Control of flagellar wave movement in Crithidia oncopelti

Abstract

MECHANISMS controlling cell behaviour are of considerable importance in biology and medicine, and much effort has been expended in experiments designed to evaluate the biochemical events which are involved in the mediation of a variety of cellular activities. Calcium ions are found to be involved in the regulation of a number of motile processes, such as muscular contraction¹, ciliary reversal² and cytoplasmic contraction³. We present here preliminary results which show that calcium may be responsible for the control of flagellar activity in a trypanasomid flagellate, Crithidia oncopelti. The flagellum of this organism propagates waves both distally and proximally in common with other trypanosomes⁴ but in contrast to the flagella on the majority of other protozoa and spermatozoa which are observed to maintain only distally propagating waves⁵. During normal swimming Crithidia propagates waves from tip to base, but on meeting an obstruction wave reversal occurs for several flagellar beats, thereby causing the organism to reverse its direction of movement and enabling it to escape from the obstacle. The wave reversal thus seems to be an avoidance reaction, and can be induced by mechanical, electrical or chemical stimulation⁶.