Die Bedeutung der Untersuchungen des Lebenszyklus bei der Bestimmung fadenförmiger Grünalgen (Chlorophyta)

Abstract

Summary Investigating the epibiontic algae growing on planctonic Entomostraca in a rural pond masses of green coloured Daphnia magna individuals were observed. The outer surface of the chitin shells of these Daphnias was densely overgrown with a small filamentous green alga resembling Protoderma daphnicola Fott . Protoderma however is a representative of pseudoparenchymatous algae with biflagellate zoospores. No one of these characters could be found in the studied alga. The alga produced under natural conditions short prostrate uni- or biseriate filaments, only sometimes with 2–3 erected cells as known in the genus Pseudendoclonium. Moreover quadriflagellate zoospores were arising. In cultures the mentioned alga produced as well prostrate as erected filaments and the plant has developed into a Stigeoclonium with all its typical features. Zoospores of two types were formed, large quadriflagellate macrozoospores and smaller quadri- or biflagellate microzoospores. The cultured Stigeoclonium belongs with regard to the prostrate system probably into the group of Stigeoclonium tenue ( Ag .) Kutzing . On this example authors call attention to the possibility of making mistakes in determination of filamentous green algae if they are not well developed. Therefore the knowledge of their whole life cycle is most important, both in nature and in culture.