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Lower Growth Rate (lower + growth_rate)
Selected AbstractsKIN-BASED RECOGNITION AND SOCIAL AGGREGATION IN A CILIATEEVOLUTION, Issue 5 2010Alexis S. Chaine Aggregative groups entail costs that must be overcome for the evolution of complex social interactions. Understanding the mechanisms that allow aggregations to form and restrict costs of cheating can provide a resolution to the instability of social evolution. Aggregation in Tetrahymena thermophila is associated with costs of reduced growth and benefits of improved survival through "growth factor" exchange. We investigated what mechanisms contribute to stable cooperative aggregation in the face of potential exploitation by less-cooperative lines using experimental microcosms. We found that kin recognition modulates aggregative behavior to exclude cheaters from social interactions. Long-distance kin recognition across patches modulates social structure by allowing recruitment of kin in aggregative lines and repulsion in asocial lines. Although previous studies have shown a clear benefit to social aggregation at low population densities, we found that social aggregation has very different effects at higher densities. Lower growth rates are a cost of aggregation, but also present potential benefits when restricted to kin aggregations: slow growth and crowd tolerance allow aggregations to form and permit longer persistence on ephemeral resources. Thus in highly dynamic metapopulations, kin recognition plays an important role in the formation and stability of social groups that increase persistence through cooperative consumptive restraint. [source] Currency boards: More than a quick fix?ECONOMIC POLICY, Issue 31 2000Atish R. Ghosh Once a popular colonial monetary arrangement, currency boards fell into disuse as countries gained political independence. But recently, currency boards have made a remarkable come-back. This essay takes a critical look at their performance. Are currency boards really a panacea for achieving low inflation and high growth? Or do they merely provide a ,quick fix' allowing authorities to neglect fundamental reforms and thus fail to yield lasting benefits? We have three major findings. First, the historical track record of currency boards is sterling, with few instances of speculative attacks and virtually no ,involuntary' exits. Countries that did exit from currency boards did so mainly for political, rather than economic reasons, and such exits were usually uneventful. Second, modern currency boards have often been instituted to gain credibility following a period of high or hyperinflation, and in this regard, have been remarkably successful. Countries with currency boards experienced lower inflation and higher (if more volatile) GDP growth compared to both floating regimes and simple pegs. The inflation difference reflects both a lower growth rate of money supply (a ,discipline effect'), and a faster growth of money demand (a ,credibility effect'). The GDP growth effect is significant, but may simply reflect a rebound from depressed levels. Third, case studies reveal the successful introduction of a currency board to be far from trivial, requiring lengthy legal and institutional changes, as well as a broad economic and social consensus for the implied commitment. Moreover, there are thorny issues, as yet untested, regarding possible exits from a currency board. Thus currency boards do not provide easy solutions. But if introduced in the right circumstances, with some built-in flexibility, they can be an important tool for gaining credibility and achieving macroeconomic stabilization. [source] Breeding biology of the White-rumped Swallow Tachycineta leucorrhoa in Buenos Aires Province, ArgentinaIBIS, Issue 1 2007VIVIANA MASSONI We conducted a study of the breeding biology of the White-rumped Swallow Tachycineta leucorrhoa nesting in nestboxes in a flat, farming landscape in Buenos Aires Province, Argentina. White-rumped Swallow nesting attempts were detected from the end of September to mid December, with most clutches laid during October. Birds laid clutches of 4,6 eggs with a mode of five eggs; most broods hatched synchronously (58%), but hatching spread could last up to 4 days. Nestling growth curves adjust well to logistic functions, and at day 15 nestlings attain the asymptotic weight of 21.6 g. Clutch size in White-rumped Swallows declined significantly as the season progressed. In addition, late-season eggs