So far I have found Mallomonas matvienkoae for the first time in a drainage ditch in the industrial area of Radolfzell. I have not been able to find the species in my other localities.

The species was originally described by Matvienko (1941) as Mallomonopsis elliptica on the basis of the two flagella and oval scales. Belcher (1969) proposed to treat species with two flagella as subspecies of the genus Mallomonas and Asmund & Kristiansen finally renamed the species in Mallomonas matvienkoae on the basis of electron microscopic studies.

My specimens were all less than 30 µm long. The free-swimming specimens were somewhat more elongated than the specimen shown in fig. 1 a-d, which is already slightly squashed. The two flagella (s. fig. 1 a) are difficult to recognize even at high magnification. The scales and the L-shaped spines attached to them correspond to Matvienko’s descriptions (s. fig. 3). The egg-shaped scales have a thickened edge at the tapered end. This is also where the spines are attached, which are very easily detached by the pressure of the coverslip (s. fig. 3). In contrast to Matvienko’s description, I could recognize only one contractile vacuole at the posterior end (s. fig. 1 c) and the nucleus was located in the anterior third (s. fig. 1 b). The center of the cell was filled by a large leucosin body.