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31.
Na’ama Morag Ally R. Harari Amos Bouskila Tamar Keasar 《Behavioral ecology and sociobiology》2011,65(12):2287-2296
Mothers can epigenetically influence their progeny’s characteristics in response to environmental conditions they experience,
thereby increasing offspring adaptation to anticipated future conditions. When resource shortage is anticipated, females are
expected to produce larger offspring, as large body size often confers competitive and dispersal advantages. We tested this
hypothesis using the polyembryonic parasitoid, Copidosoma koehleri. In this wasp, each egg proliferates into a clone of genetically identical individuals within its moth host, and body size
correlates negatively with clone size. We expected females anticipating resource limitation to produce fewer and larger offspring
per clone than females that anticipate abundant resources. Encounter rates of parasitoid females with hosts were manipulated
to simulate varying levels of resource availability. High-encounter-rate females were introduced to ten hosts successively,
while low-encounter-rate females encountered each of ten hosts at 8-h intervals. To control for female age at oviposition,
we also introduced females at different ages to a single host. Contrary to our predictions, low-encounter-rate females produced
larger offspring clones than high-encounter-rate females, and offspring body size did not differ between treatments. Low-encounter-rate
females were shorter-lived than females that encountered hosts successively. Single-oviposition females resembled the high-encounter-rate
females in longevity but produced as many offspring per clone as in the low-encounter-rate treatment. Female age, and number
of previous host encounters, did not affect offspring clone size. These results suggest that offspring proliferation bears
a cost to mothers, thus mothers that repeatedly induce high proliferation in their offspring pay an increased price. 相似文献
32.
33.
Osnat Malka Shiri Shnieor Abraham Hefetz Tamar Katzav-Gozansky 《Behavioral ecology and sociobiology》2007,61(3):465-473
In most social insects, worker sterility is reversible, and in the absence of the queen, at least some workers develop ovaries and lay male-destined eggs. In the honeybee, reproductive workers also produce queen-characteristic mandibular and Dufour’s pheromones. The evolution of worker sterility is still under debate as to whether it is caused by queen manipulation (queen-control hypothesis) or represents worker fitness maximization (worker-control hypothesis). In this study, we investigated whether worker fertility and royal pheromone production are reversible under the queen influence. To that effect, we induced ovary activation and queen pheromone production in workers by rearing them as queenless (QL) groups. These workers were subsequently reintroduced into queenright (QR) microcolonies for 1 week, and their ovary status and queen pheromone levels were monitored. Workers reintroduced into QR, but not QL colonies, showed a clear regression in ovary development and levels of the queen pheromones. This is the first demonstration that worker sterility and/or fertility is reversible and is influenced by the queen. These results also emphasize the robustness of the coupling between ovary activation and royal pheromone production, as well as lending credence to the queen-control hypothesis. The dynamics of queen pheromone production in QL workers supports the role of Dufour’s gland pheromone as a fertility signal and that of the mandibular gland pheromone in dominance hierarchies.The two authors, Osnat Malka and Shiri Shnieor, contributed equally to this work. 相似文献
34.
The short-spined toxopneustid sea urchin Tripneustes gratilla feeds on a wide variety of algal species and on sea grasses. However, the urchin does show preferences when offered a selection
of macroalgal species, which it encounters in nature. Preferences among macroalgae were evident in field-collected urchins
exposed to pair-wise tests where the variable was either the consumption rate of the algae or observation of which algal species
the urchins chose to touch with their lantern teeth. Exposure of lab-housed urchins to one of five species of macroalgae for
5 months did not seem to alter preferences of urchins in three of the exposure groups, but those exposed to Padina sanctae-crucis seemed to show an enhanced preference for this species when offered a choice of the five species of macroalgae at the end
of the exposure period, and those exposed to Gracilaria salicornia seemed to avoid the species when offered the choice of the five species. Perhaps more ecologically important than their preferences
were two other observations on these urchins: first, when offered only a single species of algae, the urchins on four of five
diets ate the same quantity per day. Second, when simultaneously offered the choice among the five macroalgal species, the
urchins consumed more macroalgae per day than when offered only one species. These urchins move about a meter a day. They
probably encounter food resources in a relatively coarse-grained fashion and have evolved to eat what is available. Because
of their limited movements, their habitat overlap with grazing fishes, their acceptance of a wide variety of macroalgae and
their preference for macroalgae, these native urchins are thought to have the potential to serve as biological control agents
of alien and invasive macroalgae, which have come to dominate some reef zones normally occupied by corals in Hawaii. 相似文献
35.
