不同来源黄鳝(Monopterus albus)繁殖力的比较分析

比较不同来源黄鳝(Monopterus albus)的个体繁殖力,研究了其个体繁殖力分布特征、变化规律及与生物学指标的关系.以怀卵量作为绝对繁殖力的表征参数,对雌性黄鳝进行解剖测定.结果显示,野生黄鳝绝对繁殖力(F)为181-729粒,人工培养黄鳝F值为165-589粒,人工繁育黄鳝F值为135-352粒;野生黄鳝基于体重的相对繁殖力(FW)为5.4-11.8粒/g,人工培养黄鳝FW为3.5-9.3粒/g,人工繁育黄鳝FW为4.96-8.55粒/g;野生黄鳝基于体长的相对繁殖力(FL)为5.8-17.2粒/mm,人工培养黄鳝FL为4.85-15.00粒/mm,人工繁育黄鳝FL为4.35-9.03粒/mm,不同来源黄鳝在F、FL、FW上均有极显著差异(P＜0.01).来源和体色均不同的黄鳝其F和FL均具有极显著差异,而FW差异不显著;所有黄鳝的F和野生黄鳝的FL与体长、体重生物学指标密切相关,其余F、FL和FW与各生物学指标均相关性较小.研究表明,野生黄鳝的F、FL和FW均高于人工培养和人工繁育的黄鳝,怀卵量优势明显.     

不同投喂水平对刺参(Apostichopus japonicus Selenka)生长、消化酶及免疫相关酶活性的影响

试验研究了饥饿、次饱食、饱食和过饱食4个不同投喂水平(即2％、3％、4％和5％体重)对刺参[初始体重为(5.80±0.02)g]生长性能、体成分、消化性能以及刺参体壁与体腔液内超氧化物歧化酶(SOD)、碱性磷酸酶(AKP)和溶菌酶(LZM)活性的影响.试验在室内静水养殖系统中进行,试验水温为19-21℃,为期60 d.结果显示,在次饱食水平下,刺参特定生长率达到最高,显著高于饥饿水平和过饱食水平(P＜0.05),但与饱食水平差异不显著(P＞0.05);刺参肠道胰蛋白酶活性均随着投喂水平的提高而升高,在过饱食水平下达到最高,显著高于饥饿水平和次饱食水平(P＜0.05),但与饱食水平差异不显著(P＞0.05);刺参肠道淀粉酶活性随着投喂水平的提高呈现先下降后保持稳定的趋势,在饱食水平之后达到稳定;在饱食水平下,刺参体壁和体腔液AKP、SOD及LZM活性均表现出较高水平,表明在饱食投喂水平下,刺参抗病能力最强;不同投喂水平对刺参体壁营养组成以及刺参脏壁比均无显著影响(P＞0.05).因此,建议刺参养殖采用饱食水平进行投喂.     

维生素D3对仿刺参幼参生长、体组成及 抗氧化能力的影响

为研究维生素D3对仿刺参(Apostichopus japonicus)幼参生长、体组成及抗氧化能力的影响,在基础饲料中分别添加0(D1)、250(D2)、500(D3)、1000(D4)、2000(D5)、3000(D6) IU/kg的维生素D3(实测值：95、334、570、1076、2063、3081 IU/kg),制作6组等氮等能的实验饲料,饲喂初始体重为(15.43±0.14) g仿刺参幼参56 d。结果显示,1) 维生素D3对仿刺参存活率(SR)无显著影响(P>0.05),显著提高了增重率(WGR)和特定生长率(SGR),D1组均显著低于其他组(P<0.05);D3、D4、D5组肠体比(IWR)显著高于其他3组(P<0.05),但3组之间差异不显著(P>0.05)。2) 维生素D3对体壁水分、粗蛋白和粗脂肪含量无显著影响(P>0.05);粗灰分含量随添加量的增加呈先升后降趋势,D5组达到最高值;羟脯氨酸含量呈先下降后上升趋势,D4组达到最低值;维生素D3显著提高了体壁Ca含量(P<0.05);体壁维生素D3的沉积量呈先上升后下降趋势,D4组达到最高值,显著高于其他组(P<0.05)。P含量呈先上升后平稳趋势;Mg含量呈上升趋势,D1组显著低于其他组(P<0.05);Fe含量呈先升后降趋势,D5、D6组显著低于其他组(P<0.05);Mn含量呈下降趋势,但各组间差异不显著(P>0.05)。3) 随着维生素D3添加量的增加,肠道碱性磷酸酶(AKP)及总超氧化物歧化酶(T-SOD)活力呈先上升后下降趋势,丙二醛(MDA)含量呈下降趋势,各组间总抗氧化能力(T-AOC)及过氧化氢酶(CAT)活力均无显著性差异(P>0.05)。研究表明,以增重率为评价指标,一元二次线性回归分析表明,初始体重为15.43 g的仿刺参对维生素D3的最适需求量为1587.5 IU/kg。     

