cell obovoid or pear-shaped with a long caudal prolongation
usually slightly twisted
length 85–170 µm
pellicle longitudinally striated
chloroplasts disc-shaped
flagellum half of body length
eyespot prominent
usually one large paramylon body, centrally located
nucleus eccentrically located
Phacus longicauda
Phacus longicauda is one of the most common representatives of the genus Phacus in my sites. I find it in the upper layer of mud but also in the floating plant masses. Because of the long spine the species can hardly be confused. Sometimes slightly twisted specimens occur (s. fig. 3 a-b), but they are never as twisted as Phacus tortus, whose cell is twisted by 360°.
Fig. 1 a-b:Phacus longicauda. L = 147 µm. Two focal planes of a slightly squashed specimen. ES = eyespot, F = flagellum. Obj. 100 X.
Fig. 2 a-b:Phacus longicauda. L = 151 µm. Two focal planes of a second, slightly squashed specimen. Chl = disc-shaped chloroplasts, CPB = central paramylon body, Nu = nucleus. Obj. 100 X.
Fig. 3 a-b:Phacus longicauda. L = 135 µm. Two focal planes of a slightly twisted specimen. Obj. 100 X.