Tadpole Activity Research Articles

Freshwater salinization and the evolved tolerance of amphibians.

The increasing salinization of freshwaters is a growing environmental issue as a result of mining, agriculture, climate change, and the application of de-icing salts in regions that experience ice and snow. Due to narrow osmotic limits, many freshwater species are particularly susceptible to salinization, but it is possible that repeated exposures over time could favor the evolution of increased salt tolerance. Using collected nine populations of larval wood frogs (Rana sylvatica) as eggs from ponds and wetlands with close proximity to roads and spanning a wide gradient of salt concentrations. In the first experiment, we used a time-to-death experiment to examine the salt tolerance. In a second experiment, we examined whether population differences in salt tolerance were associated with trade-offs in growth, development, or behavior in the presence of control water or a sublethal salt concentration. We found that populations collected from ponds with low and intermediate salt concentrations exhibited similar tolerance curves over a 96-h exposure. However, the population from a pond with the highest salt concentration exhibited a much higher tolerance. We also found population differences in growth, development, and activity level among the populations, but these were not associated with population differences in tolerance. In addition, the sublethal concentration of salt had no impact on growth and development, but it did cause a reduction in tadpole activity across the populations. Collectively, these results provide further evidence that some species of freshwater organisms can evolve tolerance to increasing salinization, although it may only occur under relatively high concentrations and without trade-offs in growth, development, or behavior.

Effects of metolachlor and fish cues on tadpole antipredator behaviors

Antipredator behaviors are often crucial for animal survival. In environments impacted by humans, animals may be exposed to a wide array of chemical contaminants due to agriculture, industry, and other activities. Among other effects, these chemical contaminants may influence behaviors prey animals use to cope with predation risk, likely reducing survival by suppressing or even maladaptively reversing normal behavioral responses. Changes in behavioral responses could be the result of impaired detection of cues that indicate predator presence or altered behavioral plasticity in response to predator cues. In a laboratory experiment, we tested the effects of the commonly used herbicide metolachlor on the behavior of tadpoles of the American bullfrog (Lithobates catesbeianus) in both the absence and presence of water conditioned with cues (odor) of fish. We observed several behaviors in the tadpoles reflective of predator avoidance when exposed to combinations of metolachlor (0 or 80 ppb) and the presence or absence of fish cues. We found that metolachlor had size-dependent effects on tadpole activity levels, with larger tadpoles being much less active in the absence of metolachlor but similar in activity to small tadpoles when metolachlor was present. Fish cues similarly had size-dependent effects on multiple tadpole behaviors. Finally, hiding behavior and zone change (movement) behavior of tadpoles in response to fish cues varied depending on the presence of metolachlor and, in the case of zone changes, tadpole size. Our findings indicate that the presence of chemical contaminants has the potential to alter important antipredator behaviors. However, these effects are complex, and size may mediate the nature of the response to both chemical contaminants and predators.

Dietary tannins alter growth, behavior, and the gut microbiome of larval amphibians.

Research has shown that leached plant toxins negatively impact the growth and development of larval amphibians. However, tadpoles may encounter these same toxins in food material, and differential exposure routes and distribution of toxic chemicals can yield variable downstream effects on animals. To date, most research understanding the interactions between dietary plant toxins and herbivores has been conducted in terrestrial systems. Despite the abundance of plant toxins in food and water sources, the effects of dietary plant toxins on larval amphibians have not been studied, and tannins could negatively affect these species. Here, green frog tadpoles (Lithobates clamitans) were fed diets with or without 2% tannic acid to test how their growth, development, behavior, and gut microbiome respond to dietary tannins. At the end of the trial, we conducted a behavioral assay to measure tadpole activity and boldness and inventoried the gut microbiome using 16S rRNA sequencing. Dietary tannins significantly decreased body mass by 66% and length by 28%, without influencing tadpole developmental stage. We found significant differences in exploratory behavior and boldness during the first minute of our behavioral assay, demonstrating that tannins have the potential to influence behavior during novel or stressful events. Finally, tannins significantly sculpted the gut microbiome, with an increase in the measurement of Shannon entropy. We observed 7 microbial phyla and 153 microbial genera that exhibited significantly differential abundances differences between control and tannic acid-fed tadpoles. Collectively, our results demonstrate that dietary tannins have the potential to alter amphibian growth, behavior, and microbiome.

