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11.
黄土中蜗牛壳Mn^2＋的EPR研究及其古气候意义 总被引：2，自引：0，他引：2
对黄土高原陕西省洛川和甘肃省西峰剖面中黄土－古土壤层中的蜗牛壳进行了EPR波谱分析，同时对洛川地区的现代蜗牛壳也进行了测定。结果显示：（1）不同种类的蜗牛壳具有相近的EPR信号强度，表明不同种类的蜗牛对Mn^2+的吸收没有差异性。（2）黄土层中蜗牛壳的EPR信号强度远大于占土壤中的，即黄土中蜗牛壳所含的Mn^2+远大于古土壤中的蜗牛壳的Mn^2+的含量，说明前者生活在比较还原的条件下，后者形成环境的氧化性较高。因此本认为为蜗牛壳中Mn^2+的含量可反映其生长环境中Mn^2+的含量和氧化还原条件，对古气候的重建具有重要意义。 相似文献
12.
本文通过对渭南黄土剖面末次盛冰期地层较高分辨率的蜗牛化石记录研究，发现这一时期特征蜗牛种类峰值的演替反映了古气候的演化过程和温，湿度的组合关系。气候变化显示出百年-千年尺度波动的特征，温度的变化明显地要早于湿度（降水）的变化1000-2000a，表现为变冷-冷湿-冷干-温干-温湿的气候过程，研究认为造成这一气候特点的原因是东亚冬，夏季风共同作用的结果，可喜温湿蜗牛种类的研究，揭示出东亚夏季风在这一时期至少能够持续地影响到黄土高原的东南部地区，这个时期冬季风强化的结果之一是影响了夏季风在这一地区滞留的时间，加大了季节性的差异，分析表明尽管夏季风在这一地区滞留的时间缩短，但维持了它固有的强度，提供了适量的水热条件供喜温湿蜗牛种类在这一寒冷阶段持续地生长和发育。 相似文献
13.
河蚬是原产于我国和东南亚地区的一种淡水双壳类底栖动物,极强的环境适应能力使其在世界越来越多的淡水环境中成为优势动物种类,为研究生物对环境变化的适应性提供了一个范例。壳体是河蚬适应外部环境的重要器官,长期以来被认为由文石矿物组成。通过对我国黄河下游、淮河流域、长江和西江流域河蚬壳体显微结构观察和矿物成分X射线衍射分析,我们发现文石仅占壳体矿物质平均组成的95.5%,其余为方解石、蒙脱石、高岭石和伊利石等,平均含量各为1%左右。壳体棱柱层和薄片层中文石矿物的含量也存在系统差异,后者高出前者11%左右。河蚬壳体相同部位棱柱层文石含量表现出显著的区域变化特征,淮河和长江流域文石含量较高,分别达到96.1%和97.8%。而汉水和西江流域壳体中文石矿物含量较低,平均分别为94.5%和94.2%。黄河下游和珠江流域的数据较少,但已有数据显示前者文石含量低至92.7%而后者高达98.4%。壳体文石矿物含量的变化与区域气候变化和环境污染之间存在较好的对应关系,是河蚬适应环境变化的结果。本研究结果有助于在全球变化背景下利用生物的适应特点保护陆地水环境的生物多样性。 相似文献
14.
Alla V. Silina 《Ocean Science Journal》2006,41(4):211-219
A comparison was made of population of the economically important cockleAnadara (=Scapharca)broughtoni (Bivalvia, Arcidae) inhabiting different areas of the Razdolnaya River estuary at the head of Amurskii Bay (Peter the Great
Gulf, East Sea). Also, changes in cockle population density and structure, as well as in cockle growth rates during the last
20 years were studied. In all years of investigation, the morphometrical parameters and growth rates of cockles were smaller
at the sites located close to the River mouth than farther down-estuary. The differences can be attributed to higher concentration
of suspended particulate matter, decreased salinity and water temperature, as well as a longer exposure to these unfavorable
environmental factors at sites located close to the River mouth, compared to farther sites. For two decades, cockle population
density had decreased by almost 30 times at some sites in the River estuary. The main reason for this population decline is
commercial over-fishing of the cockle. Besides, for the last 20 years, linear parameters of the cockles in the population
decreased approximately by 30% and weight parameters, almost two times. Cockle growth rates also decreased for this period.
Evidently, these facts are due to the damaging effect of dredging. 相似文献
15.
