Energy Metabolism of Nautilus Swimming Muscles

Abstract

Increasing attention is being paid to the energy metabolism of cephalopods, particularly to the metabolic pathways used to provide ATP for muscle contraction during locomotion (for recent reviews, see Hochachka et al., 1983; Storey and Storey, 1983). Extending these studies to Nautilus has generated considerable interest among comparative biochemists for a variety of reasons. As the only extant genus of the once abundant and highly diverse externally shelled cephalopods, Nautilus offers a unique opportunity for gaining information about metabolic organization in an ancient lineage that has been separated since Paleozoic times from those that lead to other modern cephalopods. In addition, most studies of energy metabolism have been carried out with the highly active squids and cuttlefishes. Nautilus, with lower oxygen demands and a less efficient oxygen delivery system (Johansen et al., 1978; Redmond et al., 1978), provides an interesting contrast of cephalopod metabolism in "slow motion." Further, because correlations exist between the intensity and duration of locomotion and biochemical properties of the muscles involved in propulsion, comparative studies utilizing a range of cephalopods enable predictions to be made about locomotory behavior in animals such as Nautilus for which direct observations of swimming in nature are limited.