Frog Body Size Research Articles

Deeper or Shallower? Interactions and Temporal Variability in Choosing Burrowing Depth between Species of Economic Burrowing Frogs of Forest Area from Northeastern Thailand

Burrowing is one of the important seasonal behaviors in amphibians that could be related to physiological ecology and environmental factors. Burrowing characteristics and temporal variability in burrowing behaviors were explored and examined from three sampling surveys in northeastern Thailand in 2017–2018. Four species of burrowing frogs were identified with overwhelmingly abundant specimens in two species, Glyphoglossus molossus and Kaloula mediolineata. In general, K. mediolineata burrowed deeper than G. molossus although their body size were not different. There were no clear relationships between burrowing depth and frog body size in each species, although G. molossus showed larger SVL in dry seasons than that in rainy seasons. In contrast to K. mediolineata which preferred to burrow deeper in dry seasons, burrowing depth of G. molossus was almost stable among seasons. The results of this study highlighted an interaction between season and species in the burrowing depth of these two frog species in northeastern Thailand.

Frog body size responses to precipitation shift from resource-driven to desiccation-resistant as temperatures warm.

Climate change threatens biodiversity in a range of ways, including changing animal body sizes. Despite numerous examples of size declines related to increasing temperatures, patterns of size change are not universal, suggesting that one or more primary mechanisms impacting size change are unknown. Precipitation is likely to influence the size different from and in conjunction with changes in temperature, yet tests of the interaction between these variables are rare. In this study, we show that a crossover interaction between temperature and precipitation impacts the body size of frogs as the climate warms. Using more than 3000 museum frog specimens from Borneo and climate records spanning more than 100 years, we found that frogs are larger in wet conditions than in dry conditions at cool temperatures, suggesting that resource availability determines body size at colder temperature. Conversely, frogs are larger in dry conditions than in wet conditions at warm temperatures, resulting in a crossover to desiccation resistance as the main determinant of body size as climates warm. Our results demonstrate that global warming can alter the impact of precipitation on life-history traits. We suggest that increased attention be paid to such interactive effects of climate variables, to identify complex mechanisms driving climate-induced size changes.

Amphibian body size and species richness as a proxy for primary productivity and climate: The Orce wetlands (Early Pleistocene, Guadix-Baza Basin, SE Spain)

Amphibians are considered excellent indicators of ecological and climatic changes with a remarkable phenotypic plasticity. The study of such adaptative capacities is central to understanding the climate and environmental changes that occurred during the Early-Middle Pleistocene Transition, at around 1.2 Ma, when the persistence of subtropical ecosystems in Europe came to an end, and several reptile and tree taxa were extirpated. The SE Spain sites in the Guadix-Baza Basin offer an exceptional opportunity for studying this change, in addition to the significant findings made in this area in the field of human evolution. We have analysed the body size of the most well-represented amphibian species in the sites, the Iberian waterfrog, Pelophylax perezi . In order to reconstruct past body sizes from fossil samples, a regression model from current osteological collections has been generated. Also, diversity of the herpetofauna community was studied at different levels as richness or species number. Finally, to study the relationships between body size, richness, climate and productivity, OLS regression models and Pearson correlations were applied. Also for this purpose, a productivity indicator was designed based on the addition of the two most productive ecosystems from previous habitat reconstruction. Amphibian body size appears to be negatively associated with primary productivity, reaching minimum values during the interglacial stages, when species richness increased. In contrast, during glacial periods characterised by greater aridity and fewer resources, amphibian body size increased while species richness decreased. Main explanations proposed to justify this pattern are the “water-availability hypothesis” and a trade-off between somatic growth and reproductive opportunities for females. The study of herpetofaunal diversity shows a clear correlation to regional plant diversity and primary productivity. The results of this work indicate that species richness and amphibian body size are valuable proxies that can complement current environmental and climate reconstruction methods. • Somatic growth and reproduction: the trade-off which determines amphibian body size. • Amphibian body size decreases towards more productive ecosystems. • Primary productivity determines species richness. • Frog body size is defined as a new indicator of Pleistocene ecosystem conditions.

