RETICULOMYXA FILOSA
Reticulomyxa filosa, young plasmodium – after Nauss, 1949

Genus Reticulomyxa Nauss, 1949, emend. Hülsmann, 2006

Diagnosis: Multinucleate plasmodium of everchanging shape. Tectum as (protective) covering but reduced considerably. Central protoplasmic area surrounded by an intricate network of very long, active, anastomosing granofilose pseudopodia, which arise from any point on the surface. Pseudopodia with bidirectional streaming. Many non-contractile vacuoles while vegetating, cytoplasm thickly granular, no differentiation into ecto- and endoplasm.  Cleansing process before onset of migration phase; huge covering of waste (detrital) material produced by excretion of egesta and filamentous material along whole surface of strands. Prolonged culturing possible on wheat germ flakes.

Ecology: Freshwater habitats

Remarks: Reticulomyxa filosa is a freshwater amoeboid with fine granular, branching and anastomosing pseudopodia and therefore traditionally placed in the class Granuloreticulosea, as a sister group to the order Foraminiferida. Recent studies have revealed remarkable similarities in pseudopodial motility and ultrastructure between R. filosa and foraminifera (e.g. Allogromia laticollaris) and clearly show that R. filosa branches within the clade of foraminifera, suggesting that R. filosa is in fact a naked freshwater foraminiferan. (Pawlowski et al, 1999)

Description: The multi-nuclear protist Reticulomyxa filosa can be several millimetres in size and is divided into a stationary central area exhibiting wide protoplasmic streams and a peripheral area characterized by thin reticulopodia. The reticulopodia phagocytose nutritional particles where they are digested. Food limitation causes migration, often associated with plasmotomia. Several individuals can fuse. Under stress situations resistant forms are made.

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