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 484 毫秒
1.
Abstract

The biflagellated, single-celled parasite Ichthyobodo necator can cause significant losses among fish populations, particularly those cultured in tanks. Treatments of KMnO4 and CuSO4 were evaluated against a naturally occurring I. necator infestation on sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis) raised in tanks. Four-hour static treatments with 3 mg of KMnO4/L of water (2.5 mg/L above the determined KMnO4 demand) or 2 mg of CuSO4/L of water (total alkalinity = 207 mg/L; total hardness = 95 mg/L) were randomly applied to 4 tanks/treatment (23 fish/tank); the same treatments were reapplied 2 d later. Four tanks were used as positive controls. By 2 d posttreatment (after the second treatment), only 17.4% of the untreated control fish survived, and a sample of the remaining fish was heavily infested with I. necator. All remaining control fish were dead by 5 d posttreatment. The KMnO4 treatment significantly curtailed the initial mortality (survival = 92.4%) and slightly reduced the high parasite loads at 2 d posttreatment. However, fish mortalities increased dramatically over the next 3 d (survival at 5 d posttreatment = 37.5%), and parasite loads from sampled fish remained high. The CuSO4 treatment was effective in significantly lowering the parasite load (almost eliminating I. necator) and maintaining a high fish survival (87.5%) by 5 d posttreatment. The findings in this study clearly demonstrate that CuSO4 is a viable treatment for ichthyobodosis in tanks.  相似文献   

2.
Abstract

In the spring of 1998, the Florida Fish and Wildlife Research Institute received numerous reports of lesioned or ulcerated fish primarily from the St. Lucie Estuary on the southeast coast of Florida, an area known since the late 1970s for lesions of the ulcerative mycosis (UM) type. From these and archived reports, as well as others received from different areas of Florida, we documented that diseased specimens had randomly distributed skin ulcers (usually reddened or hemorrhagic) with raised irregular margins and, in some cases, deeply penetrating hyphae in the surrounding muscle tissue. Since 1998, 256 fish (comprising 18 species) with ulcerative lesions (from 15 different locations) were confirmed with hyphae in fresh squash preparation or by histological evaluation. Squash preparations revealed nonseptate, sparsely branching, thick-walled hyphae; histological sections revealed mycotic granulomas in the dermis that occasionally penetrated into the skeletal muscle. These pathological characteristics were consistent with UM caused by the oomycete Aphanomyces invadans in Southeast Asia, Japan, Australia, and the United States. For specific identification, six isolates from ulcerated fish were cultured and prepared for molecular characterization using established diagnostic methods. Ribosomal RNA gene sequence analysis identified three isolates as Aphanomyces invadans, one as the oomycete Achlya bisexualis, and two as the ascomycete Phialemonium dimorphosporum. A more extensive survey of 67 ulcerated skin samples from fish collected between 1998 and 2003 was performed using a polymerase chain reaction assay specific for Aphanomyces invadans. Of these, 26 (38.8%) samples from seven fish species and nine collection locations were positive. Confirmation of UM associated with Aphanomyces invadans represents new host records in Florida for the sheepshead Archosargus probatocephalus, striped mullet Mugil cephalus, white mullet Mugil curema, silver perch Bairdiella chrysoura, black drum Pogonias cromis, largemouth bass Micropterus salmoides, and American shad Alosa sapidissima.  相似文献   

3.
Abstract

Blood parameters, disease resistance, and the immune response were sequentially evaluated in rainbow trout Oncorhynchus mykiss with proliferative kidney disease (PKD). The fish were maintained under laboratory conditions, and the study group went through a full cycle of the disease. Hematological and serological changes occurred primarily in those fish with severe kidney lesions. Fish infected with the parasite that causes PKD demonstrated a greater resistance to bacterial challenge, and their immune responses were heightened when compared with those of uninfected fish. These data suggest that PKD alone is not a predisposing factor for secondary infections if the fish does not incur severe renal lesions.  相似文献   

