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81.
利用蛋白质含量不同的6个亲本的不完全双列杂交的F1,F2代资料,分析了蛋白质含量的遗传变异趋势及与其他性状间的相互关系。结果表明,双亲的蛋白质含量差异大,F2变异程度也大。蛋白质含量的遗传力较高,可在F2代选择并能获得一定的遗传进度,F1,F2代的蛋白地岑与母本的含量及双亲中亲值呈极显著的正相关。F2代的蛋白质含量与百粒重呈极显著的正相关,与脂肪含量呈极著的负相关。  相似文献   
82.
Abstract – The morphologies of sympatric juvenile Atlantic salmon Salmo salar parr and brown trout Salmo trutta parr were compared between Irish rivers with contrasting hydraulic environments – a high‐gradient and a low‐gradient tributary from the River Barrow catchment, south‐east Ireland and a high‐gradient river from the Burrishoole catchment, west of Ireland. The two catchments differ markedly in mean annual precipitation (849.0 mm year?1 and 1370.3 mm year?1 for the Barrow and Burrishoole catchments, respectively). Parr of both species demonstrated morphological variation between and within catchments. Changes in metrics such as pectoral fin length, body depth and body length between and within catchments suggest that hydraulic forces were a major determinant of morphological variation. Both species from the Burrishoole catchment had relatively larger pectoral fins, longer heads, larger eyes and shallower bodies than conspecifics from the Barrow catchment. In rivers subject to frequent rainfall‐driven high discharges, such as those in the Burrishoole catchment, a more fusiform body and head shape coupled with larger pectoral fins may reduce the energetic cost of maintaining position in the water column, as well as increase stability and manoeuvrability. The larger eyes in both parr species in the Burrishoole catchment could further be a response to the lower visibility of the more turbid and peat‐stained waters or to the reduced prey availability. The results of this study demonstrate that local adaptation to flow conditions can yield morphologically distinct populations and that multiple species can exhibit parallel phenotypic responses to changing environmental conditions.  相似文献   
83.
火炬松材性变异规律的初步研究   总被引:4,自引:0,他引:4  
宋云民  黄永利 《林业科学》1995,31(4):346-352
对生长于广西南宁地区相同环境下来自美国的18个种源10年生火炬松的材性进行了研究。包括:材笥的种源变异。材性的地理变异模式及其与原产地气候因子的相互关系,材性因子间及其与生长因子、形态因子的相关分析。  相似文献   
84.
Hypothalamic dopamine (DA), noradrenaline (NA) and 5-hydroxytryptamine (5-HT) levels exhibited marked day-night variations under ambient photoperiod and temperature (12L12D; 17±1°C) with peak values at mid-light phase. The 16L8D; 22±1°C treatment reversed the diurnal rhythm of 5-HT, but not that of DA and NA. However, there was an overall increase in the levels of the catecholamines on exposure to the long photoperiod and high temperature. The administration of melatonin in the fish held on 16L8D; 22±1°C regime restored the 5-HT rhythm to that of the 12L12D; 17±1°C control group, but with elevated mid-photophase value. However, there was no effect of the indole treatment on the 5-HT rhythm under the 12L12D; 17±1°C regime. Melatonin causes a significant reduction of NA level in both the groups, while DA level did not change in either group.  相似文献   
85.
黄海中部小黄鱼摄食习性的体长变化与昼夜变化   总被引:7,自引:2,他引:7  
根据2001年3月至2002年1月在黄海中部海域进行的4个季节的定点底拖网调查,应用聚类分析、单因素方差分析和列联表检验等方法,对小黄鱼(PseudosciaenapolyactisBleeker)摄食的体长和昼夜变化进行研究。结果表明:摄食强度没有明显的体长变化,而食物组成却有明显的体长变化。随着体长的增大,鱼类和虾类的比例有所增加,而磷虾类、桡足类和端足类的比例则减少。饵料生境宽度在体长大于109mm后有明显的增加。经检验,小黄鱼平均每个胃中含有的饵料个数显著减少而饵料重量则增加,这符合"最佳摄食理论"。聚类分析的结果表明,小黄鱼在体长达到109mm时,出现了明显的食物转换现象。小黄鱼的摄食强度在各个季节都有明显的昼夜变化,午夜24:00和早晨08:00是2个摄食高峰期。  相似文献   
86.
