Eisenia Areschoug, 1876

Holotype species: Eisenia arborea J.E.Areschoug

Original publication and holotype designation: Areschoug, J.E. (1876). De tribus Laminarieis (Egregia Aresch., Eisenia Aresch., Nereocystis) et de Stephanocystide osmundacea (Turn.). Trevis. observationes praecursorias offert. Botaniska Notiser 1876: 65-73.

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 is 15 in E. arborea (Hollenberg 1939) and 27-29 in E. bicyclis (Ohmori 1967). Sporophyte perennial. Six years is estimated life-span for E. bicyclis (Taniguchi & Kato 1984). Holdfast massive, with dichotomously branched haptera. Stiff, woody stipe up to ca. 1 m tall and bifurcate above, extending into 2 flattened lobes bearing many lateral blades, the sporophylls. The bifurcation is the thickened lower margin of the primary terminal, simple and undivided blade which erodes after some time leaving a small partial blade at outer extremity of each false stipe with 2 meristem regions. These give rise to the sporophylls along the lower outer margin. Sori develop on sporophylls as irregular patches. Structure of sporophyte as in Laminaria composed of photosynthetic meristoderm, parenchymatic cortex and central medulla. There is a strong seasonality of growth and reproduction in E. bicyclis. Each year up to ca. 40 sporophylls are formed and discarded lateron. Rapid growth takes place from January to August, slow growth from September to December. Although sori are present throughout the year, new sori on young blades appear from late summer onwards (Taniguchi et al. 1991).

Information contributed by: I. Bartsch. The most recent alteration to this page was made on 2021-04-23 by M.D. Guiry.

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

Most recent taxonomic treatment adopted: Kawai, H., Akita, S., Hashimoto, K. & Hanyuda, T. (2020). A multigene molecular phylogeny of Eisenia reveals evidence for a new species, Eisenia nipponica (Laminariales), from Japan. European Journal of Phycology 55(2): 234-241, 14 figs.

Comments: Photosynthetic rate of E. bicyclis plants from 2, 4 and 5 m depths is saturated at a photon fluence rate of ca. 185 µmol m-2 s-1. Depth limitation of this species is calculated to be at 1.2% of the light intensity at water surface (Maegawa et al. 1987). Population density of newly germinated plants is affected by density of adults (reduced light intensity) and temperature, with high recruitment at low temperatures (Taniguchi and Kito 1988) although gametophytes survive up to 30°C for 2 weeks (tom Dieck 1993). The genus is endemic to warm-temperate waters in the Pacific with two very similar species in Japan (E. bicyclis) and the west coast af USA from Vancouver islands to Baja California (E. arborea). Along the Peruvian coast grow E. gracilis and E. cokeri, the latter probably conspecific to E. arborea. Additionally there are deep-water species: E. desmarestioides and E. masonii at Isla Guadeloupe in Baja California and E. galapagensis in the Galapagos Archipelago. The deep-water species and young Eisenia plants are similar to the genus Ecklonia. In Japan, intergeneric and interspecific crosses were successful between the 4 species Ei. bicyclis, Ec. cava, Ec. stolonifera and Ec. kurome (Migita 1984). Genus of economic importance, especially in Japan as important food source for abalone or sea urchin aquaculture (Sanbonsuga 1984). First tissue culture experiments with E. bicyclis were successful (Notoya & Aruga 1990). In E. bicyclis a phlorotannin was identified as a substance with remarkable deodorizing action against methyl mercaptan (Kita et al 1990).

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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.

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Citing AlgaeBase
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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 23 April 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 25 June 2024

 
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