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Field and laboratory studies of the susceptibility of the green treefrog (Hyla cinerea) to Batrachochytrium dendrobatidis infection.

Brannelly LA, Chatfield MW, Richards-Zawacki CL - PLoS ONE (2012)

Bottom Line: Although we were able to infect H. cinerea with Bd in the lab, we did not observe any clinical signs of chytridiomycosis.Furthermore, infection by Bd does not appear to negatively affect body condition or growth rate of post-metamorphic individuals.Our results suggest that H. cinerea is not susceptible to chytridiomycosis post-metamorphosis and probably is not an important carrier of the fungal pathogen Bd in the southeastern United States, although susceptibility at the larval stage remains unknown.

View Article: PubMed Central - PubMed

Affiliation: Ecology and Evolutionary Biology Department, Tulane University, New Orleans, Louisiana, United States of America. lbrannel@tulane.edu

ABSTRACT
Amphibians worldwide are experiencing devastating declines, some of which are due to the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd). Populations in the southeastern United States, however, have not been noticeably affected by the pathogen. The green treefrog (Hyla cinerea) is abundant and widespread in the southeastern United States, but has not been documented to harbor Bd infection. This study examined the susceptibility of H. cinerea to two strains of Bd in the lab and the prevalence of infection in wild populations of this species in southeastern Louisiana. Although we were able to infect H. cinerea with Bd in the lab, we did not observe any clinical signs of chytridiomycosis. Furthermore, infection by Bd does not appear to negatively affect body condition or growth rate of post-metamorphic individuals. We found no evidence of infection in surveys of wild H. cinerea. Our results suggest that H. cinerea is not susceptible to chytridiomycosis post-metamorphosis and probably is not an important carrier of the fungal pathogen Bd in the southeastern United States, although susceptibility at the larval stage remains unknown.

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Body condition does not differ between frogs infected with different strains of Bd.SRS810 infected individuals: grey. JEL423 infected individuals: black. Body condition was measured mass (g) divided by SVL (mm). Week indicates the number of weeks after last inoculation. Error bars are ± one standard error of the mean.
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pone-0038473-g003: Body condition does not differ between frogs infected with different strains of Bd.SRS810 infected individuals: grey. JEL423 infected individuals: black. Body condition was measured mass (g) divided by SVL (mm). Week indicates the number of weeks after last inoculation. Error bars are ± one standard error of the mean.

Mentions: The zoospore concentrations used for inoculations varied with both strain and day. Animals inoculated with SRS810 received a dose of 2.7×106 zoospores in the first inoculation, 1.6×106 zoospores in the second (two days later) and 0.4×106 zoospores in the third (another two days later). JEL423 animals were inoculated with 10.7×106 zoospores in the first, 55.4×106 zoospores in the second and 10.6×106 zoospores in the third inoculation. These animals were inoculated on the same schedule as the SRS810 group. Although the inoculation doses varied between the two strains, the zoospore loads detected on the animals did not differ between the two treatment groups one week after the final inoculation (t-test: t19 = 0.73, p = 0.47). All 20 lab animals contracted a Bd infection; however, some individuals cleared their infection over the course of the experiment. We considered an individual to have cleared its infection if its qPCR results were consistently Bd-negative after week 20. Over the course of the experiment there was no difference in body condition among frogs infected with different strains of Bd (JEL423 and SRS810, ANCOVA: F1,18 = 0.036, p = 0.856, see Fig. 3). Animals that retained an infection throughout the experiment also did not differ in body condition from animals that cleared their infection during the experiment (ANOVA: F1,18 = 1.611, p = 0.221, see Fig. 4).


Field and laboratory studies of the susceptibility of the green treefrog (Hyla cinerea) to Batrachochytrium dendrobatidis infection.

Brannelly LA, Chatfield MW, Richards-Zawacki CL - PLoS ONE (2012)

Body condition does not differ between frogs infected with different strains of Bd.SRS810 infected individuals: grey. JEL423 infected individuals: black. Body condition was measured mass (g) divided by SVL (mm). Week indicates the number of weeks after last inoculation. Error bars are ± one standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369911&req=5

pone-0038473-g003: Body condition does not differ between frogs infected with different strains of Bd.SRS810 infected individuals: grey. JEL423 infected individuals: black. Body condition was measured mass (g) divided by SVL (mm). Week indicates the number of weeks after last inoculation. Error bars are ± one standard error of the mean.
Mentions: The zoospore concentrations used for inoculations varied with both strain and day. Animals inoculated with SRS810 received a dose of 2.7×106 zoospores in the first inoculation, 1.6×106 zoospores in the second (two days later) and 0.4×106 zoospores in the third (another two days later). JEL423 animals were inoculated with 10.7×106 zoospores in the first, 55.4×106 zoospores in the second and 10.6×106 zoospores in the third inoculation. These animals were inoculated on the same schedule as the SRS810 group. Although the inoculation doses varied between the two strains, the zoospore loads detected on the animals did not differ between the two treatment groups one week after the final inoculation (t-test: t19 = 0.73, p = 0.47). All 20 lab animals contracted a Bd infection; however, some individuals cleared their infection over the course of the experiment. We considered an individual to have cleared its infection if its qPCR results were consistently Bd-negative after week 20. Over the course of the experiment there was no difference in body condition among frogs infected with different strains of Bd (JEL423 and SRS810, ANCOVA: F1,18 = 0.036, p = 0.856, see Fig. 3). Animals that retained an infection throughout the experiment also did not differ in body condition from animals that cleared their infection during the experiment (ANOVA: F1,18 = 1.611, p = 0.221, see Fig. 4).

Bottom Line: Although we were able to infect H. cinerea with Bd in the lab, we did not observe any clinical signs of chytridiomycosis.Furthermore, infection by Bd does not appear to negatively affect body condition or growth rate of post-metamorphic individuals.Our results suggest that H. cinerea is not susceptible to chytridiomycosis post-metamorphosis and probably is not an important carrier of the fungal pathogen Bd in the southeastern United States, although susceptibility at the larval stage remains unknown.

View Article: PubMed Central - PubMed

Affiliation: Ecology and Evolutionary Biology Department, Tulane University, New Orleans, Louisiana, United States of America. lbrannel@tulane.edu

ABSTRACT
Amphibians worldwide are experiencing devastating declines, some of which are due to the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd). Populations in the southeastern United States, however, have not been noticeably affected by the pathogen. The green treefrog (Hyla cinerea) is abundant and widespread in the southeastern United States, but has not been documented to harbor Bd infection. This study examined the susceptibility of H. cinerea to two strains of Bd in the lab and the prevalence of infection in wild populations of this species in southeastern Louisiana. Although we were able to infect H. cinerea with Bd in the lab, we did not observe any clinical signs of chytridiomycosis. Furthermore, infection by Bd does not appear to negatively affect body condition or growth rate of post-metamorphic individuals. We found no evidence of infection in surveys of wild H. cinerea. Our results suggest that H. cinerea is not susceptible to chytridiomycosis post-metamorphosis and probably is not an important carrier of the fungal pathogen Bd in the southeastern United States, although susceptibility at the larval stage remains unknown.

Show MeSH
Related in: MedlinePlus