Ploidy level,morphological characteristics and performance of interploid hybrids by Megalobrama amblycephala♀× allo‐tetraploids ♂

Interploid hybrids were produced by mating allo‐tetraploid males, an interspecific tetraploidy induced by blunt snout bream (Megalobrama amblycephala) ♀× black bream (Megalobrama terminalis) ♂, with blunt snout bream females. The fertilization rate was high in the interploid hybrids. Although significant (P<0.05) mortalities were observed at hatching, swim‐up and 30‐day stages, respectively, the survival percentage of the interploid hybrids became stabilized after the 60‐day stage. In different interploid hybridization batches, 64–97% of juveniles were identified as 3n and 1–36% as 2n. Less than 2% of tetraploids were obtained in these interploid hybridization batches. The daily growth rate of the interploid 3n increased 7.5%, compared with that of diploid blunt snout breams during the 180‐day culture. Moreover, a method using seven morphological parameter ratios was set up with a relatively high classification accuracy of 93.8% to harmlessly discriminate interploid 3n from allo‐tetraploids, black bream and blunt snout bream.     

Production of interploid triploids by 4n × 2n blunt snout bream (Megalobrama amblycephala. Yih) and their first performance data

Positive and negative interploid triploids of blunt snout bream (Megalobrama amblycephala) were produced by reciprocal crossing autotetraploids with diploids. Fertilization and hatching rate of negative interploid triploid, 2n♀× 4n♂, at different reproductive ages was similar to that of control, but higher than that of positive interploid triploid, 4n♀× 2n♂. Additionally, the development rate of embryos of the positive interploid triploid, 4n♀× 2n♂, was slower than that of control and the negative interploid triploid, 2n♀× 4n♂. Gonad growth of the positive and negative interploid 3n was significantly (P<0.01) affected by parents, and spawning could not be induced both in females and males at the 2+ age. The negative interploid 3n (2n♀× 4n♂) had a significantly higher survival rate than the positive interploid 3n (4n♀× 2n♂), but close to the level of the control (P<0.05). The daily growth rate of the negative interploid 3n was similar to that of the good breed ‘Pujiang No. 1’ blunt snout bream (2n) during the early life stages.     

Dietary choline requirement for juvenile blunt snout bream,Megalobrama amblycephala

A 12‐week feeding trial was conducted to determine dietary choline requirement for juvenile Megalobrama amblycephala. The basal diet was formulated to contain 310 g kg^?1 diet from vitamin‐free casein and gelatine. Choline chloride was supplemented to the basal diet to formulate six purified diets containing 0, 250, 500, 1000, 2000 and 4000 mg kg^?1, respectively. Each diet was randomly fed to quadrupled groups of Megalobrama amblycephala with initial average weight 1.84 ± 0.04 g in a flow‐through system. Results showed weight gain was increased significantly with increasing dietary choline levels (P < 0.01). Lipid content of liver decreased significantly as dietary choline concentration increased (P < 0.01), whereas lipid content of dressed carcass showed opposite trend (P < 0.01), and lipid content of whole‐body was unaffected by dietary choline supplementation. Broken‐ line regression of weight gain, liver and muscle choline concentration showed choline requirements of Megalobrama amblycephala of 1198, 1525 and 1365 mg kg^?1, respectively. In addition, dietary choline supplementation significantly improved lipid content of dressed carcass but not the content of whole body of blunt snout bream.     

Response to individual selection for age at sexual maturity in Atlantic salmon

Atlantic salmon (Salmo salar) that mature sexually at 1 year of age (as parr or precocious males), at 4 years of age (after two winters in the sea) and at 5 years of age (after three winters in the sea) were used to study response to individual selection for age at sexual maturity. Six mating groups were made: between fish of the same age (4 × 4 and 5 × 5); reciprocal matings between 4- and 5-year-old fish (4 × 5 and 5 × 4); and matings between 1-year-old precocious males and 4- and 5-year-old females (1 × 4 and 1 × 5). Parental age at sexual maturity was found to influence markedly the offspring age at sexual maturity. The heritability for age at maturity in the sea was estimated at 0.48 ± 0.20 from the offspring—dam regression. It is concluded that there is considerable opportunity to alter the age at sexual maturity in Atlantic salmon through selection. Evidence was found that maturation of parr is a heritable trait and that it is independently inherited from maturation in the sea.     

