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1
McAlpine, Donald F. "Helminth communities in bullfrogs (Rana catesbeiana), green frogs (Rana clamitans), and leopard frogs (Rana pipiens) from New Brunswick, Canada". Canadian Journal of Zoology 75, n. 11 (1 novembre 1997): 1883–90. http://dx.doi.org/10.1139/z97-818.
Testo completoAbstract (sommario):
Twenty-three helminth species were identified from bullfrogs, Rana catesbeiana, green frogs, R. clamitans, and leopard frogs, R. pipiens, in New Brunswick. Digeneans dominated adult helminth communities in the aquatic bullfrog and semi-aquatic green frog; nematodes were dominant in the more terrestrial leopard frog. In green frogs and leopard frogs, richness and abundance were greatest in adults; in bullfrogs, juveniles showed the greatest richness and abundance. An increase in vertebrates in the diet of adult bullfrogs influences helminth communities in bullfrogs. Where Glypthelmins quieta and nematodes, which infect the host by skin penetration, predominate in green frogs and leopard frogs, respectively, the increase in epidermal area with age probably influences helminth abundance. Adult female leopard frogs are larger than males and harbour greater numbers of helminths. Within the most heavily sampled component communities only larval digeneans, and less frequently nematodes with direct life cycles, were common (i.e., in > 50% of hosts); other taxa were generally present at prevalences of < 20% and intensities of < 10 helminths per frog. Although wetland characteristics and helminth transmission dynamics play a role in producing variation in helminth communities among sites, ontogenetic shifts in diet and sexual size dimorphism within these anuran species are important in shaping helminth communities in individual frog hosts.
2
Woinarski, J. C. Z., S. M. Legge, L. A. Woolley, R. Palmer, C. R. Dickman, J. Augusteyn, T. S. Doherty et al. "Predation by introduced cats Felis catus on Australian frogs: compilation of species records and estimation of numbers killed". Wildlife Research 47, n. 8 (2020): 580. http://dx.doi.org/10.1071/wr19182.
Testo completoAbstract (sommario):
Abstract ContextWe recently estimated the numbers of reptiles, birds and mammals killed by cats (Felis catus) in Australia, with these assessments providing further evidence that cats have significant impacts on Australian wildlife. No previous studies have estimated the numbers of frogs killed by cats in Australia and there is limited comparable information from elsewhere in the world. AimsWe sought to (1) estimate the numbers of frogs killed by cats in Australia and (2) compile a list of Australian frog species known to be killed by cats. MethodsFor feral cats, we estimated the number of frogs killed from information on their frequency of occurrence in 53 cat dietary studies (that examined stomach contents), the mean number of frogs in dietary samples that contained frogs, and the numbers of cats in Australia. We collated comparable information for take of frogs by pet cats, but the information base was far sparser. Key resultsFrogs were far more likely to be reported in studies that sampled cat stomachs than cat scats. The mean frequency of occurrence of frogs in cat stomachs was 1.5%. The estimated annual per capita consumption by feral cats in Australia’s natural environments is 44 frogs, and, hence, the annual total take is estimated at 92 million frogs. The estimated annual per capita consumption by pet cats is 0.26 frogs, for a total annual kill of one million frogs by pet cats. Thirty native frog species (13% of the Australian frog fauna) are known to be killed by cats: this tally does not include any of the 51 threatened frog species, but this may simply be because no cat dietary studies have occurred within the small ranges typical of threatened frog species. ConclusionsThe present study indicated that cats in Australia kill nearly 100 million frogs annually, but further research is required to understand the conservation significance of such predation rates. ImplicationsThe present study completed a set of reviews of the impacts of cats on Australian terrestrial vertebrates. Cat predation on Australian frogs is substantial, but is likely to be markedly less than that on Australian reptiles, birds and mammals.
3
Folt, Brian, e Craig Guyer. "Habitat-dependent effects of predatory spiders on prey frogs in a Neotropical wet forest". Journal of Tropical Ecology 37, n. 5 (16 agosto 2021): 214–21. http://dx.doi.org/10.1017/s0266467421000274.
Testo completoAbstract (sommario):
AbstractIn seasonal wet Neotropical forests, many studies have suggested that species-rich terrestrial frog assemblages are regulated bottom-up by the abundance of leaf litter. However, terrestrial frogs are prey to a diverse community of predators, and no studies have tested for top-down effects of predators on this or other anuran assemblages. Here, we used an extensive field dataset to model the relative contribution of food resources, microhabitat resources and predators towards the occupancy and detection of two frog species (Craugastor bransfordii and Oophaga pumilio) at La Selva, Costa Rica. Frog occupancy was most strongly influenced by predatory spiders and secondarily influenced by the abundance of leaf litter. Predators exerted stronger effects on frogs than food resources, and frogs avoided predators more as leaf litter decreased. Detection probability was elevated when predators were present. We found support for bottom-up effects of leaf litter on the terrestrial frog assemblage, but top-down effects by predators exerted stronger effects on frog occupancy and detection. Because predator avoidance varied along a resource gradient, predator and resource effects appear to be dependent, supporting interactions between top-down and bottom-up mechanisms. Climate-driven decreases in leaf litter may drive decreased availability of frog refugia and increased interactions between frogs and predators.
4
Paluh, Daniel J., Edward L. Stanley e David C. Blackburn. "Evolution of hyperossification expands skull diversity in frogs". Proceedings of the National Academy of Sciences 117, n. 15 (27 marzo 2020): 8554–62. http://dx.doi.org/10.1073/pnas.2000872117.
Testo completoAbstract (sommario):
Frogs (Anura) are one of the most diverse vertebrate orders, comprising more than 7,000 species with a worldwide distribution and extensive ecological diversity. In contrast to other tetrapods, frogs have a highly derived body plan and simplified skull. In many lineages of anurans, increased mineralization has led to hyperossified skulls, but the function of this trait and its relationship with other aspects of head morphology are largely unexplored. Using three-dimensional morphological data from 158 species representing all frog families, we assessed wide-scale patterns of shape variation across all major lineages, reconstructed the evolutionary history of cranial hyperossification across the anuran phylogeny, and tested for relationships between ecology, skull shape, and hyperossification. Although many frogs share a conserved skull shape, several extreme forms have repeatedly evolved that commonly are associated with hyperossification, which has evolved independently more than 25 times. Variation in cranial shape is not explained by phylogenetic relatedness but is correlated with shifts in body size and ecology. The species with highly divergent, hyperossified skulls often have a specialized diet or a unique predator defense mechanism. Thus, the evolution of hyperossification has repeatedly facilitated the expansion of the head into multiple new shapes and functions.
5
McCAY, MICHAEL G. "AERODYNAMIC STABILITY AND MANEUVERABILITY OF THE GLIDING FROG POLYPEDATES DENNYSI". Journal of Experimental Biology 204, n. 16 (15 agosto 2001): 2817–26. http://dx.doi.org/10.1242/jeb.204.16.2817.
Testo completoAbstract (sommario):
SUMMARY Gliding has evolved independently in two families of tree frog. Tree frogs glide to descend rapidly to mating sites over temporary pools on the forest floor or to escape predators. The physical mechanisms used by frogs to glide and maneuver were investigated using a combination of observations of live frogs (Polypedates dennysi) gliding in a tilted wind-tunnel and aerodynamic forces and torques measured from physical models of tree frogs in a wind-tunnel. Tree frogs maneuvered in the tilted wind-tunnel using two different turning mechanisms: a banked turn (the frog rolls into the turn) and a crabbed turn (the frog yaws into the turn). Polypedates dennysipossessed overall weak aerodynamic stability: slightly stable about the pitch and roll axis, slightly unstable about the yaw axis. The maneuverability of gliding tree frogs was quantified using a maneuverability index. The maneuverability of tree frogs was roughly equivalent for tree frogs performing a banked turn and performing a crabbed turn. The maneuverability of tree frogs was approximately one-third of the maneuverability of a falcon (Falcon jugger).
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Smith, Lora L., Jennifer M. Howze, Jennifer S. Staiger, Eric R. Sievers, Deborah Burr e Kevin M. Enge. "Added Value: Gopher Tortoise Surveys Provide Estimates of Gopher Frog Abundance in Tortoise Burrows". Journal of Fish and Wildlife Management 12, n. 1 (27 ottobre 2020): 3–11. http://dx.doi.org/10.3996/jfwm-20-030.
