I only rarely find Zosterodasys transversa in a few of my sampling sites. A comparatively safe site to find specimens is the overflow channel of the Mühlhalden pond, because there are a lot of diatoms present, which are the main food of Zosterodasys transversa.

At first glance, Zosterodasys transversa resembles a cyrthophorid ciliate, such as Trithigmostoma cucullulus. However, Zosterodasys transversa is much larger and, above all, does not have the characteristic ventral ciliary fields that are typical of cyrthophorid ciliates. Instead, Zosterodasys transversa has a postoral synhymenium, which runs underneath the oral apparatus and almost encircles the body, but has a gap on the dorsal side. Zosterodasys transversa is therefore classified as a nassulid ciliate. In squashed specimens the synhymenium is clearly visible (s. fig. 2). The cilia of the synhymenium are also elongated and pointed (s. fig. 3).

Another characteristic feature of Zosterodasys transversa is the oral basket, which consists of 12-18 rods (nematodesmata = bundles of microtubules). In my population I also found specimens with 19 rods (s. fig. 2). At the distal end, the rods are bent in a knee-shape and thus resemble a field hockey stick. The bent ends of the rods in unsquashed specimens always point towards the center of the oral basket.