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通过观察栉江珧 (Atrina pectinata linnaeus)的未分化生殖细胞 ,精原细胞和卵原细胞 ,精母细胞和卵母细胞 ,精子和卵子的形态结构与分布状况及核仁在卵成熟过程中的变化 ,对栉江珧生殖细胞发生及成熟过程的有关问题进行了探讨。 相似文献
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太平洋牡蛎受精过程中的精核扩散与成熟分裂 总被引：27，自引：2，他引：25
光镜下观察了太平洋牡蛎受精过程中的原核形成和成熟分裂。受精前,卵子处于第一次成熟分裂前期（即生发泡阶段）。精子入卵后开始进行成熟分裂,过程如下：（1）生发泡破裂前精核只进行轻微增大。（2）生发泡破裂,精核迅速去致密,体积迅速增大。（3）第一次成熟分裂结束,精核扩散速度减慢,核内染色体致密环状结构。（4）第二次成熟分裂结束,精核膨胀到最大程度。（5）两性原核形成,准备进行第一次卵裂。在整个受精过程中,核仁一直存在,其体积逐渐减小;有多精入卵并有多个精原核同时形成的现象。 相似文献
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波纹巴非蛤Paphia undulata精子发生的超微结构 总被引：8，自引：0，他引：8
本文在超微结构水平上,研究波纹巴非蛤精子发生过程中细胞形态结构的变化和细胞器的演变规律,以及成熟精子的形态结构。观察到精细胞核形态变化的特点和线粒体演变过程。尤其是精细胞变态过程中顶体的形成和中心体的移动。精子为典型的初生型。本文还讨论了双壳类成熟精子核型变化的种属间的差异。 相似文献
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为了探讨鱼类性腺发育成熟规律和卵母细胞成熟过程中激素的调节问题,过去进行了许多性腺发育组织学、细胞学以及组织化学等方面的研究,最近几十年来,应用电镜、免疫、质谱和分子生物学等先进技术对上述问题进行了更深入的研究,并获得了迅速进展[1~2].Nagahama[3]首先采用高体方法研究硬骨鱼类性腺类固醇激素的来源,这一技术已被广泛应用于探讨鱼类卵母细胞成熟和排卵过程中激素的作用问题,而且已被认为是一种可靠和有效的方法. 相似文献
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本文报道了在注射促性腺激素和促黄体素释放素类似物诱导鲻鱼卵母细胞成熟过程中,其胞质中高尔基体、油球数量和核的形态均发生显著变化,并据此分析了这两种激素在诱导鲻鱼卵母细胞成熟中的作用机理。 相似文献
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于1979年3－6月和1980年4—10月在东海北部获取了带鱼生殖鱼群。采用宏观和组织学方法，对2866个样本的雄鱼成熟状况进行鉴定和分析。结果表明，肛长在130－140mm，体重在20－40g的个体开始性成熟；肝长180mm以上和体重100g左右个体基本全部性成熟。当年早生群50％以上达到性成熟，翌年春季全部成熟；晚生群到翌年4月出现少量成熟个体，秋季全部成熟。雄带鱼一个世代的成熟过程在半年或一年中即可完成。 相似文献
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方斑东风螺性畸变现象的解剖学和组织学研究 总被引：1，自引：0，他引：1
以解剖学和组织学方法研究了方斑东风螺未成熟和成熟的正常雌、雄个体以及性畸变个体的生殖系统结构.性畸变个体除具有正常的雌性器官外,还有输精管或阴茎.在正常雄性输精管的个体发育过程中再现了系统发育的过程,而且在性畸变个体输精管的形成过程和发育过程中组织学结构特征的变化与正常雄性输精管的个体发育过程的相似.性畸变雌体的性腺发育受阻.目前,性畸变现象仅存在于成熟个体,但这并不表明未成熟个体中不会发生性畸变现象.具有较高食用价值的方斑东风螺因有机锡污染可能会对人类健康不利,应引起人们的关注. 相似文献
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采用石蜡切片法,对分布于粤西沿海的斗嫁蜮Cellana grata(Gould)的精子发生和雄性性腺的组织结构进行了研究。斗嫁蜮精子发生经历雄性性细胞的增殖、生长、成熟、变态等阶段.依据精子发生过程中生精细胞形态的变化,精子发生过程可分为精原细胞期、初级精母细胞期、次级精母细胞期、精细胞期和精子形成期等5期。雄性性腺组织主要由滤泡构成,滤泡为生殖细胞增殖、生长、成熟、变态的场所,滤泡腔中的精子经生殖输送管向外输送。显微观察与分析表明:(1)精子发生中,生长期不明显,初级精母细胞较精原细胞小;(2)生精细胞及核的大小随发育逐渐变小,核嗜碱性逐渐增强;(3)精子发生过程中的变态期长,易观察到变态过程中的不同形态的精细胞;(4)成熟精子为鞭毛型,头部短杆状,约0.5×(3~4)μm,尾部细长呈鞭毛状;(5)生长-成熟期的雄性性腺由形态较规则的(多边形)滤泡构成,滤泡界限清晰;(6)雄性滤泡壁由不同发育时期的生精细胞依次排列,较原始的生精细胞呈嗜酸性,靠近滤泡膜分布,而发育晚期的生精细胞呈嗜碱性,渐离滤泡膜分布,成熟精子群集并呈涡旋状分布于腔中;(7)成熟雄性性腺可伸入足部或肝组织中;在肝组织切片中,可观察到结构不同的4个级别的生殖输送管;8)斗嫁蜮雌雄异体,但存在雌雄同体、性转化现象。还对斗嫁蜮精子发生与成熟过程及雌雄同体的有关问题进行了探讨。 相似文献
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Chandralata Raghukumar G. Sheelu P. A. Loka Bharathi Shanta Nair C. Mohandass 《Marine Georesources & Geotechnology》2001,19(1):1-16
In order to assess the impact of deep-sea mining on the in situ benthic life, we measured the microbial standing stock and concentration of organic nutrients in the deep-sea sediments of the Central Indian Ocean Basin in the Indian pioneer area. Sediments were collected using box core and grab samples during September 1996. The total bacterial numbers ranged from 10 10 -10 11 cells per g -1 dry weight sediment. There was a marginal decrease in the number of bacteria from surface to 30 cm depth, though the subsurface section registered a higher number than did the surface. The highest numbers were encountered at depths of 4-8 cm. The retrievable number of bacteria were two orders less in