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1.
Abstract. Ultrastructural analysis of epitheliocystis organisms from gills of anadromous juvenile steelhead trout, Salmo gairdneri Richardson, revealed the presence of several distinct forms. Two oval infectious organisms resembled previously described agents and had chlamydia-like characteristics. One form had a distinct oval head region from which a tail-like structure projected. These prokaryotic forms have an ultrastructural appearance which has not been described in previous reports of epitheliocystis. Morphological analyses of gill epithelial cells of S. gairdneri suggest that each cyst remains contained within the cytoplasm of a single host cell.  相似文献   

2.
Abstract. Epitheliocystis infections in the gills of carp from Israel and Portugal occurred in lining epithelial cells as well as mucus and chloride cells. Ultrastructural studies of infected cells revealed several morphological forms of epitheliocystis showing the existence of a pleomorphic developmental cycle. The following stages were observed: chlamydia-like round cells (RC), non-dividing round cells (NRC) and bullet-shaped small cells (SC). All these were identical in shape to RC and SC described from epitheliocystis of other fish, The rickettsia-like cells (PLC and ILC) which occur in epitheliocystis from other fish species and produce the SC were absent in carp epitheliocystis and instead the RC were seen transforming into SC. Transformation to SC, however, occurred at any stage of the developmental process, even before the replication potential of the RC was exhausted, i.e. before reaching the NRC stage.  相似文献   

3.
Abstract. Ultrastructural study of epitheliocystis organisms from gills of Sparus aurata (L.) and Liza ramada (Risso) revealed in each fish a new form of the organism which differed from epitheliocystis organisms previously described. In their size range, the presence of a plasma membrane, a trilaminated cell wall and a central nucleoid, these organisms resembled chlamydial organisms (PLT). However they differed from them in the following respects: in both species several morphological forms were recognized; hyphae or mycelium-like forms and individual units, not comparable to any of the successive units described for Chlamydia organisms. Both organisms were contained within an inclusion in the host cell, but in epitlieliocysts from S. aM7-ata apparently intracytoplasmic forms were also observed. Ultrastructural studies of the cytoplasmic wall of the epitheliocystis inclusion in S. aurata suggest that the epitheliocystis cyst remains contained in a single unruptured hypertrophied cell, while in i. ramada the final cyst is formed through the coalescence of several epithelial cells.  相似文献   

4.
Epitheliocystis is a condition affecting the gills and skin of fish, which has been reported from more than 50 freshwater and marine species. It is caused by intracellular Gram-negative bacteria. Mortalities have been associated with epitheliocystis infections in cultured fish. This review provides an update of our current understanding of this condition, including characterization of the pathogen using immunohistochemical and molecular studies. In most fish species the epitheliocystis agent was negative to an antibody specific for chlamydial genus-specific lipopolysaccharide antigen. Recently, four epitheliocystis agents from four different fish species have been characterized using molecular analysis. While they all belong to the order Chlamydiales, in a lineage separate from the Chlamydiaceae, they are distinct organisms and similarity analysis showed that they had highest similarity values with other chlamydia-like bacteria isolated from various sources, including humans or pig. This confirms the high diversity and host specificity of the pathogen. Further molecular analysis should result in an increased understanding of this condition. To date the pathogen has not been cultured, making experimental studies difficult. High stocking densities, presence of nutrients, season, temperature and fish age have been identified as potential risk factors for the manifestation of this condition.  相似文献   

5.
Abstract. Stages of development of chlamydial organisms were found in intracellular 'cysts' in the epithelium of the gill lamellae of brown bullheads. Early, irregularly shaped stages with granular cytoplasm occurred in membrane-bound vacuotes in host cells of undetermined origin. The organisms enlarged and divided within the grossly hypertrophied host cell. Dense nucleoids were first seen in single, closely packed organisms, which became enlarged and irregular in shape. Small, spherical organisms were formed from larger ones by fission and budding. Mature cysts contained many small, dense, spherical forms, each of which contained a dense central nucleoid. Fine filaments arranged perpendicular to the plasma membrane traversed the space between the inner and outer membranes of the dense spherical forms, which appeared to be the terminal stage of development. The ultrastructural features of the chlamydial agent of epitheliocystis are compared with those in other fish and with chlamydiae in higher vertebrates.  相似文献   

