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1.
KJELL SJÖBERG 《Ibis》1988,130(2):164-171
A total of 126 flightless adult male Teal was caught in 1982 and 1983 in a moulting area in northern Sweden (63° 53'N). The birds were weighed and the stage of development of their primaries and secondaries measured. During the flightless period, the weight of the birds decreased by an average of 10% in 1982 and 19% in 1983. This weight decrease allows the birds to fly before their primaries and secondaries are full-grown. The weight loss is considered to be an adaptation making it possible, for example, for lighter birds to escape predators sooner after moulting. Birds varied greatly in the dates at which they initiated their flightless period, that is, from the end of June to the end of July. Thus, it is probable that both local birds and birds from distant breeding grounds were present in the moulting area. 相似文献
2.
SAMUEL P.S. SVENSSON PER I. ADOLFSSON NILS GRUNDSTR
M JAN OLOF G. KARLSSON 《Pigment cell & melanoma research》1997,10(6):395-400
It has previously been shown that α2-adrenoceptors (α2-ARs) mediate pigment granule (melanosome) aggregation in melanophores of the teleost fish Labrus ossifagus. The present investigation scrutinized the signalling mechanisms of melanosome aggregation induced by sympathetic nerve stimulation or by exogenous addition of α-AR agonists and cAMP analogues. The following was observed: i) nerve-induced melanosome aggregation was associated with a rapid decrease in the cAMP level; ii) noradrenaline or medetomidine (an α2-AR agonist) caused melanosome aggregation and reduced the cAMP content; iii) RP-S-CI-cAMP, a membrane-permeating inhibitor of protein kinase A induced melanosome aggregation; and iv) B-HT 920 (an α2-AR agonist) and methoxamine (an α1-AR agonist) induced melanosome aggregation, although they did not reduce cAMP. It has been suggested that in some teleost species α1-ARs mediate melanosome aggregation by increasing the level of intracellular calcium. However, we found that the effect of methoxamine in melanophores from Labrus ossifagus could be blocked by yohimbine (an α2-AR antagonist) but not by equimolar concentration of prazosin (an α1-AR antagonist). Furthermore, 1 μM ionomycin (a calcium ionophore) did not induce melanosome aggregation. Our findings therefore do not indicate that α1-ARs and/or an increase in intracellular calcium mediate melanosome aggregation in Labrus ossifagus. Our results suggest that α2-AR-mediated melanosome aggregation is induced by multiple signalling pathways. One of these involves a reduction in cAMP, but none involves an increase in intracellular calcium. 相似文献
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4.
NILS HANIK SARA GÓMEZ MICHAEL SCHUELLER COLIN M. ORIANS RICHARD A. FERRIERI 《Plant, cell & environment》2010,33(12):2173-2179
Nitrogen‐13 (t1/2 9.97 m), a radioactive isotope of nitrogen, offers unique opportunities to explore plant nitrogen utilization over short time periods. Here we describe a method for administering 13N as gaseous 13NH3 to intact leaves of Nicotiana tabacum L. (cv Samsun), and measuring the labelled amino acids using radio high‐performance liquid chromatography (HPLC) on tissue extract. We used this method to study the effects of defence induction on plant nitrogen utilization by applying treatments of methyl jasmonate (MeJA), a potent defence elicitor. MeJA caused a significant increase relative to controls in key [13N]amino acids, including serine, glycine and alanine by 4 h post‐treatment, yet had no effect on 13NH3 incorporation, a process that is primarily under the control of the glutamine synthatase/glutamate synthase pathway (GS/GOGAT) in cellular photorespiration. We suggest that the reconfiguration of nitrogen metabolism may reflect induction of non‐photorespiratory sources of nitrogen to better serve the plant's defences. 相似文献
5.
JON E. SWENSON BJØRN DAHLE HELENA BUSK OLE OPSETH THOMAS JOHANSEN ARNE SÖDERBERG KJELL WALLIN GORAN CEDERLUND 《The Journal of wildlife management》2007,71(6):1993-1997
Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km2 and 920/1,000 km2, respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%. 相似文献
6.
Knowledge of statistical power is essential for sampling design and data evaluation when testing for genetic differentiation. Yet, such information is typically missing in studies of conservation and evolutionary genetics, most likely because of complex interactions between the many factors that affect power. powsim is a 32‐bit Windows/DOS simulation‐based computer program that estimates power (and α error) for chi‐square and Fisher's exact tests when evaluating the hypothesis of genetic homogeneity. Optional combinations include the number of samples, sample sizes, number of loci and alleles, allele frequencies, and degree of differentiation (quantified as FST). powsim is available at http://www.zoologi.su.se/~ryman . 相似文献
7.
NILS RYMAN 《Molecular ecology resources》2006,6(1):285-287
chifish is a 32‐bit Windows/DOS program evaluating divergence at multiple gene loci. It tests the hypothesis of no difference at any locus both by means of Pearson's traditional chi‐square and by using Fisher's method of combining P values obtained by Fisher's exact test. Input data are read from a file formatted for genepop . Commonly used population genetics software do not perform chi‐square tests, and the simultaneous application of both techniques aids in situations where poor power of the ‘exact approach’ may prevent detection of true differentiation (e.g. few populations and few alleles per locus). 相似文献
8.
The taxonomy and systematics of the New Caledonian endemic caddisfly genus Gracilipsodes Sykora, 1967 (Trichoptera: Leptoceridae: Grumichellini) are reviewed. Seven new species represented by males are described and illustrated: Gracilipsodes aoupiniensis sp. nov. , Gracilipsodes aureus sp. nov. , Gracilipsodes aurorus sp. nov. , Gracilipsodes grandis sp. nov. , Gracilipsodes koghiensis sp. nov. , Gracilipsodes lanceolatus sp. nov. , and Gracilipsodes robustus sp. nov. Molecular phylogenetic analyses are applied to discern the relationships among the species of the genus and their closest relatives, based on sequence characters from the nuclear gene translation elongation factor-1α (EF-1α) and the three mitochondrial genes cytochrome oxidase I (COI), COII, and ribosomal large subunit (16S). The data are analyzed using parsimony and Bayesian inference, revealing a monophyletic Gracilipsodes with the eastern Australian monotypic genus Triplexa as its closest relative. Gracilipsodes is in turn divided into two major lineages. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 153 , 425–452. 相似文献
9.
ABSTRACT. Gynes and males of Lasius flavus Fab. were taken from the nest as they eclosed, and at intervals thereafter until the mating flight, and their respiration was measured. After the mating flight respiration was measured in gynes at various stages of colony foundation. Respiration in gynes rose rapidly to a peak as they began to accumulate food reserves for colony foundation. Subsequently, the respiratory rate declined and remained at a low level until the mating flight and during the claustral phase of colony foundation. Once the colony was well established and the queen actively laying, the respiratory rate returned to that at the beginning of maturation. Males showed smaller changes in their respiratory rates, which were generally higher than those of the gynes. The variation in respiration in males seemed to be due to increasing restlessness as the time of the mating flight approached. 相似文献
10.