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81.
The red beds of the northern Heyuan Basin (Guangdong Province, China) are more than 4,000 m thick. Based on the lithological characters, in ascending order these beds are divided into the Dafeng Formation, Zhutian Formation, and Zhenshui Formation of the Nanxiong Group, Shanghu Formation and Danxia Formation. The Nanxiong Group with relatively mature coarse clastic rocks attains about 2940 m in thickness. The Dafeng Formation is 837 m thick, consisting of conglomerates and sandy conglomerates; the Zhutian Formation, which is 1.200 m thick, consists of purplish red sandstone with gravels, poorly sorted sandstone, feldspathic quartzose sandstone banded granular conglomerate, siltstone, and sandy mudstone. The Zhutian Formation is rich in calcareous concretions. Heyuannia (Oviraptoridae) and turtle fossils were found in this formation. The Zhenshui Formation deposited to a thickness of 900 m consists of coarse sediments, including granular conglomerate, and gravelly sandstone with well developed cross-beddings; the Shanghu Formation, which is 820 m thick, consists of purplish red granular conglomerate coarse sandstone intercalated with fine si~tstone; the Danxia Formation characterized by the Danxia ~andform is composed of coarse c~astic gravels and sandy gravels. The lower part of the Nanxiong Group whence dinosaur eggs and derived oviraptorosaurs come, belongs to the Late Cretaceous. No fossils are found in the Shanghu Formation or the Danxia Formation, but their stratigraphic order of superposition on the Nanxiong Group clearly shows their younger age.  相似文献   
82.
Two closely associated egg types occur at the same locality in the Upper Cretaceous (Maastrichtian) St. Mary River Formation in north central Montana. These specimens represent the first fossil eggs described from this formation. At least fifteen small ovoid eggs or egg portions are scattered through a 25 cm interval of rock. Five significantly larger, round eggs overlie these smaller eggs and are in close proximity to one another on a single bedding plane. The best preserved egg of the smaller size measures 36 mm × 62 mm and exhibits the prismatic, two-layered eggshell structure of a theropod egg. The dispersed distribution and inconsistent angles of these small eggs likely resulted from disturbance by subsequent nesting activity and/or possibly nest predation. At least twelve additional small prismatic eggs also occur at this site. We assign the small eggs as a new oogenus and oospecies, Tetonoolithus nelsoni, within the Prismatoolithidae. The large round eggs measure 130 mm in diameter and the eggshell displays substantial diagenetic alteration. These eggs likely belonged to a hadrosaur due to their similarity in egg size, shape, and eggshell thickness to Maiasaura eggs from the stratigraphically lower Two Medicine Formation. Eggs at different stratigraphic levels at this site indicate that conditions favorable to both dinosaur species persisted for an extended period of time. However, determining whether these dinosaurs occupied the nesting site at the same or different years remains beyond the resolution of the rock record.  相似文献   
83.
Many estuarine and coastal planktonic copepods depend on the hatching of benthic resting eggs for recruitment of nauplii to the water column population. The distribution and abundance of viable resting eggs of Acartia pacifica in the Xiamen Bay were determined by the presence of nauplii in the laboratory. The number of viable eggs varied temporally and spatially. The maximum number (9.2×104m-2) of viable eggs was in summer. In spring the average abundance of viable eggs was 5.6×104 m-2. The abundances of viable eggs in fall and winter were similar, respectively 2.7×104 and 3.3×104 m-2, which were the lowest in the year. The numbers of viable eggs inside the stations of the Xiamen Bay were higher than those outside the stations. The viable eggs were found at all depths (0~10 cm),although not in every station. The maximin number did not necessarily occur in the uppermost centimeter of the sediments but often occurred several centimeters below the water-sediment interface. The accumulation of viable eggs in the seabed of a subtropical bay constitutes a potential source of recruitment of nauplii into the pelagic population.  相似文献   
84.
