repetitive dna and feulgen hydrolysis kinetics in three species of bufo.two north american species of the genus bufo (bufo cognatus and bufo boreas, 2n = 22) and one african species (bufo regularis, 2n = 20) were analyzed with respect to their repetitive dna fractions and the behaviour of their chromatin to the acid hydrolysis at different times. the mean melting point of the total isolated dna decreased from 89 degrees c to 87 degrees c with a genome size increase from 4.4 to 7.5 pg. the differences in genome size can only partly be explained on the basis of repeti ...197993962
prolactin, calcitonin, and blood calcium in the toads bufo boreas and bufo marinus. 19715001863
comparative effects of mammalian prolactin and growth hormone on growth in the toads bufo boreas and bufo marinus. 19695406003
effects of meal size, meal type, body temperature, and body size on the specific dynamic action of the marine toad, bufo marinus.specific dynamic action (sda), the accumulated energy expended on all physiological processes associated with meal digestion, is strongly influenced by features of both the meal and the organism. we assessed the effects of meal size, meal type, body temperature, and body size on the postprandial metabolic response and calculated sda of the marine toad, bufo marinus. peak postprandial rates of o(2) consumption (.v(o2)) and co(2) production (.v(co2)) and sda increased with meal size (5%-20% of bod ...200212601612
evaluation of tadpole mouthpart depigmentation as a diagnostic test for infection by batrachochytrium dendrobatidis for four california anurans.the objective of this study was to evaluate the utility of gross morphologic examination of larval mouthpart defects as a diagnostic screening test to detect batrachochytrium dendrobatidis infection in four california, usa, anuran species. we examined mouthparts of 2,034 tadpoles of bufo boreas, pseudacris regilla, and rana catesbeiana collected in 2003 and 2004 and bufo canorus collected in 2004. data were recorded for three morphologic features: upper toothrows, lower toothrows, and combined j ...200717984265
inhibition of batrachochytrium dendrobatidis caused by bacteria isolated from the skin of boreal toads, anaxyrus (bufo) boreas boreas, from grand teton national park, wyoming, usa.the chytrid fungus batrachochytrium dendrobatidis is a significant cause of the worldwide decline in amphibian populations; however, various amphibian species are capable of coexisting with b. dendrobatidis. among them are boreal toads (anaxyrus (bufo) boreas boreas) located in grand teton national park (gtnp) in wyoming, usa. the purpose of this study was to identify cultivable bacterial isolates from the skin microbiota of boreal toads from gtnp and determine if they were capable of inhibiting ...201424826077
inhibitory bacteria reduce fungi on early life stages of endangered colorado boreal toads (anaxyrus boreas).increasingly, host-associated microbiota are recognized to mediate pathogen establishment, providing new ecological perspectives on health and disease. amphibian skin-associated microbiota interact with the fungal pathogen, batrachochytrium dendrobatidis (bd), but little is known about microbial turnover during host development and associations with host immune function. we surveyed skin microbiota of colorado's endangered boreal toads (anaxyrus boreas), sampling 181 toads across four life stage ...201626565725
a model to inform management actions as a response to chytridiomycosis-associated decline.decision-analytic models provide forecasts of how systems of interest will respond to management. these models can be parameterized using empirical data, but sometimes require information elicited from experts. when evaluating the effects of disease in species translocation programs, expert judgment is likely to play a role because complete empirical information will rarely be available. we illustrate development of a decision-analytic model built to inform decision-making regarding translocatio ...201727056609
citizen scientists monitor a deadly fungus threatening amphibian communities in northern coastal california, usa.ecoclub youth and supervising family members conducted citizen science to assess regional prevalence and distribution of batrachochytrium dendrobatidis (bd) among amphibians at humboldt bay national wildlife refuge (refuge) and redwood national and state parks (parks), humboldt county, california, us, may 2013 through december 2014. using quantitative real-time pcr, 26 (17%) of 155 samples were positive for bd. positive samples occurred in four frog and toad species: foothill yellow-legged frog ...201627195681
probiotic treatment restores protection against lethal fungal infection lost during amphibian microbiomes perform many beneficial functions including resisting pathogens and training the immune system. here, we show that amphibians developing in captivity lose substantial skin bacterial diversity, primarily due to reduced ongoing input from environmental sources. we combined studies of wild and captive amphibians with a database of over 1 000 strains that allows us to examine antifungal function of the skin microbiome. we tracked skin bacterial communities of 62 endangere ...201627655769
comparative study of host response to chytridiomycosis in a susceptible and a resistant toad the past century, recently emerged infectious diseases have become major drivers of species decline and extinction. the fungal disease chytridiomycosis has devastated many amphibian populations and exacerbated the amphibian conservation crisis. biologists are beginning to understand what host traits contribute to disease susceptibility, but more work is needed to determine why some species succumb to chytridiomycosis while others do not. we conducted an integrative laboratory experiment to ex ...201627696594
stability and permanence in gender- and stage-structured models for the boreal toad.the boreal toad bufo boreas boreas, once common in the western usa, is listed as an endangered species in colorado and new mexico, and protected in wyoming. populations have dramatically declined due to the presence of the fungal pathogen batrachochytrium dendrobatidis (bd). a gender- and stage-structured model for the boreal toad is formulated which depends on its life cycle and breeding strategies. in addition, an epizootic model for the spread of bd is formulated. analysis of these models pro ...201122877227
