Tadpole Performance Research Articles

Effects of warming at embryonic and larval stages on tadpole fitness in high-altitude Rana kukunoris

Global warming may affect the early developmental stages of high-altitude amphibians, thereby influencing their later fitness. Yet, this has been largely unexplored. To investigate whether and how the temperatures experienced by embryonic and larval stages affect their fitness at later developmental stages, we designed two experiments in which the embryos and larvae were treated with three temperatures (24, 18 and 12 °C), respectively. Then, the life history traits of the tadpoles during the metamorphotic climax in all treatments were evaluated, including growth rate, survival rate, morphology, thermal physiology, swimming performance, standard metabolic rate (SMR), oxidative and antioxidative system, and metabolic enzyme activities. The results revealed that elevated temperature accelerated metamorphosis but decreased body size at metamorphosis. Additionally, warming during the embryonic and larval stages decreased the thermal tolerance range and induced increased oxidative stress. Furthermore, high embryonic temperature significantly decreased the hatching success, but had no significant effect on swimming performance and SMR. Warming during larval periods was harmful to the survival and swimming performance of tadpoles. The effect size analysis revealed that the negative impacts of embryonic temperature on certain physiological traits, such as growth and development, survival and swimming performance, were more pronounced than those of larval temperature. Our results highlight the necessity for particular attention to be paid to the early stages of amphibians, notably the embryonic stages when evaluating the impact of global warming on their survival.

Changes in thermal sensitivity of Rhinella arenarum tadpoles (Anura: Bufonidae) exposed to sublethal concentrations of different pesticide fractions (Lorsban® 75WG).

The intensive use of agrochemicals and the rapid increase of global temperatures have modified the thermal conditions of aquatic environments, thus increasing amphibians' vulnerability to global warming and positioning them at great risk. Commercial formulations of chlorpyrifos (COM) are the pesticides most widely used in agricultural activities, with a high toxic potential on amphibians. However, little is known about the separate effects of the active ingredient (CPF) and adjuvants (AD). We studied the thermal sensitivity at different concentrations and pesticide fractions in Rhinella arenarum tadpoles, on thermal tolerance limits (CTmax = Critical thermal maximum and CTmin = Critical thermal minimum), swimming speed (Ss), Optimum temperature (Top), and Thermal breadth 50 (B50). Our results demonstrate that the pesticide active ingredient, the adjuvants, and the commercial formulation of chlorpyrifos differentially impair the thermal sensitivity of R. arenarum tadpoles. The pesticide fractions affected the heat and the cold tolerance (CTmax and CTmin), depending on the concentrations they were exposed to. The locomotor performance (Ss, Top, and B50) of tadpoles also varied among fractions, treatments, and environmental temperatures. In the context of climate change, the outcomes presented are particularly relevant, as mean temperatures are increasing at unprecedented rates, which suggests that tadpoles inhabiting warming and polluted ponds are currently experiencing deleterious conditions. Considering that larval stages of amphibians are the most susceptible to changing environmental conditions and the alarming predictions about environmental temperatures in the future, it is likely that the synergism between high temperatures and pesticide exposure raise the threat of population deletions in the coming years.

Importance of Genetic-Fitness Correlations for the Conservation of Amphibians.

Endangered animals suffer from isolation of their habitats. Isolation leads to a reduction in population size as well as a decrease in genetic diversity and a concomitant increase in the risk of extinction. Amphibians are the most endangered vertebrate class. Besides habitat loss, fragmentation and isolation, amphibians are threatened by emerging diseases e.g., chytrid fungus or Ranavirus. By employing experiments, researchers investigate whether changes in genetic diversity within or among isolated populations affect amphibian fitness. While genetic diversity estimates are based on molecular markers, typically microsatellites, fitness is mostly measured as tadpole performance in rearing experiments often under varying environmental conditions. Tadpole performances (e.g., body mass, growth rate and survival) have been found to be negatively affected by low genetic diversity, as several studies have found a positive association between genetic diversity and these fitness traits. Moreover, infection with pathogens also seems to be more likely in individuals or populations with lower genetic diversity. Overall, these genetic-fitness correlations seem to be more pronounced or detectable in smaller, declining populations but not in larger populations. Genomic studies, which sample a larger fraction of the genome, are still scarce in the conservation genetic literature on amphibians. These are likely to increase in upcoming years and may reveal adaptive variants that protect against dangerous pathogens or environmental changes. Altogether, genetic-fitness correlation studies should be a priority in order to develop effective management plans for the genetic rescue of isolated, imperilled amphibian populations.

