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Burrow construction in the subterranean Ctenomys talarum (Rodentia: Ctenomyidae) primarily occurs by scratch-digging. In this study, we compared the limbs of an ontogenetic series of C. talarum to identify variation in bony elements related to fossorial habits using a morphometrical and biomechanical approach. Diameters and functional lengths of long bones were measured and 10 functional indices were constructed. We found that limb proportions of C. talarum undergo signif- icant changes throughout postnatal ontogeny, and no sig- nificant differences between sexes were observed. Five of six forelimb indices and two of four hindlimb indices showed differences between ages. According to discrimi- nant analysis, the indices that contributed most to dis- crimination among age groups were robustness of the humerus and ulna, relative epicondylar width, crural and brachial indices, and index of fossorial ability (IFA). Particularly, pups could be differentiated from juveniles and adults by more robust humeri and ulnae, wider epi- condyles, longer middle limb elements, and a proportion- ally shorter olecranon. Greater robustness indicated a possible compensation for lower bone stiffness while wider epicondyles may be associated to improved effec- tive forces in those muscles that originate onto them, compensating the lower muscular development. The gradual increase in the IFA suggested a gradual enhancement in the scratch-digging performance due to an improvement in the mechanical advantage of forearm extensors. Middle limb indices were higher in pups than in juveniles-adults, reflecting relatively more gracile limbs in their middle segments, which is in accordance with their incipient fossorial ability. In sum, our results show that in C. talarum some scratch-digging adapta- tions are already present during early postnatal ontog- eny, which suggests that they are prenatally shaped, and other traits develop progressively. The role of early dig- ging behavior as a factor influencing on morphology development is discussed. J. Morphol. 000:000-000 |
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