Influence of temperature on swimming performance and respiration rate of the cold-water cyclopoid copepod Cyclops vicinus

Little is known on the swimming activity and respiration rate of the cyclopoid copepod Cyclops vicinus. Here, the swimming speed and respiration rate of C. vicinus were measured at different temperatures using a high speed (up to 1200 frames per second) camera and a closed-system respirometry, respectively. For cruise and escape swimming, log-linear relationships were found between temperature (range 1–22 °C) and duration, speed, and frequency of locomotor acts, respectively. The respiration rate of immobilized and active individuals showed log-linear relationships with temperature (range of 2–20 °C) and a thermal coefficient Q10 ≈ 2 was found. The maximum respiration rate of swimming females was 7.8 and 6.4 times higher than that of immobilized individuals at 2 and 20 °C, respectively. To better understand how temperature affects the energy efficiency of copepod swimming, the mechanical energy of movement was estimated from sswimming speed and the metabolic energy was estimated from the amount of oxygen consumed during swimming. Linear relationships between swimming speed and mechanical and metabolic energy, respectively, were found at all experimental temperatures. At 20 °C, the maximum mechanical and metabolic energy costs for movement was 15.2 × 10−5 and 37.7 × 10−4 J h−1, respectively. In the range of 2–20 °C, the mechanical energy attributed to swimming represented only a small portion (4.0–8.2%) of the total metabolic energy. Cold-water specialization probably limited the increase of the swimming speed of C. vicinus at high temperatures compared to that of warm-water adapted species.