Performance of bullfrog tadpoles (Lithobates catesbeianus) fed balanced diets using alternative energy ingredients containing vegetable mesocarp

ABSTRACT The objective of this study was to evaluate the performance and metamorphosis of bullfrog tadpoles (Lithobates catesbeianus) fed balanced diets, wherein corn flour was replaced with banana, avocado, and pumpkin meal (all made without the epicarp). Using a completely randomized design, the animals were stored in tanks with a capacity of 30 L in a water recirculation system at a density of 1 tadpole/L. Through biweekly biometric measurements, the weight, standard, and total length were evaluated to determine metamorphic development, weight gain, consumption, feed conversion, specific growth rate, survival, physical-chemical parameters of water, and the percentage carcass composition (only at the end). Tadpoles fed rations balanced with pumpkin and banana flour performed the best, followed by those fed avocado meal and those fed the control ration (p < 0.05). It can be concluded that growth performance is improved in animals fed diets containing 10% pumpkin and banana meal instead of corn, and tadpoles that received the avocado meal had the same performance as the conventional diets. Research should be carried out to assess other avenues for the replacement of ingredients in rations for bullfrog tadpoles.

Growing up in a new world: trait divergence between rural, urban, and invasive populations of an amphibian urban invader

Cities are focal points of introduction for invasive species. Urban evolution might facilitate the success of invasive species in recipient urban habitats. Here we test this hypothesis by rearing tadpoles of a successful amphibian urban coloniser and invader in a common garden environment. We compared growth rate, morphological traits, swimming performance, and developmental rate of guttural toad tadpoles (Sclerophrys gutturalis) from native rural, native urban, and non-native urban habitats. By measuring these traits across ontogeny, we were also able to compare divergence across different origins as the tadpoles develop. The tadpoles of non-native urban origin showed significantly slower developmental rate (e.g., the proportion of tadpoles reaching Gosner stage 31 or higher was lower at age 40 days) than tadpoles of native urban origin. Yet, tadpoles did not differ in growth rate or any morphological or performance trait examined, and none of these traits showed divergent ontogenetic changes between tadpoles of different origin. These findings suggest that prior adaptation to urban habitats in larval traits likely does not play an important role in facilitating the invasion success of guttural toads into other urban habitats. Instead, we suggest that evolutionary changes in larval traits after colonization (e.g., developmental rate), together with decoupling of other traits and phenotypic plasticity might explain how this species succeeded in colonising extra-limital urban habitats.

Thermal Acclimation to the Highest Natural Ambient Temperature Compromises Physiological Performance in Tadpoles of a Stream-Breeding Savanna Tree Frog.

Amphibians may be more vulnerable to climate-driven habitat modification because of their complex life cycle dependence on land and water. Considering the current rate of global warming, it is critical to identify the vulnerability of a species by assessing its potential to acclimate to warming temperatures. In many species, thermal acclimation provides a reversible physiological adjustment in response to temperature changes, conferring resilience in a changing climate. Here, we investigate the effects of temperature acclimation on the physiological performance of tadpoles of a stream-breeding savanna tree frog (Bokermannohyla ibitiguara) in relation to the thermal conditions naturally experienced in their microhabitat (range: 18.8–24.6°C). We quantified performance measures such as routine and maximum metabolic rate at different test (15, 20, 25, 30, and 34°C) and acclimation temperatures (18 and 25°C). We also measured heart rate before and after autonomic blockade with atropine and sotalol at the respective acclimation temperatures. Further, we determined the critical thermal maximum and warming tolerance (critical thermal maximum minus maximum microhabitat temperature), which were not affected by acclimation. Mass-specific routine and mass-specific maximum metabolic rate, as well as heart rate, increased with increasing test temperatures; however, acclimation elevated mass-specific routine metabolic rate while not affecting mass-specific maximum metabolic rate. Heart rate before and after the pharmacological blockade was also unaffected by acclimation. Aerobic scope in animals acclimated to 25°C was substantially reduced, suggesting that physiological performance at the highest temperatures experienced in their natural habitat is compromised. In conclusion, the data suggest that the tadpoles of B. ibitiguara, living in a thermally stable environment, have a limited capacity to physiologically adjust to the highest temperatures found in their micro-habitat, making the species more vulnerable to future climate change.

