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
on the diversity of sperm histones in the vertebrates. i. changes in basic proteins during spermiogenesis in the newt notophthalmus viridescens.sperm histones display great variability in contrast to the conservation of most classes of somatic histones. to study this paradox, this series of papers examines the variation of histone patterns in the testis and sperm of vertebrates, particularly amphibians and reptiles, and attempts to relate such variation to genetically based sex determination as hypothesized by bloch [genetics supplement 61, 93 (1969)]. in the present study we have investigated spermiogenesis in the newt notophthalmus vi ...19761010162
comparison of the sequence and structure of transcription factor iiia from bufo americanus and rana pipiens.amino acid (aa) sequences of transcription factor iiia (tfiiia) from the toad, bufo americanus, and the grass frog, rana pipiens, were determined by cdna cloning and dna sequencing. the 3'-untranslated regions of the cdnas reveal that the tfiiia gene polyadenylation signal is attaaa, rather than the conventional aataaa. the b. americanus and r. pipiens proteins share about 60% aa sequence homology with each other and with xenopus laevis tfiiia. although these results indicate that tfiiia has mor ...19921398134
stimulation of adenosine 3',5'-monophosphate formation in mononuclear leukocytes by toad venoms.the content of adenosine 3',5'-monophosphate in human mononuclear leukocytes was enhanced 3-5-times by venoms obtained from african toad (bufo africanus), american toad (bufo americanus), colorado river toad (bufo arenarum) and marine toad (bufo marinus) at 25 micrograms/ml for 5 min of incubation at 37 degrees c. the maximum stimulation was observed after 1-5 min of incubation. the half-maximal stimulation was observed at 0.1 micrograms/ml venom obtained from colorado river toad (bufo arenarum) ...19826184077
mating call phonotaxis in the female american toad: induction by hormones.gravid, female american toads are known to move toward conspecific mating calls. this behavior, as well as ovulation, often can be induced by the injection of human chorionic gonadotropin (hcg). it was found that hcg-induced phonotaxis could be terminated by the injection of indomethacin (an inhibitor of prostaglandin synthesis) and then reinstated by the injection of prostaglandin f2 alpha. a drug regimen was devised that allowed elicitation of phonotaxis, indistinguishable from that induced by ...19846235146
the effects of aquatic oxygen concentration, body size and respiratory behaviour on the stamina of obligate aquatic (bufo americanus) and facultative air-breathing (xenopus laevis and rana berlandieri) anuran larvae.larvae of the anurans rana berlandieri and xenopus laevis have lungs and can breathe air as well as irrigate buccal and pharyngeal surfaces for aquatic respiration. larvae of bufo americanus lack lungs until just before metamorphosis and are obligately aquatic. we examined the relationship between the locomotor stamina (time to fatigue), aquatic oxygen concentration, body size, and respiratory behaviour of swimming larvae of these species, with the following results: stamina is size-dependent in ...19836619726
amphibian neurotensin (nt) is not xenopsin (xp): dual presence of nt-like and xp-like peptides in various clarify whether xenopsin (xp) is the amphibian counterpart of mammalian neurotensin (nt), extracts of skin, brain, and intestine from representative amphibians were subjected to immunochemical, chromatographic, and biological analyses. the results indicated the dual presence of nt- and xp-like peptides in extracts of tissues from xenopus laevis, rana catesbeiana, rana pipiens, bufo marinus, bufo americanus, and necturus maculosus, which were separated during gel chromatography on sephadex g-2 ...19826977439
diagnostic exercise: ulcerative dermatitis and cellulitis in american toads. 19938158992
comparative enzymology of amp deaminase, adenylate kinase, and creatine kinase in vertebrate heart and skeletal muscle: the characteristic amp deaminase levels of skeletal versus cardiac muscle are reversed in the north american toad.the specific activity of three characteristic enzymes, adenylate deaminase, adenylate kinase, and creatine kinase, in the skeletal muscles and heart of a variety of vertebrate land animals, including the human, are surveyed. data from this study and available studies in the literature suggest that adenosine monophosphate deaminase in land vertebrates is quite high in white skeletal muscle, usually somewhat lower in red muscle, and 15- to 500-fold lower in cardiac muscle. adenosine monophosphate ...19938394393
caged amphibian tadpoles and in situ genotoxicity monitoring of aquatic environments with the alkaline single cell gel electrophoresis (comet) previous studies we demonstrated that indigenous amphibian tadpoles are suitable organisms for monitoring small bodies of water (e.g., creeks, ponds, and drainage ditches) using the alkaline single cell gel electrophoresis (scg) or 'comet' assay. this approach involves detection, under alkaline conditions, of cell dna fragments which on electrophoresis migrate from the nuclear core, resulting in a 'comet with tail' formation. however, although often plentiful, tadpoles are not present in all ...19989651536
the life history and host specificity of hepatozoon clamatae (apicomplexa: adeleorina) and its-1 nucleotide sequence variation of hepatozoon species of frogs and mosquitoes from ontario.the life cycle of an intraerythrocytic hemogregarine, hepatozoon clamatae, was studied in green frogs (rana clamitans melanota), bullfrogs (rana catesbeiana), northern leopard frogs (rana pipiens), and in the mosquito, culex territans. gametogenesis, fertilization, and sporogony occurred within cells of the malpighian tubules of laboratory-reared cx. territans that had fed on naturally infected frogs. mature oocysts containing hundreds of sporocysts were observed in mosquitoes 30 days postfeedin ...19989714212
cryopreservation of spermatozoa from freeze-tolerant and -intolerant anurans.spermatozoa of the freeze-tolerant wood frog (rana sylvatica) were used to develop a general protocol for the frozen storage of amphibian spermatozoa. tolerance of spermatozoa to cryoprotective agents and freezing in suspension (-80 degrees c) was determined from rates of sperm lysis and dual-fluorochrome vital dye assays. we tested the efficacy of four cryoprotectants (me2so, methanol, glycerol, and ethylene glycol), two supplements (fetal bovine serum or glutathione), and combinations of these ...19989769166
blood lead content in a peri-urban population of the south american toad bufo arenarum.blood pb concentration in a south american toad bufo arenarum population (n = 152) was determined over 10 samplings carried out between december 1996 and november 1999. the studied population lived in the surroundings of the la plata city, the largest industrial-urban setting of the buenos aires province, argentina. the presence of the metal was detected in all the samples tested, the mean concentration range being 1.99-4.66 mg dl(-1). some preliminary environmental data on soil content of pb in ...200111346044
