首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 125 毫秒
1.
ABSTRACT:   A new myxosporean parasite was found in the body cavity and caudal peduncle of the freshwater goby Rhinogobius sp. Orange type (OR) collected from the Nagara River, Gifu Prefecture, Japan. Infected fish exhibited substantial swelling of the abdomen caused by large parasitic cysts approximately 10 mm in size, formed in the visceral cavity. The cyst was a compacted aggregate of several smaller cysts, similar to a bunch of grapes in appearance. Histological examination showed that plasmodia developed within the renal capsule, and finally occupied the visceral cavity. Spores were ovoid with an attenuated anterior end. Sutural ridges were conspicuous with several folds on the edge. Average spore size was 11.9 (10.5–13.5) μm long, 9.0 (8.0–10.0) μm wide, and 6.5 (6.0–7.0) μm thick. Two equal polar capsules were 5.5 (4.5–6 0) μm long and 3.0 (2.5–4.0) μm wide. Partial small subunit ribosomal DNA sequences of the myxosporean were distinct from those of other myxozoan species in GENBANK. A new species name, Myxobolus nagaraensis , is proposed for this parasite.  相似文献   

2.
Cardinal tetra, Paracheirodon axelrodi (Schultz, 1956), kept in an ornamental tank, was found to be affected by severe invasive mycosis. Externally, the disease manifested as abdominal swelling, and internally, the anterior part of the intestine was extremely bloated with abundant dematiaceous septate hyphae and an accumulation of fluid. Histopathologically, a granulomatous inflammatory response was observed in the intestine wall, kidney and spleen. We assume that the mycotic agent was primarily deposited in the intestine and was then gradually disseminated to the other organs. DNA sequencing of ITS and LSU rDNA regions and phenotypic characterization were used for identification of the isolated fungus. The obtained data confirmed that the infection was caused by Exophiala pisciphila. The disease was subsequently reproduced in the carp fingerling using intramuscular and intraperitoneal injection of a spore suspension. The 13th day after intramuscular infection, a marked elevation of neutrophils was recorded in the peripheral blood; this involved a proliferation of band forms and segmented forms. As far as we know, this is the first report of infection due to E. pisciphila in Cardinal tetra.  相似文献   

3.
Proliferative kidney disease (PKD) is caused by the infection of susceptible salmonid fish with spores of the myxozoan Tetracapsula bryosalmonae , a parasite harboured and released by several species of bryozoans. Under natural conditions, PKD is a water-borne infection of fish, whose outcome and spatio-temporal dissemination depend on the viability of spores present in the water. In order to evaluate the duration of parasite infectivity, juvenile rainbow trout, Oncorhynchus mykiss , were exposed for 20 h to T. bryosalmonae -infected water at various times post-water collection or after different filtration procedures. When infected water was held in a temperature range of 14.5–17 °C for up to 14 days, PKD was transmitted to the fish only between 0 and 12 h post-water collection and its infectivity vanished between 12 and 24 h. Similarly, the infectivity of water passed through 25 μm but not through 1 μm mesh filters, and was lost in the material eluted from the 1 μm filtration membrane although the parasite's DNA was amplified from this material. The parasitic infectivity in water appears to be fragile and this may offer opportunities to decrease the impact of PKD in trout farms by the implementation of management procedures aimed at reducing the number of the bryozoan-holding surfaces located in the river, immediately upstream from these farms.  相似文献   

4.
Abstract. Unicauda magna sp.n. (Protozoa: Myxozoa) was found in hatchery-raised fathead minnows, Pimephales promelas (Cyprinidae) from Pennsylvania. A large number of whitish-coloured cysts were located in the tissues of the pectoral, pelvic and caudal fins of infected fish. Spore dimensions (in μm) based on 30 measurements (10 spores/cyst) included the following: total length, 109.6 (75–170); spore body length, 15.5 (14–17); spore body thickness, 12.1 (10–13); spore body width, 13.2 (12–14.5); tail length, 94.1 (60–154); polar capsule lengths, 8.6 (7.5–9.5); polar capsule width 4.1 (3.0–5.0); sutural ridge width, about 1. The tail and body of the spores differed in colour when stained with each of three dyes. They are, therefore, composed of different material.  相似文献   

