关键词： 病毒性肝炎   乙型肝炎   丙型肝炎   树鼩   动物模型  

摘要： 病毒性肝炎是由肝炎病毒引起的肝脏疾病。在我国,病毒性肝炎高度流行,其中又以乙型肝炎病毒(Hepatitis B virus,HBV)和丙型肝炎病毒(Hepatitis C virus,HCV)危害较大。动物模型是研究疾病感染与发病机制,进行药物与疫苗研究的必要工具。目前病毒性肝炎实验动物模型的研究已取得长足的发展,主要集中于病毒在动物体内的感染特性及发病规律方面。本文仅就病毒性肝炎动物模型,尤其乙型、丙型肝炎树鼩动物模型的研究及建模策略进行综述。

关键词： 中药材市场   动物类   组成部分   市场经销   哈尔滨   农家  

摘要： 动物类药材为我国传统中药材之一，是我国中药材专业市场经销的重要组成部分，更是药市、药厂、药企、医院等不可或缺的品种之一。动物类药材的产量、销量、库存、价格、走势等一系列商情已引起商家和农家的密切关注。那么，哈尔滨三棵树中药材市场上的动物类药材的整体走势如何？

关键词： 《动物星球》   大师   话筒   电视纪录片   系列节目   节目介绍   录音室   华盛顿  

摘要： 美国《动物星球》系列节目“树屋大师”（TreehouseMasters）是一档60分钟的电视纪录片。最近，节目介绍了一座特别的树屋录音室。它掩映在华盛顿伍丁维尔市茂密的美国侧柏树林之中，高耸于空中，距离地面18m。

关键词： 精原干细胞   啮齿类动物   非人灵长类动物   男性不育   树鼩  

摘要： 精原干细胞（ spermatogonial stem cells, SSCs）是雄性精子发生和生育能力维持的基础，具有干细胞的普遍特征，可自我更新并具分化潜能。SSCs在成熟睾丸中的数量很少，加之没有可用于鉴定SSCs的特异性分子标记，SSCs的相关研究一直是雄性生殖生物学领域研究的热点和难点。近年来针对啮齿类动物SSCs的研究技术和体系日趋成熟，研究成果不断涌现，但对灵长类动物SSCs的生理特性，自我更新及调控机制的研究尚未深入，而相关研究在临床上对治疗男性不育等生殖疾病有重要意义。树朐是灵长类的近亲．在很多方面具有可用来替代猕猴等大型灵长类实验动物的遗传基础，可以作为研究灵长类SSCs的良好模型。

关键词： grazing   diversity   large-herbivore exclusion   herbivory   disturbance   Konza Prairie, Kansas, USA   richness   forb   herbaceous community   grass   Kruger National Park, South Africa   fire  

摘要： Herbivory and fire shape plant community structure in grass-dominated ecosystems, but these disturbance regimes are being altered around the world. To assess the consequences of such alterations, we excluded large herbivores for seven years from mesic savanna grasslands sites burned at different frequencies in North America (Konza Prairie Biological Station, Kansas, USA) and South Africa (Kruger National Park). We hypothesized that the removal of a single grass-feeding herbivore from Konza would decrease plant community richness and shift community composition due to increased dominance by grasses. Similarly, we expected grass dominance to increase at Kruger when removing large herbivores, but because large herbivores are more diverse, targeting both grasses and forbs, at this study site, the changes due to herbivore removal would be muted. After seven years of large-herbivore exclusion, richness strongly decreased and community composition changed at Konza, whereas little change was evident at Kruger. We found that this divergence in response was largely due to differences in the traits and numbers of dominant grasses between the study sites rather than the predicted differences in herbivore assemblages. Thus, the diversity of large herbivores lost may be less important in determining plant community dynamics than the functional traits of the grasses that dominate mesic, disturbance-maintained savanna grasslands.

