1
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Belasen AM, Peek RA, Adams AJ, Russell ID, De León ME, Adams MJ, Bettaso J, Breedveld KGH, Catenazzi A, Dillingham CP, Grear DA, Halstead BJ, Johnson PG, Kleeman PM, Koo MS, Koppl CW, Lauder JD, Padgett-Flohr G, Piovia-Scott J, Pope KL, Vredenburg V, Westphal M, Wiseman K, Kupferberg SJ. Chytrid infections exhibit historical spread and contemporary seasonality in a declining stream-breeding frog. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231270. [PMID: 38298390 PMCID: PMC10827429 DOI: 10.1098/rsos.231270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 12/18/2023] [Indexed: 02/02/2024]
Abstract
Species with extensive geographical ranges pose special challenges to assessing drivers of wildlife disease, necessitating collaborative and large-scale analyses. The imperilled foothill yellow-legged frog (Rana boylii) inhabits a wide geographical range and variable conditions in rivers of California and Oregon (USA), and is considered threatened by the pathogen Batrachochytrium dendrobatidis (Bd). To assess drivers of Bd infections over time and space, we compiled over 2000 datapoints from R. boylii museum specimens (collected 1897-2005) and field samples (2005-2021) spanning 9° of latitude. We observed a south-to-north spread of Bd detections beginning in the 1940s and increase in prevalence from the 1940s to 1970s, coinciding with extirpation from southern latitudes. We detected eight high-prevalence geographical clusters through time that span the species' geographical range. Field-sampled male R. boylii exhibited the highest prevalence, and juveniles sampled in autumn exhibited the highest loads. Bd infection risk was highest in lower elevation rain-dominated watersheds, and with cool temperatures and low stream-flow conditions at the end of the dry season. Through a holistic assessment of relationships between infection risk, geographical context and time, we identify the locations and time periods where Bd mitigation and monitoring will be critical for conservation of this imperilled species.
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Affiliation(s)
- A. M. Belasen
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
| | - R. A. Peek
- California Department of Fish and Wildlife, West Sacramento, CA, USA
| | - A. J. Adams
- Earth Research Institute, University of California, Santa Barbara, CA, USA
| | - I. D. Russell
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
| | - M. E. De León
- Genome Center, University of California, Davis, CA, USA
| | - M. J. Adams
- U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, USA
| | - J. Bettaso
- Six Rivers National Forest, Lower Trinity Ranger District, USDA Forest Service, P.O. Box 68, Willow Creek, CA, USA
| | | | - A. Catenazzi
- Department of Biological Sciences, Florida International University, Miami, FL, USA
| | | | - D. A. Grear
- U.S. Geological Survey, National Wildlife Health Center, Madison, WI, USA
| | - B. J. Halstead
- Point Reyes Field Station, U.S. Geological Survey, Western Ecological Research Center, Point Reyes Station, CA, USA
| | - P. G. Johnson
- Pinnacles National Park, National Park Service, Paicines, CA, USA
| | - P. M. Kleeman
- Point Reyes Field Station, U.S. Geological Survey, Western Ecological Research Center, Point Reyes Station, CA, USA
| | - M. S. Koo
- Museum of Vertebrate Zoology, University of California, Berkeley, CA
| | - C. W. Koppl
- Plumas National Forest, USDA Forest Service, Quincy, CA, USA
| | | | | | - J. Piovia-Scott
- School of Biological Sciences, Washington State University, Vancouver, WA, USA
| | - K. L. Pope
- Pacific Southwest Research Station, USDA Forest Service, Arcata, CA, USA
| | - V. Vredenburg
- Department of Biology, San Francisco State University, San Francisco, CA, USA
| | - M. Westphal
- Central Coast Field Office, United States Bureau of Land Management, Marina, CA, USA
| | - K. Wiseman
- Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
| | - S. J. Kupferberg
- Department of Integrative Biology, University of California, Berkeley, CA, USA
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2
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Pereira KE, Bletz MC, McCartney JA, Woodhams DC, Woodley SK. Effects of exogenous elevation of corticosterone on immunity and the skin microbiome of eastern newts ( Notophthalmus viridescens). Philos Trans R Soc Lond B Biol Sci 2023; 378:20220120. [PMID: 37305906 PMCID: PMC10258667 DOI: 10.1098/rstb.2022.0120] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 12/15/2022] [Indexed: 06/13/2023] Open
Abstract
The amphibian chytrid fungus, Batrachochytrium salamandrivorans (Bsal) threatens salamander biodiversity. The factors underlying Bsal susceptibility may include glucocorticoid hormones (GCs). The effects of GCs on immunity and disease susceptibility are well studied in mammals, but less is known in other groups, including salamanders. We used Notophthalmus viridescens (eastern newts) to test the hypothesis that GCs modulate salamander immunity. We first determined the dose required to elevate corticosterone (CORT; primary GC in amphibians) to physiologically relevant levels. We then measured immunity (neutrophil lymphocyte ratios, plasma bacterial killing ability (BKA), skin microbiome, splenocytes, melanomacrophage centres (MMCs)) and overall health in newts following treatment with CORT or an oil vehicle control. Treatments were repeated for a short (two treatments over 5 days) or long (18 treatments over 26 days) time period. Contrary to our predictions, most immune and health parameters were similar for CORT and oil-treated newts. Surprisingly, differences in BKA, skin microbiome and MMCs were observed between newts subjected to short- and long-term treatments, regardless of treatment type (CORT, oil vehicle). Taken together, CORT does not appear to be a major factor contributing to immunity in eastern newts, although more studies examining additional immune factors are necessary. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