complete genome sequence of a bohle iridovirus isolate from ornate burrowing frogs (limnodynastes ornatus) in australia.bohle iridovirus (biv) is a species within the genus ranavirus, family iridoviridae, first isolated from the ornate burrowing frog limnodynastes ornatus in australia. the biv genome confirms it is closely related to isolates from boreal toad anaxyrus boreas and leaf-tailed gecko uroplatus fimbriatus within the united states and germany, respectively.201627540051
isolation of a bohle-like iridovirus from boreal toads housed within a cosmopolitan aquarium collection.a captive 'survival assurance' population of 56 endangered boreal toads anaxyrus boreas boreas, housed within a cosmopolitan collection of amphibians originating from southeast asia and other locations, experienced high mortality (91%) in april to july 2010. histological examination demonstrated lesions consistent with ranaviral disease, including multicentric necrosis of skin, kidney, liver, spleen, and hematopoietic tissue, vasculitis, and myriad basophilic intracytoplasmic inclusion bodies. i ...201425266901
temperature, hydric environment, and prior pathogen exposure alter the experimental severity of chytridiomycosis in boreal toads.prevalence of the pathogen batrachochytrium dendrobatidis (bd), implicated in amphibian population declines worldwide, is associated with habitat moisture and temperature, but few studies have varied these factors and measured the response to infection in amphibian hosts. we evaluated how varying humidity, contact with water, and temperature affected the manifestation of chytridiomycosis in boreal toads anaxyrus (bufo) boreas boreas and how prior exposure to bd affects the likelihood of survival ...201121797033
effects of an infectious fungus, batrachochytrium dendrobatidis, on amphibian predator-prey interactions.the effects of parasites and pathogens on host behaviors may be particularly important in predator-prey contexts, since few animal behaviors are more crucial for ensuring immediate survival than the avoidance of lethal predators in nature. we examined the effects of an emerging fungal pathogen of amphibians, batrachochytrium dendrobatidis, on anti-predator behaviors of tadpoles of four frog species. we also investigated whether amphibian predators consumed infected prey, and whether b. dendrobat ...201121311771
the toxicity of glyphosate alone and glyphosate-surfactant mixtures to western toad (anaxyrus boreas) tadpoles.pesticide choice based on toxicity to nontarget wildlife is reliant on available toxicity data. despite a number of recent studies examining the effects of glyphosate on amphibians, very few have aimed to understand the toxicological effects of glyphosate in combination with surfactants as it is commonly applied in the field. land managers interested in making pesticide choices based on minimizing impacts to nontarget wildlife are hindered by a lack of published toxicity data. short-term acute t ...201526084619
amphibian chytrid fungus and ranaviruses in the northwest territories, canada.pathogens can cause serious declines in host species, and knowing where pathogens associated with host declines occur facilitates understanding host-pathogen ecology. suspected drivers of global amphibian declines include infectious diseases, with 2 pathogens in particular, batrachochytrium dendrobatidis (bd) and ranaviruses, causing concern. we explored the host range and geographic distribution of bd and ranaviruses in the taiga plains ecoregion of the northwest territories, canada, in 2007 an ...201021268986
effects of batrachochytrium dendrobatidis infection on ion concentrations in the boreal toad anaxyrus (bufo) boreas boreas.batrachochytrium dendrobatidis causes mortality in various amphibian species including the boreal toad anaxyrus (bufo) boreas boreas. the purpose of this study was to determine the physiological effects of this pathogen on experimentally infected boreal toads. plasma osmolality, sodium, and potassium concentrations were analyzed to evaluate the differences between diseased and non-exposed animals. infected animals with clinical signs of chytridiomycosis had significantly lower plasma osmolality, ...201020853738
effects of amphibian chytrid fungus on individual survival probability in wild boreal toads.chytridiomycosis is linked to the worldwide decline of amphibians, yet little is known about the demographic effects of the disease. we collected capture-recapture data on three populations of boreal toads (bufo boreas [bufo = anaxyrus]) in the rocky mountains (u.s.a.). two of the populations were infected with chytridiomycosis and one was not. we examined the effect of the presence of amphibian chytrid fungus (batrachochytrium dendrobatidis [bd]; the agent of chytridiomycosis) on survival proba ...201020412086
effects of age, weight, hormones, and hibernation on breeding success in boreal toads (bufo boreas boreas).the goals of this study were to test the effects of exogenous hormones and hibernation on breeding behavior and gamete release by boreal toads (bufo boreas boreas). each year, a subset of 77 toads was hibernated and then paired with hibernated or nonhibernated mates and treated with luteinizing hormone releasing hormone analogue (lhrha), human chorionic gonadotropin (hcg), or left untreated. amplexus and egg and sperm production were recorded. at 1 yr of age, only 19% of pairs exhibited amplexus ...201020004010
immune defenses of xenopus laevis against batrachochytrium dendrobatidis.amphibian populations are declining at an unprecedented rate worldwide. a number of declines have been linked to a pathogenic skin fungus, batrachochytrium dendrobatidis. although amphibians have robust immune defenses, many species seem to be very susceptible to infection by this fungus and to development of the lethal disease called chytridiomycosis. one species that is relatively resistant to b. dendrobatidis is xenopus laevis. because x. laevis has been used as a model for studies of immunit ...200919482684
