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Robertson DR 《Science (New York, N.Y.)》1972,177(4053):1007-1009
Males of Labroides dimidiatus control the process of sex reversal within social groups. Each group consists of a male with a harem of females, among which larger individuals dominate smaller ones. The male in each harem suppresses the tendency of the females to change sex by actively dominating them. Death of the male releases this suppression and the dominant female of the harem changes sex immediately. Possible genetic advantages of the system are considered. 相似文献
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Many mammalian species rely on pheromones-semiochemicals produced by other members of the same species-to communicate social status and reproductive readiness. To assess how the central nervous system integrates the complex repertoire of pheromones, we recorded from single neurons in the accessory olfactory bulb, a nucleus that processes pheromonal signals, of male mice engaged in natural behaviors. Neuronal firing was robustly modulated by physical contact with male and female conspecifics, with individual neurons activated selectively by specific combinations of the sex and strain of conspecifics. We infer that mammals encode social and reproductive information by integrating vomeronasal sensory activity specific to sex and genetic makeup. 相似文献
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In male swordtails ((Xiphophorus nigrensis)) there are three size classes that derive from allelic variation at the pituitary locus on the Y chromosome. Progeny analysis and preference tests suggest that females prefer to mate with larger males. In the closely related X. pygmaeus, there is no allelic variation at this locus; this species consists of males similar in size only to smaller X. nigrensis males. In addition to being smaller than most X. nigrensis males, these X.pygmaeus males also lack both the swordtail and a major component of the courtship display common in most X. nigrensis males. Usually, female X. pygmaeus prefer to mate with heterospecific males rather than conspecifics, regardless of body size and the presence of a swordtail. However, the smallest X. nigrensis males lack the same courtship component as do the X. pygmaeus males, and in this comparison female X. pygmaeus show no preference. Although sexual selection, through its action on divergence of courtship displays, has been implicated as a factor leading to speciation, in this case sexual selection could lead to the congealing of gene pools between heterospecifics. 相似文献
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寄主大小模型认为寄生蜂后代性比与寄主大小相关,寄生蜂倾向于在大寄主上产出更多雌性后代,在小寄主上产出更多雄性后代。探讨了以家蝇蛹为寄主时,蝇蛹佣小蜂后代产量和性比变化;单次寄生情况下,寄主大小及寄生顺序对寄生蜂后代性比等影响。结果表明,蝇蛹佣小蜂的产卵期为(8.93±3.34) d,单头雌蜂能产雌性后代(34.11±16.34)头和雄性后代(11.04±8.87)头,且雄性百分比为0.24±0.11。随成蜂日龄的增大,寄生蜂产生雄性后代的比率显著增加。蝇蛹佣小蜂在寄生家蝇蛹时,会优先选择寄生个体较大的蛹;在单次寄生的情况下,蝇蛹佣小蜂倾向于在较大的家蝇蛹内产出更多的雌性后代。 相似文献
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2011年4月中旬至5月下旬,在长白山头道白河上游捕捞北方条鳅样本846尾,对其种群结构进行了,分析,结果表明：捕捞群体的体长为2．2—14．6em,平均8．8cm,以10-12cm体长组和2-4cm体长组的数量最多,两者所占的比例合计达75．3％,呈明显的双峰型分布格局．雌性和雄性群体的体长组成相似;捕捞群体的总体性比接近1：1,但不同体长组的性比不同,个体小者（体长小于8cm）雌性所占比例较低,个体大者（体长大于13cm）雌性所占比例则明显偏高;春季迁移过程一般是大个体在先,小个体在后． 相似文献
