Figure 8.

Life cycle of Eurychasma dicksonii in its brown algal host Ectocarpus siliculosus. (A) A spore (arrow) attaches to the algal surface and injects its content into the host. (B) Within the algal cytoplasm, the Eu. dicksonii thallus (arrow) develops which, at the early stage of infection, is unwalled. (C) Later, the pathogen thallus (arrow) has a cell wall and causes hypertrophic expansion of the algal host cell. (D) At the final stage, the complete thallus differentiates into a sporangium from which motile zoospores (arrow) are produced, completing the life cycle of the pathogen. Scale bars equal to 25 μm. (Figure reproduced from Strittmatter et al. 2016.)