5.
ABSTRACT:   The feeding behavior and growth of post-larval Haliotis diversicolor with initial shell lengths (SL) of approximately 500 μm (Exp. 1-1 and 1-2), 800 μm (Exp. 2), and 1200 μm (Exp. 3) were studied in a laboratory setting while they fed on four species of benthic diatom Achnanthes longipes , Cocconeis sublittoralis , Cylindrotheca closterium , and Navicula ramosissima . Exp. 1-1 and 1-2 revealed no marked differences in post-larval growth rates (mean 24–39 μm SL/day) among the diatom species. However, marked differences in growth rates among the species were revealed in Exp. 2 and 3. Three species, A. longipes , Co. sublittoralis, and Cy. closterium , produced faster growth (Exp. 2 mean 29–51 μm/day, Exp. 3 mean 36–44 μm/day) than N. ramosissima (Exp. 2 mean 18 μm/day, Exp. 3 mean 23 μm/day). Post-larvae fed N. ramosissima had lower digestion efficiency (42.8%) than those fed other diatom species (90.7–100%). Diatom extracellular substances appeared to be principally used from post-settlement to 800 μm SL, and diatom cell contents were required to produce rapid growth of larger post-larvae (>800 μm SL). It is likely that the availability of each diatom for post-larvae was affected by diatom morphology, attachment strength, frustule strength, and post-larval size.  相似文献   

6.
Juvenile rainbow trout Oncorhynchus mykiss (Walbaum) were fed six low-phosphorus (P) diets supplemented with two different sizes of ground fish bone-meals (fine, 68 μm or less; coarse, 250–425 μm) and a coarse bone-meal diet containing four levels of citric acid (0, 4, 8 or 16 g kg−1 diet) to investigate the effects of pH and bone particle size on P bioavailability. The basal diet provided 3.4 g P   kg−1 and bone-meal increased P contents to 5.4–6.0 g P   kg−1. Coarse bone-meal diets supplemented with 0, 4, 8 or 16 g kg−1 of citric acid had pH values of 6.0, 5.7, 5.4 and 5.0, respectively. Weight gain and whole-body water, protein and lipid contents were not influenced by bone-meal supplementation. Supplementing the basal diet with both coarse and fine bone-meal significantly increased whole-body ash content. Fish fed no bone-meal were hypophosphataemic compared with fish fed with either fine or coarse bone-meals. Phosphorus in fine bone-meal had higher availability than P in coarse bone-meal. Bone-meal supplementation significantly decreased whole-body manganese content from 8.9 μg g−1 in fish fed no bone-meal to 2.3 and 4.5 μg g−1 in fish fed with fine and coarse bone-meals, respectively. The concentration of magnesium increased but zinc concentration was not affected by bone-meal supplements. Citric acid increased whole-body ash content but the influence of citric acid on the body P content was not significant ( P  = 0.07). Dietary acidification by citric acid significantly increased whole-body iron in a linear fashion. The bioavailability of dietary P can be improved by fine grinding the bone in fish meals.  相似文献   

7.
Abstract –  We measured growth of pike larvae ( Esox lucius ) fed with freshwater and brackish-water zooplankton by monitoring larval wet weight during 18 days. The fish food was analysed for species composition, carbon, nitrogen and fatty acids. Further, we analysed fish larval faecal pellet production. Larval weight was significantly higher in fresh water than in brackish water with natural zooplankton as food. Growth, given as wet weight, showed a significant relationship with zooplankton (>100  μ m) food carbon and highly unsaturated fatty acids, 20:5ω3, 22:6ω3, ω6 fatty acids and the ω3/ω6 fatty acid ratio. Phytoplankton fatty acids (10–50  μ m), such as polyunsaturated fatty acids, 20:5ω3, 22:6ω3 and the ω3 fatty acids also correlated strongly with the wet weight of pike larvae. We demonstrated that several factors impact on pike larval growth.  相似文献   

8.
ABSTRACT:   Toxic heavy metals such as cadmium (Cd) accumulate in cultured fish from solid-form feed mixtures. In this paper, two natural ingredients, supposed to inhibit accumulation of heavy metals in the fish body, were investigated to develop a functional feed mixture for healthy fish. Three test diets: (i) ♯1, regular diet as negative control; (ii) ♯2, ♯1 + 2% lyophilized Chinese parsley Coriandrum sativum (CP); and (iii) ♯3, ♯1 + 3% chitosan (CT), were each fed to 50 rainbow trout Oncorhynchus mykiss once a day, at the constant rate of 1.0–1.2% of body weight for 12 weeks. No undesirable effect on fish growth was observed by an addition of either CP or CT to regular feed. Then, 10 mg Cd was added to 1 kg each of the three test diets and they were named as: (i) ♯4, ♯1 + Cd; (ii) ♯5, ♯2 + Cd; and (iii) ♯6, ♯3 + Cd, respectively. The fish given positive a control feed (diet ♯4) for 3 weeks accumulated Cd in the liver and kidney at approximately 0.52 mg/kg. However, Cd in ordinary muscle was found to be just above the detection limit. Upon accumulation of Cd, three groups of 50 fish were each fed test diets ♯4, ♯5, and ♯6 for 12 weeks at the same feed rate described above. The concentrations of Cd accumulated in the liver, kidney, and ordinary muscle of the fish were measured every 3 weeks. Contrary to the positive control fish fed diet ♯4, those fish fed test diets ♯5 and ♯6 accumulated 20–30% and 25–40% less Cd in the liver, respectively. Test diets were a little less effective for inhibition of Cd uptake in the kidney than that observed in the liver. These results suggest that addition of CP or CT to fish feed might be used to decrease toxic heavy metal accumulation in fish.  相似文献   

