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Winfried Lampert 《新西兰海洋与淡水研究杂志》2013,47(3):483-490
Laboratory studies on cyanobacteria‐zooplankton interactions have largely focused on the inadequacy of cyanobacteria as a food source. Some features of cyanobacteria can be regarded as anti‐herbivore defences. Large colonies of Aphanizomenon, Anabaena and Microcystis cannot be handled by zooplankton, but do not interfere seriously with the filtering process. Small colonies and filaments, however, may cause severe inhibition of the feeding process by mechanical interference. This reduces zooplankton growth, reproduction, and survival. Copepods, rotifers, and Bosmina are less affected by mechanical disturbance than cladocerans. If ingested, some cyanobacteria may be poorly digested or may not provide essential nutrients. Some cyanobacteria are reported to be toxic to zooplankton. Several strains of Microcystis produce an endotoxin, but the amount of toxin produced differs among strains and with the condition of Microcystis. Zooplankton encountering toxic cells cease feeding. Some evidence of an extra‐cellular herbivore deterrent was found for Anabaena. Thus, cyanobacteria may either be individually protected or may create an environment that is unfavourable for efficient grazers (e.g., Daphnia). 相似文献
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Effect of canopy openness and meteorological factors on spatial variability of throughfall isotopic composition in a Japanese cypress plantation 总被引：1，自引：0，他引：1 
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下载免费PDF全文 Xinchao Sun Yuichi Onda Akiko Hirata Hiroaki Kato Takashi Gomi Xueyan Liu 《水文研究》2018,32(8):1038-1049
Spatial variability of throughfall (TF) isotopic composition, used as tracer input, influences isotope hydrological applications in forested watersheds. Notwithstanding, identification of the dominant canopy factors and processes that affect the patterns of TF isotopic variability remains ambiguous. Here, we examined the spatio‐temporal variability of TF isotopic composition in a Japanese cypress plantation, in which intensive strip thinning was performed and investigated whether canopy structure at a fine resolution of canopy effect analysis is related to TF isotopic composition and how this is affected by meteorological factors. Canopy openness, as an index of canopy structure, was calculated from hemispherical photographs at different zenith angles. TF samples were collected in a 10 × 10 m experimental plot in both pre‐thinning (from July to November 2010) and post‐thinning (from May 2012 to March 2013) periods. Our results show that thinning resulted in a smaller alteration of input δ18O of gross precipitation, whereas the changes in deuterium excess varied in both directions. Despite the temporal stability of spatial patterns in TF amount, the spatial variability of TF isotopic composition was not temporally stable in both pre‐ and post‐thinning periods. Additionally, after thinning, the isotopic composition of TF was best related to canopy openness calculated at the zenith angle of 7°, exhibiting three different relationships, that is, significantly negative, significantly positive, and nonsignificant. Changes in meteorological factors (wind speed, rainfall intensity, and temperature) were found to affect the relationships between TF δ18O and canopy openness. The observed shifts in the relationships reveal different dominant factors (partial evaporation and the selection), and canopy water flowpaths control such differences. This study provides useful insights into the spatial variability of TF isotopic composition and improves our understanding of the physical processes of interception through canopy passage. 相似文献
