Mass Growth Rate Research Articles

Capital vs. income‐dependent optimal birth date in two North American ungulates

AbstractPhenotypic plasticity in reproductive traits is of theoretical and applied interest as one avenue by which organisms might maintain an optimal annual reproductive routine in the face of cyclic and/or directional change in environmental conditions. We used long‐term, individual‐based data from parapatric populations of bighorn sheep (Ovis canadensis canadensis) and pronghorn (Antilocapra americana) to evaluate plasticity in breeding date, gestation duration, birth date, birth mass, and fetal growth rate in response to inter‐annual (cyclic) variation in indices of maternal energy income and expense. Traits in both species responded plastically to variation in maternal energy balance. However, despite nearly identical climate and similar vegetative habitat, plasticity was expressed in fundamentally different ways in the study species. Variation in bighorn birth date was primarily due to plasticity in breeding date, whereas variation in pronghorn birth date was primarily due to variation in gestation duration. Across traits, bighorn plastic responses were more consistent with explanations that invoked periodic energy surplus as the basis for plasticity, whereas pronghorn plastic responses were more consistent with explanations that invoked periodic energy deficiency. Later birth date was associated with increased fetal growth rate in bighorn but decreased fetal growth rate in pronghorn. Finally, we detected strong directional selection for early birth among bighorn mothers but found no evidence of selection on pronghorn birth date. Collectively, our results indicate markedly different maternal tactics for timing birth. Bighorn mothers appeared to use stored energy to subsidize the cost of birth prior to the local environmental optimum in an energy‐mediated competition with other females to minimize birth order rank. Pronghorn mothers, committed to high levels of energy allocation to offspring and subject therefore to frequent energy deficiency, timed birth conservatively to more closely match peak reproductive expenditure with peak energy income at the local environmental optimum.

CCK1, a PMK1-type MAP kinase is required for hyphal growth, pigmentation, conidiation, enzyme activity, osmotic stress response, and pathogenicity in Corynespora cassiicola

Corynespora cassiicola is a fungal pathogen causing Corynespora Leaf Fall disease (CLF) in rubber trees (Hevea brasiliensis). CLF has great economic impact in rubber-producing countries. However, the molecular mechanisms involved in the pathogenicity of C. cassiicola remain poorly understood. Mitogen-activated protein kinase (MAPK) is one of the major signaling pathways responsible for regulation of fungal development and virulence in many plant fungal pathogens. The C. cassiicola cck1 gene encodes a MAPK that is homologous to the rice pathogen Magnaporthe grisea MAPK Pmk1 protein. In this study, targeted cck1 gene disruption and complementation experiments were carried out in C. cassiicola. Compared to the wild-type and CΔcck1 complement, the Δcck1 mutant had more pigmentation and exhibited dramatically reduced aerial mycelial mass and mycelial growth rates, along with the inability to produce conidia or conidiophores. In addition, the Δcck1 hyphae were darker in color and had less branches and septae with visibly condensed protoplasm. The Δcck1 mutant was more resistant to hyperosmotic stress, and was able to produce greater amount of laccase and lesser cellulase in vitro; however, the production of laccase was delayed. Importantly, Δcck1 mycelia and crude toxin were less virulent upon inoculation of rubber tree leaves. These findings indicate that the C. cassiicola CCK1 MAP kinase is a versatile regulator involved in nearly every aspect of plant fungal pathogenicity including mycelial growth, development, differentiation, pigmentation, conidiation, production of extracellular degradation enzymes, osmoregulation, and virulence.

Can individual variation in phenotypic plasticity enhance population viability?