Saday Azadoglu ALIYEV Ali SARI Bahadir KTEN Ankara University Faculty of Engineering Department of Geological Engineering Tandogan Ankara Turkey 《《地质学报》英文版》2008,82(6)
Concentrations of some heavy metals and trace elements such as Cr,Ga,Ni,Zn,Mo,Cu, Pb,Yb,Y,Nb,Ti,Sr,Ba,Mn,Sc,Co,V,Zr,Fe,Al,W,Se,Bi,Sb,As,Cd in recent mollusk shells and factors affecting their distribution and deposits collected from various depths in the southern and southwestern parts of the Marmara Sea are investigated.The distribution of the elements in the shells is categorized into four groups.Of these,concentrations of 12 elements(As,Bi,Cd,Co,Ga,Mo,Nb, Sb,Se,Sc,W and Yb)are below zero [(0.053-0.79)×10~(-6)];concentrations of seven elements(Cr,Ni, Pb,V,Y,Zr and Cu)are(1.0-6.0)×10~(-6);concentrations of four elements(Ti,Mn,Ba and Zn)are 10- 20×10~(-6);and concentrations of five elements(Si,Al,Fe,Mg and Sr)are(47.44-268.11)×10~(-6).The taxonomic characteristics of the 29 elements were studied separately in mollusk shells such as Chamalea gallina(Linné),Pitar-rudis(Poll),Nassarius reticulatus(Linné),Venerupis senescens (Coocconi),Mytilus galloprovincialis(Lamarck),Mytilaster lineatus(Gemelin in Linné)and Chlamys glabra.It was found that,in mollusk taxonomy,the elements have unique values.In other words, element concentrations in various mollusk shells depend mainly on the taxonomic characteristics of mollusks.In various bionomic environments different element distributions of the same species are attributed to the different geochemical characters of the each environment.Data obtained in this study indicate that the organisms are the most active and deterministic factors of the environment. 相似文献
16.
贝类种质资源保护研究进展 总被引：5，自引：0，他引：5
种质资源保护是保护生物学的重要内容之一。保护贝类种质资源，是使我国贝类养殖业健康持续发展的可靠保障。本文根据国内外近年的研究成果，对种质资源保护的方式、生物技术在贝类种质资源保护中的应用进行了综述，并展望了今后的发展趋势。 相似文献
17.
现代砗磲壳体锶同位素与其生活环境的关系 总被引：1，自引：0，他引：1
对来自西沙群岛的双壳类磷砗壳体沿着其生长纹取样并系统地作了锶同位素的分析,得出了该生物壳体的锶同位素生长变化曲线。我们发现鳞砗磲壳体的锶同位素生长曲线显示出周期性的变化,与生物体的生长周期相一致,产生这种现象的因素主要是沿岸大陆河流排放量年同期性的变化。 相似文献
18.
辽宁省近岸海域水质生物指标及变化趋势分析 总被引：1，自引：0，他引：1
2002年8月以来,对辽宁省沿岸经济贝类进行了抽样调查,并对近岸海域水质生物指标及变化趋势进行了分析。结果表明,一些地区沿岸贝类有害物残留量较高．水生生物表现为轻污染趋势。 相似文献
19.
Increasing evidence indicates that transforming growth factor β(TGF-P) signaling pathways play many important roles in the early development of mollusks.However,limited information is known concerning their detailed mechanisms.Here,we describe the identification,cloning and characterization of two Smad genes,the key components of TGF-P signaling pathways,from the Pacific oyster Crassostrea gigas.Sequence analysis of the two genes,designated as cgi-smad1/5/8 and cgi-smad4,revealed conserved functional characteristics.The two genes were widely expressed in embryos and larvae,suggesting multiple roles in the early development of C.gigas.The mRNA of the two genes aggregated in the D quadrant and cgi-smad4 was highly expressed on the dorsal side of the gastrula,indicating that TGF-P signaling pathways may be involved in dorsoventral patterning in C.gigas.Furthermore,high expression levels of the two genes in the shell fields of embryos at different stages suggested important roles for TGF-P signaling pathways in particular phases of shell development,including the formation of the initial shell field and the biomineralization of larval shells.The results of this study provide fundamental support for elucidating how TGF-P signaling pathways participate in the early development of bivalve mollusks,and suggest that further work is warranted to this end. 相似文献
20.
深圳市潮间带动物体内的重金属含量 总被引：1，自引：0，他引：1
2005年12月和2006年5月调查了深圳海岸潮间带动物体内的重金属含量.结果表明,动物体内重金属Cr、Mn、Fe、Co、Ni、Cu、Zn、As、Se、Mo、Pb、Cd、Sn、Sb、Ba和Hg的平均含量分别为0.63、9.24、137.22、0.13、1.46、97.36、283.77、1.96、0.49、0.27、0.68、0.62、0.28、0.01、1.23和0.01mg·kg-1(湿重).采用中国海岸带污染综合调查技术组推荐使用的海洋生物污染评价标准以及贾晓平等提出的污染评价标准参考值,结果表明深圳潮间带软体动物体内的Cu、Zn超标较为严重,其中牡蛎的Cu、Zn超幅分别达到5.27和9.05倍.所有样品中的Cr、Ni、Pb和Hg都没有超标,而As则全部超过人类食用限量标准,部分样品如疣荔枝螺Thais clavigera的超幅达5.63倍.分析表明,深圳市潮间带软体动物Cu含量超标源自珠江口、深圳湾及大鹏湾海水中的Cu超标,而所调查动物中Zn和As的超标原因有待进一步研究. 相似文献