Acanthocystis clavata
From Siemensma, 1991

Acanthocystis tubata Dürrschmidt, 1987

Diagnosis: Periplast, ca. 25 µm in diameter, with two types of siliceous scales. Details of protoplast unknown. Plate scales ovoid or elliptical, 2.9-3.7 µm long and 2.2 µm wide, patternless, except for an axial thickening. Spine scales, 6-11 µm long and 0.23 µm wide at the narrowest point. Shaft cylindrical, gradually expanding towards the distal end. Apex, 0.4 µm in dia­meter, covered by a thin siliceous layer. A circle of about 12 conical teeth surrounds the apical margin. Base of the shaft supported by a circular, centrally depressed base­plate (diameter 1.2 µm) with peripheral rim.

Ecology: Surface sample collected 1982 in a swamp near Maramaranui, North Island, New Zealand.

Remarks: Dürrschmidt: A. tubata specimens reveal in the light microscope a striking similarity to A. mimetica Penard (1904), in the gradually expanded spine scale shafts, their circular base-plates and the dimensions of cells and scales. The only feature which contradicts an identification with A. mimetica is the absence of a conspicuous horse­shoe-like rim reported by Penard from the surface of the plate scales. Such a ‘rim’ appears sometimes during the LM observation of uneven structured plate scales, especially when these are somewhat tilted. Those scales are present, for instance in A. rotundata Nicholls ssp. rotoairense and A. pantopodeoides Nicholls (syn. A. cuneiformis Dürrschmidt. Thus it is assumed to be only an optical effect. However, the plate scales of A. tubata are flat. As no type material has been left by Penard, as inquiries at the following institutes revealed (British Museum, London; Museum D’Histoire Naturelle, Geneva; The Royal Microscopical Society, London; Museum National d’Histoire Naturelle, Paris) it will remain unclear on which specimens Penard based the diagnosis of A. mimetica.

A. tubata is easily recognized under the electron microscope by the shape of the spine scales. No variation in scale structure has been observed in specimens from different localities.

Recent posts

Microcorycia spec. 4

Microcorycia spec. , folded Microcorycia spec.? I found this specimen in a sample from moss on a fallen tree in a marsh in the Naardermeer,

Read More »

Microchlamys spec.

Microchlamys spec., the same cell in lateral view Microchlamys spec. Diagnosis: Shell relatively high compared with all described species. The diameter is twice the height.

Read More »

Excentrostoma

Infraorder Excentrostoma Kosakyan et al., 2016   Diagnosis: Testate amoebae with an eccentrically placed aperture; test organic with few or many xenosomes. Family Centropyxidae Jung, 1942  

Read More »

Longithecina

Infraorder Longithecina Kosakyan et al., 2016   Diagnosis: Testate amoebae with a more or less tubular or cylindrical test and a terminal aperture; test with

Read More »