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961.
The mantle dermal formations (MDFs) ofHypselodoris webbi (D'orbigny, 1839), andH. cantabrica (Bouchet and Ortea, 1980) are globular sub-epidermal structures located in the cephalic and caudal regions. Histologically they consist of an accumulation of vacuolate cells surrounded by a basal lamina and an outer muscular capsule. Chemical analysis ofH. webbi MDFs reveals the presence of high concentrations of longifolin, a well known deterrent furanosesquiterpenoid that had been previously isolated from this species. In the present paper it is demonstrated that the great majority of longifolin accumulated in the mantle ofH. webbi is stored in the MDF vacuolar cells. This finding strongly suggests that such structures act as chemical weapons against predation, mainly protecting vital organs such as the head, rhinophores and gills. 相似文献
962.
Testosterone stress does not increase asymmetry of a hormonally mediated sexual ornament in a lizard
José P. Veiga Alfredo Salvador Pilar López José Martin 《Behavioral ecology and sociobiology》1997,41(3):171-176
The theory that fluctuating asymmetry is sensitive to both environmental and genetic stress is gaining acceptance among evolutionary
biologists. Most empirical work has focused on ornamental traits on the assumption that they are more susceptible to stress.
In tegumentary coloration is a common ornament in nature, and frequently has a hormonal basis. Earlier studies in the lizard
Psammodromus algirus indicate that testosterone induces the development of head nuptial coloration in large males and, at the same time, produces
an increase of the ectoparasite load and higher mortality. Hence, the manipulation of testosterone levels may be a way to
increase ornament expression and simultaneously create conditions that may make symmetrical development difficult. This positive
covariation between character size and symmetry is opposite to that expected in theory for sexually selected traits, so the
predicted elevation of asymmetry due to the treatment cannot be confounded by any intrinsic association between symmetry and
character size. We firstly consider the effect that testosterone supplementation has on two variables that reflect the symmetry
of bilateral throat nuptial coloration in large P. algirus males. Also, we examine whether ornament symmetry is positively associated with reproductive success, a prediction of theory
of sexually selected symmetry. Testosterone treatment did not increase the fluctuating asymmetry of throat coloration. Size
asymmetry increased with character size in individuals with a fragmented colour pattern, but changed suddenly to a highly
symmetric pattern in individuals with non-fragmented coloration. Mirror asymmetry decreased steadily with character size.
These results suggest that the development of coloration on both sides of the throat midline follows a random pattern. Asymmetry
did not correlate with variables that estimated reproductive success, suggesting that asymmetry is not affected by physiological
stress and that this trait is not a sexually selected signal in P. algirus.
Received: 1 July 1996 / Accepted after revision: 4 May 1997 相似文献
963.
Some organisms use morphological structures obtained by behavioural processes to lower mortality by predation. We test whether
larvae of the limnephilid caddisfly Potamophylax latipennis (Curtis) vary their responses to the presence of different predators (dragonfly naiads, fire salamander larvae or brown trout)
by choosing organic or mineral cases. We offered both case types to larvae, and simulated differences in predation risk using
water conditioned with chemicals from the different predators. Our results show that Potamophylax larvae detect and discriminate predators using water-borne chemical cues and alter their choice of case type according to
the perceived predation risk. Moreover, the distribution of larvae bearing cases of different anti-predator value matches
the spatial variation in predation risk in the field. 相似文献
964.
Summary. The plant apparency hypothesis predicts that apparent plants invest in broadly effective defences such as tannins while unapparent
plants invest in specific toxins such as alkaloids. The stress hypothesis states that plants invest in cheaper defences if
they have evolved in habitats that impose abiotic limitations to plant fitness. We tested these hypotheses by determining
the concentrations of alkaloids and tannins in a representative sample of the vascular plants of continental Chile (with exclusion
of Pteridophyta, Cactaceae, and Poaceae) consisting of 396 species. In a subsample of 166 species which contained both alkaloids
and tannins, we constructed the A/T index (A/T = [alkaloids]/ [tannins]). We discarded the presumed effect of phylogeny (as
estimated by taxonomy) on the variation observed in the data because no correlation of A/T with taxonomic relationships among
species either at family or genus levels was found in a nested ANOVA with genera nested in families. Concentration of alkaloids
was negatively correlated with that of tannins. We compared the value of A/T among species differing in life form (herbs,
shrubs or trees), herb longevity (annual or perennial), leaf-shedding manner of woody plants (deciduous or evergreen), latitudinal
range, and level of water stress typical in their natural habitat. Unapparent plants (herbs, annual) exhibited higher mean
A/T index than apparent plants (shrubs and trees, perennial). A/T did not correlate with latitudinal range. Mean A/T values
decreased from deserts to deciduous forests. The comparisons were not always significant due to the inevitable unbalance of
the data set which lowers the power of the statistical tests employed. The results suggest that chemical defences are indeed
distributed in a non-random manner among plants, and that to a large extent the predictions derived from the apparency and
stress hypotheses are sustained. 相似文献
965.
