Individual Variation In Growth Research Articles

Differential responses to defoliation frequency in little bluestem (Schizachyrium scoparium) in tallgrass prairie: implications for herbivory tolerance and avoidance

Plant responses to herbivory are complex. In grasses, relative growth rate (RGR), seed, and vegetative reproduction, resource allocation, and architecture vary differentially and often nonlinearly with grazing intensity. High grazing tolerance may be achieved through compensatory photosynthesis and leaf growth, or through demographic mechanisms such as activation of a belowground dormant bud bank. This study assessed the relationship between grazing frequency and responses of Schizachyrium scoparium (little bluestem) in a tallgrass prairie, and examined the roles of tiller growth, reproduction, and bud (meristem) populations in its persistence under grazing. Genets were subjected to varying simulated grazing frequencies for a period of 2 years. Strong differential responses were observed among plant traits. RGR, biomass, and flowering showed strong nonlinear reductions in response to increasing clipping frequency, with no evidence of threshold effects. However, meristem density was unaffected, and plants maintained a large bud bank across all clipping treatments. Tiller natality decreased initially, but increased with >4 clippings, suggesting that declines in tiller RGR are partially offset by increasing tiller natality, and that variation in genet size is driven more by demography than by variation in individual tiller growth. Increased grazing frequency also resulted in differential activation of buds at different positions (emerging within vs. outside the subtending leaf sheath), explaining the shift to a more prostrate growth form observed in many caespitose grasses under persistent grazing. Thus, although this grass species lacks the capacity for compensatory foliage re-growth, the maintenance of a large dormant bud bank and the differential activation of buds in different positions contribute to its grazing tolerance and avoidance, respectively, and its long-term persistence in grazed grasslands.

Response of non-native lake trout (Salvelinus namaycush) to 15 years of harvest in Yellowstone Lake, Yellowstone National Park

Introduced lake trout ( Salvelinus namaycush ) threaten to extirpate native Yellowstone cutthroat trout ( Oncorhynchus clarkii bouvieri ) in the 34 000 ha Yellowstone Lake in Yellowstone National Park, USA. Suppression (and eventual eradication) of the lake trout population is deemed necessary for the conservation of Yellowstone cutthroat trout. A US National Park Service gill-netting program removed nearly 450 000 lake trout from Yellowstone Lake from 1995 through 2009. We examined temporal variation in individual growth, body condition, length and age at maturity, fecundity, mortality, and population models to assess the efficacy of the lake trout suppression program. Population metrics did not indicate overharvest despite more than a decade of fish removal. The current rate of population growth is positive; however, it is lower than it would be in the absence of lake trout suppression. Fishing effort needs to increase above observed levels to reduce population growth rate below replacement. Additionally, high sensitivity of population growth rate to reproductive vital rates indicates that increasing fishing mortality for sexually mature lake trout may increase the effectiveness of suppression. Lake trout suppression in Yellowstone Lake illustrates the complexities of trying to remove an apex predator to restore a relatively large remote lentic ecosystem with a simple fish assemblage.

The relation between teacher input and lexical growth of preschoolers

ABSTRACTThe present study examined the growth of receptive lexical skills in preschoolers over an academic year in relation to teacher speech. The participating students were English language learners and their monolingual English-speaking peers from the same classrooms. The measures of teacher input included indicators of the amount of speech (total number of words), lexical richness (number of different word types), and structural complexity (number of words per utterance). These measures were based on a speech sample collected during a classroom observation. For English language learners, vocabulary growth was positively related to the total number of words produced by the teacher, but negatively related to the number of words per utterance. For monolingual speakers, vocabulary growth was positively related to the number of word types produced by the teacher. The findings underscore the importance of considering different aspects of verbal input for understanding individual variability in language growth of preschool students.

Individual variation in growth in sea cucumber Apostichopus japonicus (Selenck) housed individually

The exceptionally large individual growth variation has been previously recognized in several sea cucumber cohorts. However, there is a lack of information regarding the mechanism of such individual differences. In this study, the sea cucumber Apostichopus japonicus (Selenka) was reared individually in order to eliminate possible effects of social interaction, stocking density, etc. The results showed that there were substantial differences in growth among the sea cucumber individuals during the 100-day experiment. The special growth rate of the sea cucumber individuals differed by up to three folds (from 0.40% to 1.01%), and the coefficient of variation in body weight increased from 12.04% to 40.51%. The final wet body weight, food intake and food conversion efficiency for each sea cucumber were generally positively correlated with their initial wet body weight (P<0.05). Energy budget of the animals showed that the food energy spent on respiration was much greater (about four folds) but energy deposited for growth was much less for (initially) smaller than for larger A. japonicus. The present result implies that there are obvious genetic differences among the sea cucumber individuals, largely accounting for the individual growth variation of the cohort sea cucumber. These results will provide some basic data for promoting selective breeding and farming of the sea cucumber.

