呋喃唑酮代谢物AOZ在斑点叉尾(鲴)体内组织分布与消除规律研究

研究了在池塘网箱养殖模式下,平均水温为30.6℃,以100 mg/kg鱼体重的剂量投饲斑点叉尾鲴(Ietalurus punetaus)苗种(95±20.9)g含呋喃唑酮的药饵,连续5d,每天2次.采用高效液相色谱串联质谱(HPLC-ESI/MS/MS)法分析了呋喃唑酮主要代谢产物3-氨基-2-噁唑烷酮(3-amina...     

酶联免疫法测定水产品中呋喃唑酮代谢物残留量

为测定水产品中呋喃唑酮代谢物(AOZ)的残留量,采用2-硝基苯甲醛进行衍生,乙酸乙酯提取AOZ。通过样品中残留的AOZ和酶标板上预包被的抗原竞争抗体,加入酶标二抗后与底物显色,测得样品中AOZ的残留量。测定了四组水产品中AOZ的残留量,测定浓度均小于1μg/kg,结果为阴性。向空白样品中分别添加0.5μg/kg、1.5μg/kg和2μg/kg的AOZ标准品,回收率为90%、109%和101%。因此得出结论:采用酶联免疫法测定水产品中AOZ残留量操作简单,检测时间短,结果准确,是一种适合大批量水产样品筛选的检测方法。     

Effects of Estradiol Valerate on Steroid Hormones and Sex Reversal of Female Rice Field Eel,Monopterus albus (Zuiew)

The rice field eel, Monopterus albus (Zuiew), is an important aquaculture fish in many Asian countries. Productivity, however, is limited by low fecundity as a result of sex reversal of female juveniles of this fish. This study was conducted to investigate the effects of estradiol valerate on the sex reversal process of this fish by determining sex changes of initial 2‐yr‐old female eels (26.5 ± 2.6 cm, 21.9 ± 2.1 g) treated with three concentrations of estradiol valerate: 0 mg/kg (Control, Group A), 10 mg/kg (Group B), and 50 mg/kg (Group C). In Group A, sex reversal took place with significantly higher percentage of sex change: about 45% of female eels to intersexes and males. Only about 22% of female eels changed to intersexes and males in Group B, but no sex reversal occurred in Group C during the experimental period. The result also indicated that the gonadal development and the concentrations of serum estradiol (E₂) and testosterone (T) varied significantly with different concentrations of dietary estradiol valerate. Serum T significantly reduced but serum E₂ significantly increased in Group C compared to the control Group A. The results demonstrated that estradiol valerate affected the secretion of sex steroid hormones in rice field eels and thus inhibited the sex reversal process at a low concentration (10 mg/kg) or stopped the sex reversal process at a high concentration (50 mg/kg) of estradiol valerate. These results suggest that a higher yield of mature female eels could be achieved by treatments with estradiol valerate, thus enhancing the fecundity of this rice field eel.     

Humoral immune response of Japanese eel, Anguilla japonica Temminck & Schlegel, to Pleistophora anguillarum Hoshina, 1951 (Microspora)

A humoral response of Japanese eel, Anguilla japonica Temminck & Schlegel, to the microsporean Pleistophora anguillarum Hoshina was demonstrated using immunoblotting and an enzyme-linked immunosorbent assay (ELISA). Japanese eel immunoglobulin was purified by affinity chromatography. The immunoglobulin was composed of 25-kDa light chains and 72-kDa heavy chains. The ELISA values of P. anguillarum antibodies in naturally infected fish sera were significantly higher than those of clinically healthy fish. Spore proteins from the microsporean were separated by electrophoresis and subjected to analysis by Western blot. Sera from naturally infected fish showed different reaction patterns to the spore proteins. While the sera randomly selected from naturally infected eels all showed a significant positive reaction to P. anguillarum antigens, the mucus from only three out of the nine infected eels reacted positively in the ELISA test. Subsequent analyses indicated that there was no significant difference in the amount of mucus immunoglobulin among the tested eels. Therefore, the generally lower ELISA values of mucosal anti-P. anguillarum antibodies from the infected eels tested were evidently not caused by a lack of immunoglobulin per se, but seem to be the result of a lack of anti-P. anguillarum antibodies in the mucus and/or a lower affinity in the anti-P. anguillarum antibodies that were present.     

