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1.
Developmental times and rates of nucleopolyhedrosis virus infection in third-instar velvetbean caterpillar, Anticarsia gemmatalis, larvae were studied in the laboratory at a variety of constant and variable temperatures. Developmental time was considered to be time from inoculation until death. Viral infection exhibited a temperature optimum of ca. 30°C and was inhibited at 10 and 40°C. Mean developmental time of the virus ranged from 18.1 days (15°C) to 5.5 days (30°C). Means and standard deviations of viral developmental rates (= development time?1) were used as inputs into a previously derived absolute reaction rate model designed to generate a set of kinetic constants usable in predicting developmental times. Actual distributions of viral cohort developmental times were compared to distributions generated by the model. Reasonable agreement between predicted and actual distributions was found at three of four temperatures tested.  相似文献   

2.
The effects of variable daylength and temperature on net rates of photosynthesis, dark respiration, and excretion of a unicellular marine haptophyte, Isochrysis galbana Parke, were examined and related to division rates. Six combinations of daylength (18:6, 12:12, 6:18 light:dark, LD) and temperature (20, 25 C) were used. Daily rates of net photosynthesis were closely correlated to division rates, suggesting a direct relationship, and were maximal when cells were grown at 12:12 LD at both temperatures and 18:6 LD at 20 C. A daylength of 6 hours decreased daily rates by decreasing the time for carbon uptake. Further, cells grown with this daylength had maximal chlorophyll a contents, suggesting a physiological adaptation by photosynthetic units to short light periods. A photoperiod of 18:6 LD at 25 C decreased daily rates of net photosynthesis by reducing the hourly rate of net photosynthesis via an unidentified mechanism. The importance of rates of net dark respiration in controlling daily net photosynthesis was small, with carbon lost during dark periods varying between 4 and 14% of that gained during light periods. Also, the influence of net excretion was small, varying between 1.0 and 5.5% of daily net photosynthesis.  相似文献   

3.
Alkaline protease is a class of important hydrolytic enzymes having wide applications in bioprocess industries. Their optimum pH in the alkaline range and stability at higher temperatures make them ideal in detergent and leather processing industries. These enzymes have excellent depilating capacity. The present study aims at process optimization for the production of alkaline protease from Bacillus amyloliquefaciens ATCC 23844. Information on the optimal operating temperature and pH were elicited from specific growth rates and alkaline protease yields. It was also observed that besides pH and temperature, the oxygen transfer rate is another important limiting variable for the production of protease. Volumetric oxygen transfer coefficient (k L a) was estimated at various impeller speeds and aeration rates. The optimal impeller speed and aeration rates were determined from k L a and the relative protease yield data. It was understood that the oxygen transfer rate is one of the crucial parameters for the production of proteolytic enzymes by B. amyloliquefaciens.  相似文献   

4.
Delayed selfing has been considered the best-of-both-worlds response to pollinator unpredictability because it can provide reproductive assurance without decreasing outcrossing potential. According to this hypothesis, selfing rates in delayed selfing species should be highly variable in fluctuating pollinator environments. To test this prediction, as well to explore the consequences of delayed selfing on genetic patterns, we compared two sister species that grow in the high Andes of Chile: Schizanthus grahamii that exhibits delayed selfing and Schizanthus hookeri, which is self-compatible but requires pollinators for seed set. We estimated genetic diversity within and among five populations of each species using six shared microsatellites. Our results indicated that selfing rates in S. grahamii (range 0.07–0.81) were significantly more variable than in S. hookeri (range 0–0.26). The highest levels of selfing were found in the populations of S. grahamii located at highest altitudes (r = 0.78) and at northern margin range, where pollinators are probably more scarce. These populations also showed the lowest allelic richness and heterozygosity values. Southern populations of S. grahamii had mixed mating, and showed heterozygosity and diversity values close to those detected for S. hookeri along all the sampled range. Selfing in this species results from geitonogamy, and did not covary with altitude. Schizanthus grahamii showed greater population differentiation than S. hookeri. Overall, our results indicated that selfing rates were widely variable in S. grahamii, with some populations predominantly selfing and others showing mixed mating. This pattern may be associated with the strong fluctuations in pollinator service that typically occur in the high Andes of Chile.  相似文献   

