群体成员大小差异对不同生境鲤科鱼类集群行为的影响

为研究群体成员大小差异对不同喜好生境鱼类集群行为特征的影响, 实验分别以鳊(Parabramis pekinensis)和中华倒刺鲃(Spinibarbus sinensis)幼鱼为实验对象, 比较分析4尾等大小(E)和不等大小(2大2小, NE)实验鱼群体的自发游泳速度、空间分布以及对恐吓刺激反应等集群行为参数的差异。结果显示: (1)和鳊相比, 中华倒刺鲃有更高的自发游泳速度、速度同步性和排列方向的极性, 但二者对恐吓刺激的反应率及反应的协调一致性相似; (2)当群体成员大小出现差异时, 两种鱼群体排列方向的极性不受影响, 且大小个体成员间的速度及其同步性均没有差异, 但整体的速度同步性与等大小群体相比有所下降; (3)个体间距离数据显示, 个体大小差异不会影响两种鱼群体的凝聚力; (4)群体成员在两种鱼群中偏好位置不同, 当群体成员大小不同时, 大个体成员更偏好占据领头鱼位置; (5)群体成员大小的差异导致两种鱼对刺激的反应率下降。研究表明: 中华倒刺鲃具有更高的活跃性、更好的群体运动的协调性, 可能与其流水生境相关; 当群体成员大小出现差异时, 成员不分大小在整体上协调运动的速度和方向, 并保持群体有较高的凝聚力, 但两种鱼类自发游泳速度调整策略截然不同(鳊大小个体速度妥协趋同, 而中华倒刺鲃低速个体速度提高); 群体成员大小差异导致鱼群对恐吓刺激的反应率有所下降, 可能原因包括体形差异导致的社会因素造成敏锐性下降、信息交流效率受阻和(或)集群收益代价出现分化影响一致决策的形成等。     

Aggregate Size Distribution of Ammonia-Oxidizing Bacteria and Archaea at Different Landscape Positions

To quantify the spatial distribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) and to determine nitrification activity in soil aggregates along a landscape, soil samples were collected from three landscape positions (shoulder, backslope, and toeslope) at two pasture sites with contrasting climatic conditions. The abundance of AOB and AOA was estimated by quantifying their respective bacterial and archaeal amoA gene copies using real-time polymerase chain reaction. Soil organic C (SOC), total N (TN), and the potential nitrification rate (PNR) were measured in aggregate size ranges (4–1, 1–0.25, and 0.25–0.05 mm). At site 1, a decreasing trend in PNR was observed as the size of aggregates decreased. Both bacterial and archaeal amoA genes were higher in the macroaggregates (4–1 and 1–0.25 mm) than in the microaggregates (0.25–0.05 mm) along the landscape. At site 2, PNR was higher in the smallest size of aggregates. In the 0.25–0.05-mm fraction, the abundance of bacterial and archaeal amoA genes was equal to, or greater than, those found in larger aggregate sizes. The relative abundance of archaeal amoA gene and the PNR correlated with relative SOC and TN contents along the landscapes. The positive relationship between relative archaeal amoA gene abundance and PNR suggests that nitrification in the studied pastures is probably driven by ammonia-oxidizing Thaumarchaeota.     

Newly discovered role of the heterotrophic nanoflagellate Katablepharis japonica,a predator of toxic or harmful dinoflagellates and raphidophytes

Heterotrophic nanoflagellates are ubiquitous and known to be major predators of bacteria. The feeding of free-living heterotrophic nanoflagellates on phytoplankton is poorly understood, although these two components usually co-exist. To investigate the feeding and ecological roles of major heterotrophic nanoflagellates Katablepharis spp., the feeding ability of Katablepharis japonica on bacteria and phytoplankton species and the type of the prey that K. japonica can feed on were explored. Furthermore, the growth and ingestion rates of K. japonica on the dinoflagellate Akashiwo sanguinea—a suitable algal prey item—heterotrophic bacteria, and the cyanobacteria Synechococcus sp., as a function of prey concentration were determined. Among the prey tested, K. japonica ingested heterotrophic bacteria, Synechococcus sp., the prasinophyte Pyramimonas sp., the cryptophytes Rhodomonas salina and Teleaulax sp., the raphidophytes Heterosigma akashiwo and Chattonella ovata, the dinoflagellates Heterocapsa rotundata, Amphidinium carterae, Prorocentrum donghaiense, Alexandrium minutum, Cochlodinium polykrikoides, Gymnodinium catenatum, A. sanguinea, Coolia malayensis, and the ciliate Mesodinium rubrum, however, it did not feed on the dinoflagellates Alexandrium catenella, Gambierdiscus caribaeus, Heterocapsa triquetra, Lingulodinium polyedra, Prorocentrum cordatum, P. micans, and Scrippsiella acuminata and the diatom Skeletonema costatum. Many K. japonica cells attacked and ingested a prey cell together after pecking and rupturing the surface of the prey cell and then uptaking the materials that emerged from the ruptured cell surface. Cells of A. sanguinea supported positive growth of K. japonica, but neither heterotrophic bacteria nor Synechococcus sp. supported growth. The maximum specific growth rate of K. japonica on A. sanguinea was 1.01 d⁻¹. In addition, the maximum ingestion rate of K. japonica for A. sanguinea was 0.13 ng C predator⁻¹d⁻¹ (0.06 cells predator⁻¹d⁻¹). The maximum ingestion rate of K. japonica for heterotrophic bacteria was 0.019 ng C predator⁻¹d⁻¹ (266 bacteria predator⁻¹d⁻¹), and the highest ingestion rate of K. japonica for Synechococcus sp. at the given prey concentrations of up to ca. 10⁷ cells ml⁻¹ was 0.01 ng C predator⁻¹d⁻¹ (48 Synechococcus predator⁻¹d⁻¹). The maximum daily carbon acquisition from A. sanguinea, heterotrophic bacteria, and Synechococcus sp. were 307, 43, and 22%, respectively, of the body carbon of the predator. Thus, low ingestion rates of K. japonica on heterotrophic bacteria and Synechococcus sp. may be responsible for the lack of growth. The results of the present study clearly show that K. japonica is a predator of diverse phytoplankton, including toxic or harmful algae, and may also affect the dynamics of red tides caused by these prey species.     