were smaller and late-season nestlings had a shorter nestling period and lower weight at day 15, probably leaving the nest lighter than early-season nestlings. These data suggest that the Swallows would benefit greatly from laying early in the season, which would provide nestlings with better survival prospects. However, both major sources of nest mortality, interspecific competition for nest-sites and nestling mortality during bad weather, decreased through the season. White-rumped Swallows follow the pattern found for other southern species, as it has smaller clutch size, lower growth rate and remains longer at the nest than its Northern Hemisphere congener the Tree Swallow Tachycineta bicolor. [source] The Information Signaling Hypothesis of Dividends: Evidence from Cointegration and Causality TestsJOURNAL OF BUSINESS FINANCE & ACCOUNTING, Issue 3-4 2003Mbodja Mougoué This paper uses cointegration and causality tests to study the temporal behavior of dividends and earnings at the individual firm level. We find that, for a sample of 143 non-utility firms, approximately one-fifth of the firms exhibits a temporal relationship between dividends and earnings that is consistent with the information signaling hypothesis of dividends. In the case of 72 utilities, about a third exhibit dividend policies that are consistent with the signaling notion of dividends. Further examination of firm characteristic differences between signaling and non-signaling firms shows that, in the case of non-utility firms, signaling firms tend to be smaller, have a lower growth rate of total assets, and have a higher leverage ratio. In the case of utilities, we find no major differences in firm characteristics between signaling and non-signaling firms. [source] Demography and population dynamics of Drosera anglica and D. rotundifoliaJOURNAL OF ECOLOGY, Issue 1 2004J.-F. Nordbakken Summary 1We studied demography and population dynamics of the sympatric perennial herbs Drosera anglica and D. rotundifolia on a boreal bog in SE Norway. Dry mass of 2872 D. anglica plants and 2467 D. rotundifolia plants (estimated from field morphological measurements) was used to classify plants into five species-specific size classes. Demographic changes within these two populations were followed from 1995 to 1999, and within segments (quartiles) along the water table gradient and the peat productivity gradient. 2Mortality was strongly size dependent, and varied between years, for both species; it was high for seedlings, low for the smallest mature rosettes and increased again for the largest mature rosettes. The proportion of fertile rosettes increased with increasing rosette size. Fecundity varied considerably between years, but little relative to gradient position. 3Growth rate (,) was > 1, except in the second year, when it fell to 0.572 for D. anglica and 0.627 for D. rotundifolia . For D. anglica small, but significant, differences were found between the two extremities of the water table gradient, and for D. rotundifolia between the second and the uppermost quartile. There was a tendency for D. anglica populations to have a lower growth rate in the most productive sites, whereas D. rotundifolia grew less on both low and high peat productivity. Elasticity analysis showed that stasis and size increase (primarily within mature stages) made major contributions to , for D. anglica in all years. 4The variance in population growth rate (var ,) was high between years, and higher for D. anglica than for D. rotundifolia , while the variance between quartiles along the two main gradients was low. Life-table response experiment (LTRE) analyses revealed that for both species, differences in probabilities of transitions within mature stages, and in growth to larger stages, contributed most to var ,. 5The effects of global warming are uncertain: drier growing seasons would affect Drosera populations negatively, while initially positive responses to a wetter climate may be balanced by competition from increased Sphagnum growth. [source] Feeding ecology and growth of neonate and juvenile blacktip sharks Carcharhinus limbatus in the Timbalier,Terrebone Bay complex, LA, U.S.A.JOURNAL OF FISH BIOLOGY, Issue 3 2008K. P. Barry Stomach contents and vertebrae from neonate and juvenile blacktip sharks Carcharhinus limbatus (n= 334) were examined to describe their diet, feeding patterns and growth within the Timbalier,Terrebone Bay complex, LA, U.S.A. In the study area, both neonate and juvenile