Genus: Colonies of 4 (or 2, 8, 16) cells attached side by side, arranged linearly or zigzag; cell body elliptical or spindle or crescent in shape; terminal cells with spiny projections in many species; cell wall usually smooth, but in some species granulated or dented or ridged (Illustrations of The Japanese Fresh-water Algae, 1977).
Species [ var. abundans ]: Colonies of 4 cells arranging lineary; cell body ovoid or ellipsoidal in shape, 9-20 μm long, 3-5 μm wide; outer cells with long spines at both ends (6-8 μm long) and short spines at outer side (3-5 μm long); inner cells sometimes have a short spine at both ends (Illustrations of The Japanese Fresh-water Algae, 1977).
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Outer cells have spiny projections and lateral spines
var. abundans
a dividing cell
cell 9 x 3 μm
Ueno
Tokyo, 2001
var. abundans
cell 8 x 4 μm
Soka
Saitama, 2002
var. abundans
cell 10 x 4 μm
Saitama, 1999
var. abundans
cell μm
Kamihira Park
Ageo
Saitama, 2003
var. abundans
cell μm
Hagoromo Park
Chiba, 2003
var. abundans
cell 9 x 4 μm
Shiroyama p.
Okegawa
Saitama, 2006
var. abundans
cell 9 x 4 μm
Kanayama g. p.
Kiyose
Tokyo, 2006
var. abundans
cell 10-11 x 3.5 μm
Heisei-no-mori
Kawajima
Saitama, 2006
var. abundans ?
cell 8 x 2.5 μm
Mizumoto park
Tokyo, 2001
var. abundans ?
cell 10 x 4 μm
Kayoicho-ike
Fukuoka, 2001Both spiny projections and lateral spines of outer cells elongated
var. longicauda
or var. abundans ?
cell μm
Chiba-Minato Park
Chiba, 2003
var. longicauda
cell 9-10 x 3 μm
Kayoicho-ike
Fukuoka, 2001
var. longicauda
cell 9 x 3 μm
Koriyama
Fukushima, 2001
var. longicauda
cell μm
route 272
Minakami
Gunma, 2007Outer cells have many short lateral spines
var. spicatus
cell 9-10 x 3 μm
Bessho-numa
Saitama, 2001
var. spicatus
cell 7 x 2.5 μm
Umi-no-nakamichi
Fukuoka, 2001Cell body ovoid, small; both spiny projections and lateral spines are short
var. brevicauda
cell 8 x 2.5 μm
Japan, 1998
var. brevicauda
cell μm
Kiyose
Tokyo, 2003
var. brevicauda
cell μm
spines μm
Kanayama Green Park
Tokyo, 2003
var. brevicauda
cell μm
spines μm
Kodaira Central Park
Tokyo, 2003
var. brevicauda
or S. microspina ?
cell μm
spines μm
Kayoicho-ike
Fukuoka, 2001