6.
2015年,山东省某养殖场工厂化养殖的斑石鲷(Oplegnathus puncatus)幼鱼(全长为15 cm左右)因病陆续死亡,15d内累积死亡率达40％以上.现场调查发现,发病池水温为21℃,盐度为30.患病鱼群散开、不聚集.病鱼身体侧偏,活力差,常贴底或者贴壁,严重者随着水流漂流.病鱼呼吸困难,口部持续张开,鳃盖开合频繁,对投喂的食物无反应.但病鱼反应灵敏,难以捕捉.临床检查和剖检可见病鱼鳃表面覆盖着大量黏液,鳃丝有损伤,肠道无食物.取病鱼鳃丝制成水浸片,在光学显微镜下观察,鳃丝上可见到许多直径约为30-70 μm的囊肿物,外观圆形或卵圆形,呈浅黄棕色.在苏木精-伊红染色的石蜡切片中,病鱼次级鳃丝末端粘连,许多上皮细胞膨大呈囊肿状.囊肿嗜碱性,内部均质化.在扫描电子显微镜下观察,病鱼鳃丝呈棍棒化,鳃小片被大量黏液覆盖,表面光滑的囊肿细胞镶嵌其间.通过上述疾病现场调查、病鱼的临床检查、鳃组织的光学显微镜和扫描电子显微镜病理观察,可以初步确定该病为斑石鲷上皮囊肿病.这是上皮囊肿病在中国养殖斑石鲷中首次被发现和记载.  相似文献   

7.
Epitheliocystis infection affecting the gill and the pseudobranch of the cultured amberjack, Seriola dumerili Risso, is described. In hyperinfected fish, proliferative cell response around the epitheliocystis capsule resulted in gill and pseudobranch lamellar fusion, which led to mass mortalities in the 0+age class. Histopathological and scanning electron microscope observations showed that the target cell was the chloride cell since (1) epitheliocystis organisms were first found within the chloride cell; (2) chloride cells underwent degeneration in the filament epithelium, proliferated along the lamellae, and hypertrophied; and (3) cysts were found only in the trailing edge of the gill filament and in the interlamellar spaces where, in healthy fish, chloride cells are mainly located. In some cases, the pseudobranch of infected fish was much more severely affected than the gill. It is therefore suggested that, for diagnostic purposes, the pseudobranch should also be sampled when epitheliocystis disease is suspected.  相似文献   

8.
Epitheliocystis in Swiss brown trout (Salmo trutta) is a chlamydial infection, mainly caused by Candidatus Piscichlamydia salmonis and Candidatus Clavichlamydia salmonicola. To gain a better understanding of the temporal development of infections in wild brown trout, we investigated epitheliocystis infections during the course of the summer and autumn months of a single year (2015), and compared this to sampling points over the span of the years 2012–2014. The survey focused on tributaries (Venoge and Boiron) of the Rhone flowing in to Lake Geneva. When evaluated histologically, epitheliocystis infections were found throughout the period of investigation with the exception of the month of June. Fifty to 86 animals per sampling were investigated. Highest prevalence and infection intensities were seen in September. A correlation between epitheliocystis infection and water temperatures was not evident. Interyear comparison revealed consistent levels of prevalence and infection intensities in late summer. The absence of infections in June, combined with the consistent interyear results, indicates seasonal fluctuation of epitheliocystis infections in brown trout with a reservoir persisting during winter months from which infections can re‐initiate each year. This could either be at levels below detection limits within the brown trout population itself or in an alternative host.  相似文献   

9.
An intracellular bacterium was detected on several occasions in commercial farms in Ecuador culturing red claw crayfish, Cherax quadricarinatus (Von Martens). Cases A, B and C presented mortality rates of 80%, 45% and 80%, respectively. Each incident occurred in grow-out ponds. Moribund crayfish were observed at the edge of the ponds in some cases. Affected crayfish presented no external differences from healthy ones, except their smaller size. Histological examination of affected red claw crayfish revealed that the cytoplasm of cells in the hepatopancreas, cuticular epithelium, and connective tissue of all organs had been replaced by massive granular and basophilic material. In the hepatopancreas, the tubules were intact but the intertubular connective tissue was replaced by Gram-negative microcolonies. Columnar cells in the cuticular epithelium also contained Gram-negative microcolonies and were necrotic. The heart and nerve cords also contained basophilic material. Transmission electron microscopy showed that the microcolonies consisted of a rod-shaped, obligately intracellular bacterium. The bacterium was delimited by a cell membrane that was composed of two electron-dense zones. Cells contained a single, compact, cytoplasmic condensation that was circumscribed by an electron-lucent halo. The bacterium replicated within the cytoplasm of host cells, which is pathognomic of rickettsiales infections. No host cell nuclei were infected.  相似文献   