蒋玫  王云龙 《海洋与湖沼》2007,38(4):351-355
采用1999年6—8月间在东海(26°30′—32°30′N、121°00′—128°00′E)的日本鲭和鱼卵仔鱼综合调查资料,对鱼卵仔鱼的数量分布的生态特征进行分析,并就平面分布与水文环境的关系进行了初步探讨。结果表明,鱼卵分布范围较仔鱼要大,高值区主要出现在南部近海的鱼外渔场,鱼仔鱼则在近海的长江口外渔场分布较多。日本鲭仔鱼的摄食对水温盐度的要求较亲鱼产卵的水文环境要严格许多,鱼产卵受水温和盐度的影响控制较仔鱼的育肥更为显著。两种鱼卵仔鱼数量平面分布状况与黄海冷水、江浙沿岸流、台湾暖流以及黑潮在本区运动消长而产生的温、盐变化存在着密切关系,日本鲭和鱼的鱼卵数量随着浮游动物丰度减少而逐渐增加,鱼仔鱼的数量则随着浮游动物丰度的增加而增加,浮游生物饵料生物的变动对鱼卵仔鱼的分布也有一定的影响。  相似文献   
85.
Data collected in 1953 and 1954 by the U.S. Fish and Wildlife Service were statistically analyzed to ascertain where and when fish eggs and larvae are most abundant on the southeastern U.S. continental shelf. The results are related to some oceanographic processes that might affect the survival of larval fish. Along-shelf differences in numbers of eggs and larvae are minimal compared with differences that occur across the shelf. Highest numbers of fish larvae are found on the outer shelf during fall, winter and spring, but larvae are evenly distributed across the shelf in summer.Upwelling strongly influences the dynamics of plankton production on the outer shelf, and thus during most seasons of the year upwelling may be the most important process controlling the amount of food available to larval fish. During winter and spring, mean winds do not favor shoreward transport of larval fish from the outer shelf if the larvae are located in near-surface waters. Thus, during these seasons variability of winds on the ‘event’ time scale may be more important to onshore and offshore transport of larval fish than the mean strength and direction of monthly or seasonally averaged winds.  相似文献   
86.
几种药物对中国对虾卵子的消毒试验   总被引:4,自引:0,他引:4  
本文试验了几种药物对中国对虾卵子表面细菌的杀灭力以及卵子对消毒药物的耐受力。试验结果表明,利用适当浓度的药物对卵子消毒可以消除病原体的来源和传播途径,减少对虾育期各种疾病的发生而又不致于对卵子的孵化率产生显著影响。  相似文献   
87.
韩向娜  赵文华  陈熜  蒋顺兴  汪筱林 《地质论评》2021,67(6):67120002-67120002
翼龙骨骼及其蛋与胚胎化石对研究翼龙生殖和胚胎发育方面具有重要意义。在哈密戈壁发现的一件超过200枚翼龙蛋、胚胎和骨骼三位一体保存的哈密翼龙化石标本从极干旱强盐碱的戈壁滩搬运至相对潮湿的环境后,就会发生明显的风化破碎,表现为由外向内逐渐蚕食性风化,富含骨骼/蛋化石的区域风暴岩快速发生崩解,造成化石脱落,不含化石的区域砂岩情况稳定。针对在同一件标本上发生差异风化的现象,本文利用PLM、XRD、MIP、IC、Raman、FTIR、SEM- EDS等多种分析方法,对出现风化的围岩与稳定区域围岩进行对比研究,探寻出现不同风化表现的原因。结果表明,风化区域围岩的黏土矿物(Ca型蒙脱石为主)含量较低,孔隙较大,孔径是稳定区域围岩的7倍以上,可溶盐含量较高,是稳定区域的约36倍,可溶盐种类以极易潮解的CaCl2和Ca(NO3)2·4H2O为主,而稳定区域围岩中可溶盐主要是NaCl和Na2SO4。通过模拟风化实验说明,造成化石标本出现差异风化的原因有以下两点,一是富集翼龙骨骼和蛋(胚胎)区域的风暴岩结构不均一、孔隙较大,结构疏松,内部胶结较弱;二是该化石区域中对温湿度变化敏感的易潮解钙盐含量较高,加之化石与围岩边界不均一性极大,与稳定区域围岩的致密均匀不同,在北京四季温湿度变化下更容易迅速风化。根据风化原因对此类标本的风化治理提出一些初步建议。本研究对发掘出的干旱地区特异埋藏的化石标本的保存及保护具有一定的指导意义。  相似文献   
88.
