Rana Temporaria Tadpoles Research Articles

A laboratory experimental assessment of the sensibility of Rana temporaria tadpoles to the effects of car traffic-associated seismic disturbances

"Vibrations generated by road traffic are considered to be a form of physical environmental pollution. Nonetheless, the effect of this disturbance in natural habitats, and in particular on the aquatic stage of amphibians, received very little attention from the scientific community. This study aims to assess the direct effect of mechanical waves and the consequent water turbidity on the aquatic larval stage of Rana temporaria by exposing an experimental group to laboratory-induced vibrations and comparison with a non-exposed control group. Our results show that this kind of pollution had no significant effect on the development rate, the length of the larval period, and the mortality of the larvae. However, we identified a significant effect on the size of animals, both during the larval period, and at metamorphosis. This result raises concern about the long-term risks to the amphibian population exposed to this type of low-profile pollution. Keywords: development, growth, metamorphosis, amphibian performance, traffic-related pollution"

Microplastics in biotic and abiotic compartments of high-mountain lakes from Alps

Microplastic (MP) pollution is a major environmental concern for mountain ecosystem and for high-mountain lakes in particular, which are recognized indicators of global change. In this study, the presence of MPs was assessed in abiotic (water and sediment) and biotic (zooplankton, tadpoles, fish) compartments of two high-mountain lakes (Upper Lake Balma and Lower Lake Balma) in the Cottian Alps (northwest Italy). No MPs were found in water and zooplankton samples, whereas the mean MPs in sediment samples was 1.33 ± 0.67 items/m3 and 1.75 ± 0.62 items/m3 in Lower and Upper Lake Balma, respectively. The mean MPs in tadpoles of Rana temporaria was 0.33 ± 0.58 items/individual and 0.66 ± 0.58 items/individual in Lower and Upper Lake Balma, respectively. The mean number of MPs items found in the gastrointestinal tract (GIT) of fish (Salvelinus fontinalis) was considerably higher in specimens from the Lower (0.45 items/g GIT) than in those from the Upper Lake (0.20 items/g GIT). There was a negative relationship between fish size (weight and age) and MPs abundance in the GIT of fish, indicating that young fish accumulated more MP items probably due to the high prey ingestion rate compared to adults. The same MPs color (blue, white, black), shape (fibers and fragments), and chemical type (polypropylene and polyethylene) were found in the compartments of both lakes. Our findings suggest the use of S. fontinalis as an indicator of MP pollution in high-mountain lakes. Further studies are needed to better understand the sources and the effects of MPs in these remote ecosystems.

Contributions of water-borne corticosterone as one non-invasive biomarker in assessing nitrate pollution stress in tadpoles of Rana temporaria

Among a multitude of stressors to which wildlife is exposed, environmental pollution is a pervasive one that poses a serious threat. The permeable skin of amphibians is likely to increase direct contact of the body with pollutants, making them a group worth studying to access environmental quality. Consequently, finding reliable and complementary biomarkers that will present detectable and predictable changes in response to pollutants is essential to identify pollution sublethal effects on amphibians and to investigate whether these are in part responsible for population declines. The glucocorticoid hormone corticosterone (CORT), involved in many metabolic functions, is often used to measure the physiological stress response to environmental stressors in amphibians. In this study, we evaluated whether water-borne CORT can serve as a non-invasive biomarker for nitrate pollution stress in the European common frog (Rana temporaria) by comparing the effect of nitrate exposure on hormone release rates and on other physiological downstream biomarkers, i.e., ultimate physiological effects of the stressor. Specifically, we investigated the effect of different nitrate concentrations (0, 10, 50, and 100 mg/L) on water-borne CORT release rates, age, size, and body condition. Exposure to nitrate pollution significantly increased age at metamorphosis and water-borne CORT release rates, and led to reduced mass and body condition, but only at higher nitrate concentrations (i.e., 50 and 100 mg/L). Considering this similar sensitivity to other acknowledged biomarkers, water-borne CORT was a reliable biomarker of physiological stress in R. temporaria exposed to nitrate pollution stress in a controlled single-stressor laboratory approach. Thus, water-borne CORT is a promising method to be included in more holistic approaches. We recommend that such approaches keep testing multiple biomarker combinations, as species are exposed to several stressors likely to interact and produce varied outcomes in different biomarkers in their natural habitats.

