共查询到20条相似文献，搜索用时 359 毫秒
1.
杨柳科植物染色体数目及其进化的研究(英文) 总被引：1，自引：0，他引：1
本文报道了8种3变种2杂交种杨树的染色体数目,结果均为2n=38,其中3种1杂交种为首次报道。统计了277种杨柳科植物的染色体数目,分析了其可能的进化途径,初步结论如下:(1)现代杨柳科植物是一群具有多个染色体基数、处在不同倍性水平的多倍体系列;(2)其次生基数X_2=19,11,12和14,这些次生基数可能是古多倍体起源的;(3)杨柳科植物染色体的原始基数可能是X=6;(4)现代杨属和钻天柳属植物染色体数目的进化处在同一水平上,即古多倍体水平上;而柳属中大约50％的种进化为次生多倍体,最高为16倍体。绘出了杨柳科植物染色体进化谱,讨论了该科植物染色体基数进化的可能途径。 相似文献
2.
本文报道了8种3变种2杂交种杨树的染色体数目,结果均为2n=38,其中3种1杂交种为首次报道。统计了277种杨柳科植物的染色体数目,分析了其可能的进化途径,初步结论如下:(1)现代杨柳科植物是一群具有多个染色体基数、处在不同倍性水平的多倍体系列;(2)其次生基数X_2=19,11,12和14,这些次生基数可能是古多倍体起源的;(3)杨柳科植物染色体的原始基数可能是X=6;(4)现代杨属和钻天柳属植物染色体数目的进化处在同一水平上,即古多倍体水平上;而柳属中大约50％的种进化为次生多倍体,最高为16倍体。绘出了杨柳科植物染色体进化谱,讨论了该科植物染色体基数进化的可能途径。 相似文献
3.
2种双壳贝类染色体的观察研究 总被引：1，自引：0，他引：1
[目的]为贝类的细胞遗传学研究提供基础资料。[方法]以等边浅蛤和江户布目蛤的鳃组织为研究材料,用植物血球凝集素和秋水仙素对2种双壳贝类的腮组织进行处理后,采用滴片-空气干燥法制片并观察其染色体数目。[结果]通过观察2种贝类的中期分裂相,发现等边浅蛤的染色体众数为36的分裂相细胞,占全部计数细胞的55.0%,说明其染色体数目(2n)为36。而江户布目蛤的染色体众数为30的分裂相细胞,占全部计数细胞的58.8%,说明江户布目蛤的染色体数目(2n)为30。[结论]从细胞水平上看,日本镜蛤(2n=30)和江户布目蛤有较亲密的亲缘关系,而青蛤(2n=36)和等边浅蛤也有较亲密的亲缘关系。 相似文献
4.
5.
6.
中国苹果属(Malus)植物的核型比较研究 总被引：2，自引：0，他引：2
梁国鲁 《西南大学学报(自然科学版)》1986,(1)
本文采用去壁低渗法对原产于我国的苹果属31个种类(包括19个种)以及近缘属——梨属中川梨进行核型的初步研究。表明:除昭觉红花(Malus sp.)外,全部核型均由中部着丝点染色体(m)和近中部着丝点染色体(sm)组成,其染色体长度均属小染色体范畴。此外,还对上述种类核型的进化趋势进行了讨论。 相似文献
7.
关于六倍体普通小麦的起源,过去通常归结于通过远缘杂交和多倍体的进化。但这种进化模式无法解释每个种内存在的遗传多样性。 进入八十年代后,Ｇｒａｎｔ（1 981 ）提出了重组型物种形成的理论框架,为小麦的起源研究指出了一个重要的方向。研究表明,在小麦进化过程中,不仅通过染色体组内的转化和染色体组间的互换,而且由于遗传渐渗和杂化基因（节段）染色体组的形成,促使多倍体小麦种的染色体发生了改变。但到目前为止还缺少有关新染色体组形成的报道。 过去我们已经报道了偏凸山羊草与硬粒小麦双二倍体杂交的遗传不稳定性,指… 相似文献
8.