comparison with the direct total counts of bacteria. An almost homogeneous distribution of bacteria, total organic carbon, living biomass, and lipids throughout the depth of cores indicates active microbial and benthic processes in the deep sea sediments. On the other hand, a uniform distribution of total counts of bacteria, carbohydrates, and total organic carbon in all the cores indicates their stable nature and suggests that they can serve as useful parameters for long-term monitoring of the area after the benthic disturbance. Further studies on temporal variability in this region would not only verify the observed norms of distribution of these variables but would also help to understand restabilization processes after the simulated benthic disturbance. 相似文献
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Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
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Derek V. Ellis 《Marine Georesources & Geotechnology》2001,19(1):51-63
This article reviews information recently available from existing marine and coastal mining for responses to environmental issues affecting marine mining at different depths. It is particularly but not exclusively concerned with those issues affecting seabed biodiversity impact and recovery. Much information has been gathered in the past 10 years from shallow mining operations for construction aggregate, diamonds, and gold, from coastal mines discharging tailings to shallow and deep water, and from experimental deep mining tests. The responses to issues identified are summarized in a series of eight tables intended to facilitate site-specific consideration. Since impacts can spread widely in the surface mixing layer SML, and can affect the biologically productive euphotic zone, the main issues considered arise from the depth of mining relative to the SML of the sea. Where mining is below the SML, the issue is whether it is environmentally better to bring the extraction products to the surface vessel for processing (and waste discharge), or to process the extraction products as much as possible on the seabed. Responses to the issues need to be sitespecific, and dependent on adequate preoperational environmental impact and recovery prediction. For deep tailings disposal from a surface vessel, there are four important environmental unknowns: (1) the possible growth of "marine snow" (bacterial flocs) utilizing the enormous quantities of fine tailings particles (hundreds or thousands of metric tons per day) as nuclei for growth, (2) the possibility that local keystone plankton and nekton species may migrate diurnally down to and beyond the depth of deep discharge and hence be subjected to tailings impact at depth, (3) the burrow-up capability of deep benthos and their ability to survive high rates of tailings deposition, and (4) the pattern and rate of dispersion of a tailings density current through the deep water column from discharge point to seabed. Actions to obtain relevant information in general and site-specifically are suggested. 相似文献
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G. Parthiban 《Marine Georesources & Geotechnology》2000,18(3):223-235