Insulin-like growth factor I of Japanese eel, Anguilla japonica: cDNA cloning, tissue distribution, and expression after treatment with growth hormone and seawater acclimation

In an attempt to understand growth regulation in the Japanese eel, Anguilla japonica, we cloned insulin-like growth factor-I (IGF-I) cDNAs and examined their mRNA expression in several tissues. Two eel IGF-I (eIGF-I) cDNAs encoding preprohormones, eIGF-I-Ea1and eIGF-I-Ea2, were cloned from the liver by polymerase chain reaction (PCR). The preproIGF-Is were identical in signal peptide and mature IGF-I, but different in the E domain—eIGF-I-Ea2 mRNA was 36 bp longer than eIGF-I-Ea1 mRNA. Eel IGF-I was 83–94% identical with that of teleosts, 71% identical with that of dogfish, 87% identical with that of bullfrog and chicken, and 83% identical with that of humans. In both males and females the highest eIGF-I-Ea1 mRNA levels were observed in the liver, with detectable levels also found in the gills, heart, stomach, spleen, kidney, intestine, swim-bladder, muscle, and gonads. eIGF-I-Ea1 mRNA levels in the liver were higher in females than in males whereas in the intestine they were lower than in males. eIGF-I-Ea2 mRNA was detected in all the tissues examined and at similar levels in males and females. In this experiment higher eIGF-I-Ea1 mRNA levels were observed in the liver of larger glass eels than in those of smaller fish. eIGF-I-Ea2 mRNA levels were also higher in larger eels, although they were lower than IGF-I-Ea1 mRNA levels. Both eIGF-I mRNA levels in liver were positively correlated with the body size of the␣glass eels. Intraperitoneal injection of recombinant eel GH (reGH), 0.25 μg g⁻¹ body weight, into glass eels resulted in a significant increase in both eIGF-I mRNAs in the liver 1 day after injection compared with control fish, but no elevation was observed 2 days after injection. Incubation of liver slices with reGH at concentrations of 10, 100, and 1,000 ng mL⁻¹ for 24 h resulted in a significant concentration-dependent increase in the levels of both eIGF-I mRNAs. Higher levels of eIGF-I-Ea1 and Ea2 mRNA were observed in the gills ofseawater-reared eels than in those of freshwater-reared fish, but no differenceswere observed in the whole kidney. These results suggest that IGF-I is involved in the regulation of somatic growth and also in adaptation of the Japanese eel to seawater.     

Temporal changes in European eel, Anguilla anguilla, stocks in a small catchment after installation of fish passes

Abstract  Changes in the abundance of European eel, Anguilla anguilla L., in the River Frémur, France, were examined over an 8-year period. Natural connectivity of the river was disturbed by three high dams that inhibited eel upstream migration and reduced recruitment by elvers and yellow eels. After eel passes were installed, fish became more abundant upstream (mean density 0.5 eel m⁻²). Moreover, except in the more upstream areas, no decline in eel numbers and biomass was found, in contrast to the general decline of eel throughout its distribution range. It was concluded that eel passes are important to conserve and/or to recover eel stocks.     

Migration of silver eel,Anguilla anguilla,through three water pumping stations in The Netherlands

European eel, Anguilla anguilla (L.), migrating to sea encounter many man-made structures that can hamper and delay migration or induce mortality. Three pumping stations in Friesland, the Netherlands, were covered with acoustic receivers. Ninety-three silver eels tagged with acoustic transmitters were released in the polders upstream of the stations and 89% were detected passing a pumping station. The majority of silver eels passed the stations within a day after arriving at the station. Four silver eels stayed for longer than 2 weeks before passage, and 18 were detected at the receiver downstream the pumping station for more than one day, with detections up to several weeks. These detections probably indicated a dead eel, but could also indicate a live eel remaining at the site. Most of the silver eels passed the pumping stations within a day after release, so fish-friendly pumps will benefit the migrating population most. In the Netherlands, there are several thousand pumping stations. Installing fish passages near these stations is not feasible due to high costs. Prioritising all these sites in relation to the degree of blockage, mortality rates and its relative importance for migratory fish, can maximise the effectiveness of measures and mitigation taken.     

