2.1.2 Parasites on parasites

Because every living organism is a potential shelter or food source, even parasites can be infected by other organisms. These are called hyperparasites. Hyperparasites are themselves prone to parasites, and numerous examples focused on land plants and animals can be found.

While algal pathology – as a scientific area – is only just taking off, records of aquatic hyperparasites affecting algal pathogens are still scarce and we will therefore use a land-based agriculture example as an illustration (see Figure 3).

Figure 3 The potato late blight agent Phytophthora infestans and its mycoparasite Pythium oligandrum.

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The diagram shows how the infection of potatoes by Phytophothora Infestans (which causes late blight) [centrally in the digram with arrow pointing to infected potato plant] can be in using Pythium oligandium [left of image, image of P oligandium top left, arrows to P Infestans, and image showing P oligandium parasiting P infestans bottom left].

Figure 3 The potato late blight agent Phytophthora infestans and its mycoparasite Pythium oligandrum.

While P. infestans is the causal agent of the potato late blight (responsible for the Irish potato famine in the nineteenth century), P. oligandrum is a soil-borne organism that can colonise and decay P.infestans hyphae. Those naturally occurring relationships can be exploited for agronomic purposes: P.oligandrum is the main active ingredient of several biocontrol treatments used to protect cultures from a range of pests.

Will the development of algal pathology reveal such complex and promising interactions?