Phymatodocis Nordstedt, 1878
Holotype species: Phymatodocis alternans Nordstedt
Original publication and holotype designation: Nordstedt, C.F.O. (1878 '1877'). Nonnullae algae aquae dulcis brasilienses. Öfversigt af Kongl. Vetenskaps-Akademiens Forhandlingar 1877(3): 15-28, 2 pls.
Request PDFDescription: Cells united in short or long filaments. Cells quadrate to rectangular in lateral view, with moderately deep median constriction (isthmus). In apical view each semicell 4-lobed (rarely 3- or 5-lobed). Lobing symmetric except P. irregulare (two long and two short lobes). Cell wall of two pieces overlapping at isthmus. Open cylindrical pores typical of Cosmarium-type desmids, absent in P. nordstedtiana, the wall structure resembling Penium or Closterium, with dense matrix embedded among crossed bands of microfibrils. Funnel-shaped pores resemble those in Closterium, with narrow outer opening and broader inner region traversed by microfibrils. Chloroplast oneper semicell with one or two pyrenoids and two broad, flattened lobes extending into each lateral lobe of semicell. Nucleus in isthmus. Asexual reproduction by cell division and new semicell morphogenesis typical of desmids (see Cosmarium). P. nordstedtiana unique in that primary wall shed as small pieces very early, before full differentiation of new semicells (as opposed to after differentiation). Sexual reproduction observed in two species, by conjugation between cells that remain attached in filaments or dissociate. Gametes fuse within broad conjugation tube; mature zygospore irregularly quadrangular. Phymatodocis species all rare, usually in acidic, oligotrophic lakes in tropical or subtropical regions; one species extends to boreal forest of Canada. The taxonomic position of Phymatodocis uncertain. Wall ultrastructure suggests position intermediate between Cosmarium-type and Penium-type desmids. Further studies, including observations of type species needed to resolve this problem.
Information contributed by: J.F. Gerrath. The most recent alteration to this page was made on 2018-12-18 by M.D. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Gender: This genus name is currently treated as feminine.
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=43540
Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 18 December 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 18 April 2024
