The well known hypotriche ciliate Stylonychia pustulata was transferred into the new genus Tetmemena by Eigner (1999) on the basis of genetic analyses. Tetmemena pustulata is very common and adaptable to environmental conditions. It is found in practically all of my sampling sites. It likes to settle on the floating cover glass and is then easy to observe.

The exact identification of hypotriche ciliates using light microscopy alone is difficult, even with very common species. It is therefore necessary to closely examine the nuclear apparatus, the position of the contractile vacuole and especially the ventral ciliature. In the case of Tetmemena pustulata, two macronuclei are present, each with an attached micronucleus (s. fig. 6 b). The contractile vacuole is located on the left side, approximately in the middle of the body (s. fig. 6 b). The 4 fronto-ventral cirri are particularly important in the ventral ciliature. In Tetmemena pustulata they form a V-shaped arrangement (s. fig. 5). In the very similar species Tetmemena vorax, the right cirrus of the fronto-ventral cirri is clearly separated from the straight row of the three left cirri. On the dorsal side of Tetmemena pustulata the ciliation is strongly reduced to 6 rows of short, bristle-shaped cilia (s. fig. 6 a).