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Cabanzo-Olarte LC, Cardoso Bícego K, Navas Iannini CA. Behavioral responses during sickness in amphibians and reptiles: Concepts, experimental design, and implications for field studies. J Therm Biol 2024; 123:103889. [PMID: 38897001 DOI: 10.1016/j.jtherbio.2024.103889] [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: 11/09/2023] [Revised: 06/09/2024] [Accepted: 06/10/2024] [Indexed: 06/21/2024]
Abstract
In ectothermic vertebrates, behavioral fever, where an individual actively seeks warmer areas, seems to be a primary response to pathogens. This is considered a broad and evolutionarily conserved response among vertebrates. Recent population declines in amphibians are associated with an increase of infectious disease driven largely by climate change, habitat degradation, and pollution. Immediate action through research is required to better understand and inform conservation efforts. The literature available, does not provide unifying concepts that can guide adequate experimental protocols and interpretation of data, especially when studying animals in the field. The aim of this review is to promote common understanding of terminology and facilitating improved comprehension and application of key concepts about the occurrence of both sickness behavior or behavioral fever in ectothermic vertebrates. We start with a conceptual synthesis of sickness behavior and behavioral fever, with examples in different taxa. Through this discussion we present possible paths to standardize terminology, starting from original use in endothermic tetrapods which was expanded to ectothermic vertebrates, particularly amphibians and reptiles. This conceptual expansion from humans (endothermic vertebrates) and then to ectothermic counterparts, gravitates around the concept of 'normality'. Thus, following this discussion, we highlight caveats with experimental protocols and state the need of a reference value considered normal (RVCN), which is different from experimental control and make recommendations regarding experimental procedures and stress the value of detailed documentation of behavioral responses. We also propose some future directions that could enhance interaction among disciplines, emphasizing relationships at different levels of biological organization. This is crucial given the increasing convergence of fields such as thermal physiology, immunology, and animal behavior due to emerging diseases and other global crises impacting biodiversity.
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Affiliation(s)
- Laura Camila Cabanzo-Olarte
- Physiology Department, Biosciences Institute, University of São Paulo, Trav. 14, N 321, CEP 05508-090 São Paulo, SP, Brazil.
| | - Kênia Cardoso Bícego
- Department of Animal Morphology and Physiology, São Paulo State University (FCAV-UNESP), Via de Acesso Prof. Paulo Donato Castellane s/n, Jaboticabal, SP 14884-900, Brazil.
| | - Carlos Arturo Navas Iannini
- Physiology Department, Biosciences Institute, University of São Paulo, Trav. 14, N 321, CEP 05508-090 São Paulo, SP, Brazil.
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Kásler A, Holly D, Herczeg D, Ujszegi J, Hettyey A. Chytridiomycosis and climate change: exposure to
Batrachochytrium dendrobatidis
and mild winter conditions do not increase mortality in juvenile agile frogs during hibernation. Anim Conserv 2023. [DOI: 10.1111/acv.12851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- A. Kásler
- Department of Evolutionary Ecology Centre for Agricultural Research, Plant Protection Institute, Eötvös Loránd Research Network Budapest Hungary
- Doctoral School of Biology Institute of Biology, ELTE Eötvös Loránd University Budapest Hungary
| | - D. Holly
- Department of Evolutionary Ecology Centre for Agricultural Research, Plant Protection Institute, Eötvös Loránd Research Network Budapest Hungary
- Doctoral School of Biology Institute of Biology, ELTE Eötvös Loránd University Budapest Hungary
| | - D. Herczeg
- Department of Evolutionary Ecology Centre for Agricultural Research, Plant Protection Institute, Eötvös Loránd Research Network Budapest Hungary
- ELKH‐ELTE‐MTM Integrative Ecology Research Group Budapest Hungary
| | - J. Ujszegi
- Department of Evolutionary Ecology Centre for Agricultural Research, Plant Protection Institute, Eötvös Loránd Research Network Budapest Hungary
- Department of Systematic Zoology and Ecology ELTE Eötvös Loránd University Budapest Hungary
| | - A. Hettyey
- Department of Evolutionary Ecology Centre for Agricultural Research, Plant Protection Institute, Eötvös Loránd Research Network Budapest Hungary
- Department of Systematic Zoology and Ecology ELTE Eötvös Loránd University Budapest Hungary
