The significance of myxosporean infections in roach, Rutilus rutilus L., in different habitats

Abstract. Two Myxobolus species, M. pseudodispar and M. ellipsoides , and two Myxidium species, M. rhodei and M. pfeifferi , were found in roach, Rutilus rutilus L., from three different locations in northern Greece, northern England and Scotland. Their prevalence, distribution in the host and pathology were studied. In the ease of M. rhodei , the pathological changes were quantitatively evaluated by computer-based image analysis, and the results expressed in terms of area and volume of organs affected. The pathology of M. pfeifferi was associated with trophozoites in the bile duets and the infection ranged from mild to severe. In the severe eases, degeneration of duetal mucosa sometimes progressed to focal hepatitis. Myxidium rhodei was found in the kidneys as large cysts containing mature and immature spores (Type A cysts), and less often, in the form of small concentric cysts (Type B) which contained no obvious spores but which were characterized by a marked host response giving the appearance of focal granulomas. Type A cysts were also found in liver and spleen, and Type B cysts in the heart. Trophozoites of M. rhodei were observed in only a few eases and occurred in enlarged renal corpuscles in which the capillary tuft was atrophied and compressed. The pathology of M. rhodei was significant due to the enlargement of glomeruli from four to seven times their normal size and with an estimated increase in volume of 54 to 78 times. In addition to the functional damage to the glomeruli, there was also damage of the surrounding interstitial tissue and tubules as a result of the pressure from these enlarged glomeruli. The two myxobolid species were considered to be mainly specific to the kidney with no serious pathology in this organ, but caused significant pathology in the muscles ( M. pseudodispar ) and gills ( M. ellipsoides ).     

Factors affecting between-lake variation in the occurrence of epidermal papillomatosis in roach, Rutilus rutilus (L.)

The theory of island biogeography predicts that the probability of a species occupying an island depends on a dynamic equilibrium between extinction and colonization. Epidermal papillomatosis is a disease manifesting as skin tumours on fish. We studied the factors affecting the occurrence of the disease in roach, Rutilus rutilus (L.), in 34 lakes. The results of discrimination analysis suggest that maximum depth, percentage of the drainage area of the lake covered by lakes in the vicinity and altitude best identified diseased lakes. Comparison of diseased and non-diseased lakes revealed that lake area could also be regarded as a variable contributing to the occurrence of the disease. The sampling date, proportion of males and mean length of fish did not discriminate between the lakes. The probability of the disease occurring was highest in large, deep, low-altitude lakes which had a high percentage of lakes in their vicinity. Thus, the results indicate that the colonization and extinction processes probably contribute to the occurrence of papillomatosis in roach, as predicted by the theory. Furthermore, the large natural variation in the occurrence of the disease could mask possible environmental effects and between-lake comparisons should be interpreted with caution when using the fish-papillomatosis system as an indicator of environmental stress.     

Parasitism, condition and number of front head breeding tubercles in roach (Rutilus rutilus L.)

Abstract –  In a previous study on the male roach, Rutilus rutilus , we found a positive correlation between sexual ornamentation, breeding tubercles (BTs) on lateral sides and parasite resistance. As a continuation of that study, we examined another measure of sexual ornamentation – number of BTs on front head – of male roach from five populations. BTs on head correlated positively with fish size in two populations and with condition in one population, but not with parasite resistance (proportion of dead parasites) in any of the populations. Moreover, head BTs correlated negatively with the number of two parasite species ( Rhipidocotyle campanula and Myxobolus mülleri ) in two populations, but positively with the number of a third parasite ( Raphidascarus acus ) in one population. In addition, a negative correlation with spleen size was found in one population. The present results suggest that head BTs of male roach – although the patterns vary between populations – may signal condition and parasite load, but not resistance, in contrast to lateral BTs. Therefore, our results are in line with the hypothesis of multiple-message sexual ornaments.     