Symbiont specificity and bleaching susceptibility among soft corals in the 1998 Great Barrier Reef mass coral bleaching event 总被引:1,自引:0,他引:1
Considerable variability in bleaching was observed within and among soft coral taxa in the order Alcyonacea (Octocorallia:
Cnidaria) on the central Great Barrier Reef (GBR, latitude 18.2°–19.0°S, longitude 146.4°–147.3°E) during the 1998 mass coral
bleaching event. In April 1998, during a period of high sea surface temperatures, tissue samples were taken from bleached
and unbleached colonies representative of 17 soft coral genera. The genetic identities of intracellular dinoflagellates (Symbiodinium spp.) in these samples were analyzed using PCR-denaturing gradient gel electrophoresis fingerprinting analysis of the internal
transcribed spacer regions 1 and 2. Alcyonaceans from the GBR exhibited a high level of symbiont specificity for Symbiodinium types mostly in clade C. A rare clade D type (D3) was associated only with Clavularia koellikeri, while Nephthea sp. hosted symbionts in clade B (B1n and B36). Homogenous Symbiodinium clade populations were detected in all but one colony. Colonies that appeared bleached possessed symbiont types that were
genetically indistinguishable from those in nonbleached conspecifics. These data suggest that parameters other than the resident
endosymbionts such as host identity and colony acclimatization are important in determining bleaching susceptibility among
soft corals.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
36.
K David Hambright Tamar Zohary Werner Eckert Steven S Schwartz Claire L Schelske Kathleen R Laird Peter R Leavitt 《Ecological applications》2008,18(7):1591-1603
Exploitation of freshwater resources is having catastrophic effects on the ecological dynamics, stability, and quality of those water resources on a global scale, especially in arid and semiarid regions. Lake Kinneret, Israel (the Biblical Sea of Galilee), the only major natural freshwater lake in the Middle East, has been transformed functionally into a reservoir over the course of approximately 70 years of hydrological alterations aimed mostly at producing electrical power and increasing domestic and agricultural water supply. Historical changes in lake chemistry and biology were reconstructed using analysis of sedimentary nutrient content, stable and radioisotope composition, biochemical and morphological fossils from algae, remains of aquatic invertebrates, and chemical indices of past light regimes. Together, these paleolimnological analyses of the lake's bottom sediments revealed that this transformation has been accompanied by acceleration in the rate of eutrophication, as indicated by increased accumulation rates of phosphorus, nitrogen, organic matter, phytoplankton and bacterial pigments, and remains of phytoplankton and zooplankton. Substantial increases in these indices of eutrophication coincide with periods of increased water-level fluctuations and drainage of a major upstream wetland in the early to middle 20th century and suggest that management of the lake for increased water supply has degraded water quality to the point that ecosystem stability and sustainability are threatened. Such destabilization may be a model for eutrophication of freshwater lakes in other arid regions of the world in which management emphasizes water quantity over quality. 相似文献
37.
Ingrid Hillmer Penelope van Reenen Jrg Imberger Tamar Zohary 《Ecological modelling》2008,218(1-2):49-59
Phytoplankton concentration in Lake Kinneret (Israel) has varied up to 10-fold in space and time, with horizontal patches ranging from a couple of kilometres to a basin scale. Previous studies have used a 1D model to reproduce the temporal evolution of physical and biogeochemical variables in this lake. The question that arises then is how appropriate is a 1D approach to represent the dynamic of a spatially heterogeneous system, where there are non-linear dependencies between variables. Field data, a N-P-Z model coupled to both a 1D and a 3D hydrodynamic model, a 1D diffusion-reaction equation and scaling analysis are used to understand the role of spatial variability, expressed as phytoplankton patchiness, in the modelling of primary production. The analysis and results are used to investigate the effect of horizontal variability in the forcing and in the free mechanisms that affect the growth of patterns. The study shows that the use of averaged properties in a 1D approach may produce misleading results in the presence of localised patches, in terms of both concentration and composition of phytoplankton. The reason lies in the fact that the calibration process of ecological parameters in the 1D model appears to be site and process specific. That is, it depends on the pattern's characteristics and the underlying physical processes causing them. And this is a critical point for the success of numerical simulations under spatial variability. In this study, it is also shown that a length scale based on diffusion and growth rate of phytoplankton could be used as a criterion to assess the appropriateness of the 1D assumption. 相似文献
38.
