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Agarum Dumortier, 1822: 102

Classification:
Empire Eukaryota
Kingdom Chromista
Phylum Ochrophyta
Class Phaeophyceae
Order Laminariales
Family Costariaceae

Lectotype species: Agarum clathratum Dumortier

Original publication:Dumortier, B.-C. (1822). Commentationes botanicae. Observations botaniques, dédiées à la Société d'Horticulture de Tournay. pp. [i], [1]-116, [1, tabl., err.]. Tournay: Imprimerie de Ch. Casterman-Dieu, Rue de pont No. 10.
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Type designated inBoo, G.H., Lindstrom, S.C., Klochkova, N.C., Yotsukura, N., Yang, E.C., Kim, H.G., Waaland, J.R., Cho, G.Y., Miller, K.A. & Boo, S.M. (2011). Taxonomy and biogeography of Agarum and Thalassiophyllum (Laminariales, Phaeophyceae) based on sequences of nuclear, mitochondrial, and plastid markers. Taxon 60(3): 831-840.

Taxonomic status: currently recognized as a distinct genus.

Description: Life history diplohaplontic with alternation of large sporophyte bearing unilocular meiosporangia with paraphyses (sori) and microscopic dioecious and oogamous, heteromorphous gametophytes (for detail, see Laminaria). Haploid chromosome number in A. clathrathum (= A. cribrosum) is n = 22 (Yabu 1964b). Sporophyte perennial, composed of holdfast, stipe and blade. Holdfast composed of small branched haptera. Stipe comparatively small (10-30 cm), cylindrical or flattened. Undivided blades with longitudinal narrow to broad median rib and numerous perforations distinguish the genus from the other genera of Laminariaceae. The perforations in the blade may be of considerable size (up to 2 cm in diam.). Sori broad, as irregular patches on the blade surface. In A. clathratum sori develop from late winter to early spring on the newly formed blade (Kanda 1941). Structure of sporophyte as in Laminaria composed of photosynthetic meristoderm, parenchymatic cortex and central medulla. Parthenogenesis of female gametophytes and apogamy of male gametophytes may take place, in the latter process normal adult sporophytes are never formed. Aposporie on distal blade parts may produce monoecious diploid gametophytes, forming tetraploid sporophytes after fertilization (Nakahara 1984). Growth of the Arctic to cold-temperate species A. clathratum is best at 5-10%C. Gametogenesis is inhibited at > 14_and the upper lethal limit of the gametophytes is 20-21_ (Nakahara 1984; tom Dieck 1993).

Comments: The genus is distributed in cold-temperate to arctic waters of the northwestern Atlantic, on the american Pacific side from Alaska to California, in the Bering Sea, Ochotsk sea and northern Japan (Honshu, Hokkaido, Saghalien and Kuriles). It may form dense sublittoral belts. A. clathratum is a deep-water species (often dominating at 10-30 m) growing under the dense laminarian vegetation and seems to have a protection mechanism against sea urchin predation (Keats and others 1984, Vadas 1977).

NCBI Nucleotide Sequences

Numbers of names and species: There are 45 species (and infraspecific) names in the database at present, of which 6 have been flagged as currently accepted taxonomically.

Names: ('C' indicates a name that is currently accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):

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: http://www.algaebase.org/search/genus/detail/?genus_id=33349

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 20 June 2013.

Algaebase taxon LSID: urn:lsid:algaebase.org:taxname:8244

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