9.
ABSTRACT:   The bluefin tuna tested were reared for 22 months from eggs before the beginning of the experiment, and sampling was performed every 3 months over the following year. The experimental results showed that the mercury concentration in the muscle ranged from 0.32 to 0.85 μg/g, which is lower than that found in wild bluefin tuna of a similar size. Increase in the mercury concentration corresponding to the increase in body weight was not shown, and it was quite different with wild bluefin tuna. Furthermore, no significant relationship was found between the lipid concentration and the mercury concentration in muscle. Among the internal organs of cultured bluefin tuna, the heart (0.32–0.66 μg/g), liver (0.43–0.99 μg/g) and spleen (0.59–1.0 μg/g) contained higher concentrations of mercury. It was estimated that the full-cycle cultured bluefin tuna had been fed small fish containing lower concentrations of mercury, and that the mercury concentration of tuna would be almost equal throughout the year because the effect of mercury accumulation would be weakened by body growth. Therefore, it was concluded that selecting diet fish species might decrease mercury contents in cultured bluefin tuna.  相似文献   

10.
ABSTRACT:   Body size dependent distribution patterns of bighand thornyhead Sebastolobus macrochir were examined using bottom trawl surveys in the Tohoku area, off the Pacific coast of northern Honshu, Japan. In northern and southern Tohoku, distribution depths of ≤10-cm standard length (SL) fish increased from 500–600 m in 2003 to 600–700 m in 2005 with an increase in density of 11–20-cm SL fish at depths of 500–600 m. In 2004–2005, small fish (≤10 cm SL) were distributed in deeper waters than large fish (11–20 cm SL). In ≤20-cm SL fish, the main distribution depths changed from 300–600 m in 1997–2002 to 500–600 m in 2003 in southern Tohoku, but not in northern Tohoku. Stepwise multiple regression analysis showed that negative correlations were found in biomass densities between a few demersal fish species and bighand thornyhead at depths of 300–400 and 400–500 m in southern Tohoku. These results suggest that distribution of bighand thornyhead was affected by intra- and interspecific competitions in the Tohoku area.  相似文献   

11.
An annual disease problem with high levels of mortality in Atlantic salmon, Salmo salar L., on a freshwater farm was investigated. In 2000, mortalities began early in October and peaked in December, being unevenly distributed between tanks. Histopathological changes included severe hyperplasia of gill epithelium, with fusion of secondary lamellae, and extensive necrosis of the haematopoietic centres in the kidney and spleen, the latter being consistent with a diagnosis of phagocytolytic syndrome (PCLS). Moribund fish were anaemic, with multiple, circular basophilic inclusion bodies, 1–2 μm in diameter and suggestive of erythrocytic inclusion body syndrome (EIBS), being observed on blood smears. Thin section electron microscopy (EM) revealed primarily membrane-bound aggregates of non-enveloped virus particles (73 ± 7 nm) with an electron dense core (35 ± 3 nm) in spleen, kidney and gill tissue and the erythrocytes therein. These particles had morphology and distribution consistent with those previously described separately for both EIBS and PCLS. Virus isolation attempts in a wide range of cell lines were unsuccessful. In the absence of suitable alternative infectious or environmental explanations, it is postulated that the aetiology was primarily viral, with possible contributory secondary environmental factors. It is further hypothesized that the agents of EIBS and PCLS may be the same or closely related viruses.  相似文献   

