Sagenoerithids are a group of marine unicellular diflagellate organisms. Sagenoerithids are phagotrophic. They produce a unique network of strong sticky microfilaments, which serve as both motility tracks attached to their sides, which the cells glide along and use as nets to catch nutrients.
The filaments, although outside the cell, are surrounded by a membrane. They are formed and connected with the cytoplasm by the sagenogen organelle. The cells are uninucleate and typically ovoid, and move back and forth along the amorphous network at speeds varying from 5-150 μm per minute. Reproduction is via zoospores
There are approximately 50,000 species of sagenoerithids.