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Affiliation(s)
- Kenzie E. Pereira
- Department of Biology, Duquesne University, Pittsburgh, PA 15282, USA
| | - Molly C. Bletz
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Julia A. McCartney
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Douglas C. Woodhams
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Sarah K. Woodley
- Department of Biology, Duquesne University, Pittsburgh, PA 15282, USA
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3
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Wu NC. Pathogen load predicts host functional disruption: A meta‐analysis of an amphibian fungal panzootic. Funct Ecol 2023. [DOI: 10.1111/1365-2435.14245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Nicholas C. Wu
- Hawkesbury Institute for the Environment Western Sydney University Richmond New South Wales Australia
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4
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Humphries JE, Lanctôt CM, Robert J, McCallum HI, Newell DA, Grogan LF. Do immune system changes at metamorphosis predict vulnerability to chytridiomycosis? An update. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2022; 136:104510. [PMID: 35985564 DOI: 10.1016/j.dci.2022.104510] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 06/20/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
Amphibians are among the vertebrate groups suffering great losses of biodiversity due to a variety of causes including diseases, such as chytridiomycosis (caused by the fungal pathogens Batrachochytrium dendrobatidis and B. salamandrivorans). The amphibian metamorphic period has been identified as being particularly vulnerable to chytridiomycosis, with dramatic physiological and immunological reorganisation likely contributing to this vulnerability. Here, we overview the processes behind these changes at metamorphosis and then perform a systematic literature review to capture the breadth of empirical research performed over the last two decades on the metamorphic immune response. We found that few studies focused specifically on the immune response during the peri-metamorphic stages of amphibian development and fewer still on the implications of their findings with respect to chytridiomycosis. We recommend future studies consider components of the immune system that are currently under-represented in the literature on amphibian metamorphosis, particularly pathogen recognition pathways. Although logistically challenging, we suggest varying the timing of exposure to Bd across metamorphosis to examine the relative importance of pathogen evasion, suppression or dysregulation of the immune system. We also suggest elucidating the underlying mechanisms of the increased susceptibility to chytridiomycosis at metamorphosis and the associated implications for population persistence. For species that overlap a distribution where Bd/Bsal are now endemic, we recommend a greater focus on management strategies that consider the important peri-metamorphic period.
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Affiliation(s)
- Josephine E Humphries
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland, 4222, Australia; Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, 2480, Australia.
| | - Chantal M Lanctôt
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Australian Rivers Institute, Griffith University, Southport, Queensland, 4222, Australia
| | - Jacques Robert
- Department of Microbiology and Immunology, University of Rochester Medical Center, 14642, Rochester, NY, United States
| | - Hamish I McCallum
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland, 4222, Australia
| | - David A Newell
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, 2480, Australia
| | - Laura F Grogan
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland, 4222, Australia
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5
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Silver LW, Cheng Y, Quigley BL, Robbins A, Timms P, Hogg CJ, Belov K. A targeted approach to investigating immune genes of an iconic Australian marsupial. Mol Ecol 2022; 31:3286-3303. [PMID: 35510793 PMCID: PMC9325493 DOI: 10.1111/mec.16493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 03/02/2022] [Accepted: 04/05/2022] [Indexed: 11/30/2022]
Abstract
Disease is a contributing factor to the decline of wildlife populations across the globe. Koalas, iconic yet declining Australian marsupials, are predominantly impacted by two pathogens, Chlamydia and koala retrovirus. Chlamydia is an obligate intracellular bacterium and one of the most widespread sexually transmitted infections in humans worldwide. In koalas, Chlamydia infections can present as asymptomatic or can cause a range of ocular and urogenital disease signs, such as conjunctivitis, cystitis and infertility. In this study, we looked at differences in response to Chlamydia in two northern populations of koalas using a targeted gene sequencing of 1209 immune genes in addition to genome‐wide reduced representation data. We identified two MHC Class I genes associated with Chlamydia disease progression as well as 25 single nucleotide polymorphisms across 17 genes that were associated with resolution of Chlamydia infection. These genes are involved in the innate immune response (TLR5) and defence (TLR5, IFNγ, SERPINE1, STAT2 and STX4). This study deepens our understanding of the role that genetics plays in disease progression in koalas and leads into future work that will use whole genome resequencing of a larger sample set to investigate in greater detail regions identified in this study. Elucidation of the role of host genetics in disease progression and resolution in koalas will directly contribute to better design of Chlamydia vaccines and management of koala populations which have recently been listed as “endangered.”
