Preliminary Observations on the Holdfast of Amoebidium Parasiticum

SUMMARY

The thallus of Amoebidium parasiticum is attached to its host animal by a basal, acellular holdfast. The holdfast is produced soon after sporangiospore release and may adhere, with varying effectiveness, to a variety of natural and unnatural substrates. Electron micrographs have disclosed a number of electron transparent pits which seem to perforate the cell wall at each end of the thallus. The holdfast material is always associated with one of these “pit fields” and it is assumed that the initial production and continued development of the holdfast occurs by extrusion of the adhesive through the terminal pit field. The cytoplasm adjacent to the holdfast contains a high density of membrane bound vesicles of approximately 0.24 μ in diam. The matrix of the vesicle resembles the amorphous holdfast material.