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261.
A new family of thrips, Moundthripidae, is described on the basis of a new genus and species, Moundthrips beatificus, from Early Cretaceous Lebanese amber. This taxon has plesiomorphic prognathous mouthparts, a unique type of wing venation and the main apomorphies of the Thysanoptera of the legs and mouthpart structures, suggesting that they were acquired very early during the evolution of this order. 相似文献
262.
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264.
A new Late Pennsylvanian species of gymnospermous fossil wood, Zalesskioxylon xiaheyanense sp. nov. is described from the Lower Taiyuan Formation (Stephanian B-C) near the village of Xiaheyan, Ningxia Hui Autonomous Region, northwestern China. The specimen consists only of silicified secondary xylem. The tracheids are pycnoxylic with 2–3 seriate bordered pits, arranged in subcircular or hexagonal alternate (araucaroid) pattern. The pores of the pits are small, linear, and regularly tilted. Xylem rays are homogeneous, uniseriate, 1–25 cells high. Cross-fields are filled with numerous mixed simple pits of various sizes. Growth rings, axial parenchymatous elements and resin canals are absent. The geographic distribution of Zalesskioxylon woods is reviewed. Zalesskioxylon xiaheyanense sp. nov. grew at low latitudes, and because of the lack of growth rings, probably lived under relatively uniform climatic conditions. Our new species supplements the poorly known distribution of Carboniferous wood in China. 相似文献
265.
Lake Hayward, Western Australia, is a pristine, monomictic coastal lake with a residual brine (depth=1.5 m) of 200 gL−1: stratification in winter (May to October) followed the input of ground water and rain. The epilimnion had temperature ranges
of 10–30°C, and salinity from 65–110 g L−1. Maximum depth in winter was 2.4 m. The population structure of the brine shrimpArtemia parthenogenetica, the dominant metazoan grazer in Lake Hayward, was studied from September, 1989, to February, 1991. The L. Hayward population
ofA. parthenogenetica is predominantly ovoviviparous with little recruitment into the adult population. Cyst production occurs in summer, and there
was evidence for recruitment from cyst hatching in the winters of 1989 and 1990. Nauplii were continuously present throughout
the study period. Nevertheless, recruitment through to adult stages as defined by the presence of gravid females occurred
only twice: in October–December, 1989 and in December, 1990. Based on limited observations of long-term survival of laboratory
cultures, we believe that the major mechanism controlling nauplius survival and recruitment ofArtemia in Lake Hayward is food quality and quantity. 相似文献
266.
采用水生毒理联合效应相加指数法,比较了久效磷、辛硫磷、敌敌畏以及对硫磷的单剂和混合剂对扁藻的急性毒性和联合毒性。结果表明:久效磷和辛硫磷的联合毒性为协同作用;久效磷和敌敌畏的联合毒性为拮抗作用;久效磷和敌敌畏和对硫磷的48h联合毒性为协同作用,72h、96h则为拮抗作用。 相似文献
267.
紫球藻胞外多糖抗辐射的生物学活性研究 总被引:10,自引:0,他引:10
研究了单细胞红藻紫球藻(Porphyridium sp.)对^60Coγ-射线辐射后小鼠免疫功能的影响。紫球藻胞外多糖(Plysaccharide of Porphyridium sp.PSP)在体内对小鼠免疫功能具正调节作用,具体表现为显著提高小鼠脾细胞增殖水平,自然杀伤(Natural Killer Cell,NK细胞)杀伤活性和白细胞介素2(Interleukin 2,IL-2)活性。IL-2可以激活T细胞,增强NK细胞的活性,改善^60Coγ-射线辐射引起的免疫功能低下而对机体造成的不利影响,使小鼠的免疫功能达到甚至超过正常水平。 相似文献
268.
光照对东海赤潮高发区春季硅藻生长的影响 总被引:7,自引:0,他引:7
2005年3月在东海赤潮高发区的ZA3和ZC18b站通过现场培养探讨了光照对东海硅藻生长和演替的影响。培养期间,ZA3站优势种为中肋骨条藻,没有发生演替现象;ZC18b站,当光照低于6.7MJ.m-2.d-1,由角毛藻演替为中肋骨条藻,光照高于6.7MJ.m-2.d-1,角毛藻为第一优势种,浮动弯角藻为第二优势种。Logistic生长模型可以很好地描述不同光照下硅藻的生长状况,其拟和系数为0.92±0.03。终止生物量以及优势种生长速率与光照的关系表明,温度13.0℃左右,中肋骨条藻的最适生长光照为5.0MJ.m-2.d-1,角毛藻sp.和浮动弯角藻的最适生长光照均为6.7MJ.m-2.d-1。在富营养化条件下,光照是影响硅藻生长和演替的因子。 相似文献
269.
General nutrient components including moisture, ash, crude protein, lipid and carbohydrate, inorganic elements, photosynthetic pigments, amino acids and fatty acids of Bangia sp. were analyzed and compared with Porphyra yezoensis. The results indicated that the content of protein, total amino acids and free amino acids accounted for 47.2% , 42.6% and 3.3% in dried Bangia sp. , respectively, all essential amino acids were present in relatively high levels and desirable composition. Lipid was 1.8%, in which the eicosapentaenoic acid (EPA) reached 50.5% . In per 100 g dried material, the content of chlorophyll, carotenoids, phycoerythrin and phycocyanin accounted for 766, 208, 4 600 and 2963 mg, respectively. Inorganic elements necessary for human body were found to be abundant in Bangia sp. The results showed that the nutritive value of Bangia sp. was the highest among algae reported so far, and the industry of Bangia sp. was provided with significant economic importance and developing potential. 相似文献
270.