5.
Background: The disparity in breast cancer mortality rates among white and black US women is widening, with higher mortality rates among black women. We apply functional time series models on age-specific breast cancer mortality rates for each group of women, and forecast their mortality curves using exponential smoothing state-space models with damping. Materials and Methods: The data were obtained from the Surveillance, Epidemiology and End Results (SEER) program of the US [1]. Mortality data were obtained from the National Centre for Health Statistics (NCHS) available on the SEER*Stat database. We use annual unadjusted breast cancer mortality rates from 1969 to 2004 in 5-year age groups (45–49, 50–54, 55–59, 60–64, 65–69, 70–74, 75–79, 80–84). Age-specific mortality curves were obtained using nonparametric smoothing methods. The curves are then decomposed using functional principal components and we fit functional time series models with four basis functions for each population separately. The curves from each population are forecast and prediction intervals are calculated. Results: Twenty-year forecasts indicate an overall decline in future breast cancer mortality rates for both groups of women. This decline appears to be steeper among white women aged 55–73 and black women aged 60–84. For black women under 55 years of age, the forecast rates are relatively stable indicating there is no significant change in future breast cancer mortality rates among young black women in the next 20 years. Conclusion: White women have smooth and consistent patterns in breast cancer mortality rates for all age-groups whereas the mortality rates for black women are much more variable. The projections suggest, for some age groups, black American women may not benefit equally from the overall decline in breast cancer mortality in the United States.  相似文献   

6.
Populations of three coexisting intertidal gastropods, Nerita atramentosa Reeve, Bembicium nanum (Lamarck) and Cellana tramoserica (Sowerby), were sampled from a shore in Botany Bay, New South Wales, from July 1972 to September 1973. The recruitment and growth rates of each species were analysed from size frequency distributions. Mortality of each age cohort, and longevity, were estimated from analyses of the densities of Nerita atramentosa and Bembicium nanum.Nerita atramentosa showed no significant mortality during the first two years on the shore, but high mortality (at an instantaneous rate of 0.084 deaths/individual/month) after reaching the age of reproductive maturity, which was 20 months from settlement and at a mean shell-length of 13.5 mm. No growth could be detected after reproductive maturity was reached. Longevity of N. atramentosa was estimated as 3–5.5 years. Bembicium nanum juveniles showed higher mortality (at an instantaneous rate of 0.233 deaths/individual/month) than reproductively mature animals (0.060 deaths/individual/month). Reproductive maturity was reached at a mean shell-breadth of 11.0mm, i.e., about ten months after settlement on the shore. Longevity was estimated as from 4–8 years. Cellana tramoserica showed different growth patterns depending on the time of settlement.The three species showed different patterns of growth and life history relating to variable recruitment (which was demonstrated in all three species) and different rates of mortality of age cohorts.  相似文献   

7.
Blooms of the toxin producing dinoflagellate Karenia brevis occur routinely on the West Florida Shelf of the Gulf of Mexico. Nutrient supplies are thought to play a large role in the formation and maintenance of these blooms. The role of top-down control has been less well studied, but grazing, or the lack thereof, on these toxic species may also enhance the formation of large biomass blooms in this region. Zooplankton community structure and copepod species composition were analyzed from samples collected on the West Florida Shelf (WFS) during a NOAA funded ECOHAB regional Karenia Nutrient Dynamics project during October 2007–2010. In 2008 there was no statistical difference in the abundance of zooplankton at bloom and non-bloom stations, however in 2009 there was a statistically significant difference (p < 0.05) between the abundance of zooplankton at stations with Karenia present. To investigate copepod ingestion rates in relation to K. brevis, shipboard and laboratory experiments of the single label method of 14C labeled phytoplankton culture, and time course ingestion experiments with isolated copepods were performed. Calculated ingestion rates suggest that the copepod species Centropages velificatus, and Acartia tonsa ingested K. brevis, however rates were variable among collection sites and K. brevis strains. Parvocalanus crassirostris did not ingest K. brevis in any of the experiments.  相似文献   