12.
Weirs and traps were used to monitor the movement of two strains of stocked brown trout, Salmo trutta L. Within 24 h of stocking, 15% ( n  = 13) of a Danish strain and 21% ( n  = 19) of a hybrid strain moved at least 100 m from their release site. In the following 5–6 days, no further movement was found for Danish fish, but hybrid fish continued to move, totaling 32% ( n  = 29) of the fish stocked. During this same period, 36 wild brown trout (≈ 3.5% of the population) were captured, moving over the weirs. Two weeks later, and one week after a flood, 70% ( n  = 59) of the Danish strain were recovered within their release sites and 89% ( n  = 76) were recovered during an electric fishing survey within the 3.5-km-long experimental area. In contrast, 43% ( n  = 31) of the hybrid strain were recaptured in their release sites and 49% ( n  = 45) within the experimental area. The total recapture of wild adult fish was only 16% ( n  = 41). The flooding event was insignificant in comparison with strain-specific behaviours in determining patterns of movement and residency.Austria, brown trout, floods, movement, stocking.  相似文献   

13.
Abstract –  To address the dearth of information on tagging effects and long-term survivorship of tagged fish in native and introduced species, laboratory and field investigations were undertaken on three non-native fish species (pumpkinseed Lepomis gibbosus ; topmouth gudgeon Pseudorasbora parva ; pikeperch Sander lucioperca ) tagged with coded-wire (CW), passive integrated transponder (PIT), radio (RT) telemetry and/or acoustic tags (AT), with survivorship of native brown trout ( Salmo trutta ) examined in the field. Laboratory results revealed high survivorship following tag attachment/insertion and resumption of feeding within 24–48 h of tagging (all mortalities could be attributed to an unrelated outbreak of fungal infection), with retention rates being high in both pumpkinseed and pikeperch but low in topmouth gudgeon (excluded from field studies). In the field, short-term post-operation survival was high in pikeperch, pumpkinseed and brown trout. In pumpkinseed and trout, 100% of RT fish survived a 24–30 day tracking study, with 60% and 80%, respectively, recaptured alive at least 3 months post-tagging. Of PIT tagged pumpkinseed, 44% were recaptured (after 6–18 months), with small-sized, CW-tagged fish (0.38 g weight) captured up to 1 year after tagging. In pikeperch, all AT fish except one (the smallest specimen) survived their full expected tracking period (i.e. tag life) – the single lost specimen survived at least half of its expected tracking period (i.e. 6 month battery life). Overall, the tagging methods used were highly effective in pumpkinseed and pikeperch, showing good retention and survival, but PIT tagging of topmouth gudgeon was plagued by low survivorship and tag rejection.  相似文献   

14.
The aim of this study was to evaluate the dynamics of the blood plasma parameters and the content of microcystins in the tissues of common carp ( Cyprinus carpio L.) in relation to the toxic cyanobacterial water bloom. Fish (average body mass 2176±697 g) in the hypertrophic pond were exposed to natural water bloom (dominated by Planktothrix agardhii, Pseudanabaena limnetica and Limnothrix redekei ), which contained microcystins (concentration in biomass 20–181 μg g−1 dry wt, concentration in water 0.3–9.5 μg L−1). Biochemical parameters in fish blood plasma were analysed in 89 fish at 14-day intervals during the whole season (nine sampling periods). Our results demonstrated high variability and fluctuations in the investigated parameters. The content of microcystins and density of cyanobacterial cells correlated with some haematological indices as lipase, alanine–aminotransferase, albumin, magnesium and chlorides. The concentrations of microcystins in the muscle and liver of the fish (determined by high-performance liquid chromatography with mass spectrometer) were below the limit of detection during the monitored period [0.31 ng g−1 fresh weight (f.w.) for the liver and 0.13 ng g−1 f.w. for muscle]. Our study demonstrates that although known cyanobacterial toxin microcystins were not detected in the fish tissues, several biochemical parameters important for the fish physiology were modulated by natural cyanobacterial bloom.  相似文献   

15.
Abstract –  A total of 40 (20 age-3 + 20 age-4) radio-tagged hatchery-reared brown trout ( Salmo trutta L.) and 40 wild radio-tagged northern pike ( Esox lucius L.) were released into a regulated river. Age-3 brown trout were predicted and observed to be highly vulnerable to predation by pike (50% mortality), whereas age-4 brown trout were predicted and observed to enjoy an almost absolute size refuge from predation (5% mortality). Almost half of the fish from both age groups similarly emigrated and survived from the river within 3 days of the release. However, there was a considerable difference in survival between age groups for fish that remained in the river for a longer period. Of these, all except one age-3 brown trout were eaten by pike, whereas all but one age-4 fish survived predation.  相似文献   