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休眠卵库作为淡水枝角类生物与遗传信息的储藏库,从沉积物休眠卵库中萌发的枝角类对现生种群的数量与种群遗传结构有着直接的影响.分别采集流溪河水库盔型溞的现生种群和沉积物表层(0~10 cm)的休眠卵,扩增现生种群与休眠卵的线粒体细胞色素C氧化酶亚基I基因,构建了单倍型网络.休眠种群相比现生种群有着较高的单倍型多样性和核酸多样性,初期现生种群分别为0.562、0.00104,末期现生种群分别为0.726、0.00331,休眠种群分别为0.815、0.00761.流溪河盔型溞现生种群与休眠种群存在双向基因流,现生种群到休眠种群的有效迁移率为490.9,休眠种群到现生种群的有效迁移率为527.5.通过构建贝叶斯系统树验证了休眠种群和现有种群中并不存在隐种或者亚种的分化,休眠种群与现生种群之间没有出现较大的遗传分化,现生种群遗传多样性来自于休眠种群,水库的休眠种群更能反映种群真实的遗传多样性.休眠种群与现生种群之间的基因流与休眠卵库大小无关,与休眠卵的萌发有关. 相似文献
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表型可塑性指的是生物体在生物或非生物环境发生变化时会呈现出不同的表型能力,是生物在不稳定的生活环境中维持生存的一种主要策略.在淡水生态系统,大量研究表明浮游动物能通过捕食者释放的化学信息物质感知捕食风险的存在,从而导致反捕食的表型可塑性反应的发生.溞类是一类很好的研究浮游动物对捕食者释放的信息素产生表型可塑性反应的模式生物.本文综述了捕食者释放的化学信息素对溞类的生活史、形态特征、行为活动以及生理指标等表型的影响,探讨了其形成机制和生态意义.溞类对捕食风险信息素的表型可塑性是特定种群与捕食者长期相互作用下适应性进化产生的.加强这些研究对了解物种的形成和生物的进化有非常重要的意义. 相似文献
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有毒铜绿微囊藻对鱼和溞的毒性 总被引：7，自引：0，他引：7
用有毒铜绿微囊藻细胞及其从毒细胞中提取的毒素喂养和腹腔注射鱼类,结果表明:(1)微囊藻毒素MCYST-LR对所有实验过的鱼有毒害作用(LD50为110-500μg/kg).注射毒素24h后,鱼肝电镜超微结构观察均表现出肝损伤.(2)在受控条件下,当用有毒铜绿微囊藻作为食物喂养日鲢和罗非鱼时,鱼类能在以毒藻为唯一食物的环境中生活20d以上.白鲢和罗非鱼粪便的毒性比喂食藻类的毒性分别降低约2-4.5倍,其肝的超微结构现察仍有轻度损伤.(3)在培养液中加入15μg/mLMCYST-LR和用实验室纯培养的铜绿微囊藻作为食物培养枝角类时,均可使它们在48h死亡.以无毒微囊藻培养时则生长不良亦不怀卵,表明它不是枝角类合适的食物. 相似文献
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两种提取枝角类休眠卵基因组DNA方法的比较 总被引：2，自引：2，他引：0
休眠卵是枝角类在环境胁迫条件下通过有性生殖形成的,休眠卵的孵化对种群补充与恢复有着重要作用.沉积于底泥中的休眠卵保存了不同阶段的种群遗传信息,有效地提取枝角类休眠卵基因组DNA是进一步研究水体枝角类遗传多样性的关键环节.采用目前国际上使用的氯仿异戊醇提取法和玻璃乳提取法分别对流溪河水库底泥中表层和底层的盔型溞(Daphnia galeata)休眠卵进行基因组DNA提取的比较分析.结果显示,氯仿异戊醇提取法成功率为27.5%,平均浓度为14.25±1.84 ng/μl;玻璃乳提取法成功率为65.0%,平均浓度为28.37±2.56 ng/μl.无论是提取成功率还是提取浓度玻璃乳提取法都显著高于氯仿异戊醇提取法,且玻璃乳提取法所用试剂少,不涉及有毒试剂,操作步骤简单,整个提取过程所用时间短,玻璃乳提取法提取枝角类休眠卵基因组DNA是一种快捷实用的方法. 相似文献
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Differences in seasonality and temperature dependency of stand transpiration and canopy conductance between Japanese cypress (Hinoki) and Japanese cedar (Sugi) in a plantation 下载免费PDF全文
下载免费PDF全文 Takami Saito Tomo'omi Kumagai Makiko Tateishi Nakako Kobayashi Kyoichi Otsuki Thomas W. Giambelluca 《水文研究》2017,31(10):1952-1965
In this paper, we present an investigation of interspecies differences in transpiration of the 2 most common plantation forest tree species in Japan, both in the family Cupressaceae with different northern limits of native distribution, Japanese cypress (Hinoki; Chamaecyparis obtusa Sieb. et Zucc.) and Japanese cedar (Sugi; Cryptomeria japonica D. Don). The stem sap flow rate was measured in 2 nearby stands of similar leaf area index in a 42‐year‐old plantation. Single‐tree and stand‐scale transpiration rates (Etre and Esta, respectively) were observed during an ideal autumn environment. At the stand scale, mean sap flux density of Hinoki was greater than that of Sugi, whereas total sapwood area per ground area was smaller in Hinoki than Sugi. Because the 2 variables had counterbalancing effects on transpiration, Esta of Hinoki was similar to (94% of) that of Sugi. This offset was also found between the mean Etre of the 2 species. Esta was similar between the stands from May to October, whereas Esta of Sugi was notably greater than that of Hinoki from February to April. During these 3 months, the difference in cumulative Esta was 21.7 mm, which accounted for 79% of the difference in annual Esta between Hinoki and Sugi (192 and 219 mm/year, respectively). We found that canopy conductance (Gc) and its sensitivity to the mean vapour pressure deficit during daylight hours in Sugi were particularly high in early spring, whereas those in Hinoki shifted gradually throughout the growing season. This difference was related to the optimal temperature of Gc in Sugi, which was approximately 10 °C lower than that in Hinoki. Our results suggest that plantations of water‐conserving species such as Hinoki produce timber slowly but yield water resources generously. Moreover, for plantations of trees sensitive to high temperature, such as Sugi, managers should be concerned about possible future decline caused by anticipated global warming. 相似文献