The fluid dynamics of swimming by jumping in copepods
MetadataShow full item record
KeywordCopepod jump; Viscous vortex ring; Impulsive stresslet; Impulsive Stokeslet; Hydrodynamic camouflage; Non-dimensional ‘jump number’
Copepods swim either continuously by vibrating their feeding appendages or erratically by repeatedly beating their swimming legs resulting in a series of small jumps. The two swimming modes generate different hydrodynamic disturbances and therefore expose the swimmers differently to rheotactic predators. We developed an impulsive stresslet model to quantify the jump-imposed flow disturbance. The predicted flow consists of two counterrotating viscous vortex rings of similar intensity, one in the wake and one around the body of the copepod. We showed that the entire jumping flow is spatially limited and temporally ephemeral owing to jump-impulsiveness and viscous decay. In contrast, continuous steady swimming generates two well-extended long-lasting momentum jets both in front of and behind the swimmer, as suggested by the well-known steady stresslet model. Based on the observed jump-swimming kinematics of a small copepod Oithona davisae, we further showed that jump-swimming produces a hydrodynamic disturbance with much smaller spatial extension and shorter temporal duration than that produced by a same-size copepod cruising steadily at the same average translating velocity. Hence, small copepods in jumpswimming are much less detectable by rheotactic predators. The present impulsive stresslet model improves a previously published impulsive Stokeslet model that applies only to the wake vortex.
Author Posting. © The Authors, 2010. This is the author's version of the work. It is posted here by permission of Royal Society for personal use, not for redistribution. The definitive version was published in Journal of the Royal Society Interface 8 (2011): 1090-1103, doi:10.1098/rsif.2010.0481.
Showing items related by title, author, creator and subject.
Woods, Nicholas W. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2013-06)This thesis explores the role that the circulation in the Gulf of Maine (GOM) plays in determining the distribution of dense aggregations of copepods. These aggregations are an important part of the marine ecosystem, ...
Kiørboe, Thomas; Jiang, Houshuo; Colin, Sean P. (2010-06)Zooplankton feed in either of three ways: they generate a feeding current, cruise through the water, or they are ambush feeders. Each mode generates different hydrodynamic disturbances and hence exposes the grazers ...
Drawings and descriptions of some deep-sea copepods living above the Guaymas Basin hydrothermal vent field Copley, Nancy J.; Wiebe, Peter H. (Woods Hole Oceanographic Institution, 1990-04)This report includes brief descriptions and illustrations of some of the copepods found in two bathypelagic MOCNESS samples. The MOCNESS was towed horizontally at an altitude of 100-200 m above the bottom in waters 1900 ...