We examined the interannual variation in Neocalanus copepod biomass in the Oyashio waters in spring and summer from 1972 to 1999. In the mid‐1970s, mesozooplankton biomass in spring was high; however, it decreased significantly in the late 1970s. The timing of the decrease in mesozooplankton biomass corresponded to the 1976/77 climatic regime shift. The biomass of N. flemingeri, which dominated the Neocalanus community, was roughly constant from 1980 to 1999. Although species‐level estimates of Neocalanus biomass were not available for the 1970s, a previous study reported that Neocalanus copepods were the predominant mesozooplankton in the Oyashio waters in spring during the 1970s. Neocalanus copepods dominated the mesozooplankton community throughout the 1970s, and their biomass decreased in the late 1970s. Springtime net community production, an index of new production, also decreased in the late 1970s. We suggest that the reduction in new production negatively affected Neocalanus food availability, resulting decreased copepod biomass. New production may have been limited by a combination of subsurface iron supplies, increased vertical density gradient, and reduced vertical water mixing in winter, which resulted in diminished iron entrainment in winter. In summer, mesozooplankton biomass significantly decreased and increased synchronously with the 1976/77 and 1988/89 climatic regime shifts. The biomass of N. plumchrus, which dominated the Neocalanus community, was low in the 1980s and increased in the early 1990s. The biomass of the second‐most dominant copepod, N. cristatus, also increased in the early 1990s. Neocalanus copepods were reported to be a dominant component of the mesozooplankton community in the 1970s; Neocalanus biomass was high in the mid‐1970s and decreased in the late 1970s. Japanese sardine (Sardinops melanostictus), an important predator of Neocalanus copepods, exhibited interannual variation in standing stock that was inversely related to mesozooplankton biomass. At their peak in 1984, sardines consumed 32–138% of the daily Neocalanus production during summer. Therefore, predation pressure on Neocalanus by Japanese sardine is likely to affect interannual variation in mesozooplankton biomass during the summer.  相似文献   
87.
Giant freshwater prawn (GFP; Macrobrachium rosenbergii) aquaculture has expanded rapidly since 1990. Most local culture industries, however, have developed in an unsystematic way. Fiji has a small culture industry producing the ‘Anuenue’ strain; however, performance of this strain has never been systematically evaluated. Recently, some Fijian farmers have reported declines in stock productivity. The current project evaluated the relative performance of three exotic strains with different genetic backgrounds from Malaysia, Indonesia and Vietnam, against the ‘local’ strain in Fiji in a 4 × 3 replicated pond trial experiment. A total of 5827 prawns were harvested after 143 days growout. Individual growth rate and relative survival of the Fiji strain were not statistically different from any of the introduced strains, but Vietnam strain was superior to that of the Malaysia strain. Genetic diversity showed significant differences in variability among strains, with the Malaysian strain displaying the lowest genetic diversity. Indonesia strain showed that females were reaching maturation earlier than other strains and were smaller in size. This study suggests that Malaysian and Indonesian strains would constitute a poor choice for Fiji, whereas the Vietnam strain consistently performed well on all criteria measured. High variation among replicate ponds within strains unfortunately confounded among‐strain variation.  相似文献   
88.
渤海封闭性强,水动力条件和自净能力较弱,其生态系统较为敏感和脆弱。2011年位于渤海中部的蓬莱19-3油田发生重大溢油事故,对渔业生态环境和渔业资源造成了严重影响。为了解和掌握该起溢油污染事故发生后渔业生态环境的变化状况,分别于2012?2014年在渤海中部海域进行了9个航次的生态环境跟踪调查。利用其中部分调查资料,作者对渤海中部活性磷酸盐的时空变化特征及其影响因素进行了分析探讨。结果显示,(1)2012?2014年春季和夏季渤海中部海域活性磷酸盐含量符合第二类海水水质标准要求,秋、冬季部分海域已受到活性磷酸盐的污染。(2)不同季节渤海中部海域活性磷酸盐的平面分布趋势各异,垂直分布也存在季节差异。春季和夏季活性磷酸盐呈现由表层至底层递减的趋势,秋季和冬季接近呈垂直分布均匀状态。(3)渤海中部海域活性磷酸盐平均含量季节变化明显,其含量顺序由高到低依次为冬季、秋季、春季、夏季,冬季明显高于夏季。2014年渤海中部海域活性磷酸盐含量低于2013年,呈逐年降低趋势。(4)渤海中部海域活性磷酸盐时空变化受到诸多因素的影响,营养盐的外源补充、内源再生和生物消耗是影响活性磷酸盐时空变化的最重要因素。  相似文献   
89.
本文报道了辽宁省瓦房店市邓屯乡高家养虾场对虾养成期虾池水体和底质及虾体异养菌和弧菌含量的变化。结果表明外海水中异养菌数量为10 ̄4~10 ̄5个/毫升,弧菌数量为10 ̄2~10 ̄3个/毫升,虾池水中异养菌数量为10 ̄4~10 ̄5个/毫升,弧菌数量为10 ̄2~10 ̄4个/毫升,底质中异养菌数量为10 ̄5~10 ̄7个/克,弧菌数量为10 ̄3~10 ̄4个/克。虾体肌肉中异养菌数量为10 ̄3~10 ̄5个/克,弧菌数量为10 ̄3~10 ̄5个/克;肝胰脏中异养菌数量为10 ̄3~10 ̄7个/克,弧菌数量为10 ̄2~10 ̄7个/克;肠道中异养菌数量为10 ̄6~10 ̄7个/克,弧菌数量为10 ̄6~10 ̄7个/克。  相似文献   
90.
A cycle of fluctuation in the Far Eastern sardine, Sardinops sagax, population is accompanied by an abrupt drop and recovery of fish size and lipid content of parent fish, which may reflect a phase variation from coastal to oceanic and its reverse. The cycle begins with the survival success of a smaller number of eggs produced by high-quality parents, which is triggered by a global climate change (density-independent process), and finally ends in the survival failure resulting from an overexpansion of an enormous number of fish produced by low-quality parents (density-dependent process).  相似文献   
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