10.
Abstract. The existence of a pleomorphic development cycle is demonstrated in epitheliocystis organisms obtained from fish of the following families: Sparidae, Sparus aurata L.; Mugilidae, Liza ramada (Risso), Liza aurata (Risso) and Mugil cephalus L.; Cichlidae, Tilapia mossambica (Peters) and Tilapia aurea × nilotica; and Serranidae, Dicentrarchus labrax L. Ultrastructure of the successive developmental stages, primary long cells, intermediate long cells and small cells are described as well as the division process between stages. An additional stage, the round cell, was found in infected chloride cells. The affinities between epitheliocystis organisms and known chlamydial organisms of vertebrates and invertebrates are discussed.  相似文献   

11.
Histopathological and ultrastructural investigations were conducted on 36 tench, Tinca tinca (L.), from Lake Trasimeno (Italy). The gills, intestine, liver, spleen, kidney and heart of 21 individuals were found to harbour an extensive infection of larvae of an unidentified digenean trematode. The eyes, gonads, swim bladder and muscles were uninfected. The parasites in each tissue type were embedded in a granulomatous proliferation of tissue, forming a reactive fibroconnective capsule around each larva. Most of the encysted larvae were metacercariae, in a degenerative state, but on occasion some cercariae were found. Many of the granulomas were either necrotic or had a calcified core. Within the granuloma of each, the occurrence of granulocytes, macrophages, rodlet cells and pigment‐bearing macrophage aggregates was observed. Hearts bore the highest parasitic infection. Whilst the presence of metacercariae within the intestine was found positioned between the submucosa and muscle layers, metacercariae in the liver were commonly found encysted on its surface where the hepatocytes in close contact with the granuloma were observed to have electron‐lucent vesicles within their cytoplasm. Metacercariae encysting adjacent to the cartilaginous rods of gill filaments were seen to elicit a proliferation of the cartilage from the perichondrium. Rodlet cells, neutrophils and mast cells were frequently observed in close proximity to, and within, infected gill capillaries. Given the degenerated state of most granulomas, a morphology‐based identification of the enclosed digeneans was not possible.  相似文献   

12.
Chlamydial infections are recognised as causative agent of epitheliocystis, reported from over 90 fish species. In the present study, the farmed striped catfish Pangasianodon hypophthalmus (14–15 cm, 70–90 g) with a history of cumulative mortality of about 23% during June and July 2015, were brought to the laboratory. The histopathological examination of gills from the affected fish revealed presence of granular basophilic intracellular inclusions, mostly at the base of the interlamellar region and in gill filaments. A concurrent infection with Trichodina spp., Ichthyobodo spp. and Dactylogyrus spp. was observed in the gills. The presence of chlamydial DNA in the gills of affected fish was confirmed by amplification and sequencing of 16S rRNA gene. BLAST‐n analysis of these amplicons revealed maximum similarity (96%) with Candidatus Actinochlamydia clariae. On the basis of phylogenetic analysis, it was inferred that the epitheliocystis agents from striped catfish were novel and belonged to the taxon Ca. Actinochlamydia. It is proposed that epitheliocystis agents from striped catfish will be named as Ca. Actinochlamydia pangasiae. The 16S rRNA gene amplicons from novel chlamydiae were labelled and linked to inclusions by in situ hybridisation. This is the first report of epitheliocystis from India in a new fish host P. hypophthalmus.  相似文献   

13.
安氏新银鱼的矢耳石呈不规则卵圆形。60尾样品(体长37~52 mm)耳石长半径y与体长x呈线形关系,y=260.335+2.6234x。光镜下观察了耳石制片的显微结构。耳石中心圆形的核平均直径(25.17±2.40)μm(SD,后同)。核中心原基平均直径(7.80±2.22)μm。核周围为同心环纹,即日轮。耳石上日轮数73~101,78.3%的样品分布于83~97日轮范围内。前10个日轮平均间距最窄,为1.76μm,之后日轮间距逐渐增宽,60~70日轮平均间距最宽(2.70μm),而后日轮间距又变窄。依日轮间距推算的体长生长,前10日龄平均日增长0.34 mm,以后生长加快,60~70日龄平均日增长最快,为0.52 mm。依据采样日期,日轮数和胚胎发育期推断,样品鱼的产卵期为4月中旬至5月中旬,出生日期为4月下旬至5月下旬。从最初2~3个日轮间距最宽,4~10日轮间距较窄判断,其卵黄营养期为3~4 d,混合营养期为6~7 d。部分样品在48~72日轮处有过渡轮,应是由近海(盐度27~30)到河口(盐度6~18)盐度急剧变化诱导形成的,表明幼鱼有到河口摄食洄游的习性。  相似文献   