Correlated and decoupled evolution of adult and larval body size in frogs: Larval and adult size evolution

Correlated and decoupled evolution of adult and larval body size in frogs: Larval and adult size evolution

Correlated and decoupled evolution of adult and larval body size in frogs

The majority of animal species have complex life cycles, in which larval stages may have very different morphologies and ecologies relative to adults. Anurans (frogs) provide a particularly striking example. However, the extent to which larval and adult morphologies (e.g. body size) are correlated among species has not been broadly tested in any major group. Recent studies have suggested that larval and adult morphology are evolutionarily decoupled in frogs, but focused within families and did not compare the evolution of body sizes. Here, we test for correlated evolution of adult and larval body size across 542 species from 42 families, including most families with a tadpole stage. We find strong phylogenetic signal in larval and adult body sizes, and find that both traits are significantly and positively related across frogs. However, this relationship varies dramatically among clades, from strongly positive to weakly negative. Furthermore, rates of evolution for both variables are largely decoupled among clades. Thus, some clades have high rates of adult body-size evolution but low rates in tadpole body size (and vice versa). Overall, we show for the first time that body sizes are generally related between adult and larval stages across a major group, even as evolutionary rates of larval and adult size are largely decoupled among species and clades.

Zooplankton associated with phytotelms and treefrogs in a neotropical forest

ABSTRACT Assumptions about the distribution of zooplankton communities in various ecosystems are often limited by lack of data on dispersal mechanisms. Many studies on frog-mediated passive dispersal have been developed in bromeliads, but they usually focus on ostracods and annelids. We investigated the potential for external phoresy of zooplankton (rotifers, cladocerans, copepods) by treefrogs in bromeliad phytotelms. Our hypotheses are that (1) zooplankton composition on frogs’ skin and in phytotelm tanks is similar, and (2) frogs with larger body size carry more propagules of these invertebrates. We filtered phytotelm water (10 to 150 mL) using plankton net (45 µm), and fixed invertebrates with 4% formalin. Frogs were actively collected in and around bromeliads (up to ~1.5 m radius) and then washed with distilled water. Fourteen species of rotifers and three of crustaceans were registered in phytotelm water and frog bodies. We captured 17 frogs with a snout-vent length (SVL) ranging from 2 to 5 cm and belonging to five species: Pristimantis ramagii (Boulenger, 1888), Dendropsophus decipiens (A. Lutz, 1925), Scinax auratus (Wied-Neuwied,1821), S. pachycrus (Miranda-Ribeiro, 1937) and S. x-signatus (Spix, 1824). Among them, 12 (70.59%) had propagules adhered to their bodies, of which the majority (ten individuals) had active zooplankton forms, while only two had dormant eggs. Ten rotifer and two microcrustacean species were recorded adhered to frogs. The zooplankton composition differed between phytotelms and anuran skin, and frog body size does not explain the number of propagules carried, refuting both hypotheses. However, evidence of dispersal was found due to the high number of propagules adhered to anurans. Our study provides evidence that frogs may be potential dispersers of dormant and active forms of zooplankton in bromeliads, through external phoresy.

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

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

Night and day: comparing flight initiation dynamics in two closely related species of true frogs

The decision of when to flee a predator depends on the costs and benefits of flight. Here, we used two species of closely related frogs, Lithobates catesbeianus and L. clamitans, to test the effects of several factors on flight initiation distance (FID), the distance between an approaching predator and its prey when the latter flees. We altered costs of flight by approaching frogs from within versus outside ponds, and we tested the influence of broad-scale visibility by approaching frogs during the day and at night. To assess small-scale visibility, we measured percentage of vegetative cover at the point from which a frog fled. To test effects of distance to refuge and body size on FID, we measured distance between each frog and the pond margin when the frog fled, and we estimated frog size. We predicted that FID would be greatest during the day and when frogs were approached from outside the pond. We also predicted that FID would increase with less vegetative cover, increasing distance between frogs and the pond, and increased frog body size. We used an information theoretic approach to contrast alternative models. For L. catesbeianus, the best-fit model included four highly weighted parameters: approach location, day/night, body size and distance to refuge. For L. clamitans, the best-fit model included only two parameters with high weights, day/night and body size. Lithobates catesbeianus and L. clamitans appear to differ in their sensitivity to predators, with L. catesbeianus having longer FIDs than L. clamitans and being strongly affected by more parameters. The differences we observed in FID between the two species may be best explained by differences in body size.