8.
In situ measurements of the rates of photosynthesis and calcification in three species of hermatypic corals were made at Eilat, in the Gulf of Aqaba, Red Sea. Experiments were made at 5, 20 and 35 m depth under unusually poor conditions of submarine illumination for the region, and at the relatively low water temperature (21°C) for coral growth which prevails there all year. Estimates of photosynthetic rates by both the 14C and oxygen methods indicated that the 14C method does measure gross photosynthesis in these organisms even at, and below, light compensation points. Substantial rates of carbon fixation in Acropora and Millepora show that, even under bad conditions, these organisms could survive autotrophically to at least 10 m depth, as also could the massive coral Goniastrea although this had much lower photosynthetic rates under the same conditions, compensated for by a much lower respiratory rate than the other two corals.Calcification rates were variable but showed a considerable increase in light as compared with the dark in all three species, and the rates did not decrease with depth as much as might have been anticipated from the reduction in photosynthesis and ambient light energy. Photosynthetic and calcification rates were similar to those reported for similar organisms both in the Caribbean and on the Great Barrier Reef.  相似文献   

9.
The performance of a species can be significantly altered by subtle changes in the physical environmental. The intertidal barnacle Balanus glandula is predominantly an open coast species in the Northeast Pacific. However, B. glandula commonly inhabits estuaries where environmental conditions such as salinity and temperature drastically differ from the open coast. We used survivorship and growth rates as a measure of performance in recently metamorphosed laboratory reared juvenile B. glandula outplanted along an environmental gradient at the mouth, mid-estuarine, and riverine end of the South Slough Estuary, Oregon, USA. Juvenile performance was highly variable over spatial and temporal scales and dependent upon existing environmental conditions. Surprisingly, along this estuarine gradient, juveniles performed better at a mid-estuarine location than at the mouth of the estuary. Typically, the riverine end of the estuary was the least suitable habitat along the estuarine gradient due to high juvenile mortality and a low growth rate. Although seasonally variable, survivorship and growth decreased with height along a vertical intertidal gradient as well. In a reciprocal transplant experiment, populations from both ends of the estuarine gradient displayed similar survivorship and growth rates. Our results demonstrate that the interactions of environmental conditions that vary temporally and spatially along a gradient strongly affect the success of an individual surviving and prospering during the early juvenile period.  相似文献   

10.
Photosynthetic activities in the petunia corolla   总被引:4,自引:3,他引:1       下载免费PDF全文
Pink Petuniahybrida (cv Hit Parade Rosa) corollas were found to contain photosynthetically active chloroplasts. The corolla chloroplasts were similar to those of green leaves in size and structure. The chlorophyll (Chl) content of Petunia corollas increased during early stages of flower development, reaching a maximum just before anthesis. Chloroplasts isolated from corollas at this stage, carried out photosystem I-dependent electron transport at rates which were two-thirds of those measured in chloroplasts from green leaves, but full chain electron transport at only one-quarter of the rate carried out by chloroplasts from green leaves. Both the light saturated rate and the quantum yield for electron transport were lower in corolla chloroplasts, which also required lower intensities for light saturation. Reduced efficiency of photosystem II photoreactions in the corolla was also indicated by the ratio between variable and constant components of Chl fluorescence, which was lower in corollas compared to green leaves. The induction time of Chl fluorescence was at least three times shorter in corollas compared to green leaves, indicating a smaller number of functional photosystem II centers (per Chl) in the corolla. It is suggested that corolla chloroplasts of Petunia might have a role in flower developmental processes.  相似文献   

