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The reproductive anatomy, and ultrastructural features of the gonads of the articulate brachiopodTerebratulina retusa (Linnaeus), are documented based on collections made between October 1985 and October 1986 from the Firth of Lorn, west coast of Scotland. This species is dioecious, and maturity is achieved in both sexes at shell lengths greater than ~5.5 mm. There is no obvious external sexual dimorphism except for slight differences in the coloration of the gonads; testes are white/cream, ovaries are yellow/orange. The gonads occur as four palmate lobes, a pair in each valve. Gonads are formed within a mantle sinus (vascula genitalia), which is an anterior extension of the coelom, that opens posteriorly into the visceral cavity and to the exterior via a pair of metanephridia. The latter serve as gonoducts during spawning. Gametes are borne on genital lamellae formed from a reticulate lattice of connective tissue. The lamellae are an extension of the ileoparietal band and are fused along one margin to the inner mantle membrane. Developing oocytes are closely affixed to the genital lamellae and originate from a pool of proliferating germ cells at its base. Vitellogenic oocytes that are at an advanced stage are released from the genital lamellae, but are retained within thevascula genitalia. Liberated oocytes continue to accumulate yolk and eventually occlude thevascula genitalia, before being spawned. Coelomocytes were identified within the gonads. In spent females these cells appear to be phagocytic and involved in the resorption of necrotic material, while in the male they may serve as nutritive cells. 相似文献
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刍议医院资产管理的现状及其对策 总被引:1,自引:0,他引:1
肖高峰 《湖南环境生物职业技术学院学报》2008,14(4):31-33
医院的固定资产和流动资产是医院赖以生存和发展的基础,是一项非经营性国有资产.目前公立医院固定资产、流动资产管理现状不容乐观,针对这种状况,首先分析问题形成的原因,然后提出管理的措施或建议,从而使资产管理工作规范化、制度化、科学化,使有限的卫生资源发挥出最大的社会效益和经济效益.参3. 相似文献
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L. Fishelson 《Marine Biology》1971,10(2):113-133
Approximately 500 animal species and plants are listed as being the most typical for the infratidal and shallow subtidal benthic fauna of the Red Sea. Most of them are divided into communities typical for various soft and hard substrata, and at different water depths. The oceanographic conditions and the development of several of the communities are discussed in general terms.Supported partly by grants 62558-4556 and F 671052 67C 0043 of the US Office of Naval Research and Grant SFC-7-0074 of the Smithsonian Institution. 相似文献
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R. Fenaux 《Marine Biology》1972,16(3):230-235
The present paper shows how our knowledge concerning the appendicularians from the Indian Ocean, the Red Sea and the Persian Gulf has evolved. The different historical steps and their relative importance are discussed, and the contributions, either direct or indirect, of the International Indian Ocean Expedition (IIOE) are emphasized. 相似文献
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China's endemic vertebrates sheltering under the protective umbrella of the giant panda 总被引:1,自引:0,他引:1
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Stuart L. Pimm 《Conservation biology》2016,30(2):329-339
The giant panda attracts disproportionate conservation resources. How well does this emphasis protect other endemic species? Detailed data on geographical ranges are not available for plants or invertebrates, so we restrict our analyses to 3 vertebrate taxa: birds, mammals, and amphibians. There are gaps in their protection, and we recommend practical actions to fill them. We identified patterns of species richness, then identified which species are endemic to China, and then which, like the panda, live in forests. After refining each species' range by its known elevational range and remaining forest habitats as determined from remote sensing, we identified the top 5% richest areas as the centers of endemism. Southern mountains, especially the eastern Hengduan Mountains, were centers for all 3 taxa. Over 96% of the panda habitat overlapped the endemic centers. Thus, investing in almost any panda habitat will benefit many other endemics. Existing panda national nature reserves cover all but one of the endemic species that overlap with the panda's distribution. Of particular interest are 14 mammal, 20 bird, and 82 amphibian species that are inadequately protected. Most of these species the International Union for Conservation of Nature currently deems threatened. But 7 mammal, 3 bird, and 20 amphibian species are currently nonthreatened, yet their geographical ranges are <20,000 km2 after accounting for elevational restriction and remaining habitats. These species concentrate mainly in Sichuan, Yunnan, Nan Mountains, and Hainan. There is a high concentration in the east Daxiang and Xiaoxiang Mountains of Sichuan, where pandas are absent and where there are no national nature reserves. The others concentrate in Yunnan, Nan Mountains, and Hainan. Here, 10 prefectures might establish new protected areas or upgrade local nature reserves to national status. 相似文献