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Affiliation(s)
- Luke W Silver
- School of Life and Environmental Sciences, The University of Sydney, New South Wales, 2006, Australia
| | - Yuanyuan Cheng
- School of Life and Environmental Sciences, The University of Sydney, New South Wales, 2006, Australia
| | - Bonnie L Quigley
- Genecology Research Centre, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4556, Australia.,Provectus Algae Pty Ltd, 5 Bartlett Road, Noosaville, Queensland, 4566, Australia
| | - Amy Robbins
- Genecology Research Centre, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4556, Australia.,Endeavour Veterinary Ecology Pty Ltd, 1695 Pumicestone Road, Toorbul, Queensland, 4510, Australia
| | - Peter Timms
- Genecology Research Centre, University of the Sunshine Coast, 90 Sippy Downs Drive, Sippy Downs, Queensland, 4556, Australia
| | - Carolyn J Hogg
- School of Life and Environmental Sciences, The University of Sydney, New South Wales, 2006, Australia
| | - Katherine Belov
- School of Life and Environmental Sciences, The University of Sydney, New South Wales, 2006, Australia
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6
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Rumschlag SL, Roth SA, McMahon TA, Rohr JR, Civitello DJ. Variability in environmental persistence but not per capita transmission rates of the amphibian chytrid fungus leads to differences in host infection prevalence. J Anim Ecol 2021; 91:170-181. [PMID: 34668575 DOI: 10.1111/1365-2656.13612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 09/27/2021] [Indexed: 11/28/2022]
Abstract
Heterogeneities in infections among host populations may arise through differences in environmental conditions through two mechanisms. First, environmental conditions may alter host exposure to pathogens via effects on survival. Second, environmental conditions may alter host susceptibility, making infection more or less likely if contact between a host and pathogen occurs. Further, host susceptibility might be altered through acquired resistance, which hosts can develop, in some systems, through exposure to dead or decaying pathogens and their metabolites. Environmental conditions may alter the rates of pathogen decomposition, influencing the likelihood of hosts developing acquired resistance. The present study primarily tests how environmental context influences the relative contributions of pathogen survival and per capita transmission on host infection prevalence using the amphibian chytrid fungus (Batrachochytrium dendrobatidis; Bd) as a model system. Secondarily, we evaluate how environmental context influences the decomposition of Bd because previous studies have shown that dead Bd and its metabolites can illicit acquired resistance in hosts. We conducted Bd survival and infection experiments and then fit models to discern how Bd mortality, decomposition and per capita transmission rates vary among water sources [e.g. artificial spring water (ASW) or water from three ponds]. We found that infection prevalence differed among water sources, which was driven by differences in mortality rates of Bd, rather than differences in per capita transmission rates. Bd mortality rates varied among pond water treatments and were lower in ASW compared to pond water. These results suggest that variation in Bd infection dynamics could be a function of environmental factors in waterbodies that result in differences in exposure of hosts to live Bd. In contrast to the persistence of live Bd, we found that the rates of decomposition of dead Bd did not vary among water sources, which may suggest that exposure of hosts to dead Bd or its metabolites might not commonly vary among nearby sites. Ultimately, a mechanistic understanding of the environmental dependence of free-living pathogens could lead to a deeper understanding of the patterns of outbreak heterogeneity, which could inform surveillance and management strategies.
