Mechanochemical coupling in flagella. IV. Absence of coupling between metabolism and motility in Chaetopterus...

The metabolic rate of suspensions of spermatozoa from the annelid worm, Chaetopterus, does not change significantly when the viscosity of the suspension is increased by the addition of methyl cellulose. At high viscosities, where the spermatozoa swim with about 1/3 the normal beat frequency and 1.5-1.8 times the normal bend angle, the calculated power output against external viscous resistances increases to 4-5 times its normal value. This large increase in power output can be accommodated without an increase in metabolic rate only if internal viscous resistances to flagellar bending are relatively low.