Effects of food quality on life history of the rotifer Brachionus calyciflorus Pallas

1. Herbivorous zooplankton face considerable temporal and spatial variation in food quality, to which they respond by adapting their life histories. Zooplankton may even take up mineral nutrients directly, and use these to counter the effects of algal nutrient limitation (mineral compensation). This study examined the life history of the rotifer Brachionus calyciflorus fed phosphorus‐, and nitrogen‐limited Scenedesmus obliquus (Chlorophyta), and investigated whether B. calyciflorus was capable of mineral compensation. 2. Both phosphorus‐ and nitrogen‐limited algae gave similar life history responses: somatic growth and reproduction were reduced, whereas lifespan remained unaffected. 3. No evidence was found for mineral compensation in B. calyciflorus in relation to detrimental life history effects, so mineral compensation does not seem to be relevant for this species under field conditions. 4. The similarity in life history responses of B. calyciflorus and the low levels of ω‐3 PUFAs in both phosphorus‐ and nitrogen‐depleted algae suggest that ω‐3 PUFAs were limiting to B. calyciflorus, although other (bio)chemicals or mineral nutrients may also have been important. 5. No trade‐off was observed between life span and reproduction during algal nutrient limitation. Reduced population growth rates of B. calyciflorus were caused by shorter reproductive periods.     

Paternal effects on haddock early life history traits

Paternal effects on haddock Melanogrammus aeglefinus early life history traits were examined by crossing eggs and sperm in a nested design and analysing the progeny at 0, 5 and 10 days post‐hatch (dph). The proportion of the variance in early life history traits that was due to paternity was significant for hatching success, larval standard length, myotome height, jaw length and yolk size, but not eye diameter or yolk utilization efficiency. Some morphological traits were influenced more by paternity than maternity. The findings suggest that the importance of males in the early life history success of marine fishes be reconsidered.     

Impact of turbulence on riverine zooplankton: a mesocosm experiment

1. With increases in river discharge over time and space, zooplankton generally encounter increased turbulence, turbidity, hydraulic forces, downstream advection and food limitations, all of which should affect species diversity and densities. Of these factors, the role of turbulence on the distribution of zooplankton is least known along longitudinal and lateral dimensions in river networks. 2. We tested the factorial effects of turbulence and grazing level on Ohio River potamoplankton in spring and summer using twelve 1600‐L, outdoor mesocosms. Turbulence was calculated using the Froude number for equal depths but with current velocities of 0.064 and 0.32 m s^?1. Grazing levels corresponded to a high density treatment (=ambient river densities of rotifers, copepods and cladocerans) and a low density treatment (initially no zooplankton >64 μm). All tanks had the same water residence time, and hydraulic stress was minimized by circular flow patterns. 3. Zooplankton densities and population growth rates were significantly affected by turbulence level and season. In general, rotifer populations grew faster in high turbulence tanks (though Keratella and Brachionus populations flourished in both treatments in summer) and microcrustaceans thrived better in low turbulence environments. The larger, calanoid copepods handled more turbulent conditions much better than cyclopoids or nauplii. Zooplankton had no detectable effects on particulate organic carbon concentrations in either month (values were higher in spring), but rotifers reduced chlorophyll concentrations in both months. 4. The relative importance of turbulence in controlling potamoplankton is probably to vary not only on a longitudinal basis in river networks but also with both the hydrogeomorphic complexity of river reaches and the type and amount of river regulation. Plans for river rehabilitation and management should incorporate non‐turbulent habitats in large rivers as a means of enhancing zooplankton populations and providing an important food web component for planktivores.     

Dietary effects on life history traits in a terrestrial isopod: the importance of evaluating maternal effects and trade-offs

