Studies on the ultrastructure and taxonomy of the genusTetraselmis (Prasinophyceae): III. SubgenusParviselmis

Parviselmis is described as the third subgenus ofTetraselmis (Prasinophyceae) on the basis of the ultrastructural features of pyrenoid. This subgenus is characterized by the pyrenoid whose matrix is invaded by cytoplasmic canaliculi that terminate most blindly within the matrix and by the smaller size of cells, most falling within the range between 6–14.5 μm in length. The species known at present to have these characters areTetraselmis striata, T. levis, T. chui, T. alacris andT. suecia. The description of these five species are given in detail in this paper mainly based on the ultrastructural features.