I find Ophryoglena flava regularly, but always only sporadically and in single specimens. They are usually found in floating and decomposing plant masses. I found most of the specimens in the Simmelried.

The body shape of Ophryoglena flava is very variable. Often the specimens are completely opaque due to masses of food vacuoles and are almost round in shape. Only rarely are starving specimens found, which then have a slender shape with a slightly pointed posterior end (s. fig. 1 a-d). Such specimens are then yellow-brownish in color. The specimens swim very fast and move hectically forwards and backwards. The body is also extremely metabolic.

Like all other species of the genus, Ophryonglena flava has an oral apparatus in the shape of a „6“. The oral apparatus has a complex structure and contains the so-called watch-glass body, which is also known as Lieberkuehn’s organelle (s. figs. 3 and 4). The watch-glass body of Ophryoglena flava is clearly recognizable. It is slightly yellowish in color and its surface is finely striated (s. fig. 5 a-b). Its function is unclear. However, it is assumed that it is connected with the widening of the mouth opening when swallowing large prey.

Ophryoglena flava can be easily distinguished from other species of the genus by the two contractile vacuoles located on the right side of the body (s. fig. 2 a). They have many auxiliary vacuoles, which taper into thin collecting canals that extend very far into the cytoplasm (s. fig. 6). Each contractile vacuole has 3-4 excretory pores, which can be clearly seen when focusing on the pellicle (s. fig. 7).

More images and information on Ophryoglena flava: Michael Plewka-Freshwater life-Ophryoglena flava