C. limbatus feed primarily on gulf menhaden Brevoortia patronus. However, based on the index of relative importance (IRI), gulf menhaden constituted a larger portion of the diet of neonates (84·05 %IRI) than for juveniles (47·91 %IRI). An increase in the index of relative fullness between the afternoon and dusk time intervals and a large decrease in the percentage of empty stomachs between the night and early morning time intervals suggested that these fish exhibited a diel feeding pattern with crepuscular periods being the times of highest feeding activity. A higher percentage of empty stomachs (neonates 68% and juveniles 39%) and a significantly lower growth rate (age 0+ year C. limbatus, 0·62 mm day,1; age 1+ year fish, 0·89 mm day,1) could indicate that neonate C. limbatus are less efficient predators than older conspecifics. [source] Knockout of major leaf ferredoxin reveals new redox-regulatory adaptations in Arabidopsis thalianaPHYSIOLOGIA PLANTARUM, Issue 3 2008Ingo Voss Ferredoxins are the major distributors for electrons to the various acceptor systems in plastids. In green tissues, ferredoxins are reduced by photosynthetic electron flow in the light, while in heterotrophic tissues, nicotinamide adenine dinucleotide (reduced) (NADPH) generated in the oxidative pentose-phosphate pathway (OPP) is the reductant. We have used a Ds -T-DNA insertion line of Arabidopsis thaliana for the gene encoding the major leaf ferredoxin (Fd2, At1g60950) to create a situation of high electron pressure in the thylakoids. Although these plants (Fd2-KO) possess only the minor fraction of leaf Fd1 (At1g10960), they grow photoautotrophically on soil, but with a lower growth rate and less chlorophyll. The more oxidized conditions in the stroma due to the formation of reactive oxygen species are causing a re-adjustment of the redox state in these plants that helps them to survive even under high light. Redox homeostasis is achieved by regulation at both, the post-translational and the transcriptional level. Over-reduction of the electron transport chain leads to increased transcription of the malate-valve enzyme NADP-malate dehydrogenase (MDH), and the oxidized stroma leads to an increased transcription of the OPP enzyme glucose-6-P dehydrogenase. In isolated spinach chloroplasts, oxidized conditions give rise to a decreased activation state of NADP-MDH and an activation of glucose-6-P dehydrogenase even in the light. In Fd2-KO plants, NADPH-requiring antioxidant systems are upregulated. These adjustments must be caused by plastid signals, and they prevent oxidative damage under rather severe conditions. [source] Protein requirements of Nile tilapia (Oreochromis niloticus) fry cultured at different salinitiesAQUACULTURE RESEARCH, Issue 8 2010Edvino Larumbe-Morán Abstract Effect of isolipidic (62.7 ± 5.0 g kg,1) diets with protein levels of 204.6 (T20), 302.3 (T30), 424.6 (T40) or 511.0 g kg,1 (T50) on growth and survival in Nile tilapia (Oreochromis niloticus Linnaeus 1758) fry cultured for 70 days at one of four salinities (0, 15, 20 and 25 g L,1) was evaluated. A bifactorial (4 × 4) design was used with 16 treatments run in triplicate and 20 fry (0.25 ± 0.04 g) per replicate under semi-controlled conditions. Four independent, recirculating systems (one per salinity level) were used, each one with 12 circular tanks (70 L capacity), filters and constant aeration. The different salinities had no significant effect on growth. Weight gain improved significantly as dietary protein content increased, although organisms fed the T50 diet had a lower growth rate. Survival was highest (98.33%) in the T50/15 (protein/salinity levels) treatment and lowest (71.0%) in the T20/20 treatment, with no pattern caused by the variables. The T40/25, T40/20 and T50/0 treatments produced the most efficient growth and feed utilization values while the T20 treatments at all the salinities resulted with the lowest performance. With the exception of the T50 treatments, a non-significant tendency to increased weight gain was observed as water salinity increased, suggesting that the salinity of the culture environment does not influence dietary protein requirements in Nile tilapia O. niloticus fry. [source] Morphometric changes in a strain of the lineage ,Nevada', belonging to the Brachionus plicatilis (Rotifera) complexAQUACULTURE RESEARCH, Issue 8 2009Venetia Kostopoulou Abstract The rotifer Brachionus plicatilis is an important component of aquaculture as a larval feed. Its taxonomic