In response to climatic and other sources of environmental variation, individuals within a population may adjust their behavioral, morphological or physiological responses to varying environmental conditions through phenotypic plasticity. In seasonal environments, time constraints related to seasonality, as well as variation in climatic factors, may affect body mass growth rates. To cope with the consequences of a harsh period, individuals may, for example, compensate for lost body mass by accelerating their growth rate in the following period. Phenotypically plastic responses like this can, therefore, directly affect body mass, which may affect individual fitness and, ultimately, population dynamics. Here, we use a well-studied population of yellow-bellied marmots, Marmota flaviventris, in Colorado to parametrize and develop an individual-based model (IBM) to investigate how phenotypically plastic responses in body mass growth rate may compensate for an individual’s bad start after a harsh period (compensatory growth), and to explore whether individual variation in compensatory growth favors population persistence under less favorable climatic scenarios. A simulation model that allowed marmots with a body mass less than the population’s average body mass to compensate their growth provided the best match with observed population sizes, suggesting the importance of trade-offs in population dynamics. We also found that compensatory growth plays an important role in decreasing the probability of extinction under both less favorable colder and random climate scenarios. Our results lead to a deeper understanding of the mechanisms that govern population fluctuations and highlight the importance of quantifying the fitness cost of phenotypically plastic responses.

The laccase gene (LAC1) is essential for Colletotrichum gloeosporioides development and virulence on mango leaves and fruits

Colletotrichum gloeosporioides is the main causal agent of anthracnose of mango (Mangifera indica), which has great economic impact on mango industry worldwide. Laccase has versatile biological functions including: melanin biosynthesis and pathogenicity in several other pathogenic fungi. A laccase gene LAC1, homologous to C. lagenarium laccase, was cloned from C. gloeosporioides. To evaluate its role, LAC1 was disrupted via gene replacement, and the mutant Δlac1 was analyzed. Compared with the wild-type, the Δlac1 mutant had less pigmentation and dramatically reduced aerial mycelial mass and radial growth rates, and rarely produces conidia in vitro. Microscopic observation showed that Δlac1 hyphae were lighter in color, less branched and septated with obviously more condensed protoplasm than wild-type. The Δlac1 mutant was obviously different in nutritional utilization compared with the wild-type. Virulence tests showed that Δlac1 mycelia were weakly virulent on non-wounded mango leaves and fruits, and was significantly less virulent on wounded mango leaves and fruits. The Δlac1 produced less extracellular cell wall-degrading enzymes (CWDE) and no detectable extracellular laccase activity in vitro. These results suggest that the C. gloeosporioides LAC1 laccase is involved not only in virulence, but also in mycelial growth and differentiation, conidiation, appressorium formation, pigmentation, melanin biosynthesis, secretion of extracellular hydrolytic enzymes, and utilization of exogenous nutrition.

Vaidya spacetime in the diagonal coordinates

We have analyzed the transformation from initial coordinates $(v,r)$ of the Vaidya metric with light coordinate $v$ to the most physical diagonal coordinates $(t,r)$. An exact solution has been obtained for the corresponding metric tensor in the case of a linear dependence of the mass function of the Vaidya metric on light coordinate $v$. In the diagonal coordinates, a narrow region (with a width proportional to the mass growth rate of a black hole) has been detected near the visibility horizon of the Vaidya accreting black hole, in which the metric differs qualitatively from the Schwarzschild metric and cannot be represented as a small perturbation. It has been shown that, in this case, a single set of diagonal coordinates $(t,r)$ is insufficient to cover the entire range of initial coordinates $(v,r)$ outside the visibility horizon; at least three sets of diagonal coordinates are required, the domains of which are separated by singular surfaces on which the metric components have singularities (either $g_{00}=0$ or $g_{00}=\infty$.). The energy-momentum tensor diverges on these surfaces; however, the tidal forces turn out to be finite, which follows from an analysis of the deviation equations for geodesics. Therefore, these singular surfaces are exclusively coordinate singularities that can be referred to as false firewalls because there are no physical singularities on them. We have also considered the transformation from the initial coordinates to other diagonal coordinates $(\eta,y)$, in which the solution is obtained in explicit form, and there is no energy-momentum tensor divergence.

Evidence of differential mass change rates between human breast cancer cell lines in culture.