Temperature and growth effects on otolith elemental chemistry of larval Pacific cod, Gadus macrocephalus

Variation in otolith elemental composition is used to investigate movements of teleost fishes based on observations that otolith elemental composition reflects variation in water chemistry. Various environmental (e.g., temperature, salinity, and water concentration) and biological (e.g., growth, diet, and ontogeny) factors can influence otolith elemental incorporation although the relative influence of these factors remains poorly understood for most species. Therefore, we examined the effects of temperature and growth rate on the otolith elemental composition of larval Pacific cod, Gadus macrocephalus. The larvae were progeny of wild Pacific cod collected from spawning grounds near Kodiak Island, Alaska. Immediately after hatching, larvae were acclimated to 2°C, 5°C, and 8°C and reared for 38–51 days. Otolith concentrations of Li, Mg, Ca, Mn, Zn, Sr, and Ba were measured using laser ablation-inductively coupled plasma mass spectrometry. Li and Zn otolith concentrations were near detection limits and excluded from subsequent analyses. The effects of temperature on otolith partition coefficients (DMe) varied among elements. DMg showed no relationship with temperature whereas DSr and DBa decreased with increasing temperature. It is possible that, for larval Pacific cod, kinetic effects are more important in the incorporation of Sr and Ba whereas metabolic effects may play a larger role in the incorporation of Mg. There was no evidence for an effect of somatic growth rate or otolith precipitation rate on DMe for any of the elements, which indicates that individual growth variation is unlikely to lead to misinterpretation of field-collected data. Understanding variable relationships among otolith elemental signatures, environmental conditions, and fish physiology can improve the accuracy of interpretations of field data, particularly in marine systems where spatial variation in element concentrations are typically lower than freshwater environments.

Incorporating temporal variation in the growth of red abalone (Haliotis rufescens) using hierarchical Bayesian growth models

Many marine species exhibit temporal variation in individual growth. Yearly variation in growth has been identified for red abalone ( Haliotis rufescens ) in southern California, USA, but has not been previously incorporated into growth models. In this study, Bayesian hierarchical models were developed to describe variability in growth rates for the Johnsons Lee red abalone population. Although the Bayesian hierarchical modeling estimates are close to estimates of the nonhierarchical highly parameterized model that assigns an estimate of parameters to each data period when the sample sizes are high, the hyperparameters in the hierarchical model are more useful in incorporating the temporal variability into the stock assessment. By ignoring temporal variability, confidence intervals of the estimates of growth can be unrealistically narrow, possibly leading to bias when these models are used for developing biological reference points such as F0.1, Fmax, or Fx%. The use of a Bayesian hierarchical approach is generally suggested for future growth modeling and for per-recruitment models that include growth when determining precautionary management decisions.

Individual growth pattern and variability in Serranus scriba: a Bayesian analysis

Abstract Alós, J., Palmer, M., Balle, S., Grau, A. M., and Morales-Nin, B. 2010. Individual growth pattern and variability in Serranus scriba: a Bayesian analysis. – ICES Journal of Marine Science, 67: 502–512. Variability in growth patterns at an individual level in Serranus scriba is described using a Bayesian approach for a generalized von Bertalanffy growth model that accommodates one change in growth rate at a specific point during the lifespan. The approach enables individual growth curves to be inferred, even in a species with a relatively short lifespan and no commercial value, i.e. limited sample sizes available, but potentially endangered by recreational fishing. The change in growth rate may be the result of differing allocation of energy between reproductive and somatic activities at different ages. Overall, the approach presented provides adequate input for future implementation of population dynamics models that take into account individual variability, e.g. individual-based models, even for species for which limited data are available.

Intra-specific effects of sea cucumber (Apostichopus japonicus) with reference to stocking density and body size

The present studies deal with the intra-specific effects of sea cucumber Apostichopus japonicus with unlimited food resources, especially the effects of stocking density on growth variation of the animal and energetic changes of small individuals under the stress of large individuals. The results showed that with the initial body weight of 5.12±0.09–6.11±0.26 g of sea cucumber among the densities of 5, 10, 20, 30, 40 and 50 ind./100 L, the density of 20 ind./100 L was the optimum stocking density because of its highest specific growth rate, crude protein content and crude lipid content in tissue. Individual growth variation of A. japonicus increased with the increase of stocking densities, whereas no significant differences in variation were found when the density was over 30 ind./100 L (P>0.05). The low-weight individuals under the stress of heavy-weight individuals exhibited obvious changes in energetics, such as lower ingestion rate, lower energy deposited as growth but higher respiration and excretion. The coefficient of variation in growth of the animals was over 70% due to the simultaneous action of aggression and maybe a factor of chemical mediator, and led to significant changes in the energetics of small-sized individuals.

