Large Tadpoles Research Articles

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.

Assessing the potential for successful translocation and co‐management of two endangered aquatic species

AbstractTranslocation programmes for endangered species typically focus on a single species, but in areas where little native habitat remains, it may be necessary to translocate multiple species to the same sites. Interactions between translocated species, such as predation and competition, are among the factors that need to be considered when planning multispecies translocations. Translocation sites for aquatic species are particularly scarce in southern California, where a limited number of sites exist for historically co‐occurring endangered mountain yellow‐legged frogs Rana muscosa and unarmoured three‐spine sticklebacks Gasterosteus aculeatus williamsoni. To determine how these species would interact if translocated to the same sites, we carried out experiments ex situ with R. muscosa tadpoles and a surrogate subspecies of stickleback (G. a. microcephalus). We found that (1) adult sticklebacks preyed on hatchling tadpoles but did not consume R. muscosa eggs or large tadpoles; (2) tadpoles did not consume stickleback eggs or disturb sticklebacks nests; and (3) both species' microhabitat use shifted slightly when the other was present. Our results suggest that these species can likely be co‐managed successfully, if measures are taken to curb stickleback predation on tadpoles until the R. muscosa population is well established. Using ex situ studies to evaluate species interactions prior to translocation is an approach that could prove useful in other species recovery programmes. Multispecies translocations could make better use of available resources when habitat is limited and promote ecosystem recovery by re‐establishing interactions among native species.

Mass Hierarchies and Quantum Gravity Constraints in DKMM‐refined KKLT

AbstractWe carefully revisit the mass hierarchies for the KKLT scenario with an uplift term from an anti D3‐brane in a strongly warped throat. First, we derive the bound resulting from what is usually termed “the throat fitting into the bulk” directly from the Klebanov‐Strassler geometry. Generating the small value of the superpotential W0 via the mechanism proposed by Demirtas, Kim, McAllister and Moritz (DKMM), we identify two possible DKMM‐refined KKLT scenarios for stabilizing the light axio‐dilaton modulus. The first scenario spoils the expected hierarchy between the bulk and the throat mass scales and implies that the energy scale of the uplift is larger than the species scale of the effective theory in the throat. Moreover it requires an unnaturally large tadpole that is certainly in conflict with tadpole cancellation. For the less restricted second scenario, the hierarchy can be controlled at the expense of, under the most optimistic assumptions, an only moderately large tadpole .

Anti-predator behavioral responses of Italian agile frog tadpoles (Rana latastei) exposed to microplastics

Microplastics (MPs) are nowadays abundant, persistent, and ubiquitous in the environment, representing a new threat for terrestrial, marine, and freshwater ecosystems. Although anuran populations and species are globally declining, the effect of MP exposure on this taxon has been poorly investigated. With the aim of assessing the effects of microplastic exposure on the defensive responses of Italian agile frog (Rana latastei) tadpoles, we exposed them to three different concentrations (1, 7, and 50 mg L−1) of a mixture of plastic polymers (HPDE, PVC, PS, and PES) for 2 weeks. Then, we measured the total distance covered by individual tadpoles before and after exposure to tadpole-fed dragonfly larvae (Aeshna cyanea) cues. As expected, predation risk sharply lowered the total distance travelled by tadpoles; however, MP concentration did not affect their defensive performances. We also collected data on tadpole development, activity, and mortality. In contrast with previous experiments, neither tadpole growth nor mortality varied with MP concentration. Our results indicate that the intensity of MP effects on growth and development may depend on tadpole size, with large tadpoles being less susceptible to the negative effects of MP exposure.