Density and temperature dependence of gill net catch per unit effort for perch, Perca fluviatilis, and roach, Rutilus rutilus

Abstract  The densities of perch, Perca fluviatilis L., and roach, Rutilus rutilus (L.), were estimated in six and three lakes, respectively, using mark–recapture and ranged from 25–1064 perch ha⁻¹ and 865–2749 roach ha⁻¹. Effects of fish density, net type and water temperature on catch-per-unit-effort (CPUE) were analysed by generalised linear models (GLM) and generalised additive models (GAM). GAMs were fitted to estimate the simultaneous linear and nonlinear effects of temperature and density on CPUE. These models showed significant nonlinear effects of density on CPUE – mostly for perch, and also for both species at high densities. The models also revealed that both species had distinct density–temperature criteria of expected maximum CPUE and zero CPUE values. Because of the nonlinear relationship between CPUE and density, it was concluded that CPUE should be used with caution as a proxy of density.     

Isolation and structural characterization of hepatic metallothionein from the roach (shape Rutilus rutilus L.)

Metallothioneins (MTs), considered as metal biomarkers by many authors, are very conserved proteins that present great interests in phylogenetical studies. This paper reports the purification of the hepatic MT from the roach (Rutilus rutilus). After extensive reverse-phase HPLC, the sequence of the MT was established by a combination of techniques including automated Edman degradation, mass spectrometry and enzymatic treatment. Sequence comparison with other fishes or mammalian MTs showed considerable identities and a high conservation in cysteine residues positions. MTs of roach and goldfish that both belong to the same family (Cyprinidae) share 97% identity. Ninety five% identity were found between roach and stone loach (Cypriniforms, Cobitidae) MTs. Only 77% identity were found with pleuronectiforms or salmoniforms. This sequence brings a new element in the study of the phylogenetical relationships among teleost species.     

Progestogen metabolism by ovaries of the roach (Rutilus rutilus L.) and the rudd (Scardinius erythrophthalmus L.)

Roach ovaries converted 17-hydroxyprogesterone to 17,20-dihydroxy-4-pregnen-3-one (17,20P) and to glucuronides of testosterone and 17,20P. Small amounts of 5-pregnane-3- and -3, 17, 20-triols, 7-hydroxy-5-reduced metabolites and 17,20-dihydroxy-4-pregnen-3-one (17,20P) were also formed. Rudd ovaries converted this substrate mainly to 17,20P, 5-pregnane-3- and -3,17,20-triols, 17,20-dihydroxy-5-pregnan-3-one and testosterone glucuronide. The main metabolites of progesterone with both species were 17,20P, 5-pregnane-3,17,20-triol and 7-hydroxy-5-reduced steroids. Rudd ovaries formed, in addition, 17,20-dihydroxy-5-pregnan-3-one from progesterone. The pattern of metabolites was markedly altered when the concentration of substrate was increased from 42ng to 1 µg or 100 µg. At the highest concentration, glucuronides and polar steroids were not detectable, while at low concentrations they accounted for over 50% of the metabolites. 20-Hydroxysteroid dehydrogenase was shown to have a very high capacity, producing 21–47 µg 17,20P from 100 µg 17-hydroxyprogesterone substrate with 200 mg ovarian tissue in 5h.     

Efficacy of artificial shelters for roach,Rutilus rutilus,against predators in the presence of reeds

Abstract Cormorants, Phalacocorax spp., have great potential to affect recreational fisheries and have increased substantially in abundance over the last decades in UK inland waters. Fabricated refuges provide a potential means of reducing fish losses, yet the benefits of such structures may be marginal if natural shelters are abundant and favoured, or if strong density‐dependence limits refuge use. This study examined the efficacy of artificial shelters in mesocosm enclosures that allowed standardised and replicated observations of roach, Rutilus rutilus (L.), distribution. When given a choice between occupying open water, simulated reedbeds and artificial brushwood shelters, roach used brushwood shelters extensively across a range of fish densities. When fish had a choice of occupying open water or reedbeds offering no overhead cover, they actively avoided reedbeds and used open water almost exclusively. Occupation of reedbeds was positively related to the amount of overhead cover they provided. When artificial brushwood shelters and reedbeds offered complete overhead cover, brushwood shelters were occupied twice as much as reedbeds. Artificial shelters may therefore have wide application in stillwaters with abundant reedbeds unless the reedbeds are coupled with extensive overhead cover.     

