共查询到20条相似文献,搜索用时 15 毫秒
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Early theories of aging suggested that organisms with relatively high metabolic rates would live shorter lives. Despite widespread tests of this 'rate of living' theory of aging, there is little empirical evidence to support the idea. A more fine-grained approach that examined age-related changes in metabolic rate over the life span could provide valuable insight into the relationship between metabolic rate and aging. Here we compare age-related metabolic rate (measured as CO2 production per hour) and age-related mortality rate among five species in the genus Drosophila. We find no evidence that longer-lived species have lower metabolic rates. In all five species, there is no clear evidence of an age-related metabolic decline. Metabolic rates are strikingly constant throughout the life course, with the exception of females of D. hydei, in which metabolic rates show an increase over the first third of the life span and then decline. We argue that some physiological traits may have been shaped by such strong selection over evolutionary time that they are relatively resistant to the decline in the force of selection that occurs within the life time of a single individual. We suggest that comparisons of specific traits that do not show signs of aging with those traits that do decline with age could provide insight into the aging process. 相似文献
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Wentsaiboea renifolia D. Fang & D. H. Qin, a new genus and species of Gesneriaceae from Guangxi, China, is described and illustrated. This genus is similar to Dolicholoma D. Fang & W. T. Wang in the shape of stigma, but differs by having leaves reniform, palmately nerved and base cordate, corolla obliquely campanulate, corolla lobes rounded, and both stamens and staminodes adnate to corolla tube near base. It is also similar to Chiritopsis W. T. Wang in the habit, but differs by having leaves palmately nerved, corolla tube campanulate and abaxially swollen, and stigma hippocrepiform. 相似文献
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国产牡竹属野龙竹和版纳甜龙竹的订正 总被引:1,自引:0,他引:1
通过对模式标本和原始文献的研究,确认<中国植物志>、、<云南植物志>、<中国竹类植物图志>、<云南树木图志>、<中国竹类图志>等重要专著中广泛使用的版纳甜龙竹学名Dendrocdanus hamittonii Nees et Arn.为错误鉴定,其正确学名为D.parishii Munro;野龙竹(D.semiscandens Hsueh et D.Z.Li)为D.ham iltonii Nees et Arn.的异名. 相似文献
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Two new species of bamboo, Dendrocalamus ovatus Xia et Chia and D.
textilis Xia, Chia et C. Y. Xia, collected from southwestern China aredescribed. 相似文献
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M. Pascual J. Balanya A. Latorre L. Serra 《Journal of Zoological Systematics and Evolutionary Research》1997,35(4):159-164
The disribution ranges of Drosophila azteca and D. athabasca overlap in northen California and southern Oregon. Seven populations, four of which are located in this area, were studied. Large random amplified polymorphic DNA (RAPD) variation was found within species; nevertheless, more than half the primers used in the study yielded greater diofference between than within species. A nested analysis of molecular variance (AMOVA) showed that the variance between populations within species was significantly greater than zero for 55% of the oligonucleotides used, which provided evidence for an underlying geographical structure of these populations. Specimens of D. azteca and D. athabasca from Salem (OR), where both species were collected together, presented the highest similarity encountered between species. 相似文献
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报道了内脐蠕孢属一新种棗燕麦生内脐蠕孢Drechslera avenicola和两个中国新记录种:安德森内脐蠕孢Drechslera andersenii和席氏内脐蠕孢Drechslera sivanesanii。新种与新记录种均附绘图。研究的标本保存在山东农业大学植物病理学标本室(HSAUP) 相似文献
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两种菊属植物的核型研究 总被引:12,自引:2,他引:10
杜冰群;刘启宏;朱翠英;柯善强 《武汉植物学研究》1989,7(3):293-296
神农香菊和野菊均为菊属(Dendranthema)植物。神农香菊D. indicum var.aromaticum为菊属的一个新变种,是武汉植物所在湖北神农架首先发现的一种具有较高经济价值的香料和药用植物资源,它与原种野菊很近似,主要区别在于神农香菊的花叶根具浓香,叶片较小而质厚,深绿色,叶脉明显隆起,下面具极小腺体,头状花序 相似文献
