Streptonema Wallich, 1860

Holotype species: Streptonema trilobatum Wallich

Original publication and holotype designation: Wallich, C.G. (1860). Descriptions of Desmidiaceae from Lower Bengal. Annals and Magazine of Natural History, Series 3 5: 184-197, 273-285, pls XIII, XIV.

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Description: Cells deeply constricted, smooth-walled, trilobed in end view (rarely quadrilobate) with lobes slightly asymmetric. Cell united into filaments by three short, hollow, apical processes (one near base of each lobe), each joined to similar process from adjacent cell of filament by firm, elongate-cylindrical structure with median transverse suture. Linking structures of unknown composition, but usually described as gelatinous. Chloroplast one per semicell with broad extensions into the three lobes. Pyrenoids 4, one axial and one near end of each chloroplast lobe. Isthmus unusual in being distinctly triangular in transverse section. Asexual reproduction probably by cell division similar to Desmidium; process poorly known in Streptonema but stages observed in field samples show replicate wall involved in formation of apical processes (identical to some Desmidium species). Sexual reproduction by conjugation of cells detached from filaments. Distinct conjugation tube present, both gametes moving into tube. Mature zygospores subspherical to ovoid and smooth-walled. Type species of Streptonema tropical, endemic to Indo-malaysian-Australian region; in acidic swamps, ponds and lakes. S. quadrangularis from Malaysia considered quadrilobate variant of type species. S. bourrellyi occurs in South America but details of habitat unpublished.

Information contributed by: J.F. Gerrath. The most recent alteration to this page was made on 2013-09-12 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Guiry, M.D. (2013). Taxonomy and nomenclature of the Conjugatophyceae (=Zygnematophyceae). Algae. An International Journal of Algal Research 28: 1-29.

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Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=43548

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 12 September 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 29 March 2024

 
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