Studies of life history aim to explain patterns in the evolution of reproductive investment, growth, and survival. Trade-offs between traits are a fundamental component of life history theory. In herbivorous arthropods life history traits are often responsive to variation in numerous environmental factors, especially diet quality. Using three artificial diets under controlled laboratory conditions, we examined changes in life history traits (i.e. growth rate, offspring number, offspring size, incubation period), trade-offs between traits, and maternal effect on the growth rate of offspring, in the common woodlouse (terrestrial isopod), Porcellio laevis. The high protein diet had significant impacts on offspring production, triggering a smaller-sized offspring, and demonstrating a trade-off between these last two traits. The high carbohydrate diet seldom exerted a significant effect on incubation period. The quality of dietary items evidently has important consequences on the life history of the mother and, thus, on offspring growth; the directions of these effects, however, were opposite. Mothers fed diets with high protein concentrations presented significant maternal effects, measured as offspring growth rate during later ontogeny. Our results support the notion that protein, rather than carbohydrate, concentrations in the diet limit herbivorous arthropods, and have significant consequences on life history traits, as was seen for P. laevis. Clearly, the change in phenotypic correlations between incubation period and offspring number from negative to positive is an empirical demonstration of the context dependence of life history trait trade-offs.     

Dietary fatty acid effects on morphogenesis in bithorax mutants

Three bithorax alleles of Drosophila melanogaster were tested to determine if dietary additions of fatty acids would alter their gene expression. For the bx¹ allele, myristic, oleic, and linoleic acids were all effective in reducing gene expression while fatty acid supplementation was ineffective with the bx³ and bx^34e alleles. For bx¹ the nutritionally sensitive period was found to occur in the first 48 h of larval life.     

Thematic review series: patient-oriented research. Dietary fat, carbohydrate, and protein: effects on plasma lipoprotein patterns

In general, under isoweight conditions, different types of dietary protein or individual amino acids have little effect on lipoprotein patterns. Dietary carbohydrate tends to increase plasma triglyceride when it displaces fat, accompanied by a decrease in HDL cholesterol concentrations. Potential differential effects of types of carbohydrate are difficult to assess because of differences in rates of absorption and confounding of dietary fiber. Saturated fatty acids increase LDL and HDL cholesterol, whereas trans fatty acids increase LDL but not HDL cholesterol. Unsaturated fatty acids decrease LDL and HDL cholesterol, polyunsaturated more so than monounsaturated. There has been considerable interest in the potential benefit of major shifts in dietary macronutrients on weight loss and lipoprotein patterns. Short-term data favor substituting protein and fat for carbohydrate, whereas long-term data have failed to show a benefit for weight loss. During an active weight loss period low-carbohydrate diets more favorably affect triglyceride and HDL and less favorably affect LDL cholesterol concentrations. Additional efforts need to be focused on gaining a better understanding of the effect of dietary macronutrient profiles on established and emerging cardiovascular disease risk factors, mechanisms for changes observed and contributors to individual variability. Such data are needed to allow reassessment and, if necessary, modification of current recommendations.     

Manipulation of habitat quality: effects on chironomid life history traits

1. To understand how habitat heterogeneity affects organisms, the present authors measured the response of chironomid life-histories to single patch types in a controlled laboratory experiment. The objective was to determine whether the size and type of leaf particles in the substratum affect development rate and survival of larvae, and the fecundity of the resulting adults.
2. Chironomus riparius larvae were raised in sand supplemented with dogwood, Cornus florida, (a rapid decomposer) or American sycamore, Platanus occidentalis, (a refractory decomposer) leaves fully crossed in a factorial design with four leaf particle sizes (0.2, 0.5, 1 and 5 cm²), or in sand only.
3. Development time was shorter in dogwood habitats than sycamore habitats, and shorter in sycamore habitats than in sand habitats. Survival was higher and larval head capsule lengths of instars III and IV were larger in dogwood than in sycamore or sand habitats. Development time was longer and head capsule lengths of instars III and IV were smaller in habitats with 5-cm² leaf particles than in 0.2-, 0.5- and 1-cm² particle size treatments. Female thorax length (a measure of fecundity) did not differ among treatments.
4. The present authors conclude that, for C. riparius confined to a single patch type, fitness is significantly enhanced when the patch contains small particles of dogwood (labile) leaves.     

