Massisteria marina Larsen & Patterson 1990, a widespread and abundant bacterivorous protist associated with marine detritus

Abstract

An account is given of Massisteria marina Larsen and Patterson 1990, a small phagotrophic protist associated with sediment particles and with suspended detrital material in littoral and oceanic marine waters. It has been found at sites around the world. The organism has an irregular star-shaped body from which radiate thin pseudopodia with extrusomes. There are 2 inactive flagella. The organism is normally sedentary but, under adverse conditions, the arms are resorbed, the flagella become active, and the organism becomes a motile non-feeding flagellate. The ecological niche occupied by this organism and its phylogenetic affinities are discussed.