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81.
Tiger sharks (Galeocerdo cuvier) play an important ecological role as top predators, yet knowledge of their reproductive ecology is scarce. Here, the authors report the first observation of a potential neonate G. cuvier at Cocos Island, a predator-dominated oceanic island in the Eastern Tropical Pacific (ETP). The individual was detected using baited remote underwater video stations (BRUVS). The cameras also detected female individuals potentially pregnant, suggesting that parturition may take place at or near the island. Nonetheless, it is still unclear if the presence of a single neonate is an isolated event or evidence that the species is using the island for reproduction.  相似文献   
82.
连作障碍严重限制了当归产业的可持续发展。为了探索当归(Angelica sinensis)高效栽培技术,本研究在当归主产区甘肃省渭源县设置5种种植模式(A: 豌豆-当归-当归,对照;B: 豌豆-小麦-当归;C: 豌豆-蒙古黄芪-当归;D: 豌豆-马铃薯-当归;E: 豌豆-休耕-当归),于采挖期分别测定不同种植模式下,当归根际土壤理化特性和细菌基因组DNA相对丰度,分析不同种植模式对当归根际土壤理化特性、细菌群落多样性和代谢通路的影响。结果表明: 1) 5种种植模式下当归根际土壤理化特性差异较大。与对照相比,C模式根际土壤的电导率显著增加,B、D和E模式的电导率略有下降,B、C、D和E模式的土壤CO2呼吸速率显著提高。2) 5种种植模式的当归根际土壤细菌隶属于26门368属,其中,芽单胞菌门的芽单胞菌属、变形菌门的鞘脂单胞菌属和酸杆菌门的Subgroup_6属为优势菌属。与对照相比,B、C模式变形菌门和放线菌门的相对丰度显著增加,D模式酸杆菌门的相对丰度显著降低;E模式变形菌门、酸杆菌门和放线菌门的相对丰度显著增加。3) 5种种植模式下,当归根际土壤的pH值、电导率、有机质、碱解氮、有效磷和速效钾含量与变形菌门细菌的相对丰度呈显著负相关。4) 5种种植模式下,当归根际土壤中6种代谢通路细菌的相对丰度差异显著。C模式对当归根际土壤理化特性和细菌群落有较好的调节作用,是克服当归连作障碍的主要种植模式。  相似文献   
83.
胡蜂Vespidae是重要的捕食性天敌和授粉昆虫,敌害是制约胡蜂种群存活与发育的主要因素之一,弄清胡蜂的敌害种类和危害,可以为下一步防治技术措施的研究提供参考.通过目测法和设监视器等方法对广西胡蜂标准蜂群培育及其野训成为经济蜂群阶段的敌害种类和危害情况进行了初步调查,结果发现,胡蜂的敌害共有33种,其中有害动物19种、有害微生物14种.在标准蜂群野训成为经济蜂群期,对胡蜂危害严重的有害动物为蚂蚁、鸟类、盗虻、蝙蝠及松鼠等,蚂蚁对蜂群的危害最严重、最普遍;在蜂王越冬及标准蜂群培育期,对胡蜂危害严重的病害种类较多,有以色列急性麻痹病毒病、白垩病、欧幼病等,其中危害最严重的是以色列急性麻痹病毒病.14种有害微生物中,有13种病害是蜜蜂群中常见的病害.  相似文献   
84.
Pine barrens are open‐canopy ecological communities once prevalent on sandy soils across the northern Great Lakes Region of the United States and Canada, though fire suppression and plantation forestry have now reduced them to a few isolated areas. Efforts to restore pine barrens are underway on some public lands, but lack of knowledge on the social and ecological issues and challenges that affect these projects impedes fuller progress. As a precursor to designing a public preference survey for pine barrens restoration, we sought input from those with expert knowledge about pine barrens. Using a three‐round modified Delphi survey, forest land managers and researchers identified the key characteristics of pine barrens and important current and future management challenges. Key characteristics were related to fire, landscape structure, plant and animal species, soils, and social themes. Current and future challenges were related to landscape, invasive species, social, economic, climate change, and science themes. Four social issues (education, fire acceptance, fire risk, aesthetics) were rated among the top current challenges but none of them maintained prominence as future challenges. Potential explanations for this shift are that the experts felt these social concerns would be resolved in time or that other issues, such as development pressures and budgets for carrying out restoration, would become greater future challenges. Our approach can be used by managers and researchers to better understand the ecosystems they seek to restore and to communicate with public stakeholders about restoration efforts.  相似文献   
85.

