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71.
We estimated silicate uptake kinetics for 8 spring diatom species using a model based on time series measurements of the depletion
of dissolved silicate (DSi) and increases in biomass. Furthermore, the carbon: nitrogen: silicate stoichiometric relationships
and maximum growth rates were determined. Differences in DSi uptake kinetics and maximum growth rate were distinct among the
species. All the most common diatom species (Chaetoceros wighamii, Pauliella taeniata, Skeletonema costatum and Thalassiosira baltica) were relatively lightly silicified and had variable but relatively low half-saturation constants (K
s
), indicating that they are well adapted to low DSi concentrations. The less common Diatoma tenuis and Nitzschia frigida had higher K
s
values, suggesting that they are more vulnerable to DSi limitation. The much used nitrogen:silicate ratio of 1 for marine
diatom biomass was too low for most of the examined species, while a ratio of 2–3 seems to be more appropriate for these Baltic
Sea species. 相似文献
72.
Manfred Ayasse Wolf Engels Gunter Lübke Timo Taghizadeh Wittko Francke 《Behavioral ecology and sociobiology》1999,45(2):95-106
The present paper reports on behavioral experiments and gas chromatographic analysis of chemical communication in the mating
biology of the primitively eusocial sweat bee Lasioglossum (Evylaeus) malachurum. In a dual-choice experiment, a female made odorless was significantly less attractive than an untreated one. Attraction in
L. (Evylaeus) malachurum is therefore mediated by a female-produced sex pheromone. Further bioassays showed that unmated gynes are more attractive
to males than mated ones. Males are able to differentiate between the two groups of females as little as 3 h after mating.
Biotests with different samples obtained from attractive gynes showed surface extracts to be most attractive. Behavioral tests
with synthetic copies of the compounds identified as cuticular constituents of virgin gynes were highly attractive to males;
the volatile bouquets consisting of n-alkanes, n-alkenes and iso- pentenyl esters of unsaturated fatty acids were the most
attractive samples. Isopentenyl esters of unsaturated fatty acids were the key compounds in inducing male inspections as well
as stimulating pounces and copulatory attempts. Virgin and nesting gynes differed clearly in the relative and absolute amounts
of the volatiles on the cuticle. The total amount of volatiles was significantly higher in virgin gynes and decreased in breeding
queens. Hydrocarbons were the dominant group of compounds in both groups of females. The relative amounts of the wax-type
ester, hexadecyl oleate, iso- pentenyl esters, and a hitherto unidentified steroid were higher in attractive virgin gynes,
while the relative proportions of hydrocarbons and lactones dominated in nesting queens. The site of sex pheromone production
in attractive young L. (Evylaeus) malachurum gynes remains unknown. Head glands or Dufour's gland secretions may be involved. Another possible source of the `active principle'
found among the cuticular lipids could be glandular cells of the epidermis. The significance of modulation of female sex pheromone
composition is discussed in terms of a reduction in mating expenditures.
Received: 30 April 1998 / Accepted after revision: 24 July 1998 相似文献
73.
Timo Thünken Theo C. M. Bakker Sebastian A. Baldauf 《Behavioral ecology and sociobiology》2014,68(1):99-104
Kin discrimination in nepotistic as well as in sexual contexts is widespread in animals including humans. However, the underlying mechanisms of kin discrimination are assumed to vary between species and—within species—between contexts. During solitary life stages, kin recognition based on social learning is assumed to be less reliable because kin templates that are not continuously updated may get lost. Therefore, self-referent phenotype matching (“armpit effect”), i.e., the comparison of unknown phenotypes with own characteristics, should be particularly relevant when no social cues are available. However, experimental evidence for this mechanism is scarce. Here, we examine self-referent kin recognition in a mate-choice context in adult male Pelvicachromis taeniatus, a socially monogamous cichlid fish from West Africa with biparental brood care and pronounced kin-mating preferences. Juvenile P. taeniatus live in groups, whereas adult males compete for access to breeding sites which they aggressively defend against rivals. Using computer-animated females as standardized visual stimuli in combination with olfactory cues of related and unrelated females, we show that adult males reared isolated from kin since egg stage were able to discriminate sisters from unrelated females. As males could have learned kin cues only from themselves, our study provides evidence for self-referent kin recognition and indicates that the observed inbreeding preferences are mediated by self-derived olfactory cues. Male preferences for sisters were correlated with male body size. We discuss the implications of quality-related mate choice for the evolution of kin-mating preferences. 相似文献
74.
