Bite force in South American caviomorph rodents: influence of size and niche

FEDERICO BECERRA; ALEJANDRA ISABEL ECHEVERRÍA; ALDO IVÁN VASSALLO; ADRIÀ I. CASINOS

Paris

Encuentro; 5th International Meeting on Cranio cervical Systems in Vertebrates; 2011

Ctenomys is a very specious genus of octodontoidea. However, all the species are adapted to the subterranean life, using both forelimbs and incisors as digging tools, the latter being used when animals face hard soils and fibrous roots. Given the large range of body mass among the species and the variation of soils where they live, important differences in bite forces could be expected. Up to date, bite forces have been recorded in two species of Ctenomys (C. australis, C. talarum) and in several other epigean species of the group. Bite forces were regressed to body mass, incorporating published values from different species of mammals. The allometric coefficient obtained with this interspecific sample was about 0.66, very different from that obtained in an ontogenetic study on bite forces in C. talarum, in which case that coefficient was not statistically different from 1. Although in this species bite forces were significantly higher in adult males than in adult females, this was not the situation in juveniles and pups. Moreover, the respective allometric coefficients calculated with both ontogenetic series of males and females of C. talarum were not significantly different either. In order to investigate the muscular basis of the bite force, the mandibular adductor muscles (different heads of the masseter, the pterygoideus, and the superficialis) were dissected, and the maximum forces that these muscles can exert in isometric conditions were calculated. Comparisons with data from C. australis are carried out.