membrane currents in the oocyte of the toad bufo arenarum.the amphibian oocyte cell model is widely used for heterologous expression of ionic channels and receptors. little is known, however, about the physiology of oocyte cell models other than xenopus laevis. in this study, the two-electrode voltage clamp technique was used to assess the most common electrical patterns of oocytes of the south american toad bufo arenarum. basal membrane resistance, resting potential, and ionic currents were determined in this cell model. the oocyte transmembrane resis ...200211857475
active sodium transport by the isolated toad bladder.studies were made of the active ion transport by the isolated urinary bladder of the european toad, bufo bufo, and the large american toad, bufo marinus. the urinary bladder of the toad is a thin membrane consisting of a single layer of mucosal cells supported on a small amount of connective tissue. the bladder exhibits a characteristic transmembrane potential with the serosal surface electrically positive to the mucosal surface. active sodium transport was demonstrated by the isolated bladder u ...195813514002
effect of ph and release on two life stages of four anuran amphibians.using three native canadian and one exotic anuran species, the interactive toxicity of ph and the forestry used-herbicide release (triclopyr [3,5,6-trichloro-2-pyridl-oxyacetic acid]) was assessed. embryonic and larval (gosner 25) stages of rana pipiens, rana clamitans, bufo americanus, and xenopus laevis were exposed to treatments for at least 96 h in a static-renewal system using a central composite rotatable design. mortality and the prevalence of malformations were modeled using generalized ...200314587907
comparative effects of ph and vision herbicide on two life stages of four anuran amphibian, a glyphosate-based herbicide containing a 15% (weight:weight) polyethoxylated tallow amine surfactant blend, and the concurrent factor of ph were tested to determine their interactive effects on early life-stage anurans. ninety-six-hour laboratory static renewal studies, using the embryonic and larval life stages (gosner 25) of rana clamitans, r. pipiens, bufo americanus, and xenopus laevis, were performed under a central composite rotatable design. mortality and the prevalence of malfor ...200415095875
synergistic impacts of malathion and predatory stress on six species of north american tadpoles.the decline of many amphibian populations is associated with pesticides, but for most pesticides we know little about their toxicity to amphibians. malathion is a classic example; it is sprayed over aquatic habitats to control mosquitoes that carry malaria and the west nile virus, yet we know little about its effect on amphibians. i examined the survival of six species of tadpoles (wood frogs, rana sylvatica; leopard frogs, r. pipiens; green frogs, r. clamitans; bullfrogs, r. catesbeiana; americ ...200415095908
metamorphosis of two amphibian species after chronic cadmium exposure in outdoor aquatic mesocosms.amphibian larvae at contaminated sites may experience an alteration of metamorphic traits and survival compared to amphibians in uncontaminated conditions. effects of chronic cadmium (cd) exposure on the metamorphosis of american toads (bufo americanus) and southern leopard frogs (rana sphenocephala) were determined. the two species were reared separately from shortly after hatching through metamorphosis in outdoor mesocosms (1,325-l polyethylene cattle tanks) that simulated natural ponds and en ...200516152972
differential metamorphosis alters the endocrine response in anuran larvae exposed to t3 and atrazine.pesticide chemical contamination is one of the suspected contributors of the amphibian population decline. the herbicide atrazine is one of the major surface water contaminants in the u.s. a previous study has shown that atrazine at concentrations as low as 100 parts per billion (ppb) increased the time to metamorphosis in xenopus laevis tadpoles. however, questions remain as to the applicability of a study of a non-native species to a native organism. the possible effects of atrazine on develop ...200516213604
serum protein profile and blood cell counts in adult toads bufo arenarum(amphibia: anura: bufonidae): effects of sublethal lead acetate.lead is a multiple-source pollutant, well known for its toxicity, of great risk both for the environment and human health. the main target organs of lead are the hematopoietic, nervous, and renal systems; there are also reports in support of its impairment effects on the reproductive and immune systems. it is well known that most of the metal is accumulated in the blood cells and that many of the deleterious effects are related to its circulating concentrations. these adverse effects have been d ...200616446996
multiple stressors in amphibian communities: effects of chemical contamination, bullfrogs, and fish.a leading hypothesis of amphibian population declines is that combinations of multiple stressors contribute to declines. we examined the role that chemical contamination, competition, and predation play singly and in combination in aquatic amphibian communities. we exposed larvae of american toads (bufo americanus), southern leopard frogs (rana sphenocephala), and spotted salamanders (ambystoma maculatum) to overwintered bullfrog tadpoles (r. catesbeiana), bluegill sunfish (lepomis macrochirus), ...200717479852
the natural occurrence of redleg, pseudomonas hydrophila, in a population of american toads, bufo americanus. 194918130557
suitability of golf course ponds for amphibian metamorphosis when bullfrogs are removed.managing areas designed for human recreation so that they are compatible with natural amphibian populations can reduce the negative impacts of habitat destruction. we examined the potential for amphibians to complete larval development in golf course ponds in the presence or absence of overwintered bullfrog tadpoles (rana catesbeiana), which are frequently found in permanent, human-made ponds. we reared larval american toads (bufo americanus), southern leopard frogs (r. sphenocephala), and spott ...200818254862
all hosts are not equal: explaining differential patterns of malformations in an amphibian community.1. within a community, different host species often exhibit broad variation in sensitivity to infection and disease. because such differences can influence the strength and outcome of community interactions, it is essential to understand differential disease patterns and identify the mechanisms responsible. 2. in north american wetlands, amphibian species often exhibit extraordinary differences in the frequency of limb malformations induced by the digenetic trematode, ribeiroia ondatrae. by coup ...200918671806
changes in the antioxidant metabolism in the embryonic development of the common south american toad bufo arenarum: differential responses to pesticide in early embryos and autonomous-feeding larvae.amphibians may be critically challenged by aquatic contaminants during their embryonic development. many classes of compounds, including organophosphorus pesticides, are able to cause oxidative stress that affects the delicate cellular redox balance regulating tissue modeling. we determined the progression of antioxidant defenses during the embryonic development of the south american common toad, bufo arenarum. superoxide dismutase (sod) and catalase (cat) activities were high in the unfertilize ...200818752312