The aim of this study was to investigate the relationship between organizational climate and driver behaviours of professional drivers. The sample consisted of 230 male professional drivers. The participants completed a questionnaire including the Driver Behaviour Questionnaire (DBQ), Hofstede’s Organizational Culture Scale, and a background information form. Results of the factor analysis of Hofstede’s Organizational Culture Scale yielded two dimensions, which were named as “work orientation” and “employee consideration”. Analyses of Covariance (ANCOVA) revealed significant main and interaction effects of organizational climate on errors, and violations after controlling for the statistical effects of age, annual mileage and the organization types. Drivers with low scores of work orientation reported significantly higher frequencies of errors and violations than drivers with high scores of work orientation. It was also found that drivers with low scores of employee consideration reported higher frequencies of errors and violations than drivers with high scores of employee consideration. The effect of interaction between work orientation and employee consideration dimensions was only found on the frequencies of violations. 相似文献
75.
Antti J. Koivisto Tareq Hussein Raimo Niemelä Timo Tuomi Kaarle Hämeri 《Atmospheric environment (Oxford, England : 1994)》2010,44(17):2140-2146
In this study, we present how an indoor aerosol model can be used to characterize particle emitter and predict influence of the source on indoor air quality. Particle size-resolved emission rates were quantified and the source’s influence on indoor air quality was estimated by using office model simulations. We measured particle emissions from three modern laser printers in a flow-through chamber. Measured parameters were used as input parameters for an indoor aerosol model, which we then used to quantify the particle emission rates. The same indoor aerosol model was used to simulate the effect of the particle emission source inside an office model. The office model consists of a mechanically ventilated empty room and the particle source. The aerosol from the ventilation air was a filtered urban background aerosol. The effect of the ventilation rate was studied using three different ventilation ratios 1, 2 and 3 h?1. According to the model, peak emission rates of the printers exceeded 7.0 × 108 s?1 (2.5 × 1012 h?1), and emitted mainly ultrafine particles (diameter less than 100 nm). The office model simulation results indicate that a print job increases ultrafine particle concentration to a maximum of 2.6 × 105 cm?3. Printer-emitted particles increased 6-h averaged particle concentration over eleven times compared to the background particle concentration. 相似文献
76.
Stenberg M Hamers T Machala M Fonnum F Stenius U Lauy AA van Duursen MB Westerink RH Fernandes EC Andersson PL 《Chemosphere》2011,85(9):1423-1429
The non-dioxin-like PCBs (NDL-PCBs) found in food and human samples have a complex spectrum of adverse effects, but lack a detailed risk assessment. The toxicity profiles of 21 carefully selected PCBs (19 NDL-PCBs) were identified by in vitro screening in 17 different assays on specific endpoints related to neurotoxicity, endocrine disruption and tumor promotion. To ensure that the test results were not affected by polychlorinated dioxins, dibenzofurans or DL-PCB contaminants, the NDL-PCB congeners were thoroughly purified before testing. Principal component analysis (PCA) was used to derive general toxicity profiles from the in vitro screening data. The toxicity profiles indicated different structure-activity relationships (SAR) and distinct mechanisms of action. The analysis also indicated that the NDL-PCBs could be divided into two groups. The first group included generally smaller, ortho-substituted congeners, comprising PCB 28, 47, 51, 52, 53, 95, 100, 101, 104 and 136, with PCB 95, 101 and 136 as generally being most active. The second group comprising PCB 19, 74, 118, 122, 128, 138, 153, 170, 180 and 190 had lower biological activity in many of the assays, except for three endocrine-related assays. The most abundant congeners, PCB 138, 153, 170, 180 and 190, cluster in the second group, and thereby show similar SAR. Two quantitative structure-activity relationship (QSAR) models could be developed that added information to the SAR and could aid in risk assessments of NDL-PCBs. The QSAR models predicted a number of congeners as active and among these e.g., PCB 18, 25, 45 and 49 have been found in food or human samples. 相似文献
77.
