**Group 2**
Tasty parasites
Wiki site of the practical exercise of the [[http://www.ictp-saifr.org/ix-southern-summer-school-on-mathematical-biology/|IX Southern-Summer School on Mathematical Biology]].
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