Tadpole Growth Research Articles

Increased Temperature and Exposure to Ammonium Alter the Life Cycle of an Anuran Species.

Amphibian populations are undergoing a major recession worldwide, likely triggered by global change components such as the global warming and pollutants, among which agrochemicals, in general, and fertilizers, in particular, play a central role given their relevance in agriculture. Potential synergies among these stressors could maximize their individual effects. In this work, we investigated the consequences of a controlled chronic exposure to increased temperature and a sublethal dose of ammonium during the larval stage of Pelophylax perezi frogs on the growth, development, and locomotor performance of tadpoles and the metamorphs they gave rise to. To that end, tadpoles were reared either in heated or nonheated tanks, with or without ammonium added. The parents of these tadpoles came from either a pine grove or an agrosystem. Survival was reduced in agrosystem tadpoles reared with ammonium. Increased temperature potentiated tadpole growth while giving way to smaller metamorphs. Faster growth could be a consequence of increased metabolism, whereas the smaller size could follow an accelerated development and metamorphosis, which reduced the growth period. Also, swimming speed was greater in tadpoles reared in heated tanks, while jumping distance was greater in metamorphs reared in nonheated tanks. The effects of temperature were more marked in agrosystem than in pine grove individuals, which could mirror reduced adaptability. Thus, the ability to withstand the effects of these stressors was lower in agrosystem tadpoles.

Effects of food level and fecal material on the plasticity of metamorphic traits in Asiatic toad, Bufo gargarizans, in Central China

Abstract According to Richards’ hypothesis, the presence of a nonpigmented unicellular alga in the intestinal tract of tadpoles is believed to be the inhibitory factor that affects their growth. It is proposed that thecanimals eat their fecal material containing these algal cells, which are then reintroduced into their systems when the alga is shed with the feces and dropped to the bottom. In this study, we aimed to investigate the plasticity of metamorphic traits in the Asiatic toad (Bufo gargarizans) under different combinations of fecal material and food levels. Our findings revealed that B. gargarizans tadpoles reared at high food levels exhibited accelerated larval periods but had smaller metamorphic sizes compared to those reared at low food levels. This suggests that the tadpoles prioritize rapid development at the expense of body mass during metamorphosis. Furthermore, our study discovered evidence supporting the positive effect of fecal material on tadpole growth, as indicated by the investigation of growth rate. Importantly, the presence of feces did not result in smaller body mass on average for Asiatic toad tadpoles compared to those raised in the absence of fecal material. The difference in body mass between fecal material treatments tended to be smaller at low food levels, implying that feces does not inhibit growth in B. gargarizans tadpoles. Therefore, our results contradict Richards’ hypothesis and provide support for a novel mechanism that is selected for in areas where coprophagy is likely to be advantageous, particularly in times of food scarcity.

Effects of perfluoroalkyl sulfonic acids on developmental, physiological, and immunological measures in northern leopard frog tadpoles

The chronic toxicity of short chain perfluoroalkyl sulfonic acids (PFSAs), such as perfluorobutanesulfonic acid (PFBS) and perfluorohexanesulfonic acid (PFHxS), are relatively understudied despite the increasing detection of these compounds in the environment. We investigated the chronic toxicity and bioconcentration of PFBS and PFHxS using northern leopard frog (Rana [Lithobates] pipiens) tadpoles. We exposed Gosner stage (GS) 25 tadpoles to either PFBS or PFHxS at nominal concentrations of 0.1, 1, 10, 100, and 1000 μg/L until metamorphosis (GS42). We then assessed tadpole growth, development, stress, and immune metrics, and measured fatty acid (FA) composition and PFSA concentrations in liver and whole-body tissues. Tadpole growth and development measures were relatively unaffected by PFSA exposure. However, tadpoles exposed to 1000 μg/L PFBS or PFHxS had significantly increased hepatosomatic indexes (HSI) relative to controls. Further, tadpoles from the 1000 μg/L PFHxS treatment had altered FA profiles relative to controls, with increased total FAs, saturated FAs, monounsaturated FAs, and omega-6 polyunsaturated FAs. In addition, tadpoles from the 1000 μg/L PFHxS treatment had a higher probability of waterborne corticosterone detection. These results suggest that PFBS and PFHxS influence the hepatic health of tadpoles, and that PFHxS may alter lipid metabolism in tadpoles. We also observed a higher probability of tadpoles being phenotypically female after exposure to an environmentally relevant concentration (0.1 μg/L) of PFHxS, suggesting that PFHxS may exert endocrine disrupting effects on tadpoles during early development. The measured bioconcentration factors (BCFs) for both compounds were ≤10 L kg−1 wet weight, suggesting low bioconcentration potential for PFBS and PFHxS in tadpoles. Many of the significant effects observed in this study occurred at concentrations several orders of magnitude above those measured in the environment; however, our work shows effects of PFSAs exposure on amphibians and provides essential information for ecological risk assessments of these compounds.

