Nannotax3 - ntax_Farinacci - Chrysochromulina microcylindra

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: Chrysochromulina microcylindra Leadbeater 1972

Type specimens: Type drawing Fig. 1C

Type sample (& lithostrat): Found on 9 August 1970 in a sea water sample taken from a depth of 5 m

Standardised type level: 160_HOLOCENE

Type locality: approximately 30 km NW of Bergen, Norway

Farinacci catalog page (& compiler): n/a

Current citation: Chrysochromulina microcylindra Leadbeater 1972

Cells subspherical, 4-7 µm diameter; flagella 2 equal, 20-25 µm long and a haptonema, 16-30 µm long when extended. Scales of two types, inner scales plate-like, oval to sub circular, length 0.6-1.0 µm, breadth 0.5-1.0 µm, thin with a cruciform plane centre and a pattern of radiating ridges visible on both surfaces but the ridges covered with a thin band of concentrically striated material on the distal surface near the edge. Outer scales cylindrical straight-sided, very thin, diameter 0.1-0.2 µm, length very variable 0.5-3.0 µm, arising centrally from a stouter radially striated base plate diameter 0.4-0.5 µm; base plates without attached cylinders frequent. 2 lateral orange chloroplasts with non-projecting pyrenoids.

Cellula subsphaerica, 4-7 µm diam.; flagella 2 aequalia, 20-25 µm longa; haptonema 16-30 µm longum. Squamae dimorphae. Squama strati interioris laminaris, ovalis vel suborbicularis, 0.6-1.0 µm longa, 0.5-1.0 µm lata, tenuis, area centrali plana, circllm eam carinis radiantibus utrinque visibilibus ornata, clava tenui concentrice striata ultimas partes carinarum extra obtegente. Squama strati exterioris cylindrica, lateribus rectis, tenuissima, 0.1-0.2 µm diam., longitudinis pervariae, 0.5-3.0 µm Zonga, e lamina basali crassiore, 0.4-0.5 µm diam., radiatim striata oriens, laminis basalibus cylindris carentibus multis observatis. Chloroplasti 2 pallideflllvi, laterales, pyrenoida non projecta gerentes.

This species was occasionally found in plankton samples from Hjeltefjorden and rarely in samples from Herdlefjorden (for further details see LEADBEATER 1972). It was also obtained in culture in N orwa y and later in unialgal culture in Birmingham.

The subspherical cell, approximately 4-7 ,µm in diameter, possesses a haptonema more or less equal in length to the flagella (Figs. 1C, 10). When coiled, the haptonema forms approximately 6 gyres (Fig. 11). In shadowcast whole mounts this species is readily recognised by its general resemblance to C. megacylindra except that the cylinder scales have consistently different relative proportions; the circular base plates are more massively constructed and the cylinder itself is both relatively and absolutely narrower and longer. The plate scales (Fig. 12) are very similar to those of C. megacylindra and need not be separately described.

The base plates of the cylinder scales on the other hand are slightly smaller in overall dimensions, but conspicuously more opaque. The central circular area delimiting the place of attachment of the cylinder occupies less than a third of the diameter of the plate as opposed to more than three-quarters in C. megacylindra.

The patterning on the base plate is exceptionally coarse, the periphery of the proximal face being conspicuously ridged (Figs. 13, 14, 17) while that of the distal face is smooth, with some irregular radial perforations near the margin (Figs. 15, 16). The much more delicate striations of the thin centre of the base plate are frequently visible on both surfaces though sometimes obscured on the proximal surface by mucilage, especially in cultured material (e.g. Fig. 14). The length of the cylinders was usually less in wild material (0.5 µm; Figs. 19, 20) than in culture where they could reach 3.0 µm (Fig. 13). Scales without cylinders but bearing a similar patterning to the base plates of the cylinder scales were common on cultured specimens (Figs. 17, 18). The central thinner region of the proximal surface and the hole on the distal surface were then absent; the patterns of radial ridges and perforations extended further towards the centre.

Sections of cells fixed with osmium tetroxide or postosmicated glutaraldehyde lacked the covering of scales (Figs. 24, 34) although occasionally a rather poorly preserved group of detached cylinder scales was encountered (Figs. 22, 23); the extreme thinness of the cylinder wall can then be seen contrasting with densely staining base plates (Fig. 23). The structure of the cylinder scales is better understood by observing completed scales within the cell (Figs. 24, 30-33). The base plate is composed of two thick densely staining layers joined at the periphery but slightly separated towards the centre (Figs. 24, 31, 32). The thinner centre of the lower layer forms the base of the cylinder (Fig. 32).

Both plate and cylinder scales are produced within the Golgi apparatus (Figs. 24-33). The latter is curved and has certain clearly distinguishable regions (Fig. 25). The quiescent portion (upper left) is composed of somewhat contorted cisternae with dark-staining contents. The mid-portion often contains swollen cisternae whilst those at the other end of the stack (lower right Fig. 25) contain both plate and cylinder scales. Vertical sections of the Golgi apparatus show that the plate scales are usually orientated with their proximal surfaces facing the same direction, although variations to this are quite common (Fig. 26). This may result from the interpolation of plate scale containing cisternae from other parts of the Golgi apparatus. The cisternae containing cylinder scales are frequently located perpendicularly to those containing plate scales (Figs. 3A, B, 27-29) and often they may be confluent (Figs. 28, 29). A diagrammatic reconstruction of this arrangement is shown in Fig. 3C. During formation of a cylinder scale a plug of densely staining material bounded by a single membrane fills the centre of the cylinder (Figs. 27, 31, 32). This membrane is continuous with that bounding the Golgi cisterna (Figs. 3B, 33). Another membrane delimiting dense material, can sometimes be seen entering the plug (Fig. 33) or surrounding a hollow centre (Fig. 29). It is not known at what stage in development the plug disappears but mature scales are empty (Fig. 22).

Cisternae containing mature plate and cylinder scales are swollen and contain irregularly bloated tubes (Figs. 30, 31, etc.). The latter are a common feature in the cisternae containing mature scales in Chrysochromulina chiton (MANTON 1967; see also MANTON 1972b).

The remainder of the cell organelles (Figs. 24-34) are similar to those found in other species of Chrysochromulina and other members of the Haptophyceae. The two peripheral chloroplasts possess sunken pyrenoids. Unfortunately, it was not possible to obtain sections of the haptonema and thus the number of microtubules, an important taxonomic feature, has not been ascertained.

References:

Leadbeater, B. S. C. (1972a). Fine structural observations on six new species of Chrysochromulina (Haptophyceae) from Norway with preliminary observations on scale production in C. microcylindra sp. nov. Sarsia. 49: 65-80. gs

Leadbeater, B. S. C. (1972b). Identification, by means of electron microscopy, of nanoplankton flagellates from the coast of Norway. Sarsia. 49: 105-132. gs

Manton, I. (1967). Further observations on scale formation in Chrysochromulina chiton. Journal of Cell Science. 2: 411-418. gs

Manton, I. (1972). Scales and scale production in pigmented flagellates, a historical progress report. In, Robards, A. W. (ed.) Aspects of dynamic fine structure. McGraw Hill, London -. gs

CATALOG - Chrysochromulina microcylindra

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