Eating increases oxidative damage in a reptile

While eating has substantial benefits in terms of both nutrient and energy acquisition, there are physiological costs associated with digesting and metabolizing a meal. Frequently, these costs have been documented in the context of energy expenditure while other physiological costs have been relatively unexplored. Here, we tested whether the seemingly innocuous act of eating affects either systemic pro-oxidant (reactive oxygen metabolite, ROM) levels or antioxidant capacity of corn snakes (Pantherophis guttatus) by collecting plasma during absorptive (peak increase in metabolic rate due to digestion of a meal) and non-absorptive (baseline) states. When individuals were digesting a meal, there was a minimal increase in antioxidant capacity relative to baseline (4%), but a substantial increase in ROMs (nearly 155%), even when controlling for circulating nutrient levels. We report an oxidative cost of eating that is much greater than that due to long distance flight or mounting an immune response in other taxa. This result demonstrates the importance of investigating non-energetic costs associated with meal processing, and it begs future work to identify the mechanism(s) driving this increase in ROM levels. Because energetic costs associated with eating are taxonomically widespread, identifying the taxonomic breadth of eating-induced ROM increases may provide insights into the interplay between oxidative damage and life history theory

Taxonomic Chauvinism Revisited: Insight from Parental Care Research

Parental care (any non-genetic contribution by a parent that appears likely to increase the fitness of its offspring) is a widespread trait exhibited by a broad range of animal taxa. In addition to influencing the fitness of parent(s) and offspring, parental care may be inextricably involved in other evolutionary processes, such as sexual selection and the evolution of endothermy. Yet, recent work has demonstrated that bias related to taxonomy is prevalent across many biological disciplines, and research in parental care may be similarly burdened. Thus, I used parental care articles published in six leading journals of fundamental behavioral sciences (Animal Behaviour, Behavioral Ecology, Behavioral Ecology and Sociobiology, Ethology, Hormones and Behavior, and Physiology & Behavior) from 2001–2010 (n = 712) to examine the year-to-year dynamics of two types of bias related to taxonomy across animals: (1) taxonomic bias, which exists when research output is not proportional to the frequency of organisms in nature, and (2) taxonomic citation bias, which is a proxy for the breadth of a given article—specifically, the proportion of articles cited that refer solely to the studied taxon. I demonstrate that research on birds likely represents a disproportionate amount of parental care research and, thus, exhibits taxonomic bias. Parental care research on birds and mammals also refers to a relatively narrow range of taxonomic groups when discussing its context and, thus, exhibits taxonomic citation bias. Further, the levels of taxonomic bias and taxonomic citation bias have not declined over the past decade despite cautionary messages about similar bias in related disciplines— in fact, taxonomic bias may have increased. As in Bonnet et al. (2002), my results should not be interpreted as evidence of an ‘ornithological Mafia’ conspiring to suppress other taxonomic groups. Rather, I generate several rational hypotheses to determine why bias persists and to guide future work

Data from: Food-limited mothers favor offspring quality over offspring number: a principal components approach

Mothers are expected to balance the tradeoff between the number and quality of offspring, and many theoretical studies describe how the maternal environment might influence the evolution of the number-quality tradeoff. However, few empirical studies attempt to test these theories (and their assumptions) by measuring the fitness consequences of variation in investment per offspring. Part of the problem is that measuring offspring fitness is difficult, which frequently leads experimenters to measure several proxies of offspring fitness in place of a comprehensive fitness assay. This strategy tends to result in multiple univariate analyses that involve different offspring fitness proxies, and these tests can have low power and may produce conflicting conclusions. Here, we demonstrate the benefits of integrating maternal fecundity and proxies of offspring size and fitness into multivariate analyses to elucidate variation in reproductive allocation strategies. In a 2×2 factorial experiment, we manipulated the quality of maternal environment (food availability) throughout early and late adulthood (acute and chronic exposure to the maternal environment) in a field cricket. We developed a multivariate index of reproductive allocation by incorporating maternal fecundity and the performance of offspring in low- and high-food environments into a principle components analysis. This index of reproductive allocation indicated that females decreased fecundity and increased offspring quality after chronic exposure to low-food environments, thereby providing evidence of adaptive plasticity in investment per offspring. In contrast, few treatment effects were observed using univariate analyses. The present study demonstrates that multivariate analysis can increase our ability to assess the adaptive significance of reproductive strategies, particularly in situations when offspring size and fitness are difficult to measure with accuracy. Such an approach might ultimately help assess the adaptive significance of reproductive allocation across a wider range of taxa, thereby providing broader insight into the evolution of reproductive strategies

The role of python eggshell permeability dynamics in a respiration-hydration trade-off.

