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Diseases of Aquatic Organisms

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DAO 68:65-70 (2005)  -  doi:10.3354/dao068065

Distribution of Batrachochytrium dendrobatidis and pathology in the skin of green tree frogs Litoria caerulea with severe chytridiomycosis

Lee Berger1,*, Rick Speare1, Lee F. Skerratt2

1Amphibian Disease Ecology Group, School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Townsville, Queensland 4811, Australia
2Amphibian Disease Ecology Group, School of Veterinary and Biomedical Sciences, James Cook University, Townsville, Queensland 4811, Australia

ABSTRACT: Although histopathology is used routinely for diagnosis of chytridiomycosis in live and dead amphibians, there are no quantitative data on the distribution of the causative fungus, Batrachochytrium dendrobatidis, in the skin. We performed quantitative histological examinations on 6 sites on the body and 4 toes of 10 free-ranging adult green tree frogs Litoria caerulea found recently dead or dying from chytridiomycosis. Large numbers of sporangia occurred in all areas of ventral skin and toes; on average there were 94.3 sporangia mm–1 of superficial epidermis. The number of sporangia was highly variable and this appeared to be related to the stage in the cycle of sloughing. The stratum corneum tends to build up with high intensities of infection and then sheds entirely rather than being shed continuously. Very few or no sporangia occurred on dorsal skin. This distribution could be explained by the dryness of the dorsal skin or possibly by the greater number of serous glands, which produce antifungal peptides, on the dorsum. In some frogs, ulceration and erosions occurred on skin on the back in the absence of sporangia. Other pathological changes such as hyperkeratosis and congestion occurred much more frequently on ventral surfaces.

KEY WORDS: Batrachochytrium dendrobatidis · Distribution · Amphibian · Pathology · Ulceration · Litoria caerulea

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