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克氏原螯虾交配行为的研究 总被引：10，自引：0，他引：10
本文以对比行为实验方法研究了克氏原螯虾的交配行为。结果表明，克氏原螯虾交配过程可分为交配前期和交配期。在交配前期．雄虾表现出特有的交配前期行为；交配期包括钳夹、翻转、横跨、交尾和分离五个阶段。雌虾被雄虾钳住后表现顺从行为；而在对照组中的雌虾被同性钳住后却不表现顺从行为。雄虾之间的接触导致进攻行为。交配时雄虾横跨的步足均为右第5步足；雌虾在交配前勿需生殖蜕皮，交配的成败与雄虾接近雌虾的行为方式有关。且螯足较大的雄性个体交配成功率明显较高。 相似文献
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G Medeiros-Ribeiro AM Bratkovski TI Kamins DAA Ohlberg RS Williams 《Science (New York, N.Y.)》1998,279(5349):353-355
Chemical vapor deposition of germanium onto the silicon (001) surface at atmospheric pressure and 600 degrees Celsius has previously been shown to produce distinct families of smaller (up to 6 nanometers high) and larger (all approximately 15 nanometers high) nanocrystals. Under ultrahigh-vacuum conditions, physical vapor deposition at approximately the same substrate temperature and growth rate produced a similar bimodal size distribution. In situ scanning tunneling microscopy revealed that the smaller square-based pyramids transform abruptly during growth to significantly larger multifaceted domes, and that few structures with intermediate size and shape remain. Both nanocrystal shapes have size-dependent energy minima that result from the interplay between strain relaxation at the facets and stress concentration at the edges. A thermodynamic model similar to a phase transition accounts for this abrupt morphology change. 相似文献
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本文以对比行为实验方法研究了克氏原螯虾的交配行为。结果表明，克氏原螯虾交配过程可分为交配前期和交配期。在交配前期．雄虾表现出特有的交配前期行为；交配期包括钳夹、翻转、横跨、交尾和分离五个阶段。雌虾被雄虾钳住后表现顺从行为；而在对照组中的雌虾被同性钳住后却不表现顺从行为。雄虾之间的接触导致进攻行为。交配时雄虾横跨的步足均为右第5步足；雌虾在交配前勿需生殖蜕皮，交配的成败与雄虾接近雌虾的行为方式有关。且螯足较大的雄性个体交配成功率明显较高。 相似文献
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在灌水和非灌水条件下,研究了5个不同基因型小麦群体动态的变化及其与产量的相关性表现。 结果表明,不同基因型小麦在灌水小区的群体指标明显高于非灌水小区;叶面积指数(LAI)变化呈“S”形曲线,且与 产量有很大的相关关系;在干旱条件下全生育期的LAI变化幅度较灌水条件下小,且拔节以后的LAI对产量影响 较大;不同处理下各基因型小麦群体变化对产量的贡献不同。因此,在旱作农业生产中,小麦除了选用大穗型品种 外,还要力求保持小麦生育后期有较高的绿叶面积,并使各因素协调发展,以获得较高的经济产量。 相似文献
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The mouse vomeronasal organ (VNO) is thought to mediate social behaviors and neuroendocrine changes elicited by pheromonal cues. The molecular mechanisms underlying the sensory response to pheromones and the behavioral repertoire induced through the VNO are not fully characterized. Using the tools of mouse genetics and multielectrode recording, we demonstrate that the sensory activation of VNO neurons requires TRP2, a putative ion channel of the transient receptor potential family that is expressed exclusively in these neurons. Moreover, we show that male mice deficient in TRP2 expression fail to display male-male aggression, and they initiate sexual and courtship behaviors toward both males and females. Our study suggests that, in the mouse, sensory activation of the VNO is essential for sex discrimination of conspecifics and thus ensures gender-specific behavior. 相似文献
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木本植物木质部栓塞修复机制的探讨 总被引：1，自引：0，他引：1
