鳙幼鱼在下行过程中应对加速流的行为响应研究

以具有下行洄游需求的鳙(Aristichthys noblis)幼鱼为研究对象, 在自行设计制造加速流的装置中进行下行实验, 结果发现: 在实验设置的3个入口流速下(入口流速分别为: 0.018、0.034和0.053 m/s), 鳙幼鱼的通过率均为100%。在下行通过孔口的方式上, 以尾部先通过为主(即顶流通过), 尤其是在流速较高的时候, 头部先通过比例仅为6.25%。在通过总时间(从实验开始至通过孔口的时间)上, 鳙幼鱼在低流速条件下显著小于在中流速条件下(P<0.05), 而在高流速条件下与中低两个流速条件下均无显著性差异(P>0.1)。在通过时间(从实验鱼最后一次进入加速区域, 至通过孔口的时间)上, 鳙幼鱼在三种流速条件下没有显著差异性(P>0.1)。研究表明, 加速流会对鳙幼鱼下行的时间和方式产生影响。研究旨在为鱼类资源保护, 帮助鱼类安全高效过坝提供基础数据, 同时也为研究鱼类在下行过程中应对加速流的行为研究提供一种研究方法。     

不同流速下气泡幕和闪光对光倒刺鲃趋避行为的影响

{{@ convertAbstractHtml(article.abstractinfoCn, "cn")}}       

不同流速下杂交鲟幼鱼游泳状态与活动代谢研究

为研究水流速度对杂交鲟幼鱼行为和代谢的影响,探讨游泳状态与活动代谢及相关游泳运动参数之间的关系,在26℃水温下,使用特制的鱼类游泳行为和活动代谢同步测定装置,测定了杂交鲟幼鱼在0.1、0.3、0.5 m/s三种流速和静水条件下的游泳状态、趋流率、摆尾频率和耗氧率。结果表明:随着流速的增大,杂交鲟幼鱼逆流前进和逆流静止游泳状态所占时间比例显著减少,而逆流后退所占时间比例显著增加,顺流而下时间比例有所上升。在0.0—0.3 m/s的流速范围内,杂交鲟幼鱼各个时段的平均趋流率、摆尾频率和耗氧率均随着流速的增加而增大,在0.3 m/s流速下分别达到100%﹑(2.53±0.34)Hz和(490.99±164.59)mg O2/(kg.h)。当流速增加至0.5 m/s时,在趋流率仍保持100%的情况下,其耗氧率相比0.3 m/s增加了21.86%,而摆尾频率却减小了6.70%。实验过程杂交鲟幼鱼趋流率与摆尾频率呈显著线性正相关,而摆尾频率与耗氧率在大部分时段却无相关性。随着时间的延长,各流速组杂交鲟幼鱼趋流率、摆尾频率和耗氧率呈现不同的变化趋势,其趋流率均相对稳定;但摆尾频率均随时间延长呈下降趋势,而耗氧率则在实验前9h随时间延长逐渐增加,随后趋于稳定。研究结果提示:杂交鲟幼鱼游泳状态的变化与流速有关,而反映运动强度大小的摆尾频率与活动代谢率的关系受到游泳状态的显著影响,同时也与运动代谢特征的时间变化有关。       

倒刺鲃生活史各阶段的食性分析

2004年3月至2005年2月对分布在西江水系中上游广西柳江段龙江中的一种名贵经济鱼类——倒刺鲃(Spinibarbus denticulatus)生活史各发育阶段的食性进行了分析研究。采用常规生物学方法,测定了倒刺鲃生活史各发育阶段的消化道指数、肠长指数、食物充塞度、肥满度等生物学参数。通过其食物组成、出现率和饵料类群变动或更替的数量特征,细分出倒刺鲃各发育阶段的食性特点:仔鱼和稚鱼阶段为杂食性偏动物食性;早期幼鱼为明显的杂食性;青年鱼则趋向于杂食偏植物食性;成鱼才是真正意义上的草食性鱼类。倒刺鲃幼龄及青年个体在周年中保持2·0～5·0的食物充塞度,而成鱼的摄食强度则存在明显的季节变化,在1月的平均充塞度只有0·3,在10月则为5·0。倒刺鲃幼龄个体周年中肥满度变化不明显,条件系数全年维持在2·201～2·406;青年个体周年中的肥满度5～8月间维持相对稳定,平均条件系数的变幅为2·337～2·365,但从9～12月,条件系数逐渐从2·451逐渐增大到2·852,在1～4月,条件系数逐渐从2·693减小到2·306;成鱼的肥满度呈现明显的季节变化,7月的条件系数为1·775,12月的则高达2·894。在倒刺鲃的整个生活史中,藻类在消化道中的出现率均达100%,平均湿重百分比在25·0%以上,可能是其重要的食物类群。     

