sheath unlamellate or rarely lamellate, sometimes diffluent at the margins
So far I have only found Chroococcus subnudus in the Sima Moor (Austria), where this cyanobacterium is very common. The cells are smaller than 25 µm (without envelope) and thus less than half the size of those of Chroococcus giganteus. In addition, the sheath of Chroococcus subnudus is homogeneous and not layered. The color can vary greatly. My population appeared green in brightfield illumination (s. fig. 1) and rather olive green in DIC (s. fig. 2).
Fig. 1:Chroococcus subnudus. D = 14–21 µm (without sheat). A group of specimens in brightfield illumination. Obj. 100 X.
Fig. 2:Chroococcus subnudus. D = 14–21 µm (without sheat). The same specimens as shown in fig. 1 in DIC. Note the homogenous, not layered sheat of the cells (HS). Obj. 100 X.
Fig. 3:Chroococcus subnudus. D = 14–21 µm (without sheat). The same specimens as shown in fig. 2 with focal plane on the cell surfaces. Obj. 100 X.