Publications

atelopidtoxin from the panamanian frog, atelopus zeteki.		1969	5368468
toxin from skin of frogs of the genus atelopus: differentiation from dendrobatid toxins.	a potent, dialyzable toxin (atelopidtoxin) occurs in the skin of frogs of the genus atelopus. a concentrate of atelopidtoxin from atelopus zeteki has an ld(50) in mice of 16 micrograms per kilogram. it differs from batrachotoxin, tetrodotoxin, and saxitoxin, the only known nonprotein substances of greater toxicity, as well as from all toxins previously isolated from amphibia.	1969	5807965
chemistry and pharmacology of skin toxins from the frog atelopus zeteki (atelopidtoxin: zetekitoxin).		1977	558664
semaphoring in an earless frog: the origin of a novel visual signal.	social communication in anuran amphibians (frogs and toads) is mediated predominantly by acoustic signals. unlike most anurans, the panamanian golden frog, atelopus zeteki, lacks a standard tympanic middle ear and appears to have augmented its communicatory repertoire to include rotational limb motions as visual signals, referred to here as semaphores. the communicatory nature of semaphoring was inferred from experimental manipulations using mirrored self-image presentations and nonresident intr ...	1998	24399272
the structure of zetekitoxin ab, a saxitoxin analog from the panamanian golden frog atelopus zeteki: a potent sodium-channel blocker.	bufonid anurans of the genus atelopus contain both steroidal bufadienolides and various guanidinium alkaloids of the tetrodotoxin class. the former inhibit sodium-potassium atpases, whereas the latter block voltage-dependent sodium channels. the structure of one guanidinium alkaloid, zetekitoxin ab, has remained a mystery for over 30 years. the structure of this alkaloid now has been investigated with a sample of approximately 0.3 mg, purified from extracts obtained decades ago from the panamani ...	2004	15070720
tests of phenotypic and genetic concordance and their application to the conservation of panamanian golden frogs (anura, bufonidae).	evolutionarily significant units (esus) differ in the extent to which they capture, or even consider, adaptive variation, and most such designations are based solely on neutral genetic differences that may not capture variation relevant to species' adaptabilities to changing environmental conditions. while concordant patterns of divergence among data sets (i.e. neutral and potentially non-neutral characters) can strengthen esu designations, determining whether such criteria are met for highly va ...	2007	17651191
effects of temperature and hydric environment on survival of the panamanian golden frog infected with a pathogenic chytrid fungus.	considerable controversy exists concerning whether or not climate changes (particularly global warming) are causing outbreaks of a lethal amphibian pathogen, the chytrid fungus batrachochytrium dendrobatidis (longcore, pessier & d.k. nichols 1999). in the present study, groups of panamanian golden frogs (atelopus zeteki dunn, 1993), a critically endangered amphibian thought to be nearly extinct in panama, were exposed to varying dosages of zoospores of batrachochytrium dendrobatidis, temperature ...	2010	21392332
thermoregulatory behaviour affects prevalence of chytrid fungal infection in a wild population of panamanian golden frogs.	predicting how climate change will affect disease dynamics requires an understanding of how the environment affects host-pathogen interactions. for amphibians, global declines and extinctions have been linked to a pathogenic chytrid fungus, batrachochytrium dendrobatidis. using a combination of body temperature measurements and disease assays conducted before and after the arrival of b. dendrobatidis, this study tested the hypothesis that body temperature affects the prevalence of infection in a ...	2010	19864287
towards a better understanding of the use of probiotics for preventing chytridiomycosis in panamanian golden frogs.	populations of native panamanian golden frogs (atelopus zeteki) have collapsed due to a recent chytridiomycosis epidemic. reintroduction efforts from captive assurance colonies are unlikely to be successful without the development of methods to control chytridiomycosis in the wild. in an effort to develop a protective treatment regimen, we treated golden frogs with janthinobacterium lividum, a skin bacterium that has been used to experimentally prevent chytridiomycosis in north american amphibia ...	2011	22328095
