Présence de fibres striées transversalement et d'agrégats tubulaires intrasarcoplasmiques dans le prostomium de Magelona papillicornis (Annélide Polychète)

Abstract

The prostomium of the polychaetous annelid Magelona papillicornis contains a very well developed musculature formed of narrow, transversely striated fibers. These fibers are characterized by irregular A bands, discontinuous and winding Z lines, absence of a T system, and sarcoplasmic reticulum (SR) with longitudinal tubules anastomosing in the I bands. In some fibers the SR also develops aggregates of tubules in the non-contractile sarcoplasm. The occurrence and characteristics of these fibers, and specially the presence of aggregates of tubules are discussed in relation to the role of the prostomium in burrowing.