4.
Innate and acquired immune responses of Gilthead Seabream Sparus aurata was studied under normal culture and short-term stressful conditions for 18 months in offshore sea cages in Alghero Bay, Italy. Every 45 d, 50 fish were sampled and divided into two groups: fish in the first group (normal culture conditions) were bled after harvesting; fish in the second group were put into a tank under stressful conditions (crowding and confinement) and bled after 2 h. Innate humoral immunity, such as complement-like, hemagglutination, and lysozyme activities, was determined in the sera of both groups. Pathogen challenge was not performed, but the specific humoral immune response was assessed against the most common pathogens affecting cultured fish in Sardinia. Stressed fish, compared with the control, showed a lower lysozyme activity against Vibrio (Listonella) anguillarum, which was not clearly correlated with temperatures. Complement-like activity differed between the first and second half of the study and, at the end of the trial, a slightly higher activity was recorded in the controls than in the stressed fish. Hemagglutination activity was mainly higher in the stressed fish than in control fish. Confinement, crowding, and cold water temperature caused decreased lysozyme activity in short-term stressed Gilthead Seabream compared with those reared normally. The specific humoral immune response, against V. anguillarum, Tenacibaculum mesophilum, Enterococcus Seriolicida, and Aeromonas sobria, fluctuated during the rearing period, particularly during the first year of culture.

Received October 12, 2015; accepted March 24, 2016 Published online August 2, 2016  相似文献   


5.
Abstract

After an epizootic of amyloodiniosis (caused by the protozoan Amyloodinium ocellatum) in a commercial aquaculture facility for hybrid striped bass (female striped bass Morone saxatilis × male white bass M. chrysops), sera from these fish, as well as from others that had been experimentally immunized with the parasite, were evaluated by an enzyme-linked immunosorbent assay for antibody specific for the parasite. Titers were similar between the fish infested in culture and the experimentally immunized fish, and were significantly higher in both the cultured and artificially exposed fish than in unexposed fish. These results suggest that an infestation of A. ocellatum can stimulate the production of humoral antibodies to the parasite, providing further evidence that natural infestations of the parasite may confer protective resistance in fish that survive the initial parasitic infestation.  相似文献   

6.
Abstract

Channel catfish Ictalurus punctatus were exposed to a sublethal dose of infectious Ichthyophthirius multifiliis theronts, and eight serum analytes were measured. Sequential serum samples from each fish were collected for serum immediately before exposure, 4 d postexposure (PE), and 11 d PE. All fish developed moderately heavy infections with the parasite as indicated by the development of cutaneous lesions 5 d PE to infective theronts. Small but statistically significant changes in total protein, creatinine, and alkaline phosphatase values occurred after acute infection with I. multifiliis. Serum concentrations of glucose, albumin, urea nitrogen, alanine aminotransferase, and aspartate aminotransferase remained constant, indicating little disturbance of liver or kidney functions detectable by a serum biochemical profile established during an acute infection with I. multifiliis.  相似文献   

7.
Abstract

The effect of long-term freshwater acclimation on the blood and plasma ion composition of Red Drum Sciaenops ocellatus was investigated with the goal of elucidating the necessity of ion remediation. Four replicates (n = 50) of freshwater-acclimated (FW) fish (1.6 ± 0.2 g) were raised in 25-m3 tanks supported by 140,000 L of recirculating water. Four replicates (n = 50) of seawater (SW) fish groups were placed in 40-m3 offshore cages at 32–35 psu. Blood was collected from 100 fish (FW = 578 ± 50 g; SW = 686 ± 45 g) of each group (FW, SW) after 8 months of rearing. During the grow-out phase, the survival of FW and SW fish was 57.5% and 92.2%, respectively. The water ion composition (mainly the Ca2+/K+ [43%] and Ca2+/Mg2+ ratios [1%]) explained 56.6% of the plasmatic ion variability in the fish groups. Freshwater exposure produced significant reductions in osmolality and in several plasma indicators (Na+, Cl?, and Mg2+); the K+ levels from FW fish were the most compromised parameter. The water Ca2+/Na+ ratio had a greater influence (44%) on the plasma chemistry parameters, mainly glucose and creatinine. Freshwater-acclimated fish had a higher percentage of hematocrit, hemoglobin, and red blood cells than SW fish, but the water quality explained only 12.5% of the blood parameter variability between the FW and SW groups. The results support the conclusion that Red Drum tolerates salinity variations and can adopt a relatively stable condition for short periods; however, the data suggest that Red Drum have only a limited ability to withstand a hyposmotic environment for long periods due to their limited ability in maintaining K+ concentrations without external supplementation. Freshwater environments with high Ca2+/Na+, Ca2+/K+, and Ca2+/Mg2+ ratios appear to be a chronic stress factor that should be considered in future experiments.

