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81.
Twelve Galaxias postvectis (shortjaw kokopu) and four G. fasciatus (banded kokopu) spawning sites were found on the margins of the Katikara Stream, Taranaki, New Zealand. This is the first time G. postvectis spawning sites have been documented. G. fasciatus spawning sites discovered in this study confirm previous observations elsewhere in New Zealand. These spawning sites were all found out of water, variable distances from the base flow water level amongst stony substrate, vegetation, and debris. Most G. fasciatus appeared to lay their eggs, and subsequently hatch, c. 3 weeks earlier than G. postvectis, which spawned from 9 to 17 May 2001. G. brevipinnis (koaro) larvae were also identified drifting downstream in late May and mid June 2001. Deposition of eggs and subsequent hatching were found to be associated with elevated flows. 相似文献
82.
STUDY ON MIXIS POTENTIAL OF ROTIFER RESTING EGGS( BRACHIONUS PLICATILIS ) WITH DIFFERENT COLLECTION TIMES AND DIFFERENT PRESERVATION PERIODS 总被引:1,自引:0,他引:1
The present study investigated the possible changes in the mixis potential of rotifer resting eggs produced by a single stock of Brachionus plicatilis and collected and preserved annually from 1985 - 1998. Several clones derived from each batch of resting eggs were cultured under the same conditions for 21 days. The percentage of clones appearing resting eggs and the average yield of resting eggs produced from each clone were recorded and statistically analyzed to find the differences between the mixis potential of those resting egg batches. Results showed that different batches of resting eggs had different mictic levels among their descendent clones; but no regular relationship was found between the mixis potential of resting eggs and their collection times/preservation periods. Several internal and external factors that might affect the mixis potential of resting eggs were discussed. 相似文献
83.
瓯江口树排沙湿地不同生境大型底栖动物群落多样性研究 总被引:1,自引:0,他引:1
为了解瓯江口树排沙湿地不同生境大型底栖动物群落多样性,于2014年10月至2015年6月对红树林、互花米草及光滩3种生境开展大型底栖动物调查。共鉴定出大型底栖动物48种,隶属于5纲15目31科40属。大型底栖动物年平均栖息密度和生物量,红树林生境最高,互花米草生境次之,光滩生境最低。采用物种多样性指数和G-F多样性指数分析不同生境大型底栖动物群落多样性,发现红树林生境大型底栖动物的多样性高于互花米草生境和光滩生境。单因素方差分析表明:物种数、栖息密度、生物量及物种多样性季节间差异不显著,而物种数、Shannon-Wiener多样性指数与Margalef物种丰富度指数生境间差异显著。人工恢复红树林有助于提高大型底栖动物群落的多样性。 相似文献
84.
We consider a scenario where the interior spacetime, described by a heat conducting fluid sphere is matched to a Vaidya metric
in higher dimensions. Interestingly we get a class of solutions, where following heat radiation the boundary surface collapses
without the appearance of an event horizon at any stage and this happens with reasonable properties of matter field. The non-occurrence
of a horizon is due to the fact that the rate of mass loss was exactly counterbalanced by the fall of boundary radius. Evidently
this poses a counter example to the so-called cosmic censorship hypothesis. Two explicit examples of this class of solutions
are also given and it is observed that the rate of collapse is delayed with the introduction of extra dimensions. The work
extends to higher dimensions our previous investigation in 4D. 相似文献
85.
86.
ZHANG Xianqiu Lü Junchang BIAN Geguo QIU Licheng HUANG Dong YUAN Weiqiang China New Star 《《地质学报》英文版》2005,79(5):598-604
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
87.
比较在0、5、10、15、20、25、30(自然海水)、35、40、45、50等11个盐度梯度下,菊黄东方鲀(Takiugu flavidus)的受精卵发育和仔鱼生长情况,测定仔鱼的不投饵存活系数(SAI).结果表明:1)菊黄东方鲀受精卵在盐度0~50范围内均可孵化,最适盐度20~25.盐度(x)与孵化时间(y)呈正相关关系,表达式为:y=0.345 x+141.1,R2=0.956.2)实验盐度范围内,菊黄东方鲀仔鱼SAI值为1.55~30.10.3)在盐度5~45条件下,仔鱼皆可存活,存活率为3%~27%.其中,在10~30盐度下存活率较高,为20%~27%.经15 d的培育,仔鱼平均全长为6.28~7.34 mm.低盐度对菊黄东方鲀仔鱼生长更有利,在15~20盐度条件下,仔鱼生长较好,最终平均全长为7.30~7.34 mm.4)根据SAI值和生长状况,仔鱼生长和存活的适宜生长盐度为10~30,最适盐度范围为15~20. 相似文献
88.