Somatic growth, survival, feed utilization and starvation in European elver Anguilla anguilla (Linnaeus) under two different photoperiods

The aim of the study was to determine the effect of two photoperiod regimes under artificial conditions on growth performance and survival in the European eel Anguilla anguilla during the transition from glass eel to elver. The fish were held in 12-h-light:12-h-dark (12L:12D) and in continuous darkness (DD) in fed and fast trials lasting 80 days. Fed fish kept in the dark showed higher somatic growth, and a better feed conversion ratio, higher protein and lipid content, with significant differences between treatments. Dark environment increased the survival rate in comparison with fish exposed to 12L:12D, during which eels showed lower survival rates and greater variations in size. Fasted fish suffered loss of body mass in both photoperiods at the end of the experimental phase, but fish exposed to 12L:12D lost more body mass. These results indicate that the photoperiod is a key factor during the glass eel–elver stage, which may contribute to optimizing the early stages of eel culture.     

Epidermal response of the Japanese eel to environmental stress

Nonspecific responses of Japanese eels to environmental stress were monitored by assaying various lytic activities in eel epidermal extract. In fish maintained at 10 and 30 °C for up to 10 days, epidermal proteolytic activities due to serine protease and aminopeptidase and hemolytic activity varied within a 2-fold value range. Other proteolytic activities, due to cathepsins B and L, in the fish at 30 °C increased for up to 8 days and were 3.4 and 2.9-fold over those in fish maintained at 10 °C, respectively. This was accompanied by a 3.0-fold increase in bacteriolytic activity. Other forms of stress were exerted on the fishes by immersing them in a suspension of Flavobacterium columnare or giving them intraperitoneal injections of Edwardsiella tarda over 72 h. Although serine protease and aminopeptidase activities and hemolytic activity in the fishes exposed to F. columnare changed marginally, and were similar to those in the control fish, cathepsins B and L activities in the infected fishes increased more than 1.5-fold over their initial values over a 48 h period, along with a 4.5-fold increase in bacteriolytic activity. No marked change was detected in any of the lytic activities of the fishes exposed to E. tarda. These findings indicate that epidermal cathepsins B and L probably participate in bacteriolysis associated with Japanese eel skin and that their activities are elicited by environmental stimuli and may be an important nonspecific response of eels. Abbreviations: Cbz – carbobenzoxy; MCA – 4-methylcoumaryl-7-amide.     

Differences in head shape of the European eel, Anguilla anguilla (L.)

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).     

Improving water quality following the death of Asian swamp eel (Monopterus albus) in cage culture through monitoring of ammonia nitrogen levels

Water quality management is important in cage culture of the Asian swamp eel (Monopterus albus). However, it is difficult to manage water quality after a large number of eels have died within the cages. The present study seeks to solve this problem by establishing a method to judge and maintain water quality. To this end, the effect of temperature and eel body weight on the water quality and microorganisms after the death of Asian swamp eels have been examined in the laboratory. The results showed that the changes in water quality parameters were similar at different temperatures and different eel weights. For example, at 26°C, the water quality started deteriorating at 5–7 days after death, which corresponded to the oxygen consumption stage. This was followed by the anaerobic decomposition stage at 11 days after death, at which point the self‐purification process of the water body was initiated. Under a lower temperature of 18°C, the oxygen consumption stage and, therefore, the overall decomposition process were extended. Proteobacteria, Bacteroidetes and Verrucomicrobia were the dominant phyla detected during the decomposition process, but the relative proportions of the dominant families differed across the stages. Based on these findings, we have provided innovative suggestions for water quality detection and management in Asian swamp eel production: (i) at a water temperature of 16–23°C, the following measures should be taken to deal with dead eels 15 days after the introduction of seedlings: (a) at an ammonia nitrogen level higher than 2 mg/L, the bodies present at the bottom of the cage need to be fished out with a net. However, when the ammonia nitrogen level is not higher than 2 mg/L, the whole cage should be sprayed with detoxifying substrate improver or Bacillus powder, according to the instructions, to improve water quality. (ii) At a water temperature of 23–30°C, the above measures should be taken on the 6th day after the seedlings are released, provided the critical value of ammonia nitrogen is 1.57 mg/L. An important limitation of this study is that water exchange was not possible under the laboratory experimental conditions, and the deterioration of water quality caused by eel death may have been alleviated due to water exchange between the inside and outside of the cage.     

