First Record of Algal Ball-forming Aegagropilopsis clavuligera (Cladophorales, Ulvophyceae) from Japan

Abstract

Algal balls belonging to the genus Cladophora sensu lato, also known as ‘Marimo’ in Japanese, were found in a home aquarium containing rosy bitterling (Rhodeus ocellatus ocellatus). The algal balls were presumed to have originated from bivalves collected from Lake Motosu, which the bitterling use for spawning. Genetic analyses showed agreement with the 18S rRNA gene of Aegagropilopsis clavuligera, registered in GenBank from tropical aquarium in the Netherlands and China. Zoospore formation noted during microscopic observations was consistent with the description of Aegagropilopsis clavuligera and their morphological differences were vague. This is the third species in the ball-forming Aegagropila–Aegagropilopsis group identified in Japan, and has been given the Japanese name ‘Motosu Marimo’.