The haptonema as a food-capturing device: observations on Chrysochromulina hirta (Prymnesiophyceae)

Abstract

It is shown that the haptonema plays an important role as a food capture and transport device in the processes of phagocytosis in the marine flagellate, Chrysochromulina hirta Manton (Prymnesiophyceae). The capture offood and its transport by the haptonema were observed only when the cells were swimming with the haptonema fully extended forward and the two flagella beating backwards alongside the body of the cell. Food particles become attached and adhere to the haptonema. They then move down to a particular point on the haptonema, the particle-aggregating centre, where they accumulate. The cell stops swimming, and the aggregated food moves toward the tip of the haptonema. After the food aggregate reaches the tip, the haptonema bends and delivers it to the lateral posterior surface of the cell. The food aggregate is then translocated to the posterior end of the cell, where it is taken into the cell by phagocytosis. The haptonema bends even when it does not carry any particles, suggesting that it repeats the same motion at certain programmed intervals. Various mechanisms possibly involved in food capture and transport are discussed.