The effect of the photoperiod on the larval development and growth of two amphibian species (Amphibia: anura)

ABSTRACT The photoperiod regulates the growth and development of many animals. We conducted experiments and studied the effect of the photoperiod on the growth and development of the larvae and young of two amphibian species Rana temporaria and Xenopus laevis. We studied photoperiods: constant absence of light – 0 h light/24 h darkness (0L/24D), 8 h light/16 h darkness (8L/16D), 12 h light/12 h darkness (12L/12D), 16 h light/8 h dark (16L/8D), and round-the-clock lighting (24L/0D). We found out that the size of the Rana temporaria tadpoles was the highest with photoperiods 24L/0D, 16L/8D, 12L/12D. A decrease in the parameters was observed in the absence of light and the photoperiod 8L/16D. The pace of development began to differ after the 10th day of the experiment. The development was slower with the photoperiod 0L/24D. The highest percentage of tadpoles’ mortality was observed in total darkness (0L/24D), the lowest percentage was observed in the photoperiod 16L/8D. The photoperiod had no effect on the Xenopus laevis young. The mechanisms of the photoperiod’s effect on the larval development and growth of amphibians are discussed.

Does Bti (Bacillus thuringiensis var. israelensis) affect Rana temporaria tadpoles?

Biocides based on toxins of Bacillus thuringiensis var. israelensis (Bti) are established as alternatives to conventional chemical insecticides for mosquito control all across the globe since they are regarded ecologically compatible and harmless to non-target species. Since recent studies on amphibian larvae have called this opinion into question, we exposed Rana temporaria tadpoles to single (1 mg/L), tenfold (10 mg/L) and hundredfold (100 mg/L) field concentrations of VectoBac® WG (a water dispersible granule Bti formulation) in the laboratory for eleven days to investigate whether larvae were adversely affected by Bti and its endotoxin proteins. In addition to a negative (water) control, a positive control based on organic rice protein (50 mg/L) was run to check for the nutritional relevance of Bti proteins.There was no Bti-related mortality and a histopathological analysis of tadpole intestines revealed no adverse effects. Analyses of biomarkers for proteotoxicity (stress protein family, Hsp70) and neurotoxicity or metabolic action (b-esterases acetylcholine esterase (AChE) and carboxylesterases) revealed no significant differences between Bti treatments and the negative control. The responses of tadpoles in the protein-supplemented positive control differed from those of the negative control and the Bti treatments. Tadpoles in the positive control had reduced body mass and elevated AChE activity.

Development and evaluation of gene expression biomarkers for chemical pollution in common frog (Rana temporaria) tadpoles

Pollutants have been proposed as one factor in the worldwide declines of amphibian species and populations. Applying gene expression analysis of liver RNA in tadpoles would be a possible approach for biomarker measurements to increase knowledge of ecological health in amphibian populations. The major aim of this study was to explore the relevance of applying gene expression analyses of cytochrome p450 (cyp1a), metallothionein (mt), and vitellogenin (vtg) in Rana temporaria tadpoles. Therefore, tadpoles were exposed for 1 week to β-naphthoflavone (BNF), cadmium chloride (CdCl2), and ethinylestradiol (EE2). Primers were developed for RT-qPCR to analyze gene expression in livers. The result showed that the methods for gene expression analyses of cyp1a, mt, and vtg as well as the reference gene β-actin (bact) were successful not only in R. temporaria but also in another amphibian, Rana arvalis. The gene expression of cyp1a was induced by BNF and the gene expression of mt was induced by CdCl2 but no significant induction was recorded in vtg expression after exposure to EE2. Gene expressions varied throughout the tadpole metamorphosis development, in particular for vtg. Overall, the use of gene expression of cyp1a and mt as biomarkers in wild tadpoles seems promising while the use of vtg seems less relevant due to high natural variation and low background expression. The study shows that variations in gene expressions between tadpoles of different genetic origin are important to consider when evaluating the data. The present study has thus increased the background knowledge about gene expression applicability as biomarker for tadpoles.