status has been recently re-defined as a species complex, consisting of at least 14 new species/lineages. This study deals with the lineage Brachionus,Nevada', which has been shown to occur in European hatcheries. A strain of B. ,Nevada' was mass cultured using two commonly applied feeding regimes and analysed in terms of its morphometry. A new formula was proposed for the calculation of volume, which can be used as an index of adequacy of rotifers as feed for fish larvae. The results were related to life cycle parameters. The pre-reproductive and reproductive phases were divided into distinct size groups. Differences were also found between the two diets in morphometry and demography. Rotifers of a larger size (yeast-based diet) showed a lower growth rate and a longer reproductive period, lifespan and mean generation time compared with smaller-sized rotifers (Culture Selco® -based diet). In terms of lorica length, the present study's strain of B. ,Nevada' (238.5 ,m) was intermediate between values reported for Brachionus ibericus (193.5 ,m) and B. plicatilis sensu stricto (299 ,m). [source] Fertilization, hatching, survival and growth rates in reciprocal crosses of two strains of an African catfish Heterobranchus longifilis Valenciennes 1840 under controlled hatchery conditionsAQUACULTURE RESEARCH, Issue 7 2000D Nguenga A diallelic cross between two strains [Layo strain (LS) and Noun strain (NS)] of the catfish Heterobranchus longifilis Valenciennes was carried out under controlled hatchery conditions to estimate their reproductive performance and aquaculture potential in terms of fertilizability, hatchability, survival, growth and heterosis. The average fertilization rate of all mating groups was as high as 90.4%, the fertilization rate of the purebred NS (95.2%) being significantly higher than that of the purebred LS or the reciprocal crosses (P <,0.05). The average hatching rate of all genetic groups was as high as 84.7%, the hatching rate of NS (89.4%) being significantly higher than that of the purebred LS or the reciprocal crosses (P <,0.05). The mean survival rate of all crosses from hatching up to the onset of exogenous feeding stood at 94.2%, without showing a significant difference (P >,0.05) between the crosses. During the larval rearing period, which extended from the onset of exogenous feeding up to 15 days of age, NS displayed a significantly lower growth rate (P <,0.001) than that of the purebred LS and their reciprocal hybrids. There was no significant difference (P >,0.05) in survival rate (mean 84.7%) between the four crosses at the end of the larval rearing period. During the juvenile rearing phase, the mean growth performance of all crossbreds was similar to that of the purebred LS and significantly different from that of the purebred NS (P <,0.001). The final individual weights attained by LS, NS, LS × NS and NS × LS were 3.31, 0.71, 3.97 and 3.66 g respectively. The increase in weight attained by the fast-growing crossbred LS × NS was 562.2%, 20.4% and 8.7% more than that of NS, LS and NS × LS respectively. The survival rate of NS (57.1%) was significantly lower (P <,0.001) than that of all the rest of the crosses. The crossbreds displayed about 15.1% heterosis in mean body weight relative to the fast-growing purebred LS. It was concluded that cross-breeding of H. longifilis strains could be advantageous because of the hybrid vigour in the progeny. [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] Experimental reduction of incubation temperature affects both nestling and adult blue tits Cyanistes caeruleusJOURNAL OF AVIAN BIOLOGY, Issue 5 2008Johan F. Nilsson Incubation was for a long time considered to be a period of decreased activity and low cost for parents. It was therefore ignored as a potential factor affecting life-history trade-offs in birds. Lately this view has started to change, and studies now show that there might be considerable costs connected to incubation. We experimentally reduced the nest temperature during incubation in blue tits Cyanistes caeruleus, thus increasing the energetic cost of incubation, to test the importance of incubation as a component of reproductive costs and for nestling quality. While most other studies use brood size manipulation to manipulate reproductive costs, we were able to separate treatment effects acting during the incubation period from those acting on later reproductive performance by applying a cross-foster design. We were also able to isolate the effects