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Figure 5.

Species Name: Bacteriastrum comosum Pavillard
Common Name: None
Synonymy: None
  1. TAXONOMY

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Protista Bacillariophyta Mediophyceae - - Bacteriastrum

    Species Description

    Cells are united into chains, mostly 4-16 cells long, with a complex three dimensional structure.  Each cell is cylindrical, with a deep mantle (Fig.1, chain in girdle view, modified from Pavillard 1916).  The valve surface has a circular array of 6-8 setae that emerge from the valve in the axis of the chain, then turn perpendicularly to the chain axis and fuse with setae of the adjacent cell. At about one third the seta length, each fused seta bifurcates and bends toward the posterior end of the chain.

    The terminal cells of a chain are dimorphic. The upper terminal valve has 6-8 heavily siliceous non-bifurcate setae that spiral out from the valve (Fig. 2, SEM), and lie in the apical plane, often curving slightly up or down toward the axis of the chain. The lower terminal valve also has 6-8 heavily siliceous non-bifurcate setae (Fig. 3, SEM), but they curve strongly downward, becoming more or less parallel to the axis of the chain (Fig. 4, LM color). Both upper and lower terminal setae may have spirally arranged minute spines along their length (Fig. 2, 3). The upper terminal valve has a central rimoportula (Fig. 5, arrow; terminal valve interior).

    Cell diameters vary from about 6-24µm, with a pervalvar axis of 25-50µm.  There are numerous small discoid chloroplasts.  This is a tropical species, more common in neritic areas, but also oceanic in Atlantic, Pacific, and Indian Oceans. In the IRL, it was found rarely in the Jupiter Inlet area in August 2008 and in the Haulover Canal in October 2010.

  2. HABITAT AND DISTRIBUTION

    No information is available at this time

  3. LIFE HISTORY AND POPULATION BIOLOGY

    No information is available at this time

  4. PHYSICAL TOLERANCES

    No information is available at this time

  5. COMMUNITY ECOLOGY

    No information is available at this time

  6. ADDITIONAL INFORMATION

    No information is available at this time

  7. REFERENCES

    Pavillard J. 1916. Recherches sur les diatomées pélagiques du Golfe du Lion. Travail de l’Institut de Botanique de l’Université de Montpellier, Série mixte – Mémoire 5:7-62.

Unless otherwise noted, all images and text by PE Hargraves
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Page last updated: 28 April 2015

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