Download or read book The Ecology of Chytridiomycosis in Red legged Frog Rana Aurora Tadpoles written by Phineas Hamilton and published by . This book was released on 2010 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chytridiomycosis is an emerging infectious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Chytridiomycosis has caused declines and extinctions of amphibian species worldwide. Although the disease can be highly virulent, there are large differences both within and between amphibian species in response to Bd-infection. Environmental factors are increasingly shown to be critical in the outcome of Bd-infection and emergence of the disease, although these factors remain poorly defined. Using a series of mesocosm experiments, I examine the influence of different environmental and ecological factors on the outcome of exposure to Bd in red-leggedfrog (Rana aurora) tadpoles, a species in decline in British Columbia. First, I tested the hypothesis that Daphnia, a keystone genus of zooplankton in shallow freshwater ecosystems, consume Bd zoospores in the water column to decrease the transmission of Bd infection in tadpoles. Although Daphnia are nearly always included in amphibian mesocosm experiments, their effects in these systems are overlooked. As such, I also examined the effect of Daphnia on R. aurora in general. I found that Daphnia had dramatic beneficial effects on tadpoles, that ostensibly herbivorous tadpoles consumed large numbers of Daphnia, and that Daphnia interacted with the presence of Bd to influence tadpole survival, with tadpole survival highest in the absence of Bd and presence of Daphnia. Although Daphnia consumed Bd zoospores in the laboratory, they had no discernible effect on transmission in mesocosms. These results have broad implications for the interpretation of mesocosm studies in general. Climate change has been implicated as a trigger of outbreaks of chytridiomycosis, yet, paradoxically, high temperatures are lethal to Bd. Climate change has also impacted amphibian communities by uncoupling the phenology of interacting species. I manipulated the temperature in mesocosms to test the effects of small temperature changes on the outcome of Bd-exposure in R. aurora. I also tested the effect of the presence of the sympatric Boreal chorus frog (Pseudacris regilla) on R. aurora at different temperatures, and in the presence and absence of Bd. I found that negative effects of Bd on tadpole body condition increased with temperature, although when Bd was absent tadpoles benefitted at higher temperatures. Furthermore, both Bd and temperature increased the development rates of P. regilla but not R. aurora, uncoupling the phenology of the species. Increased temperatures thus favoured P. regilla at the expense of R. aurora. In general, slightly higher and more variable temperatures shifted the host-pathogen balance to the detriment of the R. aurora, helping to explain a mechanism by which increasing temperatures may trigger chytridiomycosis outbreaks in susceptible. Together, these experiments clearly demonstrated the importance of ecological context in the outcome of Bd exposure in tadpoles.
Download or read book The Ecology of Chytridiomycosis in Red legged Frog Rana Aurora Tadpoles written by Phineas T. Hamilton and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chytridiomycosis is an emerging infectious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Chytridiomycosis has caused declines and extinctions of amphibian species worldwide. Although the disease can be highly virulent, there are large differences both within and between amphibian species in response to Bd-infection. Environmental factors are increasingly shown to be critical in the outcome of Bd-infection and emergence of the disease, although these factors remain poorly defined. Using a series of mesocosm experiments, I examine the influence of different environmental and ecological factors on the outcome of exposure to Bd in red-leggedfrog (Rana aurora) tadpoles, a species in decline in British Columbia. First, I tested the hypothesis that Daphnia, a keystone genus of zooplankton in shallow freshwater ecosystems, consume Bd zoospores in the water column to decrease the transmission of Bd infection in tadpoles. Although Daphnia are nearly always included in amphibian mesocosm experiments, their effects in these systems are overlooked. As such, I also examined the effect of Daphnia on R. aurora in general. I found that Daphnia had dramatic beneficial effects on tadpoles, that ostensibly herbivorous tadpoles consumed large numbers of Daphnia, and that Daphnia interacted with the presence of Bd to influence tadpole survival, with tadpole survival highest in the absence of Bd and presence of Daphnia. Although Daphnia consumed Bd zoospores in the laboratory, they had no discernible effect on transmission in mesocosms. These results have broad implications for the interpretation of mesocosm studies in general. Climate