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611.
William D. Brown 《Behavioral ecology and sociobiology》2011,65(5):1007-1014
Male tree crickets, Oecanthus nigricornis, offer a nuptial gift to females during mating in the form of a secretion from a dorsal metanotal gland. I examined the effects of male and female nutrient limitation on allocation of the gift. Males were fed 14C radiolabeled amino acids, placed onto high- or low-quality diets and then mated with females also maintained on high- or low-quality diets. Female acquisition of radiolabel increased, and residual radiolabel within the metanotal gland decreased, over time verifying that gift size correlates with duration of courtship feeding. High-diet females produced greater egg numbers and allocated proportionally more of the male-derived amino acids to their ovaries. As predicted, duration of courtship feeding was greater for males on high-quality diets and females on low-quality diets. Amino acid transfer, measured as the proportion of total radiolabel transferred to the female, showed a significant interaction between male and female diet. High-diet females acquired available radiolabel more rapidly from high-diet males, but low-diet females acquired available radiolabel more rapidly from low-diet males. The causes of these differences between feeding duration and nutrient allocation are discussed. 相似文献
612.
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614.
We report the detection of a mosaic triple trisomy, 46, XY/49, XY, + 13, +20, +21, in two amniotic fluid specimens obtained from a pregnancy that yielded a normal infant. Traditional cytogenetic methods failed to detect the abnormal cell lineage in fetal blood, foreskin, amnion, umbilical cord, and three different biopsies of the chorion. In addition, fluorescence in situ hybridization study of cells from a buccal smear showed no evidence of cells with three copies of chromosome 20. 相似文献
615.
Summary American Acraeinae butterflies often ingest large amounts of dehydropyrrolizidine alkaloids (PAs) from their Asteraceae hostplants in both larval and adult stages, but do not normally store these compounds for defence, instead biosynthesizing large amounts of the cyanogenic glucoside linamarin in all stages. This defence syndrome (rejection of plant toxins andde novo synthesis of protective chemicals) is considered to be the most evolved among aposematic (unpalatable mimicry-model) butterflies, as are the Acraeinae and Heliconiini which also synthesize cyanogens. Storage or minimal processing of larval hostplant-derived defensive chemicals is widespread and characterizes the most primitive model groups; an intermediate series (Danainae/Ithomiinae) also obtains the principal defensive chemicals (PAs) from plants, but mostly in the adult stage. These syndromes are discussed and contrasted with the pattern seen in Chrysomelidae beetles, wherede novo synthesis is widespread and considered primitive.Originally presented at the 9th Meeting on Micromolecular Evolution, Systematics and Ecology (Ribeirão Preto, SP, April 1987); see also Brownet al. (1990) 相似文献
616.
Kevin C. Weng Andre M. Boustany Peter Pyle Scot D. Anderson Adam Brown Barbara A. Block 《Marine Biology》2007,152(4):877-894
Satellite telemetry studies of 20 adult and sub-adult white sharks (360–530 cm estimated total length (TL)) in the eastern
North Pacific during 1999–2005 revealed long distance seasonal migrations from the coast of California to an offshore focal
area 2,500 km west of the Baja Peninsula, as well as the Hawaii Islands. Three tags were recovered allowing detailed behavioral
analyses, including one shark’s migration cycle from the coast to the offshore focal area and back. While near pinniped rookeries
in autumn and winter, sharks avoided the surface and used water to 50 m depth, consistent with a silhouette-based hunting
strategy. Offshore migrations were initiated during November–March and followed periods of decreasing pinniped abundance.
Migrations were highly directed, taking 23 ± 5 days to reach the offshore focal area along similar paths among sharks and
years, defining a migration corridor. Sharks exhibited a broad depth distribution (0–644 m) in the offshore focal area, and
remained there for up to 167 days during spring and summer, though primary productivity and fishery data suggest that forage
resources are scarcer there than in other regions of the eastern North Pacific. Archival data from one shark revealed intensive
oscillatory movements while in the offshore focal area, a behavior that may be related to foraging or mating. Sharks traveling
to Hawaii remained near the islands up to 122 days, potentially feeding on pelagic fishes and marine mammals that concentrate
around the islands.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
617.
Growth experiments in batch cultures indicated that the uptake of nitrate by the marine pseudomonad PL1 was inhibited in the presence of ammonia provided that the ammonia concentration was higher than 1 mM. At ammonia concentrations of less than about 1 mM, however, both nitrate and ammonia were utilised simultaneously. The saturation constants for nitrate and ammonia uptake were both 2.6x10-4 M, and similar to the Michaelis constants of nitrate reductase for nitrate (2.9x10-4 M) and glutamine synthetase for ammonia (2x10-4 M). Nitrate reductase activity linked to NADH was detected in chemostat-grown cultures with nitrate as nitrogen source, and in cultures containing limiting concentrations of nitrate and ammonia, ammonia or glutamate. Enzyme synthesis appeared to be repressed in cultures containing an excess of ammonia or glutamate. Chemostat cultures utilised ammonia or glutamate in preference to nitrate, while there was no marked preference between ammonia and glutamate. 相似文献
618.
