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311.
Acute K depletion in the rhizosphere can lead to increased root uptake of radiocesium. Two processes can govern this increase: the very low uptake of potassium and the weathering of Cs-fixing clay minerals. Their respective importance is, however, unknown. We investigated the effects of these processes on radiocesium mobilization by roots of willow (Salix viminalis L.) from three micas: muscovite, biotite, and phlogopite. Willows were grown in a mixed quartz-mica substrate with the three respective (134)Cs-contaminated micas as sole sources of potassium and radiocesium. After 7 wk of plant growth, the micas were partially weathered. The degree of mica weathering and the prevalent potassium concentration in the solution increased in the order muscovite (5-11 microM K) < biotite (25-32 microM K) < phlogopite (25-35 microM K). The mobilization and root uptake of radiocesium were negligible with muscovite but increased in the same order. These results show that mica weathering directly and chiefly governs the mobility of radiocesium in K-depleted rhizosphere soil. The low mobility of trace Cs in the muscovite rhizosphere is linked with the dioctahedral character of this mica, and hence to its very low alterability. 相似文献
312.
Male reproductive performance can vary with condition, age and future reproductive opportunities. Web-building spiders are ideal models to examine the effects of senescence on fitness-related behaviours due to strong selection on male courtship to reduce pre-copulatory sexual cannibalism. Argiope keyserlingi spiders generate courtship vibrations, or ‘shudders’, that reduce female aggression. We found that male A. keyserlingi courtship slowed with chronological age. Older males took longer to travel across the courtship thread, and overall number of shudders increased. Males retained some ability to modulate courtship quality (shudder duration and number of rocks within each shudder) in response to female quality. A change in courtship performance over time, despite strong selection for repeatability, indicates that ageing in male A. keyserlingi may have direct impacts on reproductive performance. 相似文献
313.
Bryna Cosgriff Dunn Anne Steinemann 《Journal of Environmental Planning and Management》1998,41(6):661-672
Industrial ecology is a promising approach that planners can use to create more sustainable communities. This paper examines the scientific basis and planning implications of industrial ecology, which models urban systems on natural systems to increase efficiency and to reduce resource consumption and disposal. A case study of a successful eco-industrial system in Kalundborg, Denmark, demonstrates ways in which industrial ecology can promote key principles of sustainability. We conclude with lessons and directions for the role of planning in industrial ecology. 相似文献
314.
Knowledge of the pelagic vertical distribution of fish eggs is central for several aspects of fisheries science including
fisheries recruitment and egg production studies. In modelling egg vertical distributions, variation in fish egg density is
an important issue. Though variation in egg density between individual eggs has been reported, evidence for significant spatial
variation in egg density is novel. The present study provides evidence that egg density of anchovy (Engraulis encrasicolus) varies spatially across spawning sites in the Bay of Biscay, depending on the regional scale variation in sea water properties
due to river discharge. We measured the density of the eggs using a density gradient column at 17 stations in 2005 and 2006
as well as their diameter. At station, the variability in the individual egg density was statistically distributed according
to a Gaussian probability function. Significant variation in the mean egg density was observed across stations. Mean egg density
displayed a significant correlation with sea surface salinity. Results are discussed in light of the mechanisms determining
the egg density. 相似文献
315.
E. E. G. Clavico G. Muricy B. A. P. da Gama D. Batista C. R. R. Ventura R. C. Pereira 《Marine Biology》2006,148(3):479-488
In the Brazilian coast, high numbers of the small brittle star Ophiactis savignyi usually live associated with the sponge Geodia corticostylifera (Demospongiae, Geodidae), but not with other sympatric sponge species. In order to check whether this association was related
only with the physical shelter provided by the sponge body or was chemically mediated, the crude organic extract of G. corticostylifera was added to sponge mimics made of phytagel and spongin skeleton. Control and treated mimics were simultaneously offered
to previously sponge-associated O. savignyi in both static seawater and flow-through laboratory experiments. Ophiuroids were allowed to move towards the preferred mimic.
The defensive properties of the sponge extract against fish predation and fouling were also evaluated. Chemotaxis assays showed
that symbiotic ophiuroids were able to chemically recognize its host sponge, moving significantly more towards mimics containing
G. corticostylifera extract. Chemical deterrence assays showed that the natural concentration of the extract of this sponge was also able to
inhibit generalist fish predation on field experiments and the attachment of the common mussel Perna perna in laboratory assays. These results indicate that the crude extract of G. corticostylifera plays multiple functions in the marine environment, presumably being responsible for a closer association of this sponge
with O. savignyi, providing protection for this ophiuroid and inhibition of epibionts on itself. 相似文献
316.
