Muscles à striation oblique et à striation transversale chez les Annélides Polychètes

Abstract

Abstract Ohlique- and cross-striated muscles in polichaetes. Most annelids, chiefly polychaetes, have muscles of oblique double striation or of helical striation. Yet special evolutionary processes may induce profound changes in the structure of muscles in two polychaete families, the Syllidae and Nereidae. At time of reproduction they can undergo somatic metamorphoses termed stolonisation and epitoky. Many of their muscles de-differentiate partly or wholly, and then they redifferentiate into epitokous fibres, characterized by thick, shorter filaments of smaller diameter, and rich in mitochondria and glycogen. Besides, there are some examples of muscle fibres non-helical in type worth investigating, for they show, first, an absence of a direct relation between phylogeny and fibre type (obliquely or transversely striated, or smooth), and, secondly, an absence of transitions between smooth and cross-striated fibres (the proventriculus in Syllidae), and between the latter and fibres of oblique simple striati...