Epidermal cell proliferation and differentiation in the beak of tadpoles of Rana dalmatina

AbstractEpidermal cell proliferation and differentiation during formation of the beak in tadpoles of Rana dalmatina. Acta Zoologica (Stockolm). The beak utilized in tadpoles of R. dalmatina for crushing vegetables is formed of cornified cell layers. A row of large wedge‐like cells forms a central pile that produces the sharp corneous lamina of the beak. The labial and oral surfaces of the beaks also accumulate corneous material during proliferation and differentiation of keratinocytes from the epidermis to form a sheath around the central corneous cells. Corneocytes are shed during the growth of tadpoles. Electron microscopy reveals that keratin and mucus granules are main components of these keratinocytes. Electron‐dense organelles of unknown composition and with inside lamellae are also present. Using immunohistochemistry after post‐injection of 5BrdU, a marker of cell proliferation, the main timing of formation of the beak has been determined. After 2–5 h from injection, labelled nuclei of keratinocytes are seen in the basal layer, and sparse suprabasal labelled nuclei are detected after 5 h. Labelled keratinocytes are seen in suprabasal layers at 2 days post‐injection. At 5 and 6 days labelled keratinocytes are present in central corneous cells and in the lateral shell of corneocytes forming the labial and oral beak sides. Shedding a complete stratum corneum likely takes more days, but this depends on feeding usage.

Developmental plasticity to desiccation risk in tadpoles of a tropical inselberg specialist

Developmental plasticity evolves in heterogeneous environmental conditions as long as individuals can accurately perceive them. A paradigmatic example of developmental plasticity is the ability of amphibian larvae to alter growth and development in response to the risk of pond drying. Such responses are often found in amphibian species breeding in highly dynamic water bodies with high desiccation risk. The inselbergs of the Guianan Shield are rocky outcrops with extremely high and fluctuating temperatures and a marked seasonality in precipitation. During the rainy season, eroded depressions form precipitation-dependent pools with a high and variable risk of desiccation within the timeframe of a few days. The frog Leptodactylus lithonaetes specializes in breeding in this extreme environment, and its tadpoles are thus forced to cope with desiccation risk by adjusting their developmental trajectories and physiological performance. We experimentally assessed the effect of different levels of desiccation risk, under controlled temperature conditions, on developmental rate, growth, and temperature-dependent locomotor performance in tadpoles of Leptodactylus lithonaetes. We did not find an effect of desiccation risk on developmental rate, but under simulated drying conditions, tadpoles showed larger body size, greater body mass, and enhanced locomotor performance compared to constant (high or low) water levels. These results suggest that drying pools offer cues that trigger developmental and behavioral changes in these tadpoles, enabling them to enhance growth over a short time span without accelerating development. We discuss the potential compensatory mechanisms behind these responses and highlight the need for further investigations in species with semiterrestrial life histories in extreme environments.

Effects of dietary lipid and protein levels on metamorphosis, growth, metabolism and gut microbiota of tadpole (Lithobates catesbeianus)

