Efficient nematode swimming in a shear thinning colloidal suspension

Area of Science:

• Biophysics
• Fluid Dynamics
• Nematology

Background:

• Understanding organismal locomotion in complex fluids is crucial for ecological and biomedical applications.
• Caenorhabditis elegans (C. elegans) is a model organism for studying biological movement.
• Non-Newtonian fluids, like shear-thinning suspensions, present unique challenges for swimmers.

Purpose of the Study:

• To investigate the swimming behavior of C. elegans in shear-thinning colloidal suspensions.
• To quantify changes in swimming speed and efficiency as a function of fluid properties.
• To elucidate the mechanisms behind enhanced nematode locomotion in non-Newtonian media.

Main Methods:

• Experimental observation of C. elegans swimming in varying concentrations of a shear-thinning colloidal suspension.
• Measurement of worm swimming speed and stroke dynamics.
• Analysis of fluid rheology and its relationship to worm kinematics.

Main Results:

• At approximately 8% concentration, the shear-thinning suspension caused a 12% increase in average swimming speed compared to Newtonian fluids.
• Swimming efficiency significantly improved with increasing suspension concentration in the shear-thinning regime.
• Worm stroke patterns adapted, featuring faster, larger head strokes correlated with a drop in local fluid viscosity.

Conclusions:

• C. elegans exhibits enhanced swimming performance and efficiency in shear-thinning fluids.
• The nematode's adaptive stroke dynamics are key to overcoming high drag in these complex media.
• Findings provide novel insights into nematode navigation and survival in natural, non-Newtonian environments.