behavioral response and kinetics of terrestrial atrazine exposure in american toads (bufo americanus).amphibians in terrestrial environments obtain water through a highly vascularized pelvic patch of skin. chemicals can also be exchanged across this patch. atrazine (atz), a widespread herbicide, continues to be a concern among amphibian ecologists based on potential exposure and toxicity. few studies have examined its impact on the terrestrial juvenile or adult stages of toads. in the current study, we asked the following questions: (1) will juvenile american toads (bufo americanus) avoid soils ...200919198750
pcr detection of ranavirus in adult anurans from the louisville zoological garden.ranaviruses are known to cause mortality in a variety of anuran species and have the potential to significantly impact wild and captive frog populations. in this study, 16 captive frogs and toads from the louisville zoological garden were examined for the presence of ranavirus; this group included 14 cope's grey tree frogs (hyla chrysoscelis), an american toad (bufo americanus), and a southern toad (bufo terrestris). all animals were wild caught and were evaluated via polymerase chain reaction ( ...200919746873
kinematics and hydrodynamics analysis of swimming anurans reveals striking inter-specific differences in the mechanism for producing thrust.this study aimed to compare the swimming kinematics and hydrodynamics within and among aquatic and semi-aquatic/terrestrial frogs. high-speed video was used to obtain kinematics of the leg joints and feet as animals swam freely across their natural range of speeds. blade element analysis was then used to model the hydrodynamic thrust as a function of foot kinematics. two purely aquatic frogs, xenopus laevis and hymenochirus boettgeri, were compared with two semi-aquatic/terrestrial frogs, rana p ...201020118313
extracts of the invasive shrub lonicera maackii increase mortality and alter behavior of amphibian larvae.water-soluble phytochemicals produced by invasive plants may represent novel elements of invaded ecosystems that can precipitate a variety of direct and indirect effects on native organisms. phenolic compounds in particular are a common plant defense, and these compounds may have disproportionate impacts on amphibians compared to other taxa. we coupled an exploration of invasive plant extract effects on larvae of four amphibian species (the salamander ambystoma maculatum, the toad anaxyrus ameri ...201020938785
interactive effects of maternal and dietary mercury exposure have latent and lethal consequences for amphibian larvae.organisms born into the same contaminated environment as their parents can be exposed both maternally and environmentally to contaminants, potentially placing them at greater risk of adverse effects than when exposed via either of the two pathways independently. we examined whether embryonic exposure to maternally derived mercury (hg) interacts with dietary exposure to negatively influence larval development in american toads ( bufo americanus ). we collected eggs from breeding pairs at referenc ...201121428394
varying responses of northeastern north american amphibians to the chytrid pathogen batrachochytrium dendrobatidis.chytridiomycosis, caused by batrachochytrium dendrobatidis (bd), is widespread among amphibians in northeastern north america. it is unknown, however, whether bd has the potential to cause extensive amphibian mortalities in northeastern north america as have occurred elsewhere. in the laboratory, we exposed seven common northeastern north american amphibian species to bd to assess the likelihood of population-level effects from the disease. we exposed larval wood frogs (lithobates sylvaticus) an ...201122181933
development of trypanosoma fallisi in the leech, desserobdella picta, in toads (bufo americanus), and in vitro. a light and electron microscopic study.the development of trypanosoma fallisi of bufo americanus from algonquin park, ontario was studied by light and electron microscopy in blood culture, in its leech vector desserobdella (= batracobdella) picta, and in its toad host. in culture, bloodstream trypomastigotes transformed within one day to elongate epimastigotes which divided into rosettes. these gave rise to amastigotes, spheromastigotes, stumpy and elongate epimastigotes, and slender metacyclic trypomastigotes over a 4- to 6-day peri ...20071994366
the fine structure of fungiform papillae and epithelium of the tongue of a south american toad, calyptocephalella gayi. 20144107470
new and uncommon indole- and imidazole-alkylamines in skins of amphibians from australia and papua new guinea.extracts of the skin of some amphibians from australia and papua new guinea contained, in addition to the usual 5-hydroxyindolealkylamines and histamine: a. two new, hitherto unknown indolealkylamines, i.e. o-sulphate of bufotenidine and 2-(3-indolyl) ethyltrimethylammonium, a quaternary ammonium base of tryptamine. the rare o-sulphate of bufotenine was also present, the occurrence of which had previously been demonstrated only in the skin of some south american toads; b. a series of uncommon im ...2001134551
angiotensin converting enzyme in the toad bufo arenarum.angiotensin converting enzyme activity (acea) was determined in serum, kidney, whole skin and isolated epithelia homogenates of the south american toad bufo arenarum. acea was present in the tissues and serum of the toad. the activity was higher in the kidney, as compared to that of the whole skin or isolated epithelium. captopril, teprotide and edta, caused a significant decrease in the acea. possible physiological roles for the presence of acea in the toad are discussed.20022869873
mating call phonotaxis in female american toad: lesions of anterior preoptic nucleus.lesions of the preoptic area and immediately adjacent septal area were made in female american toads, bufo americanus. the ability to show mating call phonotaxis (mcp) was then tested for. the intensity of mcp was found to decrease as the degree of damage to the anterior tip of the anterior preoptic nucleus (apon) increased. the apon is known to concentrate androgens and to be essential for mating calling by male anurans. perhaps the apon is involved also in the detection of the elevated levels ...20102925180
thermal regulation of the immune response in south american toads (bufo marinus). 20154631060
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
exposure to corticosterone affects host resistance, but not tolerance, to an emerging fungal responses to pathogens include defenses that reduce infection burden (i.e., resistance) and traits that reduce the fitness consequences of an infection (i.e., tolerance). resistance and tolerance are affected by an organism's physiological status. corticosterone ("cort") is a hormone that is associated with the regulation of many physiological processes, including metabolism and reproduction. because of its role in the stress response, cort is also considered the primary vertebrate stress h ...201727690360
