Differential pathogenicity of Fusarium semitectum in Texas turtles




Smith, Denise L.

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The Texas tortoise, Gopherus berlandieri, is susceptible to a fungal infection that presents as a white lesion on the thin epidermal scutes. Box turtles residing in the same environment are not susceptible. The fungal infection can be transferred to human fingernails by handling infected tortoises. Morphological characterization and polymerase chain reaction (PCR) analyses of cultured fungal samples were used to determine and verify the identity of the fungus as Fusarium semitectum. Pathogenicity of the isolated, cultured fungus was verified by applying samples of the cultured F. semitectum to shells of tortoises and box turtles. Growth occurred on the experimental sites of the tortoise shells but did not occur on the experimental sites of the box turtle shells. To determine if the fungal mycelium penetrated into the scutes, samples were taken from the experimental and control sites on the tortoise shell and viewed by scanning electron and confocal microscopy. Experiments were performed to determine nutritional requirements of the fungus. Results indicated that the F. semitectum is able to consume tortoise shell and fingernail, but does not consume box turtle shell. Extraction and analyses of scute and nail keratins were performed by sodium dodecylsulphate polyacrylamide gel electrophoresis (SOS-PAGE) and no significant differences were found. Subsequent to demonstration that F. semitectum is a lipase producer, analysis of scute fatty acids was performed by reversed phase high-performance liquid chromatography (HPLC). Results showed significant differences in fatty acid components among box turtle scutes, fingernails and tortoise scutes. This suggests that one or more fatty acids found in box turtle scutes have antifungal properties.



Fusarium semitectum, turtles, pathogens


Smith, D. L. (2000). Differential pathogenicity of Fusarium semitectum in Texas turtles (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.


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