Tamar Drezner-Levy Brian H. Smith Sharoni Shafir 《Behavioral ecology and sociobiology》2009,64(1):135-148
Honey bee foragers may collect nectar, pollen, water, or propolis, and their foraging specialization has been associated with
several behavioral traits. By conditioning of the proboscis extension response (PER), we compared the performance of foragers
that collected nectar, pollen, both nectar and pollen, or water in several learning and choice assays. Foragers were first
tested in a three-trial olfactory associative learning assay. For further tests, we selected only good learners that responded
in two out of three conditioning trials. One group was tested in an additional olfactory associative learning assay involving
different reward volumes and concentrations. Another group was tested for risk sensitivity in a two-alternative forced-choice
PER procedure and then in a latent inhibition (LI) assay. Levels of acquisition in olfactory associative learning were highest
in pollen and water foragers, and better acquisition was associated with collection of heavier pollen loads and smaller and
lighter nectar loads of lower sugar concentration. Among the good learners, pollen foragers still showed better acquisition
than nectar foragers when rewarded with several volumes and concentrations of sucrose solution. Pollen and nectar foragers
were equally risk averse, preferring a constant reward to a variable one, and choice was not affected by pollen load weight.
Contrary to a previous study, pollen and nectar foragers were similarly affected by LI. We discuss possible explanations for
the discrepancy between the two studies. Overall, our results suggest that differences between foraging groups in sensitivity
to various stimuli may not correspond to differences in choice behavior. 相似文献
39.
Pharmaceuticals and personal care products (PPCPs) represent pollutants of emerging concern, originating in surface and drinking waters largely from their persistence in wastewater effluent. Accordingly, a wealth of recent investigations has examined PPCP fate during wastewater treatment, focusing on their removal during conventional (e.g., activated sludge) and advanced (e.g., ozonation and membrane filtration) treatment processes. Here, we compile nearly 1500 data points from over 40 published sources pertaining to influent and effluent PPCP concentrations measured at pilot- and full-scale wastewater treatment facilities to identify the most effective series of technologies for minimizing effluent PPCP levels. Available data suggest that at best a 1-log(10) concentration unit (90%) of PPCP removal can be achieved at plants employing only primary and secondary treatment, a performance trend that is maintained over the range of reported PPCP influent concentrations (ca. 0.1-10(5) ng L(-1)). Relatively few compounds (15 of 140 PPCPs considered) are consistently removed beyond this threshold at facilities using solids removal and conventional activated sludge (CAS), and most PPCPs are removed to a far lesser extent. Further, increases in CAS hydraulic retention time or sludge retention time do not appreciably increase removal beyond this limit. In contrast, plants employing advanced treatment methodologies, particularly ozonation and/or membranes, remove the vast majority of PPCPs beyond 1-log(10) concentration unit and oftentimes to levels below analytical detection limits in effluent. Data also indicate that passive approaches for tertiary treatment (e.g., wetlands and lagoons) represent promising options for PPCP removal. We conclude by addressing future challenges and frontiers in wastewater management posed by PPCPs including analytical needs for their real-time measurement, energy demands associated with advanced treatment technologies, and byproducts arising from transformation of PPCPs during treatment. 相似文献
40.
Dissolved silica species are naturally occurring, ubiquitous groundwater constituents with corrosion-inhibiting properties. Their influence on the performance and longevity of iron-based permeable reactive barriers for treatment of organohalides was investigated through long-term column studies using Connelly iron as the reactive medium. Addition of dissolved silica (0.5 mM) to the column feed solution led to a reduction in iron reactivity of 65% for trichloroethylene (TCE), 74% for 1,1,2-trichloroethane (1,1,2-TCA), and 93% for 1,1,1-trichloroethane (1,1,1-TCA), compared to columns operated under silica-free conditions. Even though silica adsorption was a gradual process, the inhibitory effect was evident within the first week, with subsequent decreases in reactivity over 288 days being relatively minor. Lower concentrations of dissolved silica species (0.2 mM) led to a lesser decrease (70%) in iron reactivity toward 1,1,1-TCA. The presence of dissolved silica species produced a shift in TCE product distribution toward the more highly chlorinated product cis-dichloroethylene (cis-DCE), although it did not appear to alter products originating from the trichloroethanes. The major corrosion products identified were magnetite (Fe3O4) or maghemite (gamma-Fe2O3) and carbonate green rust ([Fe4(2+)Fe(2)3+(OH)12][CO(3).2H2O]). Iron carbonate hydroxide (Fe(II)1.8Fe(III)0.2(OH)2.2CO3) was only found in the silica-free column, indicating that silica may hinder its formation. A comparison with columns operated under the same conditions, but using Master Builder iron as the reactive matrix, showed that Connelly iron is initially less reactive, but performs better than Master Builder iron over 288 days. 相似文献