Monostroma is a genus of marine green algae (seaweed) in the family Monostromataceae.See the NCBI webpage on Monostroma. Data extracted from the As the name suggests, algae of this genus are monostromatic (single cell layered). Monostroma kuroshiense, an algae of this genus, is commercially cultivated in East Asia and South America for the edible product "hitoegusa-nori" or "hirohano-hitoegusa nori", popular sushi wraps. Monostroma oligosaccharides with degree of polymerization 6 prepared by agarase digestion from Monostroma nitidum polysaccharides have been shown to be an effective prophylactic agent during in vitro and in vivo tests against Japanese encephalitis viral infection. The sulfated oligosaccharides from Monostroma seem to be promising candidates for further development as antiviral agents. The genus Monostroma is the most widely cultivated genus among green seaweeds.
Classification Species-level classification within this genus is quite problematic and no consensus exists among algal taxonomists. This genus is oftentimes referred as "Gayralia", however Gayralia and Monostroma are congeneric. A number of monostromatic algal species have been removed from this genus, including Kornmannia, Ulvopsis and Capsosiphon. Currently accepted working-classification of monostromatic green algaeBast, F. 2011. Monostroma: the Jeweled Seaweed for Future. LAP LAMBERT Academic Publishing GmbH & Co. KG, 66121 Saarbrücken, Germany: is provided as a figure. A taxonomic field-identification dichotomous key for this genus is available Bast, F. 2012. Systematics and Taxonomic Keys for the Marine Green Algal Family Monostromataceae. In D. M. Krueger, H (Ed.), Algae: Ecology, Economic Uses and Environmental Impact (pp. 105-120).Nova Publishers New York. 105-120
Genetics Largest phylogeographic assessment of this genus yet conducted in SW Japan revealed existence of sympatric speciation in a panmictic population; the first report of sympatric speciation in algaeBAST, F., KUBOTA, S. AND OKUDA, K. 2014. Phylogeographic Assessment of Panmictic Monostroma Species from Kuroshio Coast, Japan Reveals Sympatric Speciation. Journal of Applied Phycology. DOI:10.1007/s10811-014-0452-x
Ecophysiology, cultivation and life cycle A number of peer-reviewed scientific literature exists on the ecophysiology of this algal genus.Bast, F. 2011. Monostroma: the Jeweled Seaweed for Future. LAP LAMBERT Academic Publishing GmbH & Co. KG, 66121 Saarbrücken, Germany: Natural and cultivated sexually reproducing environmental samples, as well as sexually reproducing and serendipitously discovered asexually reproducing ecotypes of monostromatic green alga from Tosa Bay, Japan are conspecific (belong to the same species).Bast, F., Shimada, S., Hiraoka, M., & Okuda, K. 2009. Asexual life history by biflagellate zoids in Monostroma latissimum (Ulotrichales). Aquatic Botany, 91: 213-218. Patterns of seasonal fluctuations in its thallus lengths were habitat specific and recur annually.Bast, F., Shimada, S., Hiraoka, M., & Okuda, K. 2009. Seasonality and thallus ontogeny of edible seaweed Monostroma latissimum (Kützing) Wittrock (Chlorophyta, Monostromataceae) from Tosa Bay, Kochi, Japan. Hydrobiologia, 630: 161-167. Both appearance and decay of thalli were earlier at high saline habitats, suggesting that salinity positively influences either maturation of sporophytes or senescence of gametophytes. Results from life cycle, thallus ontogeny, gametangial ontogeny and phylogenetic analyses suggest that this algal genus is evolutionarily affiliated in the order Ulotrichales.Bast, F. (2010). Comparative Ecophysiology and Phylogeography of Monostroma in Southern Japan. Ph.D., Kochi University, Japan. Type of life cycle is not a valid diagnostic character for the species circumscription in MonostromataceaeBast, F. 2011. Monostroma: the Jeweled Seaweed for Future. LAP LAMBERT Academic Publishing GmbH & Co. KG, 66121 Saarbrücken, Germany:
Reproduction and sex-ratio Gametogenesis in this alga occurs in discontinuous patches along the frontal apex and the gametes release synchronously in a posterior faced linear fashion by the dehiscence of gametangial sheath, leading to the thallic disintegration.Bast, F., & Okuda, K. 2010. Gametangial Ontogeny in Intertidal Green Alga: Monostroma latissimum (Kützing) Wittrock. International Journal of Plant Reproductive Biology, 2: 11-15. The overall primary sex ratio of this alga is about 1:1 which is likely to reflect Fisherian selection.Bast, F., Hiraoka, M., & Okuda, K. 2009. Spatiotemporal Sex Ratios of a Dioecious Marine Green Alga: Monostroma latissimum (Kützing) Wittrock. International Journal on Algae., 11: 141-150.
Culinary use
In Korea, edible Monostroma species such as Monostroma nitidum are called parae (), and eaten as a namul vegetable.
In Japan, dried Monostroma kuroshiense called aonori is used to season dishes such as takoyaki and okonomiyaki. In Okinawa, it is used in a soup called āsa nu ushiru.
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