Trypanococcus rotiferorum Stein in Zacharias, 1885

= Physaliella collini Penard, 1920

Report as endobiont on rotifers: The suctorian ciliate named Trypanococcus rotiferorum, parasitic in rotifers, was found but not described by Stein, without host mentioning. Later the species was observed and redescribed by Zacharias (1885) in the rotifer Rotaria rotatoria (Pallas, 1766) collected in a pond near Kummersdorf, Germany. The species also was found by Zacharias (1885) in Embata parasitica and Stephanoceros fimbriatus from the same locality.

Later the species was independently found and described from Lake Geneva, Switzerland (Penard 1920a, b), under the name Physaliella collini in the rotifer Rotaria socialis, which in turn is an epibiont of the isopod Asellus aquaticus (Linnaeus, 1758) .