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Venesky MD, DeMarchi J, Hickerson C, Anthony CD. Does the thermal mismatch hypothesis predict disease outcomes in different morphs of a terrestrial salamander? JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2022; 337:467-476. [PMID: 35167180 DOI: 10.1002/jez.2581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 12/23/2021] [Accepted: 01/19/2022] [Indexed: 06/14/2023]
Abstract
Many aspects of ectotherm physiology are temperature-dependent. The immune system of temperate-dwelling ectothermic host species is no exception and their immune function is often downregulated in cold temperatures. Likewise, species of ectothermic pathogens experience temperature-mediated effects on rates of transmission and/or virulence. Although seemingly straightforward, predicting the outcomes of ectothermic host-pathogen interactions is quite challenging. A recent hypothesis termed the thermal mismatch hypothesis posits that cool-adapted host species should be most susceptible to pathogen infection during warm temperature periods whereas warm-adapted host species should be most susceptible to pathogens during periods of cool temperatures. We explore this hypothesis using two ecologically and physiologically differentiated color morphs of the Eastern Red-backed Salamander (Plethodon cinereus) and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis; hereafter "Bd") using a fully factorial laboratory experiment. At cool temperatures, unstriped salamanders (i.e., those that are tolerant of warm temperatures) had a significantly higher probability of Bd infection compared with cool-tolerant striped salamanders, consistent with the thermal mismatch hypothesis. However, we found no support for this hypothesis when salamanders were exposed to Bd at warm temperatures: the probability of Bd infection in the cool-tolerant striped salamanders was nearly identical in both cool and warm temperatures, opposite the predictions of the thermal mismatch hypothesis. Our results are most consistent with the fact that Bd grows poorly at warm temperatures. Alternatively, our data could indicate that the two color morphs do not differ in their tolerance to warm temperatures but that striped salamanders are more tolerant to cool temperatures than unstriped salamanders.
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Affiliation(s)
- Matthew D Venesky
- Department of Biology, Allegheny College, Meadville, Pennsylvania, USA
| | - Joseph DeMarchi
- Department of Biology, John Carroll University, University Heights, Ohio, USA
| | - Cari Hickerson
- Department of Biology, John Carroll University, University Heights, Ohio, USA
| | - Carl D Anthony
- Department of Biology, John Carroll University, University Heights, Ohio, USA
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Venesky MD, Laskey CA. Infection with Batrachochytrium dendrobatidis reduces salamander capacity to mount a cell-mediated immune response. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 337:273-281. [PMID: 34102032 DOI: 10.1002/jez.2497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 05/07/2021] [Accepted: 05/14/2021] [Indexed: 11/06/2022]
Abstract
The vertebrate immune system is a costly defense system that is responsible for preventing and eliminating parasites and pathogens. Theory predicts that hosts experience tradeoffs associated with immune deployment and other physiological functions. Although empirical evidence for immune-physiology tradeoffs are well documented in the literature, fewer studies have examined tradeoffs within the immune system in wild vertebrates. We explored the topic of concomitant immune challenges in amphibians by exposing salamanders (Plethodon cinereus) to a fungal pathogen Batrachochytrium dendrobatidis (hereafter "Bd") and then to phytohemagglutinin (hereafter "PHA"). We measured Bd infection using quantitative PCR and used measurements of the tail thickness at the PHA injection site as an estimate of skin swelling. We tested whether Bd reduced the salamander's capacity to mount an immune response towards PHA or whether Bd would stimulate immune activity and thereby increase the response towards PHA. Salamanders that were infected with Bd had a reduced skin-swelling when injected with PHA compared to noninfected salamanders, a result that is consistent with the hypothesis that Bd-infected salamanders have lower immunocompetence than noninfected salamanders. We also found that PHA-induced swelling response was negatively associated with Bd infection abundance (i.e., the infection burden of all exposed salamanders, including those that were exposed but not infected), indicating that salamanders with a higher infection abundance had the lowest swelling response to PHA. Our results suggest that individuals of P. cinereus might experience an energetic tradeoff between successfully fighting off Bd and mounting an immune response towards PHA.
