Swimming behavior and energy metabolism of the calanoid copepod invader Sinodiaptomus sarsi

The appearance of invasive species threatens the integrity of aquatic ecosystems. Much is known about dispersal and introduction mechanisms while little is known on the biological properties of invasive species, such as behavior and energy efficiency, allowing them to successfully colonize new environments and compete with native species. This study examines the functional features of the Asian invasive copepod Sinodiaptomus sarsi (Rylov, 1923) that has invaded Europe since 2016. We focused on the energy metabolism and kinematic parameters of the main swimming types (i.e., gliding, hovering, small relocation jumps, and the escape reaction) of females and males of S. sarsi. Based on the above parameters, the mechanical energy for swimming and the respiration energy needed for movement were calculated. Females and males spend up to 95% of time hovering and slowly gliding at a speed of up to 0.5 cm s⁻¹. During the remaining time, the average swimming speed was 8 cm s⁻¹ by small jumps. In contrast, the average speed was 42 cm s⁻¹ during escape swimming. Non-ovigerous females moved faster than ovigerous females during all relocation swimming types except for upward gliding. While performing small jumps with a frequency of 0.79 Hz, the respiration rate of active non-ovigerous females (0.32 ± 0.03 µg O₂ ind⁻¹ h⁻¹) was 2.1 times higher than that of anesthetized individuals. The respiration energy associated with movement was 2.6 * 10⁻³ J h⁻¹, while the total mechanical energy was only 4.2% of this value. The low energy cost of feeding along with the high speed of locomotion may explain the success of this Asian invader in European waters.