Direct and indirect effects of chronic exposure to ammonium on anuran larvae survivorship, morphology, and swimming speed

Several constituents of the current global change are usually deemed accountable for the worldwide declines of amphibian populations. Among these, water contamination poses a major threat, especially to larval stages, which are unable to escape a polluted water body. This problem is remarkable in agrosystems, one of the main sources of water pollution and whose area is forecasted to increase in the forthcoming decades. However, pollutants represent a selective pressure that may result in tolerance in affected areas. In this work, we tested whether chronic exposure to a sublethal concentration of ammonium (10 mg/L), one of the most frequent agrochemicals, affects differently hatching success, survivorship, morphology and swimming performance of Pelophylax perezi tadpoles from agrosystem and pine grove habitats. Ammonium diminished survivorship at the earliest stages after hatching. Thus, lower density was a by-product of exposure to ammonium. Higher density slowed down development, reduced snout-vent length, and had a sharper negative effect on body mass and tail length and depth of ammonium treated individuals with respect to the control. In turn, ammonium accelerated development and increased body mass, SVL, and tail length and depth. These effects did not depend on provenance habitat. However, only pine grove tadpoles’ swimming speed was negatively affected by ammonium, which supports the hypothesis that agrosystem tadpoles are more tolerant to ammonium. Finally, corroborating previous findings, tadpoles with larger bodies and tails were faster swimmers, whereas proportionally more massive individuals were slower, and tail depth was unrelated to swimming speed.

Experimental confirmation of effects of leaf litter type and light on tadpole performance for two priority amphibians

AbstractIsolated wetlands embedded within longleaf pine savannas support a high proportion of regional biodiversity including many amphibian species. Today, remnant isolated wetlands are often overgrown and hydrologically altered due to fire exclusion or incompatible, cool season fire regimes. In the absence of warm season fires when wetlands are dry, shrubs and trees succeed herbaceous plants, which alters wetland productivity via effects on light and detritus quality. We used a factorial aquatic mesocosm study to test the effects of altered detritus and shade on the growth, development, and survival of tadpoles of two priority amphibian species: gopher frogs (Rana capito) and ornate chorus frogs (Pseudacris ornata). Gopher frog survival was higher among maidencane, sedge, and pine treatments compared to oak and sweetgum treatments. While gopher frog larval periods were lowest in the sedge treatment, there was a nominal general effect of litter type on gopher frog larval periods, growth rates, and mass at metamorphosis. Shading had a nominal and inconsistent effect on gopher frog growth rates, but did extend larval periods in all litter treatments, decreased survival in all litter treatments except oak, and decreased mass at metamorphosis in all litter treatments except pine and sweetgum. Ornate chorus frog survival was minimally affected by shading and litter treatments, but growth rates and mass at metamorphosis were highest in maidencane and sedge treatments, and larval periods were extended with shading in all litter treatments. Shading also decreased growth rates in maidencane and sedge litters and decreased mass at metamorphosis in pine and sweetgum litters. Our results demonstrate that succession of isolated wetlands can reduce tadpole performance for two priority species both through changes in leaf litter and shading, though the effect on survival, larval growth, larval period, and size at metamorphosis can differ between species. These results support management recommendations to restore and maintain open canopy, grassy conditions in isolated wetlands for conservation of priority amphibian species.

