Histochemical and morphometric analyses of the musculature of the forelimb of the subterranean rodent Ctenomys talarum (Octodontoidea).

Histochemical and morphometric analyses were performed to characterize the fibre-type composition of two forelimb muscles of the South American subterranean rodent Ctenomys talarum. The studied muscles were the triceps lateralis, an extensor of the elbow, and the teres major, a flexor of the shoulder. It was found that these muscles had an elevated proportion of fast oxidative-glycolytic (FOG) fibres, and lower proportions of slow oxidative (SO) and fast glycolytic (FG) fibres. This composition probably qualifies the teres major and triceps muscles to perform the sustained effort required in tunnelling excavation. The results were discussed considering published data on fibre-type composition of mammals having different modes of life and digging behaviour. We here suggest that C. talarum has the potential of generating forces linked to rapid, powerful movements during sustained periods by means of an elevated proportion of FOG fibres, together with osteological changes that result in a great mechanical advantage of the forelimb muscles.