该文用几种木本植物茎做切片实验,探讨木本植物木质部栓塞的修复机制.研究发现:当脱水样品被复水后,在表面张力的作用下,其管状细胞中的空气立即回缩,形成长形或球形气泡;此后,在比较小的管状细胞中的气泡逐渐缩小直到消失;大的管状细胞中的气泡最初会伸长,然后缩短,直到消失;胞外球形泡也会一个接一个地出现; 除了来自细胞的切破处,这些胞外球形泡还来自木射线的横断面,其中小些的会缩小,大个的会长大. 这些现象说明,样品中的气体并没有如以往所云,溶解到水中之后进入大气.作者认为,空气也许从短半径气泡移动到了长半径气泡中.有两种可能的机制可以解释这一现象,一是根据表面张力附加压强公式,气体会由半径小、压强大的小气泡移动到大气泡;二是根据物理学的统计理论,从小气泡溶解到水分中的空气能够扩散,进入临近的、压强较小的大气泡. 两种机制导致样品中小管状细胞栓塞的修复. 因此,作者认为,对活体植物, 空穴化事件之后,空气难以从木质部移动到大气中,而是从小的管状细胞中运动到了大的管状细胞中或其他低气压区域,从而导致木质部栓塞的修复. 相似文献
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春季杨树苗圃主要地下害虫群落生态位研究 总被引：3，自引：0，他引：3
分析了杨树苗圃春季主要地下害虫群落的空间生态位、时间生态位以及时空二维生态位。结果表明:6种主要地下害虫生态位各不相同:在空间维度上,小黄鳃金龟、华北大黑鳃金龟以及阔胫鳃金龟生态位宽度较大,黑绒鳃金龟和沟金针虫生态位宽度较小;小黄鳃金龟与沟金针虫生态位重叠值较大,毛黄脊鳃金龟与沟金针虫重叠值较小。在时间维度上,除毛黄脊鳃金龟生态位宽度较小外,其他地下害虫生态位宽度均较大。在时空维度上,阔胫鳃金龟生态位宽度最大,沟金针虫生态位宽度最小;阔胫鳃金龟与沟金针虫生态位重叠值较大,黑绒鳃金龟与沟金针虫重叠值较小。 相似文献
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Learning by rats was facilitated when response-relevant cues were provided by other rats; learning increased as a function of number of cues provided. These results suggest that rats can learn by imitation. Learning by rats that observed conspecifics not emitting response-relevant cues was retarded compared to learning by rats that did not observe conspecifics. This indicates that a conspecific's presence can also inhibit learning, a result consistent with social facilitation theory. 相似文献
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Phenobarbital: effects of long-term administration on behavior and brain of artificially reared rats
Two doses of phenobarbital were given daily for 2 weeks to infant rats fed by intragastric cannulas. The larger dose (60 milligrams per kilogram of body weight) resulted in decreased spontaneous activity and increased responses to novel stimuli. The smaller dose (15 milligrams per kilogram) resulted in increased spontaneous activity and also an increase of responses to novel stimuli. The larger dose produced a 12 percent reduction in brain growth, while the smaller dose was associated with a 3 percent reduction in brain growth. 相似文献
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性别、胸径和叶龄对东北红豆杉针叶内防御蛋白活力的影响 总被引：1，自引：0，他引：1
为研究东北红豆杉的性别、树龄和叶龄与其组成抗性的相关性,分别对东北红豆杉不同性别(雌雄)、胸径(40~50cm、60~70cm, DHB)和叶龄(1、2、3年生)针叶内苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)、过氧化氢酶(CAT)、胰蛋白酶抑制剂(TI)和胰凝乳蛋白酶抑制剂(CI)的活性进行了差异显著性分析。结果表明,性别、胸径和叶龄对PAL、PPO、POD、TI和CI的活性影响差异显著(P<0.05)。东北红豆杉雄株1、2年生叶内TI活性显著高于雌株(P<0.05),东北红豆杉雌株针叶内CI的活性显著高于雄株(P<0.05),TI和CI在东北红豆杉雌雄株内的活性呈现相反的趋势;胸径大的植株针叶内PAL和POD的活性显著高于胸径小的(P<0.05);低叶龄针叶内TI活性显著高于高叶龄的,而低叶龄针叶内PAL活性显著低于高叶龄的(P<0.05)。植物的组成抗性是植物在未受到侵害时就已经具备的天然抗性屏障,防御蛋白是组成抗性的重要组成部分,本研究结果说明东北红豆杉组成抗性与性别、胸径和叶龄的相关性都较大。 相似文献
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在饲喂高脂饲料时,大白鼠的血清总胆固醇和α_2-脂蛋白升高,α_1-脂蛋白下降,由饲喂高脂饲料改为饲喂基础饲料后,血清总胆固醇逐渐地恢复正常。在饲喂高脂饲料的同时,进行运动训练,大白鼠的血清α_2-脂蛋白未见升高,血清总胆固醇的变化与饲喂高脂饲料时间的长短以及运动量的大小有关。当运动量较小时,大白鼠的血清总胆固醇虽有升高,但其差别无显著性。当运动量较大时,若饲喂高脂饲料的时间较短,则大白鼠的血清总胆固醇下降;若饲喂高脂饲料的时间较长,其差别无显著性。由饲喂高脂饲料改为饲喂基础饲料后,进行运动训练的大白鼠血清总胆固醇下降;血清甘油三酯的变化与运动量有关,在运动量较大时。大白鼠的血清甘油三酯下降。 相似文献
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百合种球大小对不同发育阶段鳞茎中糖和淀粉含量及淀粉酶活性的影响 总被引：4，自引：0，他引：4
以兰州百合与亚洲系精粹百合鳞茎为试材,研究不同规格鳞茎发育过程中糖和淀粉含量及淀粉酶活性的变化。结果表明：较小规格鳞茎淀粉积累始期与高峰期分别比较大规格鳞茎提前约10d。兰州百合鳞茎A[φ=（6．4±0．6）cm]可溶性糖的积累比鳞茎B[Φ=（4．9±0．3）cm]提前10d,而精粹百合鳞茎C[φ=（6．0±0．5）cm]比鳞茎D[Φ=（4．3±0．5）cm]提前20d。精粹百合萌发阶段总可溶性糖的下降幅度大于兰州百合。百合鳞茎中的α-淀粉酶活性显著高于β-淀粉酶活性,并且较大鳞茎的淀粉酶活性高于较小鳞茎。采收期不同,不同规格的百合鳞茎内部的碳水化合物含量水平有较大差异。兰州百合鳞茎A淀粉含量在植株半枯期达到最大值（30.39％）,鳞茎B花后60d淀粉含量达最大值（37．87％）。 相似文献