Visual environment of rearing sites affects larval response to perceived risk in poison frogs.

Turbidity challenges the visual performance of aquatic animals. Here, we use the natural diversity of ephemeral rearing sites occupied by tadpoles of two poison frog species to explore the relationship between environments with limited visibility and individual response to perceived risk. To compare how species with diverse natural histories respond to risk after developing in a range of photic environments, we sampled wild tadpoles of (1) Dendrobates tinctorius, a rearing-site generalist with facultatively cannibalistic tadpoles and (2) Oophaga pumilio, a small-pool specialist dependent on maternal food-provisioning. Using experimental arenas, we measured tadpole activity and space use first on a black and white background, and then on either black or white backgrounds where tadpoles were exposed to potentially predatory visual stimuli. The effects of rearing environment on D. tinctorius tadpoles were clear: tadpoles from darker pools were less active than tadpoles from brighter pools and did not respond to the visual stimuli, whereas tadpoles from brighter pools swam more when paired with conspecifics versus predatory insect larvae, suggesting that tadpoles can visually discriminate between predators. For O. pumilio, tadpoles were more active on experimental backgrounds that more closely matched the luminosity of their rearing sites, but their responses to the two visual stimuli did not differ. Larval specialisation associated with species-specific microhabitats may underlie the observed responses to visual stimuli. Our findings demonstrate that light availability in wild larval rearing conditions influences risk perception in novel contexts, and provides insight into how visually guided animals may respond to sudden environmental disturbances.

Multimodal Cues Do Not Improve Predator Recognition in Green Toad Tadpoles.

Simple SummaryTadpoles are known to use their sense of smell to detect the presence of predators, but some studies showed their reliance on vision during social interaction, suggesting that vision might have a role in predatory contexts as well. Here, we investigated how chemical or visual cues of a native predator, or a combination of both, influence the defensive behaviour of green toad tadpoles. We expected tadpoles to reduce their activity when exposed to chemical cues and avoid the area of the experimental arena near to the caged predator when exposed to the visual ones. With both cues, we expected tadpoles to show both responses and with greater intensity. Our results indicate that visual cues alone do not elicit any apparent defensive response, suggesting that tadpoles mainly rely on chemical cues to assess predation risk.The anti-predator behaviour of green toad (Bufotes balearicus) tadpoles was investigated by exposing them to only the visual or chemical cues, or a combination of both, of a native predator, southern hawker Aeshna cyanea. We collected green toad egg strings in the field and tadpoles did not receive any predatory stimulus before the onset of the experiment. To manipulate chemical and visual cues independently, dragonfly larvae were caged inside a transparent plastic container, while chemical cues (odour of tadpole-fed dragonfly larvae) were injected into the surrounding arena. An empty container and water were used, respectively, as controls. The behaviour of individually tested tadpoles was videorecorded for 40 min, of which 20 were before their exposure to stimuli. Five second-distance frames were compared to assess both tadpole activity and position within the arena with respect to the visual stimulus. The tadpole level of activity strongly decreased after exposure to either chemical cues alone or in combination with visual cues, while visual cues alone apparently did not elicit any defensive response. The position of tadpoles inside the arena was not affected by visual cues, suggesting that green toad tadpoles mainly rely on olfactory cues to assess the level of predation risk.