Testing nitrogen and water co-limitation of primary productivity in a temperate steppe

Background and aims

Studies have found significant differences in methane (CH₄) emissions among rice cultivars; however, it is unclear whether this difference is related to radial oxygen loss (ROL) from the roots.

Methods

Based on a 2-year in situ field study and solution culture experiments on 16 rice cultivars, we investigated CH₄ emission levels and their dependence on ROL.

Results

We detected significant differences in CH₄ emission and ROL among rice cultivars. The lowest and highest CH₄ emission levels were 4.10 and 7.35 g m^?2 for early rice, and 14.36 and 23.33 g m^?2 for late rice, respectively. The maximum and minimum ROL values were 3.77 and 1.73 mmol plant^?1 h^?1 for early rice, and 4.18 and 2.08 mmol plant^?1 h^?1 for late rice, respectively. Seasonal total CH₄ emission was negatively correlated with ROL in the early rice season (p?<?0.01), and (p?<?0.01) in the late rice season. ROL was positively correlated with the number of roots per plant (RN), root tips per plant (RT), and root volume per plant (RV).

Conclusions

We suggest that ROL can be used as a predictive index for CH₄ emissions. RN, RT, and RV were the most important factors influencing ROL in rice cultivars.

     

Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by recombinant Escherichia coli harboring propionyl-CoA synthase gene (prpE) or propionate permease gene (prpP)

In order to enhance 3-hydroxyvalerate (3HV) fraction in copolyesters of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), the propionate permease gene prpP or the propionyl-CoA synthase gene prpE was transformed into Escherichia coli XL10-Gold with co-expression of PHB operon (phaCAB) from Ralstonia eutropha. The recombinant E. coli strains were cultured on mixed carbon sources composed of glucose and propionic acid to promote PHBV accumulation. It was shown that the over-expression of prpE suppressed 3HV incorporation into PHBV copolymer, which led to reduced 3HV fraction. In contrast, the over-expression of prpP improved the 3HV content from 5.6 to 14.3 mol%, followed by an increased PHBV accumulation up to 62 wt%. The results showed that the expression of prpP stimulated the uptake and utilization of propionic acid and increased the 3HV fraction in PHBV. However, the over-expression of prpE in E. coli did not affect 3HV content in PHBV. Surprisingly, co-expression of prpE and prpP did not lead to any 3HV formation. This study showed the possibility to change the PHBV composition without overdose of propionic acid which is expensive and toxic for the cells.     

瓦氏黄颡鱼和鲢对光照强度和颜色的选择简

以野生瓦氏黄颡鱼和人工养殖鲢为研究对象,设置4种光照强度梯度0—10、10—30、100—200、700—800 lx及4种光照颜色红、白、蓝、绿,采用单因子实验法,研究了瓦氏黄颡鱼和鲢对光的趋避行为。结果表明:在光照强度选择的实验中,瓦氏黄颡鱼在0—10、10—30、100—200和700—800 lx四个光照强度中出现的次数百分比分别是:78.33%±21.51%、10.00%±14.86%、7.33%±8.27%和4.33%±7.74%。瓦氏黄颡鱼在光照强度为0—10 lx的区域中出现的次数明显多于其他三种光照强度,且差异显著(P0.05)。而鲢在四种光照强度中出现的次数之间不存在显著性差异(P0.05)。在光照颜色选择实验中,瓦氏黄颡鱼在四种光照颜色中出现的次数百分比不存在显著性差异(P0.05)。鲢在红、白、蓝和绿四种光照颜色中出现的次数百分比分别是:12.67%±13.63%、30.33%±18.47%、35.67%±24.73%、21.33%±15.02%。鲢在白光、蓝光区域出现的次数显著高于其他两种区域,且差异显著(P0.05)。实验通过研究光照强度和光照颜色对瓦氏黄颡鱼和鲢行为的影响,为鱼类趋光性研究提供一定的参考。     

