 
 
 50 μm
 50 μm
 100 μm
 100 μm
 150 μm; x 400 :
 150 μm; x 400 : 
 31 μm
 31 μm
 63 μm
 63 μm
 94 μm; x 640
 94 μm; x 640
 
 
 
 
Frontonia marina, stock Sao-2, 
cell body 150 μm long, 52 μm wide, 
x 400, Omiya, Saitama city, Saitama Pref.,  2001 by Y. Tsukii
 50 μm
 50 μm
 100 μm
 100 μm
 150 μm; x 400
 150 μm; x 400
 
 
Frontonia marina, stock Sao-2, 
cell body 150 μm long, 48 μm wide, 
a macronucleus ovoid, 
x 640, Omiya, Saitama city, Saitama Pref.,  2001 by Y. Tsukii
 31 μm
 31 μm
 63 μm
 63 μm
 94 μm; x 640
 94 μm; x 640
 
 
 
 
 
 
 
Frontonia marina, stock Sao-2, 
cell body 190 μm long, 65 μm wide, 
x 400, x 640, Omiya, Saitama city, Saitama Pref.,  2001 by Y. Tsukii
 50 μm
 50 μm
 100 μm
 100 μm
 150 μm; x 400 :
 150 μm; x 400 : 
 31 μm
 31 μm
 63 μm
 63 μm
 94 μm; x 640
 94 μm; x 640
 
 
* F. marina Fabre-Dom., 1891 (F. leucas var. marina Florentin, 1899): Cell body 150-600 μm long; posterior end slightly pointed; two ovoidal micronuclei; a single contractile vacuole (Kahl, 1930).
F. acuminata Ehrenberg, 1833 (F. acuminata var. angustata Kahl, 1931; F. arenaria Kahl, 1933): Ovoid, 60-100 μm long; cytostome ovoid; a single macronucleus and single micronucleus anterior; a single contractile vacuole central; numerous large trichocysts (Carey, 1992).
F. depressa (Stokes, 1886) (F. parvula Penard, 1922): Cell body 60-80 μm long; macronucleus short sausage-shaped; a single micronucleus; a single contractile vacuole (Kahl, 1930).
F. macrostoma Dragesco, 1960: Ovoid, small 125-230 μm long; very large oral aperture, well defined suture; a large macronucleus with single micronucleus; a contractile vacuole posterior; many large trichocysts; pellicle with interkinetal striation (Carey, 1992)
Frontonia elliptica Beardsley, 1902: Cell body 150-200 μm long; macronucleus ovoid, with a single micronucleus large, ovoid in shape; two contractile vacuoles present (Kahl, 1930).
Frontonia fusca (Quennerstedt 1869): Cell body 150-200 μm long; macronucleus ovoid, with a small micronucleu; a single contractile vacuole located at posterior half of the cell body (Kahl, 1930).