[3] rDNA evidence suggests that Thalassiosira weissflogii is a species complex and that several different genetic populations exist.
There was found to be a divergence between one clade from the east and west Atlantic Ocean and California and another from Hawaii and Indonesia.
The face of the valves vary in shape but are basically irregular rings with one labiate and two or more central processes.
Other features that may be present include an irregularly shaped areola or pore, further processes on the rim of the valves, marginal spines, striations and thick radial ribs.
[2] The native range of Thalassiosira weissflogii is unclear, but it is found in marine, brackish and freshwater environments.
This event may be triggered by some external factor such as a variation in light intensity, temperature or day length.
It is considered preferable for this purpose to the other commercially available microalgae, Chaetoceros and Tetraselmis, because of its larger size which means it can continue to be used at more advanced larval stages.