DAO 116:199-203 (2015)  -  DOI: https://doi.org/10.3354/dao02936

Oxalate nephropathy in free-living American bullfrog tadpoles

Toshihiro Tokiwa1,2, Sho Kadekaru1, Masao Ito3, Makoto Yoshida4, Yumi Une1,*

1Laboratory of Veterinary Pathology, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan
2Division of Pathobiological Analysis, Department of Veterinary Pathobiology, Nippon Veterinary and Life Science University, 1-7-1 Kyonncho, Musashino, Tokyo 180-8602, Japan
3Nagasaki Biopark, 2-9-22, Saikai, Nagasaki 300-1252, Japan
4Kanagawa Agricultural Technology Center, 1617 Kamiyoshizawa, Hiratsuka, 259-1204 Japan
*Corresponding author:

ABSTRACT: In February 2014, wild American bullfrog Lithobates catesbeianus tadpoles from an artificial pond in the Kyusyu region, Japan, presented with coelomic and subcutaneous edema and erythema within the skin. A pathological examination of 57 tadpoles of American bullfrogs in the region was conducted to evaluate the disease. Crystal deposition of varying degrees was found in the kidneys of 35 tadpoles (61.4%). The crystals were transparent, pleomorphic in shape, highly birefringent in polarized light, and arranged in a radial pattern within the renal tubular lumen. Using Alizarin Red S stain and liquid chromatography, these crystals were identified as calcium oxalate. Severe coelomic and subcutaneous edema was observed in 7 of these 35 tadpoles (20.0%). Ammonia levels in coelomic fluid were extremely elevated (>1000 µg dl-1) in 4 tadpoles examined. These findings suggest that oxalate deposition in kidneys causes metabolic disorder with renal nephropathy. The source of the oxalate could not be determined; however, the presence of calcium oxalates in pond sediments, as revealed by liquid chromatography, suggested that the deposition was most likely due to ingestion of oxalate materials from the environment. This is the first report of oxalate nephropathy in free-living amphibians.


KEY WORDS: Lithobates catesbeianus · Edema · Renal oxalosis · Oxalate poisoning · Calcium oxalate · Japan


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Cite this article as: Tokiwa T, Kadekaru S, Ito M, Yoshida M, Une Y (2015) Oxalate nephropathy in free-living American bullfrog tadpoles. Dis Aquat Org 116:199-203. https://doi.org/10.3354/dao02936

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