鲂属鱼类形态差异分析

为探讨鲂属鱼类种内及种间形态差异,采用单因素方差分析及主成分分析对厚颌鲂(Megalobrama pellegrini)、广东鲂(M.hoffmanni)、鲂(M.skolkovii)和团头鲂(M.amblycephala)共382尾样本的23个可数性状和24个可量性状进行分析和比较。结果表明,4种鲂的可数性状(尾部脊椎数),可量比例性状(口宽/头长、眼径/头长、腹鳍棘长/头长、肠长/体长、尾柄高/体长、第一鳔室长/体长、第二鳔室长/第一鳔室长、尾柄长/尾柄高)存在显著性差异,可作为4种鲂的判别性状。通过主成分分析法对可数性状(可量比例性状)构建了3个主成分,其贡献率分别为:26.28%(26.01%)、19.92%(12.05%)和8.04%(10.18%),累计贡献率54.24%(48.24%)。主成分散点图显示,4种鲂聚为4簇,广东鲂、团头鲂区分明显。     

团头鲂同源四倍体、倍间三倍体与二倍体红细胞的形态特征比较

通过比较同源四倍体、倍间三倍体与二倍体团头鲂（Megalobrama amblycephala）的红细胞、红细胞核的形态大小差异,探讨不同倍性团头鲂的红细胞形态遗传特征。结果表明：（1）团头鲂多倍体（同源4n和倍间3n）的红细胞数量显著低于二倍体（2n）团头鲂（P〈0．05）。其中,倍间三倍体团头鲂每毫升血液的红细胞数为二倍体的78．95％,而同源四倍体的红细胞数量下降幅度较大,仅为2n团头鲂的56．87％。（2）团头鲂同源四倍体、倍间三倍体的红细胞短径和长径、核短径和长径、红细胞表面积、红细胞体积和核体积均依倍性增加而显著增大（P〈0．05）;其中,又以核体积增大最为显著,同源四倍体、倍间三倍体的核体积分别为2n团头鲂的1．97倍和1．39倍。（3）团头鲂同源四倍体每毫升血液红细胞的总体积和总表面积,均明显低于二倍体和倍间三倍体团头鲂（P〈0．05）;倍间三倍体每毫升血液红细胞的总体积要多于二倍体团头鲂（P〈0．05）,但红细胞的总表面积在倍间三倍体与二倍体团头鲂间不存在显著差异（P〉0．05）。（4）在团头鲂同源四倍体中还观察到一定比例的异常红细胞现象。     

我国鲂属鱼类的研究进展

我国的鲂属鱼类有4种, 分别为团头鲂、鲂、广东鲂和厚颌鲂。从分类、形态、生态、遗传育种和增养殖等方面, 综述了国内鲂属鱼类的研究进展, 并就其资源保护与合理利用提出了建议。加强对厚颌鲂天然资源的保护和养殖开发; 鲂、广东鲂的大水面增养殖开发应逐步朝着规模化、产业化发展。指出了现代分子生物学技术在鱼类种质与资源保护研究、遗传育种等方面的广泛应用将成为渔业资源研究的主攻方向。     

植物甾醇对团头鲂生长、血脂和肝胰脏抗氧化功能的影响

选取体质量(74.52±1.03)g的团头鲂480尾,随机分成4组,每组4个重复,每个重复30尾,分别投喂添加0(对照组)、20mg/kg(试验Ⅰ组)、40mg/kg(试验Ⅱ组)和80mg/kg(试验Ⅲ组)植物甾醇的配合饲料,进行为期81d的饲养试验。试验结果表明,40、80mg/kg植物甾醇可提高团头鲂质量增加率及特定生长率(P0.05),其中40mg/kg组效果更佳,对肌肉粗蛋白含量影响不显著,对肌肉粗脂肪含量有一定提高(P0.05);添加40mg/kg植物甾醇显著降低了81d血浆低密度脂蛋白胆固醇水平(P0.05)。在本试验条件下,添加40mg/kg植物甾醇效果最佳。     

Expression of recombinant triangular bream (Megalobrama terminalis) pre-IGF-I in Escherichia coli

The insulin-like growth factor I (IGF-I) cDNA (GenBank Accession No. AY247412) of triangular bream (Megalobrama terminalis) was expressed for the first time in Escherichia coli. To construct the expression plasmid, the IGF-I cDNA was subcloned into prokaryotic-expressing vector pGEX-4T-1. The E.coli JM109 was transformed with the recombinant plasmid pGEX-4T-1-IGF-I, and the transgene expression was observed after being induced with isopropyl-β-D-thiogalactoside (IPTG). The results of SDS polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting indicated that the recombinant fusion protein had immune activity and the molecular weight was about 47 kDa. The results of SDS-PAGE and thin layer scanning showed that the yield of fusion protein had been enlarged with prolonging time. When the time of induced expression was 1, 2, 3, 4, 5, and 6 h, the expression amount was approximately 1.4, 4.3, 8.1, 11.3, 16.3 and 18.8% of total bacterial protein respectively.     