change has been implicated as a trigger of outbreaks of chytridiomycosis, yet, paradoxically, high temperatures are lethal to Bd. Climate change has also impacted amphibian communities by uncoupling the phenology of interacting species. I manipulated the temperature in mesocosms to test the effects of small temperature changes on the outcome of Bd-exposure in R. aurora. I also tested the effect of the presence of the sympatric Boreal chorus frog (Pseudacris regilla) on R. aurora at different temperatures, and in the presence and absence of Bd. I found that negative effects of Bd on tadpole body condition increased with temperature, although when Bd was absent tadpoles benefitted at higher temperatures. Furthermore, both Bd and temperature increased the development rates of P. regilla but not R. aurora, uncoupling the phenology of the species. Increased temperatures thus favoured P. regilla at the expense of R. aurora. In general, slightly higher and more variable temperatures shifted the host-pathogen balance to the detriment of the R. aurora, helping to explain a mechanism by which increasing temperatures may trigger chytridiomycosis outbreaks in susceptible. Together, these experiments clearly demonstrated the importance of ecological context in the outcome of Bd exposure in tadpoles.
Download or read book Prevalence of Chytridiomycosis in Red legged Frog Rana Aurora Aurora Larvae in and Around Redwood National Park Northern Coastal California with Notes on Other Parasites written by Nathan C. Nieto and published by . This book was released on 2004 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Mortality in a Population of Tadpoles of the Red legged Frog Rana Aurora written by George Waller Calef and published by . This book was released on 1971 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Conservation of California Red legged Frogs written by Antonia J. D'Amore and published by . This book was released on 2007 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Growth and Viability of the Red legged Frogs Rana Aurora Introduced in the Reed College Canyon written by Xeno Acharya and published by . This book was released on 2008 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Batrachochytrium Dendrobatidis Prevalence in Northern Red legged Frogs Rana Aurora written by Michael Cheng Sun and published by . This book was released on 2012 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Analysis of Mortality in a Population of Tadpoles of the Red legged Frog Rana Aurora microform written by George W. (George Waller) Calef and published by National Library of Canada. This book was released on 1971 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Multiple Stressors written by Lindsey L. Gordon and published by . This book was released on 2020 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: As human activities reach every corner of the globe, climate change, invasive species, habitat destruction, and other stressors causing species’ declines no longer act alone. Climate change has the potential to exacerbate (or mitigate) other stressors (e.g. invasive species or pathogens) affecting amphibian populations. I assessed the combined effects of increased pond drying rates (potential impact of climate change), invasive bullfrogs (Lithobates catesbeianus) presence, and food availability on northern red-legged frog (Rana aurora) survival and body size after metamorphosis by rearing tadpoles under incrementally shortened hydroperiods with and without the presence of invasive bullfrog tadpoles in low and high food environments. To explore the underlying mechanisms driving the impact of bullfrogs on R. aurora tadpoles, I had two treatments where bullfrog tadpoles were either separated by a permeable barrier (behavioral cue) or free to move about the tanks (direct competition/predation). To validate the captive experiment, I examined the influence of hydroperiod length on R. aurora survival, development, and growth in a field-based mesocosm experiment. I found hydroperiod to have a threshold effect on survival through metamorphosis in the captive experiment. Once the hydroperiod threshold was met in both the captive and field study, I found no benefit of longer hydroperiods on survival through metamorphosis. Drying rate influenced R. aurora developmental rates, but the effects were dependent on life stage and time of season in the field study. Size at metamorphosis was synergistically affected by bullfrog presence and food availability in the captive experiment. Tadpoles emerged as smaller metamorphs when exposed to bullfrogs in a low food environment. In the field experiment, size at metamorphosis was positively affected by longer hydroperiod and later emergence date. Understanding how multiple stressors impact larval growth and survival is an important component for managing and potentially mitigating the interactive effects of climate change and invasive species for amphibian conservation.