most of the dominant members of amphibian skin bacterial communities can be readily cultured.currently, it is estimated that only 0.001% to 15% of bacteria in any given system can be cultured by use of commonly used techniques and media, yet culturing is critically important for investigations of bacterial function. despite this situation, few studies have attempted to link culture-dependent and culture-independent data for a single system to better understand which members of the microbial community are readily cultured. in amphibians, some cutaneous bacterial symbionts can inhibit est ...201526162880
effects of amphibian chytrid fungus exposure on american toads in the presence of an insecticide.abiotic factors such as pesticides may alter the impact of a pathogen on hosts, which could have implications for host-pathogen interactions and may explain variation in disease outbreaks in nature. in the present laboratory experiment, american toad (anaxyrus americanus) metamorphs were exposed to the amphibian chytrid fungal pathogen batrachochytrium dendrobatidis (bd) and environmentally relevant concentrations of the insecticide malathion to determine whether malathion altered the effects of ...201425099070
the benefits of coinfection: trematodes alter disease outcomes associated with virus infection.1.coinfections are increasingly recognized as important drivers of disease dynamics. consequently, greater emphasis has been placed on integrating principles from community ecology with disease ecology to understand within-host interactions among parasites. using larval amphibians and two amphibian parasites (ranaviruses and the trematode echinoparyphium sp.), we examined the influence of coinfection on disease outcomes. 2.our first objective was to examine how priority effects (the timing and s ...201728317105
new host records for myxidium serotinum (protozoa: myxosporea) from north american amphibians.three hundred twenty-five amphibians (80 salamanders, 245 frogs and toads) from arkansas and texas, representing 28 species within 9 families (ambystomatidae, plethodontidae, salamandridae, sirenidae, bufonidae, hylidae, leptodacytlidae, microhylidae, ranidae) were examined for gall bladder myxosporeans. of these, 32 (10%) were found to harbor myxidium serotinum kudo and sprague, 1940, including 3 (4%) of the salamanders and 29 (12%) of the frogs and toads. this report documents 6 new host recor ...19957776139
new effects of roundup on amphibians: predators reduce herbicide mortality; herbicides induce antipredator morphology.the use of pesticides is important for growing crops and protecting human health by reducing the prevalence of targeted pest species. however, less attention is given to the potential unintended effects on nontarget species, including taxonomic groups that are of current conservation concern. one issue raised in recent years is the potential for pesticides to become more lethal in the presence of predatory cues, a phenomenon observed thus far only in the laboratory. a second issue is whether pes ...201222611860
immediate and lag effects of pesticide exposure on parasite resistance in larval amphibians.across host-parasite systems, there is evidence that pesticide exposure increases parasite loads and mortality following infection. however, whether these effects are driven by reductions in host resistance to infection or slower rates of parasite clearance is often unclear. using controlled laboratory experiments, we examined the ability of larval northern leopard frogs (lithobates pipiens) and american toads (anaxyrus americanus) to resist and clear trematode (echinoparyphium sp.) infections f ...201728073381
investigation of road salts and biotic stressors on freshwater wetland communities.the application of road deicing salts has led to the salinization of freshwater ecosystems in northern regions worldwide. increased chloride concentrations in lakes, streams, ponds, and wetlands may negatively affect freshwater biota, potentially threatening ecosystem services. in an effort to reduce the effects of road salt, operators have increased the use of salt alternatives, yet we lack an understanding of how these deicers affect aquatic communities. we examined the direct and indirect eff ...201727939632
biomarker analysis of american toad (anaxyrus americanus) and grey tree frog (hyla versicolor) tadpoles following exposure to atrazine.the objective of the current study was to use a biomarker-based approach to investigate the influence of atrazine exposure on american toad (anaxyrus americanus) and grey tree frog (hyla versicolor) tadpoles. atrazine is one of the most frequently detected herbicides in environmental matrices throughout the united states. in surface waters, it has been found at concentrations from 0.04-2859μg/l and thus presents a likely exposure scenario for non-target species such as amphibians. studies have e ...201727912165
soil organic matter content effects on dermal pesticide bioconcentration in american toads (bufo americanus).pesticides have been implicated as a major factor in global amphibian declines and may pose great risk to terrestrial phase amphibians moving to and from breeding ponds on agricultural landscapes. dermal uptake from soil is known to occur in amphibians, but predicting pesticide availability and bioconcentration across soil types is not well understood. the present study was designed to compare uptake of 5 current-use pesticides (imidacloprid, atrazine, triadimefon, fipronil, and pendimethalin) i ...201627028289
ecological stoichiometry quantitatively predicts responses of tadpoles to a food quality gradient.ecological stoichiometry (es) uses elemental ratios and mass balance to explain organismal growth, an important parameter in ecological systems. in this study, we tested quantitative predictions of the es "minimal model" for the growth rates of two tadpole species (wood frogs, lithobates sylvaticus and american toads, anaxyrus americanus), by manipulating light and the quality of a leaf litter mixture in a seminatural mesocosm experiment. we predicted that wood frogs, which consume leaf litter a ...201526405733
effects of tannin source and concentration from tree leaves on two species of tadpoles.vegetation in and around freshwater ecosystems can affect aquatic organisms through the production of secondary compounds, which are retained in leaves after senescence and are biologically active. tannins can be toxic to tadpoles, but the plant source of tannins and tannin concentration have been confounded in experimental designs in previous studies. to examine the effects of the concentration and source of tannins (tree species), we examined the effects of 4 factors on tadpole survival, growt ...201525319714
variation in anti-parasite behaviour and infection among larval amphibian species.along with immune defences, many animals exhibit effective anti-parasite behaviours such as parasite avoidance and removal that influence their susceptibility to infection. host ecology and life history influence investment into comparatively fixed defences such as innate immunity but may affect the strength of anti-parasite behaviours as well. we investigated activity levels in five different species of larval amphibian with varying life histories and ecology in control, novel food stimulus, an ...201424337712
