Akkesiphycus Yamada & Tak.Tanaka, 1944

Holotype species: Akkesiphycus lubricus Yamada & Tanaka

Original publication and holotype designation: Yamada, Y. & Tanaka, T. (1944). Marine algae in the vicinity of the Akkesi Marine Biological Station. Scientific Papers of the Institute of Algological Research, Faculty of Science, Hokkaido Imperial University 3(1): 47-77, pl. 8.

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Description: Erect thalli epilithic, attached with a small discoidal holdfast, up to 3 m in length, olive yellow to brown, simple foliose often with longitudinal tear, without obvious stipe, degenerating rapidly when exposed to the air or immersed in fresh water, solid, composed of medullary layer with inner hyphal filaments, peripheral layer with 3-5 celled assimilatory filaments. Phaeophycean hairs present. Unilocular sporangia ovate, sessile. Special mucilagenous organs absent. Chloroplasts, many, discoid, without pyrenoids. Plurilocular sporangia not detected on erect thalli. Heteromorphic life history alternating between macroscopic polystichous sporophyte and filamentous gametophytes. Gametophytes dioecious but sexually monomorphic, anisogamous, uniseriate, branched. Unispores pear-shaped, normally biflagellated, one chloroplast with eyespot. Germination unipolar forming emptied embryospore. Micro-gametangia almost colorless, forming in cluster, each locule has an individual release pore. Micro-gametes colorless, teardrop-shaped, biflagellated with longer anterior flagellum, containing a chloroplast with stigma. Macro-gametangia ovate, in series, containing one macro-gamete in each locule. Macro-gamete pear shaped, twice as large as micro-gamete, normally biflagellated, containing 4 to 5 chloroplasts and a stigma on one chloroplast. Macrogametes develop into macroscopic sporophyte. Early developmental processes of sporophyte show similarities with the Laminariales, however, without obvious meristematic region. Although the species has been placed in the Dictyosiphonales, it shows closer systematic relationship with the Laminariales, possibly an ancestral form of the Laminariales. Gametophytes grow well in 5-10%C, but not well over 15%C, mature under 5%C short day conditions. Sporophytes grow well in 5%C and 10%C but not over 15%C, mature in 5%C. Thus the growth season of the species is controlled by the maturation of the gametophytes in winter.

Information contributed by: H. Kawai. The most recent alteration to this page was made on 2013-03-15 by Wendy Guiry.

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

Most recent taxonomic treatment adopted: Kawai, H. & Sasaki, H. (2001 '2000'). Molecular phylogeny of the brown algal genera Akkesiphycus and Halosiphon (Laminariales), resulting in the circumscription of the new families Akkesiphycaceae and Halosiphonaceae. Phycologia 39: 416-428.

Comments: Reported only from cold current area of Hokkaido, Japan. Summer annual, upper subtidal.

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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=42929

Citing AlgaeBase
Cite this record as:
Wendy Guiry in Guiry, M.D. & Guiry, G.M. 15 March 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 19 April 2024