16.
Necropsy examination of an adult Atlantic salmon (Salmo salar) from the Dalälven River in Sweden revealed numerous large, white nodules, with spherical cysts and granulomata in kidney and liver. Histopathology showed dark, septate, thin‐walled hyphae. The aetiologic agent was found to be an Ochroconis species (Venturiales) that differed from known fish‐associated species of the genus. Molecular phylogenetic studies of the culture (strain UIII09 = CBS 135766) demonstrated that Ochroconis globalis was concerned. The isolate proved to be susceptible to all investigated antifungals, as it is known for another Ochroconis species. The role of Ochroconis in opportunism of cold‐blooded animals was discussed, and the diagnostic methods using DNA sequences for routine identification of the fungus were proposed.  相似文献   

17.
The sessile suspension feeding ascidian, Styela clava , plays an important role in the functioning of estuarine systems. The feeding selectivity of S. clava was examined using standard physiological techniques in terms of particle sizes and diet concentrations. Styela clava increased its retention efficiency (the proportion of available particles retained in ascidian) with increasing particle size at a lower diet concentration [expressed as particulate organic matter (POM)] from 2.11 to 10.06 mg POM L−1, and the highest retention was reached for 5–20 μm particles. With increasing diet concentration to 20.12 mg POM L−1, S. clava retained small particles (<3.5 μm) more efficiently and large ones (>15 μm) less efficiently. The selectivity of ascidian with different sizes was similar at the same concentration. At every diet concentration, larger ascidians retained more 5–20 μm cells than the smaller ones. All these results indicate that S. clava possesses a particle selection mechanism that may affect the zooplankton communities to a certain degree.  相似文献   

18.
ABSTRACT:   The effects of silvering state of wild female Japanese eels Anguilla japonica on the success of induced maturation and the following spawning were examined. Thirty-eight females, collected in Mikawa Bay, were divided into four stages based on their silvering state: yellow (Y1), late-yellow (Y2), silver (S1) and late silver eels (S2). Despite injections of salmon pituitary extract (SPE) through the standard technique, Y1 and Y2 eels did not respond to the treatment with undeveloped gonad (gonad-somatic index [GSI]: 0.3–0.9), and all these females died by 5 weeks, probably due to an abnormal physiological condition. Most S1 (81%) and S2 eels (100%) matured completely (GSI: 17.8–51.4), and finally spawned successfully (69% for S1, 89% for S2). S2 eels fully matured with oocytes of over 750 μm in diameter by significantly smaller number of injections of SPE (5–6 times) than the case of S1 eels (6–8 times). The amount of eggs released by S2 eels (0.65 ± 0.11 g/fish per body weight [BW]) was significantly larger than those by S1 eels (0.54 ± 0.09 g/fish per BW). There was no difference in fertilization and hatching rates between eggs released by S1 eels and those of S2 eels. These results indicate that the success of induced maturation and spawning in wild female Japanese eels depends on their silvering state, and matured eggs can be obtained efficiently through the use of S2 eels rather than other stages.  相似文献   

19.
Abstract– Habitat use and population dynamics in brown trout Salmo trutta and Arctic charr Salvelinus alpinus were studied in an oligotrophic lake over a period of 10 years. Previous studies showed that the species segregated by habitat during summer. While brown trout occupied the surface water down to a depth of 10 m, Arctic charr were found deeper with a maximum occurrence at depth 10–15 m. Following the removal of a large number of intermediate sized fish in 1988–89, habitat segregation between the species broke down and Arctic charr were found in upper waters, while brown trout descended to deeper waters. The following year, both species were most frequently found in surface waters at depths of 0–5 m. During the last four years, the species reestablished their original habitat segregation despite another removal experiment of intermediate-sized fish in 1992–1994. The removal of fish resulted in an increased proportion of large (≥ 25 cm) fish in both species. Furthermore, the charr stock responded by reduced abundance and increased size-at-age. The results revealed plasticity and strong resistance to harvest populations of brown trout and Arctic charr. This is probably due to internal mechanisms of intraspecific competition within each population, which result in differential mortality among size classes.  相似文献   

20.
Abstract  – Movements of adult Atlantic salmon were tracked through a series of four fish passes and an impoundment on the River Conon system, Northern Scotland. Proportions of fish passing individual obstructions ranged from 63 to 100%. The cumulative effect was that only 4 of the 54 tagged fish reached the spawning areas. The fish were delayed for 1–41 days at a pool-and-overfall ladder and 1–52 days at a Borland fish lift. The fish swam through a 10 km long reservoir at 0.21–1.16 km·h−1. A total of 13 fish negotiated a 2.5 km long, 3 m diameter diversion tunnel through a mountain to their home river. High levels of electromyogram (EMG) activity were recorded during ascent of a pool-and-overfall fish ladder, indicating that high energy demanding burst swimming was required.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号