn in muscles P > .05). Sequence of metals in both species was Zn > Cu > Hg. Only in muscle tissue, Hg was significantly positive correlated with weight of roach (r = 0.811, P = .045) and perch (r = 0.652, P = .041), and total length of roach (r = 0.806, P = .005). A positive relationship was also observed between Zn concentration in gills of perch and their weight (r = 0.634, P = .049). In contrary, Zn in gills of roach decreased with weight (r = −0.693, P = .026)) and length (r = −0.668, P = .035). Cu concentration in liver of perch was statistically positively correlated with HSI (r = 0.717, P = .020), whereas Hg content in muscle tissue of roach with FCF (r = 0.643, P = .045). There was negative relationship between Hg in perch gonads and GSI (r = −0.808, P = .005). Metal pollution index (MPI) in gills, liver, gonads and muscles of roach was 7.68, 7.24, 6.77 and 3.13, respectively, whereas in these organs of perch was 3.25 (gills), 4.75 (liver), 5.84 (gonads) and 4.44 (muscles), therefore the contamination of each tissue ranged from very low contamination to low contamination. The concentration of mercury was lower than the maximum acceptable limit estimated by the Commission Regulation (EC) No 629/2008 of 2 July 2008. The values of HI and THQ were below 1, which means that consumption of these fish is not hazardous to the consumer.

Binding of trace elements (Ag, Cd, Co, Cu, Ni, and Tl) to cytosolic biomolecules in livers of juvenile yellow perch (Perca flavescens) collected from lakes representing metal contamination gradients.

Biomolecules involved in handling cytosolic metals in the liver of the yellow perch (Perca flavescens) were characterized in juvenile fish collected from 4 lakes constituting metal contamination gradients. Using size-exclusion liquid chromatography coupled to an inductively coupled mass spectrometer, we determined metal distributions among ligands of different molecular weights in the cytosol, before and after a heat denaturation step designed to isolate metallothionein-like peptides and proteins. Silver, Cd, and Cu found in the heat-stable protein supernatants were indeed largely present as metallothionein-like peptide complexes; but Co, Ni, and Tl, also present in the heat-stable protein supernatants, did not coelute with metallothionein-like peptides and proteins. This difference in metal partitioning is consistent with the known preference of "soft" metals such as Ag, Cd, and Cu(I) for thiolated ligands and the contrasting tendency of Co and Ni to bind to ligands with oxygen and nitrogen as donor atoms. Metal handling in the whole cytosol also reflected these differences in metal-binding behavior. For Cd and Cu, the importance of the molecular weight pool that includes metallothionein-like peptides and proteins increased relative to the other pools as the total cytosolic metal concentration ([M]cytosol ) increased, consistent with a concentration-dependent detoxification response. In contrast, for Ni and Tl the increase in [M]cytosol was accompanied by a marked increase in the high-molecular weight (670-33 kDa) pool, suggesting that hepatic Ni and Tl are not effectively detoxified. Overall, the results suggest that metal detoxification is less effective for Ni, Tl, and Co than for Ag, Cd, and Cu. Environ Toxicol Chem 2018;37:576-586. © 2017 SETAC.

Alteration of essential fatty acids in secondary consumers across a gradient of cyanobacteria

Cyanobacteria blooms pose an increasing threat to ecosystem services. Consequently, understanding their impacts on ecosystem function is important. Cyanobacteria are poor producers of long-chain essential fatty acids (LC-EFA; eicosapentaenoic, docosahexaenoic, and arachidonic acids) and are inadequate for primary consumer growth and reproduction. Higher-level consumers such as planktivorous fishes are hypothesized to be negatively impacted through disruption of LC-EFA availability and transfer up the food web. We tested this hypothesis by comparing fatty acids in yellow perch (Perca flavescens) and white perch (Morone americana) across a gradient of cyanobacteria densities spanning four sites in Lake Champlain and Shelburne Pond, Vermont, USA. Phytoplankton community composition and fatty acid content of seston and fish tissue (liver and muscle) were collected in June, August, and October 2013. Yellow perch liver and muscle tissue increased in percent composition of linoleic acid and α-linolenic acid and decreased in LC-EFA with increased cyanobacteria. Total EFA and arachidonic acid in white perch muscle were negatively related to cyanobacteria. White perch liver did not show any relationship between EFA and cyanobacteria. We conclude that both fish species experienced altered EFA coinciding with cyanobacteria blooms, consistent with disruption of LC-EFA transfer across multiple trophic levels.