Received June 11, 2012; accepted March 17, 2013  相似文献   

8.
Sablefish Anoplopoma fimbria are a prized seafood species due to their high oil content and white flaky flesh. Raising these species in culture can help to provide an important source of protein for humans and relief to declining wild fish populations. Understanding the environmental factors that influence the production of Sablefish is important for successful culturing. The significance of host–pathogen interactions in Sablefish culture and the resulting environmental implications are unknown. Pathogens could potentially cause losses of cultured Sablefish stocks due to disease, while Sablefish cultured in net pens may also serve as reservoirs for pathogens and potentially transmit disease to wild fish species. In this initial study, the susceptibility of juvenile Sablefish to three bacterial pathogens from the family Vibrionaceae was examined. Listonella anguillarum, Vibrio ordalii, and V. splendidus can pose serious economic threats to cultured fish and shellfish. Groups of juvenile Sablefish were exposed to five concentrations of each of the pathogens. Sablefish were susceptible to L. anguillarum, but were resistant to V. ordalii and V. splendidus at exposure concentrations of ≤1.32 × 107 CFU/mL and ≤3.57 × 106 CFU/mL, respectively. The greatest L. anguillarum concentration examined (8.7 × 106 CFU/mL) resulted in 24% mortality in juvenile Sablefish. A 24% loss of Sablefish stock could significantly influence an aquaculture program. As determined by multiple logistic regression, the survival of Sablefish to L. anguillarum exposure was significantly affected by their body mass, and larger fish had a greater probability of survival. Aquaculture operations could employ various strategies to minimize the loss of juvenile Sablefish by accounting for their size and known susceptibilities to pathogens.

Received December 9, 2014; accepted February 7, 2015  相似文献   


9.
Abstract

Mycobacterium peregrinum was isolated from multifocal, melanized nodular lesions in the carapace of the cultured marine shrimp Penaeus vannamei. This is the first identification of this species of Mycobacterium in shrimp. The lesions appeared to be the result of opportunistic infections in otherwise healthy animals. The presence of M. peregrinum in cultured shrimp has a direct negative impact on the marketability of shrimp because it causes obvious black lesions. The potential for accidental infections of shrimp farm or packing plant workers from handling infected shrimp is of concern since nodular skin lesions induced by the bacterium are difficult to treat.  相似文献   

10.
Abstract

The effect of water temperature on the progress of experimentally induced Cytophaga psychrophila infection was investigated in juveniles of coho salmon Oncorhynchus kisutch, chinook salmon O. tshawytscha, and rainbow trout O. mykiss (formerly Salmo gairdneri). A virulent strain of C. psychrophila was administered to fish by subcutaneous injection. Infected fish were held in tanks containing pathogen-free well water at temperatures ranging from 3 to 23°C. Mean times from infection to death of the fish were shortest at 12–15°C, which were the temperatures associated with the shortest time for doubling the population of this bacterium in vitro. Juvenile steelhead (anadromous rainbow trout) injected with viable C. psychrophila cells and held in 22°C water did not become diseased.  相似文献   

11.
Abstract

Laboratory exposures to the infectious stages (triactinomyxons) of Myxobolus cerebralis demonstrated a range of susceptibility to whirling disease among four species of inland salmonids. Replicate groups of each species were exposed to two concentrations of triactinomyxons, a low dose (100–200 per fish) and a high dose (1,000–2,000 per fish). Exposed fish were evaluated for clinical signs, for severity of microscopic lesions at 35 d, 2 and 5 months, and for spore concentrations in the head cartilage at 5 months. A standard strain of rainbow trout Oncorhynchus mykiss matched for age served as a susceptible species control. Rainbow trout, westslope cutthroat trout O. clarki lewisi, Yellowstone cutthroat trout O. clarki bouvieri, and bull trout Salvelinus confluentus were susceptible to M. cerebralis infections. Clinical signs, including radical swimming (“whirling”) and black tails, were observed at 7 weeks postexposure among rainbow and cutthroat trout challenged at 3 weeks of age. Clinical signs were rare among bull trout exposed at an age of 4 weeks and absent among rainbow and cutthroat trout exposed at 3 months posthatch. Most rainbow, cutthroat, and bull trout were found to be infected when examined at 5 months postexposure. The most severe microscopic lesions among infected fish at 5 months postexposure were found among rainbow trout. Cutthroat trout had less severe lesions, bull trout had mild infections, and no evidence of infection was found among Arctic grayling Thymallus arcticus. Mean spore concentrations among infected fish correlated with the severity of microscopic lesion scores. Rainbow trout had mean concentrations of spores in head cartilage reaching 106, whereas more resistant species such as bull trout had 104 spores; no spores were found among Arctic grayling at 5 months postexposure.  相似文献   