Predatory influence of dragonfly larvae and water scorpions on eggs and tadpoles of Indosylvirana temporalis (Anura: Ranidae)

We assessed in the laboratory the vulnerability of Bronzed frog (Indosylvirana temporalis) eggs and tadpoles to two potential sit-and-wait insect predators, larvae of a dragonfly (Pantala flavescens; Odonata: Libellulidae) and adult water scorpions (Laccotrephes sp.; Hemiptera: Nepidae). We exposed a series of different developmental stages of I. temporalis (from eggs to metamorphic climax stage) to these two predators. The results of this study showed that larvae of P. flavescens preyed on eggs and tadpoles of I. temporalis but only to stage 36. Laccotrephes sp. did not prey on eggs of I. temporalis but on tadpoles of all stages (22 to 42). This difference in predation rate was likely due to the gape size of the predators. The larvae of P. flavescens are gape-limited and cannot prey on larger tadpoles (above stage 36). Adults Laccotrephes sp. are non-gape-limited predators, using a segmented beak to pierce I. temporalis and suck the body fluids. They captured small to large tadpoles by quickly grabbing and immobilizing them using the front pair of raptorial legs. The present study shows that both predatory insects are a threat to I. temporalis at early and later stages of larval development.

The tadpole problem

We examine the mechanism of moduli stabilization by fluxes in the limit of a large number of moduli. We conjecture that one cannot stabilize all complex-structure moduli in F-theory at a generic point in moduli space (away from singularities) by fluxes that satisfy the bound imposed by the tadpole cancellation condition. More precisely, while the tadpole bound in the limit of a large number of complex-structure moduli goes like 1/4 of the number of moduli, we conjecture that the amount of charge induced by fluxes stabilizing all moduli grows faster than this, and is therefore larger than the allowed amount. Our conjecture is supported by two examples: K3 × K3 compactifications, where by using evolutionary algorithms we find that moduli stabilization needs fluxes whose induced charge is 44% of the number of moduli, and Type IIB compactifications on mathbbm{CP} 3, where the induced charge of the fluxes needed to stabilize the D7-brane moduli is also 44% of the number of these moduli. Proving our conjecture would rule out de Sitter vacua obtained via antibrane uplift in long warped throats with a hierarchically small supersymmetry breaking scale, which require a large tadpole.

Herbivory by spadefoot toad tadpoles and reduced water level affect submerged plants in temporary ponds

ABSTRACT In temporary ponds, submerged plants have adapted to recurrent periods of drought. These ponds often lack the impact of large herbivores but can harbor large numbers of herbivorous tadpoles. Tadpoles of the Iberian spadefoot toad (Pelobates cultripes) may reach large body size and consume large quantities of macrophytes during their long larval period, which is shortened with risk of pond drying. We conducted a mesocosm experiment to analyze the interplay between hydroperiod and impact of herbivorous tadpoles on the abundance and life history of 3 species of submerged plants common to temporary ponds. We observed differences in growth among plant species resulting in lags in timing of maximum cover, probably related to interspecific competitive interactions. Some plants responded to pond drying with a remarkable increase in the production of flowers. Tadpoles greatly reduced the plant cover, although their impact varied across plant species. Differential plant consumption by these large tadpoles can substantially modify the internal structure and complexity of temporary ponds, and tadpoles can also interfere with plant responses to shortened hydroperiod.

Control Issues of KKLT

AbstractWe analyze to which extent the KKLT proposal for the construction of de Sitter vacua in string theory is quantitatively controlled. Our focus is on the quality of the 10d supergravity approximation. As our main finding, we uncover and quantify an issue which one may want to call the “singular‐bulk problem”. In particular, we show that, requiring the curvature to be small in the conifold region, one is generically forced into a regime where the warp factor becomes negative in a significant part of the Calabi‐Yau orientifold. This implies true singularities, independent of the familiar, string‐theoretically controlled singularities of this type in the vicinity of O‐planes. We also discuss possible escape routes as well as other control issues, related to the need for a large tadpole and hence for a complicated topology.

