Phenotypic plasticity of wing size and shape of Drosophila simulans was analyzed across the entire range of viable developmental temperatures with Procrustes geometric morphometric method. In agreement with previous studies, size clearly decreases when temperature increases. Wing shape variation was decomposed into its allometric (24%) and nonallometric (76%) components, and both were shown to involve landmarks located throughout the entire wing blade. The allometric component basically revealed a progressive, monotonous variation along the temperature. Surprisingly, nonallometric shape changes were highly similar at both extremes of the thermal range, suggesting that stress, rather than temperature per se, is the key developmental factor affecting wing shape. 相似文献
Eight farmed Atlantic bluefin tuna Thunnus thynnus were tagged with temperature and depth transmitters inserted in chub mackerels Scomber colias to characterize their digestive activity, feeding physiology and behaviour in captivity. Results obtained in the experiment can be used to optimize daily T. thynnus feeding strategy in farms, reducing the early regurgitation of food and thus the environmental effects of inappropriate feeding practices. 相似文献
1. Past work on the thermal preferences of Dipsosaurus dorsalis (Biard & Giard) has indicated that intense, exhaustive exercise causes these lizards to select a body temperature (33·5 °C) which is cooler than their preferred activity temperature of 40°C during the first 1–2 h of exercise recovery. 2. In order to test the hypothesis that the thermal regime selected by exhausted D. dorsalis is beneficial to the process of exercise recovery, lizards were forced to undergo both exhaustive and sprinting exercise at their preferred body temperature of 40°C. The peak speeds attained and the total distances travelled by these animals during these two different exercise protocols were measured and the animals were then forced to undergo a second bout of either sprinting or exhaustive exercise, following a 30–330 min recovery at either 20°C, 40°C or under a variable thermal regime which duplicated that selected by animals following exercise. 3. Animals recovering at a constant 40°C regained their ability to repeat exhaustive activity in less than 85 min, while animals recovering under the other two thermal regimes required between 85 and 100 min of recovery to be able to repeat this activity. Animals recovering at both 40°C and under the variable thermal regime regained their ability to repeat sprint behaviour within 60 min of recovery, while animals recovering at 20°C required more than 100 min of recovery to be able to repeat sprint behaviour. 4. These results formed the basis of the conclusion that the post-exercise behaviour selected by D. dorsalis retards the rate at which the animals recover their ability to repeat exhaustive exercise when compared with recovery at a constant 40°C but does not retard their ability to repeat sprint exercise. 相似文献
This study examines the importance of N source and concentration on plant response to distinct CO2 concentrations and root temperatures. The experimental design of this work was a factorial combination of: CO2 concentration, nitrogen concentration, nitrogen source and root temperature. Carob (Ceratonia siliqua L.) was assessed as a potential model of a slow growing Mediterranean species.
The results showed that: 1) biomass increment under high CO2 varied between 13 and 100 percnt; in relation to plants grown under the same conditions but at ambient CO2 concentrations, depending on the root temperature and nitrogen source; 2) nitrate-fed plants attained a larger increase in biomass production compared to ammonium-fed ones. This performance seems to be linked to the co-ordinated regulation of the activities of glutamine synthetase and sucrose phosphate synthase. The variations in the magnitude and nature of growth responses to elevated CO2 observed resulted in substantial changes in the chemical composition of the plant material and consequently in plant nitrogen use efficiency.
Although performed with seedlings and under controlled conditions, this work emphasizes the importance of the nitrogen source used by the plants, a factor rarely taken into consideration when forecasting plant responses to global changes. Particularly, the results presented here, highlight the potential for uncoupling biomass accumulation from increment of air CO2 concentration and show that more than nitrogen availability N source may offset positive plant growth responses under elevated CO2 and root temperature. 相似文献
Pinus pumila (Pallas) Regel. is a dominant dwarf tree in alpine regions of Japan. The possible factors limiting the net photosynthetic rate (Pn) of the needles of P. pumila were examined in the snow-melting (May) and the summer (August) seasons. In August, in situ maximum Pn was 20 mol kg–1 needle s–1 in the current-year needles and 25 mol kg–1 needle s–1 in the 1-year-old needles. Diurnal trends of Pn in August were positively related to fluctuations in photosynthetic photon flux density (PPFD) and no midday depression of Pn was found, indicating that a decrease in PPFD rather than an increase in needle-to-air vapor pressure deficit (W) might cause the reduction of Pn. Both stomatal conductance (gs) and Pn were lower in May than in August. In May, Pn and gs were almost zero in the morning, but gradually increased with decreasing W, reaching maximum Pn values (4 mol kg–1 needle s–1) and gs (60 mmol kg–1 needle s–1) at 16.00 hours. The daytime Pn in May was positively related to gs. Relative water content in the exposed needles above the snow in May was 83%, which was far above the lethal level. This indicates that the water flow from stems or soils to needles was enough to compensate for a small amount of water loss due to the low gs in May, although the water supplied to needles would be impeded by the low temperatures. Thus, the reduced gs in May would be important for avoiding needle desiccation, and would result in a reduced Pn. 相似文献
On incubation Days 9, 11, 12, 14, or 15, chick embryos were injected intravenously with 4.0 × 106L. donovani amastigotes. Embryos were incubated at 33 C immediately after infection. Numbers of amastigotes found in the liver 1 hr after injection increased as the age of embryo recipients increased. Most 14- or 15-day infected embryos hatched when allowed to do so, but many younger embryos were unable to survive at 33 C. Numbers of amastigotes in the liver of chicks, hatched after infection as embryos, decreased as the cloacal temperature of the chicks increased. Despite a 31 C incubation temperature, chicks exhibited a mean 38.3 C cloacal temperature 1 day after hatching.Chick fibroblast cultures were initiated as explants of embryo brain and infected with amastigotes from hamster spleen. Only amastigotes were seen in cultures kept at 37 C, but extracellular promastigotes and intracellular amastigotes were present in cultures at 33 C. Although promastigotes increased in number in the medium overlay at 33 C, amastigotes decreased in number at 33 C and 37 C. One intracellular amastigote was seen in a culture which had been incubated at 25 C after inoculation with promastigotes. 相似文献