Trophic strategies among heterotrophic flagellates

Abstract Flagellates are common and abundant in most natural habitats and fulfil every trophic role from primary producer to carnivore. Many are voracious feeders on bacteria and play an important part in nutrient cycling and the degradation of organic matter. Osmotrophic (saprozoic) species are found in organically enriched environments with bacterivores, but are usually a minor component of the community in these habitats. Free-living flagellates can have a significant impact as grazers of algae, and, although few data exist, flagellate predation on other protists and metazoan gametes may affect the population dynamics of the prey species. Many flagellates with photosynthetic abilities are known to ingest prey ranging from bacteria to ciliates. The feeding habits of most species of heterotrophic flagellates are only superficially known. Given their ubiquitous nature, the quantitative and behavioural trophodynamics of heterotrophic flagellates is undoubtedly central to their ecological significance and to the flow of energy and materials through the microbial food web.