A matter of proportion? Associational effects in larval anuran communities under fish predation

In Batesian mimicry, a species lacking defences against predators benefits from mimicking the aposematic signal of a defended species, while the model may incur the costs of reduced defensive efficacy. Similar reciprocal indirect effects may emerge even when the signal is not mimicked; termed associational effects, such interactions are well known in plants sharing herbivores but have received little attention in animal studies. We investigated associational interactions in a system where unequally defended prey (chemically defended Bufo bufo and undefended Rana temporaria tadpoles), sharing general morphology but not an aposematic signal, were exposed to predation by the carp Cyprinus carpio along a gradient of relative prey abundance. In the absence of fish, the assemblage composition had no effect on the survival of Rana, while that of Bufo decreased with increasing abundance of Rana. Fish reduced the survival of tadpoles from both species. However, increased relative abundance of Bufo in the community led to enhanced survival in both Bufo and Rana. Increasing relative proportions of heterospecifics reduced metamorph mass only in Bufo, indicating greater sensitivity to interspecific competition compared to Rana; the effect was reduced in the presence of fish. Our results show that undefended non-mimetic prey enjoy reduced predation with increasing relative abundance of chemically defended prey, which in turn suffer greater mortality with an increasing proportion of the undefended species. Associational resistance/susceptibility, driven by current assemblage composition, not by selection for resemblance, can shape the dynamics of mixed communities of defended and undefended prey in the absence of mimicry.

Maximal Information Coefficient and Support Vector Regression Based Nonlinear Feature Selection and QSAR Modeling on Toxicity of Alcohol Compounds to Tadpoles of Rana temporaria

Efficient evaluation of biotoxicity of organics is of vital significance to resource utilization and environmental protection. In this study, toxicity of 110 alcohol compounds to tadpoles of Rana temporaria is adopted as the dependent variable and 1388 physiochemical parameters (features) calculated by PCLIENT are used for representing each compound. A feature selection pipeline with three steps is developed to refine the feature subset: 282 features that significantly correlated with biotoxicity of chemical compounds are preliminarily selected via the maximum information coefficient (MIC); 138 descriptors that have positive contribution to the model’s performance are reserved after a support vector regression (SVR) based backward elimination; 18 descriptors are finally selected via a forward selection process that integrated minimal redundancy maximal relevance (mRMR), MIC and SVR. In terms of feature subsets with different numbers of variables, quantitative structure activity relationship (QSAR) models are built using multiple linear regression (MLR), partial least square regression (PLS) and SVR, respectively. The independent prediction evaluation index, Q2, increases from -74.787, 0.824 and 0.868 to 0.892, 0.878 and 0.940, for the three regression models, respectively. Results suggest that nonlinear feature selection methods involved in MIC and SVR can effectively eliminate irrelevant descriptors. SVR outperforms classical statistical models to QSAR modeling on high-dimensional data containing nonlinear relationship between features. The methods proposed in this study have a potential application in the QSAR research field such as biotoxicity compounds.

Ecotoxicological effects of downstream wastewater samples on Cloeon perkinsi larvae, Rana temporaria tadpoles and Clarias gariepinus frys and fingerlings

