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Sexual dimorphism in body size (sexual size dimorphism) is common in many species. The sources of selection that generate the independent evolution of adult male and female size have been investigated extensively by evolutionary biologists, but how and when females and males grow apart during ontogeny is poorly understood. Here we use the hawkmoth, Manduca sexta, to examine when sexual size dimorphism arises by measuring body mass every day during development. We further investigated whether environmental variables influence the ontogeny of sexual size dimorphism by raising moths on three different diet qualities (poor, medium and high). We found that size dimorphism arose during early larval development on the highest quality food treatment but it arose late in larval development when raised on the medium quality food. This female-biased dimorphism (females larger) increased substantially from the pupal-to-adult stage in both treatments, a pattern that appears to be common in Lepidopterans. Although dimorphism appeared in a few stages when individuals were raised on the poorest quality diet, it did not persist such that male and female adults were the same size. This demonstrates that the environmental conditions that insects are raised in can affect the growth trajectories of males and females differently and thus when dimorphism arises or disappears during development. We conclude that the development of sexual size dimorphism in M. sexta occurs during larval development and continues to accumulate during the pupal/adult stages, and that environmental variables such as diet quality can influence patterns of dimorphism in adults. 相似文献
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Mitochondrial volume fraction was compared among three regions along the length of six multiply innervated fibers (MIFs) in the orbital surface layer of rabbit superior rectus. These MIFs are of about 5 μm diameter toward the middle of their length, and of about 15 μm diameter toward their proximal and distal ends. The region of highest volume fraction (26%) was located toward the proximal end of their segment of minimal diameter, in apparent association with endplate-like nerve junctions. The region of lowest volume fraction (8%) was located at their distal segment of maximal diameter. The region toward the distal end of their segment of minimal diameter displayed an intermediate volume fraction (15%). These mitochondrial volume fractions were further analyzed in terms of the relative contributions of the I-band, the A-band, and the subsarcolemmal mitochondrial clusters. Comparable changes in mitochondrial content occur in both the I-band and A-band: in the fibers' distal segment of maximal diameter, however, the mitochondrial volume fraction in the A-band (5%) is lower than in the I-band (11%). These modifications of mitochondrial content along the fibers' length occur irrespective of the contributions of the subsarcolemmal mitochondrial clusters. 相似文献
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The physiological basis of reaction norms: the interaction among growth rate, the duration of growth and body size 总被引:4,自引:1,他引:3
The general effects of temperature and nutritional quality ongrowth rate and body size are well known. We know little, however,about the physiological mechanisms by which an organism translatesvariation in diet and temperature into reaction norms of bodysize or development time. We outline an endocrine-based physiologicalmechanism that helps explain how this translation occurs inthe holometabolous insect Manduca sexta (Sphingidae). Body sizeand development time are controlled by three factors: (i) growthrate, (ii) the timing of the cessation of juvenile hormone secretion(measured by the critical weight) and (iii) the timing of ecdysteroidsecretion leading to pupation (the interval to cessation ofgrowth [ICG] after reaching the critical weight). Thermal reactionnorms of body size and development time are a function of howthese three factors interact with temperature. Body size issmaller at higher temperatures, because the higher growth ratedecreases the ICG, thereby reducing the amount of mass thatcan accumulate. Development time is shorter at higher temperaturesbecause the higher growth rate decreases the time required toattain the critical weight and, independently, controls theduration of the ICG. Life history evolution along altitudinal,latitudinal and seasonal gradients may occur through differentialselection on growth rate and the duration of the two independentlycontrolled determinants of the growth period. 相似文献
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Rinberg D. Davidowitz H. 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2003,189(12):867-876
Experiments on the cercal wind-sensing system of the American cockroach, Periplaneta americana, showed that the firing rate of the interneurons coding wind information depends on the bandwidth of random noise wind stimuli. The firing rate was shown to increase with decreases in the stimulus bandwidth, and be independent of changes in the total power of the stimulus with constant spectral composition. A detailed analysis of ethologically relevant stimulus parameters is presented. A phenomenological model of these relationships and their relevance to wind-mediated cockroach behavior is proposed.Abbreviations 2D
two dimensional
- FOWD
