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Growth Rate (growth + rate)
Kinds of Growth Rate Terms modified by Growth Rate Selected AbstractsEVOLUTION OF INTRINSIC GROWTH RATE: METABOLIC COSTS DRIVE TRADE-OFFS BETWEEN GROWTH AND SWIMMING PERFORMANCE IN MENIDIA MENIDIAEVOLUTION, Issue 6 2006Stephen A. Arnott Abstract There is strong evidence that genetic capacity for growth evolves toward an optimum rather than an absolute maximum. This implies that fast growth has a cost and that trade-offs occur between growth and other life-history traits, but the fundamental mechanisms are poorly understood. Previous work on the Atlantic silverside fish Menidia menidia has demonstrated a trade-off between growth and swimming performance. We hypothesize that the trade-off derives from the competing metabolic demands associated with growth and swimming activity. We tested this by measuring standard metabolic rate (MSTD), maximum sustainable metabolic rate (MACT) and metabolic scope of laboratory-reared silversides originating from two geographically distinct populations with well-documented differences in genetic capacity for growth. The fast-growth genotype had a significantly greater MSTD than the slow-growth genotype, but a similar MACT when swum to near exhaustion. The scope for activity of the fast-growth genotype was lower than that of the slow-growth genotype. Furthermore, the fast-growth genotype eats larger meals, thereby incurring a greater postprandial oxygen demand. We conclude that a metabolic trade-off occurs between growth and other metabolic demands and that this trade-off provides a general mechanism underlying the evolution of growth rate. [source] VARIATION OF LAG TIME AND SPECIFIC GROWTH RATE AMONG 11 STRAINS OF SALMONELLA INOCULATED ONTO STERILE GROUND CHICKEN BREAST BURGERS AND INCUBATED AT 25C,JOURNAL OF FOOD SAFETY, Issue 4 2000THOMAS P. OSCAR ABSTRACT One strain of 11 serotypes or 11 strains of Salmonella, which were isolated from the ceca of broilers, were surveyed for their growth kinetics on sterile ground chicken breast burgers incubated at 25C to determine the variation of lag time and specific growth rate. Growth curves, four per strain, were fit to a two-phase linear model to determine lag time (h) and specific growth rate (log10/h). Repeatability of growth kinetics measurements for individual strains had a mean coefficient of variation of 11.7% for lag time (range: 5.8 to 17.3%) and a mean coefficient of variation of 6.7% for specific growth rate (range: 2.7 to 13.3%). Lag time among strains ranged from 2.2 to 3.1 h with a mean of 2.8 h for all strains, whereas specific growth rate among strains ranged from 0.3 to 0.38 log10 per h with a mean of 0.35 log10per h for all strains. One-way analysis of variance indicated that lag time (P =0.029) and specific growth rate (P =0.025) differed slightly among strains. S. Haardt had a shorter (P < 0.05) lag time than S. Agona and S. Brandenburg, whereas the specific growth rate of S. Enteritidis was less than (P < 0.05) the specific growth rates of S. Typhimurium and S. Brandenburg. All other strains had similar lag times and specific growth rates. The coefficient of variation among strains was 9.4% for lag time and 5.7% for specific growth rate. These results indicate that there were only minor differences in the lag times and specific growth rates among the strains of Salmonella surveyed. Thus, the growth kinetic values obtained with one strain of Salmonella may be useful for predicting the growth of other strains of Salmonella for which data do not currently exist. [source] FERRIC CHELATE REDUCTASE ACTIVITY AS AFFECTED BY THE IRON-LIMITED GROWTH RATE IN FOUR SPECIES OF UNICELLULAR GREEN ALGAE (CHLOROPHYTA)1JOURNAL OF PHYCOLOGY, Issue 3 2002Harold G. Weger Four species of green algae (Chlorella kessleri Fott et Nováková, Chlorococcum macrostigmatum Starr, Haematococcus lacustris[Girod-Chantrans] Rostaf., Stichococcus bacillaris Näg.) were grown in iron-limited chemostats and under phosphate limitation and iron (nutrient) sufficiency. For all four species, steady-state culture density declined with decreasing degree of iron limitation (increasing iron-limited growth rate), whereas chl per cell or biovolume increased. Plasma membrane ferric chelate reductase activity was enhanced by iron limitation in all species and suppressed by phosphate limitation and iron sufficiency. These results confirm previous work that C. kessleri uses a reductive mechanism of iron acquisition and also suggest that the other three species use the same mechanism. Although imposition of iron limitation led to enhanced activities of ferric chelate reductase in all species, the relationship between ferric chelate reductase activity and degree of iron limitation varied. Ferric chelate reductase activity in C. macrostigmatum and S. bacillaris was an inverse function of the degree of iron limitation, with the most rapidly growing iron-limited cells exhibiting the highest ferric chelate reductase activity. In contrast, ferric chelate reductase activity was only weakly affected by the degree of iron limitation in C. kessleri and H. lacustris. Calculation of ferric reductase activity per unit chl allowed a clear differentiation between iron-limited and iron-sufficient cells. The possible extension of the ferric chelate reductase assay to investigate the absence or presence of iron limitation in natural waters may be feasible, but it is unlikely that the assay could be used to estimate the degree of iron limitation. [source] RELATIVE CONTRIBUTION OF THE PRENATAL VERSUS POSTNATAL PERIOD ON DEVELOPMENT OF HYPERTENSION AND GROWTH RATE OF THE SPONTANEOUSLY HYPERTENSIVE RATCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2006Robert Di Nicolantonio SUMMARY 1To determine the relative roles of the prenatal and postnatal (preweaning) environment on the development of blood pressure and growth rate in the spontaneously hypertensive rat (SHR) of the Okamoto strain, we used combined embryo transfer and cross-fostering techniques between SHR and normotensive Wistar-Kyoto (WKY) rats to produce offspring whose development was examined during the first 20 weeks of life. 2We measured litter sizes, bodyweights and tail-cuff blood pressures in offspring at 4, 8, 12 and 20 weeks of age. We also recorded heart, kidney and adrenal weights at 20 weeks of age, when the study concluded. 