Variation of Photoperiod Regime during the American Bullfrog Tadpole Stage: Influence on Growth and Metamorphosis

AbstractIn culture of the American bullfrog Lithobates catesbeiana, photoperiod is a crucial factor affecting productivity success. Here, the objective was to determine the effect of three photoperiods (high light [HL] = 12 h light [L] : 12 h dark [D]; medium light [ML] = 10 h L : 14 h D; low light [LL] = 8 h L : 16 h D) with different application times on the performance of bullfrog tadpoles. Tadpoles at Gosner stage 25 were subjected to seven different treatments: the HL photoperiod for 90 d (HL90; control); ML for 45 d followed by HL for 45 d (ML45–HL45); LL for 45 d followed by HL for 45 d (LL45–HL45); ML for 60 d followed by HL for 30 d (ML60–HL30); LL for 60 d followed by HL for 30 d (LL60–HL30); LL for 30 d followed by ML and HL, each for 30 d (LL30–ML30–HL30); and ML for 30 d followed by LL and HL, each for 30 d (ML30–LL30–HL30). Response variables included growth, survival rate, feed conversion ratio, protein efficiency ratio, and metamorphosis rate. Likewise, the concentrations of thyroid hormones were established as explanatory variables. The results suggested that by implementing the ML60–HL30 treatment, a higher productive performance was obtained (growth [mean ± SD] = 7,318 ± 0.01 g; survival = 89.33 ± 1.7%; metamorphosis rate = 92.7 ± 1.1%) in relation to HL90 (growth = 7,027 ± 0.02 g; survival = 81.67 ± 2.05%; metamorphosis rate = 90.4 ± 1.7%). The information allows consideration of changes in bullfrog culture, establishing management plans inherent to the exposure times of the different photoperiods in order to obtain the highest performance.

Ecophysiological models for global invaders: Is Europe a big playground for the African clawed frog?

One principle threat prompting the worldwide decline of amphibians is the introduction of nonindigenous amphibians. The African Clawed Frog, Xenopus laevis, is now one of the widest distributed amphibians occurring on four continents with ongoing range expansion including large parts of Europe. Species distribution models (SDMs) are essential tools to predict the invasive risk of these species. Previous efforts have focused on correlative approaches but these can be vulnerable to extrapolation errors when projecting species' distributions in nonnative ranges. Recent developments emphasise more robust process-based models, which use physiological data like critical thermal limits and performance, or hybrid models using both approaches. Previous correlative SDMs predict different patterns in the potential future distribution of X. laevis in Europe, but it is likely that these models do not assess its full invasive potential. Based on physiological performance trials, we calculate size and temperature-dependent response surfaces, which are scaled to geographic performance layers matching the critical thermal limits. We then use these ecophysiological performance layers in a standard correlative SDM framework to predict the potential distribution in southern Africa and Europe. Physiological performance traits (standard metabolic rate and endurance time of adult frogs) are the main drivers for the predicted distribution, while the locomotor performance (maximum velocity and distance moved in 200 ms) of adults and tadpoles have low contributions.

Refining the activity level-predation risk paradigm in larval anuran communities

The activity level-predation risk paradigm of community assembly is based on observable trade-offs between activity level and predation risk. Many species that live in ephemeral habitats are relatively more active, grow faster, and metamorphose sooner than those in more permanent habitats, thus enabling them to survive by escaping drying ponds. Species with high activity levels are shown to be superior competitors in temporary ponds, but are at greater risk of predation by visually cued predators. We take a comprehensive approach to testing if the activity-predation paradigm drives community assembly of a four-species guild of larval anurans through field surveys and a series of laboratory experiments quantifying their activity level, anti-predatory responses, swim performance, and escape behavior. Activity level was a good predictor of susceptibility to predation and habitat association for most species in our study, but not all species fit the pattern. Secondary anti-predator mechanisms contributed to differences in susceptibility to predation. Some species were more capable of avoiding predation through swim performance and escape behavior, thus allowing them to occupy a greater range of the water permanency continuum than was predicted by activity level alone. Because performance traits are deeply rooted, evolutionary history plays a major role in determining tadpole performance and life-history traits. Whole-organism performance traits (e.g., swim performance, escape behavior) have not generally been considered in the classic activity-predation paradigm. Our results show that accounting for individual and species-level performance reveals the understudied, yet important role of species-specific performance traits in disentangling the mechanisms driving community assembly.