Louis D. Zeidberg John L. Butler Darlene Ramon Anthony Cossio Kevin L. Stierhoff Annette Henry 《Marine Ecology》2012,33(3):326-336
Like many other loliginid squid, Doryteuthis (Loligo) opalescens deposits egg cases on the ocean floor. Depending upon temperature, egg cases may persist for 5–12 weeks before the paralarvae hatch. Because of this relatively long duration and squid’s pelagic life history, egg cases provide a practical life stage to survey. During 2001–2002, squid egg beds in Monterey Bay, Carmel Bay, and around the California Channel Islands were surveyed using a remotely operated vehicle with the goal of delineating the habitat of egg beds that are spawned during active commercial fishing. Egg cases were highly aggregated and densities reached 1338 capsules m−2. Squid eggs were significantly shallower in Central California. Egg cases occurred between 20 and 93 m around the Channel Islands, and in Central California they were between 13 and 61 m. The temperatures in both regions were similar (10–12 °C), with some eggs in Southern California found up to 14.4 °C. Ninety-five percent of eggs were found on sand, suggesting that temperature and substrate are stronger behavioral cues than depth to stimulate spawning. Suitable spawning habitat was defined by three criteria: sandy benthic substrate, temperatures between 10 and 14.4 °C, and depths between 20 and 70 m when the first two criteria hold. Additionally, within this defined area, oxygen concentration is quantified. The greatest commercial landings of market squid occur in both Central and Southern California during a time of year when water temperatures of 10–12 °C are prevalent in the 20–70 m depth range. 相似文献
89.
YuJiao Wang ZhangDong Jin Ling Zhou FuChun Li Fei Zhang LiuMei Chen XinNing Qiu RuGui Qi 《中国科学:地球科学(英文版)》2014,57(10):2512-2521
Otoliths are biogenic carbonate minerals in the inner ear of teleost fish, whose compositions can record the physical and chemical conditions of the ambient water environment inhabited by individual fish. In this research, the fishbones and otoliths of naked carp sampled near the Bird Island, offshore Lake Qinghai, were dated and analyzed for mineralogy and microchemical compositions. Comparing the microchemical compositions of ancient otoliths with those of modern otoliths, we conclude that the ancient naked carps inhabited a relict lake formed when the lake shrank from a high lake level, by combining with the AMS-14 C ages of fishbones and otoliths, the stratigraphy and surrounding topography of the sample site. AMS-14 C dating results of ancient fishbones and otoliths show that these naked carps lived from 680 to 300 years ago, i.e. during the Ming Dynasty of China. The X-ray diffraction(XRD) patterns demonstrate that the ancient lapillus is composed of pure aragonite, identical to modern one, indicating that the mineral of lapillus didn't change after a long time burial and that the ancient lapillus is suitable for comparative analysis thereafter. Microchemical results show that both ratios of Mg/Ca((70.12±18.50)×10?5) and ? 18O((1.76±1.03)‰) of ancient lapilli are significantly higher than those of modern lapilli(average Mg/Ca=(3.11±0.41)× 10?5 and ? 18O=(?4.82±0.96)‰). This reflects that the relict water body in which the ancient naked carp lived during the Ming Dynasty was characterized by higher Mg/Ca and ? 18 O ratios than modern Lake Qinghai, resulting from strong evaporation after being isolated from the main lake, similar to today's Lake Gahai. Based upon the stratigraphy and altitude of naked carp remains, it can be inferred that the altitude of lake level of Lake Qinghai reached at least 3202 m with a lake area of 4480 km2 during the Ming Dynasty, approximately ~5% larger than it is today. 相似文献
90.
鄂尔多斯盆地奥陶系岩溶储层控制因素分析 总被引:10,自引:3,他引:7
鄂尔多斯盆地奥陶系岩溶储层演化经历了多期次的叠加。根据古岩溶的演化期次,分别编制了奥陶系地层厚度图、前石炭纪岩溶古地貌图及奥陶系顶面构造图。结合岩溶发育机理,系统分析了各个阶段岩溶储层发育的控制因素,进而综合预测了岩溶储层发育的有利区带,为奥陶系的油气勘探指出了有利方向。同沉积期,鄂尔多斯盆地存在伊盟古隆起、中央古隆起和韩城古隆起,这3个隆起带共同控制着岩溶储层的发育,隆起的鞍部、斜坡带以及坳陷中的微隆起带是岩溶储层发育的有利地区;裸露风化壳期,古岩溶地貌和古沟槽的展布是岩溶储层发育的主控因素,古岩溶坡地为岩溶作用的进一步发生创造了条件;埋藏期,奥陶系顶面起伏形态始终处于中部高、东西低,中部隆起与东部坳陷之间存在一陡坡带,中部隆起带为压释水运聚的有利方向,而陡坡带为压释水的强烈转换区,这一特征决定了岩溶储层的最终分布。因而,同沉积期隆起斜坡带、裸露风化壳期岩溶坡地以及埋藏期陡坡带的叠加位置将是岩溶储层发育的有利区域。 相似文献