carryover effects in amphibians: are characteristics of the larval habitat needed to predict juvenile survival?carryover effects occur when experiences early in life affect an individual's performance at a later stage. many studies have shown carryover effects to be important for future performance. however, it is currently unclear whether variation in later environments could overwhelm factors from an earlier life stage. we were interested in whether similar patterns would emerge under the same experimental design with similar taxa. to examine this, we implemented a four-way factorial experimental desig ...201324147414
arsenic species and uptake in amphibians (rana clamitans and bufo americanus).total arsenic concentrations and the chemical form, or species, of arsenic were determined in amphibians (rana clamitans and bufo americanus) collected from a site with elevated arsenic concentrations in nova scotia, canada. frog legs had significantly elevated total arsenic concentrations at a contaminated site when compared with a nearby background site and a calculation of the estimated daily intake rates of arsenic indicates that both diet (invertebrate intake) and water absorption are impor ...201323788261
changes in breeding phenology of eastern ontario frogs over four climate change has been implicated in phenological shifts for a variety of taxa. amphibian species in particular are sensitive to changes in their environment due to their biphasic life history and restricted reproductive requirements. previous research has shown that not all temperate amphibian species respond similarly to the same suite of climatic or environmental cues, nor are individual species necessarily uniform in their responses across their range. we examined both the timing of ...201323610628
evaluating the effects of anthropogenic stressors on source-sink dynamics in pond-breeding amphibians.although interwetland dispersal is thought to play an important role in regional persistence of pond-breeding amphibians, few researchers have modeled amphibian metapopulation or source-sink dynamics. results of recent modeling studies suggest anthropogenic stressors, such as pollution, can negatively affect density and population viability of amphibians breeding in isolated wetlands. presumably population declines also result in reduced dispersal to surrounding (often uncontaminated) habitats, ...201323551497
oscillation of an anuran hybrid zone: morphological evidence spanning 50 years.the hybrid zone between the primarily forest-dwelling american toad, anaxyrus americanus, and the prairie-adapted canadian toad, a. hemiophrys, in southeastern manitoba is known to have shifted its position during the past 50 years. hybrid zones are areas of interbreeding between species and their movement across a landscape should reflect their underlying dynamics and environmental change. however, empirical demonstrations of hybrid zone movements over long periods of time are rare. this hybrid ...201223300785
making leaps in amphibian ecotoxicology: translating individual-level effects of contaminants to population viability.concern that environmental contaminants contribute to global amphibian population declines has prompted extensive experimental investigation, but individual-level experimental results have seldom been translated to population-level processes. we used our research on the effects of mercury (hg) on american toads (bufo americanus) as a model for bridging the gap between individual-level contaminant effects and amphibian population viability. we synthesized the results of previous field and laborat ...201223092016
testing wetland features to increase amphibian reproductive success and species richness for mitigation and restoration.aquatic habitat features can directly influence the abundance, species richness, and quality of juvenile amphibians recruited into adult populations. we examined the influences of within-wetland slope, vegetation, and stocked mosquito fish (gambusia affinis) on amphibian metamorph production and species richness during the first two years post-construction at 18 experimental wetlands in northeast missouri (u.s.a.) grasslands. we used an information theoretic approach (aicc) to rank regression mo ...201222908722
a comparison of human chorionic gonadotropin and luteinizing hormone releasing hormone on the induction of spermiation and amplexus in the american toad (anaxyrus americanus).captive breeding programs for endangered amphibian species often utilize exogenous hormones for species that are difficult to breed. the purpose of our study was to compare the efficacy of two different hormones at various concentrations on sperm production, quantity and quality over time in order to optimize assisted breeding.201222905699
effects of leachate from tree leaves and grass litter on tadpoles.tree species composition can change as a result of succession, climate change, fire suppression, and invasive species. these changes clearly affect forests, but they can also affect aquatic ecosystems based on differences in the input quality of leaf litter, such as plant secondary compounds. these compounds vary in type and concentration depending on species and can be toxic to aquatic organisms. to examine toxic effects on pseudacris maculata and pseudacris crucifer tadpoles, we conducted 60-d ...201222488805
use of toe clips as a nonlethal index of mercury accumulation and maternal transfer in amphibians.nonlethal indices of contaminant exposure can facilitate research on the accumulation and effects of contaminants in wildlife. here, we tested the efficacy of using amputated toes ("toe clips"), a common byproduct when marking amphibians in population and genetic studies, to determine mercury (hg) concentrations in amphibians. we examined total mercury (thg) concentrations in american toads (bufo americanus) collected along a contamination gradient at a hg-contaminated field site. we found signi ...201222249488
counterbalancing effects of maternal mercury exposure during different stages of early ontogeny in american toads.maternal transfer of environmental contaminants is a disadvantageous parental effect which can have long-lasting implications for offspring fitness. we investigated the effects of mercury (hg) on the reproductive success of female amphibians and the subsequent effects of maternal transfer on the development of their offspring. american toads (bufo americanus) maternally transferred hg to their eggs, and there was a negative relationship between hg concentrations and the percentage of viable hatc ...201121903241
amphibians at risk? susceptibility of terrestrial amphibian life stages to pesticides.current pesticide risk assessment does not specifically consider amphibians. amphibians in the aquatic environment (aquatic life stages or postmetamorphic aquatic amphibians) and terrestrial living juvenile or adult amphibians are assumed to be covered by the risk assessment for aquatic invertebrates and fish, or mammals and birds, respectively. this procedure has been evaluated as being sufficiently protective regarding the acute risk posed by a number of pesticides to aquatic amphibian life st ...201121898550
