Genus: Cell body crescent in shape (long, curved, tapered at both ends); cross section rounded; cell wall smooth or with longitudinal lines, bands on the cell wall in some species; chloroplast laminae ridged and radially arranged, which makes cross section star-shaped; pyrenoids aligned or scattered (Illustrations of The Japanese Fresh-water Algae, 1977).
Species: 390-(430-580)-800 μm long, 4-(5-7)-8 μm wide, L/W = 73-135; cell body very long, slightly curved, tapered at both termini; cell wall transparent, lack bands (Illustrations of The Japanese Fresh-water Algae, 1977).
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Similar species -->> C. gracile;
Cell body curved
C. aciculare
380 x 6 μm
L/W=63
Arakawa-Saiko p.
Minami-ku
Saitama, 2007
C. aciculare
375-520 μm
L/W=61-74
Akigase Park
Saitama, 2002
C. aciculare ?
252 x 4 μm
L/W=63
water reservoir
near Yamaguchi Univ.
Yamaguchi, 2004
C. aciculare ?
213 μm
L/W=61
Kayoicho-ike
Fukuoka, 2001
C. aciculare
195 x 3 μm
L/W=65
picnic-no-mori
Akigase Park
Saitama, 2005
C. aciculare
142 x 2 μm
L/W=71
Omine-numa
Tsukiyono
Gunma, 2003
C. aciculare ?
219 μm
L/W=58
Higashi-hiroshima
Hiroshima, 1998
Movies
C. aciculare ?
206 μm
L/W=54
Tochigi, 1998
C. aciculare ?
138 x 2.5 μm
L/W=55.2
Omine-numa
Tsukiyono
Gunma, 2003
C. aciculare ?
125 x 2.5 μm
L/W=50
Kannon-numa
Shimogo
Fukushima, 2005
C. aciculare ?
or C. gracile ?
150 x 3 μm
L/W=50
Daidarabotchi-ike
Iizuna-kogen
Nagano, 2003
C. aciculare
or C. gracile ?
275 μm
L/W=46
Japan, 199?
C. aciculare ?
or C. gracile
150-194 μm
L/W=38-48
Japan, 1998