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: Petasaria heterolepis Moestrup 1979Taxonomic rank: speciesType locality: Type micrograph: Fig. 62, from Kaikoura, New Zealand (173°42'E, 42°25'S), 13 September
1974.">">Farinacci catalog page (& compiler): n/a Current citation: Petasaria heterolepis Moestrup 1979
Original Description Unicellular with a single flagellum which is 6-7 µm long (Figs 61, 62). The flagellum is without Flimmer-hairs, but very thin hair-shaped appendages are present, probably mucilaginous. The cell body is rounded, 4-6 µm in diameter, as seen in whole mounts, and covered by a periplast of two different scale categories. One scale type (Figs 64, 65) is shaped like a wide-brimmed hat (Latin: petasus), and it contains mainly silica. These scales measure 1.7 x 1.9 µm - 2.9 x 3.2 µm, the base being circular or oval-triangular. Part of the base is patternless and lined by a raised rim (e.g., Fig. 65), the other part is patterned by perforations of various sizes. In this latter area, which lacks a raised rim, the largest perforations are nearest the scale periphery. Near the scale centre, always in the perforated area, each scale carries a hollow projection, somewhat higher than the raised rim. This projection on the side away from the patternless basal part of the scale is also patternless, towards this side, however, an ornamentation which in some cells consists of small spines (Fig. 65), in others of a more elaborate crest, also perforated (Fig. 63). The other scale type is unmineralised, more-or-less regularly circular, c. 0.45 µm in diameter (Figs 65 and 65, inset). In each scale eight arms radiate from the centre to the circular periphery. The arms are generally equally spaced, though sometimes more irregular. In the central part the arms are interconnected and this gives the scale an appearance like a spider's web. Size: Cell 4-6 µm; Etymology: scale shaped like a wide-brimmed hat (Latin: petasus); silicified scales 1.7 x 1.9 µm - 2.9 x 3.2 µm; organic scales circular, c. 0.45 µm Extra details from original publication This flagellate was one of the most interesting organisms found at Kaikoura, where it occurred commonly. The two completely different scale categories are not similar to any other known types of scales, except that the unmineralised type perhaps somewhat resembles the cobweb scales of certain prasinophycean flagellates, e.g., the body scales of Nephroselmis gilva (Parke & Rayns 1964, loc.cit., fig. 25, top). Regarding the larger scales, I was given the opportunity during a short visit in 1976 to Wenner-Gren's Institute in Stockholm to examine these in an analytical electron microscope. As expected, the histograms of the X-ray analysis (Figs 58, 59) very clearly showed the presence of silica in the scales, though more unexpectedly a small calcium peak was also present (the extra peaks in both histograms represent copper from the copper grids, gold from the shadow-casting material, etc.). A similar analysis of the nail-shaped scales from the colourless chrysophyte Paraphysomonas imperforata (Fig. 60), also expected to be siliceous, demonstrated the presence of silica, though in much smaller quantities (the scales are less dense), but calcium could not be detected.
Light microscopy and in particular thin sectioning for electron microscopy is very much needed for this remarkable organism, which based on present evidence can hardly be contained in any group of algal flagellates, nor does it show similarity to any zooflagellate known to me. A single cell with mineralised scales resembling those of Petasaria heterolepis was recently found by H. A. Thomsen (unpublished data) from the Gulf of Elat, and later he found another cell from Danish waters. The scales are of the same basic type as those from Kaikoura, though in the Elat specimen the number of perforations is somewhat higher, and the scales possess rows of knobs on the periphery (Fig. 66). Flagella were not visible in any of the two cells, nor were any spider-web scales seen. It is therefore slightly uncertain whether the specimens belong to the same or related species.
References:
Moestrup, Ø. (1979). Identification by electron microscopy of marine nanoplankton from New Zealand, including the description of four new species. New Zealand. Journal of Botany. 17: 61-95. gs
Petasaria heterolepis: Catalog entry compiled by Jeremy Young. Viewed: 17-2-2025