于2007年和2008年6月、8月,用大型浮游生物网对莱州湾鱼卵、仔稚鱼种类组成与数量分布进行了4个航次调查。结果表明,采集到11271粒鱼卵,隶属于4目、15科、22种(不包括2个未定名物种);仔稚鱼2942尾,隶属于4目、9科、12种(不包括2个未定名物种)。6月份是莱州湾大部分鱼类主要产卵期,鱼卵、仔稚鱼种类达25种,鱼卵优势种以斑(Clupanodon punctatus)和凤鲚(Coilia mystus)为主;仔稚鱼优势种以凤鲚、梭鱼(Mugil soiuy)和斑为主。8月份产卵的鱼类较少,仅采集到15种鱼卵、仔稚鱼,优势种均以凤鲚和鲈鱼(Lateolabrax japonicus)为主。鱼卵、仔稚鱼平面分布极不均匀,黄河、广利河和老弥河口附近海域数量较多,莱州湾中部海域数量较少。通过SPSS软件分析发现,鱼卵数量与仔稚鱼、表层铵盐含量呈显著正相关(r=0.438,0.604,P0.01),与盐度、透明度呈负相关(r=-0.343,-0.329,P0.05);仔稚鱼数量仅与鱼卵数量和表层铵盐含量呈显著正相关(r=0.438,0.536,P0.01),与其它环境因子没有明显相关关系(P0.05)。  相似文献   
89.
探讨对虾白斑综合症(White Spot Syndrome WSS)与虾池中桡足类之间的关系,于2003年5~10月份,在暴发过对虾白斑综合症的池塘中采集桡足类样品共128个,并从冬季底泥样品分离出桡足类休眠卵样品20个,以及此种休眠卵孵化得来的桡足类幼体样品5个。利用PCR斑点杂交法以及巢式PCR法检测样品中对虾白斑综合症病毒(White Spot Syndrome Virus WSSV)携带情况。结果表明,5~10月份桡足类样品中均能检测到阳性样品,总的阳性率为56.3%;其中,5月份样品阳性率为37.5%,6,8,9,10月份各取样1次,每次样品中的阳性率均在60%以上。在20例桡足类休眠卵样品中有1例为阳性,阳性率为5%;并且实验室中孵化此种休眠卵得来的桡足类幼体样品中检测到阳性,阳性率为40%。本研究初步表明,桡足类是WSSV的携带者或传播媒介之一,且冬季池塘底泥中携带WSSV的桡足类休眠卵可萌发出带病毒的桡足类。  相似文献   
90.
为了综合评价经济海藻羊栖菜(Sargassum fusiforme)受精卵的营养价值及开发利用前景,本文检测了羊栖菜受精卵碳水化合物、膳食纤维、氨基酸、脂肪酸等生物活性物质与矿质元素成分,并与文献报道的孢子体相应成分进行了比较。结果发现:羊栖菜受精卵富含碳水化合物、蛋白质、氨基酸及膳食纤维,其含量分别为(20.4±0.07)、(22.7±0.03)、(16.7±0.04)和(39.2±0.03)g/100g DW;谷氨酸、维生素E和β-类胡萝卜素含量尤其高,分别达到(9.82±0.05)g/100g DW、(11.8±0.01)mg/100g DW和(3.0×103±7.07)μg/100gDW;而脂肪含量偏低,只有1.03%。矿质元素中微量元素铁、钙和镁的含量较高,分别为(4.54×103±49.50)、(1.83×103±7.78)和(1.40×103±28.28)mg/100g DW。通过与文献报道的羊栖菜孢子体生化成分相比较,羊栖菜受精卵中蛋白质、氨基酸、β-类胡萝卜素、钾、钠、磷、铁、钙、锌、锰及铜元素的含量均高于羊栖菜孢子体。说明羊栖菜受精卵具有更高的天然产物提取、开发和利用价值。  相似文献   
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