Factors affecting the intensity of epidermal papillomatosis in populations of roach, Rutilus rutilus (L.), estimated as scale coverage

Studies of epidermal papillomatosis in fish populations have only rarely focused on the intensity of the disease, i.e. the number and size of papillomas. Furthermore, the methods used to evaluate the intensity of papillomatosis have not been standardized. We tested the reliability of a method based on counting of scales covered by papilloma tumours in roach, Rutilus rutilus (L). In addition, we studied the frequency distributions of the number of scales covered by papillomas within populations, evaluated the correlation between the prevalence and mean intensity of the disease among populations and examined the intensity of papillomatosis in roach with respect to sex and size of fish. Reliability of the scale coverage method was high. Therefore, the method could offer an effective way to determine the intensity of papillomatosis in fish species with large scales. The frequency distribution of the scale coverage of papillomas was highly aggregated within all populations studied. The mean intensity of papillomatosis increased with the size of the fish and was higher in males than in females. However, there was no correlation between the mean intensity and prevalence of the disease among the 19 roach populations studied.     

Some observations of spawning by roach, Rutilus rutilus L., and bream, Abramis brama L., and their implications for management

Abstract. The spawning behaviour of roach, Rutilus rutilus L., and the spawning of roach with bream, Abramis brama L., is described with details of the nature of the spawning ground used at two sites in mid-west Britain. Roach appear to use traditional spawning grounds annually. Some female roach probably die as a result of damage inflicted by males during spawning. A simple exponential model is used to describe the relationship between temperature and the incubation period of roach eggs.     

A comparative study of the myxosporeans Myxidium rhodei Léger, 1905 and Myxidium pfeifferi Auerbach, 1908 in roach, Rutilus rutilus L.

Abstract. The morphology and dimensions of Myxidium rhodei and M. pfeifferi were studied in roach originating from two different geographic locations (Greece and UK) using both scanning and light microscopy. The measurements and morphology of both mature spores and immature stages (trophozoites and spores) were studied and compared. No differences were observed in the morphology of mature or immature spores of both species when examined under light and SEM. Furthermore, no differences were found in the dimensions of the mature spores of both species in all fish. However, immature spores of both species were found to be smaller but wider than mature ones in all organs and in both habitats. Size differences between the two species were only seen in immature spores, M. rhodei immature spores being always larger than those of M. pfeifferi. When comparing the dimensions of the spores between the two habitats, these were larger and wider in the Greek fish than those in the British fish. The information in this study suggests that, in roach, M. pfeifferi is undistinguishable from M. rhodei and that similar studies should be carried out on the tench, Tinca tinca L., the type host of M. pfeifferi.     

Ultrastructural studies on the cellular response of roach, Rutilus rutilus L., to the plerocercoid larva of the pseudophyllidean cestode, Ligula intestinalis

Abstract. Infections of roach, Rutilus rutilusL. , with the plerocercoid larva of Ligula intestinalis result in a pronounced host cellular response which consists of a leucocyte and connective tissue component. Using ultrastructural, histochemical and tracer techniques, three leucocyte cell types (L1, L2 and L3) have been observed. L1 cells, the most numerous cell type, pass through a number of characteristic developmental stages. Phagocytosis occurs in stages 1, 2 and 3. Stages 1 and 2 contain predominantly primary lysosomes and secondary lysosomes respectively, and in cells of stage 3 residual bodies are found which may be released following disruption of the cell at stage 4. The lysosomes and residual bodies do not contain acid phosphatase although arylsulphatase activity is present in all secondary lysosomes and residual bodies and in a few primary lysosomes. L1 cells are thought to be macrophages. L2 and L3 cells are relatively rare. The former contain granules resembling those found in mammalian eosinophils but which themselves are not eosinophilic or acid phosphatase and arylsulphatase positive. L2 cells are phagocytic and are thought to be neutrophils. L3 cells are also phagocytic and may represent macrophage precursors. Despite the presence of a host cellular response parasites survive apparently unharmed as long as the host lives. The significance of this is discussed.     

