Aerobic respiratory costs of swimming in the negatively buoyant brief squid Lolliguncula brevis
Ian K. Bartol1,*,
Roger Mann2 and
Mark R. Patterson2
1 Department of Organismic Biology, Ecology, and Evolution, 621 Charles E. Young Drive South, University of California, Los Angeles, CA 90095-1606, USA and
2 School of Marine Science, Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062-1346, USA
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Fig. 1. Linear regressions of mean body angle of attack (degrees) versus swimming speed (mantle lengths s–1) for six size classes of Lolliguncula brevis: 2.9–3.9, 4.0–4.9, 5.0–5.9, 6.0–6.9, 7.0–7.9 and 8.0–8.9 cm dorsal mantle length, DML. Regression equations, P-values and r2 values are included for each size class.
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Fig. 2. Linear regressions of mean rate of fin beating (beats s–1) versus swimming speed (mantle lengths s–1) for six size classes of Lolliguncula brevis: 2.9–3.9, 4.0–4.9, 5.0–5.9, 6.0–6.9, 7.0–7.9 and 8.0–8.9 cm dorsal mantle length, DML. Regression equations, P-values and r2 values are included for each size class.
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Fig. 3. O2 consumption rates (µmol O2 h–1 g–1) of 19 Lolliguncula brevis (2.9–8.4 cm dorsal mantle length, DML) plotted as a function of swimming speed (mantle lengths s–1). Each data point is derived from the slope of percentage O2 saturation versus time curves recorded in the final 10 min interval of each speed trial. Linear or polynomial regression equations, r2 values and P-values are included in plots when a significant relationship was detected. As a result of limited data, linear or curvilinear relationships were not detected in some squid and, in these cases, data points were simply connected with lines. Mean rates of O2 consumption (µmol O2 h–1 g–1) for the three speed ranges are included for each squid (a, <0.5 DML s–1; b, 0.5–1.5 DML s–1; c, >1.5 DML s–1).
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Fig. 4. Vertical jet power, induced power, refilling power, parasite/profile power and total power requirements for a 4.4 cm dorsal mantle length (DML) and a 7.6 cm DML Lolliguncula brevis swimming over a range of speeds. Vertical jet power is the power required by the jet to keep the squid up in the water column, induced power is the power required by the fins to keep the squid up in the water column, refilling power is the power required to fill the mantle cavity, parasite/profile power is the power required to overcome drag on the body, fins and arms and total power is the sum of all the above power terms.
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Fig. 5. Gross cost of transport (COT) and efficiency curves for Lolliguncula brevis. (A) COT curves derived from active metabolic data for a 4.5 cm and a 7.5 cm dorsal mantle length (DML) squid. (B) COT curves derived from kinematic and force data for a 4.4 cm and a 7.6 cm DML squid. (C) Efficiency curves, which were determined from ratios of power output (based on kinematic and force data from the 4.4 and 7.6 cm DML squid) to power input (based on active metabolic rates from the 4.5 and 7.5 cm DML squid). See text for details of calculations.
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Fig. 6. O2 consumption rates (ml O2 kg–1 h–1) of various cephalopods plotted against swimming speed. Swimming speeds are expressed in (A) cm s–1 and (B) mantle lengths s–1. The 15 and 31 g Lolliguncula brevis in the figure correspond to the 5.3 and 7.5 cm dorsal mantle length (DML) squid, respectively, depicted in Fig. 3. These squid were selected as representative of this study because they were particularly cooperative and their O2 consumption rates were close to the mean O2 consumption rates for their respective size classes. Since Illex illecebrosus was considerably larger than L. brevis, its mass was adjusted to 30 g using the metabolic scaling equation: R=aMb, where R is metabolic rate (ml O2 kg–1 h–1), M is organism mass (kg), a is the mass coefficient and b is the mass exponent (–0.25) (O’Dor and Webber, 1986). For comparative purposes, O2 consumption rates for I. illecebrosus were extrapolated to slightly lower speeds than those studied. The mass of each organism and the temperature of the water within the respirometers are included in parentheses. Sources of the data are listed in the figure.
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Fig. 7. O2 consumption rates (ml O2 kg–1 h–1) of Lolliguncula brevis and various fishes plotted against swimming speed. Swimming speeds are expressed in (A) cm s–1 and (B) body lengths s–1. The 7.8, 15 and 31 g L. brevis in the figure correspond to the 4.8, 5.3 and 7.5 cm dorsal mantle length (DML) squid, respectively, depicted in Fig. 3. These squid were selected as representative of this study because they were particularly cooperative and their O2 consumption rates were close to the mean O2 consumption rates for their respective size classes. Squid mantle lengths (ML) were converted to body lengths (BL) using the equation BL=1.6ML derived from morphological measurements of L. brevis. The masses of menhaden and flounder (denoted with asterisks) were adjusted to 15 g using the equation: R=aMb, where R is metabolic rate (ml O2 kg–1 h–1), M is organism mass (kg), a is the mass coefficient and b is the mass exponent (–0.25) (O’Dor and Webber, 1986). Moreover, flounder oxygen consumption rate was converted to 25°C using data on the effects of temperature on the active metabolic rate of flounder (Duthie, 1982). Sources of the data are listed in the figure.
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© The Company of Biologists Ltd 2001