A circadian rhythm of activity is demonstrated in single neurons of Nephrops norvegicus (L.). Eyestalk extracts depress neural and locomotor activity. Entrainment of rhythmicity is achieved by the environmental light cycle, apparently acting through the eye.  相似文献   
86.
ABSTRACT

A phytosociological study of the shrubland communities which colonise abandoned terraced olive groves in the Tyrrhenian district of Central Italy is presented here. The vegetational analysis was carried out using the Braun Blanquet phytosociological approach. Two main types of shrubland communities characterising distinct environmental conditions occur within abandoned terraced olive groves. On the one hand, there are those scrub types which tend to occupy the central part of the terrace; on the other hand, there are the scrubs types which develop along the stone walls bordering the terrace. Different phytosociological associations, sub-associations, and variants ranging from Pistacio-Rhamnetalia alaternii to Prunetalia spinosae are recognised and described. In the warm dry areas, both Myrto-Lentiscetum and Rhamno-Euphorbietum dendroidis occur. Also, a new Oleo-Ceratonion sub-association (Myrto-Lentiscetum spartietosum junceii) is presented here for the first time. In the inner zones of the study area, a range of aspects characterising a new Pruno-Rubion ulmifolii community type (Roso-Rubetum ulmifolii ass. nova) are identified.  相似文献   
87.
88.
Abstract

The effects of kinetin on chlorophyll breakdown in irradiated barley leaves. — Kinetin is shown to inhibit the breakdown of chlorophyll in isolated barley leaves. Moreover the kinetin is shown to inhibit, even if with lower effect, the chlorophyll breakdown in irradiated barley leaves. This possible correlation of these observations, with kinetin promoted protein synthesis is suggested.  相似文献   
89.
The specific species-rich high-altitude vegetation of the class Carici rupestris-Kobresietea bellardii Ohba 1974 (CK), with the occurrence of many arctic-alpine and endemic species, was chosen for a case study. The analyses were based on a dataset of 37,204 phytosociological relevés from the Slovak Vegetation Database. The traditional classification of the class CK, based on cluster analyses, was reproduced satisfactorily by means of formalised classification, based on the formal definitions created by the Cocktail method together with the frequency-positive fidelity index affiliation. Unequivocal assignment criteria for all eight associations of both alliances [Oxytropido-Elynion Br.-Bl. (1948) 1949 and Festucion versicoloris Krajina 1933] of the class CK were formulated. The formal delimitations followed the traditional ones very well. It was demonstrated that the results of applying the formal definitions created on the basis of a large, geographically stratified dataset capturing the occurrence of all vegetation types in Slovakia were highly similar in comparison with the traditional classification based on the results of cluster analysis. The reliability and the pros and cons of the expert system are also discussed.  相似文献   
90.
Three new species of the streptaxid snail genus Perrottetia are described from north and northeastern Thailand, Perrottetia aquilonaria sp. n., Perrottetia dermapyrrhosa sp. n. and Perrottetia phuphamanensis sp. n. Each species is endemic to a single or a few limestone mountain ranges. The species are characterized by the morphology of their genital organs, as well as by shell characters. Perrottetia aquilonaria sp. n. has a club shaped distal penis and large penial hooks are present and penial papillae cover almost the entire penial hook portion; adjacent areas possess low reticulated folds. Perrottetia dermapyrrhosa sp. n. has a long genital atrium and the penial sheath is about two-thirds of the penis length. Penial hooks are long, scattered and sunken into deep ovate hollows; vaginal hooks are present. Perrottetia phuphamanensis sp. n. has a rounded and protruded shell periphery. The aperture is subcircular, peristome is thick and the second parietal lamella is adjacent to the first parietal lamella; a basal lamella is the smaller than in the other Thai species.  相似文献   
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