Tadpole cultivation is a crucial step in the artificial production of bullfrogs (Lithobates catesbeiana), but its feed nutrition is poorly understood. This study examined how dietary lipid and protein levels affect metamorphosis, growth and intestinal health of tadpole. Six groups of tadpoles were fed six diets with two lipid levels (7% and 10%) and three protein levels (36%, 40% and 44%) for 70 days. The results showed that at 7% lipid level, increasing protein enhanced metamorphosis rate and mean weight of tadpoles, reaching the optimal value at 40% protein (P < 0.05). At 10% lipid level, increasing protein also improved mean weight, peaking at 40% protein. Dietary nutrition also influenced liver amino acid and lipid metabolism directly. At 7% lipid level, increasing protein significantly increased the activities of hepatic enzymes GLS, PDH, ALT, AST, etc. (P < 0.05), and up-regulated the expression of hepatic genes fas, accb, fadd6 and cpt1a involved in lipid metabolism (P < 0.05). At 10% lipid level, increasing protein also up-regulated fadd6 and cpt1a genes (P < 0.05), but down-regulated acadl gene. Meanwhile, increasing dietary lipid level elevated TG and T-CHO levels in liver. Increasing dietary protein enhanced gut microbiota richness, while increasing lipid reduced it. Moreover, different gut microbiota groups had distinct biomarkers, such as Rikenellaceae, Desulfovibrionaceae, Burkholderiales and Bacteroidales, which were related to amino acid or lipid metabolism. In summary, under the test conditions, 7% lipid and 40% protein in diet are suitable levels, which can promote metamorphosis, growth and metabolism of tadpoles, and are more economical than high-lipid and high-protein diets.

Yosemite toad (Anaxyrus canorus) transcriptome reveals interplay between speciation genes and adaptive introgression.

Genomes are heterogeneous during the early stages of speciation, with small 'islands' of DNA appearing to reflect strong adaptive differences, surrounded by vast seas of relative homogeneity. As species diverge, secondary contact zones between them can act as an interface and selectively filter through advantageous alleles of hybrid origin. Such introgression is another important adaptive process, one that allows beneficial mosaics of recombinant DNA ('rivers') to flow from one species into another. Although genomic islands of divergence appear to be associated with reproductive isolation, and genomic rivers form by adaptive introgression, it is unknown whether islands and rivers tend to be the same or different loci. We examined three replicate secondary contact zones for the Yosemite toad (Anaxyrus canorus) using two genomic data sets and a morphometric data set to answer the questions: (1) How predictably different are islands and rivers, both in terms of genomic location and gene function? (2) Are the adaptive genetic trait loci underlying tadpole growth and development reliably islands, rivers or neither? We found that island and river loci have significant overlap within a contact zone, suggesting that some loci are first islands, and later are predictably converted into rivers. However, gene ontology enrichment analysis showed strong overlap in gene function unique to all island loci, suggesting predictability in overall gene pathways for islands. Genome-wide association study outliers for tadpole development included LPIN3, a lipid metabolism gene potentially involved in climate change adaptation, that is island-like for all three contact zones, but also appears to be introgressing (as a river) across one zone. Taken together, our results suggest that adaptive divergence and introgression may be more complementary forces than currently appreciated.

Effects of Salinity on the Egg Fertilization, Hatching, and Tadpole Growth and Survival Rates of the Thailand Frog (Rana tigerina Dubois, 1981)

We studied the effects of salinity on the egg fertilization, hatching, and tadpole growth and survival rates of the Thailand frog (Rana tigerina Dubois, 1981), an introduced species that is commonly cultured in the Mekong Delta, Vietnam. Salinity levels of 2, 6, and 4% significantly affected the fertilization and hatching rates of the eggs, as well as the tadpole survival rates from the newly hatched to yolk sac exhaustion stages, respectively p&lt;0.05. Notably, during the stage from yolk sac exhaustion to juvenile tadpole, a salinity of 3% resulted in an increase in the final weight of the tadpoles throughout the stage and a significant increase in Phase 1 (the tadpole stage from yolk sac exhaustion to the onset of foreleg emergence) and Phase 2 (the tadpole stage from the onset of foreleg emergence to the onset of hind leg emergence); however, it did not show a significant effect on tadpole survival rates in Phases 1 and 2 of this stage p&gt;0.05. A salinity level of up to 5% showed no significant effect on the growth performance but caused a significant reduction in the survival rates of the tadpoles during this stage. We recommend that the artificial reproduction process of Thai frogs should be performed using salinities of &lt;2%, with salinities of ≤2 and 3% being suitable for rearing tadpoles from the newly hatched to yolk sac exhaustion stage and from the yolk sac exhaustion to juvenile stage, respectively.