Download or read book Disentangling the Biotic and Abiotic Drivers of the Amphibian Disease Chytridiomycosis written by Paul William Bradley and published by . This book was released on 2015 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ongoing worldwide loss of biodiversity has been described as a "biodiversity crisis," "the Anthropocene defaunation," and alternatively "an extinction spasm." More recently, many scientists have come to the conclusion that we are witnesses to Earth's sixth major mass extinction event, which has the potential to fundamentally alter basic ecological functions on global scale. One of the many causes of population declines, species extirpations, and extinctions contributing to this profound loss of biodiversity are emerging infectious diseases. The occurrence and spread of infectious diseases can be assisted by numerous anthropogenic causes. For example, habitat fragmentation and access to formerly undeveloped areas can increase the rate and the risk of interaction between domestic and wild animals, leading to "spill-over" of pathogens from unaffected reservoir hosts to susceptible hosts. Alternatively, global trade can lead to "pathogen pollution" caused by the translocation of pathogens or parasites directly or via the translocation of invasive species that often act as reservoir hosts in invaded ranges. Moreover, an overall increase in animal stress associated with habitat degradation, invasive species, or climate change can negatively affect the immune responses of an otherwise healthy host, which can transform benign infections into pathogenic infections. One emerging infectious disease that is in part responsible for this great loss of biodiversity is chytridiomycosis, which has been associated with numerous amphibian population declines and extinctions. Chytridiomycosis is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), which has been found on every continent where amphibians exist. Whereas Bd can infect a wide range of amphibians, there is also a wide range of heterogeneity of responses to infection. This heterogeneity exists at the species-level where some species can act as unaffected reservoirs of the disease; while at the other end of the spectrum, some species will die within days of exposure. This heterogeneity can exist at the population-level within a species; some populations survive with a persistent infection, while simultaneously mass mortality events can eliminate nearby populations of the same species. Furthermore, heterogeneity can exist within one population, where some amphibian life stages, or some individuals of the same life stage, survive after Bd-exposure while other life stages or individuals will not survive. Understanding the biotic and abiotic causes, of different responses to Bd is paramount to limiting further losses of amphibian biodiversity as well cascade effects of the loss of amphibians in ecosystems. This thesis elucidates some of the potential causes of these differences, specifically addressing heterogeneity among host species, host populations, host ages, and environmental temperature, a key environmental component that influences the biology of Bd. Previous studies have investigated the relationship between climate and chytridiomycosis by comparing differences susceptibility or sensitivity as a function of mean temperature over time. However, in addition to the predicted general warming trends associated with anthropogenic climate change, many models also predict increases in both the magnitude and frequency of extreme weather events, which can result in unusual temperature shifts for a given habitat. In Chapter 2, I describe an experiment in which I investigated how temperature shifts may influence Bd infection intensity and survival in amphibian larvae. Consistent with the "lag effect" hypothesis, Bd abundance was higher in larval red legged frogs (Rana aurora) that experienced a shift in temperature from cold to warm compared to frogs exposed to a constant temperature. Similarly, Bd abundance was lower in larval western toads (Anaxyrus boreas) that experienced a shift in temperature from warm to cold, compared to larval toads exposed to a constant temperature. In Chapter 3, I discuss the ontogeny of susceptibility to Bd infection and report on an experiment I performed in two species of frog over the first nine months post-metamorphosis. The youngest frogs of both species were the least susceptible to chytridiomycosis. Increasing age was associated with an increase in likelihood of Bd infection, increased infection intensity, and increased risk of mortality after infection. In Chapter 4, I examine differences in response to Bd infection among 10 distinct populations, using wood frogs (Lithobates sylvaticus) collected as eggs and raised in a common garden environment through metamorphosis. I observed differences in survival after Bd-exposure among the populations, but did not observe differences in infection intensity among populations. These results suggest that populations of wood frog share a similar level of resistance to Bd infection, but differ in levels of tolerance to infection of a given intensity. This thesis describes and helps disentangle the biotic drivers (the ontogeny of susceptibility and population-level variation in susceptibly) and a key abiotic parameter (temperature) of chytridiomycosis in amphibians. The information provided may assist conservationists and population managers to focus conservation efforts and mitigate the losses of these ecologically important creatures caused by this disease.
