Gracilaria, also known as irish moss or ogonori, is a genus of red algae in the family Gracilariaceae. It is notable for its economic importance as an agarophyte meaning that it is used to make agar, as well as its use as a food for humans and various species of shellfish. Various species in the genus are cultivated among Asia, South America, Africa and Oceania. They produce over 90% of the world's agar.

Taxonomy

Gracilaria contains the following subtaxa:

Distribution

Gracilaria are found in warm waters throughout the world, though they also occur seasonally in temperate waters. It can not tolerate temperatures below 10 °C. Gracilaria are found in all oceans except the Arctic. Their center of diversity is the Western Pacific, where they have been traditionally cultivated as a source of agar.

Use

Gracilaria is used as a food in Filipino, Hawaiian, Japanese, Korean and Sri Lankan cuisines. In Japanese cuisine, it is called ogonori or ogo, and used to make tokoroten. In the Philippines, it is called gulaman and used to make a gelatin substitute. In Jamaica, it is known as Irish moss. In Korea, it is known as kkosiraegi. Gracilaria oligosaccharides with degree of polymerization 6 prepared by agarase digestion from agar-bearing Gracilaria sp. polysaccharides have been shown to be an effective prophylactic agent during in vitro and in vivo experiments against Japanese encephalitis viral infection. The sulfated oligosaccharides from Gracilaria sp. seem to be promising candidates for further development as antiviral agents. In the Philippines, Gracilaria have been harvested and used as food for centuries, eaten both fresh or sun-dried and turned into jellies. The earliest historical attestation is from the Vocabulario de la lengua tagala (1754) by the Jesuit priests Juan de Noceda and Pedro de Sanlucar, where golaman or gulaman was defined as "una yerva, de que se haze conserva a modo de Halea, naze en la mar" ("an herb, from which a jam-like preserve is made, grows in the sea"), with an additional entry for guinolaman to refer to food made with the jelly. In Japan, Gracilaria has been used to produce funori (府海苔), an agar-based glue, since the 17th century. In Sri Lanka, Gracilaria has been used to make a seaweed soup that also incorporates coconut cream and lime. It is also used to create seaweed jelly, a local sweetmeat in the Puttalam District of northwestern Sri Lanka. Irish moss is long been used as a clarifying agent during the brewing of beer, especially among home brewers, as an alternative to mechanical filtering.

Aquarium trade

Gracilaria commonly appears as a macroalgae for sale in the aquarium trade. It is highly palatable to tangs and many other herbivorous fish, and its nutrient uptake ability makes it a suitable choice for a refugium.

Ecology

Gracilaria are susceptible to infection by the parasitic oomycete Pythium porphyrae. Reproduction by Gracilaria gracilis is supported by Idotea balthica – the first known case of an animal helping algae reproduce.