12.
Abstract

Proliferative gill disease (PGD), a condition not previously reported in wild fish, was found in two channel catfish Ictalurus punctatus sampled from the Tennessee-Tombigbee Waterway in Mississippi during June and July 1989. The parasite thought to cause PGD was observed in only one of the fish, but the distinctive lesions associated with this disease were prominent in both of the channel catfish. Organisms resembling the PGD parasite were also found in the gills of 4 of 18 largemouth bass Micropterus salmoides and 6 of 20 bluegills Lepomis macrochirus, but there was little or no host response to these parasites.  相似文献   

13.
An epidemiological cohort study of Cryptosporidium scophthalmi in cultured turbot Psetta maxima L. of Northwestern Spain was conducted along a four-year period. Four different ongrowing cohorts were monitored monthly from introduction into the ongrowing tanks (10–50 g) until reaching market size (400–1400 g). The association of host and environmental factors with five categories of parasite abundance was assessed using a multivariable regression framework. Epidemiological factors assessed here were water temperature, weight, length, month of collection, season, age, origin, condition factor, water filtration, and status to the myxozoan Enteromyxum scophthalmi infection. E. scophthalmi was included into the analysis because it targets the same organ than C. scophthalmi and it was prevalent in the studied population. The multivariable analysis demonstrated the statistically significant association between several factors and parasite abundance. C. scophthalmi abundance was associated (P < 0.05) with age, condition factor, season, and status to E. scophthalmi infection. Young animals, with poor condition factor, during spring or summer, and not infected with the myxozoan were most likely to be highly infected by C. scophthalmi. Inclusion of these four variables significantly (P < 0.05) improved the model, compared to the model that did not include any of these epidemiological factors. Increasing levels of C. scophthalmi abundance were associated (P < 0.01) with higher severity of C. scophthalmi-compatible lesions. The frequency of distribution of C. scophthalmi abundance was clearly right-skewed and fitted a negative binomial distribution, whereas the intensity of infection fitted a Poisson distribution. The quantification of the variance-to-mean ratio stratified by age demonstrated overdispersion for 8–16 months old fish, although this bivariate association is likely affected by several other factors, as suggested by the results of the multivariable analysis. The negative relation between C. scophthalmi abundance and status to E. scophthalmi infection suggests differences in the transmission, onset, and course of both infections. The coarse filtration used in some cohorts did not significantly affect the levels of infection. C. scophthalmi was probably introduced into the ongrowing tanks mainly with carrier fish, though the involvement of infective oocysts from the water supply cannot be disregarded. Infection prevalence and mean intensity decreased with fish age and a seasonal distribution was found. Results presented here will help to understand the epidemiology of C. scophthalmi in turbot, to estimate the expected levels of infection associated with presence or absence of epidemiological factors, and to quantify the impact that the disease may have on susceptible turbot populations. The multivariable model used here is more powerful than the visual inspection of graphics for exploring associations in cooperative processes and can be easily extended to the assessment of epidemiological associations in other population and parasitic diseases.  相似文献   