3We found that both the in utero and postnatal environments provided by the SHR mother could significantly affect WKY rat offspring growth rates, but blood pressure was unaffected in this strain. In SHR offspring, the SHR maternal in utero and suckling period both contributed to the rate of blood pressure development in the SHR, but not the final blood pressure of offspring at 20 weeks of age. This effect was greater for male than female offspring. Organ weights were largely unaffected by the perinatal environment in either strain. 4We conclude that although the SHR maternal in utero and immediate postnatal environment both contribute to the rate of blood pressure development in the SHR, they do not appear to contribute to the final blood pressure of offspring at maturity. The SHR maternal environment also alters growth rate that may, in turn, underlie these effects on SHR blood pressure development, particularly in males. [source] SPATIOTEMPORAL REORGANIZATION OF GROWTH RATES IN THE EVOLUTION OF ONTOGENYEVOLUTION, Issue 4 2000Miriam L. Zelditch Abstract. Heterochrony, evolutionary changes in rate or timing of development producing parallelism between ontogeny and phylogeny, is viewed as the most common type of evolutionary change in development. Alternative hypotheses such as heterotopy, evolutionary change in the spatial patterning of development, are rarely entertained. We examine the evidence for heterochrony and heterotopy in the evolution of body shape in two clades of piranhas. One of these is the sole case of heterochrony previously reported in the group; the others were previously interpreted as cases of heterotopy. To compare ontogenies of shape, we computed ontogenetic trajectories of shape by multivariate regression of geometric shape variables (i.e., partial warp scores and shape coordinates) on centroid size. Rates of development relative to developmental age and angles between the trajectories were compared statistically. We found a significant difference in developmental rate between species of Serrasalmus, suggesting that heterochrony is a partial explanation for the evolution of body shape, but we also found a significant difference between their ontogenetic transformations; the direction of the difference between them suggests that heterotopy also plays a role in this group. In Pygocentrus we found no difference in developmental rate among species, but we did find a difference in the ontogenies, suggesting that heterotopy, but not heterochrony, is the developmental basis for shape diversification in this group. The prevalence of heterotopy as a source of evolutionary novelty remains largely unexplored and will not become clear until the search for developmental explanations looks beyond heterochrony. [source] MEASUREMENT OF IN SITU SPECIFIC GROWTH RATES OF MICROCYSTIS (CYANOBACTERIA) FROM THE FREQUENCY OF DIVIDING CELLS,JOURNAL OF PHYCOLOGY, Issue 5 2009Yoshimasa Yamamoto Diel changes in the frequency of dividing cells (FDC) of three Microcystis species were investigated in a small eutrophic pond from July to October 2005. The representative species was M. aeruginosa (Kütz.) Kütz., constituting 57%,86% of the Microcystis population throughout the study period, and the remainder were M. viridis (A. Braun) Lemmerm. and M. wesenbergii (Komárek) Komárek. The FDC of M. aeruginosa and M. wesenbergii increased in the daytime and fell in the nighttime in July and August, but this regular variation was not observed in September or October. The in situ specific growth rates of Microcystis species were estimated based on the assumption that the specific growth rate can be given as an absolute value of the derivative of FDC with respect to time. The calculated values were similar among species,0.15,0.38 · d,1 for M. aeruginosa, 0.14,0.63 · d,1 for M. viridis, and 0.18,0.61 · d,1 for M. wesenbergii. The specific growth rates in July and August slightly exceeded those in September and October. The analysis of the in situ specific growth rate of Microcystis indicated that recruitment of the benthic population or morphological change, rather than massive growth, was at least partly responsible for the dominance of M. aeruginosa in the study pond. [source] Advancing Firm Growth Research: A Focus on Growth Mode Instead of Growth RateENTREPRENEURSHIP THEORY AND PRACTICE, Issue 2 2010Alexander McKelvie The development of firm growth research has been notably slow. In this paper, we argue that a major reason for this lack of development is the impatience of researchers to prematurely address the question of "how much?" before adequately providing answers to the question "how?" On the basis of an extensive review of the literature, we suggest how growth research can advance by changing focus to growth mode (organic, acquisition, hybrid). Toward this end, we provide a research agenda that helps establish the types of questions that growth researchers can ask within this new focus. [source] Modeling the Lag Phase and Growth Rate of Listeria monocytogenes in Ground Ham Containing Sodium Lactate and Sodium Diacetate at Various Storage TemperaturesJOURNAL OF FOOD SCIENCE, Issue 7 2007C.