Choreographed swimming of copepod nauplii

Abstract

Small metazoan paddlers, such as crustacean larvae (nauplii), are abundant, ecologically important and active swimmers, which depend on exploiting viscous forces for locomotion. The physics of micropaddling at low Reynolds number was investigated using a model of swimming based on slenderbody theory for Stokes flow. Locomotion of nauplii of the copepod Bestiolina similis was quantified from high-speed video images to obtain precise measurements of appendage movements and the resulting displacement of the body. The kinematic and morphological data served as inputs to the model, which predicted the displacement in good agreement with observations. The results of interest did not depend sensitively on the parameters within the error of measurement. Model tests revealed that the commonly attributed mechanism of 'feathering' appendages during return strokes accounts for only part of the displacement. As important for effective paddling at low Reynolds number is the ability to generate a metachronal sequence of power strokes in combination with synchronous return strokes of appendages. The effect of feathering together with a synchronous return stroke is greater than the sum of each factor individually. The model serves as a foundation for future exploration of micropaddlers swimming at intermediate Reynolds number where both viscous and inertial forces are important.

Sub-Riemannian geometry, Hamiltonian dynamics, micro-swimmers, copepod nauplii and copepod robot

“…It can be observed that angular excursions for this nauplius increased over the first three cycles, especially for antenna A1 for which it nearly quadrupled. As explained in [29], there is strong agreement between the experimental data and the predicted displacement, particularly for the first 20 ms, validating the basic approximations of the model. It can be seen on the bottom picture that the displacement per cycle is increasing which is a result of the increases in amplitude of antenna A1, this suggest that the amplitude of a single appendage excursion can impact the displacement of the nauplius.…”

“…It is clearly observed that while the abnormal curve is Fig. 19 Scanning electron microscopy image of a larval copepod, courtesy of Jenn Kong and reproduced from [29]. Copyright retained by the originator a concatenation of the edges of the triangular prism of constraints, the observed period strokes belongs to the inside and reflect the, possibly self-imposed, contraints on the appendage angles.…”

“…Toward the construction of simple robots, we restrict ourselves to n-links swimmers for which the slender body approximation is valid [34]. We will focus on the copepod swimmer which has recently gained interest in the literature, see [29,41]. The mathematical model described in [41] consists of n-pairs of symmetric (slender) legs with the body being reduced to a small sphere with radius r. The copepod zooplankton and the associated micro-robot are represented in Figs.…”

“…Experimental observations were conducted on a larval copepod (stage 5 nauplius) by the authors of [29]. On Fig.…”

A numerical approach to the optimal control and efficiency of the copepod swimmer

“…Recently a new model was developed to mimic the locomotion of larval copepods, an abundant type of zooplankton thriving in the ocean [15], [17]. The simplest form of the model, hereafter referred to as the copepod swimmer, is a symmetric body consisting of two pairs of legs, with the pairs making respectively an angle θ 1 and θ 2 with respect to the displacement direction Ox (see Fig.1).…”