Durvillaea antarctica, also known as bull kelp,[1]cochayuyo and rimurapa,[2] is a large, robust species of southern bull kelp found on the coasts of Chile, southern New Zealand, and Macquarie Island.[3][4][5][6]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.[7][8]
The blades of Durvillaea antarctica are green to golden brown with a leathery texture. The honeycomb structure of the blade gives strength and buoyancy.[7][8] 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.[9] Specimens of D. antarctica have been found to float for up to 210 days, during which time high wind speeds transport kelp rafts up to 10,000km.[10] Environmental factors such as temperature, solar radiation and surface winds (all of which vary with latitude) affect buoyancy of rafts and their rate of travel.[10] Rafts of D. antarctica are more likely to disperse offshore if plants detach during outgoing tides during autumn and winter.[11] 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.[12]
The holdfast of D. antarctica is large and is very difficult to remove. D. antarctica has to resist forces equivalent to 1100km/h on land.[13][clarification needed] The holdfast failing is usually the result of worms and molluscs which feed on the tissue because of the sheltered habitat it creates.[14] 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.[3] Recruitment rates of this species is very low, therefore the ecological impact of harvesting this species is too great.[14]
Morphology of D. antarctica
Cross-section revealing the honeycomb structure of blades
The species was first described in 1822,[15] as Fucus antarcticus, and revised in 1892 as Durvillaea antarctica.[16]
In 2012, a taxonomic revision led to the recognition of a new species, Durvillaea poha, based on genetic, morphological and ecological evidence,[4] which was previously recognised as the 'cape' lineage of Durvillaea antarctica.[4][17][18]D. poha is the only other species in the genus to share the honeycombed structure and buoyancy of D. antarctica.D. poha occurs only in southern New Zealand and on subantarctic islands (including Snares and Auckland Islands), whereas D. antarctica has a wider distribution, and is found around New Zealand, Chile and other subantarctic islands. In southern New Zealand, D. poha and D. antarctica can be found growing together, although D. poha normally grows higher up or further back on the rock platforms, or in more sheltered bays, where wave force is weaker. D. poha generally has wider fronds than D. antarctica, and can appear more 'orange' across the frond area.[4][6] Mitochondrial introgression has been observed between the two species, where some plants in Wellington exhibited the nuclear DNA of D. poha but also mitochondrial DNA belonging to D. antarctica.[19]
Further diversity, with additional unclassified lineages have been identified within the species.[6][18]
Cladogram of Durvillaea showing diversity within D. antarctica[6]
The genus name Durvillaea was given in memory of the French explorer Jules Dumont d'Urville, while the Latin derived epithet refers to antarctic, due to the species' distribution in the southern oceans.[20][1]
The Māori language name rimurapa is based on a common Polynesian word for seaweed-like living things, rimu, and is likely the basis for the Māori language name for pasta (parāoa rimurapa).[1] The common English language name bull kelp is unknown, but likely relates to the whip-like shape or the leathery texture of the species.[1]
Life cycle
Durvillaea antarctica reproduces sexually by producing egg and sperm that are released into the water. Eggs and sperm are produced on specific sites of the frond. A large individual can produce 100 million eggs in twelve hours.[14] The season when reproduction occurs varies with location, but is generally during winter months.[21] Eggs are small and disperse over short distances, and they generally require calm or moderate wave action in order to settle and successfully attach to substrates.[22]
Plants of D. antarctica can detach from substrates, particularly during storms. The kelp floats as a raft and can travel vast distances at sea, driven by ocean currents. Kelp-associated invertebrates can be transported inside of drifting holdfasts, potentially leading to long-distance dispersal and a significant impact upon the population genetic structure of those species.[24][25][26][27]
Fronds of D. antarctica can be infected by an endophytic, phaeophycean algal parasite Herpodiscus durvillaeae(Lindauer) G. R. South.[30][31] Fronds can also be infected Maullinia, a genus of intracellular, protistan parasites.[32][33][34] Based on genetic evidence, both H. durvillaeae and Maullinia have likely been dispersed across the Southern Hemisphere via rafting bull kelp.[31][32][34][35]
Durvillaea antarctica has a circumpolar distribution between the latitudes of 29°S and 55°S, found in Chile, southern New Zealand, and Macquarie Island.[3][4][5][6][36][37][38] The type locality is Cape Horn, Chile.[7][21]
It is found on exposed shores, especially in the northern parts of its range, and attaches itself with a strong holdfast.[3][4]
Human use
A pōhā covered with tōtara bark and inserted into a flax basket
Chilean culture
Use in cuisine
Stems and holdfasts of D. antarctica and D. incurvata are harvested from the coast of Chile and is used in Chilean cuisine for various recipes, including salads and stews.[6] In Quechua the species is called: cochayuyo (cocha: lake, and yuyo: weed), and hulte.[6] The Mapuche indigenous people refer to it as collofe or kollof.[6][39]
Expression
The expression remojar el cochayuyo (literally: to soak the cochayuyo) is used in Chilean Spanish to refer to sexual intercourse.[40] The expression derives from the fact that harvested D. antarctica is preserved by being sun-dried and then softened by soaking in a dish of water.
