Macrocystis

Taxobox
name = "Macrocystis"

---

image_width = 200px
image_caption = "Macrocystis pyrifera"
domain = Eukaryota
regnum = Chromalveolata
phylum = Heterokontophyta
classis = Phaeophyceae
ordo = Laminariales
familia = Lessoniaceae
genus = "Macrocystis"
subdivision_ranks = Species
subdivision = "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. [Fenner, Bob [http://www.wetwebmedia.com/brnalgae.htm "The Brown Algae"] ] They can grow two hundred feet long at a rate of two feet a day.

Description

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

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

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.

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.

Ecology

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

pecies

There are four species of "macrocystis". [AlgaeBase: [http://www.algaebase.org/search/genus/detail/?genus_id=35715 Genus: Macrocystis] ]

* "Macrocystis angustifolia" Bory de Saint-Vincent

* "Macrocystis integrifolia" Bory de Saint-Vincent

* "Macrocystis laevis" C.H.Hay;

* "Macrocystis pyrifera" (L.) C.Ag; and "M. pyrifera" var. "humboldtii" Bomplan.

Distribution

* "Macrocystis pyrifera", known as giant kelp, is found in North America (Alaska to California), South America, South Africa, New Zealand, and southern Australia. [AlgaeBase: [http://www.algaebase.org/search/species/detail/?species_id=4427 Species: Macrocystis pyrifera] ] It can grow over 45 metres long and can do so in one growing season, making it the organism with the world's fastest linear growth.
* "Macrocystis integrifolia", a smaller, intertidal species, is found on the Pacific coast of America (British Columbia to California) and South America.

* "Macrocystis integrifolia" is much smaller, the sporangial thalli growing only to 6 m long; it is found on intertidal rocks or shallow subtidal rocks. [AlgaeBase: [http://www.algaebase.org/search/species/detail/?species_id=4882&sk=0&from=results Species: Macrocystis integrifolia] ]

* "Macrocystis angustifolia" Bory is found in Australia.Huisman]

ee also

* Kelp forest

Notes

References

* 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) [http://www.publish.csiro.au/?act=view_file&file_id=MF9540001.pdf "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) " [http://books.google.co.uk/books?id=xuUoiFesSHMC&printsec=frontcover 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

* [http://www.mbari.org/staff/conn/botany/browns/james/default.htm "Macrocystis pyrifa"]
* [http://ucjeps.berkeley.edu/guide/brown61.html "Macrocystis integrifolia"]
* Bushing, William W (2000) [http://www.starthrower.org/research/kelpmisc/kelp_mp.htm "Giant Bladder Kelp "] . Retrieved 21 September, 2008.