Locomotion

Cephalopods are capable of a variety of modes of locomotion, including fin swimming, jetting, walking and in the case of some squid (Teuthoidea: Onycoteuthidae) even flying (they break the water surface during fast jetting, to escape from predators, and can glide, like flying fish, for up to 50m) (Ruppert et al. 2004).

Jetting is the usual form of locomotion in most cephalopods, including I. notoides (personal observation). There are two types of jetting, fast and slow. Slow jetting uses contractions of the circular muscles of the mantle to create a water current that flows into the mantle cavity through the inhalant siphon, and out through the funnel, propelling the animal in the opposite direction. Fast jetting involves use of the radial muscles, as well as the circular muscles, which work together to hyperextend the mantle cavity, allowing it to hold more water than during slow jetting, and then create positive pressure in the mantle cavity so that water escapes from the funnel in a forceful jet (Ruppert et al. 2004).

I. notoides was observed in the lab using jetting, as well as its posterior pair of fins for locomotion.

A. Side view of I. notoides showing funnel protruding from the ventral mantle cavity. B. The posterior dorsal mantle of I. notoides, viewed from above, showing the paired fins. Photographs by Samantha Reynolds