Nannotax3 - ntax_Farinacci - Hyalolithus neolepis

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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Citation: Hyalolithus neolepis Yoshida et al., 2006

Type specimens: Holotype: EM block TNS-AL 161040 deposited in the herbarium, Tsukuba Botanical Garden, National Science Museum, Tsukuba, Japan. Iso- type: Figure 2 A.

Type sample (& lithostrat): sample

Type locality: Shiribeshi Seamount, Hokkaido Prefecture, Japan (4313500200N, 13913301000E).

Farinacci catalog page (& compiler): n/a

Current citation: Hyalolithus neolepis Yoshida et al., 2006

Cells having at least two forms. Cells non-motile, spherical to subspherical, measuring 8-12 µm, having a posterior vacuole and hyaline hollow space. Two yellowish chloroplasts, each with an immersed pyrenoid. Nucleus central, Golgi body parabasal. Two short flagella, 1.5 µm at longest. A non-coiling haptonema, 12-18 µm long. Periplast covered with two different types of scales. The outer layer consisting of hat-shaped siliceous scales, oval to irregularly ellipsoidal in top view, measuring 5-7 and 4-6 µm across the axes, having many small pores (0.1-0.3 µm) in bulging central area. The brim of scales recurved, not perforated. The inner layer of organic scales, elliptical, measuring 0.6 and 0.4 µm across the axes, with 92-100 rough radial ridges and fine concentric patterns.

Motile phase cell subspherical to pear-shaped. Chloroplasts two, yellowish. Two equal flagella, 15-25 µm long. A non-coiling haptonema, 12-18 µm long. Periplast covered with short spine scales, oval to ellipsoidal in top view, with a maximum area of 2 and 3 µm across the axes, many small pores arranged in a radial pattern (72-120), ridge, marginal thickening.

Generic name refers to the material of the scales (Gr. hyalinus = glass, lithos = stone), and specific epithet means ‘‘novel scale’’.

Occurrence
Hyalolithus neolepis was present in surface water samples collected at Shiribeshi Seamount on July 22, 2001, during ‘‘the GELPOD cruise’’ on the research vessel Natsushima conducted by the Japan Agency for Marine Earth Science and Technology (JAMSTEC). During this cruise, sea- water samples at various depths were also collected by the submarine Shinkai 2000. The siliceous scales of H. neolepis were found in seven samples collected at depths of 150-1950m at Shiribeshi Seamount (data not shown).

Cell Structure
The living cells of H. neolepis were spherical to subspherical (Fig. 1) and were covered with numerous hat-shaped scales (Fig. 2) that were deposited in several layers; the cells measured 8-12 µm without the scale layers and 15-25 µm with the layers (Fig. 1 A). The cells were non-motile and either floated in the medium or stayed at the bottom of the culture vessels. The haptonema (12-18 µm) emerged from the anterior tip of the cell (Fig. 1B, arrowhead), and was unable to coil. Two short flagella (
The detailed structure of the haptonema and flagellar apparatus is described below. Two parietal yellowish chloroplasts were situated lateral to the axis of the haptonema and faced each other (Fig. 3A). These were surrounded by four membranes — two inner chloroplast membranes and two outer chloroplast endoplasmic reticulum (CER). Each chloroplast had an embedded pyrenoid aligned anterior— posteriorly that was traversed by a single thylakoid. The nucleus was situated in the middle of the cell (Fig. 3 A) and the outer nuclear membrane was continuous with the outer membrane of the CER (Fig. 3A, arrow). The Golgi body comprising a single dictyosome (Fig. 3 B) was situated near by the nucleus (Fig. 3A). Each cisterna of the dictyosome had a peculiar dilation (Fig. 3 B, arrow) appeared to be of the siliceous scales (Fig. 3 D). At the opposite side of the haptonema was a hyaline hollow space in which newly produced siliceous scales were present (see below).