a fungal pathogen of amphibians, batrachochytrium dendrobatidis, attenuates in pathogenicity with in vitro passages.	laboratory investigations into the amphibian chytrid fungus, batrachochytrium dendrobatidis (bd), have accelerated recently, given the pathogen's role in causing the global decline and extinction of amphibians. studies in which host animals were exposed to bd have largely assumed that lab-maintained pathogen cultures retained the infective and pathogenic properties of wild isolates. attenuated pathogenicity is common in artificially maintained cultures of other pathogenic fungi, but to date, it ...	2013	24130895
clinical challenge. large and small ventral abdominal swellings in panamanian golden frogs (atelopus zeteki).		2013	23805581
fungal infection intensity and zoospore output of atelopus zeteki, a potential acute chytrid supershedder.	amphibians vary in their response to infection by the amphibian-killing chytrid fungus, batrachochytrium dendrobatidis (bd). highly susceptible species are the first to decline and/or disappear once bd arrives at a site. these competent hosts likely facilitate bd proliferation because of ineffective innate and/or acquired immune defenses. we show that atelopus zeteki, a highly susceptible species that has undergone substantial population declines throughout its range, rapidly and exponentially i ...	2014	24675899
fighting a losing battle: vigorous immune response countered by pathogen suppression of host defenses in the chytridiomycosis-susceptible frog atelopus zeteki.	the emergence of the disease chytridiomycosis caused by the chytrid fungus batrachochytrium dendrobatidis (bd) has been implicated in dramatic global amphibian declines. although many species have undergone catastrophic declines and/or extinctions, others appear to be unaffected or persist at reduced frequencies after bd outbreaks. the reasons behind this variance in disease outcomes are poorly understood: differences in host immune responses have been proposed, yet previous studies suggest a la ...	2014	24841130
composition of symbiotic bacteria predicts survival in panamanian golden frogs infected with a lethal fungus.	symbiotic microbes can dramatically impact host health and fitness, and recent research in a diversity of systems suggests that different symbiont community structures may result in distinct outcomes for the host. in amphibians, some symbiotic skin bacteria produce metabolites that inhibit the growth of batrachochytrium dendrobatidis (bd), a cutaneous fungal pathogen that has caused many amphibian population declines and extinctions. treatment with beneficial bacteria (probiotics) prevents bd in ...	2015	25788591
dead or alive? viability of chytrid zoospores shed from live amphibian hosts.	pathogens vary in virulence and rates of transmission because of many differences in the host, the pathogen, and their environment. the amphibian chytrid fungus, batrachochytrium dendrobatidis (bd), affects amphibian hosts differently, causing extinction and population declines in some species but having limited effects on others. phenotypic differences in zoospore production rates among bd lineages likely contribute to some of the variation observed among host responses, although no studies hav ...	2016	27225201
first in vivo batrachochytrium dendrobatidis transcriptomes reveal mechanisms of host exploitation, host-specific gene expression, and expressed genotype shifts.	for generalist pathogens, host species represent distinct selective environments, providing unique challenges for resource acquisition and defense from host immunity, potentially resulting in host-dependent differences in pathogen fitness. gene expression modulation should be advantageous, responding optimally to a given host and mitigating the costs of generalism. batrachochytrium dendrobatidis (bd), a fungal pathogen of amphibians, shows variability in pathogenicity among isolates, and within- ...	2017	27856699
the thermal mismatch hypothesis explains host susceptibility to an emerging infectious disease.	parasites typically have broader thermal limits than hosts, so large performance gaps between pathogens and their cold- and warm-adapted hosts should occur at relatively warm and cold temperatures, respectively. we tested this thermal mismatch hypothesis by quantifying the temperature-dependent susceptibility of cold- and warm-adapted amphibian species to the fungal pathogen batrachochytrium dendrobatidis (bd) using laboratory experiments and field prevalence estimates from 15 410 individuals in ...	2017	28111904
