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91.
93.
94.
Martin?HeilEmail author Birgit?Baumann Ralf?Krüger K. Eduard?Linsenmair 《Chemoecology》2004,14(1):45-52
Summary. Myrmecophytic plants use obligate ant mutualists as a constitutive
indirect defence mechanism. These plants often produce cellular food bodies (FBs) to
nourish their resident ants. Lipids, proteins, and even highly specialised compounds
such as glycogen have been reported from FBs, but detailed chemical analyses of FB
composition have so far been presented only for Southeast Asian Macaranga
and Central American Piper myrmecophytes. Here we
report the chemical composition of FBs of five myrmecophytic Acacia
(Fabaceae) species from Mexico using HPLC (carbohydrates and proteins) and GC-MS
(lipids). Feeding experiments revealed no hints on any use of external food sources
by the inhabiting Pseudomyrmex ants. These ants
obviously rely completely on FBs and extrafloral nectar provided by their hosts.
The total content of nutrients in Acacia FBs was 15-25% of FB
dry mass, being much lower than in Macaranga or
Piper FBs. Proteins were dominating (8-14 % dm)
in Acacia FBs and thus were present in higher amounts than in
Macaranga FBs, yet in lower amounts than in
Piper. Lipids contributed 1-9 %
of dry mass, showing a lower proportion than in FBs of Macaranga
or Piper. Carbohydrates made up 3-11 % dm, reaching
in most Acacia species the same range as observed in
Macaranga and in Piper FBs.
Water content was 18-24 % of FB fresh mass, and structural tissue obviously made up
a much higher proportion in Acacia FBs than in
Macaranga or Piper
FBs. Both characters might represent an adaptation to producing FBs unprotected at
the leaf tips under dry conditions. Acacia FBs
contain all amino acids and all fatty acids that are considered essential for
insects, and their contents of lipids and proteins are higher than in the leaves
from which they are ontogenetically derived. This indicates a putatively adaptive
enrichment of nutritionally valuable compounds in structures functioning as ant-food. 相似文献
95.
Research on group living in animals is concentrated on highly social species, but studying less social species may hint at the factors possibly leading to the evolution of increased sociality. Thermoregulation is often thought to explain communal nesting in solitarily breeding mammals but also other factors may be involved. For example, it is observed that even solitary species may have cryptic kin cooperation. We studied factors affecting communal nesting in the Siberian flying squirrel. Flying squirrels breed solitarily but, similar to most other rodents, adults may sometimes huddle in groups. Communal nesting in flying squirrels was most frequent during winter and autumn, but also occurred during other seasons. This pattern was explained by the breeding season, which took place in the spring–summer, when communal nesting was less common. Neither monthly temperature, after accounting for breeding season, nor daily temperatures in winter explained communal nesting. Group size was small, two to three individuals. In most cases the group was a pair consisting of unrelated male and female, possibly indicating that group formation was related to mating behavior. This study contributes to the understanding of mammalian group formation in two major ways. First, our study contributes to the understanding of the role of relatedness in rodent group formation, demonstrating a case where close relatedness is not related to group formation. Second, our study indicates that in a solitarily breeding, rodent huddling may be more driven by other factors than temperature. 相似文献
96.
Ralf M. Staebler Sean M. McGinn Brian P. Crenna Thomas K. Flesch Katherine L. Hayden Shao-Meng Li 《Atmospheric environment (Oxford, England : 1994)》2009,43(38):6091-6099
In Canada approximately 45% of ammonia (NH3) emissions are attributed to dairy and beef cattle industries. The present study focused on NH3 emissions from a beef feedlot with a one-time capacity of 17,220 head. The aim was to improve the Canadian NH3 emission inventories and air quality forecasting capabilities. A Cessna 207, equipped with a fast-response NH3/NOy detector and a quadrupole aerosol mass spectrometer, was flown in a grid pattern covering an area of 8 × 8 km centered on a feedlot (800 × 800 m) at altitudes ranging from 30 to 300 m above ground. Stationary ground measurements of NH3 concentration and turbulence parameters were made downwind of the feedlot. Three flights were conducted under varying meteorological conditions, ranging from very calm to windy with near-neutral stratification. NH3 mixing ratios up to 100 ppbv were recorded on the calm day, up to 300 m above ground. An average feedlot NH3 emission rate of 76 ± 4 μg m?2 s?1 (equivalent to 10.2 g head?1 h?1) was estimated. Characteristics of the measured NH3 plume were compared to those predicted by a Lagrangian dispersion model. The spatially integrated pattern of NH3 concentrations predicted and measured agreed but the measured was often more complex than the predicted spatial distribution. The study suggests that the export of NH3 through advection accounted for about 90% of the emissions from the feedlot, chemical transformation was insignificant, and dry deposition accounted for the remaining 10%. 相似文献
97.