Testo completoAbstract (sommario):
Abstract The gopher frog Lithobates capito is one of the most terrestrial frogs in the southeastern United States and often inhabits gopher tortoise burrows Gopherus polyphemus outside of the breeding season. Gopher frog populations have declined, and the species is under review for listing as threatened or endangered under the U.S. Endangered Species Act. Much of our knowledge on the status of gopher frogs is based on detections of larvae at breeding wetlands, which can be challenging because of environmental variability and provides no information on the terrestrial life stages of the species. Therefore, an alternative method is called for. We recorded observations of gopher frogs during gopher tortoise surveys at four conservation lands in Florida and used line-transect distance sampling to estimate frog abundance. We also recorded burrow size, incidence of frog co-occupancy with tortoises, and distance from frog-occupied burrows to breeding wetlands. We observed 274 gopher frogs in 1,097 tortoise burrows at the four sites. The proportion of burrows occupied by gopher frogs among sites ranged from 0.17 to 0.25. Gopher frog abundance in tortoise burrows was 742 (512–1,076 95% CL) at Etoniah Creek State Forest, 465 (352–615) at Ft. White Wildlife Environmental Area, 411 (283–595) at Mike Roess Gold Head Branch State Park, and 134 (97–186) at Watermelon Pond Wildlife Environmental Area. We observed up to four frogs in a single burrow. The proportion of frogs detected in burrows occupied by a gopher tortoise ranged from 0.46 to 0.79 among sites, and overall, gopher frogs preferred burrows occupied by tortoises over unoccupied burrows (χ2 = 15.875; df = 3; P = 0.001). Gopher frogs used burrows from 7 to 43 cm in width; mean width of frog-occupied burrows did not differ from that of unoccupied burrows (F1,3 = 0.049, P = 0.825). Distance from frog-occupied tortoise burrows to the nearest breeding wetland ranged from 141 to 3,402 m. Our data on gopher frogs collected in conjunction with gopher tortoise monitoring efforts using line-transect distance sampling and burrow cameras provided novel information on frog abundance in their terrestrial habitat and required no additional effort. However, the extent to which frogs use tortoise burrows relative to other available refuges (small mammal burrows, stumps, or other structures) is unknown; thus, our estimates should be considered conservative. We suggest that terrestrial abundance estimates for gopher frogs can complement efforts to monitor breeding activity to provide a more comprehensive means of monitoring population trends in this cryptic species.
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Rhebergen, F., R. C. Taylor, M. J. Ryan, R. A. Page e W. Halfwerk. "Multimodal cues improve prey localization under complex environmental conditions". Proceedings of the Royal Society B: Biological Sciences 282, n. 1814 (7 settembre 2015): 20151403. http://dx.doi.org/10.1098/rspb.2015.1403.
Testo completoAbstract (sommario):
Predators often eavesdrop on sexual displays of their prey. These displays can provide multimodal cues that aid predators, but the benefits in attending to them should depend on the environmental sensory conditions under which they forage. We assessed whether bats hunting for frogs use multimodal cues to locate their prey and whether their use varies with ambient conditions. We used a robotic set-up mimicking the sexual display of a male túngara frog ( Physalaemus pustulosus ) to test prey assessment by fringe-lipped bats ( Trachops cirrhosus ). These predatory bats primarily use sound of the frog's call to find their prey, but the bats also use echolocation cues returning from the frog's dynamically moving vocal sac. In the first experiment, we show that multimodal cues affect attack behaviour: bats made narrower flank attack angles on multimodal trials compared with unimodal trials during which they could only rely on the sound of the frog. In the second experiment, we explored the bat's use of prey cues in an acoustically more complex environment. Túngara frogs often form mixed-species choruses with other frogs, including the hourglass frog ( Dendropsophus ebraccatus ). Using a multi-speaker set-up, we tested bat approaches and attacks on the robofrog under three different levels of acoustic complexity: no calling D. ebraccatus males, two calling D. ebraccatus males and five D. ebraccatus males. We found that bats are more directional in their approach to the robofrog when more D. ebraccatus males were calling. Thus, bats seemed to benefit more from multimodal cues when confronted with increased levels of acoustic complexity in their foraging environments. Our data have important consequences for our understanding of the evolution of multimodal sexual displays as they reveal how environmental conditions can alter the natural selection pressures acting on them.
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DeMarchi, Joseph A., Andrew Britton, Kaylee O'Donnell e Ralph A. Saporito. "Behavioural preference for low levels of UV-B radiation in two neotropical frog species from Costa Rica". Journal of Tropical Ecology 34, n. 5 (6 agosto 2018): 336–40. http://dx.doi.org/10.1017/s0266467418000287.
Testo completoAbstract (sommario):
Abstract:Tropical frogs experience damaging effects from exposure to UV-B radiation, and some diurnally active, conspicuous species exhibit avoidance behaviours to high levels of UV-B. To determine if similar behaviours are present in other diurnal frogs, we experimentally compared UV-B avoidance in two common species of neotropical diurnal frogs – Oophaga pumilio, an aposematic poison frog and Craugastor bransfordii, a cryptic leaf-litter frog – in response to different levels of UV-B. Wild-caught frogs were tested in experimental arenas fitted with filters that permitted two different levels of UV-B (low: 14% vs. high: 84% UV-B). Both species spent significantly more time under the low UV-B filter, suggesting that behavioural preferences for lower levels of UV-B are common to different diurnal species. Furthermore, male O. pumilio significantly preferred lower levels of UV-B, whereas females did not exhibit a preference for lower UV-B, which may suggest differences in UV-B exposure or sensitivity and/or alternative mechanism(s) to avoid UV-B between sexes. Although limited in scope, the findings of our study suggest that UV-B avoidance may be a behavioural adaptation common to all diurnal frogs.
9
Tokita, Masayoshi, e Noriko Iwai. "Development of the pseudothumb in frogs". Biology Letters 6, n. 4 (10 febbraio 2010): 517–20. http://dx.doi.org/10.1098/rsbl.2009.1038.
Testo completoAbstract (sommario):
Frogs have highly conserved hand and foot morphology, possessing four fingers and five toes. As an exception, two Japanese ranid frog species, the Otton frog Babina subaspera and the dagger frog Babina holsti , possess a unique thumb-like structure (the pseudothumb) in the forelimb, giving an appearance of a total of five fingers on the hand. To obtain insights into the developmental mechanisms that generate this novel character, we investigated the hand morphogenesis of the Otton frog. The unique morphological pattern of the pseudothumb was already established in juveniles. Surprisingly, the bud-like structure, which is similar to the area of inductive activity (e.g. feather buds in birds and the carapacial ridge in turtles), was detected over the site where the future prepollex develops in larvae. By contrast, this bud-like structure was not found in larvae of other ranid species. We discuss possible scenarios that would favour the evolution of this very unusual trait in frogs.
10
Feng, Yan-Jie, David C. Blackburn, Dan Liang, David M. Hillis, David B. Wake, David C. Cannatella e Peng Zhang. "Phylogenomics reveals rapid, simultaneous diversification of three major clades of Gondwanan frogs at the Cretaceous–Paleogene boundary". Proceedings of the National Academy of Sciences 114, n. 29 (3 luglio 2017): E5864—E5870. http://dx.doi.org/10.1073/pnas.1704632114.
Testo completoAbstract (sommario):
Frogs (Anura) are one of the most diverse groups of vertebrates and comprise nearly 90% of living amphibian species. Their worldwide distribution and diverse biology make them well-suited for assessing fundamental questions in evolution, ecology, and conservation. However, despite their scientific importance, the evolutionary history and tempo of frog diversification remain poorly understood. By using a molecular dataset of unprecedented size, including 88-kb characters from 95 nuclear genes of 156 frog species, in conjunction with 20 fossil-based calibrations, our analyses result in the most strongly supported phylogeny of all major frog lineages and provide a timescale of frog evolution that suggests much younger divergence times than suggested by earlier studies. Unexpectedly, our divergence-time analyses show that three species-rich clades (Hyloidea, Microhylidae, and Natatanura), which together comprise ∼88% of extant anuran species, simultaneously underwent rapid diversification at the Cretaceous–Paleogene (K–Pg) boundary (KPB). Moreover, anuran families and subfamilies containing arboreal species originated near or after the KPB. These results suggest that the K–Pg mass extinction may have triggered explosive radiations of frogs by creating new ecological opportunities. This phylogeny also reveals relationships such as Microhylidae being sister to all other ranoid frogs and African continental lineages of Natatanura forming a clade that is sister to a clade of Eurasian, Indian, Melanesian, and Malagasy lineages. Biogeographical analyses suggest that the ancestral area of modern frogs was Africa, and their current distribution is largely associated with the breakup of Pangaea and subsequent Gondwanan fragmentation.
11
Rowley, Jodi J. L., e Corey T. Callaghan. "The FrogID dataset: expert-validated occurrence records of Australia’s frogs collected by citizen scientists". ZooKeys 912 (17 febbraio 2020): 139–51. http://dx.doi.org/10.3897/zookeys.912.38253.
Testo completoAbstract (sommario):
This dataset represents expert-validated occurrence records of calling frogs across Australia collected via the national citizen science project FrogID (http://www.frogid.net.au). FrogID relies on participants recording calling frogs using smartphone technology, after which point the frogs are identified by expert validators, resulting in a database of georeferenced frog species records. This dataset represents one full year of the project (10 November 2017–9 November 2018), including 54,864 records of 172 species, 71% of the known frog species in Australia. This is the first instalment of the dataset, and we anticipate providing updated datasets on an annual basis.