-A. Hwang ABSTRACT:, Refrigerated ready-to-eat (RTE) meats contaminated with Listeria monocytogenes were implicated in several listeriosis outbreaks. Lactate and diacetate have been shown to control L. monocytogenes in RTE meats. The objective of this study was to examine and model the effect of lactate (1.0% to 4.2%) and diacetate (0.05% to 0.2%) in ground ham on the lag phase duration (LPD, h) and growth rate (GR, log CFU/h) of L. monocytogenes at a range of temperatures (0 to 45 °C). A 6-strain mixture of L. monocytogenes was inoculated into ground ham containing lactate and diacetate, and stored at various temperatures. The LPD and GR of L. monocytogenes in ham as affected by lactate, diacetate, and storage temperature were analyzed and accurately represented with mathematical equations. Resulting LPD and GR equations for storage temperatures within the range of 0 to 36 °C significantly represented the experimental data with a regression coefficient of 0.97 and 0.96, respectively. Significant factors (P < 0.05) that affected the LPD were temperature, lactate, diacetate, and the interactions of all three, whereas only temperature and the interactions between temperature and lactate and diacetate had a significant effect on GR. At suboptimal growth temperatures (,12 °C) the increase of lactate and diacetate concentrations, individually or in combination, extended the LPD. The effect of higher concentrations of both additives on reducing the GR was observed only at temperatures that were more suitable for growth of L. monocytogenes, that is, 15 to 35 °C. These data may be used to assist in determining concentrations of lactate and diacetate in cooked ham products to control the growth of L. monocytogenes over a wide range of temperatures during manufacturing, distribution, and storage. [source] The Use of Dynamic Financial Analysis to Determine Whether an Optimal Growth Rate Exists for a Property-Liability InsurerJOURNAL OF RISK AND INSURANCE, Issue 4 2004Stephen P. D'Arcy Prior research on the aging phenomenon has demonstrated that new business for property-liability (P-L) insurers generates high loss ratios that gradually decline as a book of business goes through successive renewal cycles. Although the experience on new business is initially unprofitable, the renewal book of business eventually becomes profitable over time. Within this context, insurers need to manage their exposure growth in order to maximize long run profitability. Dynamic financial analysis (DFA), a relatively new tool for P-L insurers, utilizes Monte Carlo simulation to generate the overall financial results for an insurer under a large number of scenarios. This article uses a publicly available DFA model,along with the estimated market value of an insurer, based on 1990,2001 data for stock P-L insurers and underlying financial variables,to determine optimal growth rates of a P-L insurer based on mean,variance analysis, stochastic dominance, and constraints on leverage. [source] Distinguishing Effects on Tumor Multiplicity and Growth Rate in Chemoprevention ExperimentsBIOMETRICS, Issue 4 2000David B. Dunson Summary. In some types of cancer chemoprevention experiments and short-term carcinogenicity bioassays, the data consist of the number of observed tumors per animal and the times at which these tumors were first detected. In such studies, there is interest in distinguishing between treatment effects on the number of tumors induced by a known carcinogen and treatment effects on the tumor growth rate. Since animals may die before all induced tumors reach a detectable size, separation of these effects can be difficult. This paper describes a flexible parametric model for data of this type. Under our model, the tumor detection times are realizations of a delayed Poisson process that is characterized by the age-specific tumor induction rate and a random latency interval between tumor induction and detection. The model accommodates distinct treatment and animal-specific effects on the number of induced tumors (multiplicity) and the time to tumor detection (growth rate). A Gibbs sampler is developed for estimation of the posterior distributions of the parameters. The methods are illustrated through application to data from a breast cancer chemoprevention experiment. [source] Global Gene Expression Differences Associated with Changes in Glycolytic Flux and Growth Rate in Escherichia coli during the Fermentation of Glucose and XyloseBIOTECHNOLOGY PROGRESS, Issue 1 2002Ramon Gonzalez The simplicity of the fermentation process (anaerobic with pH, temperature, and agitation control) in ethanologenic Escherichia coli KO11 and LY01 makes this an attractive system to investigate the utility of gene arrays for biotechnology applications. By using this system, gene expression, glycolytic flux, and growth rate have been compared in glucose-grown and xylose-grown cells. Although the initial metabolic steps differ, ethanol yields from both sugars were essentially identical on a weight basis, and little carbon was diverted to biosynthesis. Expression of only 27 genes changed by more than 2-fold in both strains. These included induction of xylose-specific operons ( xylE, xylFGHR, and xylAB) regulated by XylR and the cyclic AMP,CRP system and repression of Mlc-regulated genes encoding glucose uptake ( ptsHIcrr, ptsG) and mannose uptake ( manXYZ) during growth on xylose. However, expression of genes encoding central carbon metabolism and biosynthesis differed by less than 2-fold. Simple statistical methods were used to investigate these more subtle changes. The reproducibility (coefficient of variation of 12%) of expression measurements (mRNA as cDNA) was found to be similar to that typically observed for in vitro measurements of enzyme activities. Using Studentapos;s t test, many smaller but significant sugar-dependent changes were identified ( p < 0.05 in both strains). A total of 276 genes were more highly expressed during growth on xylose; 307 genes were more highly expressed with glucose. Slower growth (lower ATP yield) on xylose was accompanied by decreased expression of 62 genes concerned with the biosynthesis of small molecules (amino acids, nucleotides, cofactors, and lipids), transcription, and translation; 5 such genes were expressed at a higher level. In xylose-grown cells, 90 genes associated with the transport, catabolism, and regulation of pathways for alternative carbon sources