Allelopathic potential of Cistus ladanifer chemicals in response to variations of light and temperature 总被引:2,自引:0,他引:2
Natividad Chaves Lobón Juan Carlos Alias Gallego Teresa Sosa Diaz José Carlos Escudero Garcia 《Chemoecology》2002,12(3):139-145
Summary. Earlier studies have demonstrated the allelopathic potential of the exudate of Cistus ladanifer leaves, and have identified the compounds responsible for the effect. It is here shown that the effect of each of these compounds
and their interactions on germination and seedling development varies depending on the light and temperature parameters to
which they are subjected. The allelochemicals show a fairly heterogeneous response when studied separately, there being no
general pattern to the behaviour. When they act conjointly, however, their activity is enhanced by high temperatures, and
the greatest phytotoxicity in inhibiting both germination and seedling development is attained with high temperatures and
long photoperiods. These results suggest that the environmental factors temperature and photoperiod may alter the allelopathic
effect of Cistus ladanifer.
Received 5 December 2001; accepted 11 March 2002. 相似文献
966.
A laboratory technique for investigation of diffusion and transformation of volatile organic compounds in low permeability media 总被引:1,自引:0,他引:1
Gordon S Mackay D Górecki T Cherry JA Pawliszyn J 《Journal of contaminant hydrology》2002,57(3-4):223-240
A laboratory diffusion cell technique that permits spatial and temporal estimates of porewater concentrations over short intervals suitable for estimation of effective diffusion coefficients (De) and degradation rate constants (k) of volatile organic compounds (VOCs) in saturated low permeability media is presented. The diffusion cell is a sealed cylinder containing vapour reservoirs for sampling, including a vapour reservoir source and an array of vapour-filled "mini-boreholes", which are maintained water- and sediment-free by slightly negative porewater pressures. The vapour reservoirs were sampled by Solid Phase Micro-Extraction (SPME), resulting in minimal disturbance to the experimental system. Porewater concentrations are estimated from the measured vapour concentrations. Experiments were conducted using a non-reactive medium and five VOCs with a range in partitioning properties. Calibration experiments showed that equilibrium partition coefficients could be used for calculating concentrations in the vapour reservoir source from concentrations in the SPME coating after a 1-min microextraction and that the reservoir concentration was insignificantly affected by sampling. However, equilibrium was not reached during the one-min extraction of the boreholes; the microextraction reduced the borehole vapour concentrations, leading to diffusion of VOCs from porewater into the vapour-filled borehole. Thus, empirical partitioning coefficients were required for the determination of porewater VOC concentrations. The experimental data and numerical modelling indicate masses extracted by SPME extraction are relatively small, with minimal perturbation on processes studied in diffusion experiments. This technique shows promise for laboratory investigation of diffusion and transformation processes in low permeability media. 相似文献
967.
Study on PCBs,PCDD/Fs,organochlorine pesticides,heavy metals and arsenic content in freshwater fish species from the River Turia (Spain) 总被引:6,自引:0,他引:6
In this study samples of common trout, European eel and barbel have been analysed for the levels of heavy metals such as lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu), and the metalloid arsenic (As). Polychlorinated biphenyls (PCBs), including three non-ortho substituted PCBs, 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and DDT and its two main metabolites were also analysed in some selected samples, in order to evaluate the extent of contamination of the River Turia basin. All samples presented detectable levels of the elements analysed, presenting zinc the highest concentrations. European eel was the species found to highly accumulate these contaminants. Regarding organochlorinated compounds, seven samples exhibited detectable levels of the most toxic PCDD/Fs congener, the 2,3,7,8-TCDD. Non-ortho PCBs were not detected or not quantified in almost all samples and the sum of the individual PCB congeners determined were low compared to other aquatic ecosystems with similar fish species. 相似文献
968.