Indiscriminate dumping of refuse and direct defaecation into surface water bodies alter physico-chemical qualities of the water and adversely affect the existence of certain fauna. Downstream water samples were collected from five streams (Irefin, Gege, Gbagi, Odinjo and Omi Adio) receiving domestic wastes in Ibadan and a control stream within the University of Ibadan, Oyo state, Nigeria. Physico-chemical qualities of the downstream water were analysed using standard methods.  Acute toxicity of contaminated water was investigated on some fauna. The 48-hour-LC50 of stream samples was determined for Cloeon perkinsi (mayfly) larvae (CP); while 96-hour-LC50 for Rana temporaria tadpoles, Clarias gariepinus frys (CG1) and fingerlings (CG2) were determined using Probit method. Zero dissolved oxygen values were recorded for Irefin and Gege while 1.07 mg/L was recorded for Odinjo and these were lower than permissible limit for aquatic life. The values of biochemical oxygen demand (43.34 – 160.66 mg/L), chemical oxygen demand (136 – 487.10 mg/L) and phosphate (81.63 – 1877.60 mg/L) recorded for all the samples were significantly higher (P<0.05) than the control sample and were higher than limits set by National Environmental Standards and Regulatory Enforcement Agency (NESREA). The 48-hour-LC50 of contaminated stream water to CP (Irefin, 12.67%; Gege, 8.63%), and 96-hour-LC50 to CG1 (Gege, 0.79%; Gbagi, 2.75%) and CG2 (Gege, 3.33%; Irefin, 5.64%) indicated high toxicity of the sites. High toxicity of the study sites revealed that the streams were polluted in Ibadan. Therefore, there is need for adequate management and disposal of solid wastes to prevent further environmental contamination.

Is bigger really better? Relative and absolute body size influence individual growth rate under competition.

Models suggest that the mechanism of competition can influence the growth advantage associated with being large (in absolute body size or relative to other individuals in the population). Large size is advantageous under interference, but disadvantageous under exploitative competition. We addressed this prediction in a laboratory experiment on Rana temporaria tadpoles competing for limited food. There were 166 target individuals spanning a 10‐fold range in body mass reared for 3 days with three other individuals that were either the same size, half as large, or twice as large as the target. Relative growth rate (proportion per day) declined with size, and absolute growth rate (mass per day) reached a peak at intermediate size and declined thereafter. Tadpoles grew slowly if they were large relative to their competitors, although relative body size was less important than absolute size. As a result, size variation declined in groups that were initially composed of individuals of variable size. Thus, bigger was not better under exploitative competition. Our results help connect individual‐level behavior with individual growth and the size distribution of the population.

Climate change will alter amphibian‐mediated nutrient pathways: evidence from Rana temporaria tadpoles in experimental ponds

Summary With global warming, mean temperatures and brownification of many waterbodies are predicted to increase. This may have unknown consequences on aquatic consumer life histories and nutrient content, consumer‐mediated nutrient recycling, and nutrient transport between water and land. Using a large‐scale experimental pond facility, we altered temperature (ambient/+4 °C) and brownification (clear/humic) in a 2 × 2 factorial design (n = 16 pond sections) to test two aspects of climate change on Rana temporaria tadpole life‐history traits and on tadpole‐mediated nutrient pathways. On day 16 after hatching, we examined tadpole‐mediated nutrient recycling by measuring tadpole nutrient excretion and egestion rates and tadpole body nutrient content. We estimated tadpole growth and development rates from hatching to emergence and measured emergent frog body size and body nutrient content. Brownification increased total pond water nutrient availability and total pond water nitrogen (N) : phosphorous (P) ratios. Warming positively affected tadpole growth and development rates, whereas browning increased tadpole growth rate only under ambient temperatures. Emergent frog body P content decreased with warming, but only in the clear treatments. But despite these variations in body nutrient content, body stoichiometry remained within a relatively narrow stoichiometric range for both emergent frogs (P content: 1.4–1.8%, N content: 11.4–11.8% and carbon [C] content: 46.9–51.3%) and tadpoles (P content: 1.1–1.2%, N content: 10.1–11.7% and C content: 48.0–50.5%). Warming increased tadpole body P content and browning had a positive effect on tadpole body N content and tadpole N excretion rates, probably mediated by the increased pond water total N availability. We conclude that warming and brownification will interact in changing aquatic consumer growth and body nutrient stoichiometry. In addition, warming has the potential to affect emergent frog body nutrient content and may thus affect nutrient transport from water to land. Last, by increasing pond water N availability, brownification appears to intensify consumer P limitation and thus amplify consumer‐meditated N recycling.