were expressed at higher levels than in glucose-grown cells, consistent with a relaxation of control by the cyclic AMP,CRP regulatory system. Changes in expression of genes encoding the Embden,Meyerhof,Parnas (EMP) pathway were in excellent agreement with calculated changes in flux for individual metabolites. Flux through all but one step, pyruvate kinase, was predicted to be higher during glucose fermentation. Expression levels (glucose/xylose) were higher in glucose-grown cells for all EMP genes except the isoenzymes encoding pyruvate kinase ( pykA and pykF). Expression of both isoenzymes was generally higher during xylose fermentation but statistically higher in both strains only for pykF encoding the isoenzyme activated by fructose-6-phosphate, a key metabolite connecting pentose metabolism to the EMP pathway. The coordinated changes in expression of genes encoding the EMP pathway suggest the presence of a common regulatory system and that flux control within the EMP pathway may be broadly distributed. In contrast, expression levels for genes encoding the Pentose,Phosphate pathway did not differ significantly between glucose-grown and xylose-grown cells. [source] Analysis of Mycelial Growth Rates and RAPD-PCR Profiles in a Population of Gaeumannomyces graminis var. tritici Originating from Wheat Plants Grown from Fungicide-treated SeedJOURNAL OF PHYTOPATHOLOGY, Issue 6 2005Z. Weber Abstract Linear mycelial growth rates of 70 isolates of Gaeumannomyces graminis var. tritici on agar medium amended or unamended with the fungicide silthiofam were not correlated. Mycelial growth rate was not influenced by the fungicide applied to the seed of the plants from, which the isolates originated. DNA polymorphism determined by randomly amplified polymorphic DNA (RAPD) polymerase chain reaction was used to assess genetic variation among isolates. Thirty RAPD markers generated with five arbitrary 10-mer primers revealed DNA polymorphism suitable for assessing variability in this fungal population. Cluster analysis of RAPD data identified two groups at the 54% similarity level. There was a significant relationship between the presence of 11 markers and sensitivity to silthiofam. [source] Legislating for Economic Sclerosis: Are Lawyers a Baleful Influence on Growth Rates?KYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 1 2004Sam Cameron Summary William Easterly, an ex-World Bank economist and widely respected growth theorist, in recently noting that skilled individuals may elect to pursue occupations that redistribute income rather than enhance growth, referred to ,the somewhat whimsical piece of evidence , that economies with lots of lawyers grow more slowly than economies with lots of engineers'. The remark alluded to an assertion by the Bush-Quayle camp during the 1992 Presidential campaign that too many lawyers were prejudicial to US economic growth, and sparked a heated debate that was played out in the Wall Street Journal and a number of academic journals at the time. A decade later, Easterly's rejoinder has prompted us to examine the view that occupational capture (the capture of talent by particular occupations) can contribute to economic stagnation, by revisiting the notion of lawyers as negative externalities to the growth process. [source] Determinants of Cross-Sectional Variation in Discount Rates, Growth Rates and Exit Cap RatesREAL ESTATE ECONOMICS, Issue 2 2004Åke Gunnelin This study investigates the determinants of key input variables in valuers' discounted cash flow models used for estimating market values for offices. Data from 599 valuations in 2000 from Stockholm, Gothenburg and Malmö are used to explain variation in discount rates, expected growth rates in net operating income and exit cap rates. Our ability to explain the relatively wide variation in appraisal assumptions with plausible covariates generates confidence in the appraisal process. This has important implications because most value and returns indices of commercial real estate worldwide are appraisal based. [source] Food composition, habitat use and growth of stocked and native Arctic charr, Salvelinus alpinus, in Lake Muddusjärvi, FinlandFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2002K. KAHILAINEN Habitat use, growth and food composition of native and stocked Arctic charr, Salvelinus alpinus (L.), were studied in the subarctic Lake Muddusjärvi, northern Finland, to investigate reasons for poor stocking success. Samples were collected with pelagic and epibenthic gill nets. Stocked and native charr occurred in similar epibethic habitats, whereas pelagic habitat was avoided. Native charr grew fast after shifting to piscivory. Growth rate of stocked charr was slow because only a small proportion of stocked fish became piscivorous during the first year after stocking. During the first lake year, stocked charr divided into slow-growing planktivores and fast-growing piscivores. Piscivorous stocked and native charr consumed only whitefish, Coregonus lavaretus (L.), as their prey. Small-sized (<10 cm) whitefish were preferred when shifting to piscivory. [source] Growth and reproduction of three cladoceran species from a small wetland in the south-eastern U.S.A.FRESHWATER BIOLOGY, Issue 4 2003A. M. Lemke SUMMARY 1.,Growth, reproduction and life-history parameters were measured for three cladoceran species from a small south-eastern wetland, U.S.A. Simocephalus serrulatus, Diaphanosoma brachyurum and Scapholeberis mucronata juveniles were reared at temperatures between 10 and 25 °C on natural food resources. 2.,Growth rate increased with temperature and decreased with individual size for all three species. Maximum somatic growth rate was higher for Simocephalus (49,72% day,1) and Diaphanosoma (21,91% day,1) than for Scapholeberis (11,45% day,1). Multiple regression equations were developed which predict temperature- and mass-specific growth rates for each species. 