Smithsoniella J.R. Sears & S.H. Brawley, 1982

Holotype species: Smithsoniella earleae (Gallaher & Humm) J.R.Searles & S.H.Brawley

Original publication and holotype designation: Sears, J.R. & Brawley, S.H. (1982). Smithsoniella gen nov., a possible evolutionary link between the multicellular and siphonous habits in the Ulvophyceae, Chlorophyta. American Journal of Botany 69: 1450-1461.

Description: Thalli heterotrichous, uniseriate filaments to 10 mm in height. Erect axes unbranched or poorly branched with apical cell division. Cells in erect axes cylindrical, 7.5-11 &m diam. 40-110 &m long, in basal system slightly smaller and less uniform; septal plugs between adjoining cells, plasmodesmata absent. Basal filaments giving rise to additional prostrate axes laterally and erect axes at right angles. Hairs and hair-like structures absent in field collected plants, in culture plants developing attenuate, lightly pigmented filaments with age. Cells with single peripheral nucleus 2.5-3 &m diam. and prominent cell wall with two fibrillar layers. Chloroplasts single, a parietal perforate plate covering most of the interior wall; pyrenoids 4-7 per cell, traversed by a pair of thylakoids and surrounded by starch sheath. Asexual reproduction by zoospores formed in oval sporangia 22-27 &m diam. and 34-40 &m long, scattered on erect filaments; sporangia single and sessile on supporting cells with 4-16 (-24) quadriflagellate, pyriform zoospores 8-9 &m diam. with a pronounced 'beaked' apex and prominent red eyespot. After settlement zoospores geminate by forming an outgrowth from apical end, producing additional generation of filamentous plants. Sexual reproduction unknown.

Marine, known only from Florida on the Gulf of Mexico and St. Croix, U. S. Virgin Islands; probably more widely distributed in the Caribbean. Found at 1-2 m depth with coral fragments, epiphytic on Gracilaria tikvahiae, or submerged on a variety artificial structures where it forms a small turf.

Information contributed by: D. Garbary. The most recent alteration to this page was made on 2011-08-29 by M.D. Guiry.

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

Comments:

Uniquely among green algae, Smithsoniella possesses an incomplete septation during cytokinesis in which a septal plug develops. Plug with proteinaceous and polysaccharide cap layers and probably proteinaceous plug core. Plug core apparently membrane-bound. Affinities of Smithsoniella unknown and await critical observations of mitosis, cytokinesis and flagellar apparatus; genus likely represents an undescribed family and order.

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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=42543

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 29 August 2011. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 28 March 2024

 
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