Cochayuyo cuisine
Cochayuyo salad
Māori and Moriori culture
Known as rimurapa in Māori,[2][41][42] the plant is associated with the entrance to the underworld in many traditional stories.[1] Blades of D. antarctica, along with D. poha, are used to make traditional pōhā bags, which are used to carry and store food and fresh water, to propagate live shellfish, and to make clothing and equipment for sports.[41][42][43] Pōhā are especially associated with Ngāi Tahu and are often used to carry and store muttonbird (tītī) chicks.[41][42]
D. antarctica was also used to create semi-submerged dingies called waka kōrari by Moriori of the Chatham Islands and Ngāi Tahu of the South Island, and it is a traditional Māori food source.[1]
1 2 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.
↑ Fraser CI, Nikula R & Waters JM (2011) Oceanic rafting of a coastal community. Proceedings of the Royal Society, B, 278:649-655.
1 2 Tala, Fadia; López, Boris A.; Velásquez, Marcel; Jeldres, Ricardo; Macaya, Erasmo C.; Mansilla, Andrés; Ojeda, Jaime; Thiel, Martin (2019). "Long-term persistence of the floating bull kelp Durvillaea antarctica from the South-East Pacific: Potential contribution to local and transoceanic connectivity". Marine Environmental Research. 149: 67–79. Bibcode:2019MarER.149...67T. doi:10.1016/j.marenvres.2019.05.013. PMID31154063. S2CID173993590.
↑ Hawes, Nicola A.; Taylor, David I.; Schiel, David R. (2019). "Transport of drifting fucoid algae: Nearshore transport and potential for long distance dispersal". Journal of Experimental Marine Biology and Ecology. 490: 634–41. doi:10.1016/j.jembe.2017.02.001.
↑ 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.
↑ Hurd, C (2003). The Living Reef. Nelson, New Zealand: Craig Potton Publishing.
1 2 3 Bradstock, M (1989). Between the Tides. New Zealand: David Bateman Limited.
↑ Choris, L. (1822). Voyage pittoresque autour du monde. Part I. pp. vi + 17, 12 plates. Paris
↑ Hariot, P. (1892). Complément à la flore algologique de la Terre de Feu. Notarisia 7: 1427-1435.
↑ Fraser, Ceridwen I.; Hay, Cameron H.; Spencer, Hamish G.; Waters, Jonathan M. (2009). "Genetic and morphological analyses of the southern bull kelp Durvillaea antarctica (Phaeophyceae: Durvillaeales) in New Zealand reveal cryptic species". Journal of Phycology. 45 (2): 436–443. Bibcode:2009JPcgy..45..436F. doi:10.1111/j.1529-8817.2009.00658.x. PMID27033822. S2CID18309093.
1 2 Fraser, C.I.; Winter, D.J.; Spencer, H.G.; Waters, J.M. (2010). "Multigene phylogeny of the southern bull-kelp genus Durvillaea (Phaeophyceae: Fucales)". Molecular Phylogenetics and Evolution. 57 (3): 1301–11. Bibcode:2010MolPE..57.1301F. doi:10.1016/j.ympev.2010.10.011. PMID20971197.
1 2 Fraser, Ceridwen I.; Waters, Jonathan M. (2013). "Algal parasite Herpodiscus durvillaea (Phaeophyceae: Sphacelariales) inferred to have traversed the Pacific Ocean with its buoyant host". Journal of Phycology. 49 (1): 202–206. Bibcode:2013JPcgy..49..202F. doi:10.1111/jpy.12017. PMID27008401. S2CID21397549.
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