Netzelia corona with some spines and a number of teeth

 

 

Netzelia corona (Wallich, 1864) Gooma et al., 2017

 

Diagnosis: shell spherical to sub-spherical. The shell wall is composed of mineral grains, quartz and diatom  frustules, which are agglutinated together by an organic cement. The shell is ornamented by conical hollow spines at the posterior third. The aperture is circular, surrounded by a variable number of inward-oriented angular crenulations (tooth-like structures). Shells ornated with tuberculate structures similar to Netzelia tuberculata have been observed by F. Siemensma (see http://www.arcella.nl/difflugia-corona,http://www.arcella.nl/difflugia-urceolata).

 

Dimensions: 140-320 µm (Leidy); 200-250 µm (Penard); 180-310 µm (Awerinzew); 180-230 µm (Cash); 155-200 µm(Hoogenraad & De Groot); 80-380 µm (Lahr & Lopes); my measurements 105-193 µm, mean 156 µm.

 

Ecology: in sediments, in sphagnum, on waterplants, often very common. This species has been found in icefield lakes high in the mountains (Monti 1906).

 

Remarks: Sometimes the shell has a tuberculate structure as in D. tuberculata. The number of conical spines I counted in Dutch specimen is commonly 4-6.

 

Difflugia corona
Difflugia corona
Shell, dorsal and apertural view
Difflugia corona
Difflugia corona
Small spine, 33 µm long and spine with a mineral grain in the opening
Difflugia bidens
Drawing: Penard, in Faune Rhizopodique du Bassin du Léman, 1902
Aperture with 12 denticulate lobes.
Each lobe is a hollow structure at the outer most part.
Shell with tubercular structure
Shell with tubercular structure - stacked image