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Belonocystis tubistella
B. spinifera, Radiopoel, Netherlands

Belonocystis spinifera  (Brown, 1918) n. comb.
Syn.: Belonocystis tubistella Rainer, 1968

Diagnosis: Cells spherical, with fine filopodia without any extrusomes, filopodia can wave like a slow flagellum; nucleus eccentrically located, with a prominent nucleolus; one to four functional contractile vacuoles are present; periplast composed of radiating spines with a broad tent-shaped base and a long hollow shaft that was widest near the base and tapered to a very fine distal point; base of the shaft divided into four curved arms that form a basal tent-like structure covered by a membranous sheet, perforated with circular to elliptical pores in close proximity forming a mesh-work appearance to the spine base.

Dimensions: Nicholls: cells 8-16 µm diameter; nucleus about 4 µm diameter; spines 10-15 µm long, shaft 0.1-0.3 µm diameter wide near the base; scale base 2-3 µm wide,  pores in the sheet mesh-work structure forming the bases 0.1-0.3 µm diameter.

Ecology: fresh water; North America, Europe. In my samples from different watertypes it is usually a common organism.

Remarks: The fine filopodia are difficult to see, even with high magnification phase-contrast microscopy. In the living, uncollapsed state, the top portion of the spine base appears funnel-shaped with sloping sides that abruptly straighten to nearly parallel sides where scale bases abut one another.
Amazingly, Penard never described this species, as it is easy to spot and by no means very rare.

Literature: Rainer, 1968, , Mayer, 1997, Nicholls, 2012.

Belonocystis tubistella
Belonocystis tubistella
Belonocystis spinifera, 11 um; base of the spines
Belonocystis spinifera
Belonocystis tubistella
N nucleus; n nucleolus; fv food vaculoa ss spine f filopodium cv contractile vacuole Base of a spine scale (from Nicholls, 2012)

Belonocystis spinifera, spine-scales, specimen from the Netherlands – Photomicrograph Eckhard Voelcker
Belonocystis spinifera
Belonocystis spinifera
Empty periplast
Belonocystis tubistella
Belonocystis tubistella
Belonocystis spinifera, empty periplast
Belonocystis spinifera
Belonocystis tubistella
Single spine, Phase contrast 100X; dried
Belonocystis tubistella
Belonocystis tubistella
Belonocystis spinifera
Belonocystis spinifera
Belonocystis spnifera
Belonocystis spinifera,Netherlands, 2020
Belonocystis tubistella
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