Petra Brenerová Timo Hamers Jorke H. Kamstra Jan Vondráček Simona Strapáčová Patrik L. Andersson Miroslav Machala 《Environmental science and pollution research international》2016,23(3):2099-2107
The relative potencies of non-ortho-substituted coplanar polychlorinated biphenyl (PCB) congeners to activate the aryl hydrocarbon receptor (AhR) and to cause the AhR-dependent toxic events are essential for their risk assessment. Since some studies suggested that abundant non-dioxin-like PCB congeners (NDL-PCBs) may alter the AhR activation by PCB mixtures and possibly cause non-additive effects, we evaluated potential suppressive effects of NDL-PCBs on AhR activation, using a series of 24 highly purified NDL-PCBs. We investigated their impact on the model AhR agonist-induced luciferase reporter gene expression in rat hepatoma cells and on induction of CYP1A1/1B1 mRNAs and deregulation of AhR-dependent cell proliferation in rat liver epithelial cells. PCBs 128, 138, and 170 significantly suppressed AhR activation (with IC50 values from 1.4 to 5.6 μM), followed by PCBs 28, 47, 52, and 180; additionally, PCBs 122, 153, and 168 showed low but still significant potency to reduce luciferase activity. Detection of CYP1A1 mRNA levels in liver epithelial cells largely confirmed these results for the most abundant NDL-PCBs, whereas the other AhR-dependent events (CYP1B1 mRNA expression, induction of cell proliferation in confluent cells) were less sensitive to NDL-PCBs, thus indicating a more complex regulation of these endpoints. The present data suggest that some NDL-PCBs could modulate overall dioxin-like effects in complex mixtures. 相似文献
78.
Tervahauta AI Fortelius C Tuomainen M Akerman ML Rantalainen K Sipilä T Lehesranta SJ Koistinen KM Kärenlampi S Yrjälä K 《Environmental pollution (Barking, Essex : 1987)》2009,157(1):341-346
Two birch clones originating from metal-contaminated sites were exposed for 3 months to soils (sand-peat ratio 1:1 or 4:1) spiked with a mixture of polyaromatic hydrocarbons (PAHs; anthracene, fluoranthene, phenanthrene, pyrene). PAH degradation differed between the two birch clones and also by the soil type. The statistically most significant elimination (p ≤ 0.01), i.e. 88% of total PAHs, was observed in the more sandy soil planted with birch, the clearest positive effect being found with Betula pubescens clone on phenanthrene. PAHs and soil composition had rather small effects on birch protein complement. Three proteins with clonal differences were identified: ferritin-like protein, auxin-induced protein and peroxidase. Differences in planted and non-planted soils were detected in bacterial communities by 16S rRNA T-RFLP, and the overall bacterial community structures were diverse. Even though both represent complex systems, trees and rhizoidal microbes in combination can provide interesting possibilities for bioremediation of PAH-polluted soils. 相似文献
79.
Ekholm P Jouttijärvi T Priha M Rita H Nurmesniemi H 《Environmental pollution (Barking, Essex : 1987)》2007,145(3):715-722
We determined the potentially algal-available P (P(aa)) in pulp and paper mill effluents by two bioassay techniques (a dual-culture assay and a batch approach) and compared it with chemically analysed P (total P, total dissolved P, reactive P, dissolved reactive P and dissolved hydrolysable P). The mean P(aa) given by the dual-culture assay was within a 40% range of that given by the batch approach. The P(aa) obtained by both bioassays differed from total P. Dissolved reactive P appeared to be the most readily available chemical P fraction, but other P fractions also contributed to P(aa). The analysis of reactive P, which involves direct staining of an unfiltered sample, best approximated the P(aa) given by the dual-culture assay (relative error 9%). The results suggest that assessment of eutrophying effluent P can be improved by analysing simple chemical P fractions in wastewater. The fractions to be analysed, however, may be site specific. 相似文献
80.
A number of chemicals released into the environment share structural similarity to the thyroid hormones (THs), thyroxine (T(4)) and triiodothyronine (T(3)) and it is thought that they may interfere with the thyroid axis and behave as endocrine disruptors (EDs). One of the ways by which such environmental contaminants may disrupt the TH axis is by binding to TH transporter proteins. Transthyretin (TTR) is one of the thyroid hormone binding proteins responsible for TH transport in the blood. TTR forms a stable tetramer that binds both T(4) and T(3) and in fish it is principally synthesized in the liver but is also produced by the brain and intestine. In the present study, we investigate the ability of some chemicals arising from pharmaceutical, industrial or agricultural production and classified as EDs, to compete with [I(125)]-T(3) for sea bream recombinant TTR (sbrTTR). Ioxinyl, a common herbicide and several polybrominated diphenyl ethers were strong inhibitors of [I(125)]-T(3) binding to TTR and some showed even greater affinity than the natural ligand T(3). The TTR competitive binding assay developed offers a quick and effective tool for preliminary risk assessment of chemicals which may disrupt the thyroid axis in teleost fish inhabiting vulnerable aquatic environments. 相似文献