Original descriptions of taxa. For coccolithophores, and many calcispheres, these are pages from the Farinacci & Howe Catalog of Calcareous Nannofossils. In other cases (e.g. non-calcifying haptophytes) the data is directly compiled on this site. The "Catalogue of Calcareous Nannofossils" was originally compiled by Prof A. Farinacci 1969-1989, since 2000 it has been updated and extended by Richard Howe - see The Farinacci and Howe Catalog - an Introduction.
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Current identification/main database link: Chrysoculter rhomboideus Nakayama, Yoshida, Noël, Kawachi & Inouye 2005
Compiled data
Original Description
Etymology:
Extra details from original publication
Living cells of C. rhomboideus are usually slender spindle- to knife-shaped, 10–16 μm long, and 3–6 μm wide (Figs 1, 2, 5–7, 12). Cells are asymmetric in outline; one lateral side is somewhat swollen, and the opposite lateral side is flattened (Figs 2, 5, 12). Small cells with an asymmetrical ovoidal outline were sometimes observed (Fig. 3). The posterior end of the cell sometimes protruded as a short hyaline tail (Fig. 5). Two equal to subequal flagella (14–26 μm long) and a haptonema (4–10 μm long) emerged from the anterior tip of the cell (Figs 1–7, 12, 13). We did not observe a coiling haptonema. This alga was not an active swimmer, but it sometimes attached to the substratum by the anterior side of the cell or flagella. Two yellowish parietal chloroplasts were situated asymmetrically. One was situated at the anterior–lateral side of the cell, and the other was positioned at the posterior, opposite lateral side (Figs 1, 2, 5, 12, 13). The anterior chloroplast was usually situated in the swelling (Figs 2, 5, 12). The chloroplast contained three thylakoid lamellae but no girdle lamella and it was covered by periplastidal endoplasmic reticulum merging with the nuclear envelope (Figs 12, 14). Each chloroplast included an immersed pyrenoid traversed by a pair of thylakoids (Fig. 14). The nucleus was situated at the centre of the cell (Figs 1, 5, 12). Sections showed mitochondrial profiles with tubular cristae that probably represented a large reticulate mitochondrion (Figs 12, 13, 15). A Golgi body with typical dilated cisternae was located between the nucleus and the basal bodies, and the maturing face opened into the area between the basal bodies and the posterior chloroplast (Figs 12, 13, 52). Large posterior vacuoles without conspicuous contents were located at the posterior part of the cell (Fig. 13). Smaller vacuoles containing some material were present in the posterior to central part of the cell, and this type of vacuole was usually associated with rough endoplasmic reticulum (Figs 13, 15). Peripheral endoplasmic reticulum (PER) was distributed beneath the cell membrane (Figs 15, 38, 58). C. rhomboideus reproduced by binary fission of the swimming cell (Fig. 4), and sexual reproduction or occurrence of different stages was not observed.
Cell covering
One of the most distinctive features of C. rhomboideus was two layers of organic body scales. The inner layer consisted of scattered small elliptical scales (0.35 × 0.18 μm) with narrow rims (Figs 9–11, 69). Some images suggested that the small elliptical scales were distributed beneath the border of the outer scales (Figs 9, 10). The large rhomboidal scales (1.1 × 0.6 μm) of the outer layer had upright rims (50–80 nm) (Figs 9–11, 69). The rim of the rhomboidal scale has two tubular projections (0.3 μm long) at the longitudinal poles of the scale (Figs 9–11, 69). The large rhomboidal scales overlapped each other in a regular arrangement (Figs 6–8). Scales seemed to form a scale casing around the cell (Fig. 8), but they probably were not tightly attached to each other because shedded single scales were frequently observed. Both types of scales had faint radial but no concentric fibrils (Figs 9–11, 69). The scaly covering sometimes extended to the haptonema and the posterior extension (Figs 3, 7). Fibrous material covered the proximal portion of the flagella (Figs 16, 17). This material may be used to attach the cell to the substratum.
Nakayama, T., Yoshida, M., Noël, M. H., Kawachi, M. & Inouye, I. (2005). Ultrastructure and phylogenetic position of Chrysoculter rhomboideus gen. et sp. nov. (Prymnesiophyceae), a new flagellate haptophyte from Japanese coastal waters. Phycologia. 44(4): 369-383. gsReferences:
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Chrysoculter rhomboideus: Catalog entry compiled by Jeremy Young. Viewed: 17-2-2025
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