Christophe Walgraeve Kristof Demeestere Jo Dewulf Ralf Zimmermann Herman Van Langenhove 《Atmospheric environment (Oxford, England : 1994)》2010,44(15):1831-1846
Particulate matter (PM) has become a major research issue receiving increasing attention because of its significant negative impact on human health. There are main indicators that next to the morphological characteristics of the particle, also the chemical composition plays an important role in the adverse health effects of PM. In this context, the rather polar organic fraction of PM is expected to play a major role, and advanced analytical techniques are developed to improve the knowledge on the molecular composition of this fraction. One component class that deserves major attention consists of the oxygenated polycyclic aromatic hydrocarbons (PAHs). Those compounds are considered to be among the key compounds in PM toxicity. This paper presents a comprehensive review focusing on the analysis, fate and behavior of oxygenated PAHs in the atmosphere. The first part of the paper briefly introduces (i) the main sources and atmospheric pathways of oxygenated PAHs, (ii) available physical–chemical properties and (iii) their health effects. The second and main part of this paper gives a thorough discussion on the entire analytical sequence necessary to identify and quantify oxygenated PAHs on atmospheric PM. Special attention is given to critical parameters and innovations related to (i) sampling, (ii) sample preparation including both extraction and clean-up, and (iii) separation and detection. Third, the state-of-the-art knowledge about the atmospheric occurrence of oxygenated PAHs is discussed, including an extended overview of reported concentrations presented as a function of sampling season and geographical location. A clear seasonal effect is observed with the median of the oxygenated PAHs concentrations during winter being a factor of 3–4 higher than during summer. However, the oxygenated PAH/parent PAH ratio is about 20 times higher during summer, indicating the importance of photochemical activity in the atmosphere. 相似文献
98.
99.
Ramzaev V Yonehara H Hille R Barkovsky A Mishine A Sahoo SK Kurotaki K Uchiyama M 《Journal of environmental radioactivity》2006,85(2-3):205-227
In order to estimate current external gamma doses to the population of the Russian territories contaminated as a result of the Chernobyl accident, absorbed gamma-dose rates in air (DR) were determined at typical urban and suburban locations. The study was performed in the western districts of the Bryansk Region within the areas of 30 settlements (28 villages and 2 towns) with the initial levels of 137Cs deposition ranging from 13 to 4340 kBqm(-2). In the towns, the living areas considered were private one-story wooden and stone houses. DR values were derived from in situ measurements performed with the help of gamma-dosimeters and gamma-spectrometers as well as from the results of soil samples analysis. In the areas under study, the values of DR from terrestrial radionuclides were 25+/-6, 24+/-5, 50+/-10, 32+/-6, 54+/-11, 24+/-8, 20+/-6, 25+/-8, and 18+/-5 nGyh(-1) at locations of kitchen gardens, dirt surfaces, asphalt surfaces, wooden houses, stone houses, grasslands inside settlement, grasslands outside settlement, ploughed fields, and forests, respectively. In 1996-2001, mean normalized (per MBqm(-2) of 137Cs current inventory in soil) values of DR from (137)Cs were 0.41+/-0.07, 0.26+/-0.13, 0.15+/-0.07, 0.10+/-0.05, 0.05+/-0.04, 0.48+/-0.12, 1.04+/-0.22, 0.37+/-0.07, and 1.15+/-0.19 microGyh(-1) at the locations of kitchen gardens, dirt surfaces, asphalt surfaces, wooden houses, stone houses, grasslands inside settlement, grasslands outside settlement, ploughed fields, and forests, respectively. The radiometric data from this work and the values of occupancy factors determined for the Russian population by others were used for the assessments of annual effective doses to three selected groups of rural population. The normalized (per MBqm(-2) 137Cs current ground deposition) external effective doses to adults from 137Cs ranged from 0.66 to 2.27 mSvy(-1) in the years 1996-2001, in accordance with professional activities and structures of living areas. For the areas under study, the average external effective doses from 137Cs were estimated to be in the range of 0.39-1.34 mSvy(-1) in 2001. The average external effective doses from natural radionuclides appeared to be lower than those from the Chernobyl fallout ranging from 0.15 to 0.27 mSvy(-1). 相似文献
100.