do effects of mercury in larval amphibians persist after metamorphosis?despite widespread concern about the role of environmental contaminants in global amphibian declines, and evidence that post-metamorphic life stages contribute disproportionately to amphibian population dynamics, most studies in amphibian ecotoxicology focus on larval life stages. studies that focus solely on early life stages may miss important effects of contaminant exposure, such as latent effects that manifest some time after previous exposure. moreover, it is often assumed that effects obse ...201221850489
aquatic and terrestrial stressors in amphibians: a test of the double jeopardy hypothesis based on maternally and trophically derived contaminants.amphibians with biphasic life histories occupy aquatic and terrestrial habitats at different times in their lives, leading to a double jeopardy of contaminant risk in both habitats. the present study examines individual and interactive effects of mercury exposure to terrestrial adults and aquatic larvae on fitness-related traits of american toads, bufo americanus. eggs from reference mothers or contaminated mothers were allowed to hatch and larvae were fed diets of either no added hg or 2.5 or 1 ...201121755529
insecticide has asymmetric effects on two tadpole species despite priority effects.priority effects are defined as asymmetric responses of different species colonizing the same habitat in different sequences and are important in structuring communities, particularly for ephemeral systems that are colonized annually. amphibians often use ephemeral ponds and have been shown to experience priority effects from interspecific competition. pesticide exposure can impact amphibian species interactions like competition, and has been linked to declines. we investigated whether insectici ...201121431317
does maternal exposure to an environmental stressor affect offspring response to predators?there is growing recognition of the ways in which maternal effects can influence offspring size, physiological performance, and survival. additionally, environmental contaminants increasingly act as stressors in maternal environments, possibly leading to maternal effects on subsequent offspring. thus, it is important to determine whether contaminants and other stressors can contribute to maternal effects, particularly under varied ecological conditions that encompass the range under which offspr ...201121416404
pesticide has asymmetric effects on two tadpole species across density gradient.northern leopard frogs (rana pipiens) have been disappearing throughout their range. the causes for extirpations have been elusive, although habitat alteration appears to be a major factor. pesticides have been implicated in declines in western amphibians, but no mechanism has been identified. we tested the hypothesis that leopard frog tadpoles would be eliminated from insecticide-exposed ponds when they were less abundant than a competitor (american toads, bufo americanus) by manipulating toad ...201121298710
nuclear-mitochondrial discordance and gene flow in a recent radiation of toads.natural hybridization among recently diverged species has traditionally been viewed as a homogenizing force, but recent research has revealed a possible role for interspecific gene flow in facilitating species radiations. natural hybridization can actually contribute to radiations by introducing novel genes or reshuffling existing genetic variation among diverging species. species that have been affected by natural hybridization often demonstrate patterns of discordance between phylogenies gener ...201121255664
carbaryl concentration gradients in realistic environments and their influence on our understanding of the tadpole food web.although exposure to pesticides has been correlated with amphibian declines, the mechanism of their role remains enigmatic. declines have been associated with sublethal exposure, but few outdoor studies have evaluated impacts of low pesticide concentrations. understanding the effects of a range of pesticide concentrations on amphibians in outdoor mesocosms provides a framework for both direct and indirect effects of exposure. indirect effects are challenging to glean from lab studies, which typi ...201121221965
growth, abnormalities, and mortality of tadpoles of american toad exposed to combinations of malathion and nitrate.american toad tadpoles (bufo americanus) were exposed to malathion and nitrate in a fully factorial experiment that crossed four concentrations of malathion ranging between 0 and 1,000 µg malathion/l, and five concentrations of nitrate ranging from 0 to 16 mg no(3) -n/l to identify single and interactive effects. in this 21-d experiment, we recorded tadpole length, mass, survivorship, and frequencies of diamond-shaped and stiff-tail abnormalities. malathion increased frequency of diamond-shaped ...201020931609
effects of aquatic and terrestrial carbaryl exposure on feeding ability, growth, and survival of american toads.the present study evaluates whether larval density and aquatic exposure to the insecticide carbaryl influenced susceptibility to terrestrial exposure of carbaryl through effects on juvenile feeding ability, growth, and survival with metamorphs of american toads (bufo americanus). tadpoles were reared in outdoor mesocosms, and individuals were brought into the lab at metamorphosis for terrestrial exposure studies. the present study indicated that feeding and survival of toads after metamorphosis ...201020872697
roundup and amphibians: the importance of concentration, application time, and stratification.the widespread use of pesticides raises the possibility that non-target organisms might also be affected. to assess this, the traditional approach has been to conduct short-term laboratory experiments spanning a range of lethal concentrations and some longer-duration experiments at sublethal concentrations. while this approach has been very useful, less attention has been paid to the timing of exposure and the impacts of multiple, small exposures versus single, large exposures. we examined the r ...201020821659
bioaccumulation and maternal transfer of mercury and selenium in amphibians.amphibian population declines have been documented worldwide and environmental contaminants are believed to contribute to some declines. maternal transfer of bioaccumulated contaminants to offspring may be an important and overlooked mechanism of impaired reproductive success that affects amphibian populations. mercury (hg) is of particular concern due to its ubiquity in the environment, known toxicity to other wildlife, and complex relationships with other elements, such as selenium (se). the o ...201020821530
mercury accumulation along a contamination gradient and nondestructive indices of bioaccumulation in amphibians.mercury (hg) is an important environmental contaminant due to its global distribution, tendency to bioaccumulate, and toxicity in wildlife. however, hg has received little attention in amphibians compared to other vertebrates. amphibians vary widely in life history strategies and feeding ecologies, which could influence hg exposure and accumulation. to determine whether species and life stage affects hg bioaccumulation, adults from three species (plethodon cinereus, eurycea bislineata, and bufo ...201020821529