12
Smotherman, M. S., e P. M. Narins. "Hair cells, hearing and hopping: a field guide to hair cell physiology in the frog". Journal of Experimental Biology 203, n. 15 (1 agosto 2000): 2237–46. http://dx.doi.org/10.1242/jeb.203.15.2237.
Testo completoAbstract (sommario):
For more than four decades, hearing in frogs has been an important source of information for those interested in auditory neuroscience, neuroethology and the evolution of hearing. Individual features of the frog auditory system can be found represented in one or many of the other vertebrate classes, but collectively the frog inner ear represents a cornucopia of evolutionary experiments in acoustic signal processing. The mechano-sensitive hair cell, as the focal point of transduction, figures critically in the encoding of acoustic information in the afferent auditory nerve. In this review, we provide a short description of how auditory signals are encoded by the specialized anatomy and physiology of the frog inner ear and examine the role of hair cell physiology and its influence on the encoding of sound in the frog auditory nerve. We hope to demonstrate that acoustic signal processing in frogs may offer insights into the evolution and biology of hearing not only in amphibians but also in reptiles, birds and mammals, including man.
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Hazell, Donna. "Frog ecology in modified Australian landscapes: a review". Wildlife Research 30, n. 3 (2003): 193. http://dx.doi.org/10.1071/wr02075.
Testo completoAbstract (sommario):
Frog decline in Australia has often occurred where habitat is relatively intact. Habitat alteration and loss do, however, threaten many species. Widespread degradation of aquatic and terrestrial systems has occurred since European settlement, with only 6.4% of Australia's landmass reserved for conservation. But what do we know about how frogs use modified Australian landscapes? Do wildlife managers have the information required to ensure that frog habitat is considered in the management and revegetation of these areas? This review examines published Australian research on frogs to determine knowledge on processes of habitat loss and degradation. Literature that informs landscape restoration and revegetation is also examined to determine whether the habitat needs of frogs are considered. While many threats associated with frog habitat loss and change have been identified there is little quantitative information on frog–habitat relationships in modified landscapes, habitat fragmentation or knowledge of the connectivity required between terrestrial and aquatic frog habitat. Without this information frogs have largely been ignored in efforts to revegetate and manage for the conservation of Australian biota outside reserves. Ecological frog research in modified landscapes is required to avoid land-management decisions and conservation strategies based on inappropriate assumptions of how biota respond to landscape change.
14
Dahl, Chris, Stephen J. Richards e Vojtech Novotny. "The Sepik River (Papua New Guinea) is not a dispersal barrier for lowland rain-forest frogs". Journal of Tropical Ecology 29, n. 6 (11 settembre 2013): 477–83. http://dx.doi.org/10.1017/s0266467413000527.
Testo completoAbstract (sommario):
Abstract:Major tropical rivers have been suggested to be important dispersal barriers that increase the beta diversity of animal communities in lowland rain forests. We tested this hypothesis using assemblages of frogs in the floodplains of the Sepik River, a major river system in Papua New Guinea. We surveyed frogs at five sites within a continuous 150 × 500-km area of lowland rain forest bisected by the Sepik, using standardized visual and auditory survey techniques. We documented 769 frogs from 44 species. The similarity in species composition decreased with logarithm of geographical distance between the sites, which ranged from 82 to 465 km. The similarity decay did not depend on whether or not the compared sites were separated by the Sepik River or whether the species were aquatic or terrestrial breeders. Likewise, a DCA ordination of frog assemblages did not show separation of sites by the river as a significant factor explaining their composition. Our results suggest that even major rivers, such as the Sepik, may not act as dispersal barriers. Rivers may not limit the distribution of frogs and therefore have a limited effect on determining frog species abundance and assemblage structure in rain forests.
15
Withers, Philip C. "Evaporative water loss and the role of cocoon formation in Australian frogs". Australian Journal of Zoology 46, n. 5 (1998): 405. http://dx.doi.org/10.1071/zo98013.
Testo completoAbstract (sommario):
Measurements of evaporative water loss (EWL; mg min-1) and resistance (R; sec cm-1) for various Australian frogs indicate three general allometric patterns: non-cocooned and non-‘waterproof’ frogs with EWL ∝ Mass0.30 and R independent of body mass at about 1–3 sec cm-1, cocooned frogs with EWL reduced about 50–200-fold and R about 50–200 sec cm-1, and ‘waterproof’ frogs with EWL reduced about 5–100- fold and R about 5–100 sec cm-1. Cocooned frogs have an exponential reduction in EWL and fairly linear increase in R over time, corresponding to the temporal addition of layers to the cocoon. The biophysical properties of cocoon are generally similar for various species, although there is some variation in both resistance per thickness (5–20 × 104 s cm-2) and diffusion coefficient (0.4–2.4 × 10 –5 cm2 s-1). The hygroscopic property of frog cocoon resembles that of mammalian stratum corneum, hair and wool, and mucopolysaccharides; there is a slight increase in water content of cocoon over a wide range of humidities but a very steep increase in water content and substantial hydration and swelling at >96% RH. This extreme hygroscopic behaviour of frog cocoon at very high RH may reflect less polymer cross-linking in frog cocoon and its high digestibility. The prevention of over-hydration of frog cocoon in vivo may be attributed to the restriction of high water content to only very high RH (>96%).
16
Costanzo, Jon P., e Richard E. Lee Jr. "Cryoprotectant production capacity of the freeze-tolerant wood frog, Rana sylvatica". Canadian Journal of Zoology 71, n. 1 (1 gennaio 1993): 71–75. http://dx.doi.org/10.1139/z93-011.
Testo completoAbstract (sommario):
Freezing survival of the wood frog (Rana sylvatica) is enhanced by the synthesis of the cryoprotectant glucose, via liver glycogenolysis. Because the quantity of glucose mobilized during freezing bears significantly on the limit of freeze tolerance, we investigated the relationship between the quantity of liver glycogen and the capacity for cryoprotectant synthesis. We successfully augmented natural levels of liver glycogen by injecting cold-conditioned wood frogs with glucose. Groups of 8 frogs having mean liver glycogen concentrations of 554 ± 57 (SE), 940 ± 57, and 1264 ± 66 μmol/g catabolized 98.7, 83.4, and 52.8%, respectively, of their glycogen reserves during 24 h of freezing to −2.5 °C. Glucose concentrations concomitantly increased, reaching 21 ± 3, 102 ± 23, and 119 ± 14 μmol/g, respectively, in the liver, and 15 ± 3, 42 ± 5, and 61 ± 5 μmol/mL, respectively, in the blood. Because the capacity for cryoprotectant synthesis depends on the amount of liver glycogen, the greatest risk of freezing injury likely occurs during spring, when glycogen reserves are minimal. Non-glucose osmolites were important in the wood frog's cryoprotectant system, especially in frogs having low glycogen levels. Presumably the natural variation in cryoprotectant synthesis capacity among individuals and populations of R. sylvatica chiefly reflects differences in glycogen reserves; however, environmental, physiological, and genetic factors likely are also involved.
17
Halliday, William D., e Gabriel Blouin-Demers. "Habitat selection by Common Gartersnakes (Thamnophis sirtalis) is affected by vegetation structure but not by location of Northern Leopard Frog (Lithobates pipiens) prey". Canadian Field-Naturalist 132, n. 3 (11 aprile 2019): 223–30. http://dx.doi.org/10.22621/cfn.v132i3.1955.
Testo completoAbstract (sommario):
Understanding the factors affecting habitat selection of species is important for effective management and for conservation because habitat selection affects fitness. We tested the competing, but not mutually exclusive, hypotheses that habitat selection of Common Gartersnakes (Thamnophis sirtalis) at a fine spatial scale is driven by vegetation structure or by Northern Leopard Frog (Lithobates pipiens) prey abundance. We conducted surveys for snakes and frogs in six, 1-ha study grids in eastern Ontario in 2014 and 2015. Common Gartersnakes used areas dominated by forbs more than expected based on availability, and used grassy areas less than expected based on availability. Gartersnakes showed no preference for sites with more frogs. Thus, vegetation structure is important in habitat selection of Common Gartersnakes, but Northern Leopard Frog abundance is not. Common Gartersnakes and Northern Leopard Frogs did have a preference for forbs, but gartersnakes do not appear to be using habitat specifically based on frog abundance at a fine scale. Future work should study habitat use by snakes over a longer period to account for high variability in frog abundance and for temporal changes in habitat structure. Future work should also examine the distribution of other prey items in relation to the distribution of snakes.
