I have only found Kirchneriella phaseoliformis once before in June 2024 in the Lauchsee Moor in Austria.
The colonies stand out due to the very small cells. The bean-shaped cells are irregularly scattered in a gelatinous envelope. The edge of the colony is not sharply delimited, but rather deliquescent. The cells in my population had a length of 4.5–6.7 µm and were thus partly 40 % longer than indicated by Hortobágyi (1952). However, a population in China was also described as Kirchneriella sinensis, which had cells up to 5.5 µm long. The species Kirchneriella sinensis is considered synonymous with Kirchneriella phaseoliformis. The actual range of variation in the cells has therefore been little studied.
Kirchneriella phaseoliformis can be confused with the similar species Monoraphidium nanum (syn. Nephrodiella nana) and Gloeobotrys lunatus, whose cells have a similar size and shape. However, Monoraphidium nanum only occurs solitary and the colonies of Gloebotrys lunatus are sharply defined, with only a few cells (4–16). There is also the similar species Kirchneriella nana, which has so far only been found in highly eutrophic waters. Since I found my population in a nutrient-poor bog water, Kirchneriella nana can be ruled out as an alternative.
Fig. 1 a-b:Kirchneriella phaseoliformis. L = 300 µm (of colony). Two focal planes of a irregularly shaped colony with scattered, bean-shaped cells. The margin of the gelatinous sheath is deliquescent. Obj. 40 X.
Fig. 2:Kirchneriella phaseoliformis. L = 4.5–6.7 µm (of cells). The bean-shaped cells in the squashed colony. Obj. 100 X.
Fig. 3 a-h:Kirchneriella phaseoliformis. L = 4.8–6.7 µm. Different bean-shaped cells in detail. Nu = nucleus. Obj. 100 X.