The Biomechanics of the Arteries of Nautilus, Nototodarus, and Sepia

Abstract

The mechanical properties of the dorsal aorta of three cephalopod mollusks, Nautilus pompilius, Nototodarus sloani, and Sepia latimanus, were investigated by in vitro inflations of isolated arterial segments. As expected, all three arteries exhibit nonlinear, J -shaped stress-extension curves, and all are highly extensible in the circumferential direction. Differences in longitudinal extensibility appear to be correlated to specific features of the tissue architecture. The squid, Nototodarus, and to a lesser extent the cuttlefish, Sepia, arteries are reinforced longitudinally with a dense layer of longitudinally oriented elastic fibers. Analysis of the form of the incremental wall stiffness data for Nautilus and Nototodarus suggests that the in vivo blood pressures for these animals fall in the ranges 20-60 cm H20 and 100-200 cm H20, respectively. Nautilus has a thinwalled, low-pressure arterial system that is in keeping with its relatively limited locomotory capabilities. Nototodarus has a high-pressure, thick-walled circulation that is required to support the high-speed, aerobic locomotion generally common in squid. Analysis of pressure wave velocities for these arteries indicates that the Nautilus circulatory system contains a true Windkessel whereas it appears possible that wave propogation effects may make a relatively minor contribution to the hemodynamics of Nototodarus.