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Affiliation(s)
- Samantha L Rumschlag
- Department of Biological Sciences, Environmental Change Initiative, and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA.,Department of Integrative Biology, University of South Florida, Tampa, FL, USA
| | - Sadie A Roth
- Department of Integrative Biology, University of South Florida, Tampa, FL, USA.,Department of Natural Resources Management, Texas Tech University, Lubbock, TX, USA
| | - Taegan A McMahon
- Department of Biology, University of Tampa, Tampa, FL, USA.,Department of Biology, Connecticut College, New London, CT, USA
| | - Jason R Rohr
- Department of Biological Sciences, Environmental Change Initiative, and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA.,Department of Integrative Biology, University of South Florida, Tampa, FL, USA
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7
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Terrell KA, Quintero RP, Galicia VA, Bronikowski E, Evans M, Kleopfer JD, Murray S, Murphy JB, Nissen BD, Gratwicke B. Physiological impacts of temperature variability and climate warming in hellbenders ( Cryptobranchus alleganiensis). CONSERVATION PHYSIOLOGY 2021; 9:coab079. [PMID: 36118128 PMCID: PMC8445510 DOI: 10.1093/conphys/coab079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 08/10/2021] [Accepted: 09/11/2021] [Indexed: 06/15/2023]
Abstract
Cold-adapted hellbender salamanders that inhabit cool mountain streams are expected to fare poorly under warmer projected climate scenarios. This study investigated the physiological consequences of long-term, naturalistic temperature variation on juvenile hellbenders under simulated current and warmer (+1.6 C) climates vs. controlled steady temperatures. Mean temperature and temperature variability were both important predictors of growth as indicated by monthly body mass change (%), stress as indicated by neutrophil:lymphocyte (N:L) ratio and bacteria-killing ability of blood. Cold exposure in hellbenders was associated with weight loss, increased N:L ratios and reduced Escherichia coli killing ability of blood, and these effects were less pronounced under a warmer climate scenario. These observations suggest that cold periods may be more stressful for hellbenders than previously understood. Growth rates peaked in late spring and late fall around 14-17°C. Hellbenders experiencing warmer simulated climates retained body condition better in winter, but this was counter-balanced by a prolonged lack of growth in the 3-month summer period leading up to the fall breeding season where warmer simulated conditions resulted in an average loss of -0.6% body mass/month, compared to a gain +1.5% body mass/month under current climate scenario. Hellbenders can physiologically tolerate projected warmer temperatures and temperature fluctuations, but warmer summers may cause animals to enter the fall breeding season with a caloric deficit that may have population-level consequences.
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Affiliation(s)
- Kimberly A Terrell
- Center for Species Survival, Smithsonian Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
- Tulane Environmental Law Clinic, 6329 Freret St, New Orleans, LA 70118, USA
| | - Richard P Quintero
- Center for Animal Care Sciences, Reptile Discovery Center, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
| | - Veronica Acosta Galicia
- Center for Animal Care Sciences, Reptile Discovery Center, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
| | - Ed Bronikowski
- Center for Animal Care Sciences, Reptile Discovery Center, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
| | - Matthew Evans
- Center for Animal Care Sciences, Reptile Discovery Center, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
| | - John D Kleopfer
- Virginia Department of Wildlife Resources, 3801 John Tyler Hwy, Charles City, VA 23030
| | - Suzan Murray
- Center for Animal Care Sciences, Reptile Discovery Center, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
| | - James B Murphy
- Center for Animal Care Sciences, Reptile Discovery Center, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
| | - Bradley D Nissen
- Center for Animal Care Sciences, Reptile Discovery Center, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
| | - Brian Gratwicke
- Center for Species Survival, Smithsonian Conservation Biology Institute, National Zoological Park, 3001 Connecticut Ave. NW, Washington, DC 20008, USA
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8
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Siddons SR, Searle CL. Exposure to a fungal pathogen increases the critical thermal minimum of two frog species. Ecol Evol 2021; 11:9589-9598. [PMID: 34306645 PMCID: PMC8293773 DOI: 10.1002/ece3.7779] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 05/14/2021] [Accepted: 05/19/2021] [Indexed: 11/12/2022] Open
Abstract
The ability of an organism to tolerate seasonal temperature changes, such as extremely cold temperatures during the winter, can be influenced by their pathogens. We tested how exposure to a virulent fungal pathogen, Batrachochytrium dendrobatidis (Bd), affected the critical thermal minimum (CTmin) of two frog species, Hyla versicolor (gray treefrog) and Lithobates palustris (pickerel frog). The CTmin is the minimum thermal performance point of an organism, which we estimated via righting response trials. For both frog species, we compared the righting response of Bd-exposed and Bd-unexposed individuals in either a constant (15ºC) environment or with decreasing temperatures (-1°C/2.5 min) starting from 15°C. The CTmin for both species was higher for Bd-exposed frogs than unexposed frogs, and the CTmin of H. versicolor was higher than L. palustris. We also found that Bd-exposed frogs of both species righted themselves significantly fewer times in both decreasing and constant temperature trials. Our findings show that pathogen exposure can reduce cold tolerance and limit the thermal performance range of hosts, which may lead to increased overwintering mortality.
