Undaria pinnatifida or wakame is a large brown kelp with a branched holdfast giving rise to a stipe. Just above the holdfast, the stipe has very wavy edges, giving it a corrugated appearance. The stipe gives rise to a blade that is broad, flattened and lanceolate. It has a distinct midrib. The margins of the blade are wavy. Plants can reach an overall length of one to three metres. Undaria pinnatifida is an annual species with two separate life stages.
Wakame is a laminarian kelp indigenous to the temperate regions of Japan, China and Korea (Stuart, 2003). It has been spread around the world by international shipping and mariculture. It has extended its range to include 12 countries on four continents since 1981 (Stuart, 2003). Wakame is a non-native species, which may cause displacement of native species. It was first recorded in the UK from the Hamble Estuary in the Solent on 15 June 1994 (Farell & Fletcher, 2000). It tolerates a wide salinity and temperature range. Its morphological and reproductive characteristics make it a very successful invasive species. Undaria pinnatifida possesses a heteromorphic life cycle with alternation of generations between a diploid sporophyte and a haploid gametophyte (Aguilar-Rosas et al., 2004). It may be confused with Alaria esculenta but the corrugated stipe is distinctive.
Wakame is economically important as a food crop but is also a fouling organism. It is able to compete with native kelp species in the shallow sublittoral/infralittoral zone (Farrell & Fletcher, 2000). It is also effective in providing habitats, nursery areas and protective cover for many species. It grows well in estuarine conditions unlike many of the native kelp species (Farrell & Fletcher, 2000) .
Isotype for Alaria pinnatifida Harv. Catalog Number: US 56023 Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany Verification Degree: Original publication and alleged type specimen examined Preparation: Pressed specimen Collector(s): C. Wright Year Collected: 1855 Locality: Shimoda (Simodak)., Honshu, Shizuoka, Japan, Asia-Temperate
Isotype: Harvey, W. H. 1859. Proc. Amer. Acad. Arts. 4: 329.
Wakame is an introduced species of brown seaweed in Europe found subtidally, often growing on man-made structures such as marina pontoons. In its native habitat, it occurs in dense stands, forming a thick canopy on a wide range of shores from low tide level down to 15 m in clear waters.
In 1867 the word "wakame" appeared in an English-language publication, A Japanese and English Dictionary, by James C. Hepburn.
Starting in the 1960s, the word "wakame" started to be used widely in the United States, and the product (imported in dried form from Japan) became widely available at natural food stores and Asian-American grocery stores, due to the influence of the macrobiotic movement, and in the 1970s with the growing number of Japanese restaurants and sushi bars.
New studies conducted at Hokkaido University have found that a compound in wakame known as fucoxanthin can help burn fatty tissue. Studies in mice have shown that fucoxanthin induces expression of the fat-burning protein UCP1 that accumulates in fat tissue around the internal organs. Expression of UCP1 protein was significantly increased in mice fed fucoxanthin. Wakame is also used in topical beauty treatments. See also Fucoidan.
Wakame is a rich source of eicosapentaenoic acid, an omega-3 fatty acid. At over 400 mg/100 kcal or almost 1 mg/kJ, it has one of the higher nutrient:calorie ratios for this nutrient, and among the very highest for a vegetarian source. A typical 1-2 tablespoon serving of wakame contains roughly 3.75–7.5 kcal and provides 15–30 mg of omega-3 fatty acids. Wakame also has high levels of sodium, calcium, iodine, thiamine and niacin.
In Oriental medicine it has been used for blood purification, intestinal strength, skin, hair, reproductive organs and menstrual regularity.
In Korea, the wakame soup miyeokguk is popularly consumed by women after giving birth as miyeok contains a high content of calcium and iodine, nutrients that are important for nursing new mothers. Many women consume it during the pregnancy phase as well. It is also traditionally eaten on birthdays for this reason, a reminder of the first food that the mother has eaten and passed on to her newborn through her milk, thus bringing good fortune for the rest of the year.
Japanese and Korean sea-farmers have grown wakame for centuries and they still are the main producers and eaters. Since 1983 wakame is also cultivated in France, in sea fields established near the shores of Brittany.
Goma wakame, also known as seaweed salad, is a popular side dish at American and European sushi restaurants. Literally translated, it means "sesame seaweed", as sesame seeds are usually included in the recipe.
Native to cold temperate coastal areas of Japan, Korea, and China, in recent decades it has become established in New Zealand, the United States, France, Great Britain, Spain, Italy, Argentina, and Australia. It was nominated one of the 100 worst invasive species in the world.
In New Zealand, wakame is declared as an unwanted organism. It was first discovered in Wellington Harbour in 1987 and probably arrived accidentally in the late 1980s, via shipping from Asia contained in ballast water.
Wakame is now found around much of south-eastern New Zealand, and as far north as Auckland. It spreads in two ways: naturally, through the millions of microscopic spores released by each fertile organism, and through attachment to vessel hulls and marine farming equipment. It is a highly successful and fertile species, which makes it a serious invader. However, its impacts are not well understood and are likely to vary, depending on the location.
Even though it is an invasive species in 2012 the government allowed for the farming of wakame in Wellington, Marlborough and Banks Peninsula.
The sea plant has been found in several harbors in southern California. In May 2009 it was discovered in San Francisco Bay and aggressive efforts are underway to remove it before it spreads.
^Maeda, H.; Hosokawa, M.; Sashima, T.; Funayama, K.; Miyashita, K. (2005). "Fucoxanthin from edible seaweed, Undaria pinnatifida, shows antiobesity effect through UCP1 expression in white adipose tissues". Biochemical and Biophysical Research Communications 332 (2): 392–397. doi:10.1016/j.bbrc.2005.05.002. PMID15896707.edit
^Torres, A. R. I.; Gil, M. N. N.; Esteves, J. L. (2004). "Nutrient uptake rates by the alien alga Undaria pinnatifida (Phaeophyta) (Nuevo Gulf, Patagonia, Argentina) when exposed to diluted sewage effluent". Hydrobiologia 520: 1. doi:10.1023/B:HYDR.0000027686.63170.6c.edit