The haploid state of males in eusocial Hymenoptera—the ants, bees, and wasps—has been proposed as a driving force in the evolution of social behavior under the assumption that haploidy results in higher susceptibility to pathogens. In this study, we present the first test of the assumptions of the “haploid male susceptibility hypothesis”. We challenged males and workers of the bumblebee Bombus terrestris with its parasite Crithidia bombi but found no differences in either initial susceptibility or the intensity of infection between haploid males and diploid females. We reviewed observational studies on parasitism in haplodiploid insects and found that in 15 out of 26 cases, haploid males had lower parasite prevalence. However, the majority of available data related to nontransmissible parasites and thus any general statements about haploid susceptibility remain unclear. Using a simulation model, we studied how diverse genetic mechanisms could affect the values for resistance; results suggest that only a phenomenon that renders workers effectively haploid, e.g., imprinting, could explain our experimental results. A more likely explanation is that, in eusocial Hymenoptera with predominantly female populations, parasites may simply become more adapted to the more common female hosts and, thus, male haploid susceptibility may be hidden due to parasite adaptation. Our results do not support the idea that the haploid susceptibility hypothesis explains the origin or maintenance of social systems in the eusocial Hymenoptera. 相似文献
619.
Summary As recognized by Miriam Rothschild as early as the 1960s and repeatedly emphasized in her papers, the use, misuse, or non-use of plant allelochemicals by insects is extremely variable and difficult to predict, at many levels of time, space, and biological organization. Although certain patterns that reoccur have been important in the development of ecological theory, the optimization of cost-benefit equations involving two or three trophic levels, each with large numbers of individuals, populations, and species in erratic and complex interactions, produces unexpected and fascinating scenarios. The development of rapid colorimetric and chromatographic analyses for several types of plant allelochemicals, notably certain groups of alkaloids, cardiac and cyanogenic glycosides, phenolics, terpenes, and glucosinolates, has permitted a detailed investigation of the variation and flow of these substances in natural organisms and ecosystems. The results of these analyses, in our hands mostly for pyrrolizidine alkaloids (PAs), do not suggest a straightforward classical choice by the aposematic insect to simply sequester or synthesize its defences. Rather, they reveal a confusing variety of diffuse and complex patterns that become increasingly closer to chaos as they are multiplied across structures, species, sexes, stages, sites, seasons, and selective regimes. We present a model reflecting results of analyses at this chemoecological interface. Depending upon an initial option, involving the recognition (or not) of a plant allelochemical, the herbivore will face thereafter options to ingest it (or not), and then to tolerate and absorb (or detoxify and excrete), modify (or not), passively, actively or selectively accumulate, turn over (or not), distribute (or concentrate), and use this compound in a variety of growth, defense, or reproductive functions. The herbivore can also quantitatively or qualitatively regulate the intensity or dispersion of its attack on the plant tissues, in order to modify feedback loops of selection on the plant and its chemicals which exist in most of the earlier steps, or those with its predators and parasites that occur in the later ones. Options that lead to mutualism through positive feedback loops will tend to accumulate and become rapidly fixed by natural selection. Additional variations and anomalies such as automimicry, chemical mimicry, sexual dimorphism and communication, selective sequestration and passing-up of allelochemicals, special glands and structures, and synergism effects, are among the secondary complications of this model that have occupied much thought, time, experimental labor, and polemical space in chemical ecology journals and meetings. Examination of the tendencies and results at various points in the model can be used to explain these features and to make further predictions, plan experiments, and devise activity-based bioassays and new chemical analyses. These may lead some day to new and more robust visions of the major patterns of chemical transfer at this widespread and important natural interface. 相似文献
620.
Using Montane Mammals to Model Extinctions Due to Global Change 总被引:2,自引:0,他引:2
We use data on the species-area relationship and the nested subset structure of the boreal mammal faunas inhabiting isolated mountaintops in the Great Basin to develop a simple quantitative model that predicts the number and identity of species that would go extinct under an assumed scenario of changing climate and vegetation. Global warming of 3°C is predicted to cause the loss of 9–62% of the species inhabiting each mountain range and the extinction of three of fourteen species throughout the region. These results suggest (1) that it is possible to make highly plausible predictions about the susceptibility of species to extinction without detailed information about their population biology, and (2) that global and regional environmental changes seriously threaten the survival of species that are restricted in distribution to both natural "habitat islands" and biological reserves. 相似文献