Whether the Weather Drives Patterns of Endemic Amphibian Chytridiomycosis: A Pathogen Proliferation Approach

The pandemic amphibian disease chytridiomycosis often exhibits strong seasonality in both prevalence and disease-associated mortality once it becomes endemic. One hypothesis that could explain this temporal pattern is that simple weather-driven pathogen proliferation (population growth) is a major driver of chytridiomycosis disease dynamics. Despite various elaborations of this hypothesis in the literature for explaining amphibian declines (e.g., the chytrid thermal-optimum hypothesis) it has not been formally tested on infection patterns in the wild. In this study we developed a simple process-based model to simulate the growth of the pathogen Batrachochytrium dendrobatidis (Bd) under varying weather conditions to provide an a priori test of a weather-linked pathogen proliferation hypothesis for endemic chytridiomycosis. We found strong support for several predictions of the proliferation hypothesis when applied to our model species, Litoria pearsoniana, sampled across multiple sites and years: the weather-driven simulations of pathogen growth potential (represented as a growth index in the 30 days prior to sampling; GI30) were positively related to both the prevalence and intensity of Bd infections, which were themselves strongly and positively correlated. In addition, a machine-learning classifier achieved ∼72% success in classifying positive qPCR results when utilising just three informative predictors 1) GI30, 2) frog body size and 3) rain on the day of sampling. Hence, while intrinsic traits of the individuals sampled (species, size, sex) and nuisance sampling variables (rainfall when sampling) influenced infection patterns obtained when sampling via qPCR, our results also strongly suggest that weather-linked pathogen proliferation plays a key role in the infection dynamics of endemic chytridiomycosis in our study system. Predictive applications of the model include surveillance design, outbreak preparedness and response, climate change scenario modelling and the interpretation of historical patterns of amphibian decline.

Diet of Leptodactylus fuscus (Amphibia: Anura: Leptodactylidae) in the Pantanal of Miranda river, Brazil

Amphibians are usually generalist predators, and their diet is influenced by extrinsic (e.g. food availability) and intrinsic factors (e.g. body size and skull shape). This study aims to describe the diet of adult males and females of Leptodactylus fuscus in the Pantanal of the Miranda river and to answer the following questions: i) Are prey's maximum size and number of food items explained by the anuran's body size? ii) Are richness of morphospecies and number of food items explained by frog sex? iii) Is there diet overlap between male and female? We recorded 62 food items, belonging to seven orders of Arthropoda, and one individual of Annelida. The diet of L. fuscus was dominated by Orthoptera, followed by Coleoptera, Araneae, Hymenoptera, Blattaria, Hemiptera and Diptera. Frog's body size did not influence prey size or number of food items consumed. The number of prey and richness of morphospecies did not differ between males and females. There was low diet overlap between the sexes. Our results provide evidence for the opportunistic and generalist feeding behavior of L. fuscus.

Composición de la dieta de Craugastor lineatus (Anura: Craugastoridae) de Chiapas, México

Se describen los cambios ontogenéticos y estacionales de la dieta de Craugastor lineatus de Chiapas, México. De 54 contenidos estomacales de nueve juveniles, 38 machos y siete hembras, recuperamos 121 presas que representan 22 categorías de alimento. De estas, arañas, coleópteros, hormigas, isópodos, ortópteros, quilópodos y materia vegetal fueron las más importantes. El tamaño máximo de la presa estuvo relacionado positivamente con el tamaño de la rana, mientras que la relación con el número de presas fue negativa. Asimismo, los juveniles consumieron más coleópteros e isópodos que los adultos, quienes seleccionaron arañas, ortópteros y quilópodos. En la época húmeda encontramos 16 categorías de alimento, de las que ácaros, dípteros, isópteros y lepidópteros fueron exclusivas, mientras que en la época seca fueron 18 categorías, con diplópodos, fásmidos, odonatos, socópteros y seudoescorpiones como exclusivas.

Trophic Niche Variation and Individual Specialization inHypsiboas pulchellus(Duméril and Bibron, 1841) (Anura, Hylidae) from Uruguay

6 Corresponding author. ABSTRACT. Intrapopulation variation includes age and sexual variation, but also individual niche specialization. Individual specialization has important effects on dynamics at population or community levels. Environmental variation and intraspecific interactions are factors that can promote or enhance this kind of variation. Despite its relevance, knowledge about individual specialization in amphibians is still scarce, especially in species from temperate regions. In this study we analyzed the intrapopulational variation of the trophic niche in Hypsiboas pulchellus from a population in southern Uruguay. Particularly, we analyzed ontogenetic and sexual variation and individual specialization of the diet. We found ontogenetic variation in diet as a result of a shift from flies to beetles with increasing body size of frogs, but there were no differences in diet between males and females. We also found evidence of individual specialization, which varied seasonally together with population trophic niche width; during the warm season (October-March), individual specialization and population TNW both increased.

