Sunday 25 May 2014

A Phytomyxean parasite forming galls on Bull Kelp on the coast of Chile.

Bull Kelp, Durvillaea antarctica, is a large Brown Algae forming dense colonies of fronds up to 8 m long on otherwise exposed rocky shores on the coasts of South America, New Zealand and the islands of the Subantarctic. It provides protection against coastal erosion in high energy environments, as well as creating a stable environment with its own ecosystem, which is colonised by a wide variety of marine organisms. It is also considered to be economically significant, being harvested as a foodstuff in Chile, as well as for use in the cosmetic and pharmaceutical industries.

Bull Kelp, Durvillaea antarctica, on Macqaurie Island in the Southern Ocean. Steve Smith/Australian Antarctic Division.

In a paper published in the journal PLoS One on 17 September 2012, Franz Goecke and Jutta Wiese of the Kieler Wirkstoff-Zentrum at the Helmholtz Centre for Ocean Research, Alejandra Núñez of the Facultad de Ecología y Recursos Naturales at the Universidad Nacional Andrés Bello, Antje Labes and Johannes Imhoff, also of the Kieler Wirkstoff-Zentrum at the Helmholtz Centre for Ocean Research, and Sigrid Neuhauser of the Institute of Microbiology at the University of Innsbruck describe the occurrence of a gall-forming infection in Bull Kelp on the coast of central Chile in the summer of 2011.

Galls are tumour-like growth on Plants or Algae, typically caused by parasitic or pathogenic infections. In marine Algae they can be caused by Viruses, Bacteria, Fungi, Microalgae (single celled organisms which photosynthesize, but which also often have other survival strategies, such as entering the tissues of other organisms in parasitic or symbiotic relationships, or even hunting and consuming prey), Nematodes, Copepods or occasionally by exposure to industrial pollutants. Such infections are particularly dangerous to Kelps, as they typically occupy high-energy environments, and infections which modify their physical structure can significantly weaken them.

Galls on the Bull Kelp, Durvillaea antarctica, on the coast of central Chile. Scale bar is 1 cm. Goecke et al. (2012).

Examination of the galls on Bull Kelp on the Chilean coast revealed that they were caused by a Phytomyxean parasite. The Phytomyxea are a group of little-understood eukaryotic single celled organisms with complex lifestyles that often involve free-living stages and more than one host organism. They are split into two subgroups, the Plasmodiophorida, which are parasites of Green Plants and which have form resting spores (tough, inactive spores which can survive long periods of harsh conditions, such as cold winters or summer droughts), and the Phagomyxida, which infect Diatoms and Brown Macro-Algae (Kelps and Wracks), and which do not.

Genetic analysis of the new Kelp-infecting Phytomyxean parasite revealed it to be a member of the Phagomyxida, apparently closely related to the previously described Maullinia ectocarpii, which is known to infect a number of Brown Algae on the Chilean coast. Since the degree of genetic variability within Phytomyxean species is not known, and the organisms often display complex lifestyles that produce unfamiliar forms in response to novel conditions, Goecke et al. simply refer to it as Maullinia sp.

Maullinia sp. from the Chilean Bull Kelp clearly forms resting spores, a behaviour previously unseen in any member of the Phagomyxida. Given the poorly understood nature of the group Goecke et al. question whether the forming of resting spores might in fact be found across this group, rather than being a novel innovation in this species.

(e) Resting spores of Maullinia sp. (Light microscopy, DIC). The resting spores are smooth, thick walled, and roundish but slightly irregular in shape. Bar 10 μm. (f) SEM microphotograph of the smooth walled resting spores of Maullinia sp. infecting Durvillaea antarctica samples from central Chile. Bar 2 μm. Goecke et al. (2012).

See also…

Golden Algae (Chrysophyceae) are photosynthetic eukaryotic microbes (i.e. single celled organisms that posses cell nuclei similar to those found in the cells of animals and plants, but unlike bacteria which do not), found throughout the world, predominantly in fresh water. The group is mostly poorly studied, with the exception of a few species which are toxic to Fish.

Marine organisms with calcium carbonate skeletons are known to...

Diatoms are single celled algae related to Kelp and Water Moulds. They are encased in silica shells with two valves. During reproduction the cells divide in two, each of which retains one valve...

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