11.
Hydrophilic matrix tablets are commonly used for extended release dosage forms. For low aqueous-solubility drugs, there may be challenges in modulation of release profiles and achieving consistent release in physiological conditions. To evaluate potential formulation strategies, matrix tablets of a low-soluble drug, hydrochlorothiazide, were developed using hypromellose and two fillers of different solubility, lactose (soluble) or partially pregelatinized maize starch (partially soluble). Additionally, application of an insoluble barrier membrane, aqueous ethylcellulose coating system, and a hydrophilic pore former onto matrix tablets was evaluated. Drug release from uncoated matrix tablets was variable at different agitation rates. Evaluation of tablets in bio-relevant media using physiologically relevant residence time indicated variable and higher initial release rate for uncoated matrices containing lactose but more robust behavior for tablets containing partially pregelatinized starch. Such in vitro behavior may lead to erratic drug release in vivo, when comparing fed versus fasted conditions. Dissolution profiles from barrier membrane-coated tablets showed initial delay, followed by zero-order release kinetics, with reduction or elimination of variability compared to uncoated matrices. Such reduced variability may mitigate mechanical effects of post-prandial stomach. Effects of coating weight gain and inclusion levels of pore former were evaluated and found to be critical in achieving robust and stable release profiles.  相似文献   

12.
Intertidal hermit crabs were stepwise acclimated to 10, 20, and 30‰ salinity (S) and 21 ± 1 °C. Hemolymph osmolality, sodium, chloride, and magnesium were isosmotic (isoionic) to ambient sea water at 30‰ and hyperosmotic (hyperionic) at 20 and 10‰ S, while hemolymph potassium was significantly hyperionic in all acclimation salinities. Total body water did not differ significantly at any acclimation salinity. Oxygen uptake rates were higher in summer-than winter-adapted crabs. No salinity effect on oxygen consumption occurred in winter-adapted individuals. Summer-adapted, 30‰ acclimated crabs had a significantly lower oxygen consumption rate than those acclimated 10 and 20‰ S. Crabs exposed to 30 10 30‰ and 10 30 10‰ semidiurnal (12 h) and diurnal (24.8 h) fluctuating salinity regimes showed variable osmoregulatory and respiratory responses. Hemolymph osmolality followed the osmolality of the fluctuating ambient sea water in all cases, but was regulated hyperosmotically. Hemolymph sodium, chloride, and magnesium concentrations were similar to hemolymph osmolality changes. Sodium levels fluctuated the least. Hemolymph potassium was regulated hyperionically during all fluctuation patters, but corresponded to sea water potassium only under diurnal conditions. The osmoregulatory ability of Clibanarius vittatus (Bosc) resembles that reported for several euryhaline brachyuran species. The time course of normalized oxygen consumption rate changed inversely with salinity under semidiurnal and diurnal 10 30 10‰ S fluctuations. Patterns of 30 10 30‰ S cycles had no effect on oxygen consumption rate time course changes. The average hourly oxygen consumption rates during both semidiurnal fluctuations were significantly lower than respective control rates, but no statistical difference was observed under diurnal conditions.  相似文献   

13.
Dong W  Liu J  Yu J  Wang L  Zhou S 《PloS one》2012,7(4):e35071

Background

At present, plant molecular systematics and DNA barcoding techniques rely heavily on the use of chloroplast gene sequences. Because of the relatively low evolutionary rates of chloroplast genes, there are very few choices suitable for molecular studies on angiosperms at low taxonomic levels, and for DNA barcoding of species.

Methodology/Principal Findings

We scanned the entire chloroplast genomes of 12 genera to search for highly variable regions. The sequence data of 9 genera were from GenBank and 3 genera were of our own. We identified nearly 5% of the most variable loci from all variable loci in the chloroplast genomes of each genus, and then selected 23 loci that were present in at least three genera. The 23 loci included 4 coding regions, 2 introns, and 17 intergenic spacers. Of the 23 loci, the most variable (in order from highest variability to lowest) were intergenic regions ycf1-a, trnK, rpl32-trnL, and trnH-psbA, followed by trnSUGA-trnGUCC, petA-psbJ, rps16-trnQ, ndhC-trnV, ycf1-b, ndhF, rpoB-trnC, psbE-petL, and rbcL-accD. Three loci, trnSUGA-trnGUCC, trnT-psbD, and trnW-psaJ, showed very high nucleotide diversity per site (π values) across three genera. Other loci may have strong potential for resolving phylogenetic and species identification problems at the species level. The loci accD-psaI, rbcL-accD, rpl32-trnL, rps16-trnQ, and ycf1 are absent from some genera. To amplify and sequence the highly variable loci identified in this study, we designed primers from their conserved flanking regions. We tested the applicability of the primers to amplify target sequences in eight species representing basal angiosperms, monocots, eudicots, rosids, and asterids, and confirmed that the primers amplified the desired sequences of these species.