of decreased incubation temperature on the nestlings from treatment effects acting on incubating females. We found no experimental effect on the length of the incubation period or on hatching success. The lower temperature during incubation, however, caused lower growth rates in nestlings and reduced chick rearing capacity in adults. We conclude that incubation is a costly period, with the potential to affect both the trade-off between current and future reproduction and the one between parental effort and offspring quality within the current breeding attempt. [source] Dimorphic growth patterns and sex-specific reaction norms in the butterfly Lycaena hippothoe sumadiensisJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2001K. Fischer Directly developing larvae of the butterfly Lycaena hippothoe sumadiensis exhibited two growth strategies with one cohort passing four larval instars at high growth rates, and the other five instars at lower growth rates. The 4-instar-cohort displayed decreased development times, in combination with slightly reduced pupal and adult weights. In addition to adjustment of growth rate, omitting a larval instar may comprise a further mechanism to decrease development time when needed. Using the 4-instar-cohort, sex-related differences in reaction norms were investigated over a temperature gradient. At high temperatures, protandrous males showed early emergence at a reduced size, whereas weight of females remained similar throughout. These differences suggest that large size is more important for female than for male fitness. The pattern is similar to that previously reported for alpine L. tityrus, indicating that sex-specific reaction norms might be widespread in species living under severe time constraints. [source] Phenotypic plasticity of anuran larvae: environmental variables influence body shape and oral morphology in Rana temporaria tadpolesJOURNAL OF ZOOLOGY, Issue 2 2002Miguel Vences Abstract Environmental variables shaped the morphology of tadpoles of the common frog, Rana temporaria, in various ways at the Pyrenean locality Circo de Piedrafita. Examining only specimens in similar developmental stages, those from small ponds (with higher temperature and higher tadpole density) had lower growth rates, lower relative tail height, lower relative body width and fewer labial keratodonts and keratodont rows. The variation in keratodonts may have been caused by heterochrony related to the slower growth rate. The number of lingual papillae also differed between ponds but was not related to pond size. Higher predator densities caused a higher percentage of damaged tails and a lower relative tail length in specimens with apparently intact tails, probably as a result of incomplete regeneration after mutilations earlier in development. [source] Maerl growth, carbonate production rates and accumulation rates in the ne atlanticAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2003Dan Bosence Abstract 1.Accumulations of maerl occur widely in ocean facing coastal waters (<20,30 m depth) of the northeast Atlantic, that are sheltered from the direct SW approach of storm waves and have little terrigenous sediment supply. 2.The different methods that have been used to assess the rate of formation of cool temperate, coralline algal gravels (maerl) are outlined. 3.Formation rates of maerl may be expressed as short-term, branch growth rates (mm yr,1), as calcium carbonate production rates (g CaCO3 m,2 yr,1), or as longer-term accumulation rates (m kyr,1=m 1000 yr,1). 4.Branch growth rates of the free living, branching coralline algae that form maerl in northwest Spain and western Ireland vary from 0.1 to 1.0 mm yr,1. Rates from Norway are either 0.05,0.15 or up to 1.0 mm yr,1. 5.Production rates vary from 30,250 g CaCO3 m,2 yr,1 in western Ireland, 876 g CaCO3 m,2 yr,1 in northwest France and 90,143 or 895,1423 g CaCO3 m,2 yr,1 in Norway. 6.Accumulation rates vary from 0.08 m ky,1 in Orkney to 0.5 m ky,1 in Cornwall, to 0.8,1.4 m kyr,1 in Norway. 7.These production and accumulation rates are similar to the lower end of such rates from tropical coral reef environments. This is achieved by high standing crops that compensate for the lower growth rates of the temperate algae. Although rapid on a geological time-scale these accumulation rates are far too low for the maerl to be regarded as a sustainable resource for extraction for agricultural and industrial use. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||||||||