Rhodochaete Thuret ex Bornet, 1892
Holotype species: Rhodochaete pulchella Thuret ex Bornet
Original publication and holotype designation: Bornet, E. (1892). Les algues de P.-K.-A. Schousboe. Mémoires de la Société des Sciences Naturelles et Mathématiques de Cherbourg 28: 165-376, pls I-III.
Request PDFDescription: Freely branching filamentous thalli to several mm in height. Cells cylindrical to slightly barrel shaped, (20-)25-50(-75) µm long and 10-20 µm diameter; in gametophytes cells narrower and longer and less regular in shape than sporophytes. All filaments with apical cell division; branching initiated at irregular intervals along axis in upper portions of cells, with single branch per supporting cell. Gametophytic plant a single erect axis attached to downward growing rhizoidal filament; sporophytic plants with prostrate axis producing a number of erect filaments. Cell walls prominent, in fine structure densely fibrillar, walls thinner in gametophytic plants and less prominent at tips of apical cells. Cells with single central nuclei and numerous floridean starch grains; chloroplasts numerous per cell and discoid to elongate or irregularly lobed, without pyrenoids and with peripheral encircling thylakoids.
Asexual reproduction by monospores 12-15 µm diameter, formed in lateral sporangia cut off with a curved wall in upper to middle portions of intercalary branch cells. Monosporangia formed by either gametophytic or sporophytic stages; monospores germinate to repeat parental phase. All spores and spermatia released by tear in sporangial cell wall. Sexual reproduction oogamous. Gametophytes bisexual with all cells, except those at the base potentially forming spermatangia or carpogonia. Gametophytes can begin forming spermatangia when erect axes only 3-4 cells. Spermatangia lateral, cut off singly from vegetative cells with a curved wall, each releasing a single naked spermatium, ca. 5 µm diameter. Carpogonia morphologically undifferentiated from vegetative cells; following fertilization undergoing a single mitotic division by means of a curved wall to produce a single-celled lateral carposporophyte that liberates a single carpospore, about 15 µm diameter. Life history variously interpreted as either biphasic and without a carposporophyte, or triphasic with single celled carposporophyte generation. Gametophytic and sporophytic stages slightly different morphologically. Gametophytes developing following bipolar germination to form prostrate rhizoidal axis and erect axis; spores giving rise to sporophyte with unipolar germination to develop prostrate axis. Chromosome numbers of 4 and 8 reported for gametophytic and sporophytic stages, respectively. Meiosis and formation of meiospores not well understood, although only a single spore released from each sporangium. All life history, experimental and ultrastructural studies were carried out on a single isolate from Villefranche-sur-mer, France and another from Point Lonsdale, Victoria, Australia.
During development apical cells undergo tip growth; after cells are cut off they undergo little cell elongation and this is by diffuse cell wall deposition. Pit plugs are similar to Compsopogon, comprising a plug core devoid of either cap layers or plug membrane. Pit plugs 1.2-1.8 µm long in sporophytes; about half as large in gametophytes. Other ultrastructural features include the association between endoplasmic reticulum and the forming face of dictyosomes, the presence of dictysomes close to the nucleus, the occurrence of microbody like structures near nuclei, and the absence of an association between mitochondria and dictyosomes.
Information contributed by: D.J. Garbary; modified by M.D. Guiry. The most recent alteration to this page was made on 2017-01-19 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: Zuccarello, G., West, J., Bitans, A. & Kraft, G. (2000). Molecular phylogeny of Rhodochaete parvula (Bangiophycidae, Rhodophyta). Phycologia 39(1): 75-81, 5 figs, 1 table.
Comments: Rhodochaete is found in the subtidal zone only from the Mediterranean Sea and the Caribbean, and from Victoria, Australia; in France, as epiphyte on Acrosymphyton, in Jamaica on Naccaria, and in Victoria on Palmophyllum. These are widely divergent localities but the species is rarely reported, which may reflect its small size and epiphytic habit.
Rhodochaete is of major phylogenetic significance in providing an archetype for vegetative and reproductive morphology and development in red algae.
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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=39727
Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 19 January 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 22 November 2024