the pharmacokinetics of topical itraconazole in panamanian golden frogs (atelopus zeteki).	chytridiomycosis is caused by the fungus batrachochytrium dendrobatidis and is one of the primary causes of the global decline in amphibian populations and specifically of the panamanian golden frog ( atelopus zeteki ). itraconazole has been demonstrated to be an effective treatment for chytridiomycosis by inhibiting cytochrome p450, a major enzyme important for the structure of b. dendrobatidis zoospores' plasma membranes. however, anecdotal reports of toxicity in this and other amphibian speci ...	2017	28749305
effects of hormonal stimulation on the concentration and quality of excreted spermatozoa in the critically endangered panamanian golden frog (atelopus zeteki).	knowledge of basic gamete biology is critical to better protect and propagate endangered amphibian species and also to develop reproductive technologies combined with germplasm cryopreservation. the objectives of the study were to test different hormonal stimulations and then characterize the quantity and quality of panamanian golden frog (atelopus zeteki) spermatozoa. following intraperitoneal injection of the gonadotropin-releasing hormone agonist (des-gly10, d-ala6, pro-nhet9--gnrh 1, 2 or 4 ...	2017	28215683
external reinfection of a fungal pathogen does not contribute to pathogen growth.	chytridiomycosis is an emerging infectious disease of amphibians caused by the fungal pathogen batrachochytrium dendrobatidis (bd), which has led to devastating declines in amphibian populations worldwide. current theory predicts that bd infections are maintained through both reproduction on the host's skin and reinfection from sources outside of the host. to investigate the importance of external reinfection on pathogen burden, we infected captive-bred individuals of the highly susceptible pana ...	2018	30128614
causes of mortality in captive panamanian golden frogs ( atelopus zeteki) at the maryland zoo in baltimore, 2001-2013.	the maryland zoo in baltimore is home to the largest captive assurance population of the critically endangered panamanian golden frog ( atelopus zeteki). with the ongoing extinction that is occurring worldwide in amphibians, the need for amphibian captive assurance populations is growing, and few mortality reviews on amphibian species exist. necropsy and histopathologic examination of animals that die in captivity can help identify population-level disease problems, direct research needs in amph ...	2018	29900781
influence of extracellular environment on the motility and structural properties of spermatozoa collected from hormonally stimulated panamanian golden frog (atelopus zeteki).	a better understanding of the factors influencing the biology of amphibian spermatozoa after release from the testis is a prerequisite to the development of sperm preservation methods. the objective of the study was to determine the effect of extracellular conditions (exposure to water and different temperatures) over time on the sperm motility and structural properties (including morphology and dna integrity) collected from hormonally stimulated atelopus zeteki. following intraperitoneal inject ...	2018	29216539
ophthalmic findings in a captive population of panamanian golden frogs: atelopus zeteki.	the aim of this study was to describe normal ocular morphology and establish parameters for select diagnostics in a population of panamanian golden frogs (pgf) atelopus zeteki maintained at the detroit zoo.	2019	30701662
an interaction between climate change and infectious disease drove widespread amphibian declines.	climate change might drive species declines by altering species interactions, such as host-parasite interactions. however, few studies have combined experiments, field data, and historical climate records to provide evidence that an interaction between climate change and disease caused any host declines. a recently proposed hypothesis, the thermal mismatch hypothesis, could identify host species that are vulnerable to disease under climate change because it predicts that cool- and warm-adapted h ...	2019	30484936
whole exome sequencing identifies the potential for genetic rescue in iconic and critically endangered panamanian harlequin frogs.	avoiding extinction in a rapidly changing environment often relies on a species' ability to quickly adapt in the face of extreme selective pressures. in panamá, two closely related harlequin frog species (atelopus varius and atelopus zeteki) are threatened with extinction due to the fungal pathogen batrachochytrium dendrobatidis (bd). once thought to be nearly extirpated from panamá, a. varius have recently been rediscovered in multiple localities across their historical range; however, a. zetek ...	2020	33150627