生物絮团对团头鲂(Megalobrama amblycephala)生长、消化酶和免疫相关酶活性的影响

为了研究零换水条件下团头鲂(Megalobrama amblycephala)养殖水体生物絮团形成所需的适合的碳氮比(C/N),以及不同C/N形成的生物絮团对团头鲂生长、消化酶活性和非特异性免疫力的影响,本实验设计4个不同C/N实验组,包括投喂基础饲料(C/N=8∶1)的对照组,在基础饲料上添加葡萄糖的处理组,其中将处理组的C/N分别调整为12∶1(C/N12)、16∶1(C/N16)和20∶1(C/N20).结果显示,C/N16和C/N20处理组中团头鲂的增重率和特定生长率显著高于对照组(P＜0.05),而饲料系数显著低于对照组(P＜0.05);C/N16和C/N20处理组中团头鲂肠道的蛋白酶活性和淀粉酶活性显著高于对照组(P＜0.05);而各实验组中团头鲂肠道的脂肪酶活性没有显著性差异;C/N16和C/N20处理组中团头鲂肝脏超氧化物歧化酶、碱性磷酸酶和溶菌酶活性显著高于对照组(P＜0.05).研究表明,生物絮团技术应用于团头鲂养殖适宜的C/N应不低于16,该条件下形成的生物絮团能有效提高团头鲂生长、消化酶和免疫相关酶活性.     

西江广东鲂的年龄鉴定及生长研究

利用鳞片、脊椎骨和背鳍条三种材料对肇庆自然保护区广东鲂(Megalobrama hoffmanni)的年轮特征进行了研究,并对广东鲂的生长情况进行分析。结果表明:1～4龄三种材料鉴定结果较吻合,5～7龄用脊椎骨鉴定较合适;广东鲂体重生长拐点年龄为4.7龄,5龄前后为合理的捕捞时期,渔获物中3、4龄鱼居多,说明目前捕捞强度过大,需要加强保护力度。     

Age,growth and age at sexual maturity of fan ray <Emphasis Type="Italic">Platyrhina sinensis</Emphasis> (Batoidea: Platyrhinidae) in Ariake Bay,Japan

Abstract:   Age, growth and sexual maturity of the fan ray Platyrhina sinensis in Ariake Bay, Japan were determined from specimens collected from May 2002 to September 2006. Age determination was conducted by vertebral centrum analysis using soft X-radiography. Annual band pair deposition was determined by marginal increment and edge analyses. The von Bertalanffy growth model best described the overall pattern of growth for both males and females (males L _∝  = 455.2, k  = 0.56, t ₀ = −1.09; females L _∝  = 555.8, k  = 0.28, t ₀ = −1.77; L _∝ is the theoretical asymptotic total length in mm, k is the growth rate coefficient and t ₀ is the theoretical time at zero length). Parameter estimates suggest that females attain a larger asymptotic total length and grow more slowly than males. The observed maximum ages were 5 years for males and 12 years for females. Age at 50% sexual maturity was 2.1 years for males and 2.9 years for females. The results indicate that this species is relatively fast-growing, short-lived and early maturing compared with many batoid species.     