The effects of two short-chain perfluoroalkyl carboxylic acids (PFCAs) on northern leopard frog (Rana pipiens) tadpole development

Short-chain perfluoroalkyl carboxylic acids (PFCAs) have been detected in the environment globally. The presence and persistence of these compounds in the environment may lead to chronic wildlife exposure. We used northern leopard frog (Rana pipiens) tadpoles to investigate the chronic toxicity and the bioconcentration of two short-chain PFCAs, perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA). We exposed Gosner stage 25 tadpoles to PFBA and PFHxA (as individual chemicals) at nominal concentrations of 0.1, 1, 10, 100, and 1000 µg/L for 43–46 days. Tadpoles exposed to 0.1 to 100 µg/L of PFBA and PFHxA had significantly higher mean snout-to-vent lengths, mean masses, and scaled mass indexes than control tadpoles. These results indicate that exposure to short-chain PFCAs influences tadpole growth. Further investigation into the mechanism(s) causing the observed changes in tadpole growth is warranted. We observed a significantly higher proportion of males in the PFBA 1 µg/L treatment group, however further histological analyses are required to confirm visual sex identification before making concrete conclusions on the effects of PFCAs on amphibian sex ratios. PFBA concentrations in tissues were higher than PFHxA concentrations; a pattern that contrasts with previously published studies using fish, suggesting potential differences between taxa in PFBA and PFHxA bioconcentration. Bioconcentration factors were <10 L/kg wet weight, indicating low bioconcentration potential in tadpoles. Our results suggest that PFBA and PFHxA may have effects at environmentally-relevant concentrations (0.1–10 µg/L) and further investigation is required before these compounds can be deemed a “safe” alternative to their long-chain counterparts.

Mechanisms, costs, and carry-over effects of cannibal-induced developmental plasticity in invasive cane toads.

Inducible defences can improve survival in variable environments by allowing individuals to produce defences if they detect predators. These defences are often expressed as inter-related developmental, morphological, and behavioural changes. However, producing defences can incur costs, which may be expressed immediately and/or during subsequent life stages. In Australia, waterborne cues of potentially cannibalistic conspecific tadpoles induce hatchlings of invasive cane toads to accelerate their developmental rate, thereby reducing their window of vulnerability. However, the mechanisms and costs of such accelerated development are poorly understood, and whether cane toad embryos show cannibal-induced plasticity in other traits is unknown. Here, we found no evidence of altered time of hatching for embryos exposed to non-feeding conspecific cannibal tadpole cues. Additionally, hatchling dispersal behaviours were not affected by exposure to these cues. However, developmental acceleration of hatchlings induced by exposure to tadpole cues was accompanied by reduced hatchling growth, indicating a trade-off between these processes. At the conclusion of the hatchling stage, cannibal-exposed individuals were smaller and morphologically distinct from control siblings. This size reduction affected performance during the subsequent tadpole stage: smaller cannibal-exposed individuals were more likely to die, and initial size tended to be positively associated with subsequent tadpole growth and development across treatments (respectively, p = .07 and p = .06). However, even accounting for variation in initial size, there was an additional negative effect of cannibal exposure on tadpole growth and development, demonstrating that the fitness costs associated with developmental acceleration are not entirely attributable to size reductions.

The effects of preformed vitamin A and provitamin A carotenoid supplementation on tadpoles of the poison frog Phyllobates vittatus.

Understanding the nutritional requirements of captive animals is necessary for proper animal husbandry, however, the specific dietary requirements for many amphibian species commonly kept in captivity are unknown. Like most vertebrates, frogs cannot synthesize carotenoids and must therefore obtain these essential nutrients through diet. It is unclear if amphibians can cleave provitamin A carotenoids to form vitamin A metabolically within the body, so common practice is to supplement their captive diets with both preformed vitamin A and provitamin A carotenoids. We carried out a feeding experiment in tadpoles of Phyllobates vittatus, a commonly kept poison frog species, to test the effects of supplementing a fish flake diet with a provitamin A carotenoid (2.5 mg/g β-carotene) and vitamin A (0.033-0.066 µg/mL retinyl acetate), both individually and in combination. Contrary to our expectations, supplementation had either no effect or adverse effects on tadpole growth and survivorship. Tadpoles reared under supplemented diets with vitamin A showed higher mortality rates, coupled with symptoms of hypervitaminosis A. Survivors had a smaller body size and mass at metamorphosis. β-carotene supplementation alone had no detectable effect. The vitamin A and β-carotene levels in our supplemented diet have been shown to be harmless or benefit tadpoles of other species, yet our results indicate that adding these amounts to what is found in a generalist fish flake mix can have detrimental effects on P. vittatus tadpoles. More broadly, this study highlights the importance of creating husbandry guidelines based on the specific physiological needs of the species (or species groups) being kept in captivity, rather than general ones for all amphibians, as is often done.