Nitrogen fertilization and fire act independently on foliar stoichiometry in a temperate steppe

Nitrogen (N) fertilization, as a grassland management strategy, has been widely used to improve forage quality and increase the productivity of grasslands degraded by overstocking. It is widely accepted that N addition will alter ecosystem structure and function, and that these effects may be altered by natural disturbances, such as fire. We examined the effects of annual burning and N fertilization (17.5 g N m^?2 year^?1, at a surplus rate in order to simulate agriculture treatment) on foliar chemistry and stoichiometric ratios of eight dominant species (Leymus chinensis, Stipa grandis, Cleistogenes squarrosa, Potentilla bifurca, Thalictrum squarrosum, Artemisia frigida, Kochia prostrata and Caragana microphylla) in a temperate steppe in northern China. After 3 years of treatments, annual burning significantly increased soil extractable phosphorus (P) concentration but showed no effects on soil inorganic N concentration, whereas N fertilization caused a significant increase in inorganic N concentration but not of extractable P. Species differed substantially with respect to all nutritional and stoichiometric variables. Both annual burning and N fertilization caused significant increases in foliar N and P concentrations and thus decreases in carbon (C):N and C:P ratios. While annual burning showed no effects on N:P ratios, N fertilization produced higher N:P ratios. However, species responded idiosyncratically to both fire and N fertilization in terms of foliar N concentration, C:N and N:P ratio. In addition, there was no interaction between fire and N fertilization that affected all variables. This study suggests that both annual burning and N fertilization have direct impacts on plant elemental composition and that fire- and N addition-induced changes of community composition may have important consequences for plant-mediated biogeochemical cycling pathways in temperate steppe ecosystem.     

干旱胁迫对新西伯利亚银白杨抗氧化系统和幼苗生长的影响

以1年生新西伯利亚银白杨幼苗为试验材料,研究了不同干旱胁迫强度下新西伯利亚银白杨抗氧化系统的生理响应和幼苗生长状况。结果表明,在20%~95%土壤含水量范围内,随着干旱胁迫强度的增加,幼苗质膜透性升高,保护酶活性呈规律性变化;同时,幼苗生长受到的抑制作用加剧;恢复供水后,幼苗质膜透性和各保护酶活性均恢复到接近对照水平。因此认为,在土壤含水量在田间持水量的20%~95%,即绝对容积含水率11.5%~43.7%之间新西伯利亚银白杨具备良好的适应调节能力,其最适土壤容积含水率为27.6%~29.9%。     

Illumina Sequencing of 16S rRNA Tag Revealed Spatial Variations of Bacterial Communities in a Mangrove Wetland

The microbial community plays an essential role in the high productivity in mangrove wetlands. A proper understanding of the spatial variations of microbial communities will provide clues about the underline mechanisms that structure microbial groups and the isolation of bacterial strains of interest. In the present study, the diversity and composition of the bacterial community in sediments collected from four locations, namely mudflat, edge, bulk, and rhizosphere, within the Mai Po Ramsar Wetland in Hong Kong, SAR, China were compared using the barcoded Illumina paired-end sequencing technique. Rarefaction results showed that the bulk sediment inside the mature mangrove forest had the highest bacterial α-diversity, while the mudflat sediment without vegetation had the lowest. The comparison of β-diversity using principal component analysis and principal coordinate analysis with UniFrac metrics both showed that the spatial effects on bacterial communities were significant. All sediment samples could be clustered into two major groups, inner (bulk and rhizosphere sediments collected inside the mangrove forest) and outer mangrove sediments (the sediments collected at the mudflat and the edge of the mangrove forest). With the linear discriminate analysis scores larger than 3, four phyla, namely Actinobacteria, Acidobacteria, Nitrospirae, and Verrucomicrobia, were enriched in the nutrient-rich inner mangrove sediments, while abundances of Proteobacteria and Deferribacterias were higher in outer mangrove sediments. The rhizosphere effect of mangrove plants was also significant, which had a lower α-diversity, a higher amount of Nitrospirae, and a lower abundance of Proteobacteria than the bulk sediment nearby.