distribution and pathogenicity of batrachochytrium dendrobatidis in boreal toads from the grand teton area of western wyoming.the pathogen batrachochytrium dendrobatidis (bd), which causes the skin disease chytridiomycosis, has been linked to amphibian population declines and extinctions worldwide. bd has been implicated in recent declines of boreal toads, bufo boreas boreas, in colorado but populations of boreal toads in western wyoming have high prevalence of bd without suffering catastrophic mortality. in a field and laboratory study, we investigated the prevalence of bd in boreal toads from the grand teton ecosyste ...200919418097
survival of three species of anuran metamorphs exposed to uv-b radiation and the pathogenic fungus batrachochytrium dendrobatidis.when exploring the possible factors contributing to population declines, it is necessary to consider multiple, interacting environmental stressors. here, we investigate the impact of 2 factors, ultraviolet radiation and disease, on the survival of anuran amphibians. exposure to ultraviolet-b (uv-b) radiation increases mortality and results in various sub-lethal effects for many amphibian species. infectious diseases can also negatively impact amphibian populations. in this study, we exposed meta ...200617140139
effects of the landscape on boreal toad gene flow: does the pattern-process relationship hold true across distinct landscapes at the northern range margin?understanding the impact of natural and anthropogenic landscape features on population connectivity is a major goal in evolutionary ecology and conservation. discovery of dispersal barriers is important for predicting population responses to landscape and environmental changes, particularly for populations at geographic range margins. we used a landscape genetics approach to quantify the effects of landscape features on gene flow and connectivity of boreal toad (bufo boreas) populations from two ...201122035421
predicted disease susceptibility in a panamanian amphibian assemblage based on skin peptide defenses.chytridiomycosis is an emerging infectious disease of amphibians caused by a chytrid fungus, batrachochytrium dendrobatidis. this panzootic does not equally affect all amphibian species within an assemblage; some populations decline, others persist. little is known about the factors that affect disease resistance. differences in behavior, life history, biogeography, or immune function may impact survival. we found that an innate immune defense, antimicrobial skin peptides, varied significantly a ...200616870844
immunochemical identification of thyrotropes and gonadotropes in the pars distalis and pars tuberalis of the toad (bufo boreas) with reference to ontogenic changes.morphologically distinct secretory cells in the pituitary pars distalis and pars tuberalis of larval and adult toads (bufo boreas) immunoreactive cells in the pars distalis. thyrotropin immunoactivity appears in pars tuberalis and pars distalis before gonadotropin immunoreactivity during early development. antisera which distinguish gonadotropes (stained with human and sea turtle lh beta) and thyrotropes (stained with human tsh beta) as separate cell types in the pars distalis of the adult toad ...19989653025
developmental responses of amphibians to solar and artificial uvb sources: a comparative study.many amphibian species, in widely scattered locations, currently show population declines and/or reductions in range, but other amphibian species show no such declines. there is no known single cause for these declines. differential sensitivity to uvb radiation among species might be one contributing factor. we have focused on amphibian eggs, potentially the most uvb-sensitive stage, and compared their resistance to uvb components of sunlight with their levels of photolyase, typically the most i ...19968806225
interdependence of corticosterone and thyroid hormones in larval toads (bufo boreas). i. thyroid hormone-dependent and independent effects of corticosterone on growth and a previous study (hayes et al. [1993] j. exp. zool., 266:206-215), we demonstrated that exogenous corticosterone (b) inhibited growth, and had varied effects on development and metamorphosis in the toad (bufo boreas). the current study determined the relation between the actions of b and thyroid hormones on body growth (length and weight), tail growth and reduction (length and height), rear leg growth and differentiation, and foreleg emergence (fle). thiourea (thio; a goitrogen) and metyrapon ...19957884391
factors influencing testosterone metabolism by anuran larvae.the effects of experimental conditions--steroid concentration, temperature, treatment duration, tadpole density, and delivery mode--on testosterone (t) metabolic rates were examined in larval anurans. t uptake into tadpoles was measured by scintillation counting of [3h]t and metabolism of t was studied by thin layer chromatography in two anuran species, the african clawed frog (xenopus laevis) and the western toad (bufo boreas). t was extensively metabolized by both species, but the effects of e ...19957884385
interdependence of corticosterone and thyroid hormones in toad larvae (bufo boreas). ii. regulation of corticosterone and thyroid hormones.typically, the role of corticosterone(b) in metamorphosis is considered secondary to that of thyroid hormone, with b having only enhancing effects. in the current study, we demonstrate that the relationship between the thyroid hormones and b is much more complex and that thyroxine (t4) may depend on b for some of its functions. tadpoles of the western toad (bufo boreas) were treated with various combinations of corticosterone (b), thyroxine (t4), triiodothyronine (t3), a goitrogen (thiourea; thi ...19957884384
trypanosome transmitted by phlebotomus: first report from the americas.transmission studies carried out in the laboratory incriminated phlebotomus vexator occidentis as a vector of a species of trypanosome that infects bufo boreas halophilus. toads free of parasites contracted the trypanosome after eating infected flies and after intraperitoneal inoculation of flagellates cultured from the hindgut of flies that had fed on infected toads. discovery of this vectorhost-parasite system in the americas, and the localization of promastigote flagellates (leptomonads) in t ...19685671479