Density-Dependent Fitness Attributes and Carry-Over Effects in Crawfish Frogs (Rana areolata), a Species of Conservation Concern

Fitness attributes acquired in aquatic habitats by amphibians exhibiting complex life histories have been shown to cascade through terrestrial juveniles into adulthood, a phenomenon termed carry-over effects. We explored density-dependent fitness attributes and carry-over effects in Crawfish Frogs (Rana areolata) using a set of field enclosure experiments and a series of field data. Using field enclosures, we hypothesized that 1) at high densities, intraspecific competition would produce smaller Crawfish Frog juveniles that took longer to metamorphose; 2) at high densities, interspecific competition would also produce smaller Crawfish Frog juveniles that took longer to metamorphose; and 3) vertebrate (ambystomatid salamander) predation on Crawfish Frog larvae would reduce survivorship, but by releasing competition pressure would produce relatively larger tadpoles that metamorphosed earlier. Further, we hypothesized 4) that these enclosure results would apply to field data, and that fitness attributes in newly metamorphosed Crawfish Frogs would carry over to first-time breeding adults. Our results confirmed all four hypotheses. Specifically, in Crawfish Frogs, at high densities, both intra- and interspecific competition reduced size (length and mass) at metamorphosis (hypotheses 1 and 2), and predation reduced survivorship and increased size at metamorphosis (hypothesis 3). Finally, we observed density-dependent fitness effects on newly metamorphosed Crawfish Frog juvenile size (length and mass), and carry-over effects from the larval stage on juvenile survival, adult size, and breeding adult numbers (hypothesis 4). In the absence of predators, high densities of intra- and interspecific competitors had no effect on Crawfish Frog larval survivorship. We also present suggestive evidence for compensatory effects. We discuss the potential mechanisms underlying the patterns of these interactions, as well as the role of these relationships in informing management guidelines intended to ensure the future of this species of conservation concern.

NLO corrections to h \u2192 b overline{b} decay in SMEFT

We calculate the full set of next-to-leading order (NLO) corrections to h → b overline{b} decay in the dimension-6 Standard Model Effective Field Theory (SMEFT). Our calculation forms the basis for precision studies of this decay mode in effective field theory, providing analytic and numerical results for contributions of the 45 dimension-6 operators appearing at NLO. On the technical side, we discuss several complications in NLO SMEFT computations which have not yet been addressed in the literature. These include subtleties in Higgs-Z mixing, electric charge renormalization, and especially the treatment of tadpoles in SMEFT. In particular, we highlight the role of decoupling relations in eliminating potentially large tadpole corrections to the decay rate in hybrid renormalization schemes which employ the overline{mathrm{MS}} scheme for some Standard Model parameters (such as the b-quark mass and electric charge) and the on-shell scheme for others.

Developmental effects on social preferences in frog tadpoles, Rana ornativentris

Because the costs and benefits of living in a group change according to ontogenetic stage, variation in body size is predicted to cause differences in social preferences even within individuals. Based on the fitness consequences of group living, small individuals in early developmental stages are predicted to form aggregations to reduce predation risk, whereas large individuals will avoid one another to reduce resource competition. Furthermore, when individuals recognize kin, social preferences may vary depending on the kinship relationship between them. In this study, we examined the association preference of different-sized Rana ornativentris tadpoles, that is, small individuals in early developmental stages and larger tadpoles at later developmental stages. Our binary choice experiments showed that, regardless of size, R. ornativentris tadpoles can discriminate between conspecifics based on both phenotype and relatedness. That is, association preferences were determined by the size and relatedness of the subject and the two stimulus tadpoles. Both small and large individuals spent longer with small than large tadpoles. However, there was a significant difference in preference between small and large tadpoles. When one of the two stimulus tadpoles was a large nonsibling, small tadpoles tended to associate with both small siblings and small nonsiblings. In contrast, large tadpoles showed no preference for small siblings. In the context of the benefits of grouping, phenotype matching would be effective only in small tadpoles. Conversely, under the pressure of conspecific competition, large tadpoles did not prefer to associate with similar-sized ones; this may have enabled large tadpoles to avoid competing with kin and to reduce the costs of group living.

Growth and cranial development in the Andean frogs of the genus Telmatobius (Anura: Telmatobiidae): Exploring the relation of heterochrony and skeletal diversity.