18
Sun, Yan-Bo, Zi-Jun Xiong, Xue-Yan Xiang, Shi-Ping Liu, Wei-Wei Zhou, Xiao-Long Tu, Li Zhong et al. "Whole-genome sequence of the Tibetan frog Nanorana parkeri and the comparative evolution of tetrapod genomes". Proceedings of the National Academy of Sciences 112, n. 11 (2 marzo 2015): E1257—E1262. http://dx.doi.org/10.1073/pnas.1501764112.
Testo completoAbstract (sommario):
The development of efficient sequencing techniques has resulted in large numbers of genomes being available for evolutionary studies. However, only one genome is available for all amphibians, that of Xenopus tropicalis, which is distantly related from the majority of frogs. More than 96% of frogs belong to the Neobatrachia, and no genome exists for this group. This dearth of amphibian genomes greatly restricts genomic studies of amphibians and, more generally, our understanding of tetrapod genome evolution. To fill this gap, we provide the de novo genome of a Tibetan Plateau frog, Nanorana parkeri, and compare it to that of X. tropicalis and other vertebrates. This genome encodes more than 20,000 protein-coding genes, a number similar to that of Xenopus. Although the genome size of Nanorana is considerably larger than that of Xenopus (2.3 vs. 1.5 Gb), most of the difference is due to the respective number of transposable elements in the two genomes. The two frogs exhibit considerable conserved whole-genome synteny despite having diverged approximately 266 Ma, indicating a slow rate of DNA structural evolution in anurans. Multigenome synteny blocks further show that amphibians have fewer interchromosomal rearrangements than mammals but have a comparable rate of intrachromosomal rearrangements. Our analysis also identifies 11 Mb of anuran-specific highly conserved elements that will be useful for comparative genomic analyses of frogs. The Nanorana genome offers an improved understanding of evolution of tetrapod genomes and also provides a genomic reference for other evolutionary studies.
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Courtois, Daniel, Raymond Leclair jr., Sylvain Lacasse e Pierre Magnan. "Habitats préférentiels d'amphibiens ranidés dans des lacs oligotrophes du Bouclier laurentien, Québec". Canadian Journal of Zoology 73, n. 9 (1 settembre 1995): 1744–53. http://dx.doi.org/10.1139/z95-206.
Testo completoAbstract (sommario):
From a study of riparian habitat structure and a quantitive distribution survey of bullfrog, Rana catesbeiana, mink frog, Rana septentrionalis, and green frog, Rana clamitans melanota, in 31 oligotrophic lakes, we looked for, among 18 physiographic parameters, those that could best explain the spatial organisation of the ranid community. The three species cohabitated in 18 lakes, the mink frog and the green frog in 10 lakes without bullfrog, and the bullfrog alone in 3 lakes. These frogs preferentially occupied (i) habitats with medium or high density of emergent vegetation, (ii) areas with extensive floating aquatic vegetation, (iii) muddy and silty areas, and (iv) especially for the green frog, shrubby habitats with ericaceae. Substrates had a poor explicative value. In lakes devoid of bullfrogs, the mink frogs and green frogs were more frequently abundant and showed a more even distribution in the different habitats than when they were sympatric with bullfrogs. A Spearman's rank correlation analysis confirmed the similarity of habitat preferences between the three species and the poor capacity of the habitat structure to predict the ranid community composition.
20
Narayan, Edward, Frank Molinia, Ketan Christi, Craig Morley e John Cockrem. "Urinary corticosterone metabolite responses to capture, and annual patterns of urinary corticosterone in wild and captive endangered Fijian ground frogs (Platymantis vitiana)". Australian Journal of Zoology 58, n. 3 (2010): 189. http://dx.doi.org/10.1071/zo10010.
Testo completoAbstract (sommario):
This study was based on the development of a non-invasive glucocorticoid enzyme-immunoassay for the assessment of stress in wild and captive endangered Fijian ground frogs (Platymantis vitiana). Enzyme-immunoassays were developed and validated for the first time to non-invasively measure both cortisol and corticosterone metabolites in frog urine. Frog urine showed parallel displacement with corticosterone but not cortisol standards, therefore corticosterone enzyme immunoassays were used to examine stress in wild and captive frogs. Urinary corticosterone metabolite concentrations increased in frog urine (n = 4) at 6 h, 1 day and 2 days after injection with adrenocorticotropic hormone (0.44 μg g–1 bodyweight), indicating that the corticosterone enzyme-immunoassay could detect changes in circulating corticosterone in frogs. Urinary concentrations of corticosterone were measured in wild frogs (n = 18) after capture in the field. The first measurement beyond the initial sample was at 2–3 h. Mean urinary corticosterone concentrations rose after the initial sample and were significantly elevated in samples collected 3–4 h after capture. This is the first demonstration of a urinary corticosterone response to capture in amphibians. Urinary corticosterone metabolite concentrations for all months combined were lower in captive males than in wild males, and differed between vitellogenic, non-vitellogenic and captive females. Concentrations did not differ between captive and wild females. In conclusion, urinary corticosterone enzyme immunoassays can be used in frogs for assessing stress responses to capture and natural stress profiles of both captive and wild populations.
21
Ma, Wen-Juan, e Paris Veltsos. "The Diversity and Evolution of Sex Chromosomes in Frogs". Genes 12, n. 4 (26 marzo 2021): 483. http://dx.doi.org/10.3390/genes12040483.
Testo completoAbstract (sommario):
Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems.
22
Stuart, Bryan L., Robert F. Inger e Harold K. Voris. "High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs". Biology Letters 2, n. 3 (20 giugno 2006): 470–74. http://dx.doi.org/10.1098/rsbl.2006.0505.
Testo completoAbstract (sommario):
Amphibians tend to exhibit conservative morphological evolution, and the application of molecular and bioacoustic tools in systematic studies have been effective at revealing morphologically ‘cryptic’ species within taxa that were previously considered to be a single species. We report molecular genetic findings on two forest-dwelling ranid frogs from localities across Southeast Asia, and show that sympatric evolutionary lineages of morphologically cryptic frogs are a common pattern. These findings imply that species diversity of Southeast Asian frogs remains significantly underestimated, and taken in concert with other molecular investigations, suggest there may not be any geographically widespread, forest-dwelling frog species in the region. Accurate assessments of diversity and distributions are needed to mitigate extinctions of evolutionary lineages in these threatened vertebrates.
23
Layne, Jr.,, Jack R., e Matt E. Rice. "Postfreeze locomotion performance in wood frogs (Rana sylvatica) and spring peepers (Pseudacris crucifer)". Canadian Journal of Zoology 81, n. 12 (1 dicembre 2003): 2061–65. http://dx.doi.org/10.1139/z03-202.
Testo completoAbstract (sommario):
Freeze tolerance exists among a few species of terrestrially hibernating North American frogs such as the wood frog (Rana sylvatica) and the spring peeper (Pseudacris crucifer). We investigated jump distance and swimming speed of these two frog species during postfreeze recovery because impaired performance, even if reversible, could have adverse ecological consequences for these frogs. Following a nonlethal freeze at –1.5 °C, R. sylvatica returned to the prefreeze level of both modes of locomotion sooner than P. crucifer (54 h vs. 11 d or longer). Wood frogs recovered slowly following more intense freezes: a –4.0 °C treatment group failed to reach the prefreeze level after 11 d, and a –3.0 °C treatment group took 54 h to reach 50% of the prefreeze level. As a result of their diminished locomotive performance, frogs recovering from natural freezes may be temporarily less able to exploit environmental resources and less able to escape predators active in winter. Nevertheless, given the massive biochemical and physiological disturbances accompanying tissue freezing, the recovery dynamics in these frogs seem sufficiently rapid to minimize most ecological risks and to permit early spring breeding. The faster recovery of locomotion in R. sylvatica compared with P. crucifer is consistent, however, with its greater northward distribution.
24
King, Patricia A., Mary N. Rosholt e Kenneth B. Storey. "Seasonal changes in plasma membrane glucose transporters enhance cryoprotectant distribution in the freeze-tolerant wood frog". Canadian Journal of Zoology 73, n. 1 (1 gennaio 1995): 1–9. http://dx.doi.org/10.1139/z95-001.