Download or read book Post breeding Movements and Habitat Use by the Northern Red legged Frog Rana Aurora Aurora at Dempsey Creek Thurston County Washington written by Jennifer Tuesday Serra Shean and published by . This book was released on 2002 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Analysis of Mortality in a Population of Tadpoles of the Red legged Frog Rana Aurora microfilm written by George Waller Calef and published by . This book was released on 1972 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Red legged Frog Rana Aurora written by British Columbia. Ministry of Environment, Lands, and Parks and published by . This book was released on 1985 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Influence of Canopy Cover and Climate on Early Life stage Vital Rates for Northern Red legged Frogs Rana Aurora and the Implications for Population Growth Rates written by Kecly W. McHarry and published by . This book was released on 2017 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many amphibian species are in decline due to habitat loss and changing climates. Understanding how habitat characteristics and climate influence vital rates, and if they act in concert or in opposition can inform management decisions. This study investigated the potential interaction of canopy cover and climate on early stage vital rates of northern red-legged frogs. Demographic data were collected from sample populations in experimental canopy cover treatments across a latitudinal distribution. Rearing cages were used to estimate hatch success, and mark-recapture surveys to estimate tadpole survival. Ambient air temperature was used as an index of climate because it is easily relatable to the effects of climate change and collected at fine scales without specialized equipment. Estimates from field data, along with published accounts were used in a matrix modeling analysis to evaluate if tadpole survival impacted population growth rates. Egg hatch success did not differ between canopy treatments or among sites. Canopy cover did affect tadpole survival rates, but not tadpole development time. The effect of canopy over on tadpole survival varied depending on which population was being evaluated. There was no evidence that the effect of canopy cover on tadpole survival was dependent on air temperature. Tadpole survival rates did impact population growth rates. This research shows that the effect of canopy cover on early stage vital rates for this species is variable between populations, but not due to differences in average air temperatures. For some populations the effect of canopy cover on tadpole survival was large enough to change projected population growth rates from stable to decreases of 30%. These results demonstrate that manipulating canopy cover can influence tadpole survival sufficiently enough to alter population trajectories. However, the variable effects of canopy cover on vital rates suggest a universal management strategy through canopy cover manipulation will not have equal impacts across populations.
Download or read book Final Report of the Status of the California Red legged Frog Rana Aurora Draytonii in the Pescadero Marsh Natural Preserve written by Mark R. Jennings and published by . This book was released on 1990 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies on the Structure and Life history of Ostiolum Oxyorchis Ingles from the California Red legged Frog Rana Aurora Draytoni written by Lloyd Glenn Ingles and published by . This book was released on 1933 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Body Size on the Survival and Timing of Emigration of Newly Metamorphosed Northern Red legged Frogs written by Nathan D. Chelgren and published by . This book was released on 2003 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study was to investigate the survival and movements of newly metamorphosed Northern Red-legged frogs (Rana aurora aurora) as they emigrated from two ephemeral breeding ponds. Quantifying survival and movement rates will be important to our understanding how changes to terrestrial and aquatic systems affect behavior and population dynamics. I manipulated food availability for a subset of uniquely marked metamorphic frogs and then analyzed temporal and spatial aspects of their recapture in forest pitfall traps relative to body size and date of metamorphosis. The probability of surviving and emigrating increased strongly with increasing body size and declined for frogs metamorphosing later in the season. Larger body size was associated with earlier emigration and greater correlation of movements with rainfall events. Within a pond, the time elapsed between metamorphosis and emigration was not affected by the pond drying. My results demonstrate that conditions during the tadpole stage which affect body size and the timing of metamorphosis may have a dramatic impact on the performance of frogs during their initial transition into the terrestrial environment.