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9
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Challenges of a novel range: Water balance, stress, and immunity in an invasive toad. Comp Biochem Physiol A Mol Integr Physiol 2020; 253:110870. [PMID: 33321177 DOI: 10.1016/j.cbpa.2020.110870] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 12/08/2020] [Accepted: 12/08/2020] [Indexed: 11/22/2022]
Abstract
Species introduced by human activities can alter the normal functioning of ecosystems promoting negative impacts on native biodiversity, as they can rapidly expand their population size, demonstrating phenotypic plasticity and possible adaptive capacity to novel environments. Twenty years ago, the guttural toad, Sclerophrys gutturalis, was introduced to a peri-urban area of Cape Town, with cooler and drier climatic characteristics than its native source population, Durban, South Africa. Our goal was to understand the phenotypic changes, in terms of physiology and immunity, of populations in native and novel environments. We evaluated body index (BI), field hydration level, plasma corticosterone levels (CORT), proportion of neutrophils: lymphocytes (N: L), plasma bacterial killing ability (BKA), and hematocrit (HTC) in the field, and after standardized stressors (dehydration and movement restriction) in males from the native and invasive populations. Toads from the invasive population presented lower BI and tended to show a lower field hydration state, which is consistent with living in the drier environmental conditions of Cape Town. Additionally, invasive toads also showed higher BKA and N:L ratio under field conditions. After exposure to stressors, invasive animals presented higher BKA than the natives. Individuals from both populations showed increased CORT after dehydration, an intense stressor for these animals. The highest BKA and N:L ratio in the field and after submission to stressors in the laboratory shows that the invasive population has a phenotype that might increase their fitness, leading to adaptive responses in the novel environment and, thus, favoring successful dispersion and population increase.
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10
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Rodriguez KM, Voyles J. The amphibian complement system and chytridiomycosis. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 333:706-719. [PMID: 33052039 PMCID: PMC7821119 DOI: 10.1002/jez.2419] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 08/26/2020] [Accepted: 09/24/2020] [Indexed: 12/26/2022]
Abstract
Understanding host immune function and ecoimmunology is increasingly important at a time when emerging infectious diseases (EIDs) threaten wildlife. One EID that has emerged and spread widely in recent years is chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), which is implicated unprecedented amphibian declines around the world. The impacts of Bd have been severe for many amphibian species, but some populations have exhibited signs of persistence, and even recovery, in some regions. Many mechanisms may underpin this pattern and amphibian immune responses are likely one key component. Although we have made great strides in understanding amphibian immunity, the complement system remains poorly understood. The complement system is a nonspecific, innate immune defense that is known to enhance other immune responses. Complement activation can occur by three different biochemical pathways and result in protective mechanisms, such as inflammation, opsonization, and pathogen lysis, thereby providing protection to the host. We currently lack an understanding of complement pathway activation for chytridiomycosis, but several studies have suggested that it may be a key part of an early and robust immune response that confers host resistance. Here, we review the available research on the complement system in general as well as amphibian complement responses to Bd infection. Additionally, we propose future research directions that will increase our understanding of the amphibian complement system and other immune responses to Bd. Finally, we suggest how a deeper understanding of amphibian immunity could enhance the conservation and management of amphibian species that are threatened by chytridiomycosis.
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Affiliation(s)
| | - Jamie Voyles
- Department of Biology, University of Nevada-Reno, Reno, Nevada, USA
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11
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Savage AE, Gratwicke B, Hope K, Bronikowski E, Fleischer RC. Sustained immune activation is associated with susceptibility to the amphibian chytrid fungus. Mol Ecol 2020; 29:2889-2903. [PMID: 32700351 DOI: 10.1111/mec.15533] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Revised: 06/06/2020] [Accepted: 06/26/2020] [Indexed: 12/15/2022]
Abstract
The disease chytridiomycosis caused by the fungus Bd has devastated amphibian populations worldwide. Functional genomic contributions to host susceptibility remain enigmatic and vary between species and populations. We conducted experimental Bd infections in Rana yavapaiensis, a species with intraspecific variation in chytridiomycosis susceptibility, to assess the skin and spleen transcriptomic response to infection over time. We predicted that increased immune gene expression would be associated with a positive disease outcome, but we instead found that surviving frogs had significantly reduced immune gene expression compared to susceptible frogs and to uninfected controls. MHC class IIβ gene expression was also significantly higher in susceptible frogs compared to surviving frogs. Furthermore, susceptible frogs expressed a significantly larger number of distinct class IIβ alleles, demonstrating a negative correlation between class IIβ expression, functional diversity, and survival. Expression of the MHC class IIβ locus previously associated with Bd disease outcomes was a significant predictor of Bd infection intensity at early infection stages but not at late infection stages, suggesting initial MHC-linked immune processes are important for ultimate disease outcomes. We infer through disease association and phylogenetic analysis that certain MHC variants are linked to the immune expression that was negatively associated with survival, and we hypothesize that frogs that did not express these alleles could better survive infections. Our study finds that MHC expression at early and late infection stages predicts Bd infection intensity, and suggests that generating a sustained immune response against Bd may be counterproductive for surviving chytridiomycosis in this partially susceptible species.