Integrated spatial health assessment of yellow perch (Perca flavescens) populations from the St. Lawrence River, Quebec, Canada) part A: physiological parameters and pathogen assessment.

A multi-disciplinary approach was used to evaluate the health of yellow perch (Perca flavescens) in the St. Lawrence River (Quebec, Canada), which is experiencing a severe population decline in the downstream portion of the river. Physiological parameters, liver alterations, trace metal concentrations, parasite prevalence and abundance, stable isotope composition, and the presence/absence of the viral hemorragic septicemia virus (VHSV) were evaluated in perch collected at six sites along the river: Lake St. François, Lake St. Louis (north and south), Beauregard Island, and Lake St. Pierre (north and south). Trace metal concentrations in surface water were higher in Lake St. Louis and downstream of a major urban wastewater treatment plant discharge, indicating that this effluent was a significant source of Cu, As, Ag, Zn, and Cd. Levels of Pb in surface water exceeded thresholds for the protection of aquatic life in Lake St. Louis and were negatively correlated with body condition index in this lake. In Lake St. Pierre, Cu, Ag, and Cd bioaccumulated significantly in perch liver and lower body condition index and greater liver damage were observed compared to upstream sites. Parasite analyses indicated a higher abundance of metacercariae of the trematodes Apophallus brevis and Diplostomum spp. in Lake St. Louis, and VHSV was not detected in the liver of yellow perch for all studied sites. Overall, results suggested that the global health of yellow perch from Lake St. Pierre is lower compared to upstream studied sites, which could contribute to the documented population collapse at this site.

Seasonal Investigation of Selected Mineral Contents in Meat, Gills, and Liver of Perch (Perca fluviatilis L.) from Western Poland

Seasonal Investigation of Selected Mineral Contents in Meat, Gills, and Liver of Perch (Perca fluviatilis L.) from Western Poland

Concentrations of 18 Elements in Muscle, Liver, Gills, and Gonads of Sichel (Pelecus cultratus), Ruffe (Gymnocephalus cernua), and European Perch (Perca fluviatilis) in the Danube River near Belgrade (Serbia)

The analysis of 18 elements in muscle, liver, gills, and gonads of sichel (Pelecus cultratus), ruffe (Gymnocephalus cernua), and European perch (Perca fluviatilis), caught at a polluted segment of the Danube River near Belgrade, was carried out with the aim to expand the knowledge about the ecotoxicology of these species for monitoring purposes and the possible impact on human health. Generally, the elemental concentration significantly differed between species and tissues (p < 0.0001), and a statistical interaction between these two factors was observed (p < 0.0001). In muscle and liver, concentrations of Hg and Se were statistically higher in ruffe than in sichel and European perch. In gills, statistically highest concentrations of Mn, Sr, and Zn were found in sichel, and of Fe in European perch. In gonads, statistically highest concentrations of As were detected in sichel, of Zn in ruffe, and of Mn and Mo in European perch. The highest number of coefficients of partial correlations between fish weight and element levels was found in sichel (11 in total). Of all analyzed elements, Al and B had the highest number of partial correlations in tissues. The levels of Hg exceeded the maximum acceptable concentration (0.5 mg kg−1) in all muscle samples, which can pose a risk for human consumption. Different diet preferences of the investigated fish species resulted in a different accumulation of elements in tissues, and ruffe (as a species that consume mainly benthic macroinvertebrates) accumulated the highest level of Hg, which makes it suitable for monitoring of this element in water bodies.

