Diatom locomotion: Computer assisted analysis of cine film

Abstract

Cine films of eight species of diatoms were analysed with the aid of computers and the technique is described in detail. Programs were written for graphical presentation of the data obtained from the film to illustrate velocity and acceleration characteristics of movement. Movement is characterized by rapidly fluctuating velocity; large changes in speed occurred within tenths of a second, associated with acceleration of over 100 μm s-2 in some species. This is to be expected for objects of this size which have very little inertia. It is suggested that the driving force for locomotion is not steady but intermittent, and that this is the cause of velocity fluctuations in the movement of the diatom itself and in the movement of particles streaming along the dorsal raphe. Analyses of particle streaming along the raphe slit leads to the tentative proposal that ventral and dorsal raphe activity may be co-ordinated in some way and that the driving force may vary along the length of a single raphe slit.