Positive effects of an arbuscular mycorrhizal fungus on aphid life history traits

Two generations of two aphid species (Myzus ascalonicus and M. persicae) were reared on Plantago lanceolata plants, with and without root colonization by the arbuscular mycorrhizal fungus, Glomus intraradices. Life history traits of the aphids measured were nymphal development time, teneral adult weight, growth rate, total fecundity, adult longevity and duration of post-reproductive life. For both aphids in both generations, mycorrhizal colonization increased aphid weight and fecundity, while other traits were unaffected. The increases were consistent between generations. In a second experiment, M. persicae was reared on plants with and without the fungus, under varying N and P regimes. The results of N addition were inconclusive because there was high aphid mortality. However, under P supplementation, positive effects of the mycorrhiza on aphid growth were seen at low and medium P levels, while at high P levels these effects disappeared. The positive effects of mycorrhizal colonization reported here are contrary to the majority of previous studies with chewing insects, which have reported negative effects. A number of possible mechanisms for this apparent discrepancy are discussed. Received: 1 February 1999 / Accepted: 22 March 1999     

Food effects on life history traits and seasonal dynamics of Ceriodaphnia pulchella

1. This paper describes the effects of differences in food quantity and quality on selected life history traits of Ceriodaphnia pulchella . Animals were fed with four concentrations of two green algae, Scenedesmus obliquus and Chlamydomonas globosa , given separately as well as in a 1 : 1 mixture.
2. In most cases growth, reproduction and condition of the animals and consequently the rate of population increase, r , increased with food concentration. Life history parameters of animals raised on S. obliquus were lowest, whereas no significant differences were found between animals fed with C. globosa and with the mixture of the two algal species.
3. In contrast to the large effects of food quantity and quality found in the laboratory, an analysis of the population dynamics of C. pulchella in Lake Tjeukemeer showed that the effect of changes in food conditions during the growing season of this species was limited, although overall food levels seemed to be poor throughout the year.
4. Changes in the birth rate of the population are mainly governed by changes in temperature, and possibly by changes in the densities of the invertebrate predator Leptodora kindtii .     

Food effects on life history traits and seasonal dynamics of Ceriodaphnia pulchella

1. This paper describes the effects of differences in food quantity and quality on selected life history traits of Ceriodaphnia pulchella . Animals were fed with four concentrations of two green algae, Scenedesmus obliquus and Chlamydomonas globosa , given separately as well as in a 1 : 1 mixture.
2. In most cases growth, reproduction and condition of the animals and consequently the rate of population increase, r , increased with food concentration. Life history parameters of animals raised on S. obliquus were lowest, whereas no significant differences were found between animals fed with C. globosa and with the mixture of the two algal species.
3. In contrast to the large effects of food quantity and quality found in the laboratory, an analysis of the population dynamics of C. pulchella in Lake Tjeukemeer showed that the effect of changes in food conditions during the growing season of this species was limited, although overall food levels seemed to be poor throughout the year.
4. Changes in the birth rate of the population are mainly governed by changes in temperature, and possibly by changes in the densities of the invertebrate predator Leptodora kindtii .     

Context-dependent effects of ranaviral infection on northern leopard frog life history traits

Pathogens have important effects on host life-history traits, but the magnitude of these effects is often strongly context-dependent. The outcome of an interaction between a host and an infectious agent is often associated with the level of stress experienced by the host. Ranavirus causes disease and mortality in amphibian populations in various locations around the world, but most known cases of ranaviral infection have occurred in North America and the United Kingdom. While Ranavirus virulence has been investigated, the outcome of Ranavirus infection has seldom been related to the host environment. In a factorial experiment, we exposed Northern leopard frog (Lithobates pipiens, formerly Rana pipiens) tadpoles to different concentrations of Ranavirus and investigated the effect of host density on certain life-history traits, namely survival, growth rate, developmental stage and number of days from virus exposure to death. Our results suggest a prominent role of density in driving the direction of the interaction between L. pipiens tadpoles and Ranavirus. We showed that increasing animal holding density is detrimental for host fitness as mortality rate is higher, day of death earlier, development longer and growth rate significantly lower in high-density tanks. We observed a linear increase of detrimental effects when Ranavirus doses increased in low-density conditions, with control tadpoles having a significantly higher overall relative fitness. However, this pattern was no longer observed in high-density conditions, where the effects of increasing Ranavirus dose were limited. Infected and control animals fitness were consequently similar. We speculate that the host may eventually diverts the energy required for a metabolic/immune response triggered by the infection (i.e., direct costs of the infection) to better cope with the increase in environmental "stress" associated with high density (i.e., indirect benefits of the infection). Our results illustrate how the net fitness of organisms may be shaped by ecological context and emphasize the necessity of examining the direct/indirect costs and benefits balance to fully understand host-pathogen interactions.     