estimation of temporary emigration in male toads.male boreal toads (bufo boreas) are thought to return to the breeding site every year but, if absent in a particular year, will be more likely to return the following year. using pollock's robust design we estimated temporary emigration (the probability a male toad is absent from a breeding site in a given year) at three locations in colorado, usa: two in rocky mountain national park and one in chaffee county. we present data that suggest that not all male toads return to the breeding site every ...200616676548
effects of ultraviolet radiation on toad early life stages.exposure to harmful levels of ultraviolet-b radiation (uvb), a component of solar radiation, has been suggested as a potential cause of amphibian declines.200312846377
effects of pesticide mixtures on host-pathogen dynamics of the amphibian chytrid fungus.anthropogenic and natural stressors often interact to affect organisms. amphibian populations are undergoing unprecedented declines and extinctions with pesticides and emerging infectious diseases implicated as causal factors. although these factors often co-occur, their effects on amphibians are usually examined in isolation. we hypothesized that exposure of larval and metamorphic amphibians to ecologically relevant concentrations of pesticide mixtures would increase their post-metamorphic susc ...201526181492
host species composition influences infection severity among amphibians in the absence of spillover transmission.wildlife epidemiological outcomes can depend strongly on the composition of an ecological community, particularly when multiple host species are affected by the same pathogen. however, the relationship between host species richness and disease risk can vary with community context and with the degree of spillover transmission that occurs among co-occurring host species. we examined the degree to which host species composition influences infection by batrachochytrium dendrobatidis (bd), a widespre ...201525897383
stress and chytridiomycosis: exogenous exposure to corticosterone does not alter amphibian susceptibility to a fungal pathogen.recent emergence and spread of the amphibian fungal pathogen, batrachochytrium dendrobatidis (bd) has been attributed to a number of factors, including environmental stressors that increase host susceptibility to bd. physiological stress can increase circulating levels of the hormone, corticosterone, which can alter a host's physiology and affect its susceptibility to pathogens. we experimentally elevated whole-body levels of corticosterone in both larval and post-metamorphic amphibians, and sub ...201424610865
experimental evidence for american bullfrog (lithobates catesbeianus) susceptibility to chytrid fungus (batrachochytrium dendrobatidis).the emerging fungal pathogen, batrachochytrium dendrobatidis (bd), has been associated with global amphibian population declines and extinctions. american bullfrogs (lithobates catesbeianus) are widely reported to be a tolerant host and a carrier of bd that spreads the pathogen to less tolerant hosts. here, we examined whether bullfrogs raised from eggs to metamorphosis in outdoor mesocosms were susceptible to bd. we experimentally exposed metamorphic juveniles to bd in the laboratory and compar ...201323539129
juvenile western toads, bufo boreas, avoid chemical cues of snakes fed juvenile, but not larval, conspecifics.previous investigations have demonstrated the importance of predator diet in chemically mediated antipredator behaviour. however, there are few data on responses to life-stage-specific predator diets, which could be important for animals like amphibians that undergo metamorphosis and must respond to different suites of predators at different life-history stages. in laboratory choice tests, we investigated the chemically mediated avoidance response of juvenile western toads, bufo boreas, to four ...200010792942
host identity matters in the amphibian-batrachochytrium dendrobatidis system: fine-scale patterns of variation in responses to a multi-host pathogen.species composition within ecological assemblages can drive disease dynamics including pathogen invasion, spread, and persistence. in multi-host pathogen systems, interspecific variation in responses to infection creates important context dependency when predicting the outcome of disease. here, we examine the responses of three sympatric host species to a single fungal pathogen, batrachochytrium dendrobatidis, which is associated with worldwide amphibian population declines and extinctions. usin ...201323382904
effect of simultaneous amphibian exposure to pesticides and an emerging fungal pathogen, batrachochytrium dendrobatidis.amphibian declines have been linked to numerous factors, including pesticide use and the fungal pathogen batrachochytrium dendrobatidis (bd). moreover, research has suggested a link between amphibian sensitivity to bd and pesticide exposure. we simultaneously exposed postmetamorphic american toads (anaxyrus americanus), western toads (a. boreas), spring peepers (pseudacris crucifer), pacific treefrogs (p. regilla), leopard frogs (lithobates pipiens), and cascades frogs (rana cascadae) to a facto ...201728001054
a light and electron microscopic study of trypanosoma fallisi n. sp. in toads (bufo americanus) from algonquin park, ontario.trypanosoma fallisi n. sp. is described from bufo americanus in ontario. the parasite was observed in 65 of 94 toads examined. the trypanosomes were pleomorphic with respect to the age of infections, being longer and broader in early infections (during spring and summer) and shorter and more slender during late summer and autumn. they ranged in size from 38-76 microns in body length and 3-8 microns in width, with a free flagellum 6-30 microns long. epizootiological and experimental evidence sugg ...20062359048
