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1.
2.
群体成员大小差异对不同生境鲤科鱼类集群行为的影响 总被引:1,自引:0,他引:1
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。 相似文献
3.
Abstract Schizosaccharomyces pombe becomes resistant to killing by high concentration of hydrogen peroxide and other severe stresses including oxidants, high temperature and high concentration of ethanol when pretreated with nonlethal levels of hydrogen peroxide. In the presence of the protein synthesis inhibitor, cycloheximide, during hydrogen peroxide pretreatment, the cell obtained partial resistance to a higher level of hydrogen peroxide. The partial resistance to hydrogen peroxide in the presence of cycloheximide was acquired within 30 min of pretreatment but complete resistance obtained with de novo protein synthesis was not attained before 45 min of pretreatment. During adaptation to hydrogen peroxide, at least 15 polypeptides are induced, as analyzed by two-dimensional gel electrophoresis. Catalase activity is induced eight-fold by treatment with a nonlethal level of hydrogen peroxide. 相似文献
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P. Bourke D. Ziuzina L. Han P.J. Cullen B.F. Gilmore 《Journal of applied microbiology》2017,123(2):308-324
There is a diverse range of microbiological challenges facing the food, healthcare and clinical sectors. The increasing and pervasive resistance to broad‐spectrum antibiotics and health‐related concerns with many biocidal agents drives research for novel and complementary antimicrobial approaches. Biofilms display increased mechanical and antimicrobial stability and are the subject of extensive research. Cold plasmas (CP) have rapidly evolved as a technology for microbial decontamination, wound healing and cancer treatment, owing to the chemical and bio‐active radicals generated known collectively as reactive oxygen and nitrogen species. This review outlines the basics of CP technology and discusses the interactions with a range of microbiological targets. Advances in mechanistic insights are presented and applications to food and clinical issues are discussed. The possibility of tailoring CP to control specific microbiological challenges is apparent. This review focuses on microbiological issues in relation to food‐ and healthcare‐associated human infections, the role of CP in their elimination and the current status of plasma mechanisms of action. 相似文献
6.
We compared various aspects of the seed biology of eight non-pioneer tree species from a tropical seasonal rain forest in
Xishuangbanna, SW China, that differ in time of dispersal, size and fresh seed moisture content (MC). Seeds were tested for
germination under laboratory conditions after dehydration to different moisture levels and under 3.5, 10 and 30% solar irradiances
in neutral-shade houses. For six species, germination was also compared in forest understory (3.5% light) and center of a
forest gap (32.5% light). Under continuous dehydration over activated silica gel, 100% of seeds of four species had lost the
ability to germinate after 48 h, and those of all species except Castanopsis hystrix (decreased from >90 to 30% germination) had lost the ability to germinate after 120 h. Four species did not differ in final
germination percentages at the three irradiances (i.e. uniform germination). However, final germination percentages of Horsfieldia pandurifolia and Litsea pierrei var. szemaois were significantly lower in 30% than in 10 or 3.5% light, and seeds of Antiaris toxicaria and C. hystrix germinated to higher percentages in 30 and 10% than in 3.5% light. Mean time to germination (MTG) of the eight species (forest
and shade house data combined) ranged from 5–5 days for Pometia
tomentosa to 72–207days for L. pierrei; MTG for four species was ≤21 days. There was no obvious relationship between relative desiccation resistance and either
time of dispersal, MTG or uniformity of germination at the three light levels, or between seed size and MC or MTG. However,
the relationship between seed MC at maturity (25–60% fresh mass basis) and MC at 50% loss of seed viability (12.4–42.5%) was
significant. Seven of the species fit Garwood’s (Ecol Monogr 53:159–181, 1983) rapid-rainy germination syndrome and one, L. pierrei, either her delayed-rainy or intermediate-dry germination syndrome. However, fresh, non-dehydrated seeds of all eight species
germinated in ≤30 days at constant 30°C in light. 相似文献
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Field-measured grazing rates (ml/animal/d) of cladocerans (mostly daphniids) and diaptomids were assembled from various published
studies and plotted as a function of corresponding phytoplankton concentration (μg l−1 f.w.). Filtering rates of both zooplankton groups initially increased with seston concentration until maximal grazing rates
were observed at approximately 4 × 102 and 1 × 102 μg l−1 for cladocerans and copepods, respectively; at higher algal concentrations, filtering rates of both declined as a function
of food concentration. The shape of these curves are most consistent with Holling's (1966) Type 3 functional response.
