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461.
Comparisons of sympatric species inhabiting the same ecological habitat may elucidate adaptive processes. We studied the physiological patterns of two species of the genus Limicolaria (L. aurora and L. flammea) that thrive in a hot tropical habitat. We examined changes in water content, biochemical fuel reserves and haemolymph enzyme activities during aestivation and activity. Our results indicate that both species had the potential to conserve body water during aestivation. A definite pattern in foot muscle biochemical fuel reserves was observed. Both species depleted glycogen during aestivation while building up lipids. Catabolism of protein was observed during aestivation. Lactate levels and the activity of lactate dehydrogenase both decreased during aestivation, and both variables later increased at the onset of activity. Significantly higher enzyme activities were recorded during aestivation than during the active period. Stepwise discrimination analysis revealed lactate as the significant predictor of differences between the two periods, with 97.9% of the cases correctly classified. No significant correlation was observed between the measured variables and climatic data. Our results suggest that the physiological adaptation of Limicolaria is not environmentally predictable, rather it is inherently determined for ensuring physiological adjustment for survival in the tropics. 相似文献
462.
463.
Paul J. Ferraro Merlin M. Hanauer 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2015,370(1681)
To develop effective protected area policies, scholars and practitioners must better understand the mechanisms through which protected areas affect social and environmental outcomes. With strong evidence about mechanisms, the key elements of success can be strengthened, and the key elements of failure can be eliminated or repaired. Unfortunately, empirical evidence about these mechanisms is limited, and little guidance for quantifying them exists. This essay assesses what mechanisms have been hypothesized, what empirical evidence exists for their relative contributions and what advances have been made in the past decade for estimating mechanism causal effects from non-experimental data. The essay concludes with a proposed agenda for building an evidence base about protected area mechanisms. 相似文献
464.
465.
Background and aimsThis paper is about pollen ecophysiology, anther opening, pollen dispersal and the timing of the male and female phases in Parietaria judaica (Urticaceae).MethodsEcophysiological (effects of different relative humidities (RHs) and osmotic relationships) and cytological methods (stigmatic receptivity, pollen viability, histology and histochemistry) were used to determine pollen and pollination features during the long blooming period of this species.Key resultsPollen is dispersed by rapid uncurling of the filament and anther opening. The filament and anther lack cells with lignified wall thickenings, which are usually responsible for anther opening and ballistic pollen dispersal. Instead, dispersal is the result of the sudden movement of the filament. Pollen is of the partially hydrated type, i.e. with a water content greater than 30% at shedding, and readily loses water, and hence viability, at low RH. Pollen carbohydrate reserves differ with season. Starchless grains germinate quickly and are less subject to water loss. Flowers are protogynous, pollen release occurring only after complete cessation of the female phase within an inflorescence.ConclusionParietaria has partially hydrated pollen which differs from typical pollen of this type because of its reduced size and the absence of callose. Because of its low water content at the time of shedding it survives better at higher RH. Dispersal and pollination are adapted to pollen features. 相似文献
466.
C. Thouzeau S. Massemin Y. Handrich 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):17-24
To assess the role of bone marrow fat in survival during a period of negative energy balance, we investigated the relationship
between the time-course of marrow fat mobilization and the metabolic states associated with body fuel utilization during a
prolonged fast. In order to mimic the winter fast of the barn owl (Tyto alba), captive birds were subjected to fasts of various durations at 5 °C ambient temperature. Body mass and plasma metabolites
were used to determine the metabolic state at the end of fasting. Skeleton composition remained unchanged throughout phase
II of fasting, during which the birds essentially rely on lipid fuels. During the following phase III, characterized by an
increase in net body protein breakdown, the lipid mass in skeleton marrow decreased sharply by 78%, concomitant with an increase
of the bone water content. This marrow fat mobilization occurred in all parts of the skeleton. This observation supports the
hypothesis that bone marrow fat is not only involved in local nutrition, but can also be used as a lipid reserve for total
energy requirements. However, in contrast to other fat deposits, marrow fat is mobilized only during phase III of the fast,
when the last shift from lipid to protein fuel metabolism occurs. Thus, metabolic and/or hormonal changes associated with
this transition could be involved in bone marrow fat mobilization. Lastly, our results suggest that the measurement of bone
marrow fat can be used as an accurate index of the nutritional status (i.e. phase II or phase III) in barn owls.