parasitism in a community context: trait-mediated interactions with competition and predation.predation and competition can induce important density- and trait-mediated effects on species, with implications for community stability. however, interactions of these factors with parasitism remain understudied. here we investigate interactions among competition, predation and parasitism by crossing tadpole density (bufo americanus), presence of a caged predator (notophthalmus viridescens), and echinostoma trivolvis trematodes, experimentally partitioning their effects on tadpole exposure and ...201020715608
differential effects of malathion and nitrate exposure on american toad and wood frog tadpoles.organisms living in aquatic ecosystems are increasingly likely to be exposed to multiple pollutants at the same time due to the simultaneous use of several pesticides and fertilizers. we examined the single and interactive effects of environmentally realistic concentrations of nitrate and malathion on two species of tadpoles common in agricultural regions of the united states-the american toad (bufo americanus) and the wood frog (rana sylvatica)-using a fully factorial mesocosm experiment that c ...201120556601
intersex gonads in frogs: understanding the time course of natural development and role of endocrine disruptors.the paucity of data on sexual development of anuran amphibians has played an important role in the recent controversy over atrazine exposure. although some studies have demonstrated the presence of abnormal gonads in control treatments, others have not, leading to varying interpretations of the effects of atrazine exposure on sexual development. however, the timing of development varies among anuran amphibians such that, at any snapshot in time, different species may exhibit different stages of ...201019588491
the toxicity of roundup original max to 13 species of larval amphibians.with the increased use of glyphosate-based herbicides (marketed under several names, including roundup and vision), there has been a concomitant increased concern about the unintended impacts that particular formulations containing the popular surfactant polyethoxylated tallowamine (poea) might have on amphibians. published studies have examined a relatively small number of anuran species (primarily from australia and eastern north america) and, surprisingly, no species of salamanders. using a p ...200919405783
effects of aquatic exposure to the insecticide carbaryl and density on aquatic and terrestrial growth and survival in american single mechanism has been explicitly linked to explain global amphibian declines, but pesticides have been implicated as potential drivers. in mesocosm experiments, we tested the hypotheses that american toads (bufo americanus) would respond differently to the insecticide carbaryl at low or high density (i.e., competition) and that postmetamorphic terrestrial growth and survival would differ with larval exposure to pesticides and competition. carbaryl reduced survival to metamorphosis and inc ...200919391669
very highly toxic effects of endosulfan across nine species of tadpoles: lag effects and family-level sensitivity.pesticides are commonly used for health and economic benefits worldwide, but increased use has led to increased contamination of aquatic habitats. to understand potential impacts on nontarget organisms in these habitats, toxicologists generally use short-term (4-d) toxicity tests on model organisms. for most pesticides, few amphibian tests have been conducted, but there is growing concern about the potential impact of pesticides to amphibian populations. for the insecticide endosulfan, previous ...200919358624
effects of pulsed nitrate exposure on amphibian development.most toxicity tests investigate constant concentrations of a chemical. concentrations of many compounds in the environment are dynamic, however, and individuals may be more sensitive to pulses of a chemical initiated at specific points during development. realistic toxicity tests are important to accurately assess the toxicity of a compound. bufo americanus and hyla chrysoscelis tadpoles were exposed to concentrations of nitrate, a pervasive stressor in the environment, up to 5 mg/l of no3-n in ...200919199370
parasites, info-disruption, and the ecology of fear.there is growing interest in the ecological consequences of fear, as evidenced by the numerous studies on the nonconsumptive, trait-mediated effects of predators. parasitism, however, has yet to be fully integrated into research on the ecology of fear, despite it having direct negative and often lethal effects on hosts and being the most common life history strategy on the planet. this might at least be partly due to the traditional, but untested, assumption that anti-parasite responses are weak ...200918989706
toxicity of road salt to nova scotia amphibians.the deposition of chemical pollutants into roadside wetlands from runoff is a current environmental concern. in northern latitudes, a major pollutant in runoff water is salt (nacl), used as de-icing agents. in this study, 26 roadside ponds were surveyed for amphibian species richness and chloride concentration. acute toxicity tests (lc(50)) were performed on five locally common amphibian species using a range of environmentally significant nacl concentrations. field surveys indicated that spotte ...200918684543
postembryonic development of the olfactory and vomeronasal organs in the frog rana chensinensis.we studied by light microscopy the histological development of the olfactory and vomeronasal organ in tadpoles of the chinese forest frog, rana chensinensis, from postembryonic periods to the end of metamorphosis. unlike bufo americanus, the olfactory epithelium in larval r. chensinensis is not divided into dorsal and ventral branches in the rostral and mid-nasal regions. the olfactory epithelium in the dorsal portion of the buccal cavity in larval r. chensinensis may correspond to the ventral o ...200818558803
effects of timber harvesting on pond-breeding amphibian persistence: testing the evacuation hypothesis.numerous studies have documented the decline of amphibians following timber harvest. however, direct evidence concerning the mechanisms of population decline is lacking and hinders attempts to develop conservation or recovery plans and solutions for forest species. we summarized the mechanisms by which abundance of amphibians may initially decline following timber harvest into three testable hypotheses: (1) mortality, (2) retreat, and (3) evacuation. here, we tested the evacuation hypothesis wit ...200818488596
effects of temperature regime through premetamorphic ontogeny on shape of the chondrocranium in the american toad, anaxyrus americanus.if one considers the substantial amount of information that exists about phenotypic plasticity in amphibians, it is surprising that few studies have examined abiotic factors that influence phenotype through ontogeny. phenotypic change and stability of morphology are artifacts of organisms that bear significant relevance to evolution within and among taxonomic groups. here, we examine development as a phenotypically plastic aspect of larval anurans. fertilized eggs of the american toad, anaxyrus ...200818449900
