Porphyra

Porphyra is a coldwater seaweed that grows in cold, shallow seawater. More specifically, it belongs to red algae phylum of laver species (from which comes laverbread), comprising approximately 70 species.[2] It grows in the intertidal zone, typically between the upper intertidal zone and the splash zone in cold waters of temperate oceans. In East Asia, it is used to produce the sea vegetable products nori (in Japan) and gim (in Korea). There are considered to be 60 to 70 species of Porphyra worldwide[3] and seven around Britain and Ireland where it has been traditionally used to produce edible sea vegetables on the Irish Sea coast.[4] Porphyra is a chief source of plant-based vitamin B12.

For the color known in Greek as porphyra, see Tyrian purple. For some species previously in this genus have been reclassified as pyropia, see Pyropia.
Not to be confused with Porphyria.

Porphyra
Porphyra umbilicalis (right) and Porphyra purpurea (front), in Heligoland
Scientific classification
(unranked): Archaeplastida
Division: Rhodophyta
Class: Bangiophyceae
Order: Bangiales
Family: Bangiaceae
Genus: Porphyra
C.Agardh 1824
Species[1]
Synonyms[1]

Conchocelis Batters 1892
Phyllona J.Hill 1773

Life cycle

Porphyra displays a heteromorphic alternation of generations.[5] The thallus we see is the haploid generation; it can reproduce asexually by forming spores which grow to replicate the original thallus. It can also reproduce sexually. Both male and female gametes are formed on the one thallus. The female gametes while still on the thallus are fertilized by the released male gametes, which are non-motile. The fertilized, now diploid, carposporangia after mitosis produce spores (carpospores) which settle, then bore into shells, germinate and form a filamentous stage. This stage was originally thought to be a different species of alga, and was referred to as Conchocelis rosea. That Conchocelis was the diploid stage of Porphyra was discovered by the British phycologist Kathleen Mary Drew-Baker in 1949 for the European species Porphyra umbilicalis.[6] It was later shown for species from other regions as well.[2][7]

Food

Most human cultures with access to Porphyra use it as a food or somehow in the diet, making it perhaps the most domesticated of the marine algae,[8] known as laver, rong biển (Vietnamese), nori (Japanese:海苔), amanori (Japanese),[9] zakai, gim (Korean:김),[9] zǐcài (Chinese:紫菜),[9] karengo, sloke or slukos.[3] The marine red alga Porphyra has been cultivated extensively in many Asian countries as an edible seaweed used to wrap the rice and fish that compose the Japanese food sushi and the Korean food gimbap. In Japan, the annual production of Porphyra species is valued at 100 billion yen (US$1 billion).[10]

Source of Vitamin B12

One study in 2014 pointed to dried purple laver as a vegan source of biologically-active Vitamin B12. The study noted that B-12 was found in both raw and roasted seaweed, the latter containing about half as much—but still a sufficient amount. Just 4 grams of dried purple laver was considered sufficient to meet the RDA for B-12.[11] However, the Academy of Nutrition and Dietetics considers this source unreliable for vegans.[12]

Species

Following a major reassessment of the genus in 2011, many species previously included in Porphyra have been transferred to Pyropia, for example Pyropia tenera, Pyropia yezoensis and the species from New Zealand Pyropia rakiura and Pyropia virididentata, leaving only five species out of seventy still within Porphyra itself.[14]

References
  1. Guiry, Michael D. (2012). Porphyra. In: Guiry, M.D. & Guiry, G.M. (2017). AlgaeBase. World-wide electronic publication, National University of Ireland, Galway (taxonomic information republished from AlgaeBase with permission of M.D. Guiry). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=143808 on 2017-09-06
  2. Brodie, J.A. and Irvine, L.M. 2003. Seaweeds of the British Isles. Volume 1 Part 3b. The Natural History Museum, London.ISBN 1 898298 87 4
  3. Kain, J.M. 1991. Cultivation of attached seaweeds. in Guiry, M.D. and Blunden, G. 1992. Seaweed Resources in Europe: Uses and Potential. John Wiley and Sons, Chichester ISBN 0-471-92947-6
  4. Hardy, F.G. and Guiry, M.D. 2006. A Check-list and Atlas of the Seaweeds of Britain and Ireland. British Phycological Society, London. ISBN 3-906166-35-X
  5. Porphyra life cycle Archived 2007-04-11 at the Wayback Machine
  6. Drew, Kathleen M. (1949). "Conchocelis-phase in the life-history of Porphyra umbilicalis (L.) Kütz". Nature. 164 (4174): 748–749. Bibcode:1949Natur.164..748D. doi:10.1038/164748a0.
  7. Thomas, D. 2002. Seaweeds. The Natural History Museum, London. ISBN 0-565-09175-1
  8. Mumford, T.F. and Miura, A. 4.Porphyra as food: cultivation and economics. in Lembi, C.A. and Waaland, J.R. 1988. Algae and Human Affairs. Cambridge University Press, Cambridge. ISBN 0-521-32115-8
  9. Abbott, Isabella A (1989). Lembi, Carole A.; Waaland, J. Robert (eds.). Algae and human affairs (Food and food products from seaweeds). Cambridge University Press, Phycological Society of America. p. 141. ISBN 978-0-521-32115-0.
  10. Aoki, Y. and Kamei, Y. 2006 Preparation of recombinant polysaccharide-degrading enzymes from the marine bacterium, Pseudomonas sp. ND137 for the production of protoplasts of Porphyra yezoensis Eur. J. Phycol. 41: 321-328.
  11. Watanabe, Fumio; Yabuta, Yukinori; Bito, Tomohiro; Teng, Fei (2014-05-05). "Vitamin B12-Containing Plant Food Sources for Vegetarians". Nutrients. 6 (5): 1861–1873. doi:10.3390/nu6051861. ISSN 2072-6643. PMC 4042564. PMID 24803097.
  12. Melina V, Craig W, Levin S (2016). "Position of the Academy of Nutrition and Dietetics: Vegetarian Diets". J Acad Nutr Diet. 116 (12): 1970–1980. doi:10.1016/j.jand.2016.09.025. PMID 27886704. Fermented foods (such as tempeh), nori, spirulina, chlorella algae, and unfortified nutritional yeast cannot be relied upon as adequate or practical sources of B-12.39,40 Vegans must regularly consume reliable sources— meaning B-12 fortified foods or B-12 containing supplements—or they could become deficient, as shown in case studies of vegan infants, children, and adults.
  13. Morton, O. 1994. Marine Algae of Northern Ireland. Ulster Museum, Belfast. ISBN 0-900761-28-8
  14. Sutherland; et al. (October 2011). "A New Look at an Ancient Order: Generic Revision of the Bangiales (Rhodophyta)". J. Phycol. 47 (5): 1131–1151. doi:10.1111/j.1529-8817.2011.01052.x. PMID 27020195.
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