Chromera velia
not annotated - annotated - LINNAEUS only
20643581
Surface and flagella morphology of the motile form of Chromera velia revealed by field-emission scanning electron microscopy.
Chromera velia (Chromerida; Alveolata) is an autotrophic protist isolated from stony corals. Ch. velia possesses a chloroplast thought to be most closely related to the apicoplasts of non-photosynthetic apicomplexa. Phylogenetic analyses place Ch. velia as a close relative of parasitic apicomplexa and predatory colpodellids. We have used field-emission scanning electron microscopy of cells sputter-coated with gold or chromium and non-coated cells to characterise the surface ultrastructure of the motile form of Ch. velia. In overall morphology the biflagellated Ch. velia cells resemble the colpodellid Colpodella edax, but with some notable differences. The ventral side of the flagellated Ch. velia cell has two grooves extending from the anterior flagella insertion point with a ridge rising towards the anterior apex of the cell. The anterior flagellum is shorter than the posterior flagellum and possesses a distinct, small curved appendage. The insertion point of the anterior flagellum is partly enclosed by a flap extending from the cell. The posterior flagellum is approximately four times the length of the cell and possesses mastigonemes. The combination of coating techniques proved superior to the commonly used gold coating to determine fine surface ultrastructure. This new ultrastructural information for Ch. velia allowed us to emend its diagnosis.
20643580
Morphology and ultrastructure of multiple life cycle stages of the photosynthetic relative of apicomplexa, Chromera velia.
Chromera velia is a photosynthetic alga with a secondary plastid that represents the closest known photosynthetic relative of the apicomplexan parasites. The original description of this organism was based on brownish, immotile coccoid cells, which is the predominating stage of C. velia in the culture. Here we provide a detailed light and electron microscopy description of coccoid cells of C. velia and a previously undocumented bi-flagellated stage that is highly motile and moves in a characteristic zig-zag pattern. Transformation from a coccoid into a flagellate stage occurs in exponentially growing cultures, and is accelerated by exposure to light. The C. velia cells contain a pseudoconoid, which is likely homologous to the corresponding structure in the apical complex of Apicomplexa, cortical alveoli subtended by subpellicular microtubules, mitochondrion with tubular cristae, a micropyle, and a distinctive chromerosome, an apparently novel type of extrusion organelle. Ultrastructural analysis of the flagellate supports its close association with colpodellids and apicomplexans and provides important insight into their evolution.