Effects of Heavy Metal Pollution on Fitness and Swimming Performance of Bufo raddei Tadpole.

Systematic studies on the impact of environmental pollution on the survival adaptability of amphibians are relatively few. In this study, Bufo raddei tadpoles from two places with totally different backgrounds of heavy metal pollution were chosen to explore the effects of heavy metal pollution on fitness and swimming performance of tadpoles, the physiological effects were investigated as well. The tadpoles at GS 25, GS 30 and GS 35 were collected randomly from the two study sites and were exposed to different environmental temperatures. The results showed that heavy metal enrichment and antioxidant levels were significantly higher in the tadpoles under long-term heavy metal stress. Meanwhile, heavy metal pollution affected the adaptability of tadpoles to environmental change and decreased the swimming performance of the tadpoles. Unexpected, the tadpoles from heavy metal-polluted area also showed some adaptive changes, mainly reflected in the increase in swimming endurance.

Smooth, striated, or rough: how substrate textures affect the feeding performance of tadpoles with different oral morphologies

For grazing animals that share spatial and alimentary resources, the relationship between differences in oral morphology and the physical properties of substrates can help explain how and where species forage. The substrates may require different efforts from animals to access and remove food from their surfaces. Variation in oral morphology may produce differences in animals’ feeding efficiency. We tested whether one substrate characteristic, the surface texture (i.e., smooth, striated and rough), influences the growth and food consumption rates of anuran larvae from nine species with different oral morphologies. Tadpoles with few keratinized oral structures and those with more gaps in the marginal papillae row were more efficient grazing on smooth and rough surfaces, respectively. This may indicate possible feeding specializations. Conversely, tadpoles with a high number of labial tooth rows, regardless of the number of gaps in these structures, and those with only a dorsal gap in the marginal papillae row were equally efficient feeding upon all substrate textures. Tadpoles with the generalized labial tooth row formula 2(2)/3(1), had higher growth rates than the other species, suggesting an adaptive significance for this common oral morphology. We demonstrated that species differ in feeding efficiency when grazing on substrates with different textures. This can help elucidate the adaptive significance of variation in tadpole oral morphology. We also provide insights on resource selection and niche partitioning among species, especially for those whose diets do not differ in quantity or quality, as it is common in anuran larval assemblages.

Effects of 2,4-D-based herbicide (DMA® 806) on sensitivity, respiration rates, energy reserves and behavior of tadpoles

Increased use of sugarcane pesticides and their destination to non-target environments in Brazil has generated concerns related to the conservation of more vulnerable groups, such as amphibians. Besides the high skin permeability, tadpoles are constantly restricted to small and ephemeral ponds, where exposure to high concentrations of pesticides in agricultural areas is inevitable. This study evaluated chronic effects caused by sub-lethal concentrations of 2,4-dichlorophenoxyacetic acid herbicide on energy storage, development, respiration rates, swimming performance and avoidance behavior of bullfrog tadpoles (Lithobates catesbeianus). Firstly, we conducted acute toxicity test (96 h) to estipulate sub-lethal concentrations of 2,4-D and evaluate the sensitivity of three tadpoles’ species to this herbicide. Results showed that Leptodactylus fuscus presented the lowest LC50 96 h, 28.81 mg/L, followed by Physalaemus nattereri (143.08 mg/L) and L. catesbeianus (574.52 mg/L). Chronic exposure to 2,4-D (125, 250 and 500 μg/L) delayed metamorphosis and inhibited the growth of tadpoles at concentrations of 125 μg/L. Effects on biochemical reserves showed that 2,4-D increased total hepatic lipids in tadpoles, although some individual lipid classes (e.g. free fatty acids and triglycerides) were reduced. Protein and carbohydrates contents were also impaired by 2,4-D, suggesting a disruption on energy metabolism of amphibians by the herbicide. In addition to biochemical changes, respiration rates and swimming speed were also decreased after chronic exposure to 2,4-D, and these responses appeared to be correlated with the changes detected in the basic energy content. Avoidance test indicated that tadpoles of L. catesbeinus avoided the presence of 2,4-D, however they were unable to detect increasing gradients of the contaminant. Our data showed that chronic exposure to 2,4-D impaired biochemical, physiological and behavioral aspects of tadpoles, which may compromise their health and make them more vulnerable to environmental stressors in natural systems.