Investigating the growth signatures of single cells will determine how cell growth is regulated and cell size is maintained. The ability to precisely measure such changes and alterations in cell size and cell mass could be important for applications in cancer and drug screening. Here, we measure the mass growth rate of individual benign (MCF-10A), non-invasive (MCF-7), and highly-invasive malignant (MDA-MB-231) breast cancer cells. A micro-patterning technique was employed to allow for the long-term growth of motile cells. Results show mass growth rates at 4.8%, 1.2%, and 2.8% for MCF-10A, MCF-7, and MDA-MB-231, demonstrating that normal cells have a higher mass growth rate than cancerous cells. All the cell lines show an increase in mass change rate indicating that the mass accumulation rate is exponential over a single cell cycle. The growth rates measured with our MEMS sensor are compared with doubling times obtained through conventional bulk analysis techniques, and exhibit excellent agreement.

Growth of ice particle mass and projected area during riming

Abstract. There is a long-standing challenge in cloud and climate models to simulate the process of ice particle riming realistically, partly due to the unrealistic parameterization of the growth of ice particle mass (m) and projected area (A) during riming. This study addresses this problem, utilizing ground-based measurements of m and ice particle maximum dimension (D) as well as theory to formulate simple expressions describing the dependence of m and A on riming. It was observed that β in the m − D power law m = α Dβ appears independent of riming during the phase 1 (before the formation of graupel), with α accounting for the ice particle mass increase due to riming. This semi-empirical approach accounts for the degree of riming and renders a gradual and smooth ice particle growth process from unrimed ice particles to graupel, and thus avoids discontinuities in m and A during accretional growth. Once the graupel with quasi-spherical shape forms, D increases with an increase in m and A (phase 2 of riming). The treatment for riming is explicit, and includes the parameterization of the ice crystal–cloud droplet collision efficiency (Ec) for hexagonal columns and plates using hydrodynamic theory. In particular, Ec for cloud droplet diameters less than 10 µm are estimated, and under some conditions observed in mixed-phase clouds, these droplets can account for roughly half of the mass growth rate from riming. These physically meaningful yet simple methods can be used in models to improve the riming process.

Food availability influences postmetamorphic growth in two spadefoot toad species (genus Pelobates)

Understanding how major life history traits such as body size and mass and growth change in response to resource availability is crucial in explaining life history trade-offs. We conducted a laboratory experiment with three (high, medium and low) feeding intensity treatments using metamorphs of two spadefoot toads species,Pelobates syriacusandP. fuscus, from syntopic populations. We tested how total food consumption, final body size and mass, body mass increase, body mass and length growth rates and growth efficiency are influenced by food availability. The responses to food availability differed significantly between the species with respect to the total food consumption, body mass increase, body mass growth rate and growth efficiency (i.e. the ratio between total amount of food consumed during the experiment divided by the increase in body mass).P. syriacusmetamorphs had higher growth rates and growth efficiency thanP. fuscusjuveniles. Also,P. syriacusjuveniles responded to differences in food level by increasing growth efficiency with decreasing food levels. OverallP. syriacusseems better adapted to shortages in food availability thanP. fuscus. Our results clearly indicate that the differences in body size between the two species originate between metamorphosis and sexual maturity.

Characteristics of body mass growth in semialtricial and altricial bird species during the nestling period

The dynamics of body mass growth were studied in nestlings of 22 semialtricial and altricial bird species based on materials collected in seven regions of Russia in the years 1976–2013. The bird species belong to four orders and 13 families. The results of the study indicate the nonuniform growth of nestlings in different bird species. Of the species investigated, only seven were found to reach or exceed the mass of adult birds. Over the nestling period, the nestlings of open-nesting species, such as the hooded crow (Corvus cornix), rook (Corvus frugilegus), magpie (Pica pica), fieldfare (Turdus pilaris), song thrush (Turdus philomelos), and goldfinch (Carduelis carduelis), do not reach the weight of adult birds and their growth continues after they leave the nest. In closed-nesting species, only the nestlings of the barn swallow (Hirundo rustica) reach or exceed the definitive mass, whereas the nestlings of the jackdaw (Corvus monedula), starling (Sturnus vulgaris), wryneck (Jynx torquilla), tree sparrow (Passer montanus), and great tit (Parus major) continue to grow after leaving the nest. The body mass of birds on the day of their hatching and before their departure from the nests and the mass of adult birds depend on the nesting type, duration of the nestling period, size groups of species, and their definitive size. The average specific growth rate of body mass and its maximum values for different species are also associated with these factors. The maximum specific growth rate in small-sized and medium-sized bird species was observed on the 0–1st days of life; in large bird species, on the 2nd–4th days. The specific growth rate did not depend on the type of nesting, but it was inversely related to the duration of the nestling period and the definitive sizes of birds.