Plant-mediated effects on life history traits of entomovirus infected caterpillars of Spodoptera exigua

It has been reported that host plants are able to mediate the interactions between insect herbivores and entomoviruses, but how plants affect growth, development, detoxifying enzymes and metabolic enzymes of herbivores infected by entomoviruses has only rarely been studied so far. We compared growth, development duration, activity of a detoxifying enzyme (carboxylesterase) and a metabolic enzyme (acetylcholinesterase) of a caterpillar (Spodoptera exigua) infected with an entomovirus (SeMNPV) or left non-infected that were fed one of four plants (Ipomoea aquatica, Brassica oleracea, Glycine max or Zea mays). Developmental duration was shorter but growth (length, mass) and enzyme activities were higher in NPV-infected caterpillars fed I. aquatica or B. oleracea than those fed G. max or Z. mays. This study suggests that host plants influence the growth impacts of entomoviruses on herbivores by affecting the enzymes of herbivores.     

Phylogenetic effects on functional traits and life history strategies of Australian freshwater fish

Understanding the biogeographic and phylogenetic basis to interspecific differences in species’ functional traits is a central goal of evolutionary biology and community ecology. We quantify the extent of phylogenetic influence on functional traits and life‐history strategies of Australian freshwater fish to highlight intercontinental differences as a result of Australia's unique biogeographic and evolutionary history. We assembled data on life history, morphological and ecological traits from published sources for 194 Australian freshwater species. Interspecific variation among species could be described by a specialist–generalist gradient of variation in life‐history strategies associated with spawning frequency, fecundity and spawning migration. In general, Australian fish showed an affinity for life‐history strategies that maximise fitness in hydrologically unpredictable environments. We also observed differences in trait lability between and within life history, morphological and ecological traits where in general morphological and ecological traits were more labile. Our results showed that life‐history strategies are relatively evolutionarily labile and species have potentially evolved or colonised in freshwaters frequently and independently allowing them to maximise population performance in a range of environments. In addition, reproductive guild membership showed strong phylogenetic constraint indicating that evolutionary history is an important component influencing the range and distribution of reproductive strategies in extant species assemblages. For Australian freshwater fish, biogeographic and phylogenetic history contribute to broad taxonomic differences in species functional traits, while finer scale ecological processes contribute to interspecific differences in smaller taxonomic units. These results suggest that the lability or phylogenetic relatedness of different functional traits affects their suitability for testing hypothesis surrounding community level responses to environmental change.     

Dietary macronutrients modulate the fatty acyl composition of rat liver mitochondrial cardiolipins

The interaction of dietary fats and carbohydrates on liver mitochondria were examined in male FBNF1 rats fed 20 different low-fat isocaloric diets. Animal growth rates and mitochondrial respiratory parameters were essentially unaffected, but mass spectrometry-based mitochondrial lipidomics profiling revealed increased levels of cardiolipins (CLs), a family of phospholipids essential for mitochondrial structure and function, in rats fed saturated or trans fat-based diets with a high glycemic index. These mitochondria showed elevated monolysocardiolipins (a CL precursor/product of CL degradation), elevated ratio of trans-phosphocholine (PC) (18:1/18:1) to cis-PC (18:1/18:1) (a marker of thiyl radical stress), and decreased ubiquinone Q₉; the latter two of which imply a low-grade mitochondrial redox abnormality. Extended analysis demonstrated: i) dietary fats and, to a lesser extent, carbohydrates induce changes in the relative abundance of specific CL species; ii) fatty acid (FA) incorporation into mature CLs undergoes both positive (>400-fold) and negative (2.5-fold) regulation; and iii) dietary lipid abundance and incorporation of FAs into both the CL pool and specific mature tetra-acyl CLs are inversely related, suggesting previously unobserved compensatory regulation. This study reveals previously unobserved complexity/regulation of the central lipid in mitochondrial metabolism.     

