Burrowing dynamics of aquatic worms in soft sediments

Abstract

We investigate the dynamics ofLumbriculus variegatusin water-saturated sediment beds to understand limbless locomotion in the benthic zone found at the bottom of lakes and oceans. These slender aquatic worms are observed to perform elongation–contraction and transverse undulatory strokes in both water-saturated sediments and water. Greater drag anisotropy in the sediment medium is observed to boost the burrowing speed of the worm compared to swimming in water with the same stroke using drag-assisted propulsion. We capture the observed speeds by combining the calculated forms based on resistive-force theory of undulatory motion in viscous fluids and a dynamic anchor model of peristaltic motion in the sediments. Peristalsis is found to be effective for burrowing in noncohesive sediments which fill in rapidly behind the moving body inside the sediment bed. Whereas the undulatory stroke is found to be effective in water and in shallow sediment layers where anchoring is not possible to achieve peristaltic motion. We show that such dual strokes occur as well in the earthwormEisenia fetidawhich inhabits moist sediments that are prone to flooding. Our analysis in terms of the rheology of the medium shows that the dual strokes are exploited by organisms to negotiate sediment beds that may be packed heterogeneously and can be used by active intruders to move effectively from a fluid through the loose bed surface layer which fluidizes easily to the well-consolidated bed below.

Emergent Collective Locomotion in an Active Polymer Model of Entangled Worm Blobs

“…In our current model, for simplicity, we have implemented self-propulsion of worms as a tangential force with constant magnitude, without consideration of the medium through which the worms are moving. In reality, worms harness friction to propel themselves, employing a combination of peristaltic elongation and contraction, undulatory strokes, and helical movements to crawl on surfaces, burrow through sediments, or swim through water [18,47]. While our goal in this paper is to develop a parsimonious and generalizable description of worm behavior, accounting for hydrodynamics and friction can provide a more complete analysis of a specific biological system.…”

Pivot burrowing of scarab beetle (Trypoxylus dichotomus) larva

“…The soil is home to many organisms, and how they move through soil has been studied in several species (e.g., rats, lizards, snakes, nematodes, eels, spiders, ants, earthworms) by analyzing the shape of their burrows or/and using X-ray scanning technology [1][2][3][4][5][6][7][8][9][10][11] . Among them, earthworms have attracted much attention as a research model because they can burrow through soil without appendages, and their dynamics have recently been elucidated via an observation system using transparent superabsorbent polymers 12 . Furthermore, applications of these excavation techniques are being developed [13][14][15] .…”

Pivot burrowing of scarab beetle (Trypoxylus dichotomus) larva

“…[1][2][3][4][5][6][7][8][9][10][11] Among them, earthworms have attracted much attention as a research model because they can burrow through soil without appendages, and their dynamics have recently been elucidated via an observation system using transparent superabsorbent polymers. 12 Furthermore, applications of these excavation techniques are being developed. [13][14][15] Earthworm morphology seems to be suitable for burrowing in terms of the drag force from the soil, as their trunk is narrow compared to their body length.…”