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Affiliation(s)
- Matthew D Venesky
- Department of Biology, Allegheny College, Meadville, Pennsylvania, USA
| | - Corey A Laskey
- Department of Biology, Allegheny College, Meadville, Pennsylvania, USA
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Ramsay C, Rohr JR. The application of community ecology theory to co-infections in wildlife hosts. Ecology 2021; 102:e03253. [PMID: 33222193 DOI: 10.1002/ecy.3253] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/27/2020] [Accepted: 09/18/2020] [Indexed: 11/11/2022]
Abstract
Priority effect theory, a foundational concept from community ecology, states that the order and timing of species arrival during species assembly can affect species composition. Although this theory has been applied to co-infecting parasite species, it has almost always been with a single time lag between co-infecting parasites. Thus, how the timing of parasite species arrival affects co-infections and disease remains poorly understood. To address this gap in the literature, we exposed postmetamorphic Cuban tree frogs (Osteopilus septentrionalis) to Ranavirus, the fungus Batrachochytrium dendrobatidis (Bd), a nematode Aplectana hamatospicula, or pairs of these parasites either simultaneously or sequentially at a range of time lags and quantified load of the secondary parasite and host growth, survival, and parasite tolerance. Prior exposure to Bd or A. hamatospicula significantly increased viral loads relative to hosts singly infected with Ranavirus, whereas A. hamatospicula loads in hosts were higher when coexposed to Bd than when coexposed to Ranavirus. There was a significant positive relationship between time since Ranavirus infection and Bd load, and prior exposure to A. hamatospicula decreased Bd loads compared to simultaneous co-infection with these parasites. Infections with Bd and Ranavirus either singly or in co-infections decreased host growth and survival. This research reveals that time lags between co-infections can affect parasite loads, in line with priority effects theory. As co-infections in the field are unlikely to be simultaneous, an understanding of when co-infections are impacted by time lags between parasite exposures may play a major role in controlling problematic co-infections.
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Affiliation(s)
- Chloe Ramsay
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, 46556, USA
| | - Jason R Rohr
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, 46556, USA
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Female Salamanders Experience Higher Parasitism Compared to Males: A Cost of Female Reproduction? J HERPETOL 2020. [DOI: 10.1670/19-072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Barnhart KL, Bletz MC, LaBumbard BC, Tokash-Peters AG, Gabor CR, Woodhams DC. Batrachochytrium salamandrivorans ELICITS ACUTE STRESS RESPONSE IN SPOTTED SALAMANDERS BUT NOT INFECTION OR MORTALITY. Anim Conserv 2020; 23:533-546. [PMID: 33071596 DOI: 10.1111/acv.12565] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The emerging fungal pathogen Batrachochytrium salamandrivorans (Bsal) is a major threat to amphibian species worldwide with potential to infect many species if it invades salamander biodiversity hotspots in the Americas. Bsal can cause the disease chytridiomycosis, and it is important to assess the risk of Bsal-induced chytridiomycosis to species in North America. We evaluated the susceptibility to Bsal of the common and widespread spotted salamander, Ambystoma maculatum, across life history stages and monitored the effect of Bsal exposure on growth rate and response of the stress hormone, corticosterone. We conclude that spotted salamanders appear resistant to Bsal because they showed no indication of disease or infection, and experienced minor effects on growth upon exposure. While we focused on a single population for this study, results were consistent across conditions of exposure including high or repeated doses of Bsal, life-stage at exposure, environmental conditions including two temperatures and two substrates, and promoting pathogen infectivity by conditioning Bsal cultures with thyroid hormone. Exposure to high levels of Bsal elicited an acute but not chronic increase in corticosterone in spotted salamanders, and reduced growth. We hypothesize that the early acute increase in corticosterone facilitated mounting an immune response to the pathogen, perhaps through immunoredistribution to the skin, but further study is needed to determine immune responses to Bsal. These results will contribute to development of appropriate Bsal management plans to conserve species at risk of emerging disease.
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Affiliation(s)
- Kelly L Barnhart
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Molly C Bletz
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Brandon C LaBumbard
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Amanda G Tokash-Peters
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Caitlin R Gabor
- Texas State University, Department of Biology, 601 University Drive, San Marcos, TX 78666
| | - Douglas C Woodhams
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
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Disease and climate effects on individuals drive post‐reintroduction population dynamics of an endangered amphibian. Ecosphere 2018. [DOI: 10.1002/ecs2.2499] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
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Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies. DIVERSITY-BASEL 2018. [DOI: 10.3390/d10030081] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease.
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