The differential effects of Ligula intestinalis (L.) plerocercoids on host growth in three natural populations of roach, Rutilus rutilus (L.)

Abstract – This study reports the differential effect of the pseudophyllidean cestode, Ligula intestinalis , on the growth rates of three fish populations of the roach, Rutilus rutilus , under field conditions. Here, we show that only one host-population is affected by parasite-induced gigantism in the first 2 years of host life. Paradoxically, this increase in fish growth is strongly correlated with the parasitic load in plerocercoid stages, in that only the roach population subjected to the heaviest parasitic pressure shows an enhanced growth of cestode-parasitized individuals. This host gigantism observed in only one locality is associated with parasite-induced fish mortality occurring, on average, one year earlier in this fish population when compared to other populations. We discuss the different reasons for this differential parasite effect on growth enhancement across host-population in natural settings. Whether the growth effects represent an adaptive response by the host or a manipulation by L. intestinalis of the host, remains to be elucidated.     

Eimeria scardinii Pellérdy and Molnár, 1968 in the kidneys of Rutilus rutilus (L,) and Scardinius erythrophthalmus (L.) from northern Greece

Abstract. The occurrence of Eimeria scardinii in roach, Rutilus rutilus (L.), and rudd, Scardinius erythrophthalmus (L.), from a lake in northern Greece is reported. The coccidium was found in the renal haemopoiettc tissue, mainly in the form of mature sporulated oocysts. The morphology and dimensions of the parasite, as well as the host reaction, were very similar in both species of fish examined. The overall prevalence of infection in roach and rudd was 6·67% and 6·3%, respectively. The prevalence of infection of roach was higher during summer (22·22%) but less than 5% in other seasons.     

Piscivory in larval perch (Perca fluviatilis): mechanisms structuring larval roach (Rutilus rutilus) cohorts

Abstract – Perch ( Perca fluviatilis ) can act as a piscivore from larval stage VI (body size 10.3 mm) on newly hatched larval roach ( Rutilus rutilus ), bream ( Abramis brama ) and smaller siblings of its own cohort. Consumption rates at this stage were approx. 0.5 prey/perch*h at 21°C. Larval perch predation was strongly gap-limited, and the maximum size of roach consumed by perch (perch length interval 10.3–62.0 mm) under experimental conditions followed the linear regression, P_prey-max.=0.478*L_Pred.+1.829 ( r ²=0.99, P <0.001, n =12). Under experimental conditions, predatory 0⁺ perch substantially affected the size distributions of 0⁺ roach prey cohorts, since smaller prey individuals were predated more frequently than larger ones. In both unimodal and bimodal size distributions of prey roach, the distributions changed according to the maximum prey size consumed by the added predatory perch. Unimodal prey distributions were positively skewed when piscivorous perch were added compared with controls without predators. According to the size distributions of lake-living 0⁺ roach and 0⁺ perch and the relative size difference between prey and predator, the vulnerability of 0⁺ roach cohort to 0⁺ perch predation changed from June to September. Prey vulnerability was extremely sensitive to the relative size difference between predator and prey. Therefore differences in hatching time and growth rates between the two species will strongly influence the potential for predator-prey interactions. ^Note     

Gill histopathological characteristics of Caspian roach (Rutilus rutilus caspicus) fingerlings treated with potassium permanganate and formalin