关键词： Biology and life sciences   Ecology and environmental sciences   Population biology   Research Article   Zoology  

摘要： We construct a state-and-transition model for mammals in tropical savannas in northern Australia to synthesize ecological knowledge and understand mammalian declines. We aimed to validate the existence of alternative mammal assemblage states similar to those in arid Australian grasslands, and to speculate on transition triggers. Based on the arid grassland model, we hypothesized that assemblages are partitioned across rainfall gradients and between substrates. We also predicted that assemblages typical of arid regions in boom periods would be prevalent in savannas with higher and more regular rainfall. Data from eight mammal surveys from the Kimberley region, Western Australia (1994 to 2011) were collated. Survey sites were partitioned across rainfall zones and habitats. Data allowed us to identify three assemblage states: State 0:- low numbers of mammals, State II:- dominated by omnivorous rodents and State III:- dominated by rodents and larger marsupials. Unlike arid grasslands, assemblage dominance by insectivorous dasyurids (State I) did not occur in savannas. Mammal assemblages were partitioned across rainfall zones and between substrates as predicted, but-unlike arid regions-were not related strongly to yearly rainfall. Mammal assemblage composition showed high regional stability, probably related to high annual rainfall and predictable wet season resource pulses. As a consequence, we speculate that perpetually booming assemblages in savannas allow top-down control of the ecosystem, with suppression of introduced cats by the dingo, the region's top predator. Under conditions of low or erratic productivity, imposed increasingly by intense fire regimes and introduced herbivore grazing, dingoes may not limit impacts of cats on native mammals. These interacting factors may explain contemporary declines of savanna mammals as well as historical declines in arid Australia. The cat-ecosystem productivity hypothesis raised here differs from the already-articulated cat-

关键词： Carnivores   Forest management   Genet   Large old trees   Mediterranean landscape   Tree hollows  

摘要： Although tree hollows seem to be key structures for a wide range of forest mammals, their importance for Mediterranean forest carnivores remain poorly understood. Here we address this issue, by analysing daily resting site use by 21 radio-collared common genets. Tree hollows were used far more frequently during the wet season (October-April;73.1% of daily locations) than in the dry season (May-September;47.6%). Nests and underground dens were the second and third most frequently used resting sites, respectively, in both wet (17.5% and 9.4%) and dry (34.1% and 18.3%) seasons. Each individual reused a large percentage of its resting sites (65.7%). Some resting sites (17.3%) were used by more than one individual, but simultaneous sharing was exceedingly rare (0.56% of daily locations). Hollow use probability during the wet season varied little in relation to environmental variables, though there was a tendency to be higher away from riparian habitats (>50 m) and to be lower in sites with very high shrub cover (>80%). Environmental influences were responsible for more variability in the dry season, when hollow usage was highest in hot days, in days with precipitation, far from riparian habitats, close to sources of human disturbance, in landscapes dominated by continuous forest habitats, and in sites with low shrub cover. Results support the importance of tree hollows for Mediterranean forest carnivores, probably because they provide safe shelter against unfavourable weather, predators and human disturbance. However, results also revealed the importance of riparian trees, which offer support for building nests close to sources of water and food during the dry season. Considering home range size and the average number of hollow-bearing trees used by each genet, we recommend that management of cork and holm oak forests should strive to safeguard at least 4.6 hollow-bearing trees per 100 ha, while simultaneously maintaining large riparian trees. This will improve the resti

关键词： body size   climate   competition and facilitation   ecological field experiments   elephants   extinction   indirect species interactions   Kenya (East Africa)   rodents   top-down control   ungulate herbivory  

