Mandibular comparative morphometry of two armadillos from the south western Buenos Aires province, Argentina

CASANAVE, E.B.; SQUARCIA, S.M.; SIDORKEWICJ, N.S.; LODOVICHI, M.V.; CAMINA, R.E.

Mendoza, Argentina

Congreso; 10th International Mammalogical Congress; 2009

MANDIBULAR COMPARATIVE MORPHOMETRY OF TWO ARMADILLOS FROM THE SOUTH WESTERN BUENOS AIRES PROVINCE, ARGENTINA Casanave, Emma B.; Squarcia, Silvia M.; Sidorkewicj, Nora S.; Lodovichi, Mariela V. & Camina, Ricardo E. Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, Bahía Blanca, Buenos Aires, Argentina. CONICET; casanave@criba.edu.ar The morphometry of the mandible of two South American dasipodids, Chaetophractus vellerosus and Zaedyus pichiy, was studied using traditional and landmark-based geometric morphometric methods. Adult specimens (C. vellerosus: 13 males, 16 females; Z. pichiy: 13 males; 10 females), coming from the surroundings of Bahía Blanca, Argentina, were used. Eight linear mandibular characters were measured by means of a digital calliper (0.01 mm) and traditional multivariate analysis were applied. For geometric morphometric analysis (Thin-plate spline), 16 homologous landmarks were digitalized on photographs of the labial side of the left hemimandible. With the Principal Component analysis a tendency to segregation of the species was observed, with mandibles taller and shorter in C. vellerosus than in Z. pichiy. The body length of the mandible and the height at the level of the last tooth were the main variables that discriminate both species and sexes, with percentages of correct classification higher than 75 % in all cases. The geometric analysis showed clear differences in shape between species. The superimposition of the consensus configuration indicated mandibles with wider body and ramus, and a more acute angle between both structures in C. vellerosus than in Z. pichiy. The intra-specific comparison between males and females showed differences in the mandible shape only in Z. pichiy. Particularly, the relative position of the mandibular body with respect to the ramus, tends to be more open in males than in females. Future studies may allow toelucidate if differences in the shape of the mandible are related with the masticatory mechanical efficiency in both species. Funded by SGCyT (UNS), PGI 24/B122; ANPCyT 074/02Chaetophractus vellerosus and Zaedyus pichiy, was studied using traditional and landmark-based geometric morphometric methods. Adult specimens (C. vellerosus: 13 males, 16 females; Z. pichiy: 13 males; 10 females), coming from the surroundings of Bahía Blanca, Argentina, were used. Eight linear mandibular characters were measured by means of a digital calliper (0.01 mm) and traditional multivariate analysis were applied. For geometric morphometric analysis (Thin-plate spline), 16 homologous landmarks were digitalized on photographs of the labial side of the left hemimandible. With the Principal Component analysis a tendency to segregation of the species was observed, with mandibles taller and shorter in C. vellerosus than in Z. pichiy. The body length of the mandible and the height at the level of the last tooth were the main variables that discriminate both species and sexes, with percentages of correct classification higher than 75 % in all cases. The geometric analysis showed clear differences in shape between species. The superimposition of the consensus configuration indicated mandibles with wider body and ramus, and a more acute angle between both structures in C. vellerosus than in Z. pichiy. The intra-specific comparison between males and females showed differences in the mandible shape only in Z. pichiy. Particularly, the relative position of the mandibular body with respect to the ramus, tends to be more open in males than in females. Future studies may allow toelucidate if differences in the shape of the mandible are related with the masticatory mechanical efficiency in both species. Funded by SGCyT (UNS), PGI 24/B122; ANPCyT 074/02