Mandibular growth during adolescence.

To evaluate the mandibular growth of whites according to Fishman's method. Eighty-five subjects, 9 to 18 years of age, were selected from the files of the Department of Orthodontics, Pontificia Universidade Catolica do Rio Grande do Sul, Porto Alegre, Brazil. Patients were evaluated at two time points. At T1, they had a lateral head film and a hand-wrist radiograph and at T2, a lateral head film. The interval between T1 and T2 was 5 to 24 months. Subjects presented a Class I or II skeletal pattern and were divided into three groups according to Fishman's method: group I, in an accelerating growth velocity phase; group II, in peak of growth velocity phase; and group III, in decelerating growth velocity phase. The cephalograms were manually traced and cephalometric points digitalized into DentoFacial Planner Plus 2.0. The absolute growth amount was adjusted to obtain an annual growth rate (mm/y). The annual growth rate was compared between sexes, between individuals with Class I or II skeletal patterns, and among the three groups. Mandibular annual growth rate in puberty was 2.16 mm for the mandibular body length, 3.16 mm for the ramus height, and 4.31 mm for the mandibular length. The results did not show significant differences between sexes, skeletal patterns, and groups, although there was a tendency for growth acceleration in group II. There is great individual variation in mandibular linear growth.

Progress in modelling herring populations: an individual-based model of growth

Abstract Russo, T., Mariani, S., Baldi, P., Parisi, A., Magnifico, G., Clausen, L. W., and Cataudella, S. 2009. Progress in modelling herring populations: an individual-based model of growth. – ICES Journal of Marine Science, 66: 1718–1725. Stock assessment may gain from taking into account individual variations in growth, because size is a key predictor of survival and reproduction. In trying to understand patterns in empirical observations, a major challenge is to model the changes in the size distribution of a cohort with age. We introduce an individual-based growth model that is founded on the use of a stochastic class of processes called subordinators. This modelling approach has several desirable features, because it (i) can take account of both individual and environmental sources of random variations, (ii) has the property of letting size increase monotonically, and (iii) ensures that the mean size-at-age follows the widely accepted von Bertalanffy equation. The parameterization of the model is tested on two Atlantic herring (Clupea harengus) datasets collected from the stocks of North Sea autumn spawners (ICES Divisions IVa, IVb, and IVc) and western Baltic spring spawners (ICES Subarea III). The size distributions obtained from the subordinator model largely match the observed size distributions, suggesting that this approach might be successfully implemented to support the assessment of commercial fish stocks, such as when modelling of size variability is required.

Spatial and Temporal Variability in Growth of Hawaiian Spiny Lobsters in the Northwestern Hawaiian Islands

AbstractGrowth rates were estimated for recaptured Hawaiian spiny lobsters Panulirus marginatus tagged between 2002 and 2007 at Necker Island (23°30′N; 164°35′W), Gardner Pinnacles (25°00′N; 168°50′W), and Maro Reef (25°30′N; 170°45′W) in the Northwestern Hawaiian Islands (NWHI). The location and year‐specific nature of the tag–recapture cruises enabled investigation of spatial and temporal variability in growth. Mean growth rates, estimated by using the von Bertalanffy and Schnute growth models and fitted via a maximum likelihood technique, differed between sexes and particularly among locations and years. Male lobster growth rates at Necker Island were, in general, one‐third those at Gardner Pinnacles and one‐half those at Maro Reef. Female lobsters exhibited the same pattern with less‐pronounced differences. Maro Reef lobsters exhibited several abrupt, significant growth reductions among years, while Necker Island lobster growth rates increased significantly from 2004 to 2005. Model results also indicated substantial individual variability in growth. Neither density nor temperature could account for the differences in growth rates. No palinurid species studied to date has shown such spatial variability in growth, and only one panilurid species has exhibited similar variability on a temporal scale. Recognition of and accounting for the mean and individual variability in a life history trait of this endemic species will result in more accurate stock assessments and, ultimately, a better understanding of lobster dynamics and the NWHI coral reef ecosystem.

