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排序方式: 共有463条查询结果,搜索用时 781 毫秒
431.
The Science of Nature - 相似文献
432.
Gerhard Gries Regine Gries Paul W. Schaefer Tadao Gotoh Yasutomo Higashiura 《Die Naturwissenschaften》1999,86(5):235-238
Pheromone extract of female pink gypsy moth, Lymantria mathura, was analyzed by coupled gas chromatographic-electroantennographic detection (GC-EAD) and coupled GC-mass spectrometry (MS),
employing fused silica columns coated with DB-5, DB-210, or DB-23 and a custom-made GC column that separated enantiomers of
unsaturated epoxides. These analyses revealed (9R,10S)-cis–9,10-epoxy-Z3,Z6-nonadecadiene [termed here (+)-mathuralure] and (9S,10R)-cis–9,10-epoxy-Z3,Z6-nonadecadiene [termed here (–)-mathuralure] at a 1 : 4 ratio as major candidate pheromone components. In field experiments
in northern Japan (Morioka, Iwate Prefecture and Bibai, Hokkaido Prefecture), (+)- and (–)-mathuralure at a ratio of 1 : 4,
but not 1 : 1 or singly, were attractive to male L. mathura. This is the first demonstration that attraction of male moths required the very same ratio of pheromone enantiomers as produced
by conspecific females. Whether L. mathura employ different blend ratios in different geographic areas, and the role of five additional candidate pheromone components
identified in this study remains to be investigated.
Received: 29 October 1998 / Accepted in revised form: 29 December 1998 相似文献
433.
Marina Préault Olivier Chastel Frank Cézilly Bruno Faivre 《Behavioral ecology and sociobiology》2005,58(5):497-505
In monogamous bird species, male parental investment may influence offspring fitness and females may gain advantages through mating with males providing extensive paternal care. However, paternal care is a benefit that can only be assessed indirectly because mate choice precedes paternal activities. Individual quality and age, both signalled by morphological characteristics, may reflect parental abilities. Because they may reflect individual foraging abilities, carotenoid-based colorations have been proposed to honestly signal parental quality. The blackbird (Turdus merula), a socially monogamous species, exhibits biparental care and males show bills that vary from pale yellow to orange due to carotenoid pigments. In this study, we investigated whether male bill colour and age are associated with parental ability. Our results suggest that males with more orange bills and older males are better fathers. Indeed, male visit rate increased with their bill colour index independently of age, and brood condition was higher for adult males, compared to yearlings, independently of bill colour. Overall, the number of fledglings produced was positively influenced by both the age of males and the colour intensity of their bills. Males with more orange bills and adults had a greater number of fledglings and these males also had higher levels of prolactin, a hormone known to promote parental care. This latter finding suggests that prolactin may be the link between carotenoid based colorations and the intensity of paternal effort. Thus, male bill colour seems to honestly reveal male physiological adjustment to paternal activities. 相似文献
434.
Diel oscillations in the photosynthesis-irradiance (P-I) relationship are described for marine phytoplankton assemblages at 6 stations in an upwelling area off the southern California coast (USA) between May and August 1980. The initial slope () and asymptote (P
max) of P-I curves changed significantly over the day; both parameters were in phase and had similar changes in amplitude. The diel oscillations in photosynthesis appeared unrelated to changes in chlorophyll a concentrations. Amplitudes of daily variations in photosynthesis ranged from approximately 3 to 9, as measured by the maximum to minimum ratio for photosynthetic capacity (P
max). Diatom-rich samples collected during an upwelling event and those dominated by dinoflagellates both had midday to early afternoon maxima in and P
max. Samples from other locations had peak photosynthetic activity later in the afternoon. The relationship between and P
max was consistent in all phytoplankton samples analyzed, with a surprisingly high correlation considering the spatial and temporal scales encompassed in this study. These results indicate that the photosynthesis-irradiance (P-I) relationship is time-dependent and, moreover, that changes in and P
max are closely coupled for a variety of natural phytoplankton assemblages. 相似文献
435.
436.
Substrate choice and settlement preferences of planula larvae of five Scyphozoa (Cnidaria) from German Bight,North Sea 总被引:2,自引:0,他引:2
The settlement behaviour of planula larvae and their development to young polyps was investigated in laboratory experiments
in five scyphozoan species [Aurelia aurita (L.), Cyanea capillata (L.), Cyanea lamarckii Péron and Leseur, Chrysaora hysoscella (L.), and Rhizostoma octopus (L.)]. The undersides of settling plates were strongly preferred for settlement. Shells, the only natural substrate type
offered, were less attractive than artificial substrates (concrete, machined wood, polyethylene, and glass). The advantages
of colonization of substrate undersides for survival and reproduction of polyps are discussed. It is supposed that the increase
of artificial substrates in our seas, due to marine litter pollution and submarine building activities, enlarge the areas
of distribution of scyphozoan polyps, in coastal as well as in off-shore regions. Subsequent increases in ephyra production
by polyps are probably one reason for the increase in mass occurrences of jellyfish recognized worldwide during the last few
decades. It is suggested that the early developmental stages in the cnidarian life cycle, the planula larvae, and the polyps,
play the key role in the development of jellyfish outbursts. 相似文献
437.
Elemental composition of surface waters in the Antarctic Peninsula and interactions with the environment 总被引:3,自引:0,他引:3
The fast changes in chemical and biological properties of many coastal and inland waters in the last decades reflect the pressure of man on the environment. The surface waters of the Antarctic Peninsula, located far from industrial or populated areas, could eventually be used as background lines. Surface water samples were taken from five lagoons of King George Island, Antarctic Peninsula, and from the Kitiesh Lake. Sample pH and electrical conductivity were analysed in situ and in the laboratory, respectively. The dissolved fractions were analysed in 1997 and 1998. Total concentrations only for 1998 were determined in another fraction adjusted to pH 2. Aluminium, Ca, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Sr, Cd, Sn, Sb, Ba, Bi, and Pb were quantified in all samples by means of inductively coupled plasma-mass spectrometry (ICP-MS). Total and dissolved elemental concentrations were discussed considering the composition of particulate material suspended in the waters removed by streams or by water runoff, or from atmospheric aerosols. Concentrations of dissolved elements change from one lagoon to another. Total and dissolved elemental concentrations could be related to water movement by windstorms, to chemical mechanisms in water and/or to natural and anthropogenic atmospheric factors. 相似文献
438.
Gerhard Jung 《Die Naturwissenschaften》1927,15(48-49):972-972
439.
440.