Parental environmental effects on life history traits in Arabidopsis thaliana (Brassicaceae)

Environmentally induced maternal effects on offspring phenotype are well known in plants. When genotypes or maternal lineages are replicated and raised in different environmental conditions, the phenotype of their offspring often depends on the environment in which the parents developed. However, the degree to which such maternal effects are maintained over subsequent generations has not been documented in many taxa. Here we report the results of a study designed to assess the effects of parental environment on vegetative and reproductive traits, using glasshouse-raised maternal lines sampled from natural populations of Arabidopsis thaliana . Replicates of five highly selfed lines from each of four wild populations were cultivated in two abiotic environments in the glasshouse, and the quality and performance of seeds derived from these two environments were examined over two generations. We found that offspring phenotype was strongly influenced by parental environment, but because the parental environments differed with respect to the time of seed harvest, it was not possible to distinguish clearly between parental environmental effects and the possible (but unlikely) effects of seed age on offspring phenotype. We observed a rapid decline in the expression of ancestral environmental effects, and no main environmental effects on progeny phenotype persisted in the second generation. The mechanism of transmission of environmental effects did not appear to be associated with the quantity or quality of reserves in the seeds, suggesting that environmental effects may be transmitted across subsequent generations via some mechanism that generates environment-specific gene expression.     

Negative effects of UVB-irradiated phytoplankton on life history traits and fitness of Daphnia magna

SUMMARY 1. We tested the effect of ultraviolet-B (UVB)-irradiated phytoplankton on life history characteristics of Daphnia magna . Two phytoplankton species were used, Chlamydomonas reinhardtii and Cryptomonas pyrenoidifera . The phytoplankton species were cultured under photosynthetically active radiation (PAR) conditions, and under PAR supplemented with ultraviolet-A and ultraviolet-B radiation, and fed to Daphnia .
2. Life history traits of Daphnia were negatively affected when fed on UVB-irradiated Cryptomonas . Size at maturity was depressed and fewer juveniles with lower fitness were produced in the UVB treatments. In the Chlamydomonas experiment, no significant effects were found.
3. The cause of the observed UVB effects is likely to be constraints in food quality. Ultraviolet-B radiation thus has the potential of inhibiting energy transfer from the first to the second trophic level.     

Dietary fat influences electric membrane properties of neurons in cell culture

1. SJL/J mice were maintained on semipurified diets which differed in the ratio of polyunsaturated/saturated fatty acid content (P/S). Exposure was from conception and was maintained for periods ranging from 6 to 34 weeks. 2. Neural cell cultures were prepared from dorsal root ganglia (DRG). After 6 and 20 days of culture, neuronal electric membrane properties were determined quantitatively by intracellular recording. 3. A number of significant differences were observed for the two dietary conditions. DRG from mice on the low-P/s diet had an increase in the rate of fall of both phases of repolarization which, in conjunction with the reduced action potential overshoot, led to a reduced action potential duration. This shift to shorter-duration action potentials was accompanied by a shift to more monophasic falling phases. The low-P/S neurons also exhibited a decreased afterhyperpolarization, decreased specific membrane resistance, and decreased membrane electrical time constant compared to high-P/S neurons. 4. It was concluded that the P/S ratio in the diet can have a significant effect on the electric properties of neurons. The high-P/S neurons tended to have action potentials with biphasic repolarizations and longer durations. In contrast, the low-P/S neurons tended to have action potentials with monophasic repolarizations and shorter durations. Moreover, the known ionic dependence of these two types of action potentials suggested that the low-P/S diet resulted in action potentials with a more exclusive Na dependence, while the high-P/S diet resulted in action potentials with both Na and Ca dependence.     

Food quality effects on life history traits and fitness in the generalist herbivore Daphnia