ranavirus could facilitate local extinction of rare amphibian species.there is growing evidence that pathogens play a role in population declines and species extinctions. for small populations, disease-induced extinction may be especially probable. we estimated the susceptibility of two amphibian species of conservation concern (the dusky gopher frog [lithobates sevosus] and boreal toad [anaxyrus boreas boreas]) to an emerging pathogen (ranavirus) using laboratory challenge experiments, and combined these data with published demographic parameter estimates to simu ...201627344151
a hormone priming regimen and hibernation affect oviposition in the boreal toad (anaxyrus boreas boreas).declines of the southern rocky mountain population of boreal toad (anaxyrus boreas boreas) have led to the establishment of a captive assurance population and reintroduction program, in an attempt to preserve and propagate this geographically isolated population. one of the unique adaptations of this species is its ability to survive in cold environments by undergoing long periods of hibernation. in captivity, hibernation can be avoided altogether, decreasing morbidity caused by compromised immu ...201526025241
the phylogenetic utility of cytochrome b: lessons from bufonid frogs.the mitochondrial cytochrome b gene is widely used in systematic studies to resolve divergences of many different ages. to investigate phylogenetic relationships among frogs of the large family bufonidae, and to explore the utility of cytochrome b for this purpose, approximately one-third of the gene was sequenced from representatives of this group. samples were chosen to represent a range of divergence levels within bufonidae: (1) deep (= old), among species from around the world; (2) middle, a ...19938136925
temporal population genetic instability in range-edge western toads, anaxyrus this article, we address the temporal stability of population genetic structure in a range-edge population that is undergoing continual, short-distance colonization events. we sampled western toad, anaxyrus boreas, breeding populations over 2 seasons near their northern range limit in southeast alaska. we sampled 20 ponds each during the summers of 2008 and 2009, with 14 ponds sampled in both summers. we found considerable turnover in the population genetic relationships among ponds in those ...201425433082
taurine in toad brain and blood under different conditions of osmolality: an immunohistochemical study.the concentrations of taurine in blood and brain regions of the toad bufo boreas have been measured. most of these values are considerably lower than those found in mammals. using an antibody prepared against conjugated taurine, the distribution of taurine in three brain regions of the toad has been visualized. the possible osmoregulatory functions of taurine have been investigated by making toads hyper- or hypo-osmotic in vivo. induction of hypoosmolality is accompanied by a massive taurine tid ...19938474567
factors mediating co-occurrence of an economically valuable introduced fish and its native frog prey.habitat characteristics mediate predator-prey coexistence in many ecological systems but are seldom considered in species introductions. when economically important introduced predators are stocked despite known negative impacts on native species, understanding the role of refuges, landscape configurations, and community interactions can inform habitat management plans. we measured these factors in basins with introduced trout (salmonidae) and the cascades frog (rana cascadae) to determine, whic ...201424372671
the amphibian skin-associated microbiome across species, space and life history bacteria of amphibians are increasingly recognized for their role in defence against pathogens, yet we have little understanding of their basic ecology. here, we use high-throughput 16s rrna gene sequencing to examine the host and environmental influences on the skin microbiota of the cohabiting amphibian species anaxyrus boreas, pseudacris regilla, taricha torosa and lithobates catesbeianus from the central valley in california. we also studied populations of rana cascadae over ...201424171949
rapid increases and time-lagged declines in amphibian occupancy after wildfire.climate change is expected to increase the frequency and severity of drought and wildfire. aquatic and moisture-sensitive species, such as amphibians, may be particularly vulnerable to these modified disturbance regimes because large wildfires often occur during extended droughts and thus may compound environmental threats. however, understanding of the effects of wildfires on amphibians in forests with long fire-return intervals is limited. numerous stand-replacing wildfires have occurred since ...201322978248
community ecology of invasions: direct and indirect effects of multiple invasive species on aquatic communities.with many ecosystems now supporting multiple nonnative species from different trophic levels, it can be challenging to disentangle the net effects of invaders within a community context. here, we combined wetland surveys with a mesocosm experiment to examine the individual and combined effects of nonnative fish predators and nonnative bullfrogs on aquatic communities. among 139 wetlands, nonnative fish (bass, sunfish, and mosquitofish) negatively influenced the probability of occupancy of pacifi ...201222834365
genetic comparison of water molds from embryos of amphibians rana cascadae, bufo boreas and pseudacris regilla.water molds that cause the disease saprolegniasis have been implicated in widespread mortality of amphibian embryos. however, because of the limitations of traditional identification methods, water mold species involved in die-offs or utilized in ecological studies often remain unidentified or identified only as saprolegnia ferax. furthermore, water mold taxonomy requires revision, so very distinct organisms may all be called s. ferax. recent dna-based studies indicate that the diversity of wate ...201222691981
acute toxicity of zinc to several aquatic species native to the rocky mountains.national water-quality criteria for the protection of aquatic life are based on toxicity tests, often using organisms that are easy to culture in the laboratory. species native to the rocky mountains are poorly represented in data sets used to derive national water-quality criteria. to provide additional data on the toxicity of zinc, several laboratory acute-toxicity tests were conducted with a diverse assortment of fish, benthic invertebrates, and an amphibian native to the rocky mountains. tes ...201221811884