14.
Oxynticopeptic cells (OC) from rainbow trout, Oncorhynchus mykiss, and Atlantic cod, Gadus morhua, were studied during basal acid secretion and during stimulation with histamine. An in vitro method for measuring acid secretion from isolated stomac a was used. The OC ultrastructure was studied using electron microscopy. During basal acid secretion, the OC had short apical microvilli, an extensive tubulovesicular network, large electron-dense vesicles and many mitochondria. Stimulation of acid s tion with histamine and ultrastructural changes in the OC occurred simultaneously. The acid stimulation promoted large increases in the length of microvilli, a decrease in the size of the tubulovesicular network and an increase in the diameter of the ndular lumen in cod. Large vacuoles were found to characterize the histamine-stimulated OC. These were located close to the apical membrane and sometimes opened into the lumen. During stimulation, electron-dense vesicles were often observed close to apical membrane and the large vacuoles. Sometimes these vesicles were observed inside the glandular lumen and/or the large vacuoles. It is concluded that the ultrastructure of the OC in the saltwater cod and the freshwater trout show similar characte ics as OC in other animal groups both during basal and high rates of acid secretion. In addition, vacuoles were found in both species OC during basal rates of acid secretion and they significantly increased in size during high rates of acid secretion propose that the OC vacuole have a part in the osmoregulation, since the increase was tenfold in cod but less then one-fold in trout, this difference was statistically significant.  相似文献   

15.
Abstract. Kudoa paniformis and Kudoa thyrsites infect the muscle of Pacific whiting, Merluccius productus , and K. paniformis is known to cause a softened muscle texture after death of the fish. Ultrastructural studies were conducted on the host-parasite interaction between Pacific whiting and these myxosporeans at two stages of their infection: (1) unencapsulated plasmodia that contained mature and developing spores, and (2) encapsulated plasmodia that contained deteriorating spores. Unencapsulated plasmodia of both species had a microvillar border that was closely associated with the host muscle. Species-specific characteristics included the presence of multi-vesicular bodies in plasmodia of K. paniformis whereas the cytoplasm of K. thyrsites plasmodia contained an array of vesicles, microfilaments and microtubules. Differences in the predominant organelles of the plasmodia may be related to the production of different proteolytic enzymes by each species. A host response became apparent only after a plasmodium had replaced the width of an infected muscle fibre. At that time, the plasmodia of both species became encapsulated by a wall of fibroblast-like cells that were connected by numerous desmosomes. Occasional phagocytes were located at the edge of these capsules. Ultrastructural evidence suggests that the encapsulated plasmodia were not proteolytically active. Melanin deposition did not occur. However, encapsulated plasmodia with deteriorating spores contained electron-dense breakdown products.  相似文献   

16.
3种珍珠贝的外套膜小片外表皮细胞的超微结构   总被引：1，自引：0，他引：1  
用透射电子显微镜对合浦珠母贝（Ｐｉｎｃｔａｄａｆｕｃａｔａ）、大珠母贝（Ｐｉｎｃｔａｄａｍａｘｉｍａ）和企鹅珍珠贝（Ｐｔｅｒｉａｐｅｎｇｕｉｎ）的外套膜小片外表皮超微结构进行比较观察,发现都是单层柱状表皮,由３类细胞构成,即柱状表皮细胞、粘液细胞和嗜酸性粒分泌细胞。柱状表皮细胞是贝壳和珍珠组份的主要合成和转运者,据其结构和功能的差异可细分为Ａ、Ｂ、Ｃ３型。粘液细胞和嗜酸性粒分泌细胞呈杯状或不规则,体积巨大,细胞质稀少,核的形态亦不固定,前者的胞体全由电子透明泡占据,后者含有大量嗜酸性的电子稠密颗粒。这２类细胞的主要功能是参与物质转运,它们在邻近表皮的结缔组织中也有分布,可作变形运动穿越基膜进入上皮层。  相似文献   