Cell Covering
To ascertain the composition of the hat-shaped scales, optical anisotropy was verified using a polarizing microscope. As a control specimen with the double refraction characteristic, the cosmopolitan coccolithophorid Gephyrocapsa oceanica was used. As shown in Figure 4, the scales of H. neolepis did not show birefringence (Fig. 4A,B), while the coccoliths of G. oceanica showed typical bright quadrant patterns similar to a pinwheel caused by the birefringence of the calcium carbonate crystals (Fig. 4 C—E). To determine the elemental composition of the scales, an X-ray elemental analysis was conducted (Fig. 5). For comparison, Meringosphaera mediterranea, a heterokontophyte alga of unknown taxonomic position possessing twisted siliceous spines, and two coccolithophorids — Braarudosphaera bigelowii and Rhabdosphaera claviger — possessing coccoliths were examined. The results clearly showed that the major constituent of the hat-shaped scales (Fig. 5B) and the spines of M. mediterranea was silica (Fig. 5E), while that of the two coccolithophorids was calcium (Fig. 5 C,D).

The siliceous scales (Fig. 2C) comprised a bulged central area perforated by small pores that were 100—200 nm in diameter and a distinct, non-perforated, broad recurved brim that was approximately 400—600 nm wide. The bulged area was raised at two points (Fig. 2C, arrowheads); hence, the central area was slightly concave. The scales showed heavy overlapping, but were not interlocked with each other (Fig. 2 A).

Within the cell, the siliceous scales predominantly appeared in the vacuoles that were situated at the anterior side of the cell and associated with anterior cytoplasm where the nucleus and en- doplasmic reticulum (ER) were present (Fig. 3 A). Various stages of scale formation were observed at the boundary between the anterior cytoplasm and posterior vacuolar regions (Fig. 6). In the sections, the scales appeared as electron opaque structures formed of rectangular elements ar- ranged side by side in a single row, while those are round at the end of the brim (Fig. 6 E,F). Very thin scales representing the initial formation stage comprised small electron opaque granules that were probably of amorphous silica and were arranged in several rows (Fig. 6 G, arrows). Mature scales attained a thickness of 100nm. The vacuoles of this region might be continuous with the peripheral endoplasmic reticulum (PER) aligned beneath the cell membrane (Fig. 3 A), but we do not have clear evidence to confirm this. Without exception, the concave side of all the scales found within the cell faced the outside of the cell.

Whole-mount and sectioned material showed that several layers of organic scales deposited on the cell membrane beneath the siliceous scale layers (Fig. 7 A). These scales were elliptical with an area of 0.4 x 0.6 µm and a slightly incrassate rim; further, they had rough radial ridges (92—100) and fine concentric patterns on their surface that were visible only in thin sections (Fig. 7 B) and in uranyl acetate-stained material (Fig. 7C). We could not determine the faces of the organic scales, because both radial ridges and concentric patterns were very subtle. The scales had no spine or marginal ornament and were produced in the Golgi cisternae (Fig. 7 D).

Motile Cell Phase
Motile cells having two long flagella (15-25 µm) and a haptonema (12-18 µm) occurred in cultures that were maintained in a tentative oligotrophic MNK medium (Noël et al. 2004) and were incubated at 10°C. The motile phase was capable of vegetative growth through binary division. The motile cells lacked siliceous scales, but were coated with organic scales that were different from those of the non-motile cells (Fig. 13). Organic scales of the motile cells were elliptical to oval-tetragonal with a maximum area of 2.0 x 3.0 µm; however, these scales showed a wide variation in size. Organic scales were perforated by several small pores arranged in a radial pattern; these scales had a short spine (Fig. 13A,B,D, arrowheads) and a rimmed edge. Since the motile cells grow very slowly and easily transform into the non-motile cells with siliceous scales, even at constant culture conditions, it was difficult to obtain a sufficient amount of material for further observations in this study.

References:

Yoshida, M., Noël, M. -H., Nakayama, T., Naganuma, T. & Inouye, I. (2006). A Haptophyte bearing siliceous scales: Ultrastructure and phylogenetic position of Hyalolithus neolepis gen. et sp. nov. (Prymnesiophyceae, Haptophyta). Protist. 157(2): 213-234. gs

CATALOG - Hyalolithus neolepis

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