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Songs of the humpback whale Megaptera novaeangliae were recorded and analyzed from Grand Turks in the Bahamas to Venezuela. The design features of the song are as follows. The basic song evolves through a series of different sounds in a fixed order. The song is produced only in the winter tropical calving grounds, just before the whales arrive on the banks. Redundancy is high in that syllables, motifs, phrases and the entire song are repeated. Low, intermediate, and high-frequency sounds are scattered throughout the song. One sound is associated with blowing. The song appears to be partially different each year and there are some differences within a year between banks which may indicate that dialects are present. It is suggested that songs from other populations are quite different. The apparent yearly changes do not occur at one point in time. Only single individuals produce the song and they are hypothesized to be young, sexually mature males. The implications of these various design features are discussed. 相似文献
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Cloud optical depth, as it is derived from the King's method, is compared with that deduced from the simple two stream approximation for the greater Athens, Greece area. The results show that King's method overestimates the cloud optical thickness, in comparison to the two stream approximation. These estimations were also compared with satellite observations provided by the International Satellite Cloud Climatology Project. This comparison showed that there are large deviations between ground‐based and satellite observations. These deviations are probably due to the uncertainty introduced by the integration procedure of the satellite spatial analyzing resolution (distinctness). Furthermore, values of the simple scattering albedo were calculated by employing a recently proposed theoretical method and using the solar ultraviolet irradiance measurements performed at the Athens University on a routine basis. These results are of great importance for the densely populated areas like Athens, in a sense of health impacts, from enhanced incident solar ultraviolet radiation. 相似文献
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H. J. Cranfield 《Marine Biology》1973,22(3):211-223
The use during settlement of secretions of the 9 different types of gland in the foot of the pediveliger of Ostrea edulis L. was examined experimentally. During settlement, there is a progressive decrease in the crawling speed of the larva and a strengthening of its bond with the substratum. Both changes are related to (a) a change from ciliary to muscular pedal locomotion; (b) the increasing acidity and viscosity of the mucoid secretions used; (c) the secretion of a byssus thread by the glands of the byssus duet; (d) changes in the form and composition of this byssus. At the termination of settlement, the entire contents of 2 types of gland are discharged. Their secretions give rise to the cement which permanently fixes the larva to the substratum. The 9 types of gland are utilised sequentially in a manner closely related to the 6 phases recognised in settlement behaviour. 相似文献
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Animals disperse in space through different movement behaviors, resulting in different displacement distances. This is often described with a displacement kernel where the long-distance dispersers are within the tail of the kernel. A displacement with a large proportion of long-distance dispersers may have impact on different aspects of spatial ecology such as invasion speed, population persistence, and distribution. It is, however, unclear whether the kurtosis of the kernel plays a major role since a fatter tail also influences the variance of the kernel. We modeled displacement in landscapes with different amounts and configurations of habitats and handled kurtosis and variance separately to study how these affected population distribution and transition time. We conclude that kurtosis is not important for any of these aspects of spatial ecology. The variance of the kernel, on the other hand, was of great importance to both population distribution and transition time. We argue that separating variance and kurtosis can cast new light on the way in which long-distance dispersers are important in ecological processes. Consequences for empirical studies are discussed. 相似文献
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厌氧除磷是一种高效、节能、低耗的方法。获取经济、方便、高效的种泥是实现该方法的前提,种泥中产生磷化氢功能菌株的组成及特性是提高处理效能和开发新工艺的基础,目前此研究未见有关报道。本研究依据厌氧除磷理论,利用厌氧培养反应瓶、筛选培养基和微生物筛选、分离、鉴定的方法。以A2/O厌氧池、污泥浓缩池污泥、养殖场新鲜猪粪、鸡粪、牛粪及鸭粪为研究种泥,通过跟踪厌氧培养过程培养液中总磷的去除率和吸收液中磷化氢的生成量筛选出最佳种泥,并对最佳种泥的菌株进行筛选、分离和鉴定。结果表明,6种泥中鸡粪的厌氧除磷能力最强,鸭粪能力最弱,浓缩池中的污泥和猪粪次之,牛粪及厌氧池污泥有一定的作用。本试验条件下鸡粪是厌氧除磷的最佳种泥。经过3个周期的厌氧培养,6种泥培养液总磷的去除率和吸收液中磷化氢的含量随培养时间增长都有不同程度增加。鸡粪的最佳培养时间为5d。鸡粪培养液经21d培养后分离到1株芽孢杆菌属、1株假单胞菌属及2株肠杆菌科,明确了2株肠杆菌科中1株为埃希氏菌属另1株为柠檬酸杆菌属。 相似文献
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D. P. Gordon 《Marine Biology》1974,27(2):147-163
