The Swimming of Cuttlefish

Abstract

IT may not perhaps be generally realised that the common cuttlefish, Sepia officinalis, uses its siphon for slow swimming in all directions, as well as for the more violent backward leaps. We recently had an opportunity of watching the behaviour of cuttlefish which were swimming at eye level and above our heads in one of the large tanks of the Plymouth aquarium. We were rather surprised to notice that while moving slowly forwards with its fins undulating, the cuttlefish had its siphon curved back ventrally and was assisting its forward motion by emitting gentle squirts of water (Fig. 1, A). If the cuttle wished to turn to one side it would point its siphon opening to the opposite side and squirt a little more violently (Fig. 1, B). In fact, for all its general slow movements the siphon appeared to be used, the undulations of the fins merely keeping the motion continuous and preserving the balance. In the quick backwards swimming the fins were depressed along the side. The siphon was extended about an inch and a half and coxild be pointed in any direction.