A Minute New Ecuadorian Andean Frog (Anura: Strabomantidae, Pristimantis)

We describe a new species of Pristimantis from a cloud forest at 2450–2800 m in the Cordillera Oriental in southern Ecuador (Zamora Chinchipe). The new species has a maximum snout–vent length of 17.9 mm (average SVL of 21 males = 12.3 mm ± 1.2, and of 19 females = 15.9 mm ± 1.3). This new species is the second smallest frog from Ecuador and smallest Pristimantis. Morphologically and phylogenetically, the new species is similar to P. caeruleonotus and P. colodactylus. It is distinguished from them and its congeners by its size, tuberculation, a distinct color pattern consisting of tan blotches on dorsum, spots on a brown venter, minute brown spots on anterior and posterior surfaces of the thighs, and other morphological features. Determination of small body size in frogs is discussed and meristic data of 40 minute frogs are compiled.

SPECIES AFFINITY AND INFRACOMMUNITY ORDINATION OF HELMINTHS OF LEPTODACTYLUS CHAQUENSIS (ANURA: LEPTODACTYLIDAE) IN TWO CONTRASTING ENVIRONMENTS FROM NORTHEASTERN ARGENTINA

One hundred seventy-two frogs (Leptodactylus chaquensis) were collected from November 2002 to November 2003, in agricultural (n = 132) and nonagricultural (n = 40) areas. Both sites are near the city of Corrientes, Argentina. The main goals of this study were as follows: (1) to determine the helminth parasite community in agricultural and nonagricultural habitats; (2) to analyze the relationships between helminth parasites and site of infection, frog body size, and gender; (3) to identify and examine covariation and association of helminth communities; and (4) to determine the mean richness and diversity of parasite communities. The helminth compound community of this amphibian species consisted of 24 species: 19 in agricultural habitats and 18 in nonagricultural habitats. The mean richness, mean diversity, and evenness of helminths were significantly different between the habitats (P < 0.05). The body size of the host was the important factor in determining parasite richness. Both habitats exhibited differences in community ordination. The helminth species in the 2 habitats exhibited the same interspecific relationships, although differences were observed in the intensity of infection.

Helminth community structure of the oven frog Leptodactylus latinasus (Anura, Leptodactylidae) from Corrientes, Argentina

AbstractA total of 36 adult individuals of Leptodactylus latinasus were collected near the city of Corrientes, Province of Corrientes in Argentina. The main goals of this study were: (1) to determine the helminth parasite fauna of L. latinasus; (2) to determine the richness and diversity of parasites at the component and infracommunity levels; (3) to analyze the relationships between helminth, frog body size and sex, and (4) to identify and examine species affinity of helminth communities. The helminth component community of this frog’s population consisted of 17 species. The predominant groups of parasites were the trematodes (adults: Glypthelmins repandum, Catadiscus inopinatus and Haematoloechus longiplexus; larvae: Travtrema aff. stenocotyle, Bursotrema aff. tetracotyloides, Styphlodora sp., unknown opisthogonimid species, Petasiger sp. and unknown strigeid species), followed by the nematodes (Cosmocerca podicipinus, C. parva, C. rara, C. cruzi, Schrankiana schranki and Aplectana hylambatis); other groups of parasites were represented by only one species (unknown larval cestode species and Centrorhynchus sp.). All parasite helminth species showed an aggregated pattern of distribution. The most infected organs were kidneys, small intestine, large intestine and pharyngeal zone. The host body size was important in determining the parasites abundance of G. repandum. At the level of component community G. repandum was the species with highest prevalence of infection and Bursotrema aff. tetracotyloides was the dominant species. Helminth species showed four significant pairs of covariation and two significant pairs of association in the infracommunities of Leptodactylus latinasus.

Coexistence of helminth species in Lysapsus limellus (Anura: Pseudidae) from an Argentinean subtropical area: influence of biotic and abiotic factors.

