Comments on the taxonomic treatment of Micractinium reisseri (Chlorellaceae,Trebouxiophyceae), a common endosymbiont in Paramecium

Micractinium reisseri Hoshina, Iwataki et Imamura (Chlorellaceae, Trebouxiophyceae), an alga symbiotic with the ciliate Paramecium bursaria (Ehrenberg) Focker, was recently renamed M. conductrix (K. Brandt) Pröschold et Darienko. The name ‘conductrix’ was originally given to an algal endosymbiont of Hydra, a genus of Hydrozoa. Here, I outline key differences between symbionts of hydra and Paramecium, and therefore, argue against the validity of the taxonomic treatment of M. reisseri by Pröschold and colleagues.