hatching success and pesticide exposures in amphibians living in agricultural habitats of the south okanagan valley, british columbia, canada (2004-2006).in 2004 to 2006, in the okanagan valley, british columbia, canada, we measured pesticides, water chemistry, and hatching success of great basin spadefoot (spea intermontana), pacific treefrog (pseudacris regilla), western toad (bufo boreas), and columbia spotted frog (rana luteiventris). predator-proof cages containing gosner stage 4 eggs were placed in ponds in nonagricultural reference sites in conventionally sprayed and organic orchards. seventeen pesticides were detected in ponds in sprayed ...201020821610
quantifying bufo boreas connectivity in yellowstone national park with landscape genetics.a major objective of ecology is to understand how ecological processes limit population connectivity and species' distributions. by spatially quantifying ecological components driving functional connectivity, we can understand why some locally suitable habitats are unoccupied, resulting in observed discontinuities in distribution. however, estimating connectivity may be difficult due to population stochasticity and violations of assumptions of parametric statistics. to address these issues, we p ...201020380214
sublethal predators and their injured prey: linking aquatic predators and severe limb abnormalities in amphibians.while many predators completely consume their prey, others feed only on blood or tissue without killing the prey, sometimes causing ecologically significant levels of injury. we investigated the importance of sublethal predator attacks in driving an emerging issue of conservation importance: missing-limb deformities in amphibians. we combined long-term field data and manipulative experiments to evaluate the role of sublethal predation in causing abnormalities in two regions of central oregon, u. ...201020380213
hormonal regulation of skin gland development in the toad (bufo boreas): the role of the thyroid hormones and metamorphic climax, anurans develop skin glands that migrate from the epidermis into the dermis. thyroxine (t4) stimulates skin gland differentiation and migration, and a previous study showed that corticosterone (cort) treatment of larvae is inhibitory. the current study used histological analyses to address the mechanism of cort's prevention of skin gland development. two types of glands were observed in controls at metamorphic climax: the first type resembled granular glands found in adult ...19958536925
mitochondrial dna evolution in the anaxyrus boreas species group.the anaxyrus boreas species group currently comprises four species in western north america including the broadly distributed a. boreas, and three localized species, anaxyrus nelsoni, anaxyrusexsul and anaxyrus canorus. phylogenetic analyses of the mtdna 12s rdna, cytochrome oxidase i, control region, and restriction sites data, identified three major haplotype clades. the northwest clade (nw) includes both subspecies of a. boreas and divergent minor clades in the middle rocky mountains, coastal ...200918662792
myiasis by lucilia silvarum (calliphoridae) in amphibian species in boreal alberta, canada.we report myiasis by lucilia silvarum with an overall prevalence of 0.9% in amphibian populations in boreal alberta. in the period 1998--1999, we documented l. silvarum infestations in wild populations of wood frog (rana sylvatica), boreal chorus frog (pseudacris maculata), boreal toad (bufo boreas boreas), and canadian toad (b. hemiophrys). we believe this is the first record of this parasite from boreal and canadian toads. almost all previous records of l. silvarum parasitism in north america ...200818576743
responses of pond-breeding amphibians to wildfire: short-term patterns in occupancy and colonization.wildland fires are expected to become more frequent and severe in many ecosystems, potentially posing a threat to many sensitive species. we evaluated the effects of a large, stand-replacement wildfire on three species of pond-breeding amphibians by estimating changes in occupancy of breeding sites during the three years before and after the fire burned 42 of 83 previously surveyed wetlands. annual occupancy and colonization for each species was estimated using recently developed models that inc ...200717708217
pesticides are involved with population declines of amphibians in the california sierra nevadas.several species of frogs and toads are in serious decline in the sierra nevada mountains of california. these species include the threatened red-legged frog ( rana aurora ), foothill yellow-legged frog ( r. boylii ), mountain yellow-legged frog ( r. muscosa ), cascades frog ( rana cascadae ), western toad ( bufo boreas ) and yosemite toad ( b. canorus ). for many of these species current distributions are down to 10% of historical ranges. several factors including introduced predators, habitat l ...200112805670
juvenile amphibians do not avoid potentially lethal levels of urea on soil substrate.we examined the effects of a forest fertilizer (urea) on newly metamorphosed terrestrial amphibians (western toads, bufo boreas; cascades frogs, rana cascadae; long-toed salamanders, ambystoma macrodactylum; and roughskin newts, taricha granulosa). we examined avoidance behavior of western toads and cascades frogs on both paper towel and soil substrates dosed with urea (control and 100 kg n/ha and an additional treatment of 50 kg n/ha for western toads on soil substrate) and avoidance behavior o ...200111596767
cutaneous chytridiomycosis in dwarf aquatic frogs (hymenochirus boettgeri) originating from southeast asia and in a western toad (bufo boreas) from northeastern british columbia. 200111360864
