Heterophrys, W.Archer, 1869

Prokina, Kristina I., Zagumyonnyi, Dmitry G. & Tikhonenkov, Denis V., 2018, Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre, 1984) from Different Types of Freshwater Bodies in the Middle Russian Forest-steppe, Acta Protozoologica 57 (4), pp. 243-266 : 259

Heterophrys -like organism ( Fig. 7A–C )

Description: Organic spindle-shaped spicules are 2.75–7.57 µm in length, 0.05–0.09 µm in width. Spicules are slightly flattened and twisted along longitudinal axis, ends taper to pointed tips. Basal part of spicules submerged into mucopolysaccharide capsule, few axopodia are visible ( Fig. 7A ).

Remarks: Organisms with organic spindle-shaped spicules were previously found in both fresh and marine waters and identified as species of Heterophrys , Marophrys , and Sphaerastrum ( Mikrjukov 2002, Cavalier-Smith and von der Heyden 2007). However, re- cent studies have revealed a close similarity between spicule-bearing Heterophrys -like organisms and scalebearing species by both molecular (18S rDNA sequenc- es of Polyplacocystis species is similar to sequence of Heterophrys -like organism) and morphological data (presence of intermediate forms possessing characteristic Raphidiophrys glabra plate scales and spicules at the same time) (Zlatogursky 2016, Zlatogursky et al. 2018). Based on these observations, Zlatogursky with coauthors ( Zlatogursky et al. 2018) have suggested dimorphism of the life cycle in centrohelids with the presence of scales-bearing and spicules-bearing stages. So, Heterophrys -like organism can be a stage of the life cycle of some other centrohelid species.

Figures

Fig. 7. Morphology of observed scales of unidentified species (TEM): A–C – Heterophrys-like organism (A – from plant debris and silt of Usman’ River; B, C – from plant debris and silt of Lake Krugloye; A – whole cell; B, C – spicules), D–F – unidentified Centrohelea sp. (from water column of Lake Vosmerka; D – scales of the single cell; E, F – plate scales). Abbreviations: sp – spicules. Other abbreviation as in Fig. 1. Scale bars:A, D – 10 µm; B, C, E, F – 1 µm.