饲料蛋白水平对方格星虫稚虫生长和体组成的影响

以初始体重为39.20±0.24mg的方格星虫稚虫为实验对象,分别饲喂蛋白水平为25.21%、29.87%、35.03%、40.67%、45.47%、50.12%、55.29%、60.38%、64.85%的9种等能微颗粒饲料56d,研究饲料蛋白水平对方格星虫稚虫生长和体组成的影响。结果表明,饲料蛋白水平对方格星虫稚虫的生长性能有显著影响(P<0.05)。随着饲料中蛋白水平的提高,稚星虫的增重率和特定生长率都呈先增后降的趋势,当饲料蛋白水平为45.47%时,稚星虫增重率和特定生长率均达到最大值,二次曲线回归分析确定当增重率达到极值时,饲料蛋白水平为46.79%;对稚星虫体组成成分的分析表明,饲料蛋白水平对方格星虫稚虫体组成中脂肪和蛋白质的含量影响显著(P<0.05),稚星虫体蛋白含量随着饲料蛋白水平的上升有显著升高的趋势,64.85%组稚星虫体蛋白含量最高,显著高于其他各蛋白水平组(P<0.05)。体脂肪含量随着饲料蛋白水平的上升有降低的趋势,64.85%组稚星虫的体脂肪含量最低,显著低于25.21%、29.87%、35.03%和40.67%组(P<0.05)。饲料蛋白水平对稚星虫体灰分含量没有显著影响(P>0.05)。以增重率为评价指标时,方格星虫稚虫对饲料中蛋白的适宜需求量为46.79%。     

大菱鲆选育家系体重性状的分形特征

分析了2007～2010年度18月龄体重性状的信息维数和关联维数。分析结果显示,2007～2010年度所构建的大菱鲆选育家系群体18月龄体重性状的信息维数介于0．9422～0．9586之间,不同年度之间的信息雏数变异不显著,这说明不同年度各选育家系群体18月龄体重性状的信息维数均为较大值,所统计群体的遗传变异都十分丰富,统计性状的变异范围也较大,显示出良好的育种潜力。相应数据的关联维数分析结果表明,除2008年度小尺度范围的关联维数是0．4284外,其余各小尺度范围的关联维数均高于0．73,这表明,从分析结果的总体来看,大菱鲆各选育家系群体内个体间的遗传结构的相关性较高;信息维数和关联维数作为研究分形特征的指标,从两个角度阐明了选育性状遗传结构的分形特征,在实际的良种选育过程中,应考虑这两方面的因素,确定适当的留种率。     

Density-dependent growth of young-of-the-year Atlantic salmon (Salmo salar) revisited

Imre I, Grant JWA, Cunjak RA. Density-dependent growth of young-of-the-year Atlantic salmon ( Salmo salar ) revisited. Ecology of Freshwater Fish 2010: 19: 1–6. © 2009 John Wiley & Sons A/S
Abstract –  The length of individual young-of-the-year (YOY) Atlantic salmon ( Salmo salar ) in Catamaran Brook decreases with increasing population density following a negative power curve. Because most of this decrease in growth rate occurs at low densities (<1 fish·m⁻²), ( Imre et al. 2005 ; Journal of Animal Ecology, 74: 508–516) suggested that exploitation competition for drifting prey rather than space limitation might be responsible for this pattern. Recently, ( Ward et al. 2007 ; Journal of Animal Ecology, 76: 135–138) showed that the negative power curve of growth rate versus density can be caused by other mechanisms and suggested that Imre et al.'s evidence for density-dependent growth would have been stronger if we had analysed final size versus initial density rather than final density. We examined (i) whether the negative power curve of size versus density was also apparent in an analysis of final size versus initial density and tested two predictions that emerge from Ward et al.'s model, (ii) the variance in body size increases with population density, and (iii) the maximum fish size at a site is density-independent. The final size of YOY salmon decreased with increasing initial density following a negative power curve. Our data did not provide strong support for the above predictions emerging from Ward et al.'s model. Our analyses of different years, sites and seasons were consistent with the hypothesis of density-dependent growth of YOY salmon.     

Exploitation of walleye in a Great Plains reservoir: harvest patterns and management scenarios

Abstract This study assessed exploitation and evaluated management options for walleye, Sander vitreus (Mitchill), in Glen Elder Reservoir, Kansas. A total of 2429 walleye varying from 240 to 687 mm was tagged with Carlin dangler tags during 2000–2003. After correcting for tag loss and non‐reporting, exploitation of walleye was estimated as 68.3%. More than 85% of the tagged walleye were harvested during April to June and 75% were harvested within 6 months after tagging. A Beverton‐Holt yield‐per‐recruit model was used to evaluate six minimum length limits varying from 250 to 610 mm. Given current exploitation rates, population demographics and harvest regulations (381‐mm minimum length limit), the walleye population is probably experiencing recruitment overfishing. Model results suggested that a 610‐mm minimum length limit would be required to prevent growth overfishing and a 533‐mm or longer minimum length limit would prevent recruitment overfishing.     