Alternating low quality hay with access to annual ryegrass pastures affected stocker performance

Little is known about the effect of limiting access to high nutritive value pastures on subsequent pasture and stocker response when alternating with low quality bermudagrass (Cynodon dactylon) hay. In 3 consecutive years, 54 steers were randomly allotted to 3 treatments: (1) CON steers were continuously stocked on annual ryegrass (Lolium multiflorum Lamarck; Munz, 1973) pastures (1,040 kg of BW/ha); (2) HY24 steers grazed 50% of the area assigned to the CON treatment (2,081 kg of BW/ha) every other day. Steers grazed annual ryegrass for 24 h and then returned to a barn for 24 h where bermudagrass hay was fed; (3) HY72 steers grazed 50% of the area assigned to the CON treatment (2,079 kg of BW/ha) for 96 h and then returned to the barn for 72 h where bermudagrass hay was fed. There was a year effect (P < 0.05) on forage and animal performance. Treatment affected forage mass, nutritive value, and forage growth rate (P < 0.05). Estimated ryegrass DMI was influenced (P = 0.03) by treatments as was ADG (P < 0.001) and gain per hectare (P < 0.001). Treatment effect (P < 0.05) on plasma urea-N and nonesterified fatty acids is probably explained by the lower DMI in HY24 and HY72 compared with CON and the lower intake of hay in HY72. Alternating hay feeding with access to ryegrass (24 h pasture, 24 h hay) allowed for increasing stocking rates (kg of BW/ha) and productivity on annual ryegrass compared with longer periods of hay feeding, which negatively affected animal performance and BW gain per hectare.

Effect of housing density on growth, agonistic behaviour, and activity in hatchling saltwater crocodiles (Crocodylus porosus)

The purpose of this study was to examine the effect of density on growth rate, agonistic behaviour, activity and use of space by hatchling C. porosus in captivity. Hatchling C. porosus were raised in identical enclosures (1.5m2) at different densities (3.3, 6.7, 13.3 and 20.0hatchlings/m2; or 0.30, 0.15, 0.08 and 0.05m2/hatchling respectively). Hatchlings came from 5 different clutches, hatched on the same day, spread evenly between density treatments (2 replicates per treatment). Growth rate (grams per day) was assessed between 4 and 25days of age, which is a reliable indicator of post-hatching growth trajectories for this species. Clutch and initial body mass (BM) had a strong influence on growth rate, with a lower growth rate among the largest hatchlings born. The highest mean growth rate in body mass occurred at 6.7/m2 (6.12±1.24g/d) and was lowest at the highest density (20.0/m2: −2.33±0.63g/d). Behavioural observations taken every 10min on day 19 (24h period) confirmed that hatchlings remained relatively inactive and hidden under cover for most of the day, and were more active at night, with peaks at dusk and dawn. However, the level of hourly activity (mean movements per individual per hour) was highest at densities of 13.3/m2 and 20.0/m2, compared with densities of 3.3/m2 and 6.7/m2. Behavioural observations at 17:00–8:00h over 3days (days 17–19) revealed that the frequency of agonistic interactions (mean per animal per night) was highest at the lower densities (3.3/m2; 6.7/m2) and decreased with increased density (13.3/m2; 20.0/m2). The results suggest that as density increases above 6.7/m2, growth rate in hatchling C. porosus during the first 3 weeks begins to decline as activity increases. However, at the lowest density (and group size: 5), 1 or 2 individuals become dominant and grow large at the expense of the remaining hatchlings. Based on these results, it appears that the high and low densities tested may have an adverse effect on hatchling C. porosus growth rate and behaviour in captivity.

