Heliospora cf. longissima (von Sieboldon Kölliker, 1848)

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 : 247-249

Heliospora cf. longissima from Eulimnogammarus verrucosus ( Fig. 4).

The transversal and longitudinal sections were studied. Unfortunately, the fixation was not very successful, and these samples could not be recollected. The cross-sections demonstrated pellicular epicytic club-shaped folds with swollen tops containing about 5 apical filaments and 4–6 hardly discernible apical arcs ( Fig. 4A, B). The apical filaments face spaces between the apical arcs rather than the apical arcs themselves. The height of the folds varies from ~260 to ~ 500 nm, depending on location of the section: closer to the posterior end of the cell the folds are significantly lower than in the middle of the body, while the thickness remains the same (~ 140 nm tops and ~ 90 nm stems). Micropores were not observed. The subjacent layer of the pellicle was well developed, however, unlike C. cf. communis it is less electron-dense; its thickness was about 45 nm. The subdivision of the cytoplasm into ecto- and endoplasm was not observed. Large (up to 0.75 μm) carbohydrate granules come close to the subjacent layer under the pellicle.

The longitudinal sections of the two separated syzygy partners, primite and satellite, were also studied (the syzygy was fragmented during the embedding procedure). The primite demonstrates differences of cytoplasm structure between its epimerite, protomerite, and deutomerite ( Fig. 4C), despite the section missing the very apex of the cell. Just basal part of epimerite is present on the section; its cytoplasm looks homogeneous and does not contain any organelles or inclusions. A distinct septum between the epi- and protomerite is apparently absent ( Fig. 4C). The protomerite cytoplasm is subdivided into two zones: anterior and posterior. The anterior zone looks darker and more homogeneous; the posterior zone is lighter and apparently contains many membranous structures ( Fig. 4D, E). The protomerite contains large electron-dense globules ( Fig. 4C, D), which are arranged mainly near its approximate anterior and posterior borders. However, several ones may be observed in the middle part. Such globules in the deutomerite as well, and they also occur near the deuto-/ protomerite interface, which may be observed as a (barely) visible, loose septum presumably consisting of thin fibrils ( Fig. 4E). There are many large amylopectin granules within the deutomerite, unlike the epimerite and protomerite.

The fine structure of the satellite forebody sharply differs from that of primite. There is no epimerite. The protomerite is separated from the deutomerite by a thick granulated (or fibrillar) zone of the cytoplasm, which looks like a septum. The protomerite of the satellite contains no amylopectin grains, while the deutomerite is rich with them. The protomerite of the satellite is highly vacuolated. The vacuoles are large, electronlight, and contain large electron-dense globules ( Fig. 4F, G).