Accepted: 4 July 1996 相似文献
467.
Protecting endemic seed plants on the Tibetan Plateau under future climate change: migration matters
Aims
Climate change in the near future may become a major threat to high-altitude endemics by greatly altering their distribution. Our aims are to (i) assess the potential impacts of future climate change on the diversity and distribution of seed plants endemic to the Tibetan Plateau and (ii) evaluate the conservation effectiveness of the current National Nature Reserves (NNRs) in protecting the endemic plants in the face of climate change. 相似文献
468.
Wolf U. Blanckenhorn Cornelia Henseler Dieter U. Burkhard Hans Briegel 《Physiological Entomology》2001,26(3):260-265
Abstract. Yellow dung fly ( Scathophaga stercoraria (L.)) populations on cow pastures in Central Europe usually show a characteristic summer decline in fly numbers. This has been related to their sensitivity to hot temperatures, but where and in what state the flies spend the summer has remained unclear. Field enclosure experiments revealed no evidence for survival over summer in the pupal stage, as adults never emerged in early autumn from eggs laid in late spring. Laboratory and field evidence shows instead that adults acclimatize physiologically by suppressing reproduction in favour of accumulating lipid (but not glycogen) reserves. Apparently they spend the summer in cooler, forested areas close to the pastures. As reproduction is not entirely shut down, it is suggested that this represents quiescence rather than diapause. Presumably this increases the survival of the flies during the hottest time of the season, and appears to be a flexible life-history strategy, particularly for late-born spring generation individuals. 相似文献
469.
M.R. Rudge 《New Zealand journal of zoology.》2013,40(4):349-363
Abstract A scientific reserve of 200 ha has been created on Pitt Island, Chatham Islands for some 300 sheep from a flock of merino origin which has been feral for about 70 years. The reserve has a history of burning-off, and of grazing by cattle, sheep, and pigs. Transects have been established to follow changes in the vegetation. Although the original sheep were white, about 90% of the feral sheep have pigmented fleeces. Self-shedding of the wool is common in the population. The contribution that feral mammals can make to genetic conservation, and the problems that they pose to other conservation priorities, are discussed. 相似文献
470.
Abstract 1. Diapause allows insects to cope with adverse weather conditions but also poses substantial fitness costs, e.g. through reduced survival of the diapausing stage or sublethal effects in the following season.
2. The energetic costs of diapause in females of the parasitoid Asobara tabida Nees (Hymenoptera: Braconidae) were assessed using experimental manipulation of diapause duration.
3. An increase in diapause length not only led to higher mortality among diapausing pupae but also caused a significant decrease in egg load, fat reserves, and dry weight of the emerging adult females.
4. Only larvae with sufficient resources were able to survive the entire diapause period and there was a trade-off between the metabolic costs of diapause and adult fitness components.
5. In contrast, the size (tibia length) of emerging females increased with increasing diapause duration. It is proposed that this may be due to a genetic correlation between larval dry weight and adult size, so that selection for heavier larvae would result in larger adults even when resources are limited.
6. Ultimately, the evolution of diapause duration and its consequences for adult performance will depend on the costs of overwintering and the ecological conditions in the habitat. 相似文献
2. The energetic costs of diapause in females of the parasitoid Asobara tabida Nees (Hymenoptera: Braconidae) were assessed using experimental manipulation of diapause duration.
3. An increase in diapause length not only led to higher mortality among diapausing pupae but also caused a significant decrease in egg load, fat reserves, and dry weight of the emerging adult females.
4. Only larvae with sufficient resources were able to survive the entire diapause period and there was a trade-off between the metabolic costs of diapause and adult fitness components.
5. In contrast, the size (tibia length) of emerging females increased with increasing diapause duration. It is proposed that this may be due to a genetic correlation between larval dry weight and adult size, so that selection for heavier larvae would result in larger adults even when resources are limited.
6. Ultimately, the evolution of diapause duration and its consequences for adult performance will depend on the costs of overwintering and the ecological conditions in the habitat. 相似文献