17.
Heavy infection with epitheliocystis on gills caused mortality in hatchery-born Sparus aurata. Histopathological findings showed extensive proliferation of the gill epithelium around the epitheliocystis capsule. Such proliferation was not observed in benign infections. Epizootic infections thus occurred only in hatchery-born S. aurata. In S. aurata and mullets reared from natural stocks, infection remained benign and sporadic. Epitheliocystis infections were also found in juvenile mullets from the east Mediterranean waters as well as from the Gulf of Elat, Red Sea.  相似文献   

18.
Differences in eel, Anguilla anguilla (L.), head shape were the result of greater increases in head width, rather than changes in head length. The ratio of head width:total length (HW:TL) increased significantly ( t -test, P < 0.05) from the glass-yellow eel stage. Cultured yellow eels were exclusively narrow headed (mean HW:TL = 0.027, range = 0.023–0.032), while wild yellow eels displayed an array of head shapes (mean HW:TL = 0.033, range = 0.023–0.046). Therefore, broad heads (HW:TL 0.033) occurred only among wild yellow eels sampled and may have resulted from diet. Cultured yellow eels consumed only small pellet material. Of wild yellow eels stomachs containing food, 78% of broad-headed eels consumed large and/or hard-bodied organisms (e.g. beetles, fish, molluscs and Notonecta sp.), while 83% of narrow-headed eels consumed exclusively small/soft-bodied prey (e.g. amphipods and chironomids).  相似文献   

19.
Lake trout Salvelinus namaycush (Walbaum) raised for stocking experienced yearly (2011–13) winter epizootics of epitheliocystis. Affected fish were dispersed on the bottom of the tank, had decreased feed and fright response, and mortality often reached 40%. Peak mortality occurred within 3 weeks of the appearance of clinical signs, and outbreaks typically lasted 6 weeks. Affected fish had no gross lesions but histologically had branchial epithelial necrosis and lamellar hyperplasia, with small to large numbers of scattered epithelial cells containing 10‐ to 20‐μm inclusions. A longitudinal study was undertaken of one annual outbreak, and lamellar hyperplasia was most closely associated with mortality. The number of inclusions was statistically greater (P < 0.05) before and during peak mortality, but inclusions were present in low numbers before clinical signs occurred. Results of histochemical staining, immunohistochemistry and transmission electron microscopy supported the presence of a β‐proteobacteria rather than a Chlamydiales bacterium within inclusions. PCR primers to identify Chlamydiales did not give consistent results. However, the use of universal 16S rDNA bacterial primers in conjunction with laser capture microdissection of inclusions demonstrated that a β‐proteobacteria was consistently associated with affected gills and is more likely the cause of the disease in lake trout.  相似文献   

20.
Two new species of myxozoans from the Japanese anglerfish, Lophius litulon, are described using myxospore morphology and small subunit rDNA sequences. Ceratomyxa anko sp. n. is a parasite of the gall bladder and had a prevalence of 57%. Mature spores of C. anko sp. n. are arcuate to crescent shaped with valves tapering to rounded tips. A prominent sutural line runs centrally between the round adjacent polar capsules containing the polar filament coiled two to three times. Spore measurements: length 10.8 (9.7-11.9) microm, width 41.9 (36.9-47.2) microm, polar capsule diameter 4.6 (4.1-5.3) microm. Ceratomyxa anko sp. n. can be distinguished from other Ceratomyxa spp. due to its spore dimensions and shape. Zschokkella lophii sp. n. is a parasite of the urinary bladder and had a prevalence of 70%. Mature spores are ellipsoidal to semicircular with bluntly pointed ends. The sutural line is curved or sinuous and the valves have no discernable surface ornamentation. Two almost spherical polar capsules are located separately in the ends of the spore, opening in almost opposite directions and contain the polar filament with five coils. Spore measurements: length 20.1 (16.8-24.0) microm, width 14.9 (12.7-16.8) microm, polar capsule diameter 5.1 (3.6-5.8) microm. Zschokkella lophii sp. n. can be distinguished from other Zschokkella spp. due to the terminal opening of the polar capsules within the spores and the site of infection within the host fish. In the phylogenetic analyses, C. anko sp. n. grouped with other members of the same genus forming a monophyly. Zschokkella lophii sp. n. forms a discrete clade with another Zschokkella sp. that infects the urinary bladder of marine fish. This grouping forms a sister clade to one containing members of the genus Parvicapsula, all of which are parasites of the urinary system in marine fish.  相似文献   

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