Kinship influences the metamorphic traits of Asiatic toad (Bufo gargarizans) larvae, in Central China

Kin recognition has been selected by natural selection because it can enhance the chances of cooperation among close relatives, but it could also be an accidental consequence of other life-history processes. In this study, we carried out experiments by using Asiatic toad tadpoles (Bufo gargarizans) to evaluate the hypothesis that: (1) individuals can use waterborne chemical cues or combine other possible cues to communicate kinship identity when exposed to kin during early ontogeny; (2) unfamiliar siblings (or familiar non-siblings) should have similar growth with unfamiliar non-siblings because the former is not able to identify their relatives (or may not consider familiar non-siblings as kin); (3) the familiar siblings may obtain a more equal resource share in populations of siblings, thus size variation is weak. The first and second predictions were partially better supported: kinship had a positive effect on tadpole growth, obtained larger mass at metamorphosis, and increased survival, but development time was longer than that of unfamiliar non-siblings. Further, the growth of unfamiliar siblings and familiar non-siblings was different from that of familiar siblings, suggesting that Asiatic toad tadpoles lose kin-recognition ability when isolated across the embryonic stage or may not be considered as siblings when exposed to water from non-sibling groups during early embryonic development. Thus, besides chemical cues, Asiatic toad tadpoles need to combine other possible modalities to communicate kinship identity. The third prediction was supported weakly. Therefore, our results suggest that exposure to kin during early embryonic development is essential for altering kin-recognition ability. More importantly, familiar sibling groups can be expected to develop slower and spend more time in the water, allowing more time for feeding and growth, which is consistent with kin selection theory, suggesting that natural selection should drive the evolution of mechanisms that minimize the competitive intensity between sibling groups.

Carbon nitride dots do not impair the growth, development, and telomere length of tadpoles

Carbon nanoparticles, or carbon dots, can have many beneficial uses. However, we must consider whether they may have any potential negative side effects on wildlife or the ecosystem when these particles end up in wastewater. Early development stages of amphibians are particularly sensitive to contaminants, and exposure to carbon dots could disrupt their development and cause morbidity or death. Past studies have investigated short-term exposure to certain types of nanoparticles, but if these particles get into wastewater exposure may not be short term. Therefore, we tested whether chronic exposure to different concentrations of carbon dots affects the growth, metamorphosis, and telomere length of Cuban tree frog (Osteopilus septentrionalis) tadpoles. We exposed 12 groups of five tadpoles each to different concentrations of carbon dots and a control for three months and tracked survival, growth and metamorphosis. We used carbon nitride dots approximately 2 nm in size at concentrations of 0.01 mg/ml and 0.02 mg/ml, known to interrupt development in zebrafish embryos. After three months, we measured telomere length from tissue samples. We found no difference in tadpole survivorship, growth, development rate, or telomere length among any of the groups, suggesting that carbon dots at these concentrations do not disrupt tadpole development.

Effects of Thyroid Powder on Tadpole (Lithobates catesbeiana) Metamorphosis and Growth: The Role of Lipid Metabolism and Gut Microbiota.

