Aphanocapsa planctonica
(Smith) Komárek & Anagnostidis, 1995
Most likely ID: n.a.
Synonym: Aphanocapsa elachista var. planctonica
Sampling location: Simmelried
Phylogenetic tree: Aphanocapsa planctonica
Diagnosis:
- colony in a common mucilaginous sheath, irregularly or spherically shaped
- cells scattered, widely spaced
- no individual mucilaginous envelope of cells
- cells spherical, diameter 2–3 µm
- color pale blue-green
- cytoplasm homogenous, only few, small granules
- gas vacuoles absent
- planktonic lifestyle
Although Aphanocapsa planctonica is said to have a planktonic lifestyle, I found this cyanobacterium between floating plants in the Simmelried.
The identification is based on the shape of the cells and the cell size. The cells of the genus Aphanocapsa are spherical, while the cells of the genus Aphanothece are cylindrical or elliptical in shape. The species within the genus Aphanocapsa are differentiated according to the size of the cells. Aphanocapsa planctonica has cells with a diameter of 2–3 µm. The cells of the similar species Aphanocapsa elachista have a diameter of 1.5–2 µm and the cells of the species Aphanocapsa delicatissima are even smaller with a diameter of 0.5–0.75 µm. The cells in the colonies from the Simmelried have a diameter of 2.4–3.1 µm (s. fig. 3). It must therefore be Aphanocapsa planctonica.
Fig. 1: Aphanocapsa planctonica. L = 4120 µm (of colony). A large, irregularly shaped colony. Obj. 4 X.
Fig. 2: Aphanocapsa planctonica. L = 4120 µm (of colony). A closer view of the colony as shown in fig. 1. Obj. 10 X.
Fig. 3: Aphanocapsa planctonica. D = 2.4–3.1 µm (of cells). The spherical, pale blue-green cells in brightfield illumination. Obj. 100 X.
Fig. 4: Aphanocapsa planctonica. D = 2.4–3.1 µm (of cells). The spherical cells in DIC. Obj. 100 X.