Antibody production in Japanese eels, Anguilla japonica Temminck & Schlegel

Adult Japanese eels, Anguilla japonica Temminck & Schlegel, (200–250 g, 45–55 cm) were immunized by intramuscular injection with goat IgG. After 5 weeks, eel immunoglobulin (Ig) was purified using affinity chromatography. The purified eel Ig was used to immunize rabbits to produce anti-eel Ig antibody. The highest antibody ELISA value in eels was reached 3 weeks after initial immunization with goat IgG, and then gradually decreased. The antibody could still be detected at 140 days post-immunization. The optimal temperature for antibody production was 30°C. Freund's complete adjuvant and secondary immunization both increased antibody production in eels.     

虾苗使用呋喃西林和呋喃唑酮的残留评估

使用质量浓度为1mg·L^-1的呋喃西林和呋喃唑酮,以混饲的方式对凡纳滨对虾（Penaeus vannamei）幼苗给药,研究呋喃西林和呋喃唑酮在凡纳滨对虾苗体内的代谢和消除规律,对药物的残留时间和残留量等进行风险评估。呋喃西林在凡纳滨对虾幼苗体内的消除速率常数（ke）为0．041h^-1,消除半衰期（t1/2ke）为17．091h,其代谢物氨基脲（SEM）在50d后未检出;呋喃唑酮的ke为0．045h^-1,t1／2ke为15．258h,其代谢物3-氨基-2-恶唑烷基酮（AOZ）在20d内已低于方法检测限。结果表明,在凡纳滨对虾培苗期,以此试验方式使用呋喃西林和呋喃唑酮不会导致其在成虾体内的残留。     

Synthesis and possible function of 11-ketotestosterone during oogenesis in eel (Anguilla spp.)

The control of 11-ketotestosterone (11-KT) biosynthesis and its physiological roles were examined in female Japanese eel (Anguilla japonica) and New Zealand longfinned eel (Anguilla dieffenbachii). 11-KT was detected in serum of female eels of both species. Among various tissues from Japanese eel, the ovary had the greatest capacity to synthesize 11-KT in vitro. In addition, the oocyte diameters of eels treated with 11-KT had increased significantly. Furthermore, these oocytes were found to have an increased number of oil droplets. These findings suggest that 11-KT in female eels may be mostly of ovarian origin and that this androgen appears to play an important role in controlling pre-vitellogenic oocyte growth.     

孔雀石绿及其主要代谢产物在欧洲鳗鲡体内的蓄积及消除规律

为了解孔雀石绿及其有毒代谢产物无色孔雀石绿在鱼体中的蓄积与消除规律,达到对孔雀石绿的禁用监控,本试验对初始体重为12.42±2.18 g的欧洲鳗鲡进行0.1 mg/L药浴24 h,再转移到清水中养殖120d,采用高效液相色谱法测定血液、肝脏、肾脏和肌肉组织中孔雀石绿(MG)及其代谢物无色孔雀石绿(LMG)的残留。结果表明:在药浴开始阶段,肝脏、肾脏和肌肉中的MG含量迅速上升,肝脏、肾脏和血液于浸浴6 h时即达到最高平均值,分别为859.8±127.0μg/kg、589.2±40.0μg/kg和88.6±51.3μg/kg,肌肉于浸浴12h时达最高值(720.5±192.6μg/kg),随后含量下降。鳗鲡各组织中LMG高峰出现时间都晚于MG,血液、肝脏和肾脏中的LMG都是在浸浴12 h时,达到最高平均值,分别为1 135.0±376.4μg/kg、1 730.9±538.5μg/kg和238.9±105.5μg/kg;肌肉组织LMG的高峰出现时间更晚,是清水养殖3 d(72 h)时,为960.1±251.0μg/kg。血液中的MG消除最快,于清水养殖的第2天(48 h)检测不到残留。肾脏于养殖10 d(240 h)、肝脏于养殖45 d(1 080 h)时检测不到残留MG,而肌肉中的MG在养殖90 d时才检测不到。LMG在鳗鲡血液和肌肉组织中消除时间与MG相比显著延长,血液中的LMG消除时间是养殖90 d(2 160 h),而肌肉中于养殖120 d时,仍能检测到一定含量的LMG。除了肾组织在整个试验阶段和肌肉组织在浸浴过程中,所含平均MG比LMG高以外,其余情况下都是LMG平均含量明显高于MG平均值。本试验表明,可以通过对鳗鲡肌肉中的无色孔雀石绿残留的检测达到对孔雀石绿禁用的监控。     

