So far I have only found Rotaria macroceros in the Simmelried. The individuals are very difficult to find in fresh samples, as they leave their tube when disturbed. However, if the sample containers are left for 2–3 weeks without direct sunlight, nests consisting of several tubes can often be found on the container walls (s. fig. 1 a-b). Macroscopically, these nests have a flake-like appearance. They must be removed very carefully with a pipette and placed under the coverslip with a hight layer thickness. The water is then allowed to evaporate on its own to achieve an optimum layer thickness. However, if this becomes too small, the specimens will leave their tube or contract.

Within the genus Rotaria, Rotaria macroceros is one of the few species that live in self-constructed tubes. These consist of detritus and are often yellow-brown in color (s. fig. 2). This is an important identification feature of Rotaria macroceros. Another important feature is the very long dorsal antenna (s. fig. 3). It consists of two segments and can therefore elongate enormously. However, it is often seen half retracted. Therefore the specimens have to observe specimens a little longer to see both segments.

Some of the specimens in my population were up to 400 µm long and thus about 25 % longer than Donner (1965) stated (250–300 µm). However, all other characteristics corresponded with his description.

More images and information on Rotaria macroceros: Michael Plewka-Freshwater life-Rotaria macroceros