【目的】对尖裸鲤（Oxygymnocypris stewartii）的染色体核型进行分析,为其进化生物学、种质标准制定及杂交育种亲本选择提供细胞遗传学依据。【方法】以西藏自治区农牧科学院水产科学研究所和中国水产科学研究院黑龙江水产研究所联合驯养的尖裸鲤为试验对象,取其头肾采用冷滴片法制备染色体标本,PI染色,荧光显微镜下拍照,使用Photoshop和曲线测量工具E ruler对染色体进行测量和配对,获得染色体核型,并与已报道的19种（或亚种）裂腹鱼亚科鱼类的中部着丝粒染色体（m）+亚中部着丝粒染色体（sm）和亚端部着丝粒染色体（st）+端部着丝粒染色体（t）的数量比进行比对,分析尖裸鲤的进化地位。【结果】尖裸鲤染色体数目为2n=92,核型公式为26m+28sm+20st+18t,臂数（NF）=146,进化地位在裂腹鱼亚科中处于中等水平。【结论】明确了尖裸鲤的染色体核型和进化地位,其特化程度为高度特化等级。 相似文献
9.
10.
对长筒石蒜C-带进行了初步研究,研究表明其染色体2 n=16。对于M型染色体,带纹主要以末端带为主;而对于T型染色体,主要出现了着丝粒带纹,同时也出现了随体带。同时,对于石蒜属染色体可能的进化方式进行了探讨。 相似文献
11.
Stable isotopic and shell-growth banding studies of the symbiont-bearing giant clam Tridacna maxima reveal the existence of two growth phases related to sexual maturity that can be discerned in the shells of extinct and extant mollusks. The changeover from the first to second growth phase at an age of approximately 10 years is accompanied by a decrease in rate of calcification and suggests a reordering of energy priorities between biomineralization and reproduction. The carbon-13 to carbon-12 ratio of Tridacna maxima is systematically depleted relative to symbiont-barren mollusks, making it possible to determine the importance of algal-molluscan symbiosis to the functional morphology and paleoecology of mollusks in the geologic record. 相似文献
12.
Four Paleozoic bivalved genera are assigned to the new molluscan class Rostroconchia: Eopteria, Euchasma, Conocardium, and Pseudoconocardium. These mollusks have ani uncoiled univalved larval shell; an untorted bivalved adult shell; no hinge teeth, ligament, or adductor muscles; and a fused, almost inflexible. hinge. Rostroconchianis developed separately from the pelecypods through the ribeirioids, but are regarded as more closely related to the Pelecypoda and Scaphopoda than to other known classes of mollusks. 相似文献
13.
M Stuiver 《Science (New York, N.Y.)》1968,162(857):994-997
Freshwater lake marl and mollusks from Indiana show variations in ratios of oxygen-18 to oxygen-16 of a few per mil during the Postglacial. For the last 9000 years these variations are about 1 per mil for properly selected lake sediments. Thus the oxygen isotope composition of atmospheric precipitation appears relatively stable over this interval, indicating stationary atmospheric circulation patterns over the Great Lakes region. A reduction in oxygen-18 content around 10,000 years ago corresponds with the climate change indicated by pollen profiles. Large systematic differences were found between carbon-13 and oxygen-18 content of marl and mollusks. 相似文献
14.
The origin and possible antiquity of faunas at deep-sea hydrothermal vents and seeps have been debated since their discovery. We used the fossil record of seep mollusks to show that the living seep genera have significantly longer geologic ranges than the marine mollusks in general, but have ranges similar to those of deep-sea taxa, suggesting that seep faunas may be shaped by the factors that drive the evolution of life in the deep sea in general. Our data indicate that deep-sea anoxic/dysoxic events did not affect seep faunas, casting doubt on the suggested anoxic nature and/or global extent of these events. 相似文献
15.