3.,Scapholeberis egg production was positively related to temperature; however, maximum egg production occurred at intermediate temperatures for Simocephalus and Diaphanosoma. Mean cumulative egg production was higher for Scapholeberis (28,92 eggs per female) than for Simocephalus (18,25 eggs per female) and Diaphanosoma (1,41 eggs per female), and was related to differences in reproductive strategy and survival. 4.,Survival was inversely related to temperature in most cases. For all three cladocerans, the intrinsic rate of increase (r) and net reproductive rate (R0) increased with temperature, whereas generation time (G) decreased. Greater egg production by Scapholeberis compared with the other two cladocerans was consistent with higher R0 values for Scapholeberis at any given temperature. Although r was very similar among species, G was typically longer for Scapholeberis than for Simocephalus and Diaphanosoma. 5.,This analysis provides basic information about the population parameters of these coexisting wetland species, and the growth rate models can be applied to field data to determine production dynamics. [source] Growth-enhanced fish can be competitive in the wildFUNCTIONAL ECOLOGY, Issue 5 2001J. I. Johnsson Summary 1,The widespread commercial interest in producing growth-enhanced organisms has raised concerns about ecological consequences, emphasizing the need to understand the costs and benefits associated with accelerated growth in nature. Here, sustained-release growth hormone (GH) implants were used to estimate the competitive ability of growth-enhanced fish in the wild. Growth rate, movements and survival over winter were compared between GH-implanted and control Brown Trout in a natural stream. The study was repeated over two consecutive years. 2,GH treatment had no effect on recapture rates, indicating that mortality rates did not differ between GH-treated and control fish. More GH-treated trout (63%) than control fish (41%) were recaptured within their 10 m section of release. Thus, GH-treated fish were more stationary than control fish over winter. 3,GH-treated fish grew about 20% faster than control fish. This was mainly because of a three-fold growth rate increase in GH-treated fish in late summer, whereas growth rates over winter did not differ significantly between treatment groups. These results were consistent over both replicate years. 4,This first study of growth-enhanced fish in the wild shows that they can survive well and therefore may out-compete normal fish with lower growth rates. Although selection against rapid growth may be more intense at other life-history stages and/or during periods of extreme climate conditions, our findings raise concerns that released or escaped growth-enhanced salmonids may compete successfully with resident fish. It is clear that the potential ecological risks associated with growth-enhanced fish should not be ignored. [source] Annual dynamics variation of a landlocked Galaxias maculatus (Jenyns 1842) population in a Northern Patagonian river: occurrence of juvenile upstream migrationJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2007J. P. Barriga Summary Galaxias maculatus, broadly distributed in the southern hemisphere, presents both diadromic and landlocked populations. The upstream migration of larvae and juveniles from the sea to freshwater habitats is a characteristic phenomenon of diadromous populations, but upstream migration has never been reported in those that are landlocked. The objective of this study was to establish the population dynamics of a peculiar riverine landlocked population that presents an upstream migration at the larvae,juvenile transition from the Piedra del Águila Reservoir to the Caleufú River (Argentina). A spawning season from September to November and the arrival of shoals of metamorphic larvae and juveniles from February to April to the adult habitat were coincidental with lacustrine landlocked populations, but not with diadromous populations. Growth rate and age at migration, 147 ± 22.6 days, were also similar to other landlocked and diadromous populations. The arrival of these shoals produced a 20-fold increase in fish density while the two cohorts of G. maculatus overlapped in time and space. No significant differences in morphology or vertebrae number were detected when riverine and reservoir adults were compared. The great life history plasticity of G. maculatus, shown to be even greater in our results, could be the key to explain the wide distribution of this species in the southern hemisphere. Likewise, discovering this juvenile potamodromous behaviour in a landlocked population will provide a new view for the analysis of the ways of this species' dispersion in continental waters. [source] A quantitative genetic analysis of leaf beetle larval performance on two natural hosts: including a mixed dietJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2000Ballabeni Published quantitative genetic studies of larval performance on different host plants have always compared performance on one host species or genotype vs. performance on another species or genotype. The fact that some insects may feed on more than one plant species during their development has been neglected. We executed a quantitative genetic analysis of performance with larvae of the leaf beetle Oreinaelongata, raised on each of two sympatric host plants or on a mixture of them. Growth rate was higher for larvae feeding on Adenostylesalliariae, intermediate on the mixed diet and lowest on Cirsium spinosissimum. Development time was shortest on A. alliariae, intermediate on mixed diet and longest on C. spinosissimum. Survival was higher on the mixed diet than on both pure hosts. Genetic variation was present for all three performance traits but a genotype by host interaction was found only for growth rate. However, the reaction norms for growth rate are unlikely to evolve towards an optimal shape because of a lack of heritability of growth rate in each single environment. We found no negative genetic correlations for performance traits among hosts. Therefore, our results do not support a hypothesis predicting the existence of between-host trade-offs in performance when both hosts are sympatric with an insect population. We conclude that the evolution of host specialized genotypes is unlikely in the study population. [source] Growth of larval Pacific anchovy Engraulis japonicus in the Yellow Sea as indicated by otolith microstructure analysisJOURNAL OF FISH BIOLOGY, Issue 6 2006S.