Only a very brief description and a drawing of Cyclidium centrale are available from Kahl (1931). I have not found any further reports on this species. In November 2017, I found a Cyclidium species in the Ulmisried that essentially exhibits all the characteristics of Cyclidium centrale. These are particularly the contractile vacuole in the middle of the body, a peristome that takes up about one-third of the body length, and a length of about 40 µm (s. fig. 1 a-b). All these features are fulfilled by the specimen, of which I unfortunately only took a few photos.

In May 2024, I then found another specimen in the Simmelried, which, however, was significantly smaller at 27 µm in length. Furthermore, in this specimen, the peristome extended almost to the middle of the body. The contractile vacuole was located slightly below the cell equator. Therefore, I present this specimen here as Cyclidium cf. centrale (s. fig. 2 a-d).

Within the genus Cyclidium and the similar genus Cristigera, there are very few species with a contractile vacuole in the middle of the body, so the selection of alternative species is very small. Cyclidium muscicola is significantly smaller at 20 µm and has a stocky body. Cyclidium fusiformis is about 30 µm long and the posterior third of the body is distinctly tapered.