A home-modified atomic fluorescence detector (mAFS) has been employed for mercury and methylmercury determination in bivalves from the Andalusian coast (south Spain). This modification consists on the inclusion of a quartz flow cell into the detector, which increases the concentration of mercury atoms in the detector and therefore enhances sensitivity about two fold. Two analytical approaches for mercury speciation based on the coupling of gas chromatography on-line pyrolysis and mAFS (GC-Pyro-mAFS) have been tested. The first approach (Method 1) is based on aqueous ethylation followed by extraction into an organic solvent, and the second one (Method 2) in the extraction of monoalkylated mercury as chloride. Method 1 is a rapid procedure but not sensitive enough for the analysis of methylmercury in non-polluted sites (detection limit: 20 ng g(-1) as mercury, wet basis). The second one is quite more sensitive (detection limit: 0.2 ng g(-1), wet weight), but sample treatment is cumbersome and time-consuming. The optimum range for mercury determination for both methods are complementary and exhibit an overlapping measurable concentration range (OMCR) in which methylmercury can be indistinctly determined (75-100 ng g(-1) as mercury, wet basis). The suitability of both methods has been assayed with spiking experiences at levels within the OMCR with good recoveries. Both approaches have been validated with two certified reference materials (BCR-463, mercury and methylmercury in tuna fish; and NIST-2977, organic contaminants and trace metals in mussel tissue). Both procedures have been used for the analysis of three species of bivalve molluscs collected along the Andalusian coast (south Spain), all of them employed for human consumption (Chamelea gallina, Donax trunculus and Scrobicularia plana), and their potential use in routine analysis has been established. 相似文献
969.
Experimental design of Fenton and photo-Fenton reactions for the treatment of cellulose bleaching effluents 总被引:1,自引:0,他引:1
Multivariate experimental design was applied to the treatment of a cellulose conventional bleaching effluent in order to evaluate the use of the Fenton reagent under solar light irradiation. The effluent was characterised by the general parameters total organic carbon (TOC), chemical oxygen demand and color, and it was analysed for chlorinated low molecular weight compounds using GC–MS. The main parameters that govern the complex reactive system: Fe(II) and H2O2 initial concentration, and temperature were simultaneously studied. Factorial experimental design allowed to assign the weight of each variable in the TOC removal after 15 min of reaction. Temperature had an important effect in the organic matter degradation, especially when the ratio of Fenton reagents was not properly chosen. Fenton reagent under solar irradiation proved to be highly effective for these types of wastewaters. A 90% TOC reduction was achieved in only 15 min of treatment. In addition, the GC–MS analysis showed the elimination of the chlorinated organic compounds initially detected in the studied bleaching effluents. 相似文献
970.
Degradation of some biorecalcitrant pesticides by homogeneous and heterogeneous photocatalytic ozonation 总被引:12,自引:0,他引:12
Photo-Fenton/ozone (PhFO) and TiO2-photocatalysis/ozone (PhCO) coupled systems are used as advanced oxidation processes for the degradation of the following biorecalcitrant pesticides: alachlor, atrazine, chlorfenvinfos, diuron, isoproturon and pentachlorophenol. These organic compounds are considered Priority Hazardous Substances by the Water Framework Directive of the European Commission. The degradation process of the different pesticides, that occurs through oxidation of the organic molecules by means of their reaction with generated OH radical, follows a first and zero-order kinetics, when PhFO and PhCO are applied, respectively. These two Advanced Oxidation Processes, together with the traditional ozone+UV, have been used to investigate TOC reduction of the different pesticide aqueous solutions. The best results of pesticide mineralization are obtained when PhFO is applied; with the use of this advanced oxidation process the aqueous pesticide solutions become detoxyfied except in the case of atrazine and alachlor aqueous solutions for which no detoxification is achieved at the experimental conditions used in the work, at least after 2 and 3 h of treatment, respectively. 相似文献