Nannotax3 - ntax_Farinacci - Phaeocystis jahnii

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.
Taxa are sorted alphabetically for simple browsing, or you can use search boxes at the top & bottom of the page

Citation: Phaeocystis jahnii Zingone in Zingone et al. 1999

Type specimens: Holotype: Figures 26 to 31. Isotypes: Figures 23 to 25, Figures 32 to 39. Embedding PhaeoB5/IIa, Stazione Zoologica ‘Anton Dohrn,’ Naples, Italy. Authentic strain: B5, deposited at the Stazione Zoologica ‘Anton Dohrn,’ Naples, Italy.

Standardised type level: 160_HOLOCENE

Type locality: Tyrrhenian Sea, station MC, 2 miles offshore Naples (40°

Farinacci catalog page (& compiler): n/a

Current citation: Phaeocystis jahnii Zingone in Zingone et al. 1999

Cellulae cum flagellis rotundae 3.5–5 µm in diametro, depressione modica ad insertionem flagellorum. Flagella duo inequalia (8.5–12 et 5–6.5 µm) et brevis haptonema (3–4.5 µm). Chloroplasti duo aut quattuor, aureo-brun- nei. Stratum circa cellula, squamis tenuissimis et inequalibus in magnitudine compositum. Majores squamae externae et ovales, 0.35 x 0.28 µm, sine erecto margine, carinulis levibus et radiantibus ad marginem. Minores squamae interiores, margine inflexo, 0.18 x 0.14 µm. Fila desunt. Non mobiles cellulae observatae, solitariae vel glomeratae in duo aut quattuor, circumdatae a matrice polysaccharorum. Adsunt coloniae cum multis cellulis, sine definita forma aut conspicua margine. Coloniariae cellulae cum deminutis flagellis, sed squamis conservatis.

The species is named in honour of Professor Jahn Throndsen (University of Oslo, Norway), a famous specialist in flagellate taxonomy and patient teacher of three of the authors.

Species description: Light microscopy. Flagellate cells are rounded, 3.5 to 5 µm diameter, with a slight invagination at the flagellar insertion point (Figs. 23, 24). The two flagella are considerably unequal in size (8.5-12 µm and 5.5-6.5 µm, respectively), and a short, noncoiling haptonema (3-4.5 µm) is visible between them. Cells have two to four golden-brown parietal chloroplasts, and at times show a small, bright yellow-orange body in the space between the chloroplasts (Fig. 24). As in P. cordata, cells usually swim with the flagella pushing the cell, but in some cases the flagellar pole is directed forward. Filaments are not observed.

Colonies (Fig. 25) consist of a variable number of cells embedded in a transparent mucilaginous material that became more visible when stained with Alcian blue. Non-motile stages are found as single cells separated from the colonies. Colonial and single non-motile cells are usually larger than the flagellated cells, ranging from 6 to 8.5 µm, and have two to four chloroplasts. A single short appendage, possibly the haptonema, is often visible. Cells are not arranged in a particular order within the colonies. The shape of the colonies is irregular, especially that of the largest ones, and no clear envelope or denser outer layer is visible with or without staining. Often an air bubble is visible in large colonies. Colonial cells form relatively thick layers that stick to the glass culture tube at the air-medium boundary. Small colonies generally have two, four, eight, or 16 cells, implying that cell division within the colony may be synchronous. Some flagellated cells are seen trapped in the matrix, which could either be just forming from nonmotile cells or, conversely, transforming from motile into nonmotile cells.

Electron microscopy. With SEM, flagellates (Figs. 26, 27) show a rounded shape, two unequal flagella and the haptonema, and the slight depression at the region of the flagellar insertion point. The cell surface is slightly rough, but scales were not visible. Non-motile cells, either colonial (Figs. 28, 30, 31) or single cells (Fig. 29), appear more or less rounded and often show a slightly depressed pit that marks the emergence of the haptonema or an incomplete set of appendages of very reduced length (Figs. 29-31).

