Article

Relationship among size, development, and Batrachochytrium dendrobatidis infection in African tadpoles.

School of Environmental Sciences and Development, North-West University, Private Bag x6001, Potchefstroom 2520, South Africa.
Diseases of Aquatic Organisms (Impact Factor: 1.75). 03/2007; 74(2):159-64. DOI: 10.3354/dao074159
Source: PubMed

ABSTRACT

The fungal pathogen Batrachochytrium dendrobatidis contributes to the global decline of amphibians. Although mortality from B. dendrobatidis infections occurs primarily in postmetamorphic individuals, infected tadpoles may suffer reduced growth and developmental rates as a result of oral chytridiomycosis, possibly affecting adult fitness. We conducted a field study in which we examined South African tadpoles for oral chytridiomycosis and compared the body sizes of infected and uninfected individuals of 2 species, Heleophryne natalensis and Strongylopus hymenopus. Presence of B. dendrobatidis was determined by microscopic inspection of mouthparts. Infection prevalence was high in both species, 62.5 and 38.6%, respectively, and infected individuals were significantly larger in both species. The inclusion of developmental stage in the analysis of S. hymenopus body size eliminated the relationship between body size and infection status, suggesting that differences in body size were not due to differences in growth, but to differences in developmental stage of infected larvae. These results suggest that larvae at more advanced developmental stages are more likely to be infected with B. dendrobatidis and that infection in larval amphibians may be dependent on time or developmental status of larvae. Contrary to the results of past studies, there was no evidence that oral chytridiomycosis resulted in decreased growth of tadpoles, despite the occurrence of oral abnormalities in infected individuals of 1 species. Because tadpole performance can subsequently affect the health of anuran populations and because tadpoles can act as reservoirs of infection, the study of B. dendrobatidis in larval amphibians is important to understanding the effects of this emerging disease.

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    • "In general, a strong support exists to indicate that number of posterior labial tooth rows increase with body size. Remaining variations are due to environmental factors, such as feeding behaviour, food availability, flooding, and damage by the amphibian chytrid fungus (Smith et al., 2007). Visser (1985) recorded a beak with fang-like teeth that precedes the tooth rows during the first month of development, though he only recorded the total length of tadpoles. "
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    • "Bd infects keratinized tissues, such as anuran larval mouthparts, reducing their foraging capabilities [18]–[20]. While Bd does not generally cause mortality in larvae (as it does in adults), the fungus often impairs growth and developmental rates [21]–[24]. Venesky et al. [20] found that Bd altered larval mouthparts, resulting in Hyla chrysoscelis (Cope’s treefrog) larvae foraging less efficiently than uninfected individuals. Additionally, Hanlon et al. (unpublished data) found that infected Hyla versicolor (gray treefrog) larvae spent significantly more time foraging than uninfected individuals. "
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    • "Larger animals may acquire greater amounts of Bd, but may also be healthier and better able to resist infection (Carey et al. 1999), which could lead to longer survival. In previous studies with different species than the ones we studied here, both positive and negative relations have been found between body size and Bd infection (Kriger et al. 2007; Smith et al. 2007; Symonds et al. 2007). We found a positive correlation "
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