Andean frogs of the genus Telmatobius occur at high elevations, they have an aquatic mode of life and large tadpoles. There are more than 60 species that closely resemble one another and have low values of genetic divergence. However, the skeleton, particularly the cranium, is interspecifically variable with respect to the different levels of development of some elements. Heterochrony is considered to have played a prominent role in generating phenotypic variation, especially among closely related species. Herein, the developmental origins of the adult cranial configuration of two species of Telmatobius are explored. The interactions among larval and postmetamorphic growth, sexual maturation, and ossification sequence in T. oxycephalus and T. rubigo are studied. Although there are no substantial changes in the sequences of ossification of the cranium, it is likely that differential timing of larval periods is related to adult cranial characters. The prolonged larval development of T. rubigo may result in peramorphic configurations of bones that ossify during pre-metamorphosis. This long developmental time would also explain why the gonads of T. rubigo are highly differentiated by the end of metamorphosis. In this species, sexual maturation may be attained precociously in relation to metamorphosis, thereby reducing postmetamorphic developmental time of late-onset bones, which have paedomorphic configurations (e.g., vomer, neopalatine, and columella). An inverse pattern characterizes T. oxycephalus, suggesting that the duration of larval life is related to skeletal configuration in Telmatobius.

Tadpoles of the bromeliad-dwelling frog Phyllodytes luteolus are able to prey on mosquito larvae

Mosquito-borne diseases have been spreading rapidly. Although Aedes sp. are believed to prefer man-made habitats for reproduction, its larvae can also be found in bromeliads in anthropic environments. Mosquito populations can be controlled through predation, in which the relative size of predator and prey are important to understand this interaction. Tadpoles of Phyllodytes luteolus live in bromeliad axils and are potential predators of mosquito larvae. Our aim was to assess if these tadpoles are able to prey mosquito larvae, and if the predation rate differs according to the size of predator and prey. We collected P. luteolus tadpoles and Culicidae mosquito larvae from bromeliads of restinga (sandbank) areas. We measured the total length of tadpoles and mosquito larvae, and separated them into three size categories (large, medium and small). As experimental units, we used 50 mL centrifuge tubes with 35 mL of dechlorinated water, without substrate and food. We applied nine treatments composed by a combination of tadpole size categories and mosquito larvae size categories. In each unit, we added one tadpole and five mosquito larvae to evaluate the overall predation rate after 4 days. We found that P. luteolus tadpoles of any size were able to prey on mosquito larvae and verified that large tadpoles preyed a larger number of mosquito larvae than smaller size categories. Our results can contribute to evaluate the importance of tadpoles in the trophic structuring of aquatic environments, especially in phytotelmata.

Contacts with large, active individuals intensify the predation risk of small conspecifics.

Size variation within a population can influence the structure of ecosystem interactions, because ecological performance differs between individuals of different sizes. Although the impact of size variation in a predator species on the structure of interactions is well understood, our knowledge about how size variation in a prey species might modify the interactions between predators and prey is very limited. Here, by examining the interactions between predatory Hynobius retardatus salamander larvae and their prey, Rana pirica frog tadpoles, we investigated how large prey individuals affect the predation mortality of small prey conspecifics. First, in an experiment conducted in a field pond in which we manipulated the presence of salamanders and large tadpoles (i.e., large enough to protect them against salamander predation) with small tadpoles, we showed that in the presence of large tadpoles the mortality of small tadpoles from salamander predation was increased. On the basis of our observations of the activity of individuals, we hypothesized that active large tadpoles caused physical disturbances, which in turn caused the small tadpoles to move, and thus increased their encounter frequency with the predatory salamanders. To test this hypothesis, we conducted a laboratory experiment in small tanks with three players (i.e., one salamander as predator, one small tadpole as focal prey, and either a small or a large tadpole as the prospective movement inducer). In each tank, we manipulated the presence or absence of a movement inducer, and, when present, its size (large or small) and access (caged or uncaged) to the focal prey. In the presence of a large, uncaged movement inducer, the focal prey was more active and suffered from higher predation mortality compared with the other treatments, because the large movement inducer (unlike a small movement inducer) moved actively and, when uncaged, could stimulate movement of the focal prey through direct contact. The results indicated that high activity of large prey individuals and the resulting behavioral interactions with small conspecifics via direct contact indirectly increased the mortality of the small prey.

