Durvillaea antarctica

Durvillaea antarctica, also known as cochayuyo and rimurapa, is a large, robust species of southern bull kelp found on the coasts of Chile, southern New Zealand, and Macquarie Island. 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. The species was first described in 1822, as Fucus antarcticus, and revised in 1892 as Durvillaea antarctica. The genus name Durvillaea was given in memory of the French explorer Jules Dumont d'Urville, while the Latin derived epithet refers to antarctic. In 2012, a taxonomic revision led to the recognition of a new species, Durvillaea poha, based on genetic, morphological and ecological evidence, which was previously recognised as the 'cape' lineage of Durvillaea antarctica. 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. 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. Further diversity, with additional unclassified lineages have been identified within the species. The blades of Durvillaea antarctica are green to golden brown with a leathery texture. The honeycomb structure of the blade gives strength and buoyancy. 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.