Influence of check dams on the activity pattern and morphometric traits of overwintering tadpoles in the Western Himalaya

Delaying metamorphosis in low-temperature conditions by anuran larvae known as ‘overwintering’ have been poorly studied, especially in terms of habitat ecology and behavioural aspects. The present study investigates some of the ecological aspects of overwintering tadpoles of the genus Nanorana in the Western Himalaya in an anthropogenically modified stream where check dams have altered the natural habitat, which can potentially influence the amphibian ecology. We present insights on the influence of check dams on the tadpole activity pattern and morphometric traits useful in the conservation planning of the narrowly distributed and understudied species, which are most sensitive to habitat modification.We monitored natural and modified pool habitats in the stream during winter and post-winter seasons based on the visual density of tadpoles to assess the diurnal and seasonal emergence pattern with associated habitat variables. Generalized Linear Mixed Modeling (GLMM) was used to understand the influence of various habitat variables on the visible density of tadpoles. Fine-scale temporal scan sampling of tadpoles was carried out to complement the understanding of the visible density variation and analyzed using circular plots and activity overlap estimation. Variation in morphometric traits was assessed using field morphometry and photogrammetry.Mean tadpole visible density at nighttime was higher in modified pools than natural pools during winter, but there was no statistically significant difference during daytime; the nocturnal pattern changed in the post-winter, where visible density was higher in natural pools. Tadpole visible density was influenced by the interaction of mean canopy cover with water temperature, instream cover items richness, mean canopy cover percentage, water temperature, leaf litter depth, water velocity and interaction of time of the day with pool modification. Tadpole activity patterns varied significantly between pool types during post-winter, where modified pool population increased daytime activity and thus the activity overlap reduced from winter (90.8%) to post-winter (64.5%). During both seasons, the mean body size of the natural pool population was significantly lower than the modified pool population; mean relative tail length was significantly lower in natural pools during post-winter; mean tail depth was significantly lower in natural pools during winter.The study presents evidence of the influence of anthropogenic habitat alterations on behaviour and morphometric traits of overwintering tadpoles, which needs to be further investigated. We also discuss the variation in nocturnal emergence, habitat selection and morphometric trait patterns in the modified habitat, potential reasons and similar behaviour in other aquatic organisms, which need to be considered while developing conservation strategies for the overwintering tadpoles in the region.

Naive poison frog tadpoles use bi-modal cues to avoid insect predators but not heterospecific predatory tadpoles.

ABSTRACTFor animals to survive until reproduction, it is crucial that juveniles successfully detect potential predators and respond with appropriate behavior. The recognition of cues originating from predators can be innate or learned. Cues of various modalities might be used alone or in multi-modal combinations to detect and distinguish predators but studies investigating multi-modal integration in predator avoidance are scarce. Here, we used wild, naive tadpoles of the Neotropical poison frog Allobates femoralis ( Boulenger, 1884) to test their reaction to cues with two modalities from two different sympatrically occurring potential predators: heterospecific predatory Dendrobates tinctorius tadpoles and dragonfly larvae. We presented A. femoralis tadpoles with olfactory or visual cues, or a combination of the two, and compared their reaction to a water control in a between-individual design. In our trials, A. femoralis tadpoles reacted to multi-modal stimuli (a combination of visual and chemical information) originating from dragonfly larvae with avoidance but showed no reaction to uni-modal cues or cues from heterospecific tadpoles. In addition, visual cues from conspecifics increased swimming activity while cues from predators had no effect on tadpole activity. Our results show that A. femoralis tadpoles can innately recognize some predators and probably need both visual and chemical information to effectively avoid them. This is the first study looking at anti-predator behavior in poison frog tadpoles. We discuss how parental care might influence the expression of predator avoidance responses in tadpoles.

Phylogenetic patterns of trait and trait plasticity evolution: Insights from tadpoles.

