The energetics of Calanus euxinus : locomotion, filtration of food and specific dynamic action
AbstractThe effect of locomotor activity on respiration rate was studied in the food-deprived copepod Calanus euxinus tethered to a force sensor. The power generated by mouth appendages during cruising locomotion, with a frequency of 40 Hz, accounted for 0.026 and 0.0031 W for metabolic and mechanical processes, respectively. To overcome total hydrodynamic drag during foraging with a mean swimming speed of 3.2 cm s −1 , the copepods need 0.4 × 10 −3 W, equating to 1.3% of total metabolism. The losses of mechanical energy for body propulsion amounted to 1.3 × 10 −3 W, whilst the cost of feeding current generation run up to 1.8 × 10 −3 W, or 58% of the total. Changing of locomotor activity and respiration rate during feeding was examined separately in tethered and free-swimming copepods. At algal concentration of ∼300 μg C L −1 , the magnitude of specific dynamic action (SDA) averaged 1.2 ± 0.44 nL O 2 μg C −1 h −1 in copepodites V and females, with similar moving activity before and during feeding. The contribution of SDA into total metabolism varied from 23 to 85% in C. euxinus with low activity level and constituted only 10% in active animals. In starved copepods, with low locomotor activity, feeding events stimulated the increase in frequency and total duration of locomotion which resulted in elevated energy expenditure enhancing the ‘apparent SDA’.