The architecture and function of the lophophore of the marine bryozoan Cryptosula pallasiana (Moll) are described, including some new features not previously discovered in bryozoans. The nature of fluid movements within the lophophoral coelom during feeding activities is postulated on the basis of the arrangements of epithelia and muscles. Epithelial cells at the tentacle bases are blastemic in nature, and there is a ciliated pit of unknown function in the angle between every pair of tentacles. There are 6 nerves in each tentacle, including a pair of single-axon subperitoneal nerves. Neurosecretory-like vesicles and glycogen occur in some neurons of the ganglion. The basal lamina collagen has a diameter smaller than that previously recorded for an invertebrate. Filament dimensions are given for several different muscles. Tentacle muscles and lophophore retractor muscles are smooth. Thick paramyosin-like filaments up to 75 nm diameter occur in two muscle types. A new set of muscles is described: the basal transverse muscles of the tentacles. 相似文献
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基因组学、蛋白组学和代谢组学技术为生态毒理学的发展提供了生物高通量的技术手段,构成了新的交叉学科——生态毒理基因组学.生态毒理基因组学着重研究环境毒物暴露下非靶生物基因和蛋白的表达,能够在基因组水平上更深入地理解环境污染物的致毒机制,同时,它引进生物标志物为生态风险评价提供了平台.论文对生态毒理基因组学的发展历程、技术支持、模式生物及其在生态风险评价方面的应用进行了综述,以推动生态毒理基因组学技术在我国的进一步发展. 相似文献
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Joris M. Koene Tina Pförtner Nico K. Michiels 《Behavioral ecology and sociobiology》2005,59(2):243-249
Sexual conflict between mating partners can give rise to strategies that are advantageous for one sex but harmful to the opposite sex. Usually, sperm donors develop (offensive) traits to enhance their chances in sperm competition, while sperm recipients evolve (defensive) traits that allow them to stay in control of who fathers their offspring. Here, we demonstrate that these processes are also at work in simultaneous hermaphrodites. The hermaphroditic earthworm Lumbricus terrestris uses 40 to 44 copulatory setae to pierce into its partner's skin, causing damage and injecting a substance from its setal glands. Experimental injection of the gland substance indicates that a refractory period may be induced. More importantly, removal of the copulatory setae shows that they influence the partner's sperm uptake. When the setae are present, more sperm are taken up and sperm are distributed more equally over the four spermathecae. We interpret this as a strategy that stacks the odds for the donor's sperm in fertilizing cocoons. 相似文献
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Because choice is conflict, decision-making is necessarily about conflict resolution. Choices are necessary because the options
are mutually exclusive but the nature of this inherent conflict varies. Typically, these conflicts are multidimensional. In
coasal zones, the complex interactions between systems makes decision-making particularly complex; in particular, environmental
interests are themselves frequently in conflict. In making a choice, it is important to determine why that choice is necessary
in the first place.
There are further conflicts about the objectives to be satisfied by the decision process; between the determination of the
best outcome and the best decision process. Social scientists centre upon the requirement for a fair decision process rather
than upon seeking an optimum outcome. Unlike physical scientists who seek more and better information, social scientists focus
upon the development and maintenance of institutions. 相似文献
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城市化趋势下城郊土地利用结构变化的区位分析--以杭州市为例 总被引:3,自引:0,他引:3
以杭州市区为研究区,利用近卜年的土地利用系列统计资料和遥感解译数据,采用统计分析和区位原理,经过数值计算,分析了杭州市区扩建过程中土地利用动态变化特点,重点讨论了耕地和农作物播种面积的时空动态过程。通过区位商数和分离指数的计算分析,揭示了未来土地利用方式的时空变化趋势。研究结果表明,居民工矿用地和耕地面积的变化最为明显;农作物播种面积的递减速率高于耕地面积的递减速率;蔬菜播种面积的区域不平衡性最大,集中程度高。萧山区是未来主要的菜篮子工程发展区。 相似文献
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王献薄 《生态与农村环境学报》1995,(2)
景观作为自然与人类相互作用的一个基本单位,目前正在发生剧烈的变化。许多传统的文化建筑和土地利用方式和格局正在走向衰亡,景观的多样性和丰富性受到前所未有的威胁,常常被千篇一律的大片单调的景色所代替。本文主要讨论下列三个问题:景观的基本含义及其保护,景观保护的主要任务;景观保护是区域发展的基础。 相似文献
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The typical parameters of acid precipitation are evaluated in the forest of Vallombrosa (Tuscan Appennines) during the dry period 1988-89. Individual rain events (dry and wet deposition) were sampled in a clearing of the forest and below the canopy of an evergreen tree as well as a deciduous broadleaf tree.
In atmospheric precipitation the pH values usually vary around 4.4, with neutralization in the hot season due to calcareous material from distant sources. Relatively large concentrations of Pb and Cd are found in rain, but only in a small amount in canopy leachate. Aluminium, manganese and iron are more significantly washed off than Pb and Cd. 相似文献
In atmospheric precipitation the pH values usually vary around 4.4, with neutralization in the hot season due to calcareous material from distant sources. Relatively large concentrations of Pb and Cd are found in rain, but only in a small amount in canopy leachate. Aluminium, manganese and iron are more significantly washed off than Pb and Cd. 相似文献