Testo completoAbstract (sommario):
One of the critical adaptations for freeze tolerance by the wood frog, Rana sylvatica, is the production of large quantities of glucose as an organ cryoprotectant during freezing exposures. Glucose export from the liver, where it is synthesized, and its uptake by other organs is dependent upon carrier-mediated transport across plasma membranes by glucose-transporter proteins. Seasonal changes in the capacity to transport glucose across plasma membranes were assessed in liver and skeletal muscle of wood frogs; summer-collected (June) frogs were compared with autumn-collected (September) cold-acclimated (5 °C for 3–4 weeks) frogs. Plasma membrane vesicles prepared from liver of autumn-collected frogs showed 6-fold higher rates of carrier-mediated glucose transport than vesicles from summer-collected frogs, maximal velocity (Vmax) values for transport being 72 ± 14 and 12.0 + 2.9 nmol∙mg protein−1∙s−1, respectively (at 10 °C). However, substrate affinity constants for carrier-mediated glucose transport (K1/2) did not change seasonally. The difference in transport rates was due to greater numbers of glucose transporters in liver plasma membranes from autumn-collected frogs. The total number of transporter sites, as determined by cytochalasin B binding, was 8.5-fold higher in autumn than in summer. Glucose transporters in wood frog liver membranes cross-reacted with antibodies to the rat GluT-2 glucose transporter (the mammalian liver isoform), and Western blots further confirmed a large increase in transporter numbers in liver membranes from autumn- versus summer-collected frogs. By contrast with the liver, however, there were no seasonal changes in glucose-transporter activity or numbers in plasma membranes isolated from skeletal muscle. We conclude that an enhanced capacity for glucose transport across liver, but not muscle, plasma membranes during autumn cold-hardening is an important adaptation that anticipates the need for rapid export of cryoprotectant from liver during natural freezing episodes.
25
Booth, D. T. "Effect of soil type on burrowing behavior and cocoon formation in the green-striped burrowing frog, Cyclorana alboguttata". Canadian Journal of Zoology 84, n. 6 (giugno 2006): 832–38. http://dx.doi.org/10.1139/z06-062.
Testo completoAbstract (sommario):
This study examined the effect of soil type on burrowing behaviour and cocoon formation during aestivation in the green-striped burrowing frog, Cyclorana alboguttata (Günther, 1867). Given a choice, frogs always chose to burrow in wet sand in preference to wet clay. Frogs buried themselves faster and dug deeper burrows in sandy soil. However, under my laboratory conditions, there was little difference in the pattern of soil drying between the two soil types. Frogs in both sand and clay soil experienced hydrating conditions for the first 3 months and dehydrating conditions for the last 3 months of the 6-month aestivation period, and cocoons were not formed until after 3 months of aestivation. After 6 months, there were more layers in the cocoons of frogs aestivating in sand than those aestivating in clay. Frogs were able to absorb water from sandy soil with water potentials greater than –400 kPa, but lost water when placed on sand with a water potential of –1000 kPa.
26
Irwin, Jason T., Jon P. Costanzo e Richard E. Lee, Jr. "Terrestrial hibernation in the northern cricket frog, Acris crepitans". Canadian Journal of Zoology 77, n. 8 (1 novembre 1999): 1240–46. http://dx.doi.org/10.1139/z99-087.
Testo completoAbstract (sommario):
We used laboratory experiments and field observations to explore overwintering in the northern cricket frog, Acris crepitans, in southern Ohio and Indiana. Cricket frogs died within 24 h when submerged in simulated pond water that was anoxic or hypoxic, but lived 8-10 days when the water was oxygenated initially. Habitat selection experiments indicated that cricket frogs prefer a soil substrate to water as temperature decreases from 8 to 2°C. These data suggested that cricket frogs hibernate terrestrially. However, unlike sympatric hylids, this species does not tolerate extensive freezing: only 2 of 15 individuals survived freezing in the -0.8 to -2.6°C range (duration 24-96 h). Cricket frogs supercooled when dry (mean supercooling point -5.5°C; range from -4.3 to -6.8°C), but were easily inoculated by external ice at temperatures between -0.5 and -0.8°C. Our data suggested that cricket frogs hibernate terrestrially but are not freeze tolerant, are not fossorial, and are incapable of supercooling in the presence of external ice. Thus we hypothesized that cricket frogs must hibernate in terrestrial sites that adequately protect against freezing. Indeed, midwinter surveys revealed cricket frogs hibernating in crayfish burrows and cracks of the pond bank, where wet soils buffered against extensive freezing of the soil.
27
Martín, José, Juán José Luque-Larena e Pilar López. "Factors affecting escape behavior of Iberian green frogs (Rana perezi)". Canadian Journal of Zoology 83, n. 9 (1 settembre 2005): 1189–94. http://dx.doi.org/10.1139/z05-114.
Testo completoAbstract (sommario):
Theoretical models and empirical evidence suggest that prey should not flee immediately upon detecting an approaching predator, but instead should adjust their escape response to minimize the costs of flight. Similarly, after deciding to escape, animals should tend to adjust the magnitude and characteristics of their escape response according to the perceived level of predation risk. Although these hypotheses have been tested in some prey types, it remains for their applicability to a wider range of taxa to be ascertained and for a larger variety of microhabitat and environmental conditions to be considered. We simulated predator approaches to Iberian green frogs (Rana perezi Seoane, 1885) in the field. Frogs were approached while they were foraging alone at the edge of water, and they escaped by jumping into the water. Results showed that escape decisions of frogs are influenced by microhabitat variables and body size. Both the approach distance allowed to the predator and the distance jumped by the frogs in response to the approach were positively correlated with the initial distance of the frog from the water's edge; they were also dependent on vegetation cover at the edge of and in the water. Small frogs appeared to rely on crypsis more than large frogs and allowed shorter predator approach distances. They also remained still on the water surface after jumping more often than large frogs. We conclude that such flexibility in the escape response may allow frogs to reduce predation risk without incurring excessive costs.
28
Tarvin, Rebecca D., Juan C. Santos, Lauren A. O'Connell, Harold H. Zakon e David C. Cannatella. "Convergent Substitutions in a Sodium Channel Suggest Multiple Origins of Toxin Resistance in Poison Frogs". Molecular Biology and Evolution 33, n. 4 (18 gennaio 2016): 1068–80. http://dx.doi.org/10.1093/molbev/msv350.
Testo completoAbstract (sommario):
Abstract Complex phenotypes typically have a correspondingly multifaceted genetic component. However, the genotype–phenotype association between chemical defense and resistance is often simple: genetic changes in the binding site of a toxin alter how it affects its target. Some toxic organisms, such as poison frogs (Anura: Dendrobatidae), have defensive alkaloids that disrupt the function of ion channels, proteins that are crucial for nerve and muscle activity. Using protein-docking models, we predict that three major classes of poison frog alkaloids (histrionicotoxins, pumiliotoxins, and batrachotoxins) bind to similar sites in the highly conserved inner pore of the muscle voltage-gated sodium channel, Nav1.4. We predict that poison frogs are somewhat resistant to these compounds because they have six types of amino acid replacements in the Nav1.4 inner pore that are absent in all other frogs except for a distantly related alkaloid-defended frog from Madagascar, Mantella aurantiaca. Protein-docking models and comparative phylogenetics support the role of these replacements in alkaloid resistance. Taking into account the four independent origins of chemical defense in Dendrobatidae, phylogenetic patterns of the amino acid replacements suggest that 1) alkaloid resistance in Nav1.4 evolved independently at least five times in these frogs, 2) variation in resistance-conferring replacements is likely a result of differences in alkaloid exposure across species, and 3) functional constraint shapes the evolution of the Nav1.4 inner pore. Our study is the first to demonstrate the genetic basis of autoresistance in frogs with alkaloid defenses.
29
LeGros, David L., David Lesbarrères e Brad Steinberg. "Terrestrial dispersal of juvenile Mink Frog (Lithobates septentrionalis) in Algonquin Provincial Park, Ontario". Canadian Field-Naturalist 135, n. 1 (23 giugno 2021): 47–51. http://dx.doi.org/10.22621/cfn.v135i1.2607.
Testo completoAbstract (sommario):
Dispersal following metamorphosis is critical for sustaining anuran metapopulations. Mink Frog (Lithobates septentrionalis) is a primarily aquatic species that is common in eastern Canada. The species is not well studied, and little is known about the terrestrial dispersal of recently metamorphosed individuals. Here we present our observations on the phenology of terrestrial activity in recently metamorphosed Mink Frogs in Algonquin Provincial Park, Ontario, Canada. Despite a sampling effort of over 26 000 trap nights over two years (2010 and 2011) in an area with a known population of Mink Frogs, we observed only 35 individuals, all of which were recent metamorphs, in late summer 2011, suggesting annual variability of recruitment. Because all Mink Frogs were observed in a riparian area, it is likely that this species uses riparian corridors to disperse toward other wetlands, thus avoiding forested areas.
30
Lewis, B. D., e R. L. Goldingay. "Population monitoring of the vulnerable wallum sedge frog (Litoria olongburensis) in north-eastern New South Wales". Australian Journal of Zoology 53, n. 3 (2005): 185. http://dx.doi.org/10.1071/zo03063.