Reproductive biology of <Emphasis Type="Italic">Sillago aeolus</Emphasis> in Okinawa Island,Japan

ABSTRACT:   A total of 414 fish (female, 59.3–275.0 mm and male, 61.0–220.0 mm standard length) were collected from December 2000 to March 2002 around Okinawa Island, Japan, for the determination of sex, spawning season, maturity and fecundity. Monthly changes in the gonadosomatic index (GSI) exhibited similar trends for both sexes and the mean GSI maintained a high level between February and May. Furthermore, the percentage frequency of hydrated oocytes and the spermatozoic activity suggested that main spawning occurred between February and May. Some hydrated oocytes were found throughout the year, with a GSI value greater than 1.0, suggesting that sporadic spawning occurred. Length at first maturity was determined for females and males as 120 and 113 mm standard length, respectively. Almost 50% and 100% males were matured at the end of their 0 and 1 year of age group, respectively. In contrast, no females were found to be mature at 0+ age group, and almost 60% of females were mature at 1+ age group. At ages over 2 years, all males and females were found to be mature. Batch fecundity (BF) of 33 females was related to standard length, and the relationship between standard length and BF was expressed by the exponential equation: BF = 269.5e^0.020954SL.     

热休克诱导马苏大麻哈鱼三倍体的初步研究

为探索马苏大麻哈鱼(Oncorhynchus masou)三倍体育种技术方法,更好地解决其个体小、生长慢和性成熟后死亡率高等问题,采用热休克法进行三倍体诱导实验,设4个诱导温度(24、26、28、30℃),2个起始诱导时间(15 min、20 min)和2个持续诱导时间(15 min、20 min)共分13个实验组和1个对照组。结果显示,13个实验组均能诱导出三倍体个体,而不同温度组的诱导率差异显著,分别为13.3%、31.65%、52.28%和78.81%(P<0.0.5)。随着温度的上升,孵化率呈显著降低的趋势。结果表明,温度是影响诱导成功的关键因素,利用热休克诱导受精卵制备陆封型马苏大麻哈鱼三倍体苗种的方法是可行的,三倍体诱导的最佳条件是:水温28℃,卵子受精后15 min持续处理20 min,发眼率(72.57±0.26)%,孵化率(60.92±0.31)%,三倍体率53.1%,综合诱导效果最佳。     

三角鲂形态特征和胰岛素样生长因子-Ⅰ基因的序列分析

对三角鲂(mEGALOBRAMA TERMINALIS)形态学特征进行研究，用RT—PCR的方法从三角鲂肝脏克隆了三角鲂胰岛素样生长因子-Ⅰ(IGF-Ⅰ)基因的cDNA序列。三角鲂传统的形态学数据与团头鲂相似。序列分析表明，三角鲂ICE-Ⅰ cDNA由486个核苷酸构成，编码161个氨基酸，包含整个信号肽、B、C、A、D和E区，与鲂属团头鲂比较，三角鲂与团头鲂IGF-Ⅰ cDNA序列同源性为99．8％，氨基酸序列同源性为99．4％。由此可见三角鲂的遗传学特征与团头鲂非常相似。     

团头鲂Toll样受体Ⅱ基因的克隆与表达分析

为了研究团头鲂(Megalobrama amblycephala)TLR2(ma TLR2)在抗嗜水气单胞菌(Aeromonas hydrophila)感染中的作用,本实验克隆了ma TLR2基因的c DNA全长。结果显示:ma TLR2基因c DNA的全长包括2923 bp,编码792个氨基酸。预测得到的ma TLR2的结构域包括一个信号肽、氨基端的亮氨酸重复基序(LRRs)、跨膜结构域(TM)和一个胞内的Toll/白介素(IL)-1受体区(TIR)。在嗜水气单胞菌感染后,团头鲂头肾中,TLR2的表达量在6 h时显著升高。TLR2下游相关的炎症细胞因子TNF-α的表达量也显著上调。结果表明ma TLR2在嗜水气单胞菌感染团头鲂后的免疫应答中起到了重要作用。     

珠江禁渔对广东鲂资源补充群体的影响分析

继我国各大水系实施禁渔期制度之后,珠江水系于2011年4月1日至6月1日实现首次禁渔。广东鲂是珠江中下游地区主要的经济鱼类之一,为分析珠江实施禁渔期制度对广东鲂资源补充群体的影响,于珠江实施禁渔制度前(2006—2010年)和禁渔制度后(2011—2012年)在珠江下游肇庆江段设立固定采样点,利用定量弶网对流经该江段的广东鲂鱼苗补充群体进行调查。结果显示,禁渔前,珠江广东鲂鱼苗集中出现在4月中下旬至10月中旬,持续时间为(189±11)d,高峰期为6—8月。禁渔期制度实施之后,全年广东鲂鱼苗出现的起始时间变化不大,但是结束时间提前,持续时间略有缩短,4—5月份广东鲂鱼苗密度明显增大。广东鲂鱼苗总量及其在鱼苗补充群体中的比例均有所提高。根据禁渔前广东鲂鱼苗发生量与径流量之间存在的回归关系:LgY=0.988Lnx-4.932(R2=0.365,P0.01),结合禁渔后实际调查结果,对禁渔的实际作用进行了估算,2011年和2012年由于禁渔分别增加了9.43×108和651.81×108尾广东鲂鱼苗。研究表明,在径流量有保障的前提下,目前的禁渔制度可以有效增加广东鲂鱼苗补充群体资源量。     