Cool tadpoles from Arctic environments waste fewer nutrients - high gross growth efficiencies lead to low consumer-mediated nutrient recycling in the North.

Endothermic organisms can adapt to short growing seasons, low temperatures and nutrient limitation by developing high growth rates and high gross growth efficiencies (GGEs). Animals with high GGEs are better at assimilating limiting nutrients and thus should recycle (or lose) fewer nutrients. Longer guts in relation to body mass may facilitate higher GGE under resource limitation. Within the context of ecological stoichiometry theory, this study combines ecology with evolution by relating latitudinal life-history adaptations in GGE, mediated by gut length, to its ecosystem consequences, such as consumer-mediated nutrient recycling. In common garden experiments, we raised Rana temporaria tadpoles from two regions (Arctic/Boreal) under two temperature regimes (18/23 °C) crossed with two food quality treatments (high/low-nitrogen content). We measured tadpole GGEs, total nutrient loss (excretion + egestion) rates and gut length during ontogeny. In order to maintain their elemental balance, tadpoles fed low-nitrogen (N) food had lower N excretion rates and higher total phosphorous (P) loss rates than tadpoles fed high-quality food. In accordance with expectations, Arctic tadpoles had higher GGEs and lower N loss rates than their low-latitude conspecifics, especially when fed low-N food, but only in ambient temperature treatments. Arctic tadpoles also had relatively longer guts than Boreal tadpoles during early development. That temperature and food quality interacted with tadpole region of origin in affecting tadpole GGEs, nutrient loss rates and relative gut length, suggests evolved adaptation to temperature and resource differences. With future climate change, mean annual temperatures will increase. Additionally, species and genotypes will migrate north. This will change the functioning of Boreal and Arctic ecosystems by affecting consumer-mediated nutrient recycling and thus affect nutrient dynamics in general. Our study shows that evolved latitudinal adaption can change key ecosystem functions.

The Rate of Degradation of Chemical Cues Indicating Predation Risk: An Experiment and Review

AbstractMany prey taxa use kairomones or alarm pheromones to assess the risk of predation in aquatic environments, and the rate at which these cues attenuate determines how precisely they indicate the local density of predators. We estimated the rate of degradation of chemical cues generated by Aeshna dragonfly larvae feeding on Rana temporaria tadpoles. The half‐life of the cue was 35 h and was not influenced by whether it was aged in pond water or tap water or whether other tadpoles were present in the container in which cue‐aging occurred. A review of other published estimates of predator cue half‐life revealed values of 0.2–126 h, and variation among studies was unrelated to the type of aging water, the venue in which water was aged or prey behavior observed (laboratory, field), or the type of behavior that was recorded. We conclude that factors affecting the persistence of predator cues remain uncertain in spite of their importance for understanding the evolution of induced defenses.

Phenotypic plasticity in the hepatic transcriptome of the European common frog (Rana temporaria): the interplay between environmental induction and geographical lineage on developmental response

Phenotypic plasticity might facilitate adaptation to new environmental conditions through the enhancement of initial survival of organisms. Once a population is established, further adaptation and diversification may occur through adaptive trait evolution. While several studies have found evidence for this mechanism using phenotypic traits, much less is known at the level of gene expression. Here, we use an islands system of frog populations that show local adaptation and phenotypic plasticity to pool drying conditions in development time until metamorphoses. We examined gene expression differences in Rana temporaria tadpole livers with respect to pool drying at the source population and in response to simulated pool drying in the laboratory. Using a MAGEX cDNA microarray and quantitative real-time polymerase chain reaction (qPCR), we identified an increase in several gene transcripts in response to artificial pool drying including thyroid hormone receptor alpha and beta, carbamoyl phosphate synthetase 1, ornithine transcarbamylase and catalase. In addition, these gene transcripts also showed greater abundance in island populations that developed faster. Hence, the gene transcripts were related to both constitutive response (higher levels in island populations that developed faster) and plastic response (increased abundance under decreasing water levels). This pattern is in accordance with genetic accommodation, which predicts similarities between plastic gene expression and constitutive expression in locally adapted populations.