Temperature effects on otolith pattern formation in Atlantic cod Gadus morhua

The effect of food intake and temperature on otolith macrostructure and microstructure was examined experimentally in Atlantic cod Gadus morhua. Daily increment formation was validated and otolith accretion rate and optical density quantified using image analysis. Two‐week periods of starvation had no discernable effect on otolith increment width or optical density, despite having negative effects on somatic growth. In contrast, temperature had a strong positive effect on otolith accretion rate and clear effects on optical density with the otolith becoming more translucent at higher temperatures. Somatic growth, otolith accretion and otolith optical density each had a significantly different response curve to temperature. No relationship was detected between individual somatic growth rates and the accretion rate or optical properties of the otolith. The experimental manipulation of temperature‐induced otolith patterns similar to the ‘false ring’ secondary structures sometimes observed in the otoliths of wild fish. The results suggest that otolith pattern arises from a combination of temperature and seasonal effects, but not directly from individual variation in somatic growth.

Individual sensitivity of Larix sibirica L. in open woodland of the Shira forest-steppe

Some indices of individual variability in annual growth of Siberian larch in open woodlands of Khakassia are compared. In the Shira forest-steppe the Siberian larch exhibits high sensitivity of annual growth and diverse responses to changes in vegetative conditions. Stabilizing selection maintains dominance of trees with moderately sensitive annual growth. Such trees are the most vital. It has been shown that the adaptive norm of population’s response and the individual variability of annual growth positively correlate with the total annual precipitation. The sensitivity index of annual growth is a better indicator of the genetic structure of the population than the coefficient of variability of annual growth indices.

Chemogenetic fingerprinting by analysis of cellular growth dynamics

BackgroundA fundamental goal in chemical biology is the elucidation of on- and off-target effects of drugs and biocides. To this aim chemogenetic screens that quantify drug induced changes in cellular fitness, typically taken as changes in composite growth, is commonly applied.ResultsUsing the model organism Saccharomyces cerevisiae we here report that resolving cellular growth dynamics into its individual components, growth lag, growth rate and growth efficiency, increases the predictive power of chemogenetic screens. Both in terms of drug-drug and gene-drug interactions did the individual growth variables capture distinct and only partially overlapping aspects of cell physiology. In fact, the impact on cellular growth dynamics represented functionally distinct chemical fingerprints.DiscussionOur findings suggest that the resolution and quantification of all facets of growth increases the informational and interpretational output of chemogenetic screening. Hence, by facilitating a physiologically more complete analysis of gene-drug and drug-drug interactions the here reported results may simplify the assignment of mode-of-action to orphan bioactive compounds.

Catch-and-release and size limit regulations for blue, white, and striped marlin: the role of postrelease survival in effective policy design

Catch-and-release fishing as a management and conservation tool for billfish (family Istiophoridae) is practiced in many recreational fisheries, and mandatory release of billfish has been implemented for some commercial fisheries. Inherent in these approaches is the observation that survival of released fish is greater than those that are landed. Recent studies using pop-up satellite tags have begun to quantify postrelease survival rates for billfish, yet the efficacy of management measures that require some or all billfish to be released have not been evaluated. Using an age- and size-structured population model that accounts for individual variability in growth, we simulated the effects of postrelease mortality on yield, risk of recruitment overfishing, efficiency (i.e., ratio of harvest to postrelease mortality), and probability of catching trophy-sized individuals for three marlin species. Regulations such as size limits, catch-and-release, and mandatory release are likely to provide some benefit to billfish populations, but our results show that the effectiveness of these strategies is reduced when release survival is less than 100%. The management approaches most likely to benefit billfish populations are ones that focus on maximizing postrelease survival in the recreational fishery and minimize the billfish catch in commercial fisheries.

Work compatibility and musculoskeletal disorders in the construction industry

AbstractThe aim of this study was to measure the work compatibility of the different work‐related variables (physical and psychosocial) using the Demand–Energizer Instrument (DEI) and to determine their association with both musculoskeletal disorders and stress symptoms. In recent years, there has been increasing evidence that psychosocial factors play an important role in the development of musculoskeletal disorders. The study group consisted of 147 active construction workers. Data were collected by means of a questionnaire. The association between the exposure variables (work energizers and work compatibility) and outcome variables was determined using a multivariate logistic regression model with backward elimination of insignificant variables. There was a significantly high correlation between the demand and energizer aspects of the different work‐related variables. Three variables were positively associated with musculoskeletal/stress symptoms (protective effect), seven were negatively associated (hazardous effect), and two demonstrated both effects. When both demands and energizers were combined, the highest work compatibility was achieved in individual growth, economic, and social variables. The results of a factor analysis indicated that four work compatibility variables (work environment, physical task, performance, and job satisfaction) were significantly associated with musculoskeletal/stress symptoms. In the complex web of the human‐at‐work system, the work compatibility model significantly identified those work‐related variables that were associated with musculoskeletal/stress symptoms. Psychosocial factors play a significant role in the construction industry. A possible application of this research can be the use of the new tool in identifying priority areas for future intervention strategies. © 2008 Wiley Periodicals, Inc.

