The orientation of muscle fibres in the tail musculature ofRana temporaria tadpoles (Amphibia, Anura)

Summary

Shape of the myosepts and arrangement of the muscle fibres were recorded in the lateral musculature of the tail ofRana temporaria embryos and larvae. Well developed myomeres are present as early as st. 18–19. The main characteristics—ie. those related to functional properties—of myoseptal shape as well as of muscle fibre arrangement, remain unchanged throughout further development until degeneration of the tail occurs during metamorphosis. The rather simple myoseptal shape observed inRana—as compared to the multiple cone-form observed in most fishes—shows a close agreement to hypothetical myosept models described in papers by Jarman (1961), van der Stelt (1968) and Willemse (1966). The muscle fibres in the m. lateralis ofRana are arranged in trajectorial patterns that show a close similarity to the trajectorial patterns observed in “typical teleosts”. Both arrangements agree with trajectorial models based on the mathematical analyses of Alexander (1968).

Neurulas anaesthetized with 1:10000 MS-222 and exposed up two weeks to this anaesthetic developed the same shape of the myosepts and arrangement of muscle fibres as in controls. Thus even the details of the function-related features of the myomere structure develop without functioning. In this field possible feedback meachisms are either not affected by anaesthesia or do not exist at all.