摘要： Assessing the direct and indirect consequences of nonrandom species removal within guilds of strongly interacting species, such as large mammalian herbivores, is an important goal in basic and applied ecology. The ecological impacts of such perturbations are often contingent on abiotic conditions, which have hindered efforts to generalize the results of field experiments. Thus, there is a need for experiments that selectively remove different species from ecologically important guilds and that are replicated across environmental gradients. In 2008, we constructed a series of size-selective large-herbivore exclosures across a natural rainfall gradient in semi-arid Kenyan savanna. This experiment (“UHURU”, for ungulate herbivory under rainfall uncertainty) aims to (a) characterize the effects of successively removing the largest size classes of herbivores from the system and (b) evaluate how the direction and magnitude of these effects are shaped by variation in precipitation regimes. UHURU consists of three electrically fenced herbivore-exclusion treatments and an unfenced control, applied to blocks of contiguous 1-ha plots. The three fenced treatments are: “Mega” (exclusion of elephants and giraffes only); “Meso” (exclusion of both megaherbivores and mesoherbivores, ∼40 kg and larger); and “Total” (exclusion of all herbivores ≥5 kg). Each block of treatments is replicated three times at each of three sites along the 20-km rainfall gradient (increasing from 439 mm/yr in the north to 639 mm/yr in the south, with little background variation in soil attributes and species composition). We present data, spanning 2008–2013, from (a) biannual surveys of understory plants at 49 staked grid points within each of the 36 1-ha plots (1764 total stakes); (b) annual woody-plant censuses within the central 0.36 ha of each plot; (c) annual and semi-annual monitoring of individually marked woody plants; (d) small-mammal capture–mark–recapture sessions conducted every other month in

关键词： Ungulates   Water   Piosphere   Rainfall variability   Mara-Serengeti ecosystem   Pastoralism   Zero-inflated models  

摘要： Water, forage and predation constrain ungulate distributions in savannas. To understand these constraints, we characterized distributions of 15 herbivore species from water, locations of peak density and degree of clustering around the peaks using zero-inflated count data models and mapping census data collected in the Mara reserve and the adjoining pastoral ranches in Kenya during a wet and dry year. Herbivores followed a humped pattern (n = 46), suggesting constrained foraging in which they balance the benefits of proximity to water with the costs of foraging where food is depleted near water and travelling to more abundant food distant from water;an exponentially decreasing pattern (n = 11), indicating strong attraction to water or vegetation near water;or a uniform (n = 3) pattern. The details rather than the types of these patterns varied between years. Herbivores concentrated farther from water and more tightly around locations of their peak densities in the ranches than the reserve. Herbivores were more abundant and widely distributed from water in the wet than the dry year, and segregated along the distance-to-water gradient, presumably to minimize interspecific competition for food. Pastoralism compressed herbivore distributions and partially excluded some species (warthog, hartebeest, topi, wildebeest, zebra, eland, buffalo and elephant) from, while attracting others (Grant's and Thomson's gazelles, impala, giraffe) to the ranches, relative to the reserve. Regulating cultivation, fencing, settlements and livestock stocking levels in the ranches would allow continued wildlife access to water, reduce competition with, displacement or harassment of wildlife by people, livestock and dogs near water.

关键词： Trees   Marsupials   Opossums   Forests   Species diversity   Conservation science   Ecosystems   Forest ecology  

摘要： A holy grail of conservation is to find simple but reliable measures of environmental change to guide management. For example, particular species or particular habitat attributes are often used as proxies for the abundance or diversity of a subset of other taxa. However, the efficacy of such kinds of species-based surrogates and habitat-based surrogates is rarely assessed, nor are different kinds of surrogates compared in terms of their relative effectiveness. We use 30-year datasets on arboreal marsupials and vegetation structure to quantify the effectiveness of: (1) the abundance of a particular species of arboreal marsupial as a species-based surrogate for other arboreal marsupial taxa, (2) hollow-bearing tree abundance as a habitat-based surrogate for arboreal marsupial abundance, and (3) a combination of species-and habitat-based surrogates. We also quantify the robustness of species-based and habitat-based surrogates over time. We then use the same approach to model overall species richness of arboreal marsupials. We show that a species-based surrogate can appear to be a valid surrogate until a habitat-based surrogate is co-examined, after which the effectiveness of the former is lost. The addition of a species-based surrogate to a habitat-based surrogate made little difference in explaining arboreal marsupial abundance, but altered the co-occurrence relationship between species. Hence, there was limited value in simultaneously using a combination of kinds of surrogates. The habitat-based surrogate also generally performed significantly better and was easier and less costly to gather than the species-based surrogate. We found that over 30 years of study, the relationships which underpinned the habitat-based surrogate generally remained positive but variable over time. Our work highlights why it is important to compare the effectiveness of different broad classes of surrogates and identify situations when either species- or habitat-based surrogates are likely t