A low metamorphosis rate of amphibian larvae, commonly known as tadpoles, limits the farming production of bullfrogs (Lithobates catesbeiana). This study aimed to examine the effects of processed thyroid powder as a feed additive on tadpole metamorphosis, lipid metabolism, and gut microbiota. Five groups of tadpoles were fed with diets containing 0 g/kg (TH0), 1.5 g/kg (TH1.5), 3 g/kg (TH3), 4.5 g/kg (TH4.5), and 6 g/kg (TH6) thyroid powder for 70 days. The results showed that TH increased the average weight of tadpoles during metamorphosis, with the TH6 group having the highest values. The TH4.5 group had the highest metamorphosis rate (p < 0.05). Biochemical tests and Oil Red O staining showed that the lipid (triglyceride) content in the liver decreased after TH supplementation, especially at doses higher than 1.5 g/kg. RT-qPCR revealed that TH at doses higher than 4.5 g/kg significantly up-regulated the transcriptional expression of the pparα, accb, fas, fadd6, acadl, and lcat genes, which are related to lipid metabolism (p < 0.05). These results showed that TH seems to simultaneously promote the synthesis and decomposition of lipid and fatty acids, but ultimately show a decrease in lipids. As for the gut microbiota, it is noteworthy that Verrucomicrobia increased significantly in the TH4.5 and TH6 groups, and the Akkermansia (classified as Verrucomicrobia) was the corresponding genus, which is related to lipid metabolism. Specifically, the metabolic pathways of the gut microbiota were mainly enriched in metabolic-related functions (such as lipid metabolism), and there were significant differences in metabolic and immune pathways between the TH4.5 and TH0 groups (p < 0.05). In summary, TH may enhance lipid metabolism by modulating the gut microbiota (especially Akkermansia), thereby promoting the growth of tadpoles. Consequently, a supplementation of 4.5 g/kg or 6 g/kg of TH is recommended for promoting the metamorphosis and growth of tadpoles.

Pollen as food: effects of consumption on tadpole growth, development, and mobility

The structure of many aquatic food webs is influenced by tadpole survivorship and duration of seasonal occupancy, which depend on tadpole diet. Pollen has been occasionally reported to occur in tadpole diets, and the available studies show that tadpoles have a strong preference for this supposedly nutritive resource. Thus, we aimed to test whether a diet composed of pollen from varied plant species would boost tadpole growth, development, and agility/mobility, compared to a regular artificial balanced and nutritive diet. Tadpoles in initial developmental stages 25 and 30 grew more when fed with pollen, compared to artificial food and a mixture of both diets. Those initially in stage 30 advanced more developmental stages during one month when fed exclusively with pollen. Tadpoles fed with pollen moved longer distances in response to an aversive stimulus simulating a predatory attack than tadpoles fed with artificial food or a mixed diet. Our results corroborate the hypotheses of pollen being a very important food source to aquatic consumers such as tadpoles, being likely to influence the structure of aquatic food webs through tadpole nutrition and modulation of growth/development speed, as well as tadpole ability to escape predators.

Study on Detoxification of Biochemical Fulvic Acid on Quasipaa boulengeri Tadpoles under Copper Stress

To understand the detoxification effect of biochemical fulvic acid (BFA) on Quasipaa boulengeri (Q.boulengeri ) tadpoles under copper stress, effects of different concentrations of BFA on growth and physiological indexes of tadpoles. The results showed that the survival rate of tadpoles increased with the increase of BFA concentration. With the increase of BFA concentration, the growth rate of body weight and body length reached the peak at 45 mg/L; The superoxide dismutase(SOD) showed a downward trend in the control group (CK) and an upward trend in each treatment group, with significant difference between the treatment groups (P &lt; 0.05); The content of the malondialdehyde(MDA) and the treatment time and concentration of BFA showed an upward trend in CK group. With the increase of BFA concentration and the content of the MDA decreased, there was significant difference between the treatment groups (P &lt; 0.05). In conclusion, BFA can be used as a detoxification agent under copper stress, and the suitable concentration of BFA is 45 mg/L. This study provides a theoretical basis for the artificial breeding and scientific protection of Q.boulengeri tadpoles.

Географическая изменчивость длительности личиночного развития и размеров метаморфов травяных лягушек (Ranidae, Anura)

With the help of artificial inter-population crosses of adult Rana temporaria from four spatially remote populations of the European part of the species' range, the magnitude and direction of changes in metamorphic traits were estimated. The maximum values of the size of metamorphs at the end of metamorphosis and the rate of larval growth were found in the descendants of the parents of Belarusian populations (Turov and Minsk) and, as a rule, in hybrid offspring with the participation of the parents of these populations, when crossing with individuals from the population of the Moscow region (ZBS). Outbreeding depression of the time of larval development before the end of metamorphosis and growth rate was revealed when crossing ZBS females with Turov males. In a population from a region with a relatively low climatic temperature (Kirov), the minimum size of metamorphs was revealed, but not the time of larval development. In most crosses, a relatively greater contribution of non-additive genetic variability, as well as the maternal effect associated with the difference in egg sizes, to the formation of inter-population differences was revealed. The inter-population variability of studied traits related to fitness is often directed along the gradient of environmental conditions, and not counter-gradient (as should be expected based on the conception of counter-gradient selection), which is explained by the choice of different growth and development strategies in tadpoles formed in southern and northern populations.