-D. Hwang Larval Pacific anchovy Engraulis japonicus were sampled from coastal waters off the central west coast of Korea from June to November 1996. Using otolith microstructure analysis (daily growth increments), three cohorts (spring, early summer and late summer) were distinguished based on backcalculated spawning dates. Growth rates differed between cohorts, with higher growth rates for late-summer cohorts than either the spring or early-summer cohorts. Growth rate was positively related to surface water temperature, with an optimum temperature range of between 20 and 26° C occurring during the late summer (late July through to mid-September). The study highlights that early growth rates of Pacific anchovy are dependent on ecosystem (particularly water temperature) attributes during early life. [source] Changes in vertebral structure during growth of reared rainbow trout, Oncorhynchus mykiss (Walbaum): a new approach using modelling of vertebral bone profilesJOURNAL OF FISH DISEASES, Issue 3 2009M-H Deschamps Abstract Severe bone resorption of the vertebral body in reared rainbow trout was thought to be a dysfunction in mineral balance induced by increased growth rate in unfavourable rearing conditions. To verify this assumption, we sampled market-sized trout (c. 250 g) from 20 fish farms with different rearing conditions. Growth rate was also studied by sampling trout reared in three different water temperatures from fry to market-size. Transverse sections of vertebrae were microradiographed, then digitized. Total bone area (Tt-B.Ar.) and bone profiles were obtained using BONE PROFILER 3.23 software and a mathematical model was developed to statistically compare bone profiles using 12 parameters in four vertebra regions. Tt-B.Ar. and bone profiles were found to vary with rearing conditions and growing temperatures, indicating obvious influences of these factors on bone remodelling. However, vertebral resorption was found to be a general phenomenon. In trout from 190 to 235 mm in length, vertebrae underwent important remodelling resulting in large resorption of the middle area, while the transition and peripheral areas showed an increase in bone deposition. Changes in vertebra architecture seem to be a good compromise between the need to mobilize stored minerals during growth while maintaining vertebral biomechanical properties. [source] Ossification sequence of the avian order anseriformes, with comparison to other precocial birdsJOURNAL OF MORPHOLOGY, Issue 9 2008Erin E. Maxwell Abstract Ossification sequences are poorly known for most amniotes, and yet they represent an important source of morphogenetic, phylogenetic, and life history information. Here, the author describes the ossification sequences of three ducks, the Common Eider Somateria mollissima dresseri, the Pekin Duck Anas platyrhynchos, and the Muscovy Duck Cairina moschata. Sequence differences exist both within and among these species, but are generally minor. The Common Eider has the most ossified skeleton prior to hatching, contrary to what is expected in a subarctic migrant species. This may be attributed to a tradeoff between growth rate and locomotory performance. Growth rate is higher in hatchlings with more cartilaginous skeletons, but this may compromise locomotion. No major ossification sequence differences were observed in the craniofacial skeleton when compared with Galliformes, which suggests that the influence of adult morphology on ossification sequence might be relatively minor in many taxa. Galliformes and Anseriformes, while both highly ossified at hatching, differ in the location of their late-stage ossification centers. In Anseriformes, these are most often located in the appendicular skeleton, whereas in Galliformes they are in the thoracic region and form the ventilatory apparatus. J. Morphol., 2008. © 2008 Wiley-Liss, Inc. [source] 133 Studies on the Life History of the Portuguese Red Alga Porphyra Dioica (Brodie and Irvine) Under Varying Environmental ConditionsJOURNAL OF PHYCOLOGY, Issue 2003R. Pereira The life history of Porphyra dioica collected in Porto, Portugal, was investigated under laboratory conditions. This is one of the most common Porphyra species on the North Coast of Portugal and can be found throughout the year. Field studies showed higher percentage cover, from 23 to 66%, during February through May. Varying temperature, light intensities and photoperiods were tested. The zygotospores germinated faster at 15°C, and at 25 ,mol m,2·s,1. Growth rate of the conchocelis was affected by temperature rather than by photoperiod. In the three photoperiods tested, growth rate was always higher at 15°C, under 25 to 75 ,mol m,2·s,1, although not significantly different from that at 20° C. Difference between these two temperatures and 5 and 10°C was significant. Conchosporangia formation was higher in 15°C and at short-day, 8:16, Light:Dark and 25 to 75 ,mol m,2·s,1 and was almost non-existent in free floating conditions. Optimal conditions for conchosporangia maturation, 15° C, 8:16, Light:Dark and 5 to 25 ,mol m,2·s,1 also promoted spore release after 18 weeks. Aeration appeared to be crucial for normal blade development. No archeospores were observed. The first findings of the optimal conditions for growth of the gametophyte stage will also be discussed. [source] Trichoderma enzymes promote Fibrobacter succinogenes S85 adhesion to, and degradation of, complex substrates but not pure cellulose,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2004Diego