Ecology of Heterotrophic Microflagellates. I. Some Important Forms and Their Functional Morphology

Abstract

Nanoplanktonic, heterotrophic flagellates [Ochromonas wyssotzki, Paraphysomonas vestita, Pseudobodo tremulans, Monosiga sp., Actinomonas mirabilis and Pleuromonas jaculans] are described with special reference to feeding mechanisms and functional morphology. Two different types of food particle concentration mechanisms are found: filtration and direct impact. Both mechanisms depend on the creation of water currents. Crude models show that at least in some cases, the described mechanisms can explain experimentally determined values of clearance and that the organisms may subsist on the basis of bacterial concentrations found in seawater. Theoretical considerations and previous experimental results render it very unlikely that uptake of dissolved organic material plays any role for these organisms in nature. Organisms of the studied size range (3-7 .mu.m) constitute a necessary link between bacteria and larger phagotrophic organisms in planktonic food chains.