Ontogeny of bite force and incisor strength indicator in tuco tucos (Ctenomys talarum; Rodentia; Caviomorpha)

VASSALLO, AI; BECERRA, FEDERICO; ECHEVERRÍA AI; BUEZAS, GUIDO; CASINOS, ADRIA

Barcelona

Simposio; 10th International Congress of Vertebrate Morphology; 2013

Society of Vertebrate Morphology

Structural adaptations undergo changes during ontogeny that sometimes entail different functional capabilities. The behaviour of organisms at each stage of development is largely constrained by this fact. Rodents have long, ever growing incisors for gnawing, and a powerful jaw adductor musculature. The incisors are sufficiently long relative to their basal diameter to be affected significantly by bending stresses. This is particularly true in the subterranean genus Ctenomys that uses its long and procumbent incisors during the excavation of galleries. We measured bite force in individuals of different age using a force transducer. In these individuals, incisor width and depth were measured, using a digital caliper, to assess incisor´s section modulus, considering incisor cross-section as an ellipse. Incisor length was also measured. A strength indicator (S) was calculated as S = incisor section modulus / (biting force)(incisor length). We found that, for both sexes, ontogenetic biting force scales to body mass with positive allometry (allometric coefficient 0.90 and 0.95; females and males respectively). However, a two-way ANOVA showed non-significant differences in S either between sexes or among age classes (pups; juveniles; adults). This result indicates equal structural capacity in the gnawing/excavatory apparatus during the ontogeny of the species. This fact correlates well with the observation that pups and juveniles of C. talarum incorporate solid foods shortly after birth (7-10 days old), and are able to dig early in life, at 18-20 days old.