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391.
Summary In many insects nutrients transferred by the male at mating are later incorporated into both the eggs and soma of the mated females. Accordingly, it has been suggested that insect females can use these male-derived nutrients for somatic maintenance and enhancement of their fecundity and fitness of their offspring. I this paper we tested the validity of these predictions by studying the longevity and reproductive output of 1, 2, 3, 4 or 5 times mated female monarchs Danaus plexippus, a nectar-feeding butterfly that is long-lived and strongly polyandrous and emerges as an adult without mature eggs. Females mated five times received ejaculates that corresponded to an average of 38% of their body weight at eclosion. However, we found that the number of times females had mated had no effect on their longevity, life-time fecundity, or egg weight. Although negative evidence should always be interpreted with caution, our study suggests that male-derived nutrients are less important for female longevity and reproductive output than are larval and adult food. 相似文献
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R. Väinölä 《Marine Biology》1992,114(4):539-550
Inter-and intraspecific allozyme differentiation in the mysid crustacean genus Mysis in the North Atlantic region was studied in order to evaluate earlier concepts of evolutionary and systematic relationships and to assess patterns of subdivision within widespread taxa. The results support a relatively ancient divergence of the marine and non-marine species of the genus, and are generally in line with the current subgeneric tridivision into Mysis s.str., Michteimysis and Auricomysis. However, the North American littoral species M. gaspensis should be returned to subgenus Mysis s.str. from its present position in Michteimysis with M. mixta. The closest observed affinities within Mysis s.str. were between M. gaspensis and the freshwater M. relicta group, and between M. oculata and M. litoralis. Intraspecific differentiation among North European coastal populations of M. oculata and M. litoralis was moderately strong (F
ST0.1), suggesting population bottlenecks and limited dispersal in the post-glacial time. On the other hand, ransoceanic differences were not essentially greater, indicating the systematic homogeneity and long-term dispersal capacity in the marine species. This contrasts with the strong genetic and systematic fragmentation earlier found within the circumboreal M. relicta species group. 相似文献
394.
The aim of this study was to evaluate the suitability of in vitro enzymatic methods for assaying the biodegradability of new starch-based biopolymers. The materials studied included commercial starch-based materials and thermoplastic starch films prepared by extrusion from glycerol and native potato starch, native barley starch, or crosslinked amylomaize starch. Enzymatic hydrolysis was performed using excessBacillus licheniformis -amylase andAspergillus niger glucoamylase at 37°C and 80°C. The degree of degradation was determined by measuring the dissolved carbohydrates and the weight loss of the samples. Biodegradation was also determined by incubating the samples in a compost environment and measuring the weight loss after composting. The results indicated that the enzymatic method is a rapid means of obtaining preliminary information about the biodegradability of starch-based materials. Other methods are needed to investigate more accurately the extent of biodegradability, especially in the case of complex materials in which starch is blended with other polymers. 相似文献
395.
Hautala EL Rekilä R Tarhanen J Ruuskanen J 《Environmental pollution (Barking, Essex : 1987)》1995,87(1):45-49
A vertical snow-sampling method, where a sample was taken throughout the snowpack, was used to estimate the pollutant load on a roadside where average daily traffic density was about 9100 motor vehicles. The snow samples were collected at two sites, forest and open field, at two distances of 10 and 30 m from the road. The concentrations of inorganic anions (Cl(-), NO(-)(3), SO(2-)(4)), total N, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated phenols (PCPhs) were analysed. The results suggest that on roadsides there is a deposition caused by road traffic emissions and winter maintenance which exceeds normal background deposition. Inorganic anions mainly in particle form, originating from winter maintenance, are deposited near the road. PAHs with low molecular weight (=252) are mainly in gaseous form and are deposited further away from the road. Also, some PCPhs show similar behaviour. The dispersion is different at the forest site than at the open-field site. Our results also indicate that the vertical snow-sampling method can be used in studying pollutant load from traffic near the roads. However, studies should focus on individual PAH or PCPh compounds as markers of highway pollution. The deposition of mixtures of compounds does not bring sufficient information in the light of present knowledge. 相似文献
396.
Manninen S Huttunen S Rautio P Perämäki P 《Environmental pollution (Barking, Essex : 1987)》1996,93(1):27-38
A field survey was performed in eastern Finland, where measured ambient SO2 concentrations were 1.4-3.8 microg m(-3) a(-1) and bulk S deposition 0.17-0.32 g m(-2) a(-1) in 1991-1993. The accumulation of sulphur (S) in needles of Scots pine (Pinus sylvestris L.) was studied with XRF, IC and FESEM analyses and the needle damage examined under a light microscope and by SEM. Foliar N concentrations were also measured. Foliar total S concentrations were observed to be above the normal S level (500-700 microg g(-1)) over almost the whole area. Slight chlorosis and/or necrosis of the needle tips and stomatal areas, changes in the needle surface waxes and localization of S into needle tips and mesophyll cells around the stomata suggested the impact of S deposition, as did the calculations of St/Nt, and 'predicted' and 'excess' S. A concentration of about 900 microg g(-1) may be considered a critical level for foliar St in areas with low N supply. 相似文献
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