Quasistationary solutions of scalar fields around accreting black holes

Massive scalar fields can form long-lived configurations around black holes. These configurations, dubbed quasi-bound states, have been studied both in the linear and nonlinear regimes. In this paper we show that quasi-bound states can form in a dynamical scenario in which the mass of the black hole grows significantly due to the capture of infalling matter. We solve the Klein-Gordon equation numerically in spherical symmetry, mimicking the evolution of the spacetime through a sequence of analytic Schwarzschild black hole solutions of increasing mass. It is found that the frequency of oscillation of the quasi-bound states decreases as the mass of the black hole increases. In addition, accretion leads to a significative increase of the exponential decay of the scalar field energy due to the presence of terms of order higher than linear in the exponent. We compare the black hole mass growth rates used in our study with estimates from observational surveys and extrapolate our results to values of the scalar field masses consistent with models that propose scalar fields as dark matter in the universe. We show that even for unrealistically large mass accretion rates, quasi-bound states around accreting black holes can survive for cosmological timescales. Our results provide further support to the intriguing possibility of the existence of dark matter halos based on (ultra-light) scalar fields surrounding supermassive black holes in galactic centers.

Experimental sand burial affects seedling survivorship, morphological traits, and biomass allocation of &amp;lt;i&amp;gt;Ulmus pumila&amp;lt;/i&amp;gt; var. &amp;lt;i&amp;gt;sabulosa&amp;lt;/i&amp;gt; in the Horqin Sandy Land, China

Abstract. As a native tree species, Ulmus pumila var. sabulosa (sandy elm) is widely distributed in the Horqin Sandy Land, China. However, seedlings of this species have to withstand various depths of sand burial after emergence because of increasing soil degradation, which is mainly caused by overgrazing, climate change, and wind erosion. An experiment was conducted to evaluate the changes in its survivorship, morphological traits, and biomass allocation when seedlings were buried at different burial depths: unburied controls and seedlings buried vertically up to 33, 67, 100, or 133 % of their initial mean seedling height. The results showed that partial sand burial treatments (i.e., less than 67 % burial) did not reduce seedling survivorship, which still reached 100 %. However, seedling mortality increased when sand burial was equal to or greater than 100 %. In comparison with the control treatment, seedling height and stem diameter increased at least by 6 and 14 % with partial burial, respectively. In the meantime, seedling taproot length, total biomass, and relative mass growth rates were at least enhanced by 10, 15.6, and 27.6 %, respectively, with the partial sand burial treatment. Furthermore, sand burial decreased total leaf area and changed biomass allocation in seedlings, partitioning more biomass to aboveground organs (e.g., leaves) and less to belowground parts (roots). Complete sand burial after seedling emergence inhibited its re-emergence and growth, even leading to death. Our findings indicated that seedlings of sandy elm showed some resistance to partial sand burial and were adapted to sandy environments from an evolutionary perspective. The negative effect of excessive sand burial after seedling emergence might help in understanding failures in recruitments of sparse elm in the study region.

Impact of changing wind conditions on foraging and incubation success in male and female wandering albatrosses.

Wind is an important climatic factor for flying animals as by affecting their locomotion, it can deeply impact their life-history characteristics. In the context of globally changing wind patterns, we investigated the mechanisms underlying recently reported increase in body mass of a population of wandering albatrosses (Diomedea exulans) with increasing wind speed over time. We built a foraging model detailing the effects of wind on movement statistics and ultimately on mass gained by the forager and mass lost by the incubating partner. We then simulated the body mass of incubating pairs under varying wind scenarios. We tracked the frequency at which critical mass leading to nest abandonment was reached to assess incubation success. We found that wandering albatrosses behave as time minimizers during incubation as mass gain was independent of any movement statistics but decreased with increasing mass at departure. Individuals forage until their energy requirements, which are determined by their body conditions, are fulfilled. This can come at the cost of their partner's condition as mass loss of the incubating partner depended on trip duration. This behaviour is consistent with strategies of long-lived species which favoured their own survival over their current reproductive attempt. In addition, wind speed increased ground speed which in turn reduced trip duration and males foraged further away than females at high ground speed. Contrasted against an independent data set, the simulation performed satisfactorily for males but less so for females under current wind conditions. The simulation predicted an increase in male body mass growth rate with increasing wind speed, whereas females' rate decreased. This trend may provide an explanation for the observed increase in mass of males but not of females. Conversely, the simulation predicted very few nest abandonments, which is in line with the high breeding success of this species and is contrary to the hypothesis that wind patterns impact incubation success by altering foraging movement.