We found little support for the Type 3 functional response in published laboratory studies of Daphnia; most investigators report either a Type 1 or Type 2 response. The one study in which the Type 3 response was observed involved
experiments where animals were acclimated at low food concentrations for 24 h, whereas those studies associated with response
Types 1 or 2 had acclimation periods of only 1 to 3 h. We therefore assembled relevant data from the literature to examine
the effect of acclimation period on the feeding rates of Daphnia at low food concentrations. In the absence of any acclimation, animals filtered at extremely low rates. After 2 h of acclimation,
however, filtering rates increased 4 to 5-fold but declined again with longer durations; after > 70 h of pre-conditioning,
filtering rates were almost as low as they had been with no acclimation.
We also found little support for the Type 3 functional response in published studies of copepods. The only study associated
with a Type 3 response involved a marine copepod that had been subjected to a starvation period of 48 h; however, an analysis
of the effects of acclimation period did not yield conclusive evidence that filtering rates of freshwater copepods (Diaptomus and Eudiaptomus) decrease significantly with acclimation duration.
The low filtering rates associated with long acclimation periods in laboratory experiments appears to be a direct result of
animals becoming emaciated from prolonged exposure to low food concentrations, a situation which renders them incapable of
high filtering rates. This may explain the Type 3 functional response for field cladocerans, since zooplankton in food-limiting
situations are constantly exposed to low food concentrations, and would therefore have low body carbon and consequently less
energy to filter-feed. We cannot, however, use this to explain the Type 3 response for field diaptomids, since copepods in
the laboratory did not appear to lose body carbon even after 72 h of feeding at very low food levels, and there was inconclusive
evidence that either Diaptomus or Eudiaptomus decrease their filtering rates with acclimation period.
Although Incipient Limiting Concentrations (ILC) for Daphnia ranged from 1 to 8.5 × 103 μg 1−1, more than half of these fell between 1 and 3 × 103 μg l−1, bracketing the value of 2.7 × 102 μg l−1 for field cladocerans. There was, however, a great deal of variation in reported maximum ingestion rates (MIR), maximum filtering
rates (MFR) and ILC values for Daphnia magna. ILC values from the few laboratory studies of freshwater copepods ranged between 0.5 to 2.8 × 103 μg 1−1, and was higher than the ILC value of approximately 0.2 × 103 μg l−1 calculated for field populations of D. minutus. Generally, there was considerable agreement among laboratory studies regarding the shape of grazing-rate and ingestion-rate
curves when data were converted to similar units and presented on standardized scales. 相似文献
9.
10.
Dryland salinity is caused by rising saline water tables, the result of relatively recent landscape-scale clearance of deep-rooted
vegetation. One obvious solution to this problem is the reintroduction of deep-rooted vegetation into these landscapes, most
likely non-deciduous trees. Ideally, continually-transpiring deep-rooted trees would remove moisture from throughout the soil
profile, increasing the capacity of the soil to store water, thus lowering water tables by effectively reducing the number
of rainfall events that contribute to groundwater recharge. In this study, we examined how water use by a Eucalyptus sideroxylon A. Cunn. ex Woolls plantation, growing in a salinity-prone landscape, varied in response to rainfall events across four years
of sap flux monitoring. Responses of the plantation were observed across multiple seasons, from above average to well below
average rainfall. We observed that the plantation forest, while capable of continuous water use during drought, was also quite
responsive to rainfall events. During the driest periods, during which shallow soil moisture was reduced to a stable minimum,
the forest continued using water at around 1 mm/day. Generally we observed increases in forest water use following only 5
mm of rainfall, in contrast to 20 mm for neighbouring native vegetation. We compared a range of plausible empirical models
for describing forest water use responses to rainfall. The best model demonstrated that rainfall size, post-rainfall PET and
the interaction between rainfall size and antecedent soil moisture made significant contributions to variation in forest water
use across rainfall events. Interestingly, the model showed that all else equal, higher antecedent soil moisture tended to
reduce potential increases in forest water use in response to rainfall. 相似文献