Environmental heterogeneity has led to the widespread evolution of phenotypic plasticity in all taxonomic groups. Although phenotypic plasticity has been examined from multiple perspectives, few studies have examined evolutionary patterns of plasticity within a phylogeny. We conducted common-garden experiments on 20 species of tadpoles, spanning three families, exposed for 4 weeks to a control, predator cues, or reduced food (i.e., increased intraspecific competition). We quantified tadpole activity, growth, and relative morphology and found widespread differences in species responses to predator cues and reduced food. We detected pervasive phylogenetic signals in traits within each environment, but the phylogenetic signal was much less common in the trait plasticities. Among different models of continuous character evolution, Brownian Motion and Ornstein Uhlenbeck models provided better fits to the data than the Early Burst model. Tadpole activity level in predator environments had much higher evolutionary rates than in the control and reduced-food environments; we did not see this pattern in the other traits. In comparing traits versus trait plasticities, activity evolved much faster than the plasticity of activity whereas morphological traits evolved much slower than morphological plasticities. Collectively, these results suggest that traits and trait plasticities can exhibit dramatically different evolutionary patterns.

Effects of conspecific density on tadpole risk assessment and defensive behaviour

Abstract Prey species assess predation risk by using either direct and indirect cues and both may contribute to a proper evaluation of the actual risk. As postulated by the risk assessment hypothesis, conspecific density may also provide useful information for tuning defensive responses. We tested this hypothesis using a combination of five density levels (1, 2, 4, 8 and 16 individuals) of Italian agile frog Rana latastei tadpoles and three treatments (control, predatory cues of common backswimmer Notonecta glauca and a waterjet of tap water as mechanical disturbance). Tadpole activity decreased in response to all stimuli but, as expected, backswimmer cues induced a stronger and lasting response. However, tadpole activity level did not vary with group size, thus providing no support for the risk assessment hypothesis and confirming that conspecific density might have less consistent effects on short-term behavioural responses than morphological and life history traits.

Dendropsophus minutus (Hylidae) tadpole evaluation of predation risk by fishing spiders (Thaumasia sp.: Pisauridae) is modulated by size and social environment

Predator–prey interactions can cross ecosystem boundaries and the outcome of these interactions is seen in prey defensive behavior. We aimed to test how the presence of a semi-aquatic predator alters the behavior and foraging microhabitat of Dendropsophus minutus tadpoles when they are either in groups or alone. We hypothesized that in the presence of a predator, Thaumasia fishing spider, tadpoles will be (1) less active; (2) forage far from the predator and; (3) forage evenly when in groups. We measured activity and foraging microhabitat as the proportion of time spent moving, and the total percentage of food removed from the upper and lower inner surfaces of the aquarium, respectively. The presence of the spider reduced tadpole activity by 24% compared to treatments without predators. Contrary to our expectations, solitary tadpoles were 34% more active than tadpoles in groups, and larger larvae were less active than smaller ones. The presence of the fishing spider decreased tadpoles activity, but the presence of conspecifics did not dilute the predator effect. Larger larvae are under more substantial selective pressure than smaller ones. Finally, our experiment empirically demonstrates that predator effects are transferable, generating a cascading system, and affecting the recipient ecosystem in various manners.

Behavioral Changes in Tadpoles of the Antillean White Lipped Frog (Leptodactylus albilabris) in the Presence of a Predator: Habitat Use Preference and Activity Levels

This study is based on the behavioral responses of Leptodactylus albilabris tadpoles, a widely abundant frog native to Puerto Rico. We evaluated changes in habitat preference and activity levels in the presence of a predator (fish). Tadpoles were collected and allocated to one of three treatments: no fish predator, one fish (Astronotus ocellatus), and two fish. Results showed a significant decrease in activity levels of tadpoles and change in microhabitat use in the presence of a predator. However, there was no significant difference in tadpole activity when the second predator was added. The preferred habitat in the presence of a predator was leaf litter, even though L. albilabris tadpoles are benthic and usually favor hiding in the sediment. The larval stage of the anuran life cycle is the most vulnerable, and these changes in behavior increase the probability of escaping predators to reach metamorphosis and finally reproduce.