Hot tadpoles from cold environments need more nutrients – life history and stoichiometry reflects latitudinal adaptation

1. High-latitude species (and populations within species) are adapted to short and cold summers. They often have high growth and development rates to fully use the short growing season and mature before the onset of winter. 2. Within the context of ecological stoichiometry theory, this study combines ecology with evolution by relating latitudinal life-history adaptations to their molecular consequences in body nutrient composition in Rana temporaria tadpoles. 3. Temperature and food quality were manipulated during the development of tadpoles from Arctic and Boreal origins. We determined tadpole growth rate, development rate, body size and nutrient content, to test whether (i) Arctic tadpoles could realize higher growth rates and development rates with the help of higher-quality food even when food quantity was unchanged, (ii) Arctic and Boreal tadpoles differed in their stoichiometric (and life history) response to temperature changes, (iii) higher growth rates lead to higher tadpole P content (growth rate hypothesis) and (iv) allometric scaling affects tadpole nutrient allocation. 4. We found that especially Arctic tadpoles grew and developed faster with the help of higher-quality food and that tadpoles differed in their stoichiometric (and life history) response to temperature changes depending on region of origin (probably due to different temperature optima). There was no evidence that higher growth rates mediated the positive effect of temperature on tadpole P content. On the contrary, the covariate growth rate was negatively connected with tadpole P content (refuting the growth rate hypothesis). Lastly, tadpole P content was not related to body size, but tadpole C content was higher in larger tadpoles, probably due to increased fat storage. 5. We conclude that temperature had a strong effect on tadpole life history, nutrient demand and stoichiometry and that this effect depended on the evolved life history.

Effects of a sublethal pesticide exposure on locomotor behavior: A video-tracking analysis in larval amphibians

Organochlorine pesticides such as endosulfan have been shown to have both lethal and sublethal effects on amphibians. In this context, behavioral endpoints have proved their usefulness in evidencing impacts of such chemicals at environmental concentrations that do not necessarily cause mortality. The recent development of video-tracking technologies now offers the possibility of accurately quantifying locomotor behaviors. However, these techniques have not yet been applied to evaluating the toxicity of pesticides in amphibians. We therefore aimed at determining the potential toxicity of endosulfan on endpoints associated with locomotion after short-term environmental endosulfan exposure in Rana temporaria tadpoles and at using these data as warning systems for survival alterations after a longer exposure. To this end, we analyzed video-tracks of 64 tadpoles (two pesticide treatments: 5 and 50μgL−1, one control and one solvent-control) with Ethovision XT 7 software. The highest endosulfan concentration had a significant effect on all four behavioral endpoints. Contaminated tadpoles traveled shorter distances, swam less often, at a lower mean speed, and occupied a less peripherical position than control tadpoles. The lowest endosulfan concentration had similar but lower effects, and did not affect mean speed during swimming. Survival was reduced only after a long-term exposure to endosulfan and was associated with short-term behavioral dysfunctions. These results show that endosulfan strongly affects the behavioral repertory of amphibian tadpoles, but in different ways depending on concentration, thus suggesting that the pesticide has complex modes of action. Given the importance of locomotion and space use in tadpole success in their aquatic environment, these results confirm the toxic action of endosulfan. By highlighting effects before mortality markers, video-tracking systems also show their potential as sentinels of sublethal effects of pesticides.