Tadpoles of three common anuran species from Thailand do not prey on mosquito larvae.

Tadpoles are often considered to be predators of mosquito larvae and are therefore beneficial for the control of certain disease vectors. Nevertheless, only a few species have actually been recorded to prey on mosquito larvae. The mosquito larvae predation rates of tadpoles of three common Thai anuran species (Bufo melanostictus, Kaloula pulchra and Hylarana raniceps) were experimentally tested. Tadpoles in varying developmental stages were used to assess a size/age effect on the predation rate. In addition, different instars of Culex quinquefasciatus were used in order to assess a prey size effect on the predation rates. All three species failed to show any evidence of mosquito larvae predation. Neither small nor large tadpoles fed on mosquito larvae. Prey size also did not affect predation. Although tadpoles do not feed on mosquito larvae, there may be other direct or indirect inter-specific interactions that adversely impact the development of larvae in shared habitats with tadpoles.

Antagonistic indirect interactions between large and small conspecific prey via a heterospecific predator

Intrapopulation size variation strongly influences ecological interactions because individuals belonging to different size groups have distinct functions. Most demonstrations of the impacts of size variation in trophic systems have focused on size variation in predator species, and the consequences of size variation in prey species are less well understood. We investigated how prey size structure shapes intra- and interspecific interactions in experiments with a gape-limited predator (larvae of the salamander Hynobius retardatus) and its heterospecific prey (frog tadpoles, Rana pirica). We found that large and small tadpole size groups each increased mortality in the other group by intensifying salamander predation; this type of indirect interactions is called apparent competition. The antagonistic impacts on the prey size groups were caused by different size-specific mechanisms. By consuming small tadpoles, the salamanders grew large enough to consume large tadpoles. The activity of large tadpoles, by increasing the activity of the small tadpoles, may increase the number of encounters with the predator and thus small tadpole mortality. These results suggest that the magnitude of a predator's ecological role, such as whether a top–down trophic cascade is initiated, depends on size variation in its heterospecific prey.

Dispatches

Dispatches

Body size and group size of Cuban tree frog (Osteopilus septentrionalis) tadpoles influence their escape behaviour

Tadpoles risk attack from both aquatic and aerial predators. We investigated how body size and group size influenced the behaviour of tadpoles before and during a predatory attack from above to test the predictions of the theoretical economic escape model. We examined escape (swimming) response of small and large Cuban tree frog (Osteopilus septentrionalis) tadpoles kept under three density treatments and predicted that increased group size, body size and depth in the water column would all reduce perceived risk and, therefore, escape responses to simulated predation. Compared with the lower density groups, tadpoles in higher density groups moved shorter distances, and many individuals did not even move away in response to being touched. Contrary to our predictions based on the economic escape model, smaller tadpoles (which should be more vulnerable to a greater suite of predators) were less reactive than larger tadpoles, and this result may reflect different costs of escape. Finally, although tadpoles might be exposed to a wider range of predator species (aerial as well as aquatic predators), we found no effect of initial depth on escape responses. In conclusion, it appears that the main benefit of increased group density in O. septentrionalis tadpoles is likely to be predator dilution, and that variation in densities of tadpoles influences the escape behaviour of individual tadpoles, regardless of tadpole size.

Two-loop electroweak threshold corrections to the bottom and top Yukawa couplings

We study the relationship between the MS¯ Yukawa coupling and the pole mass for the bottom and top quarks at the two-loop electroweak order O(α2) in the gaugeless limit of the standard model. We also consider the MS¯ to pole mass relationships at this order, which include tadpole contributions to ensure the gauge independence of the MS¯ masses. In order to suppress numerically large tadpole contributions, we propose a redefinition of the running heavy-quark mass in terms of the MS¯ Yukawa coupling. We also present Δr in the MS¯ scheme at O(α2) in the gaugeless limit. As an aside, we also list the exact two-loop expression for the mass counterterms of the bottom and top quarks.

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.