Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Perches”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed2000

Disease and gill lesions in yellow perch (Perca flavescens) exposed to oil sands mining-associated waters.

Adult yellow perch were stocked into experimental ponds designed to test the biological effects of aquatic reclamation alternatives currently being pursued by the oil sands mining industry. Water-quality characteristics of oil sands-influenced water in the experimental ponds included increased salinity and elevated trace organics associated with raw oil sands (bitumen). After 3 and 10 months of exposure to affected waters, perch gross pathologies including severe fin erosion and virally induced tumors were observed in exposed individuals. Gill histopathology revealed large aneurysms accompanied by a proliferation of chloride and epithelial cells in the interlamellar spaces. Gill pathologies were not paralleled by a decrease in plasma sodium, calcium, or chloride. The frequencies of gross pathologies and gill changes were correlated to the concentrations of the oil sands-related compounds. As inorganic and organic compounds associated with oil sands activities are highly intercorrelated, and the observed lesions and changes are not diagnostic of particular toxicants, it was not possible to isolate the causative chemical factor(s) responsible. The incidence of observed lesions and gill pathologies could not be conclusively linked to increased mortality rates observed in the exposed populations. Evidence of recovery in the pathologies was observed between 3 and 10 months of exposure, coincident with a stabilization in population numbers.

Animals↗
PubMed1994

Ectopic ossicles associated with metacercariae of Apophallus brevis (Trematoda) in yellow perch, Perca flavescens (Teleostei): development and identification of bone and chondroid bone.

This paper describes the development and tissues in mineralized ossicles in the musculature of Perca flavescens infected with metacercariae of the trematode Apophallus brevis. Analysis involved light microscopy, transmission and scanning electron microscopy, X-ray scanning electron microprobe analysis, and tetracycline labelling. Two to 14 days post-infection, fibroblast-like host cells stream towards the parasite cyst forming a fusiform cellular capsule. By 14 days post-infection the capsule differentiates into an inner hypertrophied layer, an extensive middle layer of fibroblast-like cells, and a thin outer layer of flattened fibroblast-like cells forming a fibrous sheath at the capsule/muscle interface. From 21-35 days post-infection, a bony tissue is deposited periosteally in an equatorial ring around the cyst. With time, additional tissue is secreted over the ring increasing its thickness and advancing the matrix front towards the poles of the ossicle. Plump osteoblast-like cells cover the developing ossicle and may become trapped within the matrix in lacunae encapsulated by collagen. By 63 days post-infection, medium-sized ossicles are morphologically similar to large cysts from perch captured in the wild; ovoid with two polarized canals, but lacking acellular or lamellar bone-like tissue. Mineralized ossicles contain calcium, phosphorus and oxygen. Large ossicles retrieved from perch given multiple doses of tetracycline revealed discrete fluorescent bands, indicative of incremental growth. Fully developed ossicles are composed of two skeletal tissues, an inner region of chondroid bone and an outer region of acellular, lamellar bone.

Animals↗
PubMed1994

Stimulation of oxyradical production of hepatic microsomes of flounder (Platichthys flesus) and perch (Perca fluviatilis) by model and pollutant xenobiotics.