the genetics of amphibian declines: population substructure and molecular differentiation in the yosemite toad, bufo canorus (anura, bufonidae) based on single-strand conformation polymorphism analysis (sscp) and mitochondrial dna sequence data.we present a comprehensive survey of genetic variation across the range of the narrowly distributed endemic yosemite toad bufo canorus, a declining amphibian restricted to the sierra nevada of california. based on 322 bp of mitochondrial cytochrome b sequence data, we found limited support for the monophyly of b. canorus and its closely related congener b. exsul to the exclusion of the widespread western toad b. boreas. however, b. exsul was always phylogenetically nested within b. canorus, sugg ...200010736023
sex recognition and mate choice by male western toads, bufo field-based choice experiments, we examined sex recognition and mate choice in male western toads, bufo boreas. when given a simultaneous choice between a male and a female of equal size, males did not discriminate between the sexes and attempted to amplex a male or a female with equal frequency. when a test male clasped a stimulus male, the stimulus male uttered a release call that caused the test male to release the stimulus male. male-male amplexus never lasted more than 3 s, but male-fema ...19989642006
histological examination of the effects of corticosterone in larvae of the western toad, bufo boreas (anura: bufonidae), and the oriental fire-bellied toad, bombina orientalis (anura: discoglossidae).the effects of corticosterone (cort)-treatment on various tissues were examined in two species of anuran larvae, the discoglossid bombina orientalis, and the bufonid bufo boreas. corticosterone was administered directly into aquarium water for 15 days. after treatment, histological analyses were conducted on skin, gut, spleen, thymus, and neural and muscle tissue. corticosterone treatment prevented sloughing of the skin, which resulted in a build-up of stratum corneum, and inhibited the developm ...19958531204
uv repair and resistance to solar uv-b in amphibian eggs: a link to population declines?the populations of many amphibian species, in widely scattered habitats, appear to be in severe decline; other amphibians show no such declines. there is no known single cause for the declines, but their widespread distribution suggests involvement of global agents--increased uv-b radiation, for example. we addressed the hypothesis that differential sensitivity among species to uv radiation contributes to these population declines. we focused on species-specific differences in the abilities of e ...19948127883
is walking costly for anurans? the energetic cost of walking in the northern toad bufo boreas halophiluslocomotor mode and the maximal capacity for aerobic metabolism are thought to be co-adapted in anuran amphibians. species that rely heavily on walking often have high capacities for aerobic metabolism relative to species that rely primarily on saltation. we tested the hypothesis of co-adaptation of gait and aerobic metabolism by investigating the locomotor energetics of bufo boreas halophilus, a toad that walks, but does not hop. rates of oxygen consumption during locomotion were measured in an ...19949317560
interactions of temperature and steroids on larval growth, development, and metamorphosis in a toad (bufo boreas).the effects of temperature and steroids [testosterone (t), estradiol (e2), and corticosterone (b)] on premetamorphic growth and development were investigated in the toad (bufo boreas). the effects of steroids were both temperature and age dependent. in the first experiment, steroids (1.1-1.4 microm) were administered by dissolving them in the water beginning 1 day after hatching at 22 degrees c or 27 degrees c. at 22 degrees c, b inhibited growth (p < 0.001) but had no significant effect on deve ...19938515203
a dna-based assay identifies batrachochytrium dendrobatidis in amphibians.chytridiomycosis caused by batrachochytrium dendrobatidis (chytridiomycota) has been implicated in declines of amphibian populations on four continents. we have developed a sensitive and specific polymerase chain reaction-based assay to detect this pathogen. we isolated b. dendrobatidis from captive and wild amphibians collected across north america and sequenced the internal transcribed spacer regions of the rdna cassette of multiple isolates. we identified two primers (bd1a and bd2a) that are ...200415465708
the effects of ultraviolet-b radiation on the toxicity of fire-fighting chemicals.the interactive effects of ultraviolet (uv) and fire-retardant chemicals were evaluated by exposing rainbow trout (oncorhyncus mykiss) juveniles and tadpoles of southern leopard frogs (rana sphenocephala) to six fire-retardant formulations with and without sodium ferrocyanide (yellow prussiate of soda [yps]) and to yps alone under three simulated uv light treatments. yellow prussiate of soda is used as a corrosion inhibitor in some of the fire-retardant chemical formulations. the underwater uv i ...200312836977
notes on myiasis of the toad, bufo boreas boreas baird and girard. 194720267545
mating pattern variability among western toad (bufo boreas) populations.breeding ecology and mating patterns of the western toad, bufo boreas, were examined in three large explosively breeding populations in the oregon cascade mountains. two mating patterns occurred variably within and among the three populations. first, a large male mating advantage was observed in two of the three populations when data from all the days of data collection were combined. when each day of breeding was analyzed separately, there was a large male mating advantage on 3 of 5 days at one ...198628311920
abnormal feeding behavior of western toads (bufo boreas) kept in a hyperosmotic environment. i. a quantitative behavioral analysis as related to cerebral amino acid concentrations.discriminant analysis of eleven behavioral variables associated with feeding permitted the assignment of hyperosmotically-acclimating (hoa) toads (bufo boreas) to six different behavioral states. these behavioral states could be correlated with specific alterations in the level of select amino acids in three regions of the toad's central nervous system. by considering only those amino acids that showed equivalent levels in corresponding brain regions of normally-behaving, freshwater-acclimating ...19863725835