Effects of two little-studied environmental pollutants on early development in anurans

Despite intensive ecotoxicological research, we still know relatively little about the ecological impacts of many environmental contaminants. Filling these knowledge gaps is particularly important regarding amphibians, because they play significant roles in freshwater and terrestrial ecosystems, and their populations are declining worldwide. In this study, we investigated two pollutants that have been poorly studied in ecotoxicology despite their widespread occurrence in surface waters: the herbicide terbuthylazine and the pharmaceutical drug carbamazepine. We exposed two anuran species throughout their larval development to each of two environmentally relevant concentrations of each pollutant, and recorded mortality and 17 sub-lethal endpoints up to several months after exposure. Mortality was low and unrelated to treatment. In agile frogs (Rana dalmatina), we found that treatment with 0.3 μg/L terbuthylazine decreased tadpole activity and reduced fat bodies in juveniles, whereas treatment with 50 μg/L carbamazepine decreased spleen size and increased spleen pigmentation. In common toads (Bufo bufo), treatment with 0.003 μg/L terbuthylazine increased body mass at metamorphosis, treatment with 0.3 μg/L terbuthylazine increased the size of optic tecta, and treatment with 0.5 μg/L carbamazepine decreased hypothalamus size. Treatment with 50 μg/L carbamazepine reduced the feeding activity of toad tadpoles, decreased their production of anti-predatory bufadienolide toxins, and increased their body mass at metamorphosis; juvenile toads in this treatment group had reduced spleen pigmentation. Neither treatments affected the time to metamorphosis, post-metamorphic body mass, or sex ratios significantly. These results show that environmental levels of both terbuthylazine and carbamazepine can have several sub-lethal effects on anurans, which may be detrimental to individual fitness and population persistence in natural conditions. Our findings further highlight that toxic effects cannot be generalized between chemicals of similar structure, because the terbuthylazine effects we found do not conform with previously reported effects of atrazine, a related and extensively studied herbicide.

The effects of traffic noise on tadpole behavior and development

Traffic noise is known to negatively affect many wildlife species by interfering with foraging behavior. Frogs often lay their eggs in roadside ditches because they are predator-free, but it is possible that traffic noise could reduce the survival and fitness of tadpoles, creating an ecological trap. In a series of lab experiments, we tested whether traffic noise has a negative impact on tadpole feeding behavior, whether this is mediated by changes in tadpole activity, and whether there is any impact on tadpole growth rate or metamorphosis. Traffic noise exposure significantly reduced the amount of food consumed by Cuban Treefrog (Osteopilus septentrionalis) tadpoles. Traffic noise exposure also increased the activity level of both Southern Toad (Anaxyrus terrestris) and Cuban Treefrog tadpoles, which could possibly make them more noticeable to predators in the wild. However, these behavioral changes were not associated with changes in growth rate or timing of metamorphosis. We caution, however, that this study aimed to isolate the specific impact of traffic noise, and did not investigate other road effects that may be damaging to tadpoles.

The impact of elevated temperature and CO2 on growth, physiological and immune responses of Polypedates cruciger (common hourglass tree frog)