伊比利亚河共生的当年生鳟和埃布罗河鳟的夏季摄食关系

1996-1998年8月在Larraun河(埃布罗河流域,西班牙北部)共捕获306尾埃布罗河(鱼岁)和185尾0龄的鳟,分析比较了胃含物组成,并测定了种间的食物重叠.食物的个数百分比组成表明两种都主要摄食水生无脊椎动物.摄食策略图显示两种都是摄食不同食物 种类的广食性种类.另外,比较胃含物和底栖大型无脊椎动物群落表明,0龄的鳟和埃布罗河(鱼岁)不摄食光螺科、钩虾科、细蜉科、 四节蜉科和卷襀科的物种,而喜食摇蚊科、五节蜉科和毛翅目物种.尽管简化的Morisitas指数表明Larraun河中这两种鱼之间的食物重叠是显著的,但由于栖息地不同和摄食的可塑性可以降低种间的竞争,使得该水域的这两种鱼能以相对较大的数量共存.然而,在食物资源和可用栖息地有限的河域,埃布罗河(鱼岁)的引入,其适应性和可塑性有可能威胁单独存在的鳟     

长江口两种重要石首鱼类的摄食习性

通过对2006年夏、秋季在长江口及其毗邻海域采集的575尾白姑鱼(Argyrosomus argentatus)和1089尾小黄鱼(Pseudosciaena polyactis)胃含物样品的分析,利用多元统计分析方法,研究了它们的摄食习性以及随栖息地、季节和体长的变化规律。结果表明:该水域的白姑鱼是底栖动物食性,小黄鱼是混合动物食性,甲壳类在它们食物中均占83%以上的比例,2种石首鱼类的食物重叠系数为0.55。由于摄食的优势饵料种类的差异,使这2种石首鱼类之间不存在严重的食物竞争。与20世纪80年代的研究结果相比,两种石首鱼类所摄食的鱼类的比例均有所下降。结果还表明:白姑鱼的摄食习性较为稳定,受栖息环境、季节以及体长变化的影响较小;而小黄鱼随栖息环境、季节以及体长的变化较大,且109mm是其发生食性转换的一个关键的临界体长。     

虹鳟对时间和地点的学习记忆(英文)

为确定虹鳟(Oncorhynchus mykiss)是否能将日投放两次食物的不同时间和地点联系起来,在30天内,于09:00-10:00将食饵投放在水族箱一侧,于15:00-16:00将食饵投放在水族箱另一侧.在第21天和28天,不放食饵以确定虹鳟对时间-地点的学习记忆.结果表明,虹鳟将不同时间和地点联系起来以获取食物,并且在水族箱两个投放食饵之处均表现出预取食活动,提示该物种具有控制时间-地点学习任务的内在机制.     

Predation by small mobile aquatic predators regulates populations of the intertidal limpet Patella vulgata (L.)

Highly mobile aquatic predators are known to forage in the intertidal during periods of immersion. There is limited quantitative information, however, on the extent to which these predators influence the abundance of grazing molluscs which are known to have a key role in structuring intertidal assemblages. Our preliminary video observations revealed that crabs and small fish were abundant on shores in southwest England during high-tide. We then used manipulative experiments to quantify the effect of small mobile aquatic predators on the abundance of limpets (Patella vulgata L.). On the lower shore at two moderately sheltered rocky shores three treatments were established: complete cage, partial cage (cage control) and uncaged (natural condition). The complete cages excluded all predators. The partial cage treatment allowed full access to small predators and the uncaged treatment allowed access to all predators. After two months, limpet abundance in uncaged and partial cage treatments had declined by around 50% compared to the complete cage treatment. Population structure also changed with survival of larger individuals being greater than smaller individuals in the open and partial cage treatments compared to the complete cage treatment. The effects of excluding predators were consistent at small (meters) and large spatial scales (kilometres) and hence, it would appear that the outcomes of our research are generally applicable to similar shores in the region.To explore the mechanism behind the differential effects of predators according to prey size, we compared the detachment force required to remove limpets of differing sizes from the shore. This was around four times greater for larger individuals than for smaller ones indicating that smaller limpets were more vulnerable to predation. These effects were also consistent between locations. Subsequent laboratory observations showed that the crabs Carcinus maenas (L.), Necora puber (L.) and Cancer pagurus (L.) which are locally abundant predators of limpets, had differing handling behaviour but were all highly efficient at removing limpets from substratum. Hence, shell width and attachment force appeared to be critical factors influencing the vulnerability of limpets to predation by these crabs. Limpets are known to control the abundance of macroalgae on shores in the North-east Atlantic and so our conclusions about the role of mobile predators in regulating the abundance of these grazers are important to our broader understanding of the ecology of these shores.     