Levitation Diffusion Chamber Measurements of the Mass Growth of Small Ice Crystals from Vapor

Abstract A levitation diffusion chamber designed to examine the mass growth from the vapor of small ice particles (diameter &amp;lt; 100 μm) at ambient pressure (≃970 hPa) and low temperature (T &amp;lt; −30°C) is presented. The diffusion chamber is unique in that charged ice particles are levitated by an opposing voltage on the lower copper plate with lateral stability provided by button quadrupole electrodes attached to the upper copper plate. The button electrodes are far from the ice particle growth region, allowing ice particles to grow free of substrate influences. Experiments have been conducted for temperatures from −30° to −35.7°C, ice supersaturations from 2.5% to 28.6%, and over growth times ranging from 5 to 15 min. The experiments indicate that mass varies nonlinearly in time and exhibits a dependence on initial particle radius and ice supersaturation in accord with expectations from theory. In contrast to expectations from spherical capacitance theory, the derived mass growth rates do not scale linearly with radius, and derived effective shape factors (capacitance normalized with radius) are approximately 0.5. Fitting the growth data with a theoretical model indicates that growth is limited by surface kinetics with deposition coefficients ranging from 0.003 to 0.02.

Mass Growth Rates, Plumage Development, and Related Behaviors of Snowy Owl (Bubo scandiacus) Nestlings

Abstract In 1993 and 1995, we detailed body mass growth rates, plumage development, and related behaviors of Snowy Owl (Bubo scandiacus) nestlings from Barrow, Alaska. We recorded data from 71 of 80 nestlings from 14 of 20 nests in 1993 and 154 of 161 nestlings from 33 of 54 nests in 1995. Only nestlings for which we had data from hatching to at least 25 d of age were included in the growth model. Nestlings hatched between 1–3 d after “pipping” (creating a hole in) the eggshell. The semi-altricial young were covered in white protoptile (first) down plumage at hatching and weighed about 44–45 g. For about the first 7 d, their eyes were closed and movement was limited; the nestlings were dependent on the female for thermoregulation, food, and protection. Growth was rapid and by 8–9 d, the dark gray mesoptile (second) down had begun replacing protoptile down. By about 9–11 d, eyes were open, and by about 14 d, the owls were dark gray in color, and primary flight feather quills emerged. Mass gains were greate...

The evolution in the stellar mass of brightest cluster galaxies over the past 10 billion years

Using a sample of 98 galaxy clusters recently imaged in the near infra-red with the ESO NTT, WIYN and WHT telescopes, supplemented with 33 clusters from the ESO archive, we measure how the stellar mass of the most massive galaxies in the universe, namely Brightest Cluster Galaxies (BCG), increases with time. Most of the BCGs in this new sample lie in the redshift range $0.2<z<0.6$, which has been noted in recent works to mark an epoch over which the growth in the stellar mass of BCGs stalls. From this sample of 132 clusters, we create a subsample of 102 systems that includes only those clusters that have estimates of the cluster mass. We combine the BCGs in this subsample with BCGs from the literature, and find that the growth in stellar mass of BCGs from 10 billion years ago to the present epoch is broadly consistent with recent semi-analytic and semi-empirical models. As in other recent studies, tentative evidence indicates that the stellar mass growth rate of BCGs may be slowing in the past 3.5 billion years. Further work in collecting larger samples, and in better comparing observations with theory using mock images is required if a more detailed comparison between the models and the data is to be made.

