Family: Trichome (filamentous structure) with heterocysts; with equal diameter throughout hole length; no branching; heterocysts intervening or at base.
Genus: Mucous sheath, nearly invisible; heterocysts intervening; filments solitary or agglutinate within a gelatinous matrix (Illustrations of The Japanese Fresh-water Algae, 1977).
Google Image Search
Filaments solitary or form a thin gelatinous sheath 
A. spiroides ?
x 10 μm
Tsukuba
Ibaraki, 2002
A. spiroides ?
x 10 μm
Zenko-ji
Nagano, 2003
A. spiroides ?
x 8 μm
near Town Hall
Shobu
Saitama, 2004
A. spiroides ?
x 5-6 μm
Yamagata, 1999
A. spiroides ?
x 6 μm
Mizumoto Park
Tokyo, 2001
A. spiroides ?
x 4.5 μm
Mizumoto Park
Tokyo, 1999
A. spiroides ?
x 4.5-5 μm
Yamagata, 1999
