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Name derivation:

“Thread-bare thread” – Tribon = thread-bare; -nema = thread

 

Classification:

Tribonema  Derbès  and Solier  1851;  28 of 64 species descriptions are currently accepted taxonomically (Guiry and Guiry 2013).

Order Tribonematales; Family Tribonemataceae

 

Morphology:

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.

 

Similar genera:

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.

 

Asexual Reproduction Only

No sexual reproduction has been reported for Tribonema (Zuccarello and Lokhorst 2005).

 

Molecular phylogeny of species:

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.

 

Habitat:

Common in standing waters, often the only early spring filamentous alga of temporary pools.  Also found in rivers.

 

Tolerance of heavy metals:

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.

 

References:

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.