Ovulinata - Microworld

O. parva – from Anderson et al. 1997

Genus Ovulinata Anderson, Rogerson & Hannah, 1997
= Ovulina Anderson, Rogerson & Hannah, 1996

Diagnosis: Test ovoid, small (15 µm), organic, lacking scales or mineral particles. Aperture terminal, round to oval, sometimes with a slightly thickened border. Surface somewhat granular (SEM). Nucleus large, vesicular.
Type species: Ovulinata parva Anderson, Rogerson & Hannah, 1996

Ecology: bacterivorous. Sandy marine sediments. The amoebae grow in a broad range of salinities (fresh to seawater). Known only from collection in Scotland. Possibly overlooked elsewhere because of its small size. Monospecific.

O. parva, from Tarnawski and Lara, 2015

Ovulinata parva Anderson, Rogerson & Hannah, 1996

Diagnosis: Test ovate, round in cross-section to slightly compressed, organic, hyaline and colorless at first becoming increasingly darker amber colored with age. Aperture terminal oval to round unadorned, or sometimes surrounded by a shallow collar. Pseudopodia hyaline, sometimes branched, long tapered to a point, arising directly from the aperture or from the periphery of a thin web of ectoplasm emergent from the aperture. Nucleus round. Nucleolus central to slightly eccentric, round (1 to 2 µm), densely-staining. Fine structural features: cell body ovoid surrounded by fine fibrillar organic envelope immediately lining the inner surface of the test. Test with scattered small elongate pits (~1 µm in major dimension) forming depressions in the surface, without perforations. Pustule like projections with hyaline interiors, appearing as refractive bodies in bright field light microscopy, may be confused with scales or mineral deposits which are lacking.

Dimensions: Length 15 µm, width 11 µm, nucleus 5 µm (n=20).

Habitat and distribution: Bacterivorous. Sandy marine sediments. The amoebae grow in a broad range of salinities (fresh to seawater). Known only from collection in Scotland. Possibly overlooked elsewhere because of its small size.

O. parva, scale bar 10 µm – from Howe et al. 2011

Ovulinata spec.

Diagnosis: Very small testate amoebae (length: 9.7 µm; width: 7.3 µm), with an ovoid non-compressed transparent test, comparable to the related species Ovulinata parva. Pseudostome slit-shaped, oblique, length 3,2 µm. Test brownish. Filopodia fine, branching.

Ecology: Sediment of mesotrophic water in Crailoo, the Netherlands, 2017 and 2019 (see images and video below). At least, I think it is an Ovulinata species.