A Note on the Structural Organization of the Cardiac Myofiber in Nautilus pompilius

摘要

The ultrastructure of the cardiac myofiber in Nautilus resemblesthat of bivalves more than the decapod cephalopods. The fiber is nonstriated, themitochondrial density is relatively small and the cristae poorly developed, andthe sarcoplasmic tubule system is either sparse or absent. These features suggestthat the Nautilus heart is not highly adapted to enhance the transport of largevolumes of oxygen to the tissues and that the adaptations found in the decapodsarose within the class Cephalopoda.