Significance/Conclusions

Chloroplast genome sequences contain regions that are highly variable. Such regions are the first consideration when screening the suitable loci to resolve closely related species or genera in phylogenetic analyses, and for DNA barcoding.  相似文献   

14.
Thalassinidean shrimp are among the most important bioturbators in coastal ecosystems. The species Lepidophthalmus louisianensis and Callichirus islagrande are found in dense aggregations (up to 400 burrows m−2) along sandy and muddy shores of the northern Gulf of Mexico. These shrimp actively ventilate their burrows to provide oxygen and eliminate wastes. In doing so, they expel nutrient-rich burrow water to the overlying water column, potentially altering nutrient cycling and benthic primary productivity. To develop a mechanistic understanding of the role of burrowing shrimp in nutrient processes, we must first examine how changes in environmental conditions alter the frequency, strength, and duration of ventilation. Field measurements of burrow temperature and salinity suggest that the burrow serves as a buffer from the highly variable conditions found in these estuarine, intertidal habitats. Temperatures at sediment depths >30 cm were generally warmer in winter and cooler in summer than at the sediment surface. Burrow salinities, measured at low tide, were consistently higher than adjacent open water. We used these measurements to parameterize laboratory studies of burrow ventilation in artificial burrows made of plastic tubing and in more natural sediment mesocosms, and studies of oxygen consumption in small glass containers. Rates of oxygen consumption and burrow ventilation by L. louisianensis were lower than those of C. islagrande, perhaps reflecting a lower overall activity rate in the former species which resides in less permeable sediments. Generally, increased temperature had a significant positive effect on oxygen consumption for both species. Salinity had no effect on oxygen consumption by L. louisianensis, reflecting the ability of this species to exist in a wide range of salinities. In contrast, oxygen consumption rates of C. islagrande, which is less tolerant of low salinity, were significantly higher at 35‰ than at 20‰. Ventilation rates were highly variable, and shrimp in artificial burrows tended to have consistently higher ventilation rates than those in sediment mesocosms. There is a trend toward more frequent ventilation at 30 °C for both species. Salinity had no effect on ventilation for either species. Our results suggest that thalassinideans exhibit highly variable and species-specific ventilation patterns that are more likely to be affected by temperature than salinity. Increased ventilation at higher temperatures seems to coincide with increased oxygen consumption at these temperatures, although a similar finding was not made for salinity treatments.  相似文献   

15.
Temperature determines all physiological responses by limiting cellular reaction rates. Daily temperature variation differs between microhabitats, which means that subpopulations of the same species may respond differently to temperature. The aim of this study is to determine how physiological responses to temperature of the limpet Cellana tramoserica differ between limpets from variable and from stable thermal environments. Oxygen consumption and anaerobic and aerobic metabolic capacities were measured over a range of temperatures in limpets from thermally stable and variable field sites in summer and winter, and in laboratory acclimation treatments. Limpets from both variable and stable sites, showed acclimatisation of anaerobic and aerobic potentials. Limpets from stable environments, but not from variable environments, showed increased oxygen consumption in winter. Comparison of field and laboratory data showed that temperature was the signal for acclimatisation. The physiological response of C. tramoserica to temperature depends on season and microhabitat. Care must therefore be taken when conducting interspecies comparisons of response to temperature to address the confounding effects of phenotypic plasticity. Differences in physiological response to temperature in phenotypically flexible species like C. tramoserica may simply reflect individual reactions to immediate environmental conditions.  相似文献   

