Figure 1.
Locations where galls of Durvillaea antarctica caused by phytomyxean parasites were found in this study or by Aguilera et al. [27].
In 2011 the parasite was found in Necochea beach at Coliumo bay (in red), at the central coast of Chile, Pacific Ocean (map from [36], modified). Similar symptoms were reported from D. antarctica at the localities of Pudá and Valdivia [27], in black).
Figure 2.
Durvillaea antarctica occurring at the central coast of Chile.
a) Healthy population of D. antarctica in the natural environment; b) Light microscopic microphotograph of a cross-section of a dioecious frond of D. antarctica (stained with aniline blue) showing two female conceptacles (cp) with one free oogonium (white arrow), meristoderm (m), cortical (co) and medullary (me) zones in a normal frond; c) Scanning electron microphotograph (SEM) with details of the surface of the thallus, and cells disposition in the algal surface (arrow shows one cell); d) Detail of a cross-section of a normal thallus using SEM showing early stages in conceptacle development (cp), meristoderm (m), cortical (co) and medullar (me) tissue with normal swift hyphae (hy). Scale bar: a) 10 cm; b) 100 µm; c) 2 µm; and d) 50 µm.
Figure 3.
Infected Durvillaea antarctica samples from central Chile.
a) Gall-like structures (G) on infected fronds. Bar 1 cm. b) Enlarged D. antarctica cells in the cortical zone (co) filled with resting spores (white arrow) and plasmodia (black arrows) of Maullinia sp. The two plasmodia are in the process of developing into resting spores, because the beginning formation of the cell walls of the cystosori can be seen. Inlay: DAPI staining of a multinucleate plasmodiums which is in the process of developing into resting spores. Bar 10 µm. c) Resting spores of Maullinia sp. (Light microscopic image, DIC). Masses of single resting spores are completely filling the enlarged cells of D. antarctica. Bar 10 µm. d) SEM-micrograph showing the formation of the cortex (co), meristoderm (m), and enlarged cells infected by Maullinia sp. (arrows). Bar 20 µm. 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 D. antarctica samples from central Chile. Bar 2 µm.
Figure 4.
Phylogenetic tree of the partial 18S rDNA gene sequences from the novel Maullinia sp. which is parasitic in Durvillaea antarctica.
Maullinia sp. (JX163857) is placed within the Phagomyxida and sister to the second brown algal parasitic species of Phytomyxea Maullinia ectocarpii. The phylogenetic tree was constructed using Bayesian analyses running the GTR+I+R model with 1000000 generations (burnin = 1000). Posterior probabilities are shown above the nodes. The resolution of the branches within the Plasmodiophorida was better supported in PHYML analyses (data not shown).