FoxO1对下丘脑摄食中枢的影响研究进展

下丘脑是人体的摄食中枢,它通过抑制食欲的阿黑皮素原(POMC)神经元和促进食欲的神经肽相关蛋白(AgRP)神经元调节摄食及能量代谢。叉头转录因子O亚族1(FoxO1)是胰岛素信号通路和瘦素信号通路中重要的调节蛋白,FoxO1的生理作用是促进下丘脑Agrp基因表达、抑制Pomc基因表达,抑制瘦素信号通路的转录激活因子3(STAT3)蛋白对Pomc基因转录的促进作用,从而促进食欲。瘦素和胰岛素均可激活经典的IRS/PI(3)K/Akt信号通路,使FoxO1磷酸化失去活性,抑制食欲。此外,沉默信息调节因子Sirt1也可以通过去乙酰化,影响FoxO1的转录活性。本文综述了胰岛素、瘦素、Sirt1通过FoxO1调节下丘脑摄食中枢的作用机制。     

Determination of food sources and trophic position in Malaysian tropical highland streams using carbon and nitrogen stable isotopes

Stable isotope analysis has been extensively used as an effective tool in determination of trophic relationship in ecosystems. In freshwater ecosystem, aquatic invertebrates represent main component of a river food web. This study was carried out to determine potential food sources of freshwater organism together with pattern of trophic position along the river food web. In this study, rivers of Belum-Temengor Forest Complex (BTFC) has been selected as sampling site as it is a pristine area that contains high diversity and abundance of organisms and can be a benchmark for other rivers in Malaysia. Stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) were applied to estimate trophic position and food web paradigm. Analysis of stable isotopes based on organic material collected from the study area revealed that the highest δ¹³C value was reported from filamentous algae (? 22.68 ± 0.126⁰/₀₀) and the lowest δ¹³C was in allocthonous leaf packs (? 31.58 ± 0.187⁰/₀₀). Meanwhile the highest δ¹⁵N value was in fish (8.45 ± 0.177⁰/₀₀) and the lowest value of δ¹⁵N was in autochthonous aquatic macrophyte (2.00 ± 1.234⁰/₀₀). Based on the δ¹⁵N results, there are three trophic levels in the study river and it is suggested that the trophic chain begins with organic matter followed by group of insects and ends with fish (organic matter < insects < fish).     

Intra‐trophic isotopic discrimination of 15N/14N for amino acids in autotrophs: Implications for nitrogen dynamics in ecological studies

The differential discrimination of nitrogen isotopes (¹⁵N/¹⁴N) within amino acids in consumers and their diets has been routinely used to estimate organismal tropic position (TP). Analogous isotopic discrimination can occur within plants, particularly in organs lacking chloroplasts. Such discrimination likely arises from the catabolic deamination of amino acids, resulting in a numerical elevation of estimated TP, within newly synthesized biomass. To investigate this phenomenon, we examined the ¹⁵N/¹⁴N of amino acids (δ¹⁵N_AA) in spring leaves and flowers from eight deciduous and two annual plants. These plants were classified on the basis of their time of bloom, plants that bloomed when their leaves were absent (Type I) versus plants that bloomed while leaves were already present (Type II). Based on the δ¹⁵N_AA values from leaves, both plant types occupied comparable and ecologically realistic mean TPs (=1.0 ± 0.1, mean ± 1σ). However, the estimated TPs of flowers varied significantly (Type I: 2.2 ± 0.2; Type II: 1.0 ± 0.1). We hypothesize that these results can be interpreted by the following sequence of events: (1) Type I floral biomass is synthesized in absence of active photosynthesis; (2) the catabolic deamination of amino acids in particular, leaves behind ¹⁵N in the residual pool of amino acids; and (3) the incorporation of these ¹⁵N‐enriched amino acids within the biomass of Type I flowers results in the numerical elevation of the TPs. In contrast, the actively photosynthesizing Type II leaves energetically sustain the synthesis of Type II flower biomass, precluding any reliance on catabolic deamination of amino acids. Amino acids within Type II flowers are therefore isotopically comparable to the Type II leaves. These findings demonstrate the idiosyncratic nature of the δ¹⁵N_AA values within autotrophic organs and have implications for interpreting trophic hierarchies using primary producers and their consumers.