Stimulation of hepatic microsomal NAD(P)H-dependent hydroxyl radical (.OH) production by model compounds, viz. menadione (2-methyl-1,4-naphthoquinone) and nitrofurantoin (N-(5-nitro-2-furfurylidene)-1-aminohydantoin), and pollutant xenobiotics, viz. benzo[a]pyrene (BaP) diones (products of microsomal BaP metabolism), duroquinone (tetramethyl-1,4-benzoquinone--present in pulp mill effluent), and the pesticide lindane (gamma-hexachlorocyclohexane), was examined in flounder Platichthys flesus. Duroquinone was also studied in perch Perca fluviatilis, a freshwater species used in studies of pulp mill effluents in the aquatic environment. Microsomal .OH production was detected by the oxidation of the scavenging agent 2-keto-4-methiolbutyric acid (KMBA), using FeCl3/EDTA as a promotor of the Haber-Weiss reaction (O2- + H2O2 = .OH+OH- + O2). All xenobiotics tested, except lindane, showed synergistic interactions with ferric/EDTA indicative of redox cycling of the xenobiotic. Inhibition of menadione- and nitrofurantoin-stimulated .OH production by superoxide dismutase (50% inhibition) and catalase (80%) indicated respectively the involvement of O2- and H2O2 in .OH production. Maximal rates of KMBA oxidation (Vmax in nmol ethylene/min/mg protein) were similar for NADH and NADPH for menadione (4.58-4.61) and duroquinone (0.26-0.3 [flounder] and 0.93-0.99 [perch]), higher for NADPH than NADH for nitrofurantoin (1.21 and 0.77), and higher for NADH than NADPH for BaP diones, decreasing in the order 1,6-dione (1.12 and 0.14), 3,6-dione (0.75 and 0.25), and 6,12-dione (0.31 and 0.09). Rates for lindane, lacking a redox cycling structure, were low (0.01-0.05). Apparent Km (app. Km) values for xenobiotic were 1-2 orders of magnitude lower for BaP diones than the other compounds. App. Km was lower for NADH than NADPH for 3,6-dione (1.23 and 1.66 microM) and 6,12-dione (0.85 and 1.81 microM), but the reverse of this was found for the 1,6-dione (1.41 and 0.78 microM). App. Km values were almost identical for menadione and duroquinone and lower for NADPH (32-44 microM) than NADH (346-382 microM). The reverse was seen for nitrofurantoin, viz., 76 microM (NADH) and 269 microM (NADPH). Hepatic 1000 g supernatants of P. flesus metabolized BaP to oxyradical-generating products, moreso for beta-naphthoflavone-induced than control fish, and production was reduced by UDP-glucuronic acid for the latter but not the former. The studies indicate a widespread potential for contaminant-stimulated oxyradical generation via redox cycling and other free radical interactions of xenobiotics and their metabolites.

Animals↗
PubMed1994

Protein content and cAMP-dependent phosphorylation of fractionated white perch retina.

In the retinas of teleost fish dopamine, released from interplexiform cells, modulates synaptic transmission at both the chemical and electrical synapses of retinal horizontal cells. This modulation is due to activation of adenylate cyclase and phosphorylation by protein kinase A, perhaps of the synaptic ion channel proteins themselves. In this study we have fractionated the white perch retina by Percoll density gradient centrifugation in order to identify proteins which coenrich with horizontal cells. In addition we have tested retinal fractions for phosphorylation by native cAMP-dependent kinase. Our findings indicate that there are at least 3 proteins of molecular weights 28, 43/44 and 50 kDa which coenrich with horizontal cells and 3 proteins of 30/31 kDa, 35 kDa (putative rhodopsin) and 48 kDa (putative arrestin) which coenrich with photoreceptor fractions. The 43/44 kDa phosphoprotein is a target for cAMP-dependent protein phosphorylation and thus is apparently an element of the dopaminergic modulatory pathway in perch horizontal cells.

Animals↗
PubMed1992

Amino acid sequence of the unique protamine from yellow perch.

By the criteria of gel electrophoresis, ion-exchange chromatography, and reverse-phase HPLC, yellow perch protamine behaves as a single component. This observation was confirmed by automated Edman degradation which gave a single unambiguous amino acid sequence PRRRRHAARPVRRRRRTRRSSRVHRRRRAVRRRR. Yellow perch protamine has 34 amino acids, including 21 arginines. It has two histidines, neither of which interrupts an arginine tract. It is unusual among fish protamines in not having a serine or threonine N-terminal to the second arginine tract, and is unique in not being a mixture of components.

Amino Acid Sequence↗
PubMed1989

Sexual, seasonal and tissue variation in the encystment of Cotylurus variegatus metacercariae in perch, Perca fluviatilis.

All of the 267 perch sampled from Lough Neagh between 1981 and 1983 were infected with the metacercarial cysts of Cotylurus variegatus. Sites of infection were the swim-bladder, pericardium, septum transversum and, to a lesser extent, the visceral cavity. The swim-bladder, particularly the anterior portion, was the site of heaviest infection. Visceral cysts were found chiefly in female fish and this may be related to reduced immunological defence and/or thinner body wall during the breeding season. The number of cysts recorded was not related to host length, suggesting that further parasite invasion is offset by cyst mortality possibly as a result of the host immunological response to the parasite. Highest mean worm burden was recorded between May and June. This corresponded to increased water temperature necessary for development of eggs and the breeding season (April-June) of the perch.