The aim of this study was to determine the gill histopathological characteristics of Caspian roach (Rutilus rutilus caspicus) fingerlings exposed to different concentrations of potassium permanganate (PM) and formalin (FO). The fish were exposed to different PM and FO concentrations over different periods: 1 ppm PM for 24 h (1‐P24), 2 ppm PM for 24 h (2‐P24), 5 ppm PM for 0.5 h (5‐P0.5), 10 ppm PM for 0.5 h (10‐P0.5), 10 ppm FO for 24 h (10‐F24), 20 ppm FO for 24 h (20‐F24), 40 ppm FO for 0.5 h (40‐F0.5) and 80 ppm FO for 0.5 h (80‐F0.5). After exposure, gill samples were collected for histological examination. The most frequent gill histopathological symptoms were hyperplasia and epithelial lifting. The order of the gill injury index (I_g.i) among the treatments was as follow: 1‐P24, 2‐P24 < 5‐P0.5, 40‐F0.5 < 10‐F24 < 10‐P0.5, 20‐F24, 80‐F0.5. Comparing the two agents, it is concluded that there is no significant difference in the gill damages between the agents during the short‐bath treatments. However, PM causes less pathological symptoms than FO during the long‐bath treatments. Comparing the bath durations, the agents showed different behaviours. PM‐treated fish showed significantly lower gill damage during the long‐bath compared to the short‐bath treatment; whereas, pathological symptoms of FO‐treated fish was dose‐dependent for each exposure period, separately. Overall, exposure of Caspian roach to PM, at the concentrations recommended for long bath, resulted in milder gill damages compared to FO.     

The Spawning of Roach Rutilus rutilus (L.) in a Chalk Stream

Roach spawned on two sites where Fontinalis antipyretica (Hedw.) grew thickly on vertical pilings. The eggs were distributed throughout the fronds of Fontinalis but were concentrated near the water surface. The fish spawned on those parts of the sites where the current adjacent to the weed was relatively fast. The sudden drop in water levels caused by weed cutting presents a potential threat to spawning success.     

布伦托海湖拟鲤的生物学研究

布伦托海位于新疆北部的福海县境内 ,为乌伦古河流域容浅区 ,总面积达 140多万亩。平均水深7～ 8米。湖周多戈壁、沙漠、气候干燥 ,蒸发量大于降水量的 15倍以上。昼夜与周年的温度交差均较大 ,夏季极端最高所温为 39 2℃ ( 1974年 ) ,冬季极端最低气温 - 4 1 2℃ ( 1972年 )冰封期长达四个半月至五个月。湖拟鲤 (Ｒｕｔｉｌｕｓｒｕｔｉｌｕｓｌａｃｕｓｔｒｉｓ (Ｐａｌｌａｓ)为中小型经济鱼类 ,在我国原仅分布于新疆北中额尔齐斯河流域。 1966年人工移植到布伦托海 ,1971年开凿了沟通布伦托海与额尔齐斯河的“引额济海渠道”后 ,湖拟鲤…     

The effects of dietary vitamin C on mucosal immune responses and growth performance in Caspian roach (Rutilus rutilus caspicus) fry

This study was conducted to investigate the effects of different levels of dietary vitamin C on some skin mucus immune parameters, mucus antimicrobial activity and growth performance of Caspian roach (Rutilus rutilus caspicus) fry. Six hundred sixty Caspian roach (1.4 ± 0.02 g) fry were allocated to 12 tanks (55 fish per tank), and triplicate groups were fed diets containing 0, 1,000, 1,500 and 2,000 mg kg^?1 vitamin C for 60 days. At the end of the trial, the epidermal mucus protein level, alkaline phosphatase and antimicrobial activity against two gram-positive bacteria (Streptococcus faecium and Micrococcus luteus) and gram-negative bacteria (Escherichia coli and Serratia marcescens) as well as growth performance were measured. The results demonstrated that feeding on vitamin C significantly elevated skin mucus alkaline phosphatase and protein levels compared to the control group (P < 0.05). However, lysozyme activity was undetectable in both the vitamin C-fed roach fry and the control group. Skin mucus antimicrobial activity was increased following vitamin C administration, and the bacterial growth inhibition zones were significantly elevated in vitamin C-fed roach (P < 0.05). Similar results were obtained in case of the minimum inhibitory concentration of skin mucus. Also fish fed the control diet had a significantly lower weight gain, specific growth rate and condition factor compared to the other treatments (P < 0.05). These results revealed that dietary vitamin C beneficially affects the skin mucus immune parameters and growth performance of Caspian roach fry.