The need for studies on helminth communities of South American amphibians was addressed by examining changes in composition and population dynamics of the helminth component and infracommunities in the frog Lysapsus limellus Cope, 1862, from 1994 to 1996. Two pond types were considered, one permanent and one semipermanent. The main goals of this study were (1) to investigate the relationships between pond type, season, study time, frog body size, and frog sex and the presence-absence and counts of helminth parasite species in the frog host, L. limellus, and (2) to examine the co-occurrence of the different parasite species in the frog host in terms of the structure, assembly, and dynamics of the helminth infracommunity. Parasite presence and absence were analyzed using logistic regression and parasite counts were analyzed using log-linear modeling. To examine the association between parasite species, a principal components analysis was carried out on the correlation matrix for the counts. The pattern of co-occurrences was also examined through a randomization test. The main results were as follows: (1) five parasite species were found in the infracommunity; (2) the pond type and the host size class were the principal factors related to the presence and absence of parasites for the three dominant species, while the year of study and the host sex were only important for one of the species; (3) for the parasite counts, many more factors were significant, with body size class and pond type always important factors for the three core species of the infracommunity, with season, year of study, and sex also sometimes important, and (4) strong associations were observed between some helminth species of the host from the permanent pond, but the same species did not co-occur in frogs in the semipermanent pond. The life histories of the five species can be considered as opportunistic or "r strategists."

Myrmecophagy in a Ranid Frog Rana rugosa: Specialization or Weak Avoidance to Ant Eating

Abstract We studied diets of an Asian ranid, Rana rugosa, inhabiting three different environments (reservoir, river shoreline, and paddy fields) in Kyoto, Japan. In all the three habitats, ants were the most frequently consumed prey, representing surprisingly similar proportions in both the frequency of occurrence (81.9–85.7%) and the number of total prey items (56.8–59.4%). These values are exceptionally large for Rana, and equivalent to those reported for ant specialists in other families of frogs such as dendrobatids or bufonids. However, R. rugosa consumed ants lower in proportions than those found in the environment, and could not be regarded as purely ant specialists. Instead, we conclude that this species tends to avoid ants more weakly than other species of Rana. Other than ants, larger prey were more and smaller ones less frequently taken in proportion to frog body size, indicating that the frog consumes ants because of its weak avoidance of these abundant potential prey.

CORRELATIONS OF QUANTITATIVE PARAMETERS OF FECUNDITY IN AMPHIBIANS.

Salthe (1969), Salthe and Duellman (1973), and Salthe and Mecham (1974) generalized the published data on body size of the females, clutch size, ovum size, and reproductive mode of various amphibian species. For example, they recognized a positive interspecific correlation between ovum size and female body size in frogs within a given reproductive mode and a negative correlation between clutch size and ovum size regardless of differences in reproductive mode. Since these relationships of body size, clutch size, and ovum size should have been established during the evolutionary process as one of the adaptive features in each species, it is an interesting problem to examine whether the same sort of relationships are also found within each species. The data on which the above studies were based were from a large literature, and close examination of this literature reveals several defects for drawing relevant conclusions on the relationships of these parameters within as well as between species. There are only a few papers describing precise number and size of eggs from individual females, and, in most papers, the statistics are obtained from indirect methods. For instance, Tilley (1968) counted the number of follicles larger than 1 mm as the clutch size of five desmognathine salamanders, Bruce (1969) estimated the clutch size of four plethodontid salamanders from the yolked oocytes in the ovary, and Inger and Bacon (1968) determined the number of eggs of six Bornean frogs from the ratio of left ovary volume to 50 eggs removed from it. All these investigations were based on the preserved specimens. Only two papers deal with live animals. H6nig (1966) counted and measured the eggs obtained by spontaneous ovulation from the common frog, Rana temporaria, and Pettus and Angleton (1967) made the same kind of observations on eggs obtained by induced ovulation from the chorus frog, Pseudacris triseriata. The former study is obviously superior to the others in that it deals with weight, instead of length or volume, of females and eggs, although no correlation coefficient nor regression is given. Because the reproductive cost to the female of a given species should be expressed in terms of weight relationships, the weight parameters are more pertinent than the length or volume parameters. Since the intraspecific relationships between the reproductive parameters probably precede the interspecific relationships (Salthe and Duellman, 1973), comparative analyses on relationships both within and between species are critical for elucidating the adaptive evolution of reproductive strategies. From this point of view, the quantitative relationships among the weight parameters of eggs and adult females of 12 amphibian species from Japan were examined.