Animals↗
PubMed1991

A short-wavelength sensitive cone mechanism in juvenile yellow perch, Perca flavescens.

The retinal cone mosaic of adult yellow perch, Perca flavescens, consists of square units each having a central single cone surrounded by four identical twin cones. No cones are present at the corners of the square units. However, the cone types and organization of the retinal mosaic in juvenile P. flavescens has not been thoroughly described. We report here the presence of small, single cones at the corner positions of the square units in juvenile P. flavescens. Not every corner, nor every unit has these cones, and their distribution over the retina is not uniform. Microspectrophotometry places the visual pigment absorbance maximum of these short single cones in the region of 400 nm. Electrophysiological measurements of spectral sensitivity demonstrate a short-wavelength mechanism in juveniles that is absent, as are the small corner cones, in adults. Possible advantages of such a mechanism to juvenile perch are discussed.

Animals↗
PubMed1994

The inhibitory effects of indomethacin, nordihydroguaiaretic acid, and pyrrolidinedithiocarbamate on ovulation and prostaglandin synthesis in yellow perch (Perca flavescens) follicle incubates.

This study specifically determined the correlation between ovulation and ovarian prostaglandin F (PGF) and prostaglandin E (PGE) levels in yellow perch follicles treated with several eicosanoid synthesis inhibitors. In incubates treated with indomethacin (IM; .00001 to 10.0 micrograms/ml) there was a significant dose-dependent correlation between ovulation and PGF/PGE levels, and between the two prostaglandins (PGs), further implicating PGs in the control of yellow perch ovulation. In incubates treated with nordihydroguaiaretic acid (NDGA), a traditional lipoxygenase inhibitor, there was a significant correlation between ovulation and PGF levels, yet there was no correlation between PGE levels and ovulation. A free-radical scavenger, pyrrolidinedithiocarbamate (PDTC) inhibited ovulation in a dose-dependent manner yet there was no correlation between either PGF or PGE levels and this inhibition, indicating that PDTC may block ovulation at other steps that involve free-radicals.

Animals↗
PubMed2006

Long-term monitoring of the health status of female perch (Perca fluviatilis) in the Baltic Sea shows decreased gonad weight and increased hepatic EROD activity.

Annual investigations of the health status of female perch (Perca fluviatilis) were performed during 8-13 years in order to detect long-term, large-scale changes in the Baltic Sea. These background data are also meant to be used as baselines in recipient investigations at various point sources in the Baltic Sea. Fish were sampled at three coastal sites in Sweden: two in the Baltic Proper (since 1988) and one in the Bothnian Bay (since 1993). In all, 19 biochemical, physiological and histopathological variables were measured. By reflecting central functions of life, such as red blood cell functions, immune defence, liver function, biotransformation processes, intermediary metabolism, ion balance, and reproduction, the selected variables give a good picture of the health status of the fish. The most important observations were strong trends towards decreased gonadosomatic index (relative gonad size) and increased hepatic EROD activity in female perch in the Baltic Proper. Most of the other variables varied little between the years. The reduced gonad size and the EROD induction indicate that factors in the environment, e.g. the occurrence of pollutants, affect important physiological functions, such as reproduction and biotransformation processes, in fish even in a reference area in the Baltic Proper. It is urgent to make further studies in order to identify which pollutant(s) or other possible cause(s) are responsible for the observed biological effects.

Animals↗
PubMed2026

Genome-wide characterisation of the myosin light chain gene family in Chinese perch (Siniperca chuatsi) and its expression patterns in muscle fibre types and injury response.