Testo completoAbstract (sommario):
The literature on the population ecology of Australian frogs provides relatively few accounts of population monitoring. This has hampered our ability to understand how frog populations respond to dynamic rainfall patterns and to determine the stability of populations of threatened frog species. We conducted biannual monitoring of the wallum sedge frog (Litoria olongburensis) along transects at 10 sites over a 4-year period (1996–2000). We recorded six environmental parameters to assess their influence on our population indices. Monitoring of transects indicated that populations were rarely stable and fluctuated from year to year. Counts of adults were negatively influenced by rain during the previous day but positively influenced by rain during the previous week. This suggests that timing of recent rainfall has a differing influence on habitat use by adult frogs. Counts of adults were also significantly influenced by site and census period. Numbers of juveniles were influenced by rain during the previous three months, which may suggest that successful recruitment depends on higher water levels in the sedge swamps. Counts of juveniles were also significantly influenced by census period. Our analysis reveals that, after controlling for the influence of rainfall, the number of adult frogs per census varied between 10 and 20 per transect. The number of juveniles varied between 5 and 15 per transect per census. We conclude that the wallum sedge frog across the geographic range of our sites was not in decline during our monitoring period. In light of our findings we provide a review on population monitoring of Australian frogs.
31
Klop-Toker, Kaya L., Jose W. Valdez, Michelle P. Stockwell, Matthew E. Edgar, Loren Fardell, Simon Clulow, John Clulow e Michael J. Mahony. "Assessing host response to disease treatment: how chytrid-susceptible frogs react to increased water salinity". Wildlife Research 44, n. 8 (2017): 648. http://dx.doi.org/10.1071/wr16145.
Testo completoAbstract (sommario):
Context The severity and prevalence of the amphibian fungal pathogen, Batrachochytrium dendrobatidis (Bd) is correlated with several environmental variables, including salinity, temperature, and moisture content, which influence the pathogen’s growth and survival. Habitats that contain these environmental variables at levels outside of those optimal for Bd growth and survival may facilitate the survival of susceptible host species. Therefore, manipulation of environmental salinity is a potential management strategy to help conserve Bd-susceptible species. However, host behaviour also influences disease dynamics, and the success of habitat manipulation programs depends on how hosts use this altered habitat. Aims To assess if the Bd-susceptible green and golden bell frog, Litoria aurea, will select waterbodies with a salinity increased to S=3; if this selection is affected by infection; and if a frog’s time in a waterbody of this salinity affects infection load or blood physiology. Methods We conducted a filmed choice experiment and a 3-year field study where infected and uninfected frogs could choose between fresh or saline waterbodies. Key results In both the laboratory experiment and field study, Bd-infected L. aurea spent a significantly greater amount of time in or closer to a waterbody than uninfected frogs. Experimentally infected frogs tended to prefer the saline water over fresh, but their choice of water usage did not differ statistically from uninfected frogs. In the field, frogs began to avoid ponds when salinities rose above S=5. Conclusions Because both wild and captive, and infected and uninfected L. aurea readily selected waterbodies with a salinity of S=3, this salinity could potentially be used as a passive method for reducing the severity of Bd when managing this species. However, further testing is needed to understand the efficacy of this treatment, and care must be taken to prevent salinities rising above S=5, because this level seems to produce an avoidance response and therefore may not be suitable in every location. Implications Manipulation of aquatic habitats may be a worthwhile focus for Bd management in habitats where water level fluctuations are minimal.
32
Madsen, T., e R. Shine. "Toxicity of a tropical Australian frog, Litoria dahlii, to sympatric snakes". Wildlife Research 21, n. 1 (1994): 21. http://dx.doi.org/10.1071/wr9940021.
Testo completoAbstract (sommario):
Although Litoria dahlii is one of the most abundant frog species of floodplain habitats in tropical Australia, it is rarely eaten by snakes. Force-feeding trials showed that L. dahlii is highly toxic to snakes: ingestion of even a single large frog was potentially fatal for pythons (Liasis childreni and Liasis fuscus), colubrids (Dendrelaphispunctulatus and Stegonotus cucullatus) and elapids (Acanthophis praelongus and Demansia atra). Only one species, the keelback, Tropidonophis mairii (Colubridae), could consume these frogs without ill effects. Keelbacks were also the only snakes recorded to eat these frogs in the wild. The fact that these abundant tropical frogs are highly toxic to most snakes, and generally not eaten by them, suggests that the anurophagous snakes of the Australian tropics assess amphibian chemical defences before consuming their prey. Thus, these snakes may be better-able to deal with the invasion of cane toads, Bufo marinus, than has been generally supposed.
33
FLANIGAN, JAMES E., PHILIP C. WITHERS e MICHAEL GUPPY. "In Vitro Metabolic Depression of Tissues from the Aestivating Frog Neobatrachus Pelobatoides". Journal of Experimental Biology 161, n. 1 (1 novembre 1991): 273–83. http://dx.doi.org/10.1242/jeb.161.1.273.
Testo completoAbstract (sommario):
The desert frog Neobatrachus pelobatoides reduced its resting metabolism in vivo by 60–70% during 5–7 weeks of aestivation (summer dormancy). The rate ofoxygen consumption (V·OO2) of isolated and intact skeletal muscle, measured in vitro, was 70% lower for aestivating frogs compared with non-aestivating frogs. The cause of the reduced V·OO2 of aestivating frog muscle must lie in the tissue itself rather than being induced by external factors such as oxygen supply or bloodborne metabolites (because these were identical in the in vitro assay conditions), by any short-term effects produced by hormones (as these would have been washed out of the tissues during incubation) or by tissue dehydration (as the tissues from aestivating frogs had rehydrated to non-aestivating levels). The reduced in vitro muscle V·OO2 accounted for 60–77% of the frogs in vivo metabolic depression that accompanied aestivation. Other tissues of the aestivating frog, namely intestine, liver, skin and fat, did not have a reduced in vitro V·OO2. We suggest that metabolic depression is initiated by reduced energy demand in cells and this consequently leads to reduced energy production.
34
Eaton, B. R., W. M. Tonn, C. A. Paszkowski, A. J. Danylchuk e S. M. Boss. "Indirect effects of fish winterkills on amphibian populations in boreal lakes". Canadian Journal of Zoology 83, n. 12 (1 dicembre 2005): 1532–39. http://dx.doi.org/10.1139/z05-151.
Testo completoAbstract (sommario):
We exploited fish winterkills in small, boreal Alberta lakes to determine if anuran amphibians respond to large but natural changes in fish densities. Eight large declines in fish abundance occurred in seven lakes over a 5 year period, while major increases in fish abundance, reflecting recovery after winterkill, were recorded 5 times. Summer pitfall trapping of young-of-the-year (YOY) Wood Frogs (Rana sylvatica LeConte, 1825) and Boreal (Bufo boreas boreas Baird and Girard, 1852) and Canadian (Bufo hemiophrys Cope, 1886) toads indicated that frog abundance responded consistently to such large changes in fish abundance, but especially if fish communities were dominated by small-bodied species (sticklebacks and minnows). As well, changes in YOY Wood Frog and fish abundance were negatively correlated; YOY Wood Frogs were as much as 7.7 times more abundant after winterkills than in non-winterkill years. These increases in metamorphs did not result from an increased immigration of breeding adults to winterkill lakes, suggesting instead that larval survival was greater. Higher abundance of YOY Wood Frogs and toads was associated with smaller body size at metamorphosis. Despite this apparent reduction in individual growth, abundance of juvenile frogs remained significantly elevated 1 year after winterkill. In contrast to Wood Frogs, YOY toads tended to respond positively to recoveries of small-fish populations. Because anuran amphibians can respond to fish winterkill, and because winterkill is a frequent natural disturbance, small fish-bearing lakes can serve as important breeding habitat for amphibians in Alberta's boreal forest.
35
Railsback, Steven F., Bret C. Harvey, Sarah J. Kupferberg, Margaret M. Lang, Scott McBain e Hart H. Welsh. "Modeling potential river management conflicts between frogs and salmonids". Canadian Journal of Fisheries and Aquatic Sciences 73, n. 5 (maggio 2016): 773–84. http://dx.doi.org/10.1139/cjfas-2015-0267.
Testo completoAbstract (sommario):
Management of regulated rivers for yellow-legged frogs (Rana boylii) and salmonids exemplifies potential conflicts among species adapted to different parts of the natural flow and temperature regimes. Yellow-legged frogs oviposit in rivers in spring and depend on declining flows and warming temperatures for egg and tadpole survival and growth, whereas salmonid management can include high spring flows and low-temperature reservoir releases. We built a model of how flow and temperature affect frog breeding success. Its mechanisms include adults selecting oviposition sites to balance risks of egg dewatering by decreasing flow versus scouring by high flow, temperature effects on development, habitat selection by tadpoles, and mortality via dewatering and scouring. In simulations of a regulated river managed primarily for salmonids, below-natural temperatures delayed tadpole metamorphosis into froglets, which can reduce overwinter survival. However, mitigating this impact via higher temperatures was predicted to cause adults to oviposit before spring flow releases for salmonids, which then scoured the egg masses. The relative timing of frog oviposition and high flow releases appears critical in determining conflicts between salmonid and frog management.