Fruit growth characterization of the tomato (Solanum lycopersicum L.) hybrid Ichiban' grown under cover

The tomato (Solanum lycopersicum L.) is one of the more important crops that are consumed worldwide. In Colombia, the department of Boyaca is characterized as being the biggest producer of tomatoes, with production centered in the municipalities of Sutamarchan, Sachica, Santa Sofía and Villa de Leyva, where different cultivars and hybrids are produced that present different physiological behaviors, resulting in changes in conventional agronomic management. This study aimed to evaluate the growth and development of fruits from the tomato hybrid Ichiban under greenhouse conditions. This study evaluated the parameters of polar and equatorial diameters, diameter ratio, fresh mass and dry mass, and absolute and relative growth rates. The results were subjected to a descriptive analysis. Furthermore, the growth model was determined. The Ichiban hybrid had a simple sigmoid behavior, common in fleshy fruits, while the fresh mass and dry mass were fitted to a logistic, nonlinear model. Anthesis was seen at 50 days after transplant and the fruits reached physiological maturity 49 days after anthesis; during this period, 510.2 heating degree-days were accumulated. All of the variables presented significant differences (P≤0.01) and coefficients of determination above 0.9, indicating that the models are suitable for explaining the studied biological phenomena.

Dietary lipid oxidation tolerance of juvenile Arctic charr (Salvelinus alpinus) and Nile tilapia (Oreochromis niloticus)

The effects of dietary lipid oxidation on fish are diverse and contradictory. In this study, herring oil was oxidized to five different levels (peroxide values (POV): 20.44, 182.97, 56.12, 33.27 and 0.00meqkg−1) and used to formulate five experimental diets. Juvenile Arctic charr (Salvelinus alpinus, mean body mass±SD: 2.41±0.11g) were reared on the five diets for 67days. In another experiment, juvenile Nile tilapia (Oreochromis niloticus) (1.71±0.40g) were reared on three diets formulated with oxidized oils having POV of 19.55, 447.27 and 32.72 respectively, for 90days. Growth responses were monitored in quadruplicate groups of 60 individuals of Arctic charr and 100 for Nile tilapia, respectively. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were only studied in Arctic charr.At the end of the study, the Arctic charr group reared on a diet with oils in the primary oxidation state had significantly lower body mass and specific growth rate, but higher hepatosomatic index compared to the rest of the groups. The activities of CAT and GPx increased with dietary lipid oxidation while that of SOD remained fairly stable. In Nile tilapia, both final body mass and condition factor were significantly lower in the group fed fresh oil than in the groups fed oxidized oils. Fillet lipid content decreased with lipid oxidation while ash and protein did not differ amongst tilapia groups. The results suggest that Arctic charr are more susceptible to lipid oxidation than are Nile tilapia. These differences may be the result of species differences in tolerance to oxidized lipids, variable lipid intake or access to vitamin E/tocopherol in feed. Statement of RelevanceImportant for Arctic charr and Nile tilapia feed development.

The influence of light, substrate and seed origin on the germination and establishment of an ant-garden bromeliad.

Plant germination and development depend upon a seed's successful dispersal into a suitable habitat and its ability to grow and survive within the surrounding biotic and abiotic environment. The seeds of Aechmea mertensii, a tank-bromeliad species, are dispersed by either Camponotus femoratus or Neoponera goeldii, two ant species that initiate ant gardens (AGs). These two mutualistic ant species influence the vegetative and reproductive traits of the bromeliad through their divergent ecological preferences (i.e. light and substrate). We hypothesised that the seeds dispersed by these two ant species have underlying genetic differences affecting germination, growth and survival of A.mertensii seedlings in different ways. To test this, we used an experimental approach consisting of sowing seeds of A.mertensii: (i) taken from the two AG-ant associations (i.e. seed origin), (ii) in two contrasting light conditions, and (iii) on three different substrates. Light and substrate had significant effects on germination, survival and on eight key leaf traits reflecting plant performance. Seed origin had a significant effect only on germination and on two leaf traits (total dry mass and relative growth rate). Overall, this bromeliad performs better (i.e. high growth and survival rates) when growing both in the shade and in the carton nest developed by C.femoratus ants. These results suggest that the plasticity of the tank bromeliad A.mertensii is mainly due to environment but also to genetic differences related to seed origin, as some traits are heritable. Thus, these two ant species may play contrasting roles in shaping plant evolution and speciation.