The Class II myosin light chain (myl) genes in Chinese perch (Siniperca chuatsi) have not yet been systematically characterised, and relationships with muscle fibre specification, development, and injury-associated remodelling remain unclear. In this study, fast and slow muscle fibres were initially distinguished using myofibrillar ATPase histochemistry. Subsequently, genome-wide mining identified 16 Class II myl genes, comprising eight essential and eight regulatory light-chain subunits. Their conserved-domain features, chromosomal distribution, phylogenetic relationships and expression profiles were analysed. Transcriptomic profiling showed that summed myl transcript abundance was higher in fast muscle than in slow muscle, accounting for 67.2% of the pooled myl transcript pool across the two muscle types (paired t-test, raw P = 0.036). mylpfa, myl1 and mylz3 were the major fast-muscle-associated genes, whereas myl10, myl2b and myl13 were preferentially expressed in slow muscle at the transcript level. These patterns support these genes as candidate fibre-type-associated expression markers. Developmental profiling identified stage-associated myl expression patterns, including a possible expression shift between mylpfb and mylpfa. In the descriptive injury-repair time course (d0-d7), FPKM profiles indicated that fast-muscle-associated genes (mylpfa, mylz3 and myl1) were lower at d1 and recovered by d3, whereas several slow-muscle-associated genes showed biphasic transcript-level increases. The slow-muscle-associated RLC gene mylpfb showed a delayed expression peak at d7. Notably, the embryonic isoform myl6l showed a modest increase from approximately 2 FPKM at d0 to 4-5 FPKM after injury, suggesting a possible injury-associated expression pattern that requires further validation. Together, these findings provide a genome-wide description of the Chinese perch myl gene family and identify candidate fibre-type-associated genes and descriptive injury-associated isoform expression patterns.

Animals↗
PubMedDate not supplied

Cadmium uptake in isolated adrenocortical cells of rainbow trout and yellow perch.

Cadmium uptake was studied in isolated adrenocortical cells of rainbow trout (Oncorhynchus mykiss) and yellow perch (Perca flavescens) to test the hypothesis that the greater sensitivity of trout cells to Cd-induced disruption of cortisol secretion observed in previous studies is correlated to higher level of metal accumulation. There was no evidence for interspecies differences in accumulation level, and a specific transport mechanism of similar affinity has been characterized in both fish species. However, inhibition of Cd uptake by calcium was observed in rainbow trout exclusively. The free metal ion Cd(2+) and chlorocomplexes CdCl(n)(2-n) both contribute to Cd accumulation with different level of contribution between fish species. We conclude that interspecies differences in sensitivity to Cd endocrine disrupting effect are not necessarily related to different levels of metal accumulation but would rather be linked to transport pathways and metal speciation. Cadmium/calcium competition for uptake could be a determinant of the early Cd-induced impaired cortisol secretion in trout but not perch cells.

Adrenal Cortex↗
PubMed2006

Biochemical biomarkers in adult female perch (Perca fluviatilis) in a chronically polluted gradient in the Stockholm recipient (Sweden).

A battery of biochemical biomarkers and the SigmaPCB concentration in adult female perch (Perca fluviatilis) verified an aquatic pollution gradient with the city of Stockholm (Sweden) as a point source of anthropogenic substances. The investigation included both an upstream gradient, 46 km westwards through Lake Mälaren, and a downstream gradient, 84 km eastwards through the Stockholm archipelago. Besides the main gradient from Stockholm, there were strong indications of pollution coming from the Baltic Sea. The results indicated a severe pollution situation in central Stockholm, with poor health status of the perch, characterised by increased specific EROD activity in the liver, increased liver EROD somatic index, decreased AChE activity in the muscle, increased amount of DNA adducts in the liver, and a high concentration of biliary 1-pyrenol. In addition, laboratory exposure to common EROD inducers elicited an abnormal response, suggestive of chronic intoxication.

Acetylcholinesterase↗
PubMed2004

Are sex steroids involved in the sexual growth dimorphism in Eurasian perch juveniles?

Individual growth and food intake were monitored in Eurasian perch (Perca fluviatilis L.) juveniles (13.5+/-3.4 g initial body weight) to determine whether androgens and estrogens may mediate sex-related growth differences. Fish were individually tagged with chips and implanted with cocoa butter containing 20 microg of either 17alpha-methyltestosterone (MT) or 17beta-estradiol (E(2)) per gram of fish body; controls were implanted with cocoa butter without hormones. All fish were bled at the end of the experiment for measurement of E(2) in females and testosterone (T) in males (MT was not measured) and triiodothyronine (T3) in both genders. Survival, gonadosomatic index and hepatosomatic index were not affected by steroid treatments. Relative food intake (RFI), feed efficiency (FE) and specific growth rate (SGR) were higher in females than in males in all treatments. MT treatment significantly lowered RIF, FE and SGR in both sexes, while E(2) treatment showed no significant effect on growth and feeding parameters. In contrast to E(2) and T concentrations, T3 levels were significantly and positively correlated with SGR and RFI. The results provide evidence that MT may affect sexually related growth dimorphism by decreasing food intake and FE in Eurasian perch.

