Paravannella minima
Paravannella minima - from Kudryavtsev, 2014

 

Genus Paravannella Kudryavtsev, 2014

 

Diagnosis: Amoebae of fan-shaped morphotype usually below 10 µm in size and with a smooth outline. Floating form radial, with short, blunt hyaline pseudopodia. Glycocalyx may contain pentagonal glycostyles and simple filaments.

Type species (by monotypy): P. minima Kudryavtsev, 2014

 

Paravannella minima Kudryavtsev, 2014

 

Diagnosis: Measured length of the locomotive form 4.7–9 µm (average 5.8 µm), breadth 4.5–10 µm (average 6.7 µm), length:breadth ratio 0.62–1.2 (average 0.88); n = 100. Locomotive form rounded, oval or semicircular with smooth outline without folds or wrinkles. Single vesicular nucleus 1.7–3.3 µm (average 2.4 µm) in diameter, with central nucleolus, 1–2 µm in diameter (average 1.4); n=61. Radial floating form with short blunt hyaline pseudopodia not exceeding the diameter of the central cytoplasmic mass; rarely adopted.

Glycocalyx contains pentagonal tower-shaped glycostyles 100–125 nm long (average 113 nm) and simple filaments 190–291 nm long (average 249 nm) embedded in a basal amorphous layer 12–20 nm thick.

 

Ecology: Freshwater (aquarium filter mud), aerobic.

 

Remarks: Differs clearly from all sequenced vannellid genera in having two helices E23-2 and E23-3 in the region V4 of the SSU rRNA gene; similar to Ripella spp., Vannella aberdonica, V. langae, V. murchelanoi and V. peregrinia in the size of the locomotive form, but differs clearly from Ripella in having a smoother outline of the locomotive form, less frequent formation of a drop-shaped locomotive form with tapering posterior end, and a floating form with shorter pseudopodia; differs from the similar species of Vannella in having a floating form with radiating pseudopodia and a freshwater origin.

 

Reference: Kudryavtsev, A., 2014. Paravannella minima n. g. n. sp. (Discosea, Vannellidae) and distinction of the genera in the vannellid amoebae. Eur. J. Protistology 50, 258–269