Macrocystis C., 1820
Holotype species: Macrocystis pyrifera (Linnaeus) C.Agardh
Original publication:Agardh, C.A. (1820 '1821'). Species algarum rite cognitae, cum synonymis, differentiis specificis et descriptionibus succinctis. Volumen primum. Pars prima. pp. [i-iv], -168. Lundae [Lund]: ex officina Berlingiana.
Type designated in Bachelot de la Pylaie, A.J.M. (1830 '1829'). Flora de l'Ile Terre-Neuve et des Iles Saint Pierre et Miclon. Livraison [Algae]. pp. 1-128. Paris: Typographie de A. Firmin Didot, rue Jacob, No. 24.
Taxonomic status: currently recognized as a distinct genus.
Most recent taxonomic treatment adopted: Demes, K.W, Graham, M.H. & Suskiewicz, T.S. (2009). Phenotypic plasticity reconciles incongruous molecular and morphological taxonomies: the giant kelp, Macrocystis (Laminariales, Phaeophyceae), is a monospecific genus (note). Journal of Phycology 45(6): 1266-1269.
Arthrothamnaceae (Jackson et al., 2017). - (2 May 2017) - Wendy Guiry
Description: Thallus to 45 m long, perennial, typically 4-8 years. Holdfast conical and consisting of a few central erect stipes bearing terete branching haptera; or holdfast prostrate, subligulate, branched, creeping with short haptera along lateral margins. Stipes numerous, erect, terete, dichotomously branching 2-6 times near base. Each stipe branch subtends a frond, which is composed of a stipe with attached blades and an apical meristematic blade. Apical blade falcate, with several young lateral blades produced unilaterally by splitting through transition region. Blades numerous on each stipe, arranged at regular intervals with a short stipe and a pyriform to subglobose pneumatocyst subtending an undivided lamina, which is narrow to broad with tapering ends, smooth to rugose, and with denticulate margins. Spores produced in unilocular sporangia with paraphyses on sporophylls borne on stipe near holdfast, with sporangia covering most of both surfaces. Sporophylls divide several times dichotomously, with or without pneumatocyst. Gametophytes dimorphic, dioecious, oogamous, branched uniseriate filaments.
Information contributed by: R.J. Lewis & M.D. Guiry. The most recent alteration to this page was made on 2 Mar 2016 by M.D. Guiry.
Comments: A single Macrocystis species occurs in both the Northern and Southern Hemispheres, being found along the Pacific coast of North America in the north and having a cicumsubantarctic distribution in the south. Many species were described based on morphological differences, later reduced to species based mainly on holdfast morphology.
Macrocystis experience a wide variety of environmental conditions because of their perennial nature, their growth habit reaching from deeper water to the surface, and the wide geographic distribution of the single species.
The physiology of Macrocystis has been widely studied in these various situations, particularly in Northern Hemisphere populations, including studies of photosynthesis and nutrient uptake kinetics. Light and nutrient requirements for recruitment of young Macrocystis plants have been determined for M. pyrifera in southern California. These data have been used to model the growth of M. pyrifera individuals and populations in response to these complex factors. Ecotypic differentiation of nitrogen physiology has been found between populations of M. pyrifera from different localities of California.
Macrocystis is of both economic and ecological importance. Between 100,000 and 170,000 wet tons of Macrocystis were harvested annually in California for alginate extraction and abalone feed, but this alginate production has now ceased, although a small amount is still harvested for abalone. Sustainable harvesting is important as the organisms that thrive in Macrocystis forest communities are of great value aesthetically, supporting both commercial fishing operations and recreational activities, particularly SCUBA, and an important habitat for the resurgent Sea Otter.
Numbers of names and species: There are 15 species names in the database at present, of which 1 has been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..
Names: ('C' indicates a name that is 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):
Click here to also show infraspecific names in the list below.
Jackson, C., Salomaki, E.D., Lane, C.E. & Saunders, G.W. (2017). Kelp transcriptomes provide robust support for interfamilial relationships and revision of the little jnown Arthrothamnaceae (Laminariales) (Letter). Journal of Phycology 53(1): 1-6.
Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.
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.
Created: 28 December 2000 by M.D. Guiry
Verified by: 02 March 2016 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=35715
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 20 November 2018.