Diseases, pathogens and parasites of Undaria pinnatifida
Diseases, pathogens and parasites of Undaria pinnatifida
Diseases, pathogens and parasites of Undaria pinnatifida
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Taxa belonging to the Bigyra, including species <strong>of</strong> Olpidiopsis, Eurychasmidium, Petersenia,<br />
Pontisma have been described from a number <strong>of</strong> hosts (e.g. Sparrow 1934, 1936; Aleem<br />
1950b, c, 1952b; Feldmann & Feldmann 1967; Whittick & South 1972; van der Meer &<br />
Pueschel 1985; Molina 1986; West et al. 2006).<br />
The geographic coverage <strong>of</strong> studies on marine fungi in red algae is very incomplete <strong>and</strong><br />
currently reflects the regions where the key workers have been based. For example, the<br />
studies reporting on Chytridium <strong>and</strong> Rhizophidium species are Sparrow (1936) in the northwest<br />
Atlantic, Aleem (1952b) in Sweden <strong>and</strong> Raghukumar (1987a, b) in India. Similarly, the<br />
only papers focusing on thraustochytrids are Quick (1974) in Florida, USA <strong>and</strong> Raghukumar<br />
(1986b, 1987a, b) <strong>and</strong> Raghukumar et al. (1992) in India.<br />
Other algae<br />
Parasitic red algae<br />
More research has been published on red algal <strong>parasites</strong> than on any other area <strong>of</strong> algal<br />
diseases, <strong>pathogens</strong> <strong>and</strong> <strong>parasites</strong> considered in this study. Red algal <strong>parasites</strong> are quite<br />
common, making up to 15% <strong>of</strong> all named red algal genera, although this figure needs revising<br />
as the last comprehensive review <strong>of</strong> red algal <strong>parasites</strong> was by G<strong>of</strong>f (1982). Red algal<br />
parasitism is the most specific symbiosis between two red algae: parasitic red algae are<br />
symbionts that have a reduced size <strong>and</strong> are either completely colourless or have reduced<br />
pigmentation <strong>and</strong> must rely on their nutrition from their host. In the past two decades a lot has<br />
been learned about the origin <strong>of</strong> red algal <strong>parasites</strong> (G<strong>of</strong>f et al. 1996, 1997, Zuccarello et al.<br />
2004), their development (G<strong>of</strong>f & Coleman 1984, 1985; G<strong>of</strong>f & Zuccarello 1994; Zuccarello<br />
& West 1994a), <strong>and</strong> host specificity (Nonomura & West 1981b; G<strong>of</strong>f & Zuccarello 1994;<br />
G<strong>of</strong>f et al. 1997, Zuccarello & West 1994b, c). However only a very small percentage <strong>of</strong><br />
these parasitic red algae have been studied in any detail beyond their first description.<br />
The host specificity <strong>and</strong> evolutionary studies are especially revealing in the context <strong>of</strong> algal<br />
pathogenicity <strong>and</strong> the effects <strong>of</strong> new interactions. Evolutionary studies have revealed that<br />
many red algal <strong>parasites</strong> are derived directly from their hosts (G<strong>of</strong>f et al. 1996, 1997). This<br />
was able to be understood once the development <strong>of</strong> <strong>parasites</strong> on their hosts was elucidated<br />
(G<strong>of</strong>f & Coleman 1984, 1985; G<strong>of</strong>f & Zuccarello 1994), showing that their unusual<br />
development was very similar to post-fertilisation processes in red algae. Early in their<br />
development, either upon spore germination or soon after, red algal <strong>parasites</strong> transfer into a<br />
host cell the cytoplasm <strong>of</strong> an entire cell, or the complete contents <strong>of</strong> a spore. This<br />
“transforms” the host cell as it now develops as a parasite, presumably under the control <strong>of</strong><br />
the transferred parasite nucleus, producing more parasite nuclei <strong>and</strong> dividing to form new<br />
parasite cells. Finally reproductive structures are formed which eventually will lead to new<br />
infections. These developmental processes are similar to the nuclear transfer <strong>and</strong> subsequent<br />
events that occur during post-fertilisation development in most red algae, <strong>and</strong> thus red algal<br />
parasitism has been hypothesised to have been derived from these post-fertilisation processes<br />
(G<strong>of</strong>f et al. 1996, 1997).<br />
Nuclear transfer places constraints on the host range <strong>of</strong> red algal <strong>parasites</strong>. The majority <strong>of</strong> red<br />
algal <strong>parasites</strong> appear to be host specific, although this could be an artifact <strong>of</strong> naming new<br />
parasite species when <strong>parasites</strong> are found on new hosts. However, when host range has been<br />
tested in culture it has been shown to be quite limited (e.g. G<strong>of</strong>f & Zuccarello 1994).<br />
Occasionally <strong>parasites</strong> can grow on closely related host species (Nonomura & West 1981b;<br />
Zuccarello & West 1994b, c), but <strong>of</strong>ten this alternate host development is reduced <strong>and</strong><br />
reproductive structures are not produced. Thus evidence to date supports a high level <strong>of</strong> host<br />
specificity. However, on an evolutionary time scale this is shown not to be so, as “host<br />
jumps” have been discovered using molecular markers. Parasites <strong>of</strong> the Gigartinales family<br />
MAF Biosecurity New Zeal<strong>and</strong> <strong>Diseases</strong>, <strong>pathogens</strong> <strong>and</strong> <strong>parasites</strong> <strong>of</strong> <strong>Undaria</strong> <strong>pinnatifida</strong> • 23