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Name derivation: |
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“Thread-bare thread” – Tribon = thread-bare; -nema = thread
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Classification: |
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Tribonema Derbès and Solier
1851; 28 of 64 species
descriptions are currently accepted taxonomically (Guiry and Guiry 2013). Order
Tribonematales; Family Tribonemataceae
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Morphology: |
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Cells are cylindrical and barrel-shaped, two to five
times longer than wide, and form unbranched filaments. The wall of the
filaments forms a line of H-shaped segments. Protoplasts are uninucleate
and contain few to many discoid chromatophores without pyrenoids.
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Similar genera: |
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Tribonema and Microspora (Chlorophyceae) are similar in appearance, with
filament walls made up of H-pieces. They can be distinguished by the presence
(in Microspora) or absence (in Tribonema) of starch granules.
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Asexual Reproduction Only |
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No sexual reproduction has been reported for Tribonema (Zuccarello and Lokhorst
2005).
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Molecular phylogeny of species: |
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Ten
species of Tribonema were examined
with plastid-encoded rbcL gene
sequences, eight of which are polyphyletic (Ibid.). If species lists are based on morphological
descriptions and ignore molecular phylogenetic relationships, the entire
estimation of species diversity is called into question. The authors encourage both additional
multilocus sequence comparisons and better morphological discrimination to
better define and describe species.
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Habitat: |
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Common in
standing waters, often the only early spring filamentous alga of temporary
pools. Also found in rivers. |
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Tolerance of heavy metals: |
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At least some species of Tribonema
are found in metal-polluted streams such Gessen Creek that drains the former
uranium-mining district of Ronneburg, Germany. The filaments are encrusted with iron oxides
associated with ferrous (Fe+2) oxidizing Gallionella-related bacteria (Mori et al. 2015). Iron
encrusted Tribonema sp. in Gessen
Creek, Ronneburg Germany. From Mori et al. 2015. |
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References: |
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Derbès, A. and A.J.J. Solier 1851. Algues. In:Supplément au catalogue des plantes qui croissant naturellement aux environs de Marseille. (Castagne, J.L.M. Eds), pp. 93-121. Aix: Nicot and Pardigon. Mori, J.F.,
T.R. Nau, W. Lu, M. Handel, K.U. Totsched, and K. Kusel 2015.
Iron encrustations on filamentous algae colonized by Gallionella-related bacteria in a
metal-polluted freshwater stream.
Biogeosciences Discussions 12:7705-7737. Smith,
G.M. 1950. The fresh-water algae of the United States.
McGraw-Hill, 2nd ed. Zuccarello,
G.C. and G.M. Lokhorst 2005. Molecular phylogeny of the genus Tribonema (Xanthophyceae) using rbcL gene sequence data: monophyly of morphologicaloly simple algal
species. Phycologia 44(4):384-392. |