Individual variation affects departure rate from the natal pond in an ephemeral pond-breeding anuran

Frogs exhibit extreme plasticity and individual variation in growth and behavior during metamorphosis, driven by interactions of intrinsic state factors and extrinsic environmental factors. In northern red-legged frogs ( Rana aurora Baird and Girard, 1852), we studied the timing of departure from the natal pond as it relates to date and size of individuals at metamorphosis in the context of environmental uncertainty. To affect body size at metamorphosis, we manipulated food availability during the larval stage for a sample (317) of 1045 uniquely marked individuals and released them at their natal ponds as newly metamorphosed frogs. We recaptured 34% of marked frogs in pitfall traps as they departed and related the timing of their initial terrestrial movements to individual properties using a time-to-event model. Median age at first capture was 4 and 9 days postmetamorphosis at two sites. The rate of departure was positively related to body size and to date of metamorphosis. Departure rate was strongly negatively related to time elapsed since rainfall, and this effect was diminished for smaller and later metamorphosing frogs. Individual variation in metamorphic traits thus affects individuals’ responses to environmental variability, supporting a behavioral link with variation in survival associated with these same metamorphic traits.

Phonological Awareness, Vocabulary, and Word Reading in Children Who Use Cochlear Implants: Does Age of Implantation Explain Individual Variability in Performance Outcomes and Growth?

The phonological awareness (PA), vocabulary, and word reading abilities of 19 children with cochlear implants (CI) were assessed. Nine children had an implant early (between 2 and 3.6 years) and 10 had an implant later (between 5 and 7 years). Participants were tested twice over a 12-month period on syllable, rhyme, and phoneme awareness (see James et al., 2005). Performance of CI users was compared against younger hearing children matched for reading level. Two standardized assessments of vocabulary and single word reading were administered. As a group, the children fitted early had better performance outcomes on PA, vocabulary, and reading compared to hearing benchmark groups. The early group had significant growth on rhyme awareness, whereas the late group showed no significant gains in PA over time. There was wide individual variation in performance and growth in the CI users. Two participants with the best overall development were both fitted with an implant late in childhood.

Laboratory Culture of the Oriental Lancelet Branchiostoma belcheri

To overcome difficulties in getting research materials of cephalochordate lancelets, which has severely hampered experimental studies of this animal, we have attempted to establish a culture system in the laboratory. Adult animals collected from the wild were maintained in 2.5-L plastic containers filled with natural seawater without sand substratum. They were fed daily with unicellular algae. About 25% of the animals collected in 2003, 2004, and 2005 developed gonads in our culture system. Some of the sexually mature animals collected in the breeding seasons in 2005 and 2006 spawned spontaneously in the plastic containers of this system. Broods obtained in 2005 were maintained longer than a year in a glass tank without sand substratum. The progeny born in the laboratory showed great individual variation in growth but metamorphosed normally, and some of them started to develop gonads around 10 months after fertilization. Our mass culture methods for both adults and their progeny made daily observation possible and allowed the constant spawning of animals collected from the wild, at least in the summer season. Our culture method saves labor in maintenance and is easily set up without any specific demands except for running seawater, though still required to better survival rate and spawning control. Lancelet populations maintained in the laboratory can promote studies on these animals across disciplines and especially contribute to elucidation of the evolutionary history of chordates.

Consequences of assuming an incorrect error structure in von Bertalanffy growth models: a simulation study

The underlying sources of growth variability in a population cannot generally be known, so when modelling growth it is important to understand the consequences of assuming an incorrect error structure. In this study, four error models for a von Bertalanffy growth curve with asymptotic length parameter L∞ and growth rate parameter k are considered. Simulations are carried out in which data are generated according to one of the models and fitted assuming each of the models to be true. This is done for two types of data: direct age–length and tag–recapture. For direct age–length data, the consequences of not accounting for individual growth variability, or assuming the wrong source of variability, are minor, even when individual variability is high or data coverage is poor. For tag–recapture data, some substantial biases in growth estimates can arise when individual variability exists but is not accounted for. Importantly, however, incorporating variability in just one parameter (be it L∞ or k), even if the variability truly stems from the other or both parameters, generally leads to much smaller biases than assuming no individual variability. Often the alternative models cannot be distinguished using standard model selection procedures, so caution is warranted in using model selection to draw inferences about underlying sources of growth variability.