fiber-optic wind detector
- GI
giant interneurons
- STA
spike-triggered average 相似文献
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G Davidowitz HF Nijhout DA Roff 《Evolution; international journal of organic evolution》2012,66(9):2916-2928
A great deal is known about the evolutionary significance of body size and development time. They are determined by the nonlinear interaction of three physiological traits: two hormonal events and growth rate (GR). In this study we investigate how the genetic architecture of the underlying three physiological traits affects the simultaneous response to selection on the two life-history traits in the hawkmoth Manduca sexta. The genetic architecture suggests that when the two life-history traits are both selected in the same direction (to increase or decrease) the response to selection is primarily determined by the hormonal mechanism. When the life-history traits are selected in opposite directions (one to increase and one to decrease) the response to selection is primarily determined by factors that affect the GR. To determine how the physiological traits affect the response to selection of the life-history traits, we simulated the predicted response to 10 generations of selection. A total of 83% of our predictions were supported by the simulation. The main components of this physiological framework also exist in unicellular organisms, vertebrates, and plants and can thus provide a robust framework for understanding how underlying physiology can determine the simultaneous evolution of life-history traits. 相似文献
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H. Frederik Nijhout Derek A. Roff Goggy Davidowitz 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1540):567-575
Body size and development time of Manduca sexta are both determined by the same set of three developmental–physiological factors. These define a parameter space within which it is possible to analyse and explain how phenotypic change is associated with changes in the underlying factors. Body size and development time are determined by the identical set of underlying factors, so they are not independent, but because the mechanisms by which these factors produce each phenotype are different, the two phenotypes are only weakly correlated, and the correlation is context dependent. We use a mathematical model of this mechanism to explore the association between body size and development time and show that the correlation between these two life-history traits can be positive, zero or negative, depending entirely on where in parameter space a population is located, and on which of the underlying factors has a greater variation. The gradient within this parameter space predicts the unconstrained evolutionary trajectory under directional selection on each trait. Calculations of the gradients for body size and development time revealed that these are nearly orthogonal through much of the parameter space. Therefore, simultaneous directional selection on body size and development time can be neither synergistic nor antagonistic but leads to conflicting selection on the underlying developmental parameters. 相似文献
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Wlodek Mandecki Barbara Ardelt Thomas Coradetti Hanan Davidowitz James A AFlint Zhili Huang Wesley M MKopacka Xin Lin Zhuying Wang Zbigniew Darzynkiewicz 《Cytometry. Part A》2006,69(11):1097-1105
BACKGROUND: An electronic radio frequency (RF) microchip, the microtransponder (MTP), has been developed as a platform for assays in the fields of genomics and proteomics. Upon activation by light, each MTP provides a unique RF identification (ID) signal that matches a chip to the specific biological material attached to it. The MTP is powered by a photocell and has an antenna that transmits the signal. The aim of the present study was to explore utility of MTPs as a platform for cell growth in cytotoxicity assays. METHODS: The MCF-7, MCF-116, A549, or T-24 cells growing on MTPs placed in petri dishes or slide chambers were cultured untreated or exposed to antitumor drugs topotecan, mitoxantrone, or onconase for up to 4 days. Their attachment to- and growth on- MTPs was assessed by fluorescence microscopy and laser scanning cytometry (LSC) and compared with growth on the dish surface in the MTP neighborhood. The MTPs were fixed in ethanol, stained with propidium iodide (PI), and interrogated in flow in the instrument capable to rapidly (up to 103 MTPs/s) identify their ID signal and measure fluorescence. RESULTS: The cells plated on MTPs exhibited similar attachment properties to those plated in culture dishes. When measured by LSC, they had similar mitotic activity, growth rate, and cell cycle distributions as the cells adhering to the culture dish in the neighborhood of MTPs. The fluorescence intensity of MTPs provided information about the cell number per MTP, which made it possible to assess cell growth rate and monitor the cytostatic/cytotoxic effects of the tested drugs. CONCLUSIONS: The MTP-based system holds promise for the multiplexed cell assays in which numerous different cell lines can be screened for their growth rate or sensitivity while exposed to particular agents in the same vessel. Other advantages of the system are the rapidity of the screening and a very large number of ID codes. Because many cell lines/types can be assayed in a single dish, the system also offers cost savings on tissue culture reagents. 相似文献