Unexpected Regularity in Swimming Behavior of Clausocalanus furcatus Revealed by a Telecentric 3D Computer Vision System

Abstract

Planktonic copepods display a large repertoire of motion behaviors in a three-dimensional environment. Two-dimensional video observations demonstrated that the small copepod Clausocalanus furcatus, one the most widely distributed calanoids at low to medium latitudes, presented a unique swimming behavior that was continuous and fast and followed notably convoluted trajectories. Furthermore, previous observations indicated that the motion of C. furcatus resembled a random process. We characterized the swimming behavior of this species in three-dimensional space using a video system equipped with telecentric lenses, which allow tracking of zooplankton without the distortion errors inherent in common lenses. Our observations revealed unexpected regularities in the behavior of C. furcatus that appear primarily in the horizontal plane and could not have been identified in previous observations based on lateral views. Our results indicate that the swimming behavior of C. furcatus is based on a limited repertoire of basic kinematic modules but exhibits greater plasticity than previously thought.

Does prey elemental stoichiometry influence copepod movement over ontogeny?

“…The fraction of time spent swimming, f swim , was simply the fraction of intervals over which movement was detected. We then calculated speed while swimming, v swim , according to Bianco et al (), …”

Plankton community structure and connectivity in the Kimberley-Browse region of NW Australia

“…Mazzocchi and Paffenh€ ofer (1999) demonstrated that Clausocalanus furcatus foraged by swimming actively to explore the surrounding water to locate prey, rather than produce a feeding current as is common amongst suspensionfeeding calanoid copepods. Clausocalanus is adapted to low food concentrations, and can suspend active swimming to conserve energy when required (Bianco et al, 2013). Consequently, it is tempting to speculate that the absence of Clausocalanus species from the inshore regions of the Kimberley coast is because high turbulence interferes with their foraging strategy by disrupting search patterns during active swimming.…”

Analysis of self-overlap reveals trade-offs in plankton swimming trajectories

“…3C), increasing the self-overlap ( Fig. 5A) and reducing the average swimming speed [19]. Interestingly, this change in the kinematics is often correlated to a change in the swimming patterns, going from a fast cruising to a swim-and-sink behaviour, hence consistently increasing the amount of volume overlap for all the trajectories (Fig.…”

“…3A), and a set of regular geometric patterns with alternating swimming and sinking phases under food depleted conditions ( Fig. 3C) [19]. In contrast, T. stylifera, both females and males, perform only a cruising behaviour with regular loops in the horizontal plane ( Fig.…”

“…In fact, although the swimming is correlated on larger scales, swimand-sink trajectories reveal that organisms were repeatedly exploring the same volume of water and the motion is then characterized by larger self-overlap and less efficient encounter rates. This result combined with the low speed observed during the swim-and-sink pattern [19] would drastically reduce the encounter rate predicted by Eq. 3.…”