P Morgavi Abstract The effects of an enzyme preparation from Trichoderma longibrachiatum (TE) on adhesion and growth of the fibrolytic rumen bacterium Fibrobacter succinogenes S85 was studied to gain a better understanding of the action of feed enzyme additives on fibre digestion by ruminants. Adhesion experiments were performed on crystalline cellulose, corn silage and alfalfa hay. Adhesion of F succinogenes to cellulose was negatively related to the concentration of TE (p < 0.05). At the highest concentration used, TE reduced adhesion to cellulose from 65 to 39%. For corn silage and alfalfa hay, TE stimulated adhesion at low levels (p < 0.05) but this effect was lost at higher levels. Culture experiments were performed on crystalline cellulose and corn silage. The presence of TE in media containing cellulose failed to increase substrate disappearance or gas production although it increased numbers of non-adherent bacteria (p < 0.05). When corn silage was used, the addition of TE increased NDF disappearance (p < 0.05) at 24 and 48 h (33 and 52% in controls versus 53 and 65% in TE treatments). Growth rate and gas production were also stimulated (p < 0.05). We conclude that, for cellulose, the hydrolytic enzymes in TE obstructed available binding sites decreasing bacterial adherence. Fibrobacter succinogenes digested cellulose efficiently and addition of exogenous cellulases did not further increase substrate disappearance. However, for complex plant substrates, low concentration of TE increased bacterial adhesion and plant (corn) fiber degradation. For the Department of Agriculture and Agri-Food, Government of Canada, © Minister of Public Works and Government Services Canada 2004. Published for SCI by John Wiley & Sons, Ltd. [source] Growth rate constrain morphological divergence when driven by competitionOIKOS, Issue 1 2006Jens Olsson Resource competition has been hypothesized to be important in driving divergence by natural selection. The effect of competition on morphological divergence and plasticity has however rarely been investigated. Since low growth rates might constrain morphological modulation and individual growth rates usually are negatively related to the intensity of competition, there might be a connection between competition, growth rate and morphological divergence. We performed an aquarium experiment with young-of-the-year Eurasian perch (Perca fluviatilis L.) to investigate how individual growth rate affected morphological plasticity induced by contrasting habitat treatments. Furthermore, in a field study of 10 lakes we also related the degree of morphological differentiation between habitats to the intraspecific competitior biomass. In the aquarium experiment we found that morphological plasticity was growth rate dependent in that morphological differentiation between the habitat treatments was confined to high individual growth rates. In the field study we found that morphological differentiation between habitats decreased with increasing intraspecific competitior biomass. Since plasticity is hypothesized to be important in divergence and intraspecific biomass could serve as a proxy for the level of competition, we suggest that our results indicate that morphological divergence might be constrained during periods of intense intraspecific competition due to low growth rates. A possible scenario is that at low growth rates all energy available is used for metabolic maintenance and no surplus energy is therefore available for morphological modulation. [source] Sensitivity of the Early Life Stages of Macroalgae from the Northern Hemisphere to Ultraviolet Radiation,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Michael Y. Roleda The reproductive cells of macroalgae are regarded as the life history stages most susceptible to various environmental stresses, including UV radiation (UVR). UVR is proposed to determine the upper depth distribution limit of macroalgae on the shore. These hypotheses were tested by UV-exposure experiments, using spores and young thalli of the eulittoral Rhodophyceae Mastocarpus stellatus and Chondrus crispus and various sublittoral brown macroalgae (Phaeophyceae) with different depth distribution from Helgoland (German Bight) and Spitsbergen (Arctic). In spores, the degree of UV-induced inhibition of photosynthesis is lower in eulittoral species and higher in sublittoral species. After UV stress, recovery of photosynthetic capacity is faster in eulittoral compared to sublittoral species. DNA damage is lowest while repair of DNA damage is highest in eulittoral compared to sublittoral species. When the negative impact of UVR prevails, spore germination is inhibited. This is observed in deep water kelp species whereas the same UVR doses do not inhibit germination of shallow water kelp species. A potential acclimation mechanism to increase UV tolerance of brown algal spores is the species-specific ability to increase the content of UV-absorbing phlorotannins in response to UV-exposure. Growth rates of young Mastocarpus and Chondrus gametophytes exposed to experimental doses of UVR are not affected while growth rates of all young kelp sporophytes exposed to UVR are significantly lowered. Furthermore, morphological UV damage in Laminaria ochroleuca includes tissue deformation, lesion, blistering and thickening of the meristematic part of the lamina. The sensitivity of young sporophytes to DNA damage is correlated with thallus thickness and their optical characteristics. Growth rate is an integrative parameter of all physiological processes in juvenile plants. UV inhibition of growth may affect the upper distribution depth limit of adult life history stages. Juveniles possess several mechanisms to minimize UVR damage and, hence, are less sensitive but at the expense of growth. The species-specific susceptibility of the early life stages of macroalgae to UVR plays an important role for the determination of zonation patterns and probably also for shaping up community structure. [source] Nonpolar a -plane HVPE GaN: growth and in-plane anisotropic propertiesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005T. Paskova Abstract Nonpolar GaN thick films with [11-20] orientation were grown on [1-102] oriented sapphire by hydride vapour phase epitaxy (HVPE) utilizing reactively sputtered AlN buffers. Growth rate and microstructure of such films were investigated and compared to those in HVPE [0001] oriented GaN thick films. The structural parameters show an angular azimuth dependence implying in-plane non-homogeneity. The lattice parameters and strain components were determined by using plane and edge symmetric measurement geometries. A red shift observed in the near band edge photoluminescence is explained by the specific strain distribution studied independently by X-ray diffraction. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The use of alternative diets to culture juvenile cuttlefish, Sepia officinalis: effects on growth and lipid compositionAQUACULTURE NUTRITION, Issue 3 2010A. FERREIRA Abstract The effects of feeding three natural frozen diets, grass shrimp (Palaemonetes sp.), crayfish (Procambarus clarkii) and fish (Sardina pilchardus) and two semi-humid artificial diets (based on fish or shrimp powder) to the cuttlefish, Sepia officinalis, were analysed. Growth rate and feeding rate [FR; % body weight (BW) day,1] and food conversions (FC, %) were determined. Cuttlefish fed shrimp grew larger (3.8% BW day,1) and had the highest FC, followed by those fed crayfish, and sardine. The highest FR was obtained for cuttlefish fed crayfish (10.5% BW day,1). Although both artificial diets were accepted, none produced growth. Digestive gland-to-body weight ratio (DG/BW ratio) was calculated for animals fed each diet. A positive correlation (r = 0.94) between cuttlefish ingestion FR and DG weight was obtained. Mortality occurred mainly during the last week, and some cannibalism occurred among cuttlefish fed artificial diets. Finally, lipid composition of diets, DG and mantle of each group were analysed. Sardine diet was characterized by high levels of triacylglycerol (TG), whereas the main difference between shrimp and crayfish was the higher n -3/n -6 ratio found in shrimp. Changes in the lipid composition of DG were related to diet, but did not correlate with growth data. A strong loss of TG in the DG of artificial diets groups was notable. No differences in mantle lipid composition among the natural diets were found, but artificial diet groups showed higher contents of neutral lipids in their mantle respect to natural diets. According to results obtained, crayfish (P. clarkii) could be used as an alternative prey for rearing S. officinalis compared with shrimp. Artificial diets showed the worst effects in growth and mortality as well as the stronger influence on DG and mantle lipid composition of cuttlefish. [source] Growth, haematological parameters and tissue lipid peroxidation of soft-shelled turtles, Pelodiscus sinensis, fed diets supplemented with different levels of ferrous sulphateAQUACULTURE NUTRITION, Issue 1 2009J.-H. CHU Abstract Soft-shelled turtles, Pelodiscus sinensis, with an average weight of 5.55 g, were fed diets supplemented with eight levels of ferrous sulphate for 8 weeks. The analysed iron content ranged from 50.8 to 482.9 mg kg,1. Growth rate of turtles fed the control diet with no iron supplementation was the lowest among all dietary groups. Haematological parameters including red blood cell, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration of the turtles fed the control diet were also significantly (P < 0.05) lower relative to the other groups. Thus, dietary iron at 50.8 mg kg,1 (no supplemented iron) was deemed deficient for growth and ineffective at preventing anaemia in juvenile soft-shelled turtle. Whereas, a supplementation of 50 mg kg,1 ferrous sulphate (a total dietary iron of 91.8 mg kg,1) was enough to normalize the haematological values of soft-shelled turtles to the level similar to other iron supplement-fed groups. Within the tested dietary iron range, liver iron content curve-linearly (r2 = 0.99) increased with increasing dietary iron level. Furthermore, thiobarbituric acid-reactive substances in liver tissues of the turtles have also increased when liver iron content increased. The dietary iron requirement of soft-shelled turtle is 120,198 mg kg,1 when ferrous sulphate is used as the source of iron. [source] Complete and partial replacement of Artemia nauplii by Moina micrura during early postlarval culture of white shrimp (Litopenaeus schmitti)AQUACULTURE NUTRITION, Issue 2 2006L. MARTÍN Abstract Growth rate, soluble protein content, osmotic stress and digestive enzyme activity were studied in early Litopenaeus schmitti postlarvae under different feeding regimens, by partially or completely replacing Artemia nauplii with Moina micrura. Growth was significantly higher in the postlarvae fed with a mixture of M. micrura, Artemia nauplii and algae (0.030 mg dry weight (dw) larva,1 day,1, 17.4 ± 2.1% day,1), together with the postlarvae fed on Artemia nauplii and algae (0.027 mg dw larva,1 day,1, 18.3 ± 1.9% day,1). Complete replacement of Artemia nauplii by M. micrura produced the lowest growth rate (0.018 mg dw larva,1 day,1, 14.3 ± 1.6% day,1) and induced the highest protease and , -amylase activities and lower soluble protein contents. No significant difference among the treatments could be detected in postlarval resistance to osmotic stress. Based on the growth results, soluble protein content, enzymatic activity and osmotic stress resistance, we determined that the partial replacement of Artemia nauplii by M. micrura did not affect the growth, the soluble protein content and the nutritional state in the postlarvae of L. schmitti. To our knowledge, this is the first reported use of M.micrura as feed for early postlarvae of L. schmitti. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||