Dealing with hot rocky environments: Critical thermal maxima and locomotor performance in Leptodactylus lithonaetes (Anura: Leptodactylidae)

Environmental temperature has fitness consequences on ectotherm development, ecology and behaviour. Amphibians are especially vulnerable because thermoregulation often trades with appropriate water balance. Although substantial research has evaluated the effect of temperature in amphibian locomotion and physiological limits, there is little information about amphibians living under extreme temperature conditions. Leptodactylus lithonaetes is a frog allegedly specialised to forage and breed on dark granitic outcrops and associated puddles, which reach environmental temperatures well above 40 ˚C. Adults can select thermally favourable microhabitats during the day while tadpoles are constrained to rock puddles and associated temperature fluctuations; we thus established microhabitat temperatures and tested whether the critical thermal maximum (CTmax) of L. lithonaetes is higher in tadpoles compared to adults. In addition, we evaluated the effect of water temperature on locomotor performance of tadpoles. Contrary to our expectations, puddle temperatures were comparable and even lower than those temperatures measured in the microhabitats used by adults in the daytime. Nonetheless, the CTmax was 42.3 ˚C for tadpoles and 39.7 ˚C for adults. Regarding locomotor performance, maximum speed and maximum distance travelled by tadpoles peaked around 34 ˚C, approximately 1 ˚C below the maximum puddle temperatures registered in the puddles. In conclusion, L. lithonaetes tadpoles have a higher CTmax compared to adults, suggesting a longer exposure to extreme temperatures that lead to maintain their physiological performance at high temperatures. We suggest that these conditions are adaptations to face the strong selection forces driven by this granitic habitat.

单独隔离孵化对镇海林蛙蝌蚪生长发育、社交行为和运动表现的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 单独隔离孵化对镇海林蛙蝌蚪生长发育、社交行为和运动表现的影响 DOI: 10.5846/stxb201802120365 作者: 作者单位: 南京师范大学生命科学学院,南京师范大学生命科学学院,丽水学院生态学院,丽水学院生态学院,丽水学院生态学院,丽水学院生态学院,丽水学院生态学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31270443）；丽水市科技局重点研发计划项目（20150406，SH2017001） Effects of isolated-incubation embryos on the growth, development, social behavior, and locomotor performance of Rana zhenhaiensis tadpoles Author: Affiliation: College of Life Sciences,Nanjing Normal University,College of Life Sciences,Nanjing Normal University,College of Ecology,Lishui University,College of Ecology,Lishui University,College of Ecology,Lishui University,College of Ecology,Lishui University,College of Ecology,Lishui University Fund Project: The National Natural Science Foundation of China (General Program) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:两栖类胚胎呈卵群一起孵化在反捕食、维持胚胎间的温度平衡和促进胚胎的同步发育等方面具有重要作用。在实验条件下探究孵化条件（单独隔离孵化和卵群一起孵化）对镇海林蛙（Rana zhenhaiensis）蝌蚪的生长发育、社交行为及其运动表现能力的影响。结果表明，孵出2天后，单独隔离孵化组蝌蚪的体长和发育历期均显著大于卵群一起孵化组。以体长为协变量的协方差分析表明，特定体长的单独隔离孵化组蝌蚪的体宽和体重均显著大于卵群一起孵化组的个体。在蝌蚪的活动行为中，单独隔离孵化组蝌蚪在水体上层和中层出现的频次显著小于卵群一起孵化组，而在水体底层的出现频次显著大于卵群一起孵化组。单独隔离孵化组蝌蚪个体的分布面积率、最近邻个体的距离、个体间的距离均显著大于卵群一起孵化组，但个体间的接触频次显著小于卵群一起孵化组。在运动表现方面，单独隔离孵化组胚胎的摆尾搏动频次显著小于卵群一起孵化组。单独隔离孵化组蝌蚪的运动时长和运动频次均显著小于卵群一起孵化组。本研究结果将为无尾两栖类幼期的生长发育规律提供参考数据。 Abstract:Embryo-clustering incubation plays an important role in anti-predation, maintaining temperature balance between embryos, and promoting hatching synchrony for anurans. In this study, we investigated the effects of two hatching conditions (isolated-incubation and clustered-incubation) on the growth, development, social behavior, and locomotor performance of Rana zhenhaiensis tadpoles under laboratory conditions. Our results showed that both body length and the Gosner development stage of two-day-old hatchlings in a single-embryo treatment were significantly larger than those of the group-embryo treatment. The results of the ANCOVA (with body length as the covariate) analysis showed that both body width and body mass in the group-embryo treatment were significantly lower than those of the single-embryo treatment. For tadpole activity behavior, the occurrence frequency in the upper and middle water layers in the single-embryo treatments were significantly lower than those of the group-embryo treatment, whereas it was significantly greater in the single-embryo treatments than that of the group-embryo treatment in the lower water layers. The proportion of area occupied by tadpoles, the nearest neighbor distance, and the distance among individuals in the single-embryo treatment were both significantly greater than those of the group-embryo treatment, but the contact frequency between pairwise tadpoles was significantly lower than those of the group-embryo treatment. Regarding locomotor performance, we found that activity duration and activity frequency in the single-embryo treatment were significantly lower than those of the group-embryo treatment. These findings should provide valuable reference data on the growth and development of Rana zhenhaiensis, as well as other anuran species. 参考文献 相似文献 引证文献