36
Portik, Daniel M., Rayna C. Bell, David C. Blackburn, Aaron M. Bauer, Christopher D. Barratt, William R. Branch, Marius Burger et al. "Sexual Dichromatism Drives Diversification within a Major Radiation of African Amphibians". Systematic Biology 68, n. 6 (23 aprile 2019): 859–75. http://dx.doi.org/10.1093/sysbio/syz023.
Testo completoAbstract (sommario):
AbstractTheory predicts that sexually dimorphic traits under strong sexual selection, particularly those involved with intersexual signaling, can accelerate speciation and produce bursts of diversification. Sexual dichromatism (sexual dimorphism in color) is widely used as a proxy for sexual selection and is associated with rapid diversification in several animal groups, yet studies using phylogenetic comparative methods to explicitly test for an association between sexual dichromatism and diversification have produced conflicting results. Sexual dichromatism is rare in frogs, but it is both striking and prevalent in African reed frogs, a major component of the diverse frog radiation termed Afrobatrachia. In contrast to most other vertebrates, reed frogs display female-biased dichromatism in which females undergo color transformation, often resulting in more ornate coloration in females than in males. We produce a robust phylogeny of Afrobatrachia to investigate the evolutionary origins of sexual dichromatism in this radiation and examine whether the presence of dichromatism is associated with increased rates of net diversification. We find that sexual dichromatism evolved once within hyperoliids and was followed by numerous independent reversals to monochromatism. We detect significant diversification rate heterogeneity in Afrobatrachia and find that sexually dichromatic lineages have double the average net diversification rate of monochromatic lineages. By conducting trait simulations on our empirical phylogeny, we demonstrate that our inference of trait-dependent diversification is robust. Although sexual dichromatism in hyperoliid frogs is linked to their rapid diversification and supports macroevolutionary predictions of speciation by sexual selection, the function of dichromatism in reed frogs remains unclear. We propose that reed frogs are a compelling system for studying the roles of natural and sexual selection on the evolution of sexual dichromatism across micro- and macroevolutionary timescales.
37
Bennett, A. M., e D. L. Murray. "Carryover effects of phenotypic plasticity: embryonic environment and larval response to predation risk in Wood Frogs (Lithobates sylvaticus) and Northern Leopard Frogs (Lithobates pipiens)". Canadian Journal of Zoology 93, n. 11 (novembre 2015): 867–77. http://dx.doi.org/10.1139/cjz-2015-0129.
Testo completoAbstract (sommario):
Limitations of phenotypic plasticity affect the success of individuals and populations in changing environments. We assessed the plasticity-history limitation on predator-induced defenses in anurans (Wood Frogs, Lithobates sylvaticus (LeConte, 1825), and Northern Leopard Frogs, Lithobates pipiens (Schreber, 1782)), predicting that plastic responses to predation risk by dragonfly larvae (family Aeshnidae) in the embryonic environment would limit the defensive response to predators in the larval environment. Predator-conditioned Wood Frog embryos increased relative tail depth in response to those same cues as larvae, whereas predator-naive tadpoles did not. However, no carryover effect was noted in the behavioural response of Wood Frog tadpoles to predation risk. Predator-naive Northern Leopard Frog tadpoles increased relative tail depth in response to predation risk in the larval environment. Predator-conditioned Northern Leopard Frog embryos hatched with, and maintained, a marginal increase in tail depth as larvae in the absence of predation risk. Predator-conditioned Northern Leopard Frog embryos exposed to predation risk as larvae showed no morphological response. While we find no strong support for the plasticity-history limitation per se, carryover effects across embryonic and larval life-history stages were noted in both Wood Frog and Northern Leopard Frog, suggesting that predation risk early in ontogeny can influence the outcome of future interactions with predators.
38
Mason, Matthew J., e Peter M. Narins. "Vibrometric studies of the middle ear of the bullfrog Rana catesbeiana I. The extrastapes". Journal of Experimental Biology 205, n. 20 (15 ottobre 2002): 3153–65. http://dx.doi.org/10.1242/jeb.205.20.3153.
Testo completoAbstract (sommario):
SUMMARY Laser vibrometry was used to measure the vibration velocity at different points on the ossicular apparatus of the bullfrog Rana catesbeiana in response to free-field sound. The ascending process of the extrastapes,neglected in most accounts of frog middle ear mechanics, supports a rocking motion of the extrastapes and is critical to the normal function of the ossicular apparatus. The articulation between extrastapes and the bony stapes shaft acts as a hinge, although movement at this hinge is usually small. The ratio of tympanic membrane to footplate vibration velocity is significantly greater in male frogs than in female frogs. Differences in this ratio between male and female frogs are probably mainly due to flexion between the extrastapes and stapes rather than to differences in the coupling between tympanic membrane and extrastapes. It is argued that flexibility in the ossicular system represents a protective mechanism in frogs, and functional analogies are drawn between the stapes/extrastapes system of frogs and the tri-ossicular system of mammals.
39
Nishiumi, Nozomi, e Akira Mori. "A game of patience between predator and prey: waiting for opponent’s action determines successful capture or escape". Canadian Journal of Zoology 98, n. 6 (giugno 2020): 351–57. http://dx.doi.org/10.1139/cjz-2019-0164.
Testo completoAbstract (sommario):
When predator and prey animals face each other, preemptive actions by both sides are considered to mediate successful capture or escape. However, in spite of the general presumption, some animals, such as predatory snakes and their frog prey, occasionally remain motionless or move slowly for a while before striking or escaping, respectively. To clarify the possible advantages of this behaviour, we examined interactions between Japanese Four-lined Ratsnakes (Elaphe quadrivirgata (H. Boie, 1826)) and Black-spotted Pond Frogs (Pelophylax nigromaculatus (Hallowell, 1861)), focusing especially on kinematic features of strike behaviour of snakes and flight behaviour of frogs in close quarters. Staged encounter experiments and field observations revealed that counteractions against an opponent’s preemptive actions are effective for both snakes and frogs until a certain distance because they are hardly able to change their trajectories once they initiate strike or escape behaviours. Snakes and frogs also appropriately switched their behaviour from waiting for the opponent’s action to taking preemptive action at this threshold distance. These results suggested the occurrence of a game of patience between snakes and frogs in which they wait for the opponent’s action to achieve effective countermeasures. Our study provides new insights for predicting optimal decision-making by predators and prey and will contribute to a better understanding of their strategies.
40
YUSNAVIEL GARCÍA-PADRÓN, L. "Anomalous colour in a Cuban cave-dwelling frog: First record of piebaldism in Eleutherodactylus zeus (Anura: Eleutherodactylidae)". Herpetological Bulletin, n. 147, Spring 2019 (1 aprile 2019): 1–3. http://dx.doi.org/10.33256/hb147.13.
Testo completoAbstract (sommario):
Pigmentation anomalies may occur due to genetic or environmental factors and can affect restricted parts of the body or the entire surface. Eleutherodactylus zeus is frog endemic to western Cuba where it is adapted to life in caves, rock crevices, and other sheltered sites in limestone landscapes associated with forest habitats. We observed 43 frogs in Santo Tomás cave, in Viñales National Park, of which 26 % showed depigmented blotches, typical of piebaldism, along their bodies. No unusual behaviour was detected in any of these frogs. This is the first reported case of piebaldism in frogs of the West Indies and consequently of Cuba. Records of piebaldism in amphibians are very scarce in the literature, not necessarily as a consequence of its rarity in nature but possibly due to inconsistencies in the classification of pigmentation abnormalities.
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Allmon, Warren D. "A plot study of forest floor litter frogs, Central Amazon, Brazil". Journal of Tropical Ecology 7, n. 4 (novembre 1991): 503–22. http://dx.doi.org/10.1017/s0266467400005885.
Testo completoAbstract (sommario):
ABSTRACTAbundance and distribution of frogs inhabiting the litter layer of an area of primary lowland rain forest in Central Amazonia were studied over a period of 15 months by sampling 498 plots each 5m × 5m. The litter frog fauna of the area consists of 23 species, but only 12 of these were encountered in the plots, and 84% of the frogs encountered belonged to only six species. Total abundance and diversity within the plot data are strongly seasonal and peak in the late wet season. Both are positively correlated with litter volume and moisture. Most of this variation is due to seasonality of reproduction, as indicated by patterns of occurrence of juveniles of the most abundant species.These results indicate that the plot sampling method docs not sample the entire fauna adequately. Since this technique has been used to study other tropical forest litter herpetofaunas, however, comparison with other studies may be useful. Species diversity of litter frogs appears to be approximately the same in lowland primary forest sites studied, averaging around 20 ‘regular’ species. Abundances, however, vary widely. Central American communities contain 14–15 frogs (100m)-2, African 9–10, South American 4–6, and South-east Asian 1–2. These differences may be due to differential nutrient availability in forests of different ages and/or on different soils.
