Cephaloidophora cf. communis, Mawrodiadi, 1908

Simdyanov, Timur G., Diakin, Andrei Y. & Aleoshin, Vladimir V., 2015, Ultrastructure and 28 S rDNA Phylogeny of Two Gregarines: Cephaloidophora cf. communis and Heliospora cf. longissima with Remarks on Gregarine Morphology and Phylogenetic Analysis, Acta Protozoologica 54 (3), pp. 241-262 : 246-247

Cephaloidophora cf. communis ( Fig. 3)

The cross-sections through the middle of the cell demonstrated a typical eugregarine tegument structure: a trimembrane pellicle (~ 30 nm thick) covered by a cell coat (~ 10 nm thick), forming numerous epicytic folds ( Fig. 3A–C). Cross-sections of the folds show a finger-like shape: they have parallel lateral sides and slightly swollen rounded tops. The height of the folds significantly varies from ~ 400 nm in the middle of the body to ~ 260 nm (and probably less) closer to the anterior end of the cell, while the thickness of the folds remains the same and averages ~ 130 nm (tops) and ~ 100 nm (stems). There are three distinct apical arcs in the fold tops and two apical filaments, which are very difficult to detect; however, it is possible to discern them in some photos ( Fig. 3B, C). The two apical filaments face spaces between the three apical arcs (they are not in front of apical arcs themselves). Beneath the pellicle is a layer (35 nm thick) forming crossbars at the bases of the folds ( Fig. 3B). Micropores are located at the bottom of the grooves between the folds ( Fig. 3B), without any regular pattern.

The cytoplasm is subdivided into ecto- and endoplasm. This stratification in gregarines is caused by the absence or presence of storage carbohydrate (amylopectin) grains, respectively ( Vivier 1968). The thickness of the ectoplasm, free of amylopectin grains, was about 1 μm. The endoplasm contains numerous amylopectin grains, rounded shape up to 0.7 μm in diam- eter ( Fig. 3A). The cytoplasm also contained numerous vacuoles with dense inclusions.

Longitudinal sections of the cell demonstrated two distinct septa: one between the epi- and protomerite and another between the proto- and deutomerite ( Fig. 3D, E, G–I). Both septa appear to be fibrillar in nature ( Fig. 3G, H, I). No contacts were observed between the septa and the pellicle ( Fig. 3H). The anterior and middle parts of epimerite are filled by unusual objects, which look similar to micronemes (typically absent in gregarine trophozoites and gamonts) and tightly adjoin one another ( Fig. 3F). There are pores in the epimerite pellicle previously observed by SEM ( Rueckert et al. 2011b). Probably, the homogenous content of the microneme-like objects can be released through these pores ( Fig. 3F). The posterior part of the epimerite cytoplasm comprises electron-translucent vacuoles ( Fig. 3H). The protomerite cytoplasm has a foam-like structure ( Fig. 3G, H, I), possibly formed by highly developed endoplasmic reticulum. Additionally, there are lipid drops and amylopectin grains in the middle and in the rear part of the protomerite ( Fig. 3E). The number of these inclusions increased towards the posterior, and were in particularly high abundance in the deutomerite ( Fig. 3D, E).