海南热带兰花设施栽培中有害软体动物种类的调查 总被引：2，自引：1，他引：1
软体动物的危害已成为制约热带兰花设施生产的主要因素之一。笔者在海南的海口市、琼中县、三亚市各选若干兰园,对设施兰园内和兰园周边地带中存在的有害软体动物进行了调查,现已发现5种蜗牛,分别是褐云玛瑙螺[Achatina fulica（Bowdich,1822）],东方琥珀螺[Succinea orientalis（Benson,1851）],中华小囊螺[Microcystina sinica（Moellendorff,1885）],红粉缘尖巴蜗牛[Acusta tourannensis rhodostoma（Moellen-dorff,1884）]以及平齿坚螺[Camena platydon（Pfeiffer,1845））。另外发现2种蛞蝓,其中一种为双线嗜粘液蛞蝓[Meghimatium bilineatum（Benson,1842）];另一种在海南极为罕见,仅收到唯一一份活体标本,已死亡而尚未作物种鉴定。根据调查结果分析了各种有害软体动物对热带兰花设施生产的危害的轻重程度,并提出了相关的防除建议。 相似文献
16.
Phosphorite concretions have been detected in the kidneys of two widespread species of mollusks, Mercenaria mercenaria and Argopecten irradians, which have relatively high population densities. These concretions are the first documentation of the direct biogenic formation of phosphorite grains. The concretions are principally amorphous calcium phosphate, which upon being heated yields an x-ray diffraction pattern which is essentially that of chlorapatite. These concretions appear to be a normal formation of the excretory process of mollusks under reproductive, environmental, or pollutant-induced stress. Biogenic production of phosphorite concretions over long periods of time and diagenetic change from amorphous to crystalline structure, coupled with secondary enrichment, may account for the formation of some marine phosphorite desposits which are not easily explained by the chemical precipitation-replacement hypothesis. 相似文献
17.
Norton SF 《Science (New York, N.Y.)》1988,241(4861):92-94
In contrast to the diets of other cottid fishes and most teleosts, the diet of Asemichthys taylori is dominated by gastropod mollusks. Access to this underused prey appears to be made possible by morphological speializations of the neurocanium that allow Asemichthys to puncture the shells of its prey during mastication. Unpunched, the shell and operculum act as a barrier to digestion; more than 40% of the unpunched gastropods emerged alive in the feces. Asemichthys adjusted its punching behavior in an apparently adaptive way; other prey lacking such barriers to digestion were rarely punched. The ability of some shelled invertebrates to avoid digestion may make them less desirable as prey for many fishes that cannot masticate this kind of prey. The ability of shelled mollusks to survive in the digestive tracts of vertebrates may provide a dispersal mechanism for otherwise sedentary species. 相似文献
18.
Octopamine: presence in single neurons of Aplysia suggests neurotransmitter function 总被引：3，自引：0，他引：3
Octopamine has been identified and measured in individual neurons from Aplysia californica. Neither dopamine nor norepinephrine was detected in these cells. Thus, in Aplysia there may be separate populations of catecholaminergic and monophenolaminergic cells. Octopamine may have functions of its own in the central nervous system of mollusks. 相似文献
19.
The values of length of synodic month, obtained from tidally controlled periodical growth patterns in mollusks and stromatolites for several geologic periods, indicate that the deceleration rate of the earth's rotation has not been constant. Two breaks in slope, in the Pennsylvanian and Cretaceous, may be related to changes in distribution of continents, oceans, and adjacent shallow seas. 相似文献
20.
The fluorescence assay method has been used in the identification and quantitative estimation of 5-hydroxytryptamine (5-HT) in mollusks. Ganglia of a representative pelecypod contain more 5-HT than those of a gastropod. Most non-nerve tissues have low levels of 5-HT, which, except in "kidneys," may derive from nerve endings. 相似文献