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Affiliation(s)
- Anna E Savage
- Department of Biology, University of Central Florida, Orlando, FL, USA.,Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
| | - Brian Gratwicke
- Center for Species Survival, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
| | - Katharine Hope
- Center for Animal Care Sciences, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
| | - Edward Bronikowski
- Center for Animal Care Sciences, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
| | - Robert C Fleischer
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
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12
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Williams ST, Haas CA, Roberts JH, Taylor SS. Depauperate major histocompatibility complex variation in the endangered reticulated flatwoods salamander (Ambystoma bishopi). Immunogenetics 2020; 72:263-274. [PMID: 32300829 DOI: 10.1007/s00251-020-01160-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 03/09/2020] [Indexed: 11/28/2022]
Abstract
Reticulated flatwoods salamander (Ambystoma bishopi) populations began decreasing dramatically in the 1900s. Contemporary populations are small, isolated, and may be susceptible to inbreeding and reduced adaptive potential because of low genetic variation. Genetic variation at immune genes is especially important as it influences disease susceptibility and adaptation to emerging infectious pathogens, a central conservation concern for declining amphibians. We collected samples from across the extant range of this salamander to examine genetic variation at major histocompatibility complex (MHC) class Iα and IIβ exons as well as the mitochondrial control region. We screened tail or toe tissue for ranavirus, a pathogen associated with amphibian declines worldwide. Overall, we found low MHC variation when compared to other amphibian species and did not detect ranavirus at any site. MHC class Iα sequencing revealed only three alleles with a nucleotide diversity of 0.001, while MHC class IIβ had five alleles with a with nucleotide diversity of 0.004. However, unique variation still exists across this species' range with private alleles at three sites. Unlike MHC diversity, mitochondrial variation was comparable to levels estimated for other amphibians with nine haplotypes observed, including one haplotype shared across all sites. We hypothesize that a combination of a historic disease outbreak and a population bottleneck may have contributed to low MHC diversity while maintaining higher levels of mitochondrial DNA variation. Ultimately, MHC data indicated that the reticulated flatwoods salamander may be at an elevated risk from infectious diseases due to low levels of immunogenetic variation necessary to combat novel pathogens.
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Affiliation(s)
- Steven Tyler Williams
- School of Renewable Natural Resources, Louisiana State University AgCenter, Baton Rouge, LA, 70806, USA.
| | - Carola A Haas
- Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA, 24061, USA
| | - James H Roberts
- Department of Biology, Georgia Southern University, Statesboro, GA, 30458, USA
| | - Sabrina S Taylor
- School of Renewable Natural Resources, Louisiana State University AgCenter, Baton Rouge, LA, 70806, USA
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Brannelly LA, Ohmer MEB, Saenz V, Richards‐Zawacki CL. Effects of hydroperiod on growth, development, survival and immune defences in a temperate amphibian. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13419] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Laura A. Brannelly
- Department of Biological Sciences, Dietrich School of Arts and Sciences University of Pittsburgh Pittsburgh PA USA
| | - Michel E. B. Ohmer
- Department of Biological Sciences, Dietrich School of Arts and Sciences University of Pittsburgh Pittsburgh PA USA
| | - Veronica Saenz
- Department of Biological Sciences, Dietrich School of Arts and Sciences University of Pittsburgh Pittsburgh PA USA
| | - Corinne L. Richards‐Zawacki
- Department of Biological Sciences, Dietrich School of Arts and Sciences University of Pittsburgh Pittsburgh PA USA
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14
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Garcia MJ, Rodríguez-Brenes S, Kobisk A, Adler L, Ryan MJ, Taylor RC, Hunter KL. Epigenomic changes in the túngara frog (Physalaemus pustulosus): possible effects of introduced fungal pathogen and urbanization. Evol Ecol 2019. [DOI: 10.1007/s10682-019-10001-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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15
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Doody KA, Ohmer ME, Cramp RL, Franklin CE. Do Frogs Infected with Batrachochytrium dendrobatidis Avoid Water While Sloughing? HERPETOLOGICA 2019. [DOI: 10.1655/d-18-00014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Kathleen A. Doody
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Michel E.B. Ohmer
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia
| | - Rebecca L. Cramp
- School of Biological Sciences, The University of Queensland, St. Lucia, QLD 4072, Australia
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Longo AV, Fleischer RC, Lips KR. Double trouble: co-infections of chytrid fungi will severely impact widely distributed newts. Biol Invasions 2019. [DOI: 10.1007/s10530-019-01973-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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Hoelzel AR, Bruford MW, Fleischer RC. Conservation of adaptive potential and functional diversity. CONSERV GENET 2019. [DOI: 10.1007/s10592-019-01151-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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18
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Brannelly LA, Chatfield MWH, Sonn J, Robak M, Richards-Zawacki CL. Fungal infection has sublethal effects in a lowland subtropical amphibian population. BMC Ecol 2018; 18:34. [PMID: 30217158 PMCID: PMC6137908 DOI: 10.1186/s12898-018-0189-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 09/03/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), has been implicated as a primary cause of decline in many species around the globe. However, there are some species and populations that are known to become infected in the wild, yet declines have not been observed. Here we conducted a yearlong capture-mark-recapture study and a 2-year long disease monitoring study of northern cricket frogs, Acris crepitans, in the lowland subtropical forests of Louisiana. RESULTS We found little evidence for an impact of Bd infection on survival; however, Bd infection did appear to cause sublethal effects, including increased capture probability in the field. CONCLUSIONS Our study suggests that even in apparently stable populations, where Bd does not appear to cause mortality, there may be sublethal effects of infection that can impact a host population's dynamics and structure. Understanding and documenting such sublethal effects of infection on wild, seemingly stable populations is important, particularly for predicting future population declines.