International audienceParental care is taxonomically widespread because it improves developmental conditions and thus fitness of offspring. Although relatively simplistic compared with parental behaviors of other taxa, python egg-brooding behavior exemplifies parental care because it mediates a trade-off between embryonic respiration and hydration. However, because egg brooding increases gas-exchange resistance between embryonic and nest environments and because female pythons do not adjust their brooding behavior in response to the increasing metabolic requirements of developing offspring, python egg brooding imposes hypoxic costs on embryos during the late stages of incubation. We conducted a series of experiments to determine whether eggshells coadapted with brooding behavior to minimize the negative effects of developmental hypoxia. We tested the hypotheses that python eggshells (1) increase permeability over time to accommodate increasing embryonic respiration and (2) exhibit permeability plasticity in response to chronic hypoxia. Over incubation, we serially measured the atomic and structural components of Children's python (Antaresia childreni) eggshells as well as in vivo and in vitro gas exchange across eggshells. In support of our first hypothesis, A. childreni eggshells exhibited a reduced fibrous layer, became more permeable, and facilitated greater gas exchange as incubation progressed. Our second hypothesis was not supported, as incubation O2 concentration did not affect the shells' permeabilities to O2 and H2O vapor. Our results suggest that python eggshell permeability changes during incubation but that the alterations over time are fixed and independent of environmental conditions. These findings are of broad evolutionary interest because they demonstrate that, even in relatively simple parentalcare models, successful parent-offspring relationships depend on adjustments made by both the parent (i.e., egg-brooding behavioral shifts) and the offspring (i.e., changes in eggshell permeability)

Reproductive allocation data for female Gryllus texensis

Reproductive allocation data for female Gryllus texensi

Data from: The double-edged sword of immune defence and damage control: do food availability and immune challenge alter the balance?

1.Animal immune systems must adaptively balance aggressive immune resistance (ability to destroy pathogens) with infection tolerance (ability to withstand the negative effects of infection; e.g., immunopathology or damage due to pathogen metabolism). 2.Insects offer unique insight into this balancing act because phenoloxidase (PO)-mediated melanisation is a key feature of immune resistance, but PO activation obligates the production of non-specific reactive species that can cause self-damage. The antioxidant glutathione (GSH) can provide protection against such reactive molecules, but high levels of GSH can impair melanisation. In support of the hypothesis that GSH can protect insects (e.g., crickets) from self-damage during an immune response, we found that bacterially infected crickets showed a significant positive relationship between GSH haemolymph concentration and fecundity after controlling for bacterial growth rate. That is, GSH may be a mechanism of infection tolerance because it correlated with fecundity despite bacterial proliferation. 3.Next, we factorially manipulated food availability and immune activation in female crickets to examine whether the relative balance between a component of immune resistance (i.e., PO) and protection from self-damage (i.e., GSH) was plastic and sensitive to environmental conditions. 4.Glutathione and PO were positively correlated, and the PO:GSH ratio was robust and not affected by food availability or immune activation. Thus, increased investment in a mechanism of immune resistance may obligate a concomitant increase in GSH to reduce self-damage (i.e., increase infection tolerance). Chronic immune activation led to greater tolerance of oxidative stress suggesting that repeated immune activation up-regulates infection tolerance mechanisms. Food limitation led to reduced PO activity, but not GSH concentration. This result suggests that mechanisms of immune resistance may be more sensitive to resource scarcity than mechanisms of infection tolerance. 5.We demonstrate that some mechanisms of immune resistance and infection tolerance can be correlated, and that they can be affected by food availability or immune activation

Data from: Eating increases oxidative damage in a reptile

While eating has substantial benefits in terms of both nutrient and energy acquisition, there are physiological costs associated with digesting and metabolizing a meal. Frequently, these costs have been documented in the context of energy expenditure while other physiological costs have been relatively unexplored. Here, we tested whether the seemingly innocuous act of eating affects either systemic pro-oxidant (reactive oxygen metabolites: ROM) levels or antioxidant capacity of corn snakes (Pantherophis guttatus) by collecting plasma during absorptive (peak increase in metabolic rate due to digestion of a meal) and non-absorptive (baseline) states. When individuals were digesting a meal, there was a minimal increase in antioxidant capacity relative to baseline (4%), but a substantial increase in ROMs (nearly 155%), even when controlling for circulating nutrient levels. We report an oxidative cost of eating that is much greater than that due to long distance flight or mounting an immune response in other taxa. This result demonstrates the importance of investigating non-energetic costs associated with meal processing, and it begs future work to identify the mechanism(s) driving this increase in ROM levels. Because energetic costs associated with eating are taxonomically widespread, identifying the taxonomic breadth of eating-induced ROM increases may provide insights into the interplay between oxidative damage and life history theory

DataDryad

Data used for all data analyse