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Nunes, Ana L., Germán Orizaola, Anssi Laurila e Rui Rebelo. "Rapid Evolution of Antipredator Defenses in Frogs". Bulletin of the Ecological Society of America 95, n. 4 (ottobre 2014): 451–56. http://dx.doi.org/10.1890/0012-9623-95.4.451.
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MENSI, PAOLA, ALDO LATTES, BIANCAMARIA MACARIO, SEBASTIANO SALVIDIO, CRISTINA GIACOMA e EMILIO BALLETTO. "Taxonomy and evolution of European brown frogs". Zoological Journal of the Linnean Society 104, n. 4 (aprile 1992): 293–311. http://dx.doi.org/10.1111/j.1096-3642.1992.tb00925.x.
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Woodhams, Douglas C., Jon P. Costanzo, Jonathan D. Kelty e Richard E. Lee, Jr. "Cold hardiness in two helminth parasites of the freeze-tolerant wood frog, Rana sylvatica". Canadian Journal of Zoology 78, n. 6 (1 giugno 2000): 1085–91. http://dx.doi.org/10.1139/z00-034.
Testo completoAbstract (sommario):
Wood frogs, Rana sylvatica, tolerate the freezing of their body tissues as an overwintering adaptation. Various parasites infect wood frogs of northern populations, but nothing is known about their strategies for surviving within a frozen host. We examined winter-conditioned wood frogs that were experimentally exposed to 0°C (nonfrozen) or 4°C (frozen) to determine whether endoparasites survive the freezing of their host. We found no differences in the prevalence or intensity of adult lungworms Rhabdias ranae (Nematoda) or of larvae of an unidentified species of digenetic trematode between these groups. Live individuals of both species were observed in hosts that recovered from experimental freezing at 4°C. Within the host, R. ranae also tolerated exposure to 5°C, a temperature near the lower limit of survival of the wood frog. Cryostage experiments showed that, like its host, R. ranae was highly susceptible to inoculative freezing and tolerant of the freezing of its tissues. Rhabdias ranae frozen in vitro in the presence or absence of 250 mM glucose, the cryoprotectant used by wood frogs, recovered from a 10-h exposure to 4°C. The mechanism of cold tolerance used by larval trematodes was not investigated; however, we hypothesize that freeze avoidance by supercooling may be important in this species. Freeze-tolerant anurans, such as the wood frog, are useful subjects in the study of coevolution of thermal tolerance in parasites and their host.
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Mutnale, Milind C., Gundlapally S. Reddy e Karthikeyan Vasudevan. "Bacterial Community in the Skin Microbiome of Frogs in a Coldspot of Chytridiomycosis Infection". Microbial Ecology 82, n. 2 (13 gennaio 2021): 554–58. http://dx.doi.org/10.1007/s00248-020-01669-5.
Testo completoAbstract (sommario):
AbstractChytridiomycosis is a fungal disease caused by the pathogens, Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal), which has caused declines in amphibian populations worldwide. Asia is considered as a coldspot of infection, since adult frogs are less susceptible to Bd-induced mortality or morbidity. Using the next-generation sequencing approach, we assessed the cutaneous bacterial community composition and presence of anti-Bd bacteria in six frog species from India using DNA isolated from skin swabs. All the six frog species sampled were tested using nested PCR and found Bd negative. We found a total of 551 OTUs on frog skin, of which the bacterial phyla such as Proteobacteria (56.15% average relative abundance) was dominated followed by Actinobacteria (21.98% average relative abundance) and Firmicutes (13.7% average relative abundance). The contribution of Proteobacteria in the anti-Bd community was highest and represented by 175 OTUs. Overall, the anti-Bd bacterial community dominated (51.7% anti-Bd OTUs) the skin microbiome of the frogs. The study highlights the putative role of frog skin microbiome in affording resistance to Bd infections in coldspots of infection.
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Blackburn, David C., Rachel M. Keeffe, María C. Vallejo-Pareja e Jorge Vélez-Juarbe. "The earliest record of Caribbean frogs: a fossil coquí from Puerto Rico". Biology Letters 16, n. 4 (aprile 2020): 20190947. http://dx.doi.org/10.1098/rsbl.2019.0947.
Testo completoAbstract (sommario):
The nearly 200 species of direct-developing frogs in the genus Eleutherodactylus (the Caribbean landfrogs, which include the coquís) comprise an important lineage for understanding the evolution and historical biogeography of the Caribbean. Time-calibrated molecular phylogenies provide indirect evidence for the processes that shaped the modern anuran fauna, but there is little direct evidence from the fossil record of Caribbean frogs about their distributions in the past. We report a distal humerus of a frog from the Oligocene (approx. 29 Ma) of Puerto Rico that represents the earliest known fossil frog from any Caribbean island. Based on its prominent rounded distal humeral head, distally projecting entepicondyle, and reduced ectepicondyle, we refer it to the genus Eleutherodactylus . This fossil provides additional support for an early arrival of some groups of terrestrial vertebrates to the Greater Antilles and corroborates previous estimates based on molecular phylogenies suggesting that this diverse Caribbean lineage was present in the islands by the mid-Cenozoic.
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Borkent, Art, e Peter Belton. "Attraction of female Uranotaenia lowii (Diptera: Culicidae) to frog calls in Costa Rica". Canadian Entomologist 138, n. 1 (febbraio 2006): 91–94. http://dx.doi.org/10.4039/n04-113.
Testo completoAbstract (sommario):
AbstractDuring a survey of frog-biting corethrellid midges in Costa Rica, we collected 79 female Uranotaenia lowii Theobald, mosquitoes known to bite frogs, from seven lowland localities using the recorded calls of a frog. The calls of male barking tree frogs, Hyla gratiosa LeConte, were repeated about once per second, lasted about 0.15 s, and had a fundamental frequency near 450 Hz. We suggest that this frequency is within the range of acoustic sensitivity of the female mosquito antennae. Males of several families of Nematocera use sound to detect flying females of their own species, but we believe ours is the first observation of female mosquitoes being attracted by the sound of a host.
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Mori, Akira. "Is headfirst ingestion essential in gape-limited predators? Prey-handling behavior of the anurophagous snake Rhabdophis tigrinus (Colubridae)". Canadian Journal of Zoology 84, n. 7 (1 luglio 2006): 954–63. http://dx.doi.org/10.1139/z06-073.
Testo completoAbstract (sommario):
Headfirst ingestion of prey is a common adaptive behavioral trait in gape-limited predators that swallow large prey whole. To ascertain this tendency during anurophagy, prey handling and direction of prey ingestion were investigated in Rhabdophis tigrinus (Boie, 1826), a snake that feeds mainly on anurans. Examinations of stomach contents of wild R. tigrinus revealed that this snake does not show a tendency for headfirst ingestion of large prey, unlike most other snake species. In the laboratory, direction of ingestion depended largely on initial bite position, and when R. tigrinus swallowed a frog rump-first, the snake grasped both hind limbs of the frog and aligned them side by side so that both were swallowed together simultaneously from their tips. A simple model test suggested that physical resistance in the buccal cavity incurred during transportation of frogs may not differ between headfirst and hind-first ingestion if the hind limbs of frogs are aligned and swallowed simultaneously. Laboratory experiments also demonstrated that ingestively naive hatchlings of R. tigrinus are able to perform the unique manipulation required to swallow frogs hind-first. It is suggested that this unique ingestion mode is an adaptation for anurophagy, and several possible functional advantages are discussed.
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CANNATELLA, DAVID C., e LINDA TRUEB. "Evolution of pipoid frogs: intergeneric relationships of the aquatic frog family Pipidae (Anura)". Zoological Journal of the Linnean Society 94, n. 1 (settembre 1988): 1–38. http://dx.doi.org/10.1111/j.1096-3642.1988.tb00880.x.
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Emerson, Sharon B., Carol N. Rowsemitt e David L. Hess. "Androgen levels in a Bornean voiceless frog, Rana blythi". Canadian Journal of Zoology 71, n. 1 (1 gennaio 1993): 196–203. http://dx.doi.org/10.1139/z93-027.
Testo completoAbstract (sommario):
Male Rana blythi and males of three other species of voiceless frogs from Bornean rain forests lack the suite of secondary sex characteristics typical of most anurans: nuptial pads, vocal sacs, enlarged forearm flexors, and male advertisement calls. At the same time, basal species in the voiceless frog lineage exhibit an extreme type of male parental care: the males carry the tadpoles on their backs. This unusual form of male parental care evolves at the same point in the phylogenetic history of the group as the loss of the secondary sex characteristics. This suggests that these voiceless frogs may have lowered androgen levels. Hormone assays from blood samples of R. blythi show that plasma levels of testosterone, androstenedione, and 5α-dihydrotestosterone are considerably lower in wild-caught R. blythi than those reported for other frog species when similar sample collection methods were employed.