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Affiliation(s)
- Laura A Brannelly
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA.
| | | | - Julia Sonn
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA, USA
| | - Matthew Robak
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA, USA
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Sebastiano M, Eens M, Messina S, AbdElgawad H, Pineau K, Beemster GTS, Chastel O, Costantini D. Resveratrol supplementation reduces oxidative stress and modulates the immune response in free‐living animals during a viral infection. Funct Ecol 2018. [DOI: 10.1111/1365-2435.13195] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Manrico Sebastiano
- Department of Biology, Behavioural Ecology and Ecophysiology GroupUniversity of Antwerp Antwerp Belgium
| | - Marcel Eens
- Department of Biology, Behavioural Ecology and Ecophysiology GroupUniversity of Antwerp Antwerp Belgium
| | - Simone Messina
- Department of Biology, Behavioural Ecology and Ecophysiology GroupUniversity of Antwerp Antwerp Belgium
| | - Hamada AbdElgawad
- Department of Biology, Integrated Molecular Plant Physiology Research (IMPRES)University of Antwerp Antwerp Belgium
| | - Kévin Pineau
- Groupe d'Etude et de Protection des Oiseaux en Guyane (GEPOG) Cayenne French Guiana
| | - Gerrit T. S. Beemster
- Department of Biology, Integrated Molecular Plant Physiology Research (IMPRES)University of Antwerp Antwerp Belgium
| | - Olivier Chastel
- Centre d’Etudes Biologiques de Chizé (CEBC)UMR7372 ‐ CNRS/University of La Rochelle La Rochelle France
| | - David Costantini
- Department of Biology, Behavioural Ecology and Ecophysiology GroupUniversity of Antwerp Antwerp Belgium
- UMR 7221 CNRS/MNHN, Muséum National d'Histoire NaturelleSorbonne Universités Paris France
- Institute of Biodiversity, Animal Health and Comparative MedicineUniversity of Glasgow Glasgow UK
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Lips KR. Overview of chytrid emergence and impacts on amphibians. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0465. [PMID: 28080989 DOI: 10.1098/rstb.2015.0465] [Citation(s) in RCA: 135] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2016] [Indexed: 11/12/2022] Open
Abstract
Chytridiomycosis is an emerging infectious disease of amphibians that affects over 700 species on all continents where amphibians occur. The amphibian-chytridiomycosis system is complex, and the response of any amphibian species to chytrid depends on many aspects of the ecology and evolutionary history of the amphibian, the genotype and phenotype of the fungus, and how the biological and physical environment can mediate that interaction. Impacts of chytridiomycosis on amphibians are varied; some species have been driven extinct, populations of others have declined severely, whereas still others have not obviously declined. Understanding patterns and mechanisms of amphibian responses to chytrids is critical for conservation and management. Robust estimates of population numbers are needed to identify species at risk, prioritize taxa for conservation actions, design management strategies for managing populations and species, and to develop effective measures to reduce impacts of chytrids on amphibians.This article is part of the themed issue 'Tackling emerging fungal threats to animal health, food security and ecosystem resilience'.