variation in somatic and ovarian development: predicting susceptibility of amphibians to estrogenic contaminants.although amphibian sex determination is genetic, it can be manipulated by exogenous hormone exposure during sexual differentiation. the timing of sexual differentiation varies among anuran amphibians such that species may or may not be a tadpole during this period, and therefore, may or may not be exposed to aquatic contaminants. estrogenic contamination is present in amphibian habitats worldwide. we examined three species with varying somatic and ovarian developmental rates to assess their susc ...200818420201
examining the single and interactive effects of three insecticides on amphibian metamorphosis.although aquatic communities frequently are exposed to a number of pesticides, the effects of chemical mixtures are not well understood. in two separate studies, i examined how insecticide mixtures influenced the likelihood of unpredictable, nonadditive effects on american toad (bufo americanus) and green frog (rana clamitans) tadpoles reared in outdoor aquatic communities. i exposed tadpoles to single or multiple insecticides at approximately half the reported median lethal concentrations using ...200818260698
microcosm investigations of stormwater pond sediment toxicity to embryonic and larval amphibians: variation in sensitivity among species.stormwater ponds have become common features of modern development and often represent significant amounts of open space in urbanized areas. although stormwater ponds may provide habitat for wildlife, factors responsible for producing variation in wildlife use of ponds have received limited attention. to investigate the role of variation in species tolerances of pollutants in structuring pond-breeding amphibian assemblages, we exposed species tolerant (bufo americanus) and not tolerant (rana syl ...200818023947
helminth communities in five species of sympatric amphibians from three adjacent ephemeral ponds in southeastern wisconsin.representatives of 5 amphibian species (313 individuals), including eastern american toads (bufo americanus), wood frogs (rana sylvatica), spring peepers (pseudacris crucifer), blue-spotted salamanders (ambystoma laterale), and central newts (notophthalmus viridescens louisianensis), were collected from 3 ephemeral ponds during spring 1994, and they were inspected for helminth parasites. the component communities of anurans were more diverse than those of caudates. infracommunities of all host s ...200717918353
density dependence in the terrestrial life history stage of two anurans.populations of species with complex life cycles have the potential to be regulated at multiple life history stages. however, research tends to focus on single stage density-dependence, which can lead to inaccurate conclusions about population regulation and subsequently hinder conservation efforts. in amphibians, many studies have demonstrated strong effects of larval density and have often assumed that populations are regulated at this life history stage. however, studies examining density regu ...200717622562
amphibian embryo and parental defenses and a larval predator reduce egg mortality from water mold.water molds attack aquatic eggs worldwide and have been associated with major mortality events in some cases, but typically only in association with additional stressors. we combined field observations and laboratory experiments to study egg stage defenses against pathogenic water mold in three temperate amphibians. spotted salamanders (ambystoma maculatum) wrap their eggs in a protective jelly layer that prevents mold from reaching the embryos. wood frog (rana sylvatica) egg masses have less je ...200617089665
the tactile-stimulated startle response of tadpoles: acceleration performance and its relationship to the anatomy of wood frog (rana sylvatica), bullfrog (rana catesbeiana), and american toad (bufo americanus) tadpoles.i described the tactile-stimulated startle response (tsr) of wood frog (rana sylvatica), bullfrog (rana catesbeiana), and american toad (bufo americanus) tadpoles. one purpose was to rank species in terms of maximum acceleration performance. also, i tested whether anatomical indicators of performance potential were predictive of realized performance. tsrs were elicited in a laboratory setting, filmed at 250 hz, and digitally analyzed. tsrs began with two, initial body curls during which tadpoles ...200616493644
effects of three organic wastewater contaminants on american toad, bufo americanus, tadpoles.recent surveys of aquatic habitats suggest that organic wastewater contaminants (owcs) may be common in aquatic ecosystems. however, relatively little is known about the impacts of owcs on amphibians. we studied the lethal and sublethal effects of three owcs (acetaminophen, caffeine, and triclosan) on american toad (bufo americanus) tadpoles. high concentrations of triclosan increased activity, whereas acetaminophen had a significant effect on activity but there was no discernable pattern or tre ...200516385741
the lethal impacts of roundup and predatory stress on six species of north american tadpoles.the decline in amphibians across the globe has sparked a search for the causes, and recent evidence suggests a connection with pesticides. however, for most pesticides, tests on amphibians are rare and conducted only for short durations (1 to 4 days) and without natural stressors. recent studies have discovered that the stress of predator cues in the water can make insecticides much more lethal to larval amphibians, but it is unknown whether this phenomenon can be generalized to other types of p ...200515886853
ontogeny, phylogeny, and morphology in anuran larvae: morphometric analysis of cranial development and evolution in rana tadpoles (anura: ranidae).comparative studies of chondrocranial morphology in larval anurans are typically qualitative in nature, focusing primarily on discrete variation or gross differences in the size or shape of individual structures. detailed data on chondrocranial allometry are currently limited to only two species, rana sylvatica and bufo americanus. this study uses geometric morphometric and multivariate statistical analyses to examine interspecific variation in both larval chondrocranial shape and patterns of on ...200515688441
phylogeography of bufo fowleri at its northern range limit.many of the species that recolonized previously glaciated areas in the great lakes basin of north america over the past 10-12,000 years exhibit genetic evidence of multiple invasion routes and present-day secondary contact between deeply divergent lineages. with this in mind, we investigated the phylogeographical structure of genetic variability in fowler's toads (bufo fowleri) at the northern edge of its distribution where its range encircles the lake erie basin. because b. fowleri is so closel ...200415548286
toxicity of glyphosate-based pesticides to four north american frog species.glyphosate-based herbicides are among the most widely used pesticides in the world. we compared the acute toxicity of the glyphosate end-use formulation roundup original to four north american amphibian species (rana clamitans, r. pipiens, r. sylvatica, and bufo americanus) and the toxicity of glyphosate technical, the polyethoxylated tallowamine surfactant (poea) commonly used in glyphosate-based herbicides, and five newer glyphosate formulations to r. clamitans. for r. clamitans, acute toxicit ...200415352482
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