I mainly find Itura viridis among floating and decomposing plants. When examining the samples, the specimens are easy to recognize by their size and bright green color. Only free-swimming specimens extend their lateral auricles at the head (s. figs 1 a and 2 a).

Itura viridis is one of the few rotifers that possess symbiotic zoochlorellae. These are located in the blind sacs of the stomach. The blind sacs are bladder- and finger-shaped protrusions of the stomach, which extend high up to the mastax and into the posterior abdomen (s. fig. 11). The zoochlorellae are chloroplasts that essentially originate from phagocytized euglenids such as Euglena or Phacus. One should therefore rather speak of kleptoplasts here, since they were “stolen” from the prey. In the gastric blind sacs, the kleptoplasts continue to carry out their synthetic activity and additionally supply Itura viridis with nutrients.

Itura viridis has no gastric glands. Instead, there are two subcerebral glands at the level of the mastax (s. fig. 11). At the front end of the head there are two eyespots with lenses (s. fig. 7). A third eyespot is located on the retrocerebral sac (s. fig. 5). This is usually filled with highly refractive crystals (s. fig. 10). In the center of the stomach, so-called defecation concretions are visible (s. fig. 11). These are orange, red or brown residues of the digestion process that have an oily character.

The specimens of Itura viridis in my population were always 190–240 µm long. I have never found larger specimens. This size is clearly below the range of 260–400 µm given by Koste (1978). All other characteristics agree with the description of Itura viridis.

More images and information on Itura viridis: Michael Plewka-Freshwater life-Itura viridis