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Affiliation(s)
- Karen R Lips
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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21
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Early exposure to Batrachochytrium dendrobatidis causes profound immunosuppression in amphibians. EUR J WILDLIFE RES 2017. [DOI: 10.1007/s10344-017-1161-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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22
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Oxidative stress biomarkers are associated with visible clinical signs of a disease in frigatebird nestlings. Sci Rep 2017; 7:1599. [PMID: 28487518 PMCID: PMC5431617 DOI: 10.1038/s41598-017-01417-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 03/29/2017] [Indexed: 02/07/2023] Open
Abstract
Infectious diseases are one of the most common threats for both domestic and wild animals, but little is known about the effects on the physiological condition and survival of wild animals. Here, we have tested for the first time in a wild vertebrate facing a viral disease possibly due to herpesvirus (i) whether nestlings with either low levels of oxidative damage or high levels of antioxidant protection are less susceptible to develop visible clinical signs, (ii) whether the disease is associated with the nestlings’ oxidative status, (iii) whether the association between the disease and oxidative status is similar between males and females (iv), and whether cloacal and tracheal swabs might be used to detect herpesvirus. To address our questions, we took advantage of a population of Magnificent frigatebirds (Fregata magnificens) whose nestlings have experienced high mortality rates in recent times. Our work shows that (i) blood lipid oxidative damage is associated with observable clinical signs and survival probabilities of nestling frigatebirds, and (ii) that high glutathione levels in red blood cells are associated with the emergence of visible clinical signs of the disease. Our work provides evidence that differences in the oxidative status of nestlings might underlie individual health and survival.
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23
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Maslo B, Gignoux-Wolfsohn SA, Fefferman NH. Success of Wildlife Disease Treatment Depends on Host Immune Response. Front Ecol Evol 2017. [DOI: 10.3389/fevo.2017.00028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
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Gabor C, Forsburg Z, Vörös J, Serrano-Laguna C, Bosch J. Differences in chytridiomycosis infection costs between two amphibian species from Central Europe. AMPHIBIA-REPTILIA 2017. [DOI: 10.1163/15685381-00003099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Batrachochytrium dendrobatidis (Bd) causes the disease chytridiomycosis associated with amphibian declines. Response and costs of infection varies greatly between species. Bd can induce a stress response in amphibians resulting in elevated corticosterone (CORT). We exposed Bombina variegata and Hyla arborea tadpoles to Bd+ or Bd- Salamandra salamandra larvae and measured CORT release rates, Bd infection loads, and survival through metamorphosis. Tadpoles of both species exposed to Bd+ larvae had elevated CORT release rates compared to tadpoles exposed to Bd- larvae. Bombina variegata appear less resistant to infection than H. arborea, showing higher Bd loads and more infected individuals. Within species, we did not find differences in cost of infection on survival, however more B. variegata tadpoles reached metamorphosis than H. arborea. The differences in resistance may be species specific, owing to higher immunity defenses with H. arborea having higher overall CORT release rates, and differences in antimicrobial peptides, or to differences in Bd strain or other unexplored mechanisms.
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Affiliation(s)
- Caitlin Gabor
- Texas State University, 601 University Drive, San Marcos, Texas, 78666, USA
| | - Zachery Forsburg
- Texas State University, 601 University Drive, San Marcos, Texas, 78666, USA
| | - Judit Vörös
- Department of Zoology, Hungarian Natural History Museum, 1088 Budapest, Baross u. 13., Hungary
| | - Celia Serrano-Laguna
- Museo Nacional de Ciencias Naturales, CSIC, c/ José Gutiérrez Abascal 2, 28006 Madrid, Spain
| | - Jaime Bosch
- Museo Nacional de Ciencias Naturales, CSIC, c/ José Gutiérrez Abascal 2, 28006 Madrid, Spain
- Centro de Investigación, Seguimiento y Evaluación, Parque Nacional de la Sierra de Guadarrama, Cta. M-604, km 27.6, 28740 Rascafría, Spain
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25
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Longo AV, Zamudio KR. Environmental fluctuations and host skin bacteria shift survival advantage between frogs and their fungal pathogen. ISME JOURNAL 2016; 11:349-361. [PMID: 27935596 DOI: 10.1038/ismej.2016.138] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 08/08/2016] [Accepted: 08/15/2016] [Indexed: 12/11/2022]
Abstract
Fluctuating environments can modulate host-pathogen interactions by providing a temporary advantage to one of the interacting organisms. However, we know very little about how environmental conditions facilitate beneficial interactions between hosts and their microbial communities, resulting in individual persistence with a particular pathogen. Here, we experimentally infected Eleutherodactylus coqui frogs with the fungal pathogen Batrachochytrium dendrobatidis (Bd) under environmental conditions known to confer the survival advantage to the host during the warm-wet season, or alternatively to the pathogen during the cool-dry season. We used 16S rRNA amplicon sequencing to quantify changes in bacterial richness and phylogenetic diversity, and identified operational taxonomic units (OTUs) that became overrepresented or suppressed as a consequence of Bd infection. During the warm-wet season, frogs limited Bd infections, recruited putatively beneficial bacteria and returned to pre-infection levels of richness and phylogenetic diversity. In contrast, during the cool-dry season, Bd infections kept increasing through time, and bacterial diversity remained constant. Our findings confirm that infection outcome not only depends on abiotic factors, but also on biotic interactions between hosts and their associated bacterial communities.
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Affiliation(s)
- Ana V Longo
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
| | - Kelly R Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
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