Methods for Estimating the Volume of the Tympanic Bulla in the Big Hairy Armadillo Chaetophractus villosus

Two methods of measurement of bullar dimensions (callipers and scaling from digital images) and subsequent application of four volume formulae (rectangular prism, cylinder, ellipse and elliptical cone) were tested to find the most appropriate non-destructive method for estimating the bullar volume i...

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Veröffentlicht in:International journal of morphology 2017-03, Vol.35 (1), p.128
Hauptverfasser: Basso, Ana Paula, Sidorkewicj, Nora Silvia, Casanave, Emma Beatriz
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Sprache:spa
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Zusammenfassung:Two methods of measurement of bullar dimensions (callipers and scaling from digital images) and subsequent application of four volume formulae (rectangular prism, cylinder, ellipse and elliptical cone) were tested to find the most appropriate non-destructive method for estimating the bullar volume in Chaetophractus villosus. Material for the study consisted in clean adult skull (n=22). Real volume was obtained from latex casts of the tympanic bulla. Each estimation was corrected by a factor based on the differences between the estimated and the real volumes. Highest accuracy (5-7 % of underestimation) and precision (coefficient of variation: 13.27 %) were obtained from callipers and application of rectangular prism, cylinder and ellipse formulae. The corresponding correction factors were 0.31, 0.39 and 0.58, respectively. KEY WORDS: Fossorial mammals; Armadillos; Middle ear; Auditory bulla; Non-destructive methods. Se evaluaron dos metodos para la obtencion de medidas de la bula (calibre y escalado a partir de imagenes digitales), con posterior aplicacion de cuatro formulas de volumen (prisma rectangular, cilindro, elipse y cono eliptico), a fin de hallar el metodo no destructivo mas adecuado para el calculo de volumen de bula en Chaetophractus villosus. El material de estudio consistio en craneos limpios de individuos adultos (n=22). El volumen real fue obtenido a partir de moldes de latex de la bula timpanica. Cada estimacion fue corregida mediante un factor basado en las diferencias entre los volumenes reales y estimados. La mayor precision (coeficiente de variacion: 13,27 %) y exactitud (subestimaciones del 5-7 %) fueron obtenidas a partir de mediciones con calibre y aplicacion de formulas de prisma rectangular, cilindro y elipse (factores de correccion: 0,31, 0,39 y 0,58, respectivamente). PALABRAS CLAVE: Mamiferos fosoriales; Armadillos; Oido medio; Bula auditiva; Metodos no destructivos.
ISSN:0717-9367