Investigation of Growth Performance and Survival Rate of Pelophylax ridibundus Tadpoles Reared in Different Stock Densities

Bu çalışmada, en iyi büyüme performansının ve yaşama oranının belirlenmesi için Pelophylax ridibundus iribaşları farklı stok yoğunluklarında yetiştirilmiştir. İribaşlar stok yoğunluklarına göre A (0.5 iribaş /L), B (1 iribaş /L) ve C (1.5 iribaş /L) olarak gruplandırılmıştır. Bu deney, başlangıç ağırlığı 0.013 ± 0.01 g ve başlangıç uzunluğu 7.54 ± 0.06 mm olan ortalama 180 iribaş ile 60 gün boyunca gerçekleştirilmiştir. İribaşlar, % 39 ham protein içeren yem ile günde iki kez beslenmiştir. 30 litrelik yetiştirme kaplarında bulunan su (20 litre), oksijen gerekliliği için her 24 saatte bir değiştirilmiştir. Boy, ağırlık kazancı ve yaşama oranı tespiti için iki haftada bir ölçüm yapılmıştır. Stok yoğunluğunun boy ve ağırlık kazancı üzerindeki ters orantılı etkileri gözlenmiştir. Çalışma sonucunda, en düşük stok yoğunluğuna sahip A grubunda (0.5 iribaş /L); boyca ve ağırlıkça en iyi büyüme ile en yüksek yaşama oranı (% 90) tespit edilmiştir.

Stage-specific effects of fire: Effects of prescribed burning on adult abundance, oviposition habitat selection, and larval performance of Cope’s Gray Treefrog (Hyla chrysoscelis)

