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Macrocystis pyrifera
Scientific classification
Kingdom: Chromalveolata
Division: Heterokontophyta
Class: Phaeophyceae
Order: Laminariales
Family: Laminariaceae
Genus: Macrocystis

Macrocystis angustifolia
Macrocystis integrifolia
Macrocystis laevis
Macrocystis pyrifera

Macrocystis is a genus of kelp (algae). This genus contains the largest of all the phaeophyceae or brown algae. Macrocystis has pneumatocysts at the base of its blades. Sporophytes are perennial, and individual stipes may persist for many years. Common along the coast of the eastern Pacific Ocean, from central California to Baja California and north to southeast Alaska (Sitka).

One species, Macrocystis pyrifera, under this genus, has the fastest linear growth of any organism on earth.[1] They can grow two hundred feet long at a rate of two feet a day.



Macrocystis is a genus of kelp, some species of which are so huge that the plants may grow to up to 60m (200ft).[2]The stipes arise from a holdfast and branch three or four times from near the base. Blades develop at irregular intervals along the stipe.[3 ][4] M. pyrifera grows to over 45m (150ft) long.[4][5]

The stipes are unbranched and each blade has a gas bladder at its base.[6]

Life cycle

The sporophyte has many sporangia located in its blades, which, through meiosis, releases haploid spores, which will grow into female and male gametophytes. These gametophytes grow mitotically, and produce gametes, sperm and eggs. The gametophytes are microscopic. The female has larger and fewer cells then the male. The male releases its sperm, which find their way to the female, following a pheremone released by the female, there it fertilizes the egg, to form the zygote, which, through mitosis, begins growth.


Juvenile giant kelp grow directly on the parent female gametophyte, extending one or two primary blades, and beginning a rudimentary holdfast, which will eventually cover the gametophyte completely. Growth occurs with lengthening of the stipe, and splitting of the blades. This occurs by means of small tears where the blade meets the stipe, which splits the stipe into two. Pneumatocysts grow after the first few blade splittings.


Grows forming extensive beds, large "floating canopies", on a rocky substrate.[4]


There are four species of macrocystis.[7]

  • Macrocystis angustifolia Bory de Saint-Vincent
  • Macrocystis integrifolia Bory de Saint-Vincent, Great kelp
  • Macrocystis laevis C.H.Hay;
  • Macrocystis pyrifera (L.) C.Ag, Giant kelp, Giant bladder kelp; and M. pyrifera var. humboldtii Bomplan.


  • Macrocystis integrifolia is much smaller, the sporangial thalli growing only to 6 m long; it is found on intertidal rocks or shallow subtidal rocks.[4][9]
  • Macrocystis angustifolia Bory is found in Australia.[10]

See also


  1. ^ Fenner, Bob The Brown Algae
  2. ^ Hoek at al
  3. ^ Mondragon and Mondragon
  4. ^ a b c d e f Abbott and Hollenberg
  5. ^ Cribb
  6. ^ Kain
  7. ^ AlgaeBase: Genus: Macrocystis
  8. ^ AlgaeBase: Species: Macrocystis pyrifera
  9. ^ AlgaeBase: Species: Macrocystis integrifolia
  10. ^ Huisman


  • Abbott, I A and Hollenberg, G J (1976) Marine Algae of California. Stanford University Press, California. ISBN 0-8047-0867-3
  • Cribb, A B (1953) Macrocystis pyrifera (L.) Ag. in Tasmanian waters Australian Journal of Marine and Freshwater Research, Vol 5, issue 1.
  • Hoek, C van den; Mann, D G and Jahns, H M (1995) Algae An Introduction to Phycology. Cambridge University Press, Cambridge. ISBN 0 521 30419 9
  • Huisman, J M (2000) Marine Plants of Australia. University of Western Australia Press. ISBN 1 876268 33 6
  • Kain, J M (1991) Culivation of attached seaweeds in Guiry, M D and Blunden, G (1991) Seaweed Resources in Europe: Uses and Potential. John Wiley and Sons.
  • Mondragon, Jennifer and Mondragon, Jeff (2003) Seaweeds of the Pacific Coast. Sea Challengers, Monterey, California. ISBN 0-930118-29-4

Further reference

  • Lopez, James. "Macrocystis pyrifera." Monterey Bay Aquarium Research Institute. 2001. Monterey Bay Aquarium Research Institute. 10 Jan 2007

External links



Up to date as of January 23, 2010

From Wikispecies

Macrocystis pyrifera


Main Page
Cladus: Eukaryota
Regnum: Chromalveolata
Divisio: Heterokonta
Classis: Phaeophyceae
Ordo: Laminariales
Familia: Laminariaceae
Genus: Macrocystis
Species: M. angustifolia - M. integrifolia - M. laevis - M. pyrifera


Macrocystis C. Agardh, 1820


  • Agardh, C.A. (1820). Species algarum rite cognitae, cum synonymis, differentiis specificis et descriptionibus succinctis. Vol. 1, Part 1 pp. 1-168. Lund: Berling.
  • Guiry, M.D. & Guiry, G.M. (2009). AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. Accessed on 2009-12-19.
  • Lane, C.E.; Mayes, C.; Druehl, L.D.; & Saunders, G.W. (2006). A multi-gene molecular investigation of the kelp (Laminariales, Phaeophyceae) supports substantial taxonomic re-organization. Journal of Phycology 42:493-512.

Vernacular names

English: Giant Kelp
Wikimedia Commons For more multimedia, look at Macrocystis on Wikimedia Commons.


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