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{{Taxobox | color = #FA7B62
| name = Bladder wrack
| image_width = 250px
| image = Fucus vesiculosus Wales.jpg
| regnum = [[Chromalveolata]]
| phylum = [[Heterokont]]ophyta
| classis = [[Brown alga|Phaeophyceae]]
| ordo = [[Fucales]]
| familia = [[Fucaceae]]
| genus = ''[[Fucus]]''
| species = '''''F. vesiculosus'''''
| binomial = ''Fucus vesiculosus''
| binomial_authority = [[Carolus Linnaeus|L.]]
}}

'''Bladder wrack''', '''''Fucus vesiculosus''''', is a [[seaweed]] found on the coasts of the [[North Sea]], the western [[Baltic Sea]], and the [[Atlantic Ocean|Atlantic]] and [[Pacific Ocean]]s, also known by the common names ''black tang'', ''rockweed'', ''bladder Fucus'', ''sea oak'', ''black tany'', ''cut weed'' and ''rock wrack''. It was the original source of [[iodine]], discovered in [[1811]], and was used extensively to treat [[goitre]], a swelling of the [[thyroid gland]] related to [[iodine deficiency]]. In the 1860s, it was claimed that bladder wrack, as a thyroid [[stimulant]], could counter [[obesity]] by increasing the [[metabolic rate]] and, since then, it has been featured in numerous [[weight loss|weight-loss]] remedies.

==Distribution==
The species is common especially on sheltered shores from the middle littoral to lower intertidal levels <ref name="Taylor 57">{{cite book |author=W. R. Taylor |year=1957 |title=Marine Algae of the Northeastern Coast of North America |publisher=[[University of Michigan]], Ann Arbor |id=ISBN 0-472-04904-6}}</ref>. It is rare on exposed shores where any specimens may be short, stunted and without the air vesicles <ref>{{cite book |author=C. S. Lobban & P. J. Harrison |year=1994 |title=Seaweed Ecology and Physiology |publisher=[[Cambridge University Press]], Cambridge |id=ISBN 0-521-40897-0}}</ref>.

''Fucus vesiculosus'' is one of the most common algae on the shores of the [[British Isles]] <ref>{{cite book |author=F. G. Hardy & M. D. Guiry |year=2003 |title=A Check-list and Atlas of the Seaweeds of Britain and Ireland |publisher=[[British Phycological Society]], London |id=ISBN 0-9527115-1-6 |url=http://seaweed.ucg.ie/check-list/check-list.pdf}}</ref>. It is recorded from the Atlantic shores of Europe, the [[Baltic Sea]], [[Greenland]], [[Azores]], [[Canary Islands]] and [[Madeira]] <ref>{{cite web |url=http://www.algaebase.org/speciesdetail.lasso?species_id=87&sk=0&from=results |title=''Fucus vesiculosus'' Linnaeus |work=[[AlgaeBase]] |date=[[2007-01-12]] |author=M. D. Guiry & Wendy Guiry}}</ref>. On the Atlantic coast of [[North America]] from [[Ellesmere Island]], [[Hudson Bay]] to [[North Carolina]] <ref name="Taylor 57"/>.

==Description==
''Fucus vesiculosus'' is a very variable alga. It can grow to 100 [[centimetre|cm]] or more and is easily recognised by the small gas–filled vesicles which occur in pairs on either side of a central midrib running along the centre of the strap-like frond. ''[[Ascophyllum nodosum]]'' also has air vesicles, but rather than being paired, they are arranged in series along a frond which is not flattened and without a midrib. Both are common species on most shores of the [[British Isles]].

The large brown algae have similar life cycles. At maturity the reproductive bodies form in conceptacles sunken in receptacles produced towards the tips on the branches. In these conceptacles [[oogonium|oogonia]] and [[antheridium|antheridia]] are produced and after [[meiosis]] they are released. After [[fertilisation]], the [[zygote]] develops, settles and grows to form the [[diploid]] [[sporophyte]] plant.

The large vegetative phase is diploid and [[gametophyte|gametophytic]]. Meiosis occurs during the formation of the [[gamete]]s. The [[egg (biology)|egg cells]] are formed on the female plants in [[conceptacle]]s embedded in receptacles. The spermatozoids and egg cells are extruded from the conceptacles. Once fertilised, the zygote settles and grows to form the new diploid gametophyte <ref>{{cite book |author=C. van den Hoek, D. G. Mann & H. M. Jhans |year=1995 |title=Algae An Introduction to Phycology |publisher=[[Cambridge University Press]], Cambridge |id=ISBN 0-521-30419-9}}</ref>.

==Consumption==
[[Image:Fucus_vesiculosus_closeup.jpg|thumb|Close-up of bladder wrack's eponymous vesicles]]
A common food in [[Japan]], bladder wrack is used as an additive and flavouring in various food products in [[Europe]]. Bladder wrack is commonly found as a component of kelp tablets or powders used as [[nutritional supplement]]s. It is sometimes loosely called "[[kelp]]", but that term technically refers to a different seaweed.

Primary chemical constituents of this plant include [[mucilage]], [[algin]], [[mannitol]], [[beta-carotene]], [[zeaxanthin]], [[iodine]], [[bromine]], [[potassium]], volatile oils, and many other [[mineral]]s. The main use of bladder wrack (and other types of seaweed) in [[herbal medicine]] is as a source of iodine, an essential nutrient for the thyroid gland. Bladder wrack has proved most useful in the treatment of underactive thyroid glands (hypothyroidism) and goitre (citation needed). Through the regulation of thyroid function, there is an improvement in all the associated symptoms. Where obesity is associated with thyroid trouble, this herb may be very helpful in reducing the excess weight (citation needed). It has a reputation in helping the relief of [[rheumatism]] and [[rheumatoid arthritis]], both used internally and as an external application upon inflamed joints (citation needed). A chemical constituent of bladder wrack called [[alginic acid]] swells upon contact with water; when taken orally, it forms a type of "seal" at the top of the stomach, and for this reason is used in several over-the-counter preparations for [[heartburn]] (citation needed). The same constituent gives bladder wrack [[laxative]] properties as well (citation needed). Other proposed uses of bladder wrack include treating [[atherosclerosis]] and strengthening [[immunity (medical)|immunity]], although there is no scientific evidence at present that it works for these purposes.

Bladder wrack should not be used in cases of [[hyperthyroidism]] or cardiac problems, or during [[pregnancy]] and [[lactation]]. Excessive dosage (many times the recommended dosage) may lead to hyperthyroidism, [[tremor]], increased [[pulse rate]] and elevated [[blood pressure]].

==References==
<div class="references-small"><references/></div>

==External links==
*{{cite web |url=http://weedseen.co.uk/ShowSpecies.asp?id=ZR6760 |work=British Isles Seaweed Images |title=''Fucus vesiculosus'' Linneaus Le Jolis |accessdate=2007-07-01 |author=F. Bunker}}

[[Category:Brown algae]]
[[Category:Sea vegetables]]

Bladderwrack - Revision history

MediaWiki default at 06:50, 26 September 2007