Tangling of Tethered Swimmers: Interactions between Two Nematodes

Abstract

The tangling of two tethered microswimming worms serving as the ends of "active strings" is investigated experimentally and modeled analytically. C. elegans nematodes of similar size are caught by their tails using micropipettes and left to swim and interact at different separations over long times. The worms are found to tangle in a reproducible and statistically predictable manner, which is modeled based on the relative motion of the worm heads. Our results provide insight into the intricate tangling interactions present in active biological systems.

Micropipette force sensors for in vivo force measurements on single cells and multicellular microorganisms

“…Finally, we used two micropipettes (not force-calibrated) to hold two swimming nematodes close together in an attempt to probe their hydrodynamic interactions and collective motion. Instead, it turned out that the bodies of the tail-tethered, swimming nematodes overlapped, causing them to form fascinating active tangles (Figure 1c), which we described with an analytical model [60]. The great versatility of MFS enabled a very diverse set of questions to be investigated with micropipettes of many different cantilever designs (bottom panel of Figure 1; two and three straight corner bends in two or three dimensions) and spring constants (k = 1-10 nN/µm in the bending and swimming projects, k = 60-350 nN/µm in the crawling study), all of which were designed and made by the (under)graduate students in the lab.…”

“…(c) The interaction forces between swimming microorganisms can be directly measured with MFS by bringing the tail-tethered swimmers close together. In this experiment, the nematodes formed different, active tangles instead of swimming collectively[60]. Basics of the micropipette design.…”

Flow analysis of the low Reynolds number swimmerC. elegans

“…Recently C. elegans has been used extensively as a model system for experimental studies of propulsion, particularly at low Reynolds number, due to its simple planar swimming gait and size [9][10][11][12][13][14][15]. The nematode generates planar bending waves through contractions of its ventral and dorsal muscles, producing a quasi-two-dimensional (2D) traveling sine wave along its body [10,16,17].…”

“…At around 1 mm in length and 75 μm in diameter, C. elegans is significantly larger than the majority of low-Re undulatory swimmers, enabling high-resolution reconstruction and analysis of planar flow fields from particle tracking data. The resulting flow fields can be used to probe properties of both the swimmer and fluid, providing new insights into the physics of undulatory propulsion [11][12][13][14][15][18][19][20]. However, despite exhibiting a planar swimming stroke, the flow around C. elegans has a complex three-dimensional structure ( Fig.…”

Editorial: Soft Matters

“…(a) Gravity driven instabilities in polyacrylamide gels (adapted from [19]). (b) Two tangled C. elegans worms (reproduced from [20]). (c) Phase separation of clockwise and anticlockwise rotating spinners (adapted from [21]).…”