Maize–legume intercropping promote N uptake through changing the root spatial distribution,legume nodulation capacity,and soil N availability

Legume cultivars affect N uptake, component crop growth, and soil physical and chemical characteristics in maize–legume intercropping systems. However, how belowground interactions mediate root growth, N fixation, and nodulation of different legumes to affect N uptake is still unclear. Hence, a two-year experiment was conducted with five planting patterns, i.e., maize–soybean strip intercropping (IMS), maize–peanut strip intercropping (IMP), and corresponding monocultures (monoculture maize (MM), monoculture soybean (MS), and monoculture peanut (MP)), and two N application rates, i.e., no N fertilizer (N–) and conventional N fertilizer (N+), to examine relationships between N uptake and root distribution of crops, legume nodulation and soil N availability. Results showed that the averaged N uptake per unit area of intercrops was significantly lower than the corresponding monocultures. Compared with the monoculture system, the N uptake of the intercropping systems increased by 31.7–45.4% in IMS and by 7.4–12.2% in IMP, respectively. The N uptake per plant of intercropped maize and soybean significantly increased by 61.6 and 31.8%, and that of intercropped peanuts significantly decreased by 46.6% compared with the corresponding monocultures. Maize and soybean showed asymmetrical distribution of roots in strip intercropping systems. The root length density (RLD) and root surface area density (RSAD) of intercropped maize and soybean were significantly greater than that of the corresponding monocultures. The roots of intercropped peanuts were confined, which resulted in decreased RLD and RSAD compared with the monoculture. The nodule number and nodule fresh weight of soybean were significantly greater in IMS than in MS, and those of peanut were significantly lower in IMP than in MP. The soil protease, urease, and nitrate reductase activities of maize and soybean were significantly greater in IMS and IMP than in the corresponding monoculture, while the enzyme activities of peanut were significantly lower in IMP than in MP. The soil available N of maize and soybean was significantly greater increased in IMS and IMP than in the corresponding monocultures, while that of IMP was significantly lower than in MP. In summary, the IMS system was more beneficial to N uptake than the IMP system. The intercropping of maize and legumes can promote the N uptake of maize, thus reducing the need for N application and improving agricultural sustainability.     

Changes in DNA methylation patterns affect ripening time in Satsuma mandarin fruit

Differences in DNA methylation patterns might lead to differences in fruit maturation time in the citrus Satsuma, but the underlying mechanism is unclear. Here, we explored the differences in methylation patterns during fruit ripening in Satsuma among 20 early‐ and late‐maturing Satsuma varieties and compared DNA methylation patterns in two Satsuma cultivars (Ooita wase and Aoshima unshiu) at different developmental stages using methylation‐sensitive fragment length polymorphism (MSAP) analysis. We cloned and sequenced DNA from different bands to identify differentially methylated genes involved in fruit ripening. The internal methylation of CCGG sequences occurred more frequently in the early‐maturing Satsuma cultivars (8.47%) than the late‐maturing cultivars (6.74%), whereas the external methylation of CCGG sequences occurred less frequently in the early‐maturing cultivars (24.98%) compared to the late‐maturing types (27.27%). Genes encoding the G protein α subunit and zinc‐binding protein of the histidine triad (HIT) family and two unknown genes homologous to expressed sequence tag (EST) sequences (CX052976.1 and CX071135.1) were found to be modified by methylation during the fruit ripening process. These findings suggest that DNA methylation might play important roles in regulating fruit ripening in Satsuma. Our results lay the foundation for analysing the molecular mechanism underlying fruit ripening in this important citrus crop.     

特定土壤条件下“新温185”核桃根施氮磷钾肥细根根长密度效应研究

以"新温185"核桃(Juglans regia'Xinwen185')为试验材料,通过"3414"肥料效应田间试验,采用根钻取样法和图像扫描分析法,研究了特定土壤养分条件下根施氮(N)、磷(P)、钾(K)肥对"新温185"核桃细根根长密度的影响,以期为"新温185"核桃土壤养分的科学管理提供依据。结果表明:"新温185"核桃细根根长密度(C)的正平方根(Sqrt C)同P肥与K肥的交互作用(P×K)、N肥的施用量(纯氮量,N)、N肥施用量的自乘(N^2)存在极显著(P=0.000)的线性相关关系,即■。特定土壤条件下(碱解N 77.7 mg·kg^-1,有效P 14.3 mg·kg^-1,速效K 77.3 mg·kg^-1),根施P、K肥对核桃的细根根长密度效应不显著,P、K肥的交互作用对细根根长密度存在负效应,当N肥施用量(纯量)小于1.34 kg·株^-1时,对"新温185"核桃细根根长密度存在正效应,反之则存在负效应。