  Swimming by shape changes at low Reynolds number is widely used in biology
and understanding how the efficiency of movement depends on the geometric
pattern of shape changes is important to understand swimming of microorganisms
and in designing low Reynolds number swimming models. The simplest models of
shape changes are those that comprise a series of linked spheres that can
change their separation and/or their size. Herein we compare the efficiency of
three models in which these modes are used in different ways.