Morphological alterations in the liver of yellow perch (Perca flavescens) from a biological mercury hotspot

Mercury (Hg) contamination is a global issue due to its anthropogenic release, long-range transport, and deposition in remote areas. In Kejimkujik National Park and National Historic Site, Nova Scotia, Canada, high concentrations of total mercury (THg) were found in tissues of yellow perch (Perca flavescens). The aim of this study was to evaluate a possible relationship between THg concentrations and the morphology of perch liver as a main site of metal storage and toxicity. Yellow perch were sampled from five lakes known to contain fish representing a wide range in Hg concentrations in fall 2013. The ultrastructure of hepatocytes and the distribution of Hg within the liver parenchyma were analyzed by transmission electron microscopy (TEM) and electron energy loss spectrometry (EELS). The relative area of macrophage aggregates (MAs) in the liver was determined using image analysis software and fluorescence microscopy. No relation between general health indicators (Fulton's condition index) and THg was observed. In line with this, TEM examination of the liver ultrastructure revealed no prominent pathologies related to THg accumulation. However, a morphological parameter that appeared to increase with muscle THg was the relative area of MAs in the liver. The hepatic lysosomes appeared to be enlarged in samples with the highest THg concentrations. Interestingly, EELS analysis revealed that the MAs and hepatic lysosomes contained Hg.

A Case Report of Acute Vitamin A Intoxication due to Ocean Perch Liver Ingestion

BackgroundChronic vitamin A intoxication is well known; however, there are few reports of acute vitamin A intoxication due to the ingestion of food rich in vitamin A, particularly in adults. Case ReportWe report a case of a 27-year-old man presenting with chief complaints of flushing, headache, nausea, and joint pain. He had consumed 800 g of grilled ocean perch liver the day before and had experienced numbness shortly after. Although physical examination revealed only facial flushing, we suspected acute vitamin A intoxication due to his diet history. On day 2 after ingestion, his serum retinol levels were elevated at 1577 ng/mL, which confirmed vitamin A intoxication. He returned for follow-up on day 4 after ingestion, by which time his presenting symptoms had improved, but he had developed desquamation of his facial skin. Why Should an Emergency Physician Be Aware of This?Emergency physicians should consider acute vitamin A intoxication in the differential diagnosis of patients with headache, flushing, desquamation, nausea, and vomiting of unknown etiology. Complete diet histories and checking vitamin A levels are essential for diagnosis. This report highlights the diagnostic difficulties associated with vitamin A intoxication and the importance of an accurate diet history.

Splenic lipidosis in intensively cultured perch, Perca fluviatilis L.

Macroscopically visible lipid deposition varying in size from pinpoint to 8-mm diameter was found in spleens of a population of intensively farmed perch, Perca fluviatilis L. over a 24-month rearing period. Large agglomerates of adipocytes distinguishable from surrounding normal tissue occurred in all individuals with spleen lipidosis. Several affected fish presented total dystrophy of large clusters of hepatocytes. Prevalence of lipidosis was 5.0% at 12 months and 16.6% at 24 months. There was no significant difference between fatty acid profiles of liver or perivisceral fat of perch with and without lipidosis except for linoleic, myristic, γ-linoleic, cis-eicosatrienic, palmitooleic acid. Body weight and hepatosomatic, perivisceral fat and splenosomatic indices were not associated with lipidosis. There was no significant effect of lipidosis on mortality or growth.

Ultrastructural Assessment of Granulomas in the Liver of Perch (Perca fluviatilis) Infected by Tapeworm

Granulomas caused by migration of larvae of a helminth parasite, Triaenophorus nodulosus, within the liver of perch (Perca fluviatilis) from Rimov Dam Lake (Czech Republic) were assessed by transmission electron microscopy. Lesions were found in the liver of 29 out of 34 perch examined (85.2%) and there were between 1 and 15 T. nodulosus larvae identified per host. Pathological changes were more severe in livers containing more granulomas. Within the granulomas, there were three concentric regions: an outer layer of fibrous connective tissue, a middle clear epithelioid layer and a central dark spindle cell layer. The outer layer contained mast cells, fibroblasts, thick collagen bundles and epithelioid cells. The granulomas contained few lymphocytes and macrophages. Hepatocytes adjacent to the granulomas showed pronounced degeneration (ranging from vacuolar degeneration to acute cellular swelling).