Visual cues contribute to predator detection in anuran larvae

The ability of prey to detect predators directly affects their probability of survival. Chemical cues are known to be important for predator detection in aquatic environments, but the role of other potential cues is controversial. We tested for changes in behaviour of Rana temporaria tadpoles in response to chemical, visual, acoustic, and hydraulic cues originating from dragonfly larvae (Aeshna cyanea) and fish (Gasterosteus aculeatus). The greatest reduction in tadpole activity occurred when all cues were available, but activity was also significantly reduced by visual cues only. We did not find evidence for tadpoles lowering their activity in response to acoustic and hydraulic cues. There was no spatial avoidance of predators in our small experimental containers. The results show that anuran larvae indeed use vision for predator detection, while acoustic and hydraulic cues may be less important. Future studies of predator-induced responses of tadpoles should not only concentrate on chemical cues but also consider visual stimuli. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012,

Geographic variation in corticosterone response to chronic predator stress in tadpoles

Chronic stress often affects growth and development negatively, and these effects are often mediated via glucocorticoid hormones, which elevate during stress. We investigated latitudinal variation in corticosterone (CORT) response to chronic predator stress in Rana temporaria tadpoles along a 1500-km latitudinal cline in Sweden tadpoles, in a laboratory experiment. We hypothesized that more time-constrained high-latitude populations have evolved a lower CORT response to chronic stress to maintain higher growth under stressful conditions. Southern tadpoles had higher CORT content in response to predators after 1 day of exposure, whereas there was no increase in CORT in the northern populations. Two weeks later, there were no predator-induced CORT elevations. Artificially elevated CORT levels strongly decreased growth, development and survival in both northern and southern tadpoles. We suggest that the lower CORT response in high-latitude populations can be connected with avoidance of CORT-mediated reduction in growth and development, but also discuss other possible explanations.

Influence of experimental venue on phenotype: multiple traits reveal multiple answers

Summary1. Experiments in ecology occur in the laboratory, mesocosm or field. The choice of venue can influence the outcome and may be associated with trade‐offs involving realism and precision.2. We evaluated these trade‐offs in an experiment measuring effects of venue on larval traits of Rana temporaria tadpoles. The design included laboratory, mesocosm and field venues, crossed with two treatments (presence and absence of caged Anax imperator dragonfly larvae). Realism of venues was evaluated by comparing experimental with wild tadpoles.3. Venue influenced nearly every trait we measured, but some were more sensitive to venue than others. Larval and metamorphic performance, external morphology and predator‐induced plasticity in many traits varied among venues, while behaviour was less dependent on venue. Tadpoles in mesocosms were most similar to those in field enclosures and the wild, although the phenotypic response to predation risk was greatest in the mesocosm venue. The laboratory environment triggered highly distinctive morphology. Precision was not higher in the laboratory than in other venues.4. This study suggests that both constraints and research questions must be considered when choosing an appropriate experimental venue.

Alteration of mitochondrial efficiency affects oxidative balance, development and growth in frog (Rana temporaria) tadpoles

Mitochondria are known to play a central role in life history processes, being the main source of reactive oxygen species (ROS), which promote oxidative constraint. Surprisingly, although the main role of the mitochondria is to produce ATP, the plasticity of mitochondrial ATP generation has received little attention in life history studies. Yet, mitochondrial energy transduction represents the physiological link between environmental resources and energy allocated to animal performance. Studying both facets of mitochondrial functioning (ATP and ROS production) would allow better understanding of the proximate mechanisms underlying life history. We have experimentally modulated the mitochondrial capacity to generate ROS and ATP during larval development of Rana temporaria tadpoles, via chronic exposure (34 days) to a mitochondrial uncoupler (2,4-dinitrophenol, dNP). The aim was to better understand the impact of mitochondrial uncoupling on both responses in terms of oxidative balance, energy input (oxygen and feeding consumption) and energy output (growth and development of the tadpole). Exposure to 2,4-dNP reduced mitochondrial ROS generation, total antioxidant defences and oxidative damage in treated tadpoles compared with controls. Despite the beneficial effect of dNP on oxidative status, development and growth rates of treated tadpoles were lower than those in the control group. Treatment of tadpoles with 2,4-dNP promoted a mild mitochondrial uncoupling and enhanced metabolic rate. These tadpoles did not increase their food consumption, and thus failed to compensate for the energy loss elicited by the decrease in the efficiency of ATP production. These data suggest that the cost of ATP production, rather than the oxidative balance, is the parameter that constrains growth/development of tadpoles, highlighting the central role of energy transduction in larval performance.