Capsosiphon Gobi, 1879

Holotype species: Capsosiphon aureolus (C.Agardh) Gobi

Currently accepted name for the type species: Capsosiphon fulvescens (C.Agardh) Setchell & N.L.Gardner

Original publication and holotype designation: Gobi, C. (1879). Berichte über die algologische Forschungen in finnischen Meerbusen im Sommer 1877 ausgeführt. Trudy Leningr. Obshch. Estest. 10: 83-92.

Description: Thalli tubular with walls of tube one cell thick, and either cylindrical or compressed. Thick, gelatinous intercellular matrix between cells. Cells frequently in groups of 2 and 4, enclosed in a cell wall matrix derived from a common mother cell. Cells often in distinct longitudinal and horizontal series at least in lower part of thallus, longitudinal series loosely associated, sometimes separating. Thalli attached by a disc of rounded cells or rhizoidal extensions of basal cells. Thalli generally less than 10 (-13) cm long and 2 cm wide. Cells nearly isodiametric, from 4 to 22 ┬Ám in diameter. Single parietal chloroplast with either a single conspicuous pyrenoid or several small pyrenoids. Life history probably a heteromorphic alternation of tubular gametophytes and cyst-like sporophytes; alternation between isomorphic gametophytes and sporophytes also reported, but needs to be confirmed through cytological studies. Asexual reproduction of tubular thalli by quadriflagellated zoospores, aplanospores, and/or biflagellated swarmers that may represent parthenogenetic gametes. Sexual reproduction by biflagellated isogametes released from unisexual (C. groenlandicum) or bisexual gametophytes (C. fulvescens). Quadriflagellated and biflagellated swarmers sometimes observed from same thallus. All but basal cells of tubular thallus capable of becoming reproductive. Swarmers leave mother cells enclosed within a hyaline envelope through a pore or slit in external wall. Envelope remains attached to surface of mother cell until swarmers burst out moments later. Asexual reproductive cells develop into tubular thalli similar to parent thalli. Zygotes reported to develop into tubular thalli isomorphic with gametophytes and/or into unicellular cyst-like sporophytes that produce aplanospores or quadriflagellated zoospores. Spores develop into tubular thalli. Meiosis assumed to occur during sporogenesis in the cyst-like sporophyte, but this has not been demonstrated. Sexual reproduction not observed in some isolates. Tubular thallus initially an uniseriate filament that reaches lengths of up to 80 cells before longitudinal divisions produce a pluriseriate thallus. Continued longitudinal divisions of cells produce a ring of cells in transverse section. The tubular, hollow thallus forms from separation of cells along the longitudinal axis.

Information contributed by: C. Tanner. The most recent alteration to this page was made on 2019-04-11 by Wendy Guiry.

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

Gender: This genus name is currently treated as masculine.

Most recent taxonomic treatment adopted: Cormaci, M., Furnari, G., & Alongi, G. (2014). Flora marina bentonica del Mediterraneo: Chlorophyta. Bollettino dell'Accademia Gioenia di Scienze Naturali di Catania 47: 11-436.

Comments: Cosmopolitan in temperate waters. Epilithic and on other hard substrates. Forming tangle masses of green, yellowish-green or brownish-green fronds, favouring habitats with brackish water, but also in full strength seawater. Often above the high tide mark in areas of freshwater run-off. The morphology and development of the tubular thallus of Capsosiphon superficially resembles that of Enteromorpha and Blidingia. However, Capsosiphon differs from these genera in the arrangement of cells, and in its life history. The presence of a cyst-like sporophyte in C. groenlandicum and in at least some populations of C. fulvescens suggests affinities with Monostroma and other algae in the Ulothricales.

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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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Wendy Guiry in Guiry, M.D. & Guiry, G.M. 11 April 2019. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 06 December 2023

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