Testudinella parva var. bidentata (Ternetz, 1892)

Most likely ID: n.a.


Synonym: Testudinella bidentata, Pterodina bidentata, Testudinella parva


Sampling location: Hagstaffel pond, Ulmisried, Simmelried


Phylogenetic tree: Testudinella parva var. bidentata



  • lorica almost circular, dorso-ventral flattened
  • body transparent, length 115–120 µm, width 105–110 µm
  • two lateral projections of the lorica in the posterior third
  • polygonally shaped foot opening ventral at posterior end
  • foot annulated, retractile, distal end with cilia
  • corona is a band of cilia
  • two conspicuous retractor muscles
  • two eyespots
Testudinella parva var. bidentata

I have found Testudinella parva var. bidentata both in the plankton from Hagstaffel pond and among floating plants in Ulmisried and Simmelried. The species is much rarer than the related species Testudinella patina. Testudinella parva var. bidentata is easily recognized by the two short spines, which are located laterally in the posterior third of the lorica.


The taxonomy of Testudinella parva var. bidentata is somewhat unclear in my opinion. The valid name should be Testudinella parva. However, the form Testudinella parva has been described without the lateral spines. Therefore, it is currently unclear to me how to distinguish between Testudinella parva var. bidentata and Testudinella parva with the same name. Therefore I have kept the name Testudinella parva var. bidentata originally given by Ternetz.


Fig. 1: Testudinella parva var. bidentata. L = 172 µm (including corona and foot). A freely swimming specimen. Note the two lateral spines in the posterior third of the lorica (arrows). Obj. 20 X.


Fig. 2: Testudinella parva var. bidentata. L = 160 (including corona and foot). A slightly squashed second specimen. Obj. 40 X.


Fig. 3 a-b: Testudinella parva var. bidentata. A fully extended (a) and a retracted specimen (b). The lorica of the retracted specimen has a length of 112 µm. Obj. 100 X.


Fig. 4: Testudinella parva var. bidentata. L = 138 (including corona and foot). A half extended specimen. Obj. 100 X.