Morphology of the prostrate thallus of Stigeoclonium (Chlorophyceae, Chaetophorales) and its taxonomic implications

Abstract

The prostrate thallus of Stigeoclonium was studied under defined culture conditions. The development from zoospore to adult stage was followed in detail with the result that no more than three morphological groups (or species) can be discerned. The three groups are designated as Stigeoclonium helveticum, S. tenue, and S. farctum. Considerable intra- and intergenotypic variation exists, especially in the erect system of Stigeoclonium helveticum and in the prostrate system of S. tenue. The prostrate system of Stigeoclonium farctum is not always a closed pseudoparenchymatous disc, but may form an open star-like ‘variabile’ habit.