Mesostigma Lauterborn, 1894

Holotype species: Mesostigma viride Lauterborn

Original publication and holotype designation: Lauterborn, R. (1894). Ueber die Winterfauna einiger Gewässer der Oberrheinebene. Mit Beschreibungen neuer Protozoën. Biologische Centralblatt 14: 390-398.

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Description: Flat to saddle-shaped flagellates with 2 flagella emerging from a pit in the convex dorsal side. The ventral side somewhat concave. The flagellar pit is located near the front end, and the flagella are directed more or less anteriorly in the swimming cell which rotates rapidly during swimming. A single parietal chloroplast covers the ventral and lateral sides and extends onto the dorsal side. A single eyespot on the ventral side, near the mid axis of the cell. Several contractile vacuoles near the flagellar bases. Two pyrenoids present in the type species, while the other species lacks pyrenoids. The cell and flagella covered with several types of scales. Scales of the outermost layer on the cell body are sufficiently large to be visible under the light microscope. Two additional layers of scales present in M. viride. The flagella of M. viride covered with a single type of scales, while hair-shaped scales appear to be lacking. Sexual reproduction unknown. This remarkable genus of prasinophytes occurs in many types of fresh water. The two species differ in size and in the presence/absence of pyrenoids. Ultrastructural studies on Mesostigma viride were published by Manton and Ettl (1965) and, more recently, by Rogers and others (1981) and Melkonian (1989), with emphasis on the structure of the flagellar apparatus. Mesostigma is phylogenetically most closely related to Pyramimonas, but its many unique features make it one of the most distinct prasinophycean flagellates. For a taxonomic treatment, see Ettl (1983).

Information contributed by: Ø. Moestrup. The most recent alteration to this page was made on 2023-10-31 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 neuter.

Most recent taxonomic treatment adopted: Marin, B. & Melkonian, M. (1999). Mesostigmatophyceae, a new class of streptophyte green algae revealed by SSU rRNA sequence comparisons. Protist 150: 399-417, 9 figs, 2 tables.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in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.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 31 October 2023. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 15 June 2024

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