Yannick Outreman Anne Le Ralec Eric Wajnberg Jean-Sébastien Pierre 《Behavioral ecology and sociobiology》2005,58(2):208-217
The present study aimed to address how an insect parasitoid makes patch-departure decisions from various types of host patches and how previous patch experiences in the environment modify this decision-making process. Experiments were done with the parasitic wasp Aphidius rhopalosiphi attacking the grain aphid Sitobion avenae. In the experiments, wasps were observed in a laboratory environment containing several patches of various host densities, and behavioural records were analysed using a Coxs proportional hazards model. Consideration of the effect of the within-patch experience gave a classic pattern of patch-leaving decision rules in parasitoids: A. rhopalosiphi used local information on host quality (i.e. numbers of ovipositions or rejections) and availability (i.e. patch density) to determine departure decision. However, consideration of previous patch experiences provided evidence that these departure rules are fundamentally dynamic, responding to the physiological state of the animal and the information it has about its environment. Results showed that A. rhopalosiphi decreased its tendency to leave the visited patch after an oviposition. However, when a female has already laid several other eggs in the environment, such an incremental mechanism gradually switched to a decremental one. Hence, A. rhopalosiphi responded to egg-load depletion by leaving the visited patches sooner and by depositing a smaller number of eggs in those patches, which probably led to a decreased level of superparasitism. Results also indicated that previous experiences enabled wasps to estimate spatial host distribution and then to adjust their behavioural decisions accordingly. Thus, A. rhopalosiphi was shown to adjust its patch residence time according to the quality and the number of the patches previously visited. These proximate mechanistic rules adopted by A. rhopalosiphi females are discussed in the context of general predictions from optimality models.Communicated by D. Gwynne 相似文献
317.
Parentage analysis of multi-male social groups of tasmanian native hens (Tribonyx mortierii): genetic evidence for monogamy and polyandry 总被引:4,自引:0,他引:4
H. Lisle Gibbs Anne W. Goldizen Cindy Bullough Alan R. Goldizen 《Behavioral ecology and sociobiology》1994,35(5):363-371
Accurate estimates of male reproductive success are essential to understanding the evolution of polyandrous mating systems. Here, we use multilocus DNA fingerpinting to assess parentage in an island population of Tasmanian native hens (Tribonyx mortierii), which often live in multi-male and/or multi-female social groups. This isolated population presented special challenges to this technique because it was artificially founded from a small number of individuals in the recent past. DNA profiles from four multilocus minisatellite probes were analyzed for adults and offspring from six social groups using two methods: (1) significance of band-sharing coefficients and (2) distribution among a group's offspring of fragments unique to certain adults. Traditional band-sharing analyses did not provide sufficient resolution to establish parentage in this population due to the high level of band-sharing between adults within groups. In contrast, the distribution of unique fragments suggests that in most cases, all offspring within a group have the same male and female genetic parents, so that monogamy may be the predominant genetic mating system of this species. This forces a rexamination of the evolutionary basis of polyandry in these birds. It also demonstrates some of the difficulties in using these highly polymorphic genetic markers for parentage analyses when putative parents are closely related. 相似文献
318.
319.
Mass mortality of echinoids is well documented, and has potentially profound effects on benthic communities. However, no study to date has quantitatively investigated how regular, predictable events such as winter storms might lead to large mortality events in pivotal echinoid species. Hydrodynamic disturbances can be major drivers of crucial biological processes in benthic communities. For echinoid populations in particular, wave action in shallow waters generated by high winds (winter storms) can cause displacement, damage and even death to individuals. However, evidence for displacement-mediated mortality is scant in the literature, in part because it is so difficult to demonstrate in exposed environments where echinoids are frequently found. In this study, we examined mortality in a sheltered subtidal population of the European purple sea urchin Paracentrotus lividus over a 3-year period, and examined the role that dislodgement by wave action or predation might play in these mortality patterns. Because our study population has been in decline for the past three decades, we considered it important to evaluate its current status in addition to assessing the contribution that adult mortality makes to that decline. We sampled twice per month, using the density of freshly dead echinoid material to assess the extent of adult mortality. The Irish Meteorological Service provided our estimates of wind speed data. We compared historical and recent data on P. lividus size frequency data to investigate change the population structure (Poor recruitment would be caused by failure to spawn over a prolonged period). Our data suggest ongoing declines in this population, and support the theory that the decline of the P. lividus population of Lough Hyne is a result of persistent recruitment failure linked to repeated cool maximum sea surface temperatures. Although we found peaks of P. lividus mortality were coincident with spikes in wind speed, mortality was low, and seems unlikely to have contributed significantly to the dramatic decline in P. lividus in the past three decades.Communicated by J.P. Thorpe, Port Erin 相似文献
320.
Renström A 《Journal of environmental monitoring : JEM》2002,4(5):619-622
A number of methods are used to assess exposure to high-molecular weight allergens. In the occupational setting, airborne dust is often collected on filters using pumps, the filters are eluted and allergen content in the eluate analysed using immunoassays. Collecting inhalable dust using person-carried pumps may be considered the gold standard. Other allergen sampling methods are available. Recently, a method that collects nasally inhaled dust on adhesive surfaces within nasal samplers has been developed. Allergen content can be analysed in eluates using sensitive enzyme immunoassays, or allergen-bearing particles can be immunostained using antibodies, and studied under the microscope. Settling airborne dust can be collected in petri dishes, a cheap and simple method that has been utilised in large-scale exposure studies. Collection of reservoir dust from surfaces using vacuum cleaners with a dust collector is commonly used to measure pet or mite allergens in homes. The sampling methods differ in properties and relevance to personal allergen exposure. Since methods for all steps from sampling to analysis differ between laboratories, determining occupational exposure limits for protein allergens is today unfeasible. A general standardisation of methods is needed. 相似文献