TEM whole mounts (Fig. 32) show the cell outline and the markedly unequal length of the two flagella. Scales appear very thin and delicate in whole mounts (Fig. 33) and in ultrathin sections (Fig. 34) and often are difficult to see. They are oval, with a scarcely visible pattern of radiating lines not reaching the central part of the scale. The external layer scales are larger (0.35 x 0.28 µm), lack an upraised rim, and often appear curved (Fig. 34). This is probably an artifact of their extreme thinness because thry may appear either flat or convex or concave. The underlying, smaller scales (0.18 x 0.14 µm) are also variously curved and have inflexed rims (Fig 34).

In ultrathin sections (Figs. 35-43), it is often difficult to distinguish nonmotile and colonial cells from flagellated stages, unless the complete flagellar set or the colonial matrix is clearly shown. In fact, incomplete flagellar sets and scales are often present in colonial cells (Figs. 37-40), and flagellated cells at times show peripheral vesicles (Fig. 36) similar to those found in colonial cells (Fig. 40). The microanatomy of the flagellated stages (Figs. 35-37) is basically the same as described for P. cordata. The main differences seen in ultrathin sections are the number of chloroplasts, which in P. jahnii can vary from two to four, and the scales. The orange body, which is at times visible in the light microscope (Fig. 24), may correspond to an electron-dense rounded body visible in some of the sections (Fig. 36). Colonial cells most often show three to four chloroplasts (Figs. 38, 39), a well-developed Golgi body, and a singular elongated mitochondrion. A large number of vesicles are present, more densely packed toward the cell margin. The contents of the vesicles appear to be discharged externally (Fig. 40).

Flagellate stages were rare in embedded material, and no transversal section was found clearly showing the alignment of the three appendages at the point of emergence with respect to the cell body. Sections through the basal bodies (Figs. 41-43) showed differently oriented flagellar roots, here indicated following Birkhead and Pienaar (1994), the central electron-dense core in the flagellar bases (Fig. 42), and the haptonemal base with nine microtubules (Fig. 43). A flagellar root originating from the right basal body was observed (Fig. 43), in a similar position as R6 in Imantonia rotunda Reynolds (Green and Hori 1986).

Distribution. Flagellate cells of P. cordata were often found in dilution cultures from the Gulf of Naples from autumn through spring but rarely in summer. The highest MPNs estimated for this species were 10⁵ cells/l in February and March 1990 and in April 1996. In formalin-fixed samples, Phaeocystis flagellates were poorly preserved and not easily identifiable. They have been noticed only in recent years, previously being lumped with other unidentified flagellates. In the light microscope, Phaeocystis flagellates often appeared very close to the typical five-rayed stars of filaments, which afforded identification and enumeration. As in dilution cultures, Phaeocystis cells were generally found from September through May in preserved samples from the Gulf of Naples (temperature 13.5°-22°C; salinity =37.4-38.2 psu), and were rarely recorded in summer months. The highest concentrations (Phaeocystis in years of observation of both bottle and net samples from the Gulf. It is not possible to exclude that both SDC and counts on fixed samples may include both P. cordata and P. jahnii cells. However, direct preparations of natural samples and observations of serial dilution cultures indicate that the species most often counted is P. cordata, whereas P. jahnii was identified only when it was isolated.

In TEM whole mounts of natural samples from the Gulf of Naples and of dilution cultures from the Sicily channel, we sometimes recovered filaments arranged in groups of nine, which is a distinguishing character for Phaeocystis scrobiculata. Flagellate cells laying close to these filaments had scales apparently thicker and at times larger (0.30-0.40 x 0.21-0.31 µm) than our two new species but smaller than those originally described for P. scrobiculata (Table 2)

References:

Zingone, A., Chrétiennot-Dinet, M. -J., Lange, M. & Medlin, L. (1999). Morphological and genetic characterization of Phaeocystis cordata and P. jahnii (Prymnesiophyceae), two new species from the Mediterranean Sea. Journal of Phycology. 35: 1322-1337. gs

CATALOG - Phaeocystis jahnii

References:

Add Comment

Comments