Stanniocalcin kinetics in freshwater and seawater european eel (Anguilla anguilla)

The kinetics and hypocalcemic potency of stanniocalcin (STC) were examined in freshwater and seawater eels. The secretion rate and the metabolic clearance rate of STC were calculated from the STC disappearance curve after intra-arterial injection of trout STC. Basal plasma STC concentrations in freshwater and seawater eels did not differ but the STC secretion rate and metabolic clearance rate in seawater eel were 70–75% higher than in FW eel. The increased STC distribution space in seawater eels suggests that the STC receptor density was increased. STC had a higher hypocalcemic potency in seawater than in freshwater eels. These observations support the hypothesis that seawater fish require more hormonal control over transcellular influx of calcium than freshwater fish.To whom correspondence should be addressed.     

Distinct regional profiles of trace element content in muscle of Japanese eel Anguilla japonica from Japan, Taiwan, and China

Trace element distribution patterns were examined in Japanese eel from five Asian regions for the purpose of identifying the elements and patterns that could be used to determine provenance. Distinctive patterns were found in eels from the Japanese prefectures of Miyazaki, Kagawa, and Shizuoka, and from Taiwan and China. The levels of six trace elements, selenium, mercury, copper, manganese, zinc, and arsenic, in muscle tissue varied among eels of different origins, and factorial analysis of the elemental patterns showed that Factor 1 was attributable to selenium and mercury levels and Factor 2 to zinc and copper levels. Multivariate analysis showed that the patterns of elemental composition in fish muscle were mainly differentiated by these two factors.     

Modification in Body Fat Content and Fatty Acid Profile of Wild Yellow Shortfin Eel,Anguilla australis,through Short‐term Fattening

Wild‐catch eels with low fat content are either not accepted at all or accepted as a lower‐quality and less valuable product in the global eel market. This study was undertaken with the goal of increasing the fat content of yellow shortfin eel, Anguilla australis (104 ± 11 g initial weight), captured in the wild and kept in captivity for a short period, as well as assessing their rate of growth. An 86‐d feeding trial was conducted indoors in a recirculation aquaculture system, at 25.5 ± 1.6 C. Two commercial extruded dry feeds were tested; one formulated for European eel and one not specifically intended for use on eels. Good values of specific growth rate (1.10 and 1.12%/d) and feed conversion ratio (1.01 and 1.10) were achieved with both tested feeds. At the end of the trial, eels achieved 20–22% total fat, starting from wild fish with 7% fat content. Fat quality of the fattened eel was appreciably superior (higher proportion of omega‐3 fatty acids) than the fat of eels captured in the wild. The results of this study are encouraging for the prospect of fattening yellow shortfin eels and obtaining a market‐oriented eel product.     

The efficacy of Aqui‐S vet. (iso‐eugenol) and metomidate as anaesthetics in European eel (Anguilla anguilla L.), and their effects on animal welfare and primary and secondary stress responses

The effects of 40 mg/L metomidate and 300 mg/L iso‐eugenol (i.e. 600 mg/L Aqui‐S vet.) anaesthesia on the stress response in European silver eel during a process of complete anaesthesia, recovery and long‐term survival were studied. Metomidate is a hypnotic agent with no analgesia, whereas Aqui‐S vet. is a true anaesthetic. There was no difference between fish exposed to Aqui‐S vet. and metomidate, with respect to time to anaesthesia (mean 3.8 and 2.6 min respectively) and recovery (mean 7.6 and 6.5 min respectively). For the metomidate group, the plasma cortisol concentration increased to a peak during the recovery phase, and was significantly higher than for the Aqui‐S vet. group, which showed no such increase. Fish were kept in tanks with seawater for monitoring of long‐term survival (4 months) after anaesthesia treatment, and no mortality was observed in either group. The results indicate that metomidate is a potential stressor to European eels during exposure, and we do not recommend using metomidate in this species. Aqui‐S vet., however, seems promising as a stress‐reducing anaesthetic for European eel, and if used properly could improve animal welfare and survivability during and after common ecology‐related procedures, as capture, tagging and size measuring.