Summary Life table experiments were conducted on the generalist suspension feeder Daphnia galeata, using as food the two green algae (Chlorophyta) Scenedesmus acutus and Oocystis lacustris. Oocystis was hypothesized to be a lower quality food because it is convered with a thick sheath, believed to reduce digestibility. Results showed that Oocystis is a lower quality food for Daphnia, but only at relatively low food concentrations (0.15 mg C/L) and not at higher concentrations (1.0 mg C/L). At 0.15 mg C/L, Daphnia intrinsic rate of increase (r) when grown on Oocystis was only half that when grown on Scenedesmus. Daphnia r was similar at 0.15 mg C/L Oocystis and 0.075 mg C/L Scenedesmus, indicating that Daphnia requires twice as much Oocystis as Scenedesmus to achieve the same fitness. Intrinsic rate of increase was lower on Oocystis mainly because age at first reproduction was greatly delayed compared to that on Scenedesmus (13.6 vs 7.3 d). In addition, juvenile growth and survivorship were reduced on Oocystis compared with Scenedesmus. Clutch sizes were similar on the two foods, indicating that once individuals reached adulthood, the two foods were similar in quality. In contrast, at high food concentrations (1.0 mg C/L), the two algae were similar in quality for both juveniles and adults, and r was not significantly different on the two foods. Ingestion and assimilation rate experiments whowed that Daphnia consumes the two algae at identical rates, and that adults assimilate the two algae at similar rates. However, juveniles assimilate Oocystis at much lower rates than Scenedesmus, possibly accounting for reduced juvenile growth and delay in age at maturity at low concentrations. Thus, Daphnia exhibits an ontogenetic shift in its ability to utilize Oocystis, and this can result in juvenile bottlenecks in which survival and growth of young age classes are of critical importance in determining population dynamics. Because food quality effects were manifested primarily in juveniles and at low concentrations, food quality effects in nature will depend on phytoplankton abundance and age-structure of Daphnia populations.     

Paternal effects on early life history traits in Northwest Atlantic cod,Gadus morhua

It is important to understand parental effects on early life history of fish as manifested, for example, in individual fitness of offspring. Immediately after fertilization, parental contributions (both genetic and non‐genetic) to embryos will affect larval ontogeny, physiology, morphology and survival. In marine fish, rates of natural mortality are highest during early life and are negatively correlated with rates of growth and body size. In these early life stages (eggs, larvae, young juveniles) subtle differences in mortality can cause large differences in recruitment and year‐class success. Therefore, it is particularly critical to understand factors that contribute to variability in mortality during early life. This study focuses on evaluating the potential influence of paternity on rates of mortality and development in eggs and larvae of Northwest Atlantic cod, Gadus morhua. To accomplish this 12 males and two females were crossed using a full‐factorial breeding design. Paternity had a strong influence on fertilization success, hatching success, cumulative embryonic mortality, larval standard length, eye diameter, yolk‐sac area, and cumulative larval mortality. Female 1 showed an overall ‘weaker’ performance of offspring than Female 2, indicating that deviances can stem from differences in female quality. Nevertheless, paternal contributions to embryonic and larval development were still evident despite differences in female quality, showing that sire effects on offspring are undeniable and can serve as important sources of variation during early life stages in fishes. Overall, these findings have implications for furthering the understanding of recruitment variability and can be used to optimize reproductive output for the aquaculture industry. In addition, the data suggests that the choice of mate during spawning can play a large role in offspring fitness.     

River hydrological seasonality influences life history strategies of tropical riverine fishes

Under a particular set of selective forces, specific combinations of traits (strategies) will be favored in a given population, within the particular constraints of the considered species. For fishes, three demographic strategies have been suggested to result from adaptive responses to environmental predictability (i.e., seasonality): periodic, opportunistic and equilibrium [Winemiller KO, Rose KA (1992) Patterns of life-history diversification in North American fishes: implications for population regulation. Can J Fish Aquat Sci 49:2196–2218]. These strategies optimize fitness within predictable, unpredictable and stable systems, respectively. We tested these predictions of life history trait distribution along a gradient of hydrologic seasonality in West African tropical rivers at the drainage basin scale. We used logistic regression of species presence–absence data to test whether dominant life history traits of species caused community compositional change in response to a gradient of seasonality in hydrologic regime across basins. After accounting for taxonomic relatedness, species body size and statistical redundancy inherent to related traits, we found a higher proportion of species producing a great number of small oocytes, reproducing within a short period of time and presenting a low degree of parental care (the periodic strategy) in highly seasonal drainage basins (e.g., rivers with a short and predictable favorable season). Conversely, in more stable drainage basins (e.g., rivers with a wet season of several months), we observed a greater proportion of species producing small numbers of large oocytes, reproducing within a long period of time and providing parental care to their offspring (the equilibrium strategy). Our results suggest that distributions of tropical freshwater fishes at the drainage basin scale can be partly explained by the match between life history strategies and seasonality gradients in hydrological conditions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.