an investigation of the alarm response in bufo boreas and rana cascadae tadpoles.tadpoles of the western toad (bufo boreas) and of the cascades frog (rana cascadae) show an alarm reaction to an extract containing chemical cues from damaged conspecifics. the mean time spent by individual b. boreas tadpoles in the half of the test tank to which the extract solution was added was significantly lower than expected by chance. activity was also significantly greater in bufo extract tests than in control tests. tadpoles did not avoid an extract of another tadpole species (hyla regi ...19853994624
role of carbon dioxide fixation, blood aspartate and glutamate in the adaptation of amphibian brain tissues to a hyperosmotic internal environment.mechanisms have been examined by which hyperosmotic blood plasma might elevate the levels of aspartate and glutamate in the brain of the toad bufo boreas. co2 fixation was assessed by two in vivo methods using [2-14 c]glucose injected intracisternally. thirty minutes after injection, the 14c labeling of glutamate and aspartate was more than 100 times greater in brain than in liver. in brain tissues, 40 + % of 14c atoms appeared to be incorporated into aspartate via the pyruvate carboxylase pathw ...19806782498
the effects of arginine vasotocin and various microtubular poisons on water transfer and sodium transport across the pelvic skin of the toad bufo boreas in vitro. 19807364208
effect of constant and fluctuating temperatures on resting and active oxygen consumption of toads, bufo boreas.the relations of standard and active rates of oxygen consumption to body temperature (tb) were tested in montane bufo b. boreas and lowland bufo boreas halophilus acclimated to constant t b of 10, 20, or 30° c or to a fluctuating cycle of 5-30° c. standard metabolic rates (smr) of boreas acclimated to 30° c and halophilus acclimated to 10° c show pronounced regions of thermal independence but all other standard and active metabolic rates of groups acclimated to other thermal regimes are thermall ...197928309437
factors affecting body temperatures of toads.factors influencing levels and rates of variation of body temperature (t b) in montane bufo boreas boreas and in lowland bufo boreas halophilus were investigated as an initial step toward understanding the role of natural thermal variation in the physiology and energetics of these ectothermic animals. body temperatures of boreas can vary 25-30° c over 24-h periods. such variation is primarily due to both nocturnal and diurnal activity and the physical characteristics of the montane environment. ...197828309733
the effects of sublethal concentrations of organophosphorus insecticides and an insect growth regulator on temperature tolerance in hydrated and dehydrated juvenile western toads, bufo boreas. 19762410
photoreactivation of potentially lethal, uv-induced damage to boreal toad (bufo boreas boreas) tadpoles. 19751207374
the relation of blood hemoglobin concentration to body size in the toad bufo boreas. 19744154168
the water balance response of the pelvic "patch" of bufo punctatus and bufo boreas;. 19744156284
metabolism of glucose, amino acids, and some related metabolites in the brain of toads (bufo boreas) adapted to fresh water or hyperosmotic environments. 19734724320
comparative rates of rehydration from soil in two species of toads, bufo boreas and bufo punctatus. 19705463990
the effects of heavy gamma irradiation upon pituitary glands transplanted into hypophysectomized tadpoles of bufo boreas. 195713513963
predicting breeding habitat for amphibians: a spatiotemporal analysis across yellowstone national park.the ability to predict amphibian breeding across landscapes is important for informing land management decisions and helping biologists better understand and remediate factors contributing to declines in amphibian populations. we built geospatial models of likely breeding habitats for each of four amphibian species that breed in yellowstone national park (ynp). we used field data collected in 2000-2002 from 497 sites among 16 basins and predictor variables from geospatial models produced from re ...201122073642
identification of bufadienolides from the boreal toad, anaxyrus boreas, active against a fungal pathogen.amphibian granular glands provide a wide range of compounds on the skin that defend against pathogens and predators. we identified three bufadienolides-the steroid-like compounds arenobufagin, gamabufotalin, and telocinobufagin-from the boreal toad, anaxyrus boreas, through liquid chromatography mass spectrometry (lc/ms). compounds were detected both after inducing skin gland secretions and in constitutive mucosal rinses from toads. we described the antimicrobial properties of each bufadienolide ...201728631214
virulence variation among strains of the emerging infectious fungus batrachochytrium dendrobatidis (bd) in multiple amphibian host species.emerging infectious diseases have been documented in numerous plant and animal populations. the infectious disease amphibian chytridiomycosis, caused by the fungus batrachochytrium dendrobatidis (bd), is associated with global amphibian population declines. while much bd-amphibian research has centered on response variation in hosts, a paucity of information exists on how variation in the pathogen, such as strain differences, affects infection dynamics. to examine how different bd strains may di ...201728492179
complex life cycles and density dependence: assessing the contribution of egg mortality to amphibian the last decade there has been increasing evidence of amphibian declines from relatively pristine areas. some declines are hypothesized to be the result of egg mortality caused by factors such as elevated solar uv-b irradiation, chemical pollutants, pathogenic fungi, and climate change. however, the population-level consequences of egg mortality have not been examined explicitly, and may be complicated by density dependence in intervening life-history stages. here we develop a demographic mod ...200228466219
selective mortality and reproduction in a natural population of bufo boreas. 198028563199
natural hybridization and genetic divergence between the toads bufo boreas and bufo punctatus. 197928563922
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