Molecular cloning of Insulin-like Growth Factor-I from triangular bream (Megalobrama terminalis)

Triangular bream (Megalobrama terminalis) IGF-I DNA and gene were cloned from triangular bream liver for the first time by RT-PCR. Sequence analysis indicated that the IGF-I cDNA consisted of 486 nucleotides encoding 117 amino acids which spanned the complete signal peptide, B, C, A, D and E domains. Analysis of the E domain indicated that triangular bream IGF-I belongs to the IGF-I Ea-2 subtype. Compared to bluntnose bream (Megalobrama amblycephala), another member of the same Megalobrama genus, triangular bream IGF-I shared 99.8% identity in cDNA sequence and 99.4% in predicted amino acid sequence. However, considerable differences were found in comparison to with common carp (Cyprinus carpio) and grass carp (Ctenopharyngodon idellus), which are members of the same family but of a different genus. This revised version was published online in July 2006 with corrections to the Cover Date.     

游泳加速模式对南方鲇和团头鲂运动后代谢恢复的影响

为了探讨游泳加速模式对不同生态习性鱼类运动力竭后代谢恢复的影响,采用鱼类游泳呼吸测量仪,在(25±0.5)℃条件下,分别测定南方鲇(Silurus meridionalis)和团头鲂(Megalobrama amblycephala)爆发游泳加速模式(Uburst:Δv为20 cm/s,Δt为2 min)和持续游泳加速模式(Ucrit:Δv为10 cm/s,Δt分别为20、40和60 min)的运动后过量耗氧(EPOC)。结果显示:两种实验鱼的代谢恢复曲线均呈快速恢复和缓慢恢复两个阶段。南方鲇在Uburst后测得的EPOC恢复历时显著高于其它3个加速模式,而团头鲂4个不同处理组的EPOC恢复历时之间的差异均不显著;在相同的加速模式条件下,南方鲇的EPOC恢复历时均短于团头鲂。南方鲇在Uburst后的EPOC总量比3组Ucrit模式下的EPOC总量分别高286.6%、359.5%和816.5%,而团头鲂分别为20.6%、14.8%和29.0%。结果表明:南方鲇运动中对无氧代谢的依赖度高,爆发运动时动用无氧代谢的能力强,可以大幅度提升游泳速度,且运动后代谢恢复时间较短;团头鲂运动中主要依赖有氧代谢,可以保持较长时间的高速游泳,但运动后代谢恢复历时较长。     

Isolation,identification and character analysis of Streptococcus dysgalactiae from Megalobrama terminalis

Pure bacterial cultures were isolated from different tissues of moribund Megalobrama terminalis from a high mortality event that occurred at a farm in Foshan, China. Two isolates (F2 and F3) were identified as Streptococcus dysgalactiae subsp. dysgalactiae based on morphological and biochemical detection as well as molecular analysis. In brain heart infusion broth, the best growth conditions of isolate F3 were 35ºC, salinity 5‰ and pH 7. Furthermore, infection with isolate F3 (1.2 × 10⁶ CFU/fish) led to the death of M. terminalis and zebrafish (Danio rerio). However, isolate F3 had no obvious pathogenicity to tilapia (GIFT, Oreochromis niloticus). When the water temperature was 29ºC, the corresponding mortality rates for zebrafish infected by isolate F3 were higher than those at 23ºC. Culture for 24 and 72 hr with isolate F3 resulted in the same mortality rates for zebrafish. The antimicrobial susceptibility assay revealed that isolate F3 was susceptible to ampicillin, florfenicol and several other antibiotics but resistant to nalidixic acid, streptomycin, sulfamethoxazole/trimethoprim, neomycin and amikacin. To our knowledge, this is the first report that S. dysgalactiae infected the subtropical freshwater fish M. terminalis, which indicates that this bacterium is a potential threat to subtropical freshwater fish.