Fragilariforma nitzschioides

Fragilariforma nitzschioides forms colonies where individual cells are held together by small linking spines and small mucilage pads produced at the apical pore fields of each valve (Round et al, 1990). In live colonies, chloroplasts are numerous, small, discoid, and are either scattered throughout the cell or gathered into the center of the cell. It is abundant in samples collected from the Cayler Prairie pothole in Dickinson Co., Iowa. Live samples were collected from the outflow stream in the marshy area located within the pothole. The prairie pothole experiences both wet and dry periods throughout the year, and numerous F. nitzschioides internal valves are observed in samples of detrital thatch from the marsh and outflow stream. Internal valves are valves that are not part of the regular division of the cell and only one functional valve is produced during mitosis (Round et al, 1990). Internal valves are common in taxa living in subaerial or saline habitats, and are also associated with dormancy in some taxa (Round et al., 1990).

Fossil F. nitzschioides colonies (chains of 10-15 individuals) have been reported in the 602,000 year old Lava Creek B Ash deposit (Yellowstone Caldera eruption) in Smithville, Texas. The autecological preferences of the diatom assemblage (both planktonic and benthic taxa) in the ashfall deposit suggests these taxa were living in a cool, alkaline, moderate to high conductivity, slow-flowing stream or lake (Winsborough, 2000).