14.
Abstract

A nonradioactive in situ hybridization (ISH) protocol was developed to detect Myxobolus cerebralis, the causative organism of whirling disease, in its primary host, rainbow trout Oncorhynchus mykiss, and in its alternate oligochaete host, Tubifex tubifex. A cocktail of three oligonucleotide primers (derived from the small subunit ribosomal DNA sequence) directed at target sequences of the parasite DNA was tailed at the 3′ end with digoxigenin-labeled deoxyuridine triphosphate (DIG-dUTP). Labeled probes were hybridized to parasite DNA present in deparaffinized tissue sections from infected trout and oligochaetes. The bound probes were visualized after modifications of existing ISH protocols. By using the new ISH procedure, the parasite was found in target tissues of subclinically and clinically infected fish and tubificid oligochaetes after exposures of these hosts to triactinomyxons and mature spores, respectively. The probe did not bind with salmonid tissues infected with two other myxosporean parasites, Ceratomyxa shasta or the PKX organism, or to a Myxobolus sp. infecting the cartilage of plain sculpin Myoxocephalus jaok. These initial results indicate that ISH is an effective and specific test for detecting Myxobolus cerebralis in its fish and oligochaete hosts.  相似文献   

15.
Abstract

The risk of fish pathogen transmission via eggs can be reduced by disinfection in ozonated seawater. The aim of this study was to determine the suitable conditions for ozone disinfection of the eggs of gilthead seabream Sparus aurata, sea bass Dicentrarchus labrax, red porgy Pagrus pagrus, and common dentex Dentex dentex. The eggs were disinfected with a concentration (C) of 0.5 mg of ozone/L of water at four different exposure times (T = 2, 4, 8, and 16 min). The hatching rate was determined in triplicate for each treatment. Bacterial colonies were counted on tryptic soy agar and thiosulfate–citrate–bile salts–sucrose agar. At the end of the experiment, bacterial load and hatching rate were assessed together to determine the optimal ozone treatment values, which were estimated in CT units (i.e., C [= 0.5 mg/L] × T [min]). Optimal values were CT 2–4 (T = 4–8 min; 18°C) for gilthead seabream and red porgy, CT 2 (T = 4 min; 18°C) for common dentex, and CT 4 (T = 8 min; 15°C) for sea bass.

Received April 12, 2011; accepted February 2, 2012  相似文献   

16.
Abstract

Streptococcus iniae, the etiological agent of streptococcosis in fish, is an important pathogen of cultured and wild fish worldwide. During the last decade outbreaks of streptococcosis have occurred in a wide range of cultured and wild fish in the Americas and Caribbean islands. To gain a better understanding of the epizootiology of S. iniae in the western hemisphere, over 30 S. iniae isolates recovered from different fish species and geographic locations were characterized phenotypically and genetically. Species identities were determined biochemically and confirmed by amplification and sequencing of the 16S rRNA gene. Repetitive-element palindromic PCR fingerprinting as well as biochemical and antimicrobial susceptibility profiles suggest that a single strain of S. iniae was responsible for two different disease outbreaks among reef fishes in the Caribbean, one in 1999 and another in 2008. Interestingly, a majority of the isolates recovered from cultured fish in the Americas were genetically distinct from the Caribbean isolates and exhibited a trend toward higher minimal inhibitory concentration with respect to several antibiotics as well as greater genetic variability. The biological significance of this genetic variability is unclear, but it could have implications for future vaccine development and treatment.

Received April 20, 2014; accepted July 7, 2014  相似文献   

17.
Abstract

A series of experiments was carried out with infectious hematopoietic necrosis virus (IHNV; 193-110 isolate) in rainbow trout Oncorhynchus mykiss (weight, ～1.2 g) to determine the duration of the patent period and the timing of onset of the infectious periods. We first attempted to transmit IHNV to recipient fish from infected rainbow trout 2–3 d after they had been exposed. No infection transfer occurred despite high titers (104.79 to 104.91 plaque-forming units 5–8 d postexposure (dpe). To determine the number of secondary cases produced by one infectious individual, we exposed approximately 50 rainbow trout (weight, ～1.5 g) in each of seven replicate tanks to a donor fish that had been infected with virus by bath exposure 3 d earlier. The prevalence of infection in recipient fish rose from 0.84% at 2 dpe to 7.9% at 6 dpe. Maximum incidence (22 cases) occurred between 2 and 4 dpe. No disease-specific mortalities occurred in recipient fish during the experiment. The titer of virus in both recipient and donor fish increased from 2 to 4 dpe. There was a positive correlation between the level of infection among donors and prevalence values among recipient fish (r 2 = 0.60). The level of challenge by one infectious fish under the conditions provided was enough for infection transfer from sick cohabitant to susceptible fish but was not enough for initiation of a full-scale epizootic among recipients.  相似文献   

