M. E. DeMont (Supervisor, Biology)
W.R. Quinn (Engineering)
J.P. Quinn (Mathematics)
R.K. O’Dor (Biology, Dalhousie)
E.C. Oguejiofor (Engineering)

The kinematics and dynamics of squid locomotion were analyzed using high speed video recording, advanced image analysis and theoretical hydrodynamics. Long-finned squid, Loligo pealei, swimming in flumes at the Woods Hole Oceanographic Institute were video recorded at frame rates of 125 to 250 Hz. From each frame of an acquired swimming sequence, the squid outline was digitized by a computer-based edge detection algorithm. These outline data were used to calculate kinematic and dynamic information concerning the motion of the squid through its fluid environment as well as body deformations. The outlines of the recorded squid were also used to determine the fluid flow over the surface of swimming squid and thereby the hydrodynamic forces acting in squid locomotion were calculated.

The analysis of squid locomotion has resulted in a detailed description of the coordination and dynamic contributions of locomotory structures in squid. Variable patterns of fin and jet activity were observed. Waves of contraction and variations in the mantle deformation at varying swimming speeds have been observed and quantified. The pressures involved in producing the jet used by squid for propulsion were calculated and used to determine jet thrust and the dynamic requirements of the squid musculature to produce such pressures. An alternate method of calculating jet propulsive efficiencies for squid is also presented in this thesis. The hydrodynamic analysis preformed in this investigation has resulted in a detailed picture of the unsteady fluid dynamics at play in squid locomotion. The technique of the determination of these forces is described in this thesis and could be easily implemented by others in the field. The action of the acceleration reaction, or added mass effect, is presented. Furthermore, the characteristics of the squid body form and locomotory apparatus, which make them finely adapted to their fluid environment, are discussed. The determination of the major forces involved in squid locomotion has resulted in the calculation of the in vivo muscle behavior during the jet period of the squid.

Several important conclusions arise from this investigation of squid locomotion. First, the hydrodynamic forces acting on the squid, aside from the fins, have been shown to be practically negligible in the balance of forces during sustained swimming. It is suggested that the action of the fins, and forces due to refilling, are most significant in decelerations during swimming. Second, waves of contraction do occur on the mantle of swimming squid and may enhance hydrodynamic efficiency. Third, the use of Froude efficiency for calculating propulsive efficiencies in jet propelled organisms without continuous forward intake mechanisms is concluded to be invalid, and the equation for propulsive efficiency in rockets is suggested as the appropriate equation. Fourth, the contribution of intramantle pressure to the forces necessary to be produced by the circular muscles in jetting was found to outweigh external fluid forces, mantle wall inertia and tissue visco-elasticity to such a degree that intramantle pressure alone may be used to estimate in vivo muscle behavior at migratory swimming speeds. Finally, this investigation concludes that in vivo muscle behavior is dependent on the locomotor system in which the muscle is acting and that muscle behavior information acquired from excised tissue does not give an accurate picture of in vivo muscle behavior. Therefore, models of muscle behavior in living systems need to be based on in vivo muscle behavior determinations, as found in this work. The similarity between the locomotor system of squid and hearts suggest the application of this investigation’s findings to the study of cardiac function.

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Edwin DeMont, Associate Professor
Biology Department, St. Francis Xavier University
P.O. Box 5000, Antigonish, Nova Scotia, B2G 2W5 Canada
Voice 902-867-5116 FAX 902-867-2389 edemont@stfx.ca
April 29, 1998