Animals↗
PubMed2004

Effects of sex steroids and their inhibitors on endocrine parameters and gender growth differences in Eurasian perch (Perca fluviatilis) juveniles.

Sex steroid inhibitors were used to characterize the effects of 17beta-estradiol (E2) and testosterone (T) on the sexual growth dimorphism of Eurasian perch juveniles. In experiment 1, growth responses to different doses of either E2 (25, 50, 75, and 100 mgkg(diet)-1) or fadrozole (Fa; 50 and 100 mgkg(diet)-1) were compared in triplicate tanks of 30 fish each during 85 days. In experiment 2, five diets containing (50 mgkg(diet)-1) Tamoxifen (Ta), Flutamide (Flu), Fa, E2, and T were tested in triplicate tanks of 20 fish each during 90 days. Steroid supplementation or inhibition increased or decreased E2 and T plasma levels. Moreover, E2 treatment induced a higher plasma vitellogenin level but decreased triidothyronine levels. Brain aromatase activity (AA) was lower in Fa-treated fish than in other groups. In experiment 1, E2 supplementation did not promote growth, but high doses had negative effects as did Fa. In experiment 2, a greater growth response was observed only in E2-treated females in relation to higher food intake (FI) not feeding efficiency. Fa also promoted growth and FI both in females and males during the last month of the experiment. Other treatments did not affect growth, but T treatment decreased FI in males. In conclusion, the results did not provide clear evidence for E2 action on sexual growth dimorphism, but showed that testosterone may decrease growth in males by decreasing food intake in Eurasian perch. Therefore, the acceleration of male-to-female growth differences with age may not be a result of promotion of growth in females by estrogens, but a consequence of a reduction in growth by increased secretion of androgens in males.

Animals↗
PubMed2004

Gonad development and plasma steroid profiles by HRGC/HRMS during one reproductive cycle in reference and leachate-exposed female perch (Perca fluviatilis).

Endocrine processes were studied in reference female perch (Perca fluviatilis) from Lake Djursjön and in leachate-exposed females from Lake Molnbyggen during one reproductive cycle. A high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) technique enabled the analysis of circulating sex steroids [progesterone (P), 17alpha-hydroxyprogesterone (17alpha-OHP), androstenedione (A), testosterone (T), estrone (E1), and 17beta-estradiol (E2)], the maturation-inducing hormone (MIH) 17alpha,20beta-dihydroxy-4-pregnen-3-one (17alpha,20beta-P), and glucocorticoids [11-deoxycortisol (11-DC) and cortisol]. Body and organ measurements, ratio of sexually mature (SM) females, and frequencies of body lesions, were also recorded. High frequencies of body lesions and a low ratio of SM females were generally found in Molnbyggen. These females also had lower gonadosomatic index (GSI) and liver-somatic index (LSI) in the early stages of vitellogenesis, indicating either a delayed onset of oogenesis or an impaired vitellogenesis. Non-reproducing females from both lakes showed a similar LSI cycle as SM females. Increasing T and A levels in SM females from Djursjön coincided with the GSI peak at the time of spawning. These two androgens were on several occasions lower in SM females from Molnbyggen, possibly the result of a disrupted 17,20-lyase activity of the P450 17alpha enzyme because only minor effects were observed on circulating P and 17alpha-OHP levels. E2 and E1 levels increased during vitellogenesis in females from both lakes, with E1 levels more closely resembling the peaks of A and GSI. Peak levels of 17alpha,20beta-P at the time of spawning confirmed its function as the MIH in perch, while the simultaneous peak of 11-DC suggests that it also may be involved in final maturation of the oocytes.

Animals↗
PubMed2004

Comparative study of the reproductive characteristics of XY male and hormonally sex-reversed XX male Eurasian perch, Perca fluviatilis.