18.
Abstract

Francisellosis is an emergent disease in cultured and wild aquatic animals. The causative agent, Francisella noatunensis subsp. orientalis (Fno), is a gram-negative bacterium recognized as one of the most virulent pathogens of warmwater fish. The main objective of this project was to investigate the prevalence of Fno in cultured tilapia (specifically, Mozambique Tilapia Oreochromis mossambicus, Koilapia [also known as Wami Tilapia] O. hornorum, Blue Tilapia O. aureus, and Nile Tilapia O. niloticus hybrids) on the island of Oahu, Hawaii, using conventional and real-time PCR assays followed by statistical modeling to compare the different diagnostic methods and identify potential risk factors. During 2010 and 2012, 827 fish were collected from different geographical locations throughout the island of Oahu. Upon collection of fish, the water temperature in the rearing system and the length of individual fish were measured. Extraction of DNA from different tissues collected aseptically during necropsy served as a template for molecular diagnosis. High correlation between both molecular methods was observed. Moreover, the bacterium was isolated from infected tilapia on selective media and confirmed to be Fno utilizing a species-specific Taqman-based real-time PCR assay. Although a direct comparison of the prevalence of Fno between the different geographical areas was not possible, the results indicate a high prevalence of Fno DNA in cultured tilapia throughout the farm sites located on Oahu. Of the different tilapia species and hybrids currently cultured in Hawaii, Mozambique Tilapia were more susceptible to infection than Koilapia. Water temperature in the rearing systems and fish size also had a strong effect on the predicted level of infection, with fish held at lower temperatures and smaller fish being more susceptible to piscine francisellosis.

Received November 30, 2012; accepted February 22, 2013  相似文献   

19.
Sharpsnout bream (Diplodus puntazzo) has been used in Adriatic aquaculture for less than a decade, but the decreasing trend of rearing this species will probably result in its complete substitution by more exploited sea bream (Sparus aurata). Only two facilities still rear both fish species in neighbouring cages in monoculture. A switch of parasites was observed between sparids during monitoring of the gill monogeneans of farmed fish. In wild fish of the Adriatic Sea, Lamellodiscus elegans (Monogenea: Monopisthocotylea) has previously been reported in annular (Diplodus annularis), and two-banded sea bream (D. vulgaris) and sharpsnout bream (D. puntazzo), and the present study confirmed its presence also in sea bream, in low prevalence and abundance. The exclusively sea bream monogenean Sparicotyle chrysophrii (Monogenea: Polyopisthocotylea) was also isolated from sharpsnout bream, showing prevalence and abundance values even higher than in its resident host. In the occurrence of L. elegans in sea bream, the opportunistic switch resulted in lower abundance and prevalence than in the original host, while in the second case of switching the monogenean S. chrysophrii showed better reproductive capacity on a new host (sharpsnout bream). Both cases point to the possible enlargement of parasite host range.  相似文献   

20.
A field investigation was conducted in the Sesheke District of Zambia along the Zambezi River to determine the fish species susceptible to epizootic ulcerative syndrome (EUS), a newly confirmed disease in Southern Africa. A total of 2,132 fishes were inspected for gross EUS-like lesions, of which 188 (8.82%; 95% CI = 7.67–10.1%) were found with typical characteristic lesions of EUS. Of these 188 samples, 156 were found to have mycotic granulomas on histopathological analysis, representing 83.0% (95% CI = 76.7–87.9%) of the initially identified in the laboratory through gross examination. The following 16 species of fish were examined and found with EUS lesions; Clarias ngamensis, Clarias gariepinus, Barbus poechii, Tilapia sparrmanii, Serranochromis angusticeps, Brycinus lateralis, Micralestes acutidens, Sargochromis carlottae, Hydrocynus vittatus, Phryngochromis acuticeps, Schilbe intermedius, Hepsetus odoe, Labeo lunatus, Oreochromis andersonii, Barbus unitaeniatus, and Barbus paludinosus. T. sparrmanii did not show any lesions, while the Clarias species were found to be the most afflicted with EUS. These results could be useful to fish farmers and organizations interested in improving aquaculture in the area.  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