MICROTUBULE SLIDING IN REDUCED-AMPLITUDE BENDING WAVES OF CIONA SPERM FLAGELLA - BENDING WAVES ATTENUATED BY LITHIUM

The distinct damped, or attenuated, bending pattern observed when demembranated sperm flagella of the tunicate, Ciona, are reactivated in the presence of 2 mM Li+ has been analysed in detail. In these patterns, bends are initiated at the base of the flagellum, but die out after they start to propagate along the flagellum, so that little or no bending is seen in the distal half of the flagellum. A quantitative descriptive analysis shows that the distinctive feature of this attenuation of bending wave amplitude is an asymmetric interbend decay, or slippage, occuring, on average, only at the transitions between a reverse bend and the preceding principal bend. This attenuation is combined with a significant amount of synchronous sliding in the distal half of the flagellum and a decrease in propagation velocity of transitions between bends in the mid-region of the flagellum. Computer simulations demonstrate that the synchronous sliding in the distal half of these flagella can be an entirely passive consequence of the mechanical interaction between active sliding and bending in the basal third of the flagellum and viscous resistances to movement of the distal region of the flagellum through the fluid environment. The current computer models do not contain a mechanism for asymmetric interbend decay that can reproduce these attenuated bending patterns. (C) 1994 Wiley-Liss, Inc.