Don't take my trees: Re‐evaluating the importance of trees when it comes to managing green and golden bell frog, Litoria aurea, habitat

AbstractIt is vital to identify habitats used by each life stage of a species to formulate effective conservation management and restoration guidelines. For the threatened green and golden bell frog, Litoria aurea, it is currently recommended that, to prevent waterbody shading, managed or constructed habitat for the species should not include trees. Shading has been reported to prevent adults from sun basking, reduce breeding activity, and lower water temperatures, which may impede tadpole growth and development and provide optimum conditions for the amphibian chytrid pathogen, Batrachochytrium dendrobatidis. However, the complete exclusion of trees, which are naturally present in L. aurea habitat, warrants evidence that supports this recommendation. In the present study, we used a multi‐year dataset on an L. aurea population on Kooragang Island, NSW, Australia to determine the occurrence of tree use by post‐metamorphic individuals. These data included information on nearly 12 500 individuals captured from 86 waterbodies across 8 consecutive breeding seasons. We found that tree use by juveniles, adult males, and adult females was widespread and common, occurring both during the day and night, with more than one out of every 20 individuals captured in trees. Our findings suggest that trees are a potentially important attribute of the terrestrial component of wetland habitats occupied by L. aurea. We hypothesize that trees may (i) create microhabitat for foraging and/or increased diversity of prey species, (ii) provide refuge from predators, and (iii) allow sun basking off the ground, thereby offering protection against the chytrid fungus while removing them from chytrid‐prevalent environments such as water and moist soils. We call for the careful reconsideration of tree exclusion within L. aurea habitat and further research into the benefits of allowing trees to grow near waterbodies to accommodate the ecological needs of this threatened species.

Benefits and costs of female and male care in amphibians: a meta-analytical approach.

The origin of parental care is a central question in evolutionary biology, and understating the evolution of this behaviour requires quantifying benefits and costs. To address this subject, we conducted a meta-analysis on amphibians, a group in which parental care has evolved multiple times. We found that both male and female parents increase egg survival, regardless of whether the breeding site is concealed or exposed. Parental care also increases survival and growth of tadpoles and juveniles, independent of the caring sex. However, parental care reduces parental body condition, particularly when parents remain stationary near the offspring. Females tend to experience higher reproductive costs, but sample size is restricted to few species. In some frog species, paternal care increases male reproductive success because females prefer caring males. The benefits of parental care in amphibians resembles those reported for arthropods but differ from fish, in which parental care does not improve offspring survival. Moreover, the decrease in body condition, which is not found in fish, is influenced by the form of parental care, suggesting a trade-off between caring and foraging, as already reported for certain arthropods. Finally, the reproductive costs of parental care for both sexes remain unexplored and deserve further research.

Intraspecific interference retards growth and development of cane toad tadpoles, but those effects disappear by the time of metamorphosis.

Competition among larval anurans can occur via interference as well as via a reduction in per-capita food supply. Previous research on intraspecific interference competition in cane toad (Rhinella marina) tadpoles found conflicting results, with one study detecting strong effects on tadpoles and another detecting no effects on metamorphs. A capacity to recover from competitive suppression by the time of metamorphosis might explain those contrasting impacts. In a laboratory experiment, we found that nine days of exposure to intraspecific interference competition strongly reduced tadpole growth and development, especially when the competing tadpoles were young (early-stage) individuals. Those competitive effects disappeared by the time of metamorphosis, with no significant effect of competition on metamorph body condition, size, larval period or survival. Temporal changes in the impact of competition were not related to tadpole density or to variation in water quality. The ability of larval cane toads to recover from intraspecific interference competition may enhance the invasive success of this species, because size at metamorphosis is a significant predictor of future fitness. Our study also demonstrates a cautionary tale: conclusions about the existence and strength of competitive interactions among anuran larvae may depend on which developmental stages are measured.