BackgroundAmphibians are one of the most susceptible groups to climate change as their development occurs in aquatic environments or in microhabitats with high humidity. Accordingly, our primary objective was to investigate the chronic physiological responses seen in early larval to adult stages of Polypedates cruciger (Common hourglass tree frog) to future climate change based on continuous exposure to elevated temperature and elevated CO2 -induced low water pH. Free-swimming and free-feeding tadpoles were observed until metamorphosis under four experimental treatments; two elevated temperatures, one elevated CO2 (reduced pH) and a control maintained at ambient temperature (29 °C ± 1 °C) and CO2 (pH = 7). Elevated temperature treatments were maintained at 32 °C ± 0.5 °C and 34 °C ± 0.5 °C to represent respectively, the future climate scenarios RCP2.6 (Representative Concentration Pathway 2.6, the ‘base-case’ scenario) and RCP8.5 (‘business-as-usual’ scenario) according to the 5th Assessment Report of the IPCC. Elevated CO2 treatment was maintained within the pH range of 5.5–5.6 representing the range expected between RCP8.5 and RCP2.6.ResultsCompared to the control, elevated CO2 accelerated phenological progression of tadpoles through Gosner stages, thus resulting in lower body size at metamorphosis. Both elevated temperatures significantly delayed the development and reduced the growth of tadpoles. 100% mortality was observed in 34 °C treatment before metamorphosis (before Gosner stage 36) while all the tadpoles died after metamorphosis (at Gosner stage 46) in 32 °C treatment. Elevated CO2 increased tadpole activity, in terms of their swimming speed, while both of the elevated temperatures reduced it compared to the control. Catalase activity increased at elevated CO2. Ammonia excretion by tadpoles was decreased by elevated CO2, but increased under temperature elevation. Both Elevated CO2 and temperature treatments reduced the white blood cell count and its percentage of thrombocytes. Percentages of lymphocytes, monocytes and neutrophils were increased at 32 °C, while lymphocyte percentage and lysozyme activity were increased at elevated CO2. Several deformities were observed in tadpoles at elevated temperature and CO2.ConclusionsElevated temperatures and reduced pH due to elevated CO2, being major features of climate change, increase the vulnerability of amphibians, who are already one of the most threatened vertebrate groups. Based on our observations on the model amphibian species P. cruciger, increased vulnerability to climate change occurs by reducing their growth, body size and motility while also reducing their immunity and inducing physical deformities. These impacts are highly-likely to reduce the foraging, competitive and reproductive capabilities in their natural habitats. We conclude further that even the ‘best-case’ scenario of future climate change can impose significant physiological impacts that could threaten amphibian populations on broader spatial and temporal scales.Graphical abstract

Coexposure to environmental concentrations of cis-bifenthrin and graphene oxide: Adverse effects on the nervous system during metamorphic development of Xenopus laevis

Despite the great concerns associated with the combined biological effects of nanoparticles and insecticides, the current understanding of the corresponding ecological risks remains limited. Xenopus laevis (X. laevis) tadpoles were exposed to various concentrations of typical pyrethroid (cis-bifenthrin; cis-BF), either alone or in combination with graphene oxide (GO), for 21 days. The presence of GO resulted in increased bioconcentration of cis-BF and a higher 1S-enantiomer fraction. Exposure to cis-BF and GO caused further reduction in pre-metamorphic developmental rates and activated dopaminergic, noradrenergic, and serotonergic neurotransmitter systems. Reduced tadpole activity and levels of genomic DNA methylation at cytosine nucleotides (5hmC) were observed in the coexposure groups. These results indicate that GO enhance the bioconcentration of cis-BF and promote the conversion of its 1R-enantiomer to the 1S form, which lead to disruption of neurotransmitter systems as well as interference in metamorphic development.

Temporal variation in behavioral responses to dietary cues from a gape‐limited predator in tadpole prey: A test of the phylogenetic relatedness hypothesis

AbstractThe ability of prey to recognize and adequately respond to predators determines their survival. Predator‐borne, post‐digestion dietary cues represent essential information for prey about the identity and the level of risk posed by predators. The phylogenetic relatedness hypothesis posits that prey should respond strongly to dietary cues from closely related heterospecifics but respond weakly to such cues from distantly related prey, following a hierarchical pattern. While such responses have mostly been observed in prey at their first encounter with predators, whether prey maintain such hierarchical levels of investment through time remains unclear. We investigated this question by exposing Rhacophorus arboreus tadpoles to the non‐consumptive effect of gape‐limited newt predators Cynops pyrrhogaster that were fed one of five prey diets across a gradient of phylogenetic relatedness: frog tadpoles (Rhacophorus arboreus, Rhacophorus schlegelii, Pelophylax nigromaculatus, and Hyla japonica) and medaka fish (Oryzias latipes). Predators’ diet, time, and their interaction significantly influenced tadpole activity level. We found support for the phylogenetic relatedness hypothesis: Investments in defense were stronger to cues from tadpole diets than to cues from fish diet. However, such a hierarchical response was recorded only in the first four days following predator exposure, then gradually disappear by day 8 on which the tadpoles exhibited similar activity level across all predator treatments. The findings suggest that, at least under the threat of gape‐limited predators, prey use phylogenetic information to evaluate risk and appropriately invest in defense during early encounters with predators; however, energy requirements may prevent prey from maintaining a high level of defense over long exposure to predation risk.

