O'Dor, Ronald K.
Permanent URI for this collectionhttps://hdl.handle.net/10222/22310
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Item Open Access Costs of locomotion and vertic dynamics of cephalopods and fish(2000-12) Webber, DM; Aitken, JP; O'Dor, R. K.The world's oceans are three-dimensional habitats that support high diversity and biomass. Because the densities of most of the constituents of life are greater than that of seawater, planktonic and pelagic organisms had to evolve a host of mechanisms to occupy the third dimension. Some microscopic organisms survive at the surface by dividing rapidly in vertically well mixed zones, but most organisms, small and large, have antisinking strategies and structures that maintain vertical position and mobility. All of these mechanisms have energetic costs, ranging from the "foregone metabolic benefits" and increased drag of storing high-energy, low-density lipids to direct energy consumption for dynamic lift. Defining the niches in the mesopelagic zone, understanding evolution, and applying such ecological concepts as optimal foraging require good estimates of these costs. The extreme cases above are reasonably well quantified in fishes, but the energetic costs of dynamic physiological mechanisms like swim bladders are not; nor are the costs of maintaining vertical position for the chief invertebrate competitors, the cephalopods. This article evaluates a matrix of buoyancy mechanisms in different circumstances, including vacuum systems and ammonium storage, based on new data on the metabolic cost of creating buoyancy in Sepia officinalis.Item Open Access The Forces Acting on Swimming Squid(1988) O'dor R K1. Analysis of cine fils and intramantle pressure records for squid Loligo opalescens Berry swimming in a tunnel respirometer provided estimates of all the forces acting in the horizontal and vertical planes for swimming speeds from 0.1 to 0.5 m s-1. 2. Different speeds used different gaits; fin thrust was only important below 0.2 m s-1, 'anaerboic' circular muscles were recruited only at supracritical speeds, and hyperinflation caused by contraction of the radial muscle was not seen in steady swimming. 3. The extent, rate and frequency of contraction of the obliquely striated circular muscles varied little with speed, and jet thrust was matched to speed primarily by active pressure control through adjustments in the size of the funnel orifice. 4. Hydrodynamic lift production to compensate for negative buoyancy during enforced horizontal swimming in the tunnel required 30-90% of the total force over the speed range studied and appears less efficient than direct use of jet thrust. This suggests a new rationale for 'climb-and-glide' swimming which reduces previous estimates of the gross cost of transport for squid under natural conditions by at leas 35%, with no loss of speed. 5. The cost of accelerating water into the mantle of a squid moving at high speed appears to have been underestimated in previous studies. A simulation of a series of escape jets predicts a maximum speed of 8 body lengths s-1 (1.4 m s-1), reached after only two jets, because of the high deceleration during refilling.Item Open Access Circulation time, blood reserves and extracellular space in a cephalopod(1984) O'Dor, R. K.; Wells, MJOctopus vulgaris Cuvier has a fully enclosed blood system that includes large blood sinuses behind the eyes and around the gut. It would be useful to know the mean circulation time, the minimal number of heartbeats needed for blood to return to the hearts, and/or the extent to which the sinuses constitute a reserve of blood which can be mobilized in times of stress. Experiments are reported in which aortic pulse and pressure are recorded using a cannula following injection of inulin.