Particle fluxes were measured 7 m above the sea bottom during the predisturbance, disturbance, and postdisturbance periods by using time series sediment traps attached to seven deep-sea moorings deployed in the INDEX experiment site in the Central Indian Basin. The predisturbance particle fluxes varied between 22.3 to 55.1 mg m -2 day -1 . Increased and variable particle fluxes were recorded by the sediment traps during the disturbance period. The increase observed was 0.5 to 4 times more than the background predisturbance fluxes. The increases in particle fluxes (~4 times) recorded by the sediment trap located in the southwestern direction (DMS-1) were the greatest, which could be the result of preferential movement of resuspended particles generated during the deep-sea benthic disturbance along the general current direction prevailing in this area during the experimental period. Also, the traps located closer to the disturbance area recorded greater fluxes than did the traps far away, across the Deep Sea Sediment Resuspension System path. This variability in recorded particle fluxes by the traps around the disturbance area clearly indicates that physical characteristics such as grain size and density of the resuspended particles produced during the disturbance had an important effect on particle movement. The postdisturbance measurements during ~5 days showed a reduction in particle fluxes of ~50%, indicating rapid particle settlement. 相似文献
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海上大直径钢管桩打桩过程中,桩周土体受到强烈扰动而发生强度弱化,掌握桩周土体强度弱化规律对于准确预测打桩过程、保证工程安全具有重要意义。为研究土体强度弱化规律,开展了环剪试验模拟打桩对桩周土体的扰动,测试土体强度随剪切速率的变化规律,建立了描述土体强度弱化规律的拟合公式,引入到打桩分析软件中。研究结果表明：土体的强度折减程度不仅与土体本身的性质有关还受到土体的埋深和剪切速率的影响,埋深越深土体强度折减程度越低,剪切速率越高土体强度折减越高,在打桩分析中可采用这里推荐的线性折减方法来模拟不同深度处土体强度的折减规律。 相似文献
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Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification
An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm. 相似文献
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The advanced piston corer (APC) has been used by the Ocean Drilling Program since 1985 for recovering soft sediments from the ocean floor. The pullout force measured on extracting the core barrel from the sediment is shown to correlate with the average shear strength of the sediment core measured in the ship's laboratory. A simple rule of thumb is derived relating the shear strength of the sediment to the pullout force. Multiple APC holes at individual sites allow the consistency of the pullout measurements to be assessed. The effects of different operational procedures during APC coring are also explored. Although generally applicable, the correlation between pullout force and laboratory measurements of shear strength breaks down for some APC holes, possibly because of the disturbance of some sediment types during the APC coring process. A better understanding of the physical process of APC coring, and its effect on the properties of the sediment both inside and immediately outside the core barrel, would indicate what confidence can be put on the measurement of pullout force as a way of evaluating the in situ shear strength of deep sea sediments. 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
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The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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