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Durvillaea antarctica
''Durvillaea antarctica'', commonly known as cochayuyo, is a large, robust bull kelp species and the dominant seaweed in southern New Zealand and Chile. ''D. antarctica'' has a circumpolar distribution between the latitudes of 29°S (in Chile) and 55°S (on Macquarie Island).〔 It is found on exposed shores, especially in the northern parts of its range, and attaches itself with a strong holdfast. ''D. antarctica'', an alga, does not have air bladders, but floats due to a unique honeycomb structure within the alga's blades, which also helps the kelp avoid being damaged by the strong waves.
==Morphology==
The blades of ''Durvillaea antarctica'' are green to golden brown with a leathery texture. The honeycomb structure of the blade gives strength and buoyancy.〔Maggy Wassilieff. (Seaweed - Bull kelp’s honeycombed structure ), ''Te Ara - the Encyclopedia of New Zealand'', Ministry of Culture and Heritage. Updated 2 March 2009. Retrieved 9 March 2010.〕 This novel structure is thought to be responsible for the wide distribution of this genus, as the kelp is able to float when its holdfast fails. It can colonise other coastlines in this manner, and has been shown to carry communities of invertebrates across vast ocean distances from one shore to another.〔Fraser CI, Nikula R & Waters JM (2011) Oceanic rafting of a coastal community. ''Proceedings of the Royal Society, B'', 278:649-655.〕 It is thought that this 'rafting' with ''Durvillaea antarctica'' and other floating seaweeds allowed a wide range of species to recolonise sub-Antarctic shores scoured clean by ice during the last Ice Age.〔Fraser CI, Nikula R, Spencer HG & Waters JM (2009) Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum. ''Proceedings of the National Academy of Sciences, USA'', 106:3249-3253.〕
The holdfast of ''D. antarctica'' is large and is very difficult to remove. ''D. antarctica'' has to resist forces equivalent to 1100 km/h on land. The holdfast failing is usually the result of worms and molluscs which feed on the tissue because of the sheltered habitat it creates. It is also common for its host rock to be broken off without the holdfast losing its grip, with this contributing significantly to erosion in some areas.〔Smith, J.M.B. and Bayliss-Smith, T.P. (1998). Kelp-plucking: coastal erosion facilitated by bull-kelp ''Durvillaea antarctica'' at subantarctic Macquarie Island, ''Antarctic Science'' 10 (4), 431–438. .〕 Recruitment rates of this species is very low, therefore the ecological impact of harvesting this species is too great.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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