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

Effect of pond dye on the response of Southern Leopard Frog tadpoles (<em>Lithobates sphenocephalus</em>) to Western Mosquitofish (<em>Gambusia affinis</em>) cues

Pollutant exposure can affect tadpole activity or affect their ability to respond to predator cues. One commonly used chemical in aquatic ecosystems, particularly those in suburban or rural areas, are dyes used to color or tint pond water. Little is known about how such dyes impact amphibians. We examined the effects of Tetra Pond Water Shade pond dye on the activity and behavioural response of Southern Leopard Frog (Lithobates sphenocephalus) tadpoles to cues from a potential predator, the Western Mosquitofish (Gambusia affinis). Tadpoles of L. sphenocephalus reduced activity after exposure to cues from G. affinis. The pond dye did not affect the activity or response of L. sphenocephalus tadpoles to G. affinis cues. Our results suggest little impact of this dye on the behavior of L. sphenocephalus at concentrations up to twice the recommended usage.

Resource-dependent temporal changes in antipredator behavior of common toad (Bufo bufo) tadpoles

Inducible behavioral defenses against predators, and how environmental factors mediate such responses, have been the focus of behavioral ecological research for decades. However, results often remained contradictory, perhaps because the ontogenetic context was ignored. Here, we investigated how antipredator behavioral responses of common toad (Bufo bufo) tadpoles are affected by food limitation and how the mediated responses changed during larval development. We raised tadpoles in the presence or absence of chemical cues indicating predation risk, combined with low or high food levels, and repeatedly monitored tadpole activity and visibility. We found that the presence of cues indicating predation risk and resource availability interactively affected visibility, but not relative activity, and this interactive effect changed with time over the larval period. Visibility of tadpoles decreased with time but to a greater extent when tadpoles were exposed to cues indicating predation risk compared to control groups, and this difference was more expressed when food was limited. Activity of tadpoles also decreased during larval development but to a greater extent in case of tadpoles raised in resource-limited environment compared to the other treatments. Also, activity of tadpoles was higher when food was scarce; however, the magnitude of this effect was not influenced by the predator-cue treatment. Thus, in addition to describing the trajectories of ontogenetic changes in tadpole behavior, our study also demonstrated that responses to environmental factors, such as predation threat and food availability, vary with age. Antipredator behavior is a common phenomenon in nature, and its expression is known to be influenced by the amount of available resources. How such defensive responses change with age, however, has been studied barely. By repeatedly observing common toad (Bufo bufo) tadpoles exposed to predators and/or food limitation, we found that tadpoles’ activity and visibility decreased with age and did so to a greater extent when tadpoles were exposed to chemical cues indicating predation risk compared to control groups. Our study demonstrated how responses to environmental factors, such as predation threat and food availability, vary with age in an important amphibian model species. These results draw attention to the importance of considering age when studying behavioral responses to environmental change and provide a possible explanation for some inconsistencies in the relevant literature.

Time-lagged effect of predators on tadpole behaviour and parasite infection.

Prey should adjust their defences against natural enemies to match their current level of risk and balance other needs. This is particularly important when optimal defences represent trade-offs, as is the case with many predator-induced trait-mediated indirect effects (TMIEs) that are antagonistic to those promoting host resistance to parasites and pathogens. However, trade-offs may depend on whether different natural enemies are present simultaneously or represent temporally discrete threats. We found that larval amphibians (Anaxyrus americanus) previously exposed to predator cues did not engage in anti-parasite behaviours (activity increases) in response to a current risk of infection by a pathogenic trematode parasite compared to controls, resulting in higher infection intensities. This suggests that the memory of the likely more lethal threat (predation) had greater influence, maladaptively dampening tadpole activity. Incorporating complexity inherent in natural systems, including spatial and temporal overlap, is necessary to better understand natural enemy ecology and how TMIEs relate to infectious diseases.