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广西苦苣苔科一新属——文采苣苔属 总被引:1,自引:0,他引:1
描述了在广西发现的苦苣苔科一新属和一新种,即文采苣苔属Wentsaiboea D. Fang & D. H. Qin及文采苣苔W. renifolia D. Fang & D. H. Qin, 并提供墨线图。文采苣苔属的柱头外形略似长檐苣苔属Dolicholoma D. Fang & W. T. Wang, 不同在于前者叶肾形,基部心形,具掌状脉,花冠斜钟状,裂片圆形,雄蕊和退化雄蕊着生于冠筒近基部。新属在体态上还接近小花苣苔属Chiritopsis W. T. Wang, 但前者叶具掌状脉,冠筒钟状,远轴侧膨胀,柱头马蹄形;在后者叶具羽状脉,冠筒筒状,不膨胀,柱头下唇倒梯形至线形。 相似文献
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Characterisation of human N-acetyl-beta-hexosaminidase C 总被引:7,自引:0,他引:7
I Braidman M Carroll N Dance D Robinson L Poenaru A Weber J C Dreyfus B Overdijk G J Hooghwinkel 《FEBS letters》1974,41(2):181-184
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In rivers, variations in concentrations of many dissolved nutrients occur during spates. Increases are usually attributed
to concentrated point or non-point inputs, and decreases to dilution associated with rainfall. Increased discharge disturbs
sediments and benthic communities, but the effects of such disturbance on nutrient levels are difficult to isolate. Measurements
of nutrient levels over three artificial spates revealed that substantial variations in dissolved organic carbon, dissolved
phosphate, silicate, nitrate, and potassium levels could result from increased discharge in the absence of allochthonous inputs.
Variations were closely related to peaks in suspended solids concentration or water height. Increases in biochemical oxygen
demand and suspended bacteria also occurred.
Variations in phosphate and silicate could be accounted for by a balance between release of ‘sediment interstitial water’
and exchange processes involving suspended and freshly exposed sediment.
An increase in nitrate, during one spate, was probably due to a reduction in the effect of benthic denitrification.
Small peaks in dissolved organic matter concentration were detected over each spate.
We propose that within-stream disturbance is a factor which may contribute to variations in dissolved nutrient concentration
during the rising hydrograph in natural spates. 相似文献
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在进行中国砖格丝孢菌分类研究中,发现砖格孢属一个新种和两个中国新记录种。新种是泰山砖格孢Dictyosporiumtaishanensis,新记录种是索兰砖格孢Dictyosporiumsolani和七臂砖格孢Dictyosporiumheptasporum。分别对三个种进行了中文描述,并附图,新种有拉丁文描述。研究标本保存在山东农业大学植物病理学标本室(HSAUP)。 相似文献
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MANMOHAN D. SHARMA TOM TREGENZA DAVID J. HOSKEN 《Biological journal of the Linnean Society. Linnean Society of London》2011,103(4):923-934
There has been recent debate about the expected allometry of sexually‐selected traits. Although sexually‐selected traits exhibit a diversity of allometric patterns, signalling characters are frequently positively allometric. By contrast, insect genitalia tend to be negatively allometric, although the allometry of nongenital sexually‐selected characters in insects is largely unknown (with some notable exceptions). It has also been suggested that there should be a negative association between the asymmetry and size of bilaterally‐paired, sexually‐selected traits, although this claim is controversial. We assessed the allometry and asymmetry (fluctuating asymmetry, FA) of a nongenital contact–courtship structure, the sex comb, in replicate populations of three species of Drosophila (we also measured wing FA). Sex combs are sexually‐selected characters used to grasp the female's abdomen and genitalia and to spread her wings prior to and during copulation. Although species differed in the size of the sex combs, all combs were positively allometric, and comb allometry did not generally differ significantly between species or populations. Comb and wing asymmetry did vary across species, although not across populations of the same species. However, FA was trait specific and was never negatively associated with trait size. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 923–934. 相似文献
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在进行中国砖格丝孢菌分类研究中,发现砖格孢属一个新种和两个中国新记录种。新种是泰山砖格孢Dictyosporiumtaishanensis,新记录种是索兰砖格孢Dictyosporiumsolani和七臂砖格孢Dictyosporiumheptasporum。分别对三个种进行了中文描述,并附图,新种有拉丁文描述。研究标本保存在山东农业大学植物病理学标本室(HSAUP)。 相似文献