16.
The complete mitochondrial DNA (mtDNA) control region was analyzed from five species of the subfamily Caprinae; Naemorhedus caudatus, N. goral, Capra hircus, Capricornis swinhoei, and Capricornis crispus. Among these species, the control region ranged from 1,096 to 1,212 bp in length. Our results were compatible with the scheme of three domains (ETAS, Central, and CSB) within the control region. A + T < G + C was observed in all the domains. In the Korean gorals, of the 31 variable sites in the whole control region resulting in 15 haplotypes, 27 variable sites were in the ETAS domain. We found two to three tandem repeat in all five species examined in this study, three in N. caudatus and N. goral, two in Capra hircus and C. crispus, and one in C. swinhoei, respectively. All of these repeat units include two short sections of mirror symmetry (TACAT and ATGTA). Short mirror symmetries were well-resolved among five different species, although left domain has high substitution rates. By Kimura’s two parameter method, the genetic distances between the genera Naemorhedus and Capricornis were calculated and divergence time between Naemorhedus and Capricornis may be nearly 2Myr.  相似文献   

17.
Climate change is altering temperatures and precipitation patterns all over the world. In Patagonia, Argentina, predicted increase in precipitation together with rapidly melting glaciers increase the surface runoff, and thereby the transport of suspended solids to recipient lakes. Suspended solids affect the visual conditions in the water which in turn restricts visual foraging. The native fish Aplochiton zebra Jenyns, and its filter-feeding cladoceran prey, Daphnia commutata Ekman, were subjected to foraging experiments at three turbidity levels. A. zebra foraging rate was substantially reduced at naturally occurring turbidity levels and the filtering rate of D. commutata was reduced at the highest turbidity level. This indicates that Daphnia may be partly released from predation from A. zebra at the same time as it can maintain relatively high feeding rates as turbidity increases. Lower foraging rates at the same time as the metabolic demand increases, through increased temperatures, may result in larger effects on A. zebra than could be expected from increases in turbidity or temperature alone. Turbidity may, as an indirect effect of climate change, decrease planktivore foraging rates and thereby alter the interaction strength between trophic levels.  相似文献   

18.
The rate of oxygen uptake of three species of tropical intertidal gastropods,Nerita tessellata Gmelid., N. Versicolor Gmelin and N. Peloronta L., have been investigated under different environmental conditions. In all species the rates increased from 30 to 37°C, were depressed at 20 °C and were not size-dependent at that temperature. The rates of oxygen uptake varied between individuals collected from different habitats and were greater in areas of higher mean maximum daily temperatures, lower rainfall and lower wind speeds than in areas with the reverse conditions. A decrease in oxygen uptake was shown to occur with an increase of exposure time of the animals on the shore and in the laboratory. Rates were higher in two species collected at the time of high tide than those collected at the same level after exposure to low tides.  相似文献   

19.
20.
The relationship between rate of larval development and the potential to prolong larval life was examined for larvae of the marine prosobranch gastropod Crepidula plana Say. Larvae were maintained in clean glass dishes at constant temperatures ranging from 12–29°C and fed either Isochrysis galbana Parke (ISO) or a Tahitian strain of Isochrysis species (T-ISO). Under all conditions, larvae grew at constant rates, as determined by measurements of shell length and tissue biomass. Most larvae eventually underwent spontaneous metamorphosis. Regardless of temperature, faster growth was associated with a shorter planktonic stage prior to spontaneous metamorphosis. Within an experiment, higher temperatures generally accelerated growth rates and reduced the number of days from hatching to spontaneous metamorphosis. However, growth rates were independent of temperature for larvae fed ISO at 25 and 29°C and for larvae fed T-ISO at 20 and 25°C. Where growth rates were unaffected by temperature, time to spontaneous metamorphosis was similarly unaffected. Maximum durations of larval life at a given temperature were shorter for larvae of Crepidula plana than for those of the congener C. fornicata (L.), although both species grew at comparable rates. Interpretations of the ecological significance of these interspecific differences in delay capabilities will require additional data on adult distributions and larval dispersal patterns in the field.  相似文献   

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