To effectively manage landscapes that support species with complex life cycles, managers should consider how current practices affect habitats these organisms rely on in each life stage. Prescribed fire is a landscape level disturbance that may alter both aquatic and terrestrial habitat characteristics. However, our knowledge of the effects of fire on amphibians is primarily limited to adult responses in terrestrial habitats. Here we present an integrated approach to test the response of Cope’s Gray Treefrogs (Hyla chrysoscelis) to fire across terrestrial and aquatic habitats by examining responses in tadpole performance and survivorship, adult abundance, and oviposition choice. In a common garden experiment, tadpoles reared with unburned leaf litter grew much faster those in pools with burned litter. To determine how fire in terrestrial and aquatic habitats acts to shape oviposition choice, we embedded aquatic mesocosms containing a substrate of either burned or unburned leaf litter within burned and unburned terrestrial plots. Observed oviposition was an order of magnitude higher in unburned terrestrial plots, regardless of the aquatic leaf litter treatment. This trend was not driven by differences in adult abundance in burned and unburned plots. Our findings are consistent with a scenario where adult treefrogs use terrestrial cues to preferentially breed in aquatic sites in unburned landscapes where tadpoles also experience greater growth. These insights highlight the value of adopting a multi-scale integrative approach that links stage and habitat specific effects on abundance, behavior, and performance to understanding the effects of anthropogenic and natural stressors on animal with complex life cycles.

Sunlight-induced genotoxicity and damage in keratin structures decrease tadpole performance

The increased incidence of solar ultraviolet (UV) radiation, an environmental genotoxic agent, due to ozone depletion or deforestation may help to explain the enigmatic decline of amphibian populations in specific localities. In this work, we evaluated the importance of DNA repair performed by photolyases to maintain the performance of treefrog tadpoles after acute and chronic treatments with environmental-simulated doses of solar UVB and UVA radiation. Immediately after UV treatments, tadpoles were exposed to a visible light source to activate photolyases or kept in dark containers. The biological effects of UV treatments were evaluated through morphological, histological, locomotor and survival analyzes of Boana pulchella tadpoles (Anura: Hylidae). The results indicate that tadpole body weight suffered influence after both UVB and UVA treatments, although the body length was bit affected. The locomotor performance of UVB-exposed tadpoles was significantly reduced. In addition, UVB radiation induced a severe impact on tadpole skin, as well as on keratinized structures of mouth (tooth rows and jaw), indicating that these should be important effects of solar UV radiation in the reduction of tadpole performance. Furthermore, photolyases activation was fundamental for the maintenance of tadpole performance after chronic UVB exposures, but it was relatively inefficient after acute exposures to UVB, but not to UVA radiation. Therefore, this work demonstrates how the UV-induced genotoxicity and structural alterations in the skin and oral apparatus affect tadpole performance and survival.

Mechanisms underlying the occurrence of species in complex modified tropical landscapes: a case study of amphibians in the Osa Peninsula, Costa Rica

Abstract:The mechanisms underlying occupancy patterns of species in modified tropical landscapes are poorly understood. The presence of adults in a modified habitat may not necessarily indicate the quality of the habitat for sub-adult stages. These issues were addressed by examining patterns in breeding-site use by adult frogs and tadpole performance across a pasture-forest gradient in the Osa Peninsula, Costa Rica. The use of artificial pools by adult frogs for breeding activity was quantified along three transects, with a pool located at the edge (0 m) and 10, 30 and 50 m into forest and pasture. Next, survival, size at metamorphosis and time to metamorphosis were quantified for tadpoles of Engyptomops pustulosus and Dendrobates auratus in artificial pools at the edge, pasture and forest. Adult frogs used breeding pools non-randomly; two species used pools only in pasture, whereas three species used pools only in forest. In addition, Smilisca phaeota used pools in pasture and at the edge while E. pustulosus used pools across the pasture-forest gradient. The habitat where adults used breeding pools generally also yielded high performance of their tadpoles, with some exceptions. Tadpole survival to metamorphosis was low in pastures (<5%) and higher in edge and forest (>18%) for D. auratus; in contrast, survival of E. pustulosus was over 80% in each habitat. Metamorphs of D. auratus were largest in edges but larval period did not differ among habitats. Metamorphs of E. pustulosus were 18% larger and larval period was 27% shorter in pastures compared with forest. These results suggest that modified habitats represent an ecological jackpot for some species, such that offspring performance is enhanced compared with that in forest habitat. Populations of other species may be restricted to forest habitat because of intolerable abiotic conditions in modified habitats. The results of this study indicate that adult breeding site use and tadpole performance contribute to mechanisms that underlie patterns of species occupancy in modified tropical landscapes.