In order to compare the reproductive capacity of XY male versus XX male (neomales) Eurasian perch (Perca fluviatilis), we determined the sperm quality (sperm concentration and motility) and reproductive characteristics such as gonadosomatic index (GSI), fertilization rate and sex steroid levels (testosterone, T; 17beta-estradiol, E2 and 11-ketotestosterone, 11KT) during the reproductive season. Median GSI was not significantly different between XY males (7.9%) and XX males (7.5%). Fertilization rates ranged between 30.0 and 98.0%. Sperm concentration ranged between 27.9 x 10(9) and 42.0 x 10(9) spermatozoa ml(-1). Median level of T, 11KT and E2 levels increased in the middle of the reproductive season (2136.0, 2409.0 and 3252.0 pg ml(-1), respectively) and decreased at the end (1657.0, 2006.6 and 431.0 pg ml(-1), respectively). Sperm motility was assessed by CASA and expressed by the curvilinear velocity (VCL), straight line velocity (VSL), average path velocity (VAP), linearity (LIN), percentage of motile sperm (% MOT) and motile concentration (MOC). Overall, there were not any significant differences between XY and XX males. In conclusion, no differences of reproductive capacities were observed between XY males and XX males suggesting that the last can be crossed with females to improve the productivity of Eurasian perch by producing all-female stock.

Animals↗
PubMed2002

Competition for minerals between Acanthocephalus lucii and its definitive host perch (Perca fluviatilis).

Concentrations of various essential and toxic elements (Ba, Ca, Co, Cu, Fe, Mg, Mn, Sr, Zn and Al, Ag, Cd, Cr, Ni, Pb, Tl) were analysed by inductively coupled plasma mass spectrometry in the acanthocephalan Acanthocephalus lucii and in different tissues of its host Perca fluviatilis. Nearly all the elements were found in significantly higher concentrations in the acanthocephalan than in the host tissues. Spearman correlation analysis revealed several strong inter-element associations within the organs of perch and within the parasites. Furthermore, statistical analysis revealed different competitive interactions. The concentrations of several essential elements (Ba, Ca, Fe, Mn, Sr and Zn) within the parasites decreased with an increasing number or weight of worms inside the intestine of the host. Additionally, the levels of some elements in the perch liver were negatively correlated with the weight of A. lucii in the intestine. Thus, it emerged that not only is there competition for essential elements between acanthocephalans inside the gut but there is also competition for these elements between the host and its parasites.

Acanthocephala↗
PubMed1996

Pathology of epizootic haematopoietic necrosis virus (EHNV) infection in rainbow trout (Oncorhynchus mykiss Walbaum) and redfin perch (Perca fluviatilis L).

The gross and histopathological lesions of epizootic haematopoietic necrosis virus (EHNV) infection in rainbow trout (Oncorhynchus mykiss Walbaum) and redfin perch (Perca fluviatilis L) were examined during epidemiological studies on an endemically infected trout farm and in experimentally infected fish of the same two species maintained in the laboratory. Intercurrent infections were common in rainbow trout in field outbreaks, producing a variety of lesions and clinical signs, but the following changes were considered due to infection with EHNV in rainbow trout, based on experimental infections. Clinically, moribund fish were dark in colour, inappetent and sometimes ataxic. Gross lesions included abdominal distension, swelling of the spleen and kidney, and, rarely, pale foci in the liver. Microscopical lesions included focal to extensive, acute renal haematopoietic necrosis; multiple tiny foci of acute hepatocellular necrosis; focal to extensive, acute splenic necrosis; mild branchial hyperplasia with occasional focal necrosis; congestion, oedema and necrosis in the wall of the swim bladder; and focal acute necrotizing myocarditis, necrotic cells and debris being prominent within the cardiac lumen (and within blood vessels throughout the body generally). Round to oval basophilic intracytoplasmic inclusions were commonly present in hepatocytes surrounding necrotic foci and were sometimes seen in cells in the interstitium of the kidney, or in the spleen. Less common lesions included focal necrosis of the pancreas, thyroid, pseudobranch, thymus and gastrointestinal crypt epithelium. Intercurrent infections were not observed in redfin perch; gross lesions included multiple pale foci in the liver, haemorrhages at the bases of the fins, swelling of the spleen and kidney, and focal haemorrhages in the gills. Microscopical lesions in haematopoietic kidney, liver, spleen and heart were similar to those in rainbow trout, but the livers had larger focal to locally extensive areas of necrosis. Thrombosis, haemorrhage and fibrinous exudate were common in the gills, and focal to extensive pancreatic necrosis was frequently found. Focal necrosis of the lamina propria of the intestine was also seen. Immunoperoxidase staining in both species revealed EHNV antigen associated with areas of necrosis and in inclusions.

Animals↗