Biomarkers in European perch (Perca fluviatilis) liver from a metal-contaminated dam lake

The present study was carried out in three seasons — spring, summer and autumn in Topolnitsa Dam Lake (Bulgaria) which has been subjected to continuous contamination with trace metals due to copper extraction in the area. We investigated the trace metal levels in surface water and liver samples of European perch (Perca fluviatilis L.). We also linked the metal levels we determined with the various histological and biochemical changes which we observed. Lesions in the liver parenchyma were found to be degenerative and necrotic, as well as, they were presented as hyperemia which consequently leads to disturbances in the hepatic blood circulation. Activities of the hepatic enzymes lactate dehydrogenase (LDH), alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) were found to be significantly elevated, particularly in summer. Therefore, based on our results we could recommend that the investigated tissue and cell alterations may be successfully applied as reliable biomarkers for monitoring polluted with a mixture of trace metals freshwater ecosystems.

Content of calcium and phosphorus in the meat, gills and liver of perch (Perca fluviatilis L.) from the Wielkopolska Lakes District (Poland)

Content of calcium and phosphorus in the meat, gills and liver of perch (Perca fluviatilis L.) from the Wielkopolska Lakes District (Poland)

Multiple isotope analyses of the pike tapewormTriaenophorus nodulosusreveal peculiarities in consumer–diet discrimination patterns

Previous studies of dietary isotope discrimination have led to the general expectation that a consumer will exhibit enriched stable isotope levels relative to its diet. Parasite-host systems are specific consumer-diet pairs in which the consumer (parasite) feeds exclusively on one dietary source: host tissue. However, the small numbers of studies previously carried out on isotopic discrimination in parasite-host (ΔXP-HT) systems have yielded controversial results, showing some parasites to be isotopically depleted relative to their food source, while others are enriched or in equilibrium with their hosts. Although the mechanism for these deviations from expectations remains to be understood, possible influences of specific feeding niche or selection for only a few nutritional components by the parasite are discussed. ΔXP-HT for multiple isotopes (δ13C, δ15N, δ34S) were measured in the pike tapeworm Triaenophorus nodulosus and two of its life-cycle fish hosts, perch Perca fluviatilis and pike Esox lucius, within which T. nodulosus occupies different feeding locations. Variability in the value of ΔXP-HT calculated for the parasite and its different hosts indicates an influence of feeding location on isotopic discrimination. In perch liver ΔXP-HT was relatively more negative for all three stable isotopes. In pike gut ΔXP-HT was more positive for δ13C, as expected in conventional consumer-diet systems. For parasites feeding on pike gut, however, the δ15N and δ34S isotope values were comparable with those of the host. We discuss potential causes of these deviations from expectations, including the effect of specific parasite feeding niches, and conclude that ΔXP-HT should be critically evaluated for trophic interactions between parasite and host before general patterns are assumed.

Perch liver reaction to Triaenophorus nodulosus plerocercoids with an emphasis on piscidins 3, 4 and proliferative cell nuclear antigen (PCNA) expression

Histopathological lesions caused by plerocercoids of Triaenophorus nodulosus within the liver of perch, Perca fluviatilis, from Lake Trasimeno were studied. Livers harbored 1–3 parasite larvae and pathological alterations were more marked in those with 3 plerocercoids. In the liver, larvae were encysted, surrounded by a capsule of host tissue; two of 14 plerocercoids were necrotic. In infected livers, some hepatocytes showed degenerative changes, i.e. swelling and hydropic degeneration, notably those in close proximity to larvae. By comparison, hepatocytes in uninfected livers or in regions away from the point of infection appeared normal. The occurrence of macrophage aggregates (MAs) distributed among the mast cells (MCs) was observed around the encysted larvae. The cellular elements involved in the immune response within liver were assessed by immunohistochemical techniques and by the use of antibodies against the antimicrobial peptides piscidins 3 and 4, which revealed a sub-population of positive MCs. In infected livers, numerous MCs that were immunopositive to P4 and a few that were positive to P3 were found around T. nodulosus larvae. Histological sections of both uninfected and infected liver were immunostained with proliferative cell nuclear antigen (PCNA) antibody. Within the capsule and in close proximity to the parasite larvae, various cell types (i.e., MCs, fibroblasts and epithelioid cells) and a significantly higher number of PCNA-positive hepatocytes that were immunoreactive to PCNA were found compared to uninfected livers (ANOVA, P<0.05). No parasites of any type were found in gill, spleen, kidney or gonad of P. fluviatilis and the intestine of 3 perch were infected with few specimens of Acanthocephalus lucii.

Phylogenetic analysis and molecular methods for the detection of lymphocystis disease virus from yellow perch, Perca flavescens (Mitchell)

Lymphocystis disease is a prevalent, non-fatal disease that affects many teleost fish and is caused by the DNA virus lymphocystis disease virus (LCDV). Lymphocystis-like lesions have been observed in yellow perch, Perca flavescens (Mitchell), in lakes in northern Alberta, Canada. In an effort to confirm the identity of the virus causing these lesions, DNA was extracted from these lesions and PCR with genotype generic LCDV primers specific to the major capsid protein (MCP) gene was performed. A 1357-base pair nucleotide sequence corresponding to a peptide length of 452 amino acids of the MCP gene was sequenced, confirming the lesions as being lymphocystis disease lesions. Phylogenetic analysis of the generated amino acid sequence revealed the perch LCDV isolate to be a distinct and novel genotype. From the obtained sequence, a real-time PCR identification method was developed using fluorgenic LUX primers. The identification method was used to detect the presence/absence of LCDV in yellow perch from two lakes, one where lymphocystis disease was observed to occur and the other where the disease had not been observed. All samples of fin, spleen and liver tested negative for LCDV in the lake where lymphocystis disease had not been observed. The second lake had a 2.6% incidence of LCD, and virus was detected in tissue samples from all individuals tested regardless of whether they were expressing the disease or not. However, estimated viral copy number in spleen and liver of symptomatic perch was four orders of magnitude higher than that in asymptomatic perch.

A kinetic study of accumulation and elimination of microcystin-LR in yellow perch (Perca flavescens) tissue and implications for human fish consumption.

Fish consumption is a potential route of human exposure to the hepatotoxic microcystins, especially in lakes and reservoirs that routinely experience significant toxic Microcystis blooms. Understanding the rates of uptake and elimination for microcystins as well as the transfer efficiency into tissues of consumers are important for determining the potential for microcystins to be transferred up the food web and for predicting potential human health impacts. The main objective of this work was to conduct laboratory experiments to investigate the kinetics of toxin accumulation in fish tissue. An oral route of exposure was employed in this study, in which juvenile yellow perch (Perca flavescens) were given a single oral dose of 5 or 20 μg of microcystin-LR (MC-LR) via food and accumulation in the muscle, liver, and tank water were measured over 24 h. Peak concentrations of the water soluble fraction of microcystin were generally observed 8–10 h after dosing in the liver and after 12–16 h in the muscle, with a rapid decline in both tissues by 24 h. Up to 99% of the total recoverable (i.e., unbound) microcystin was measured in the tank water by 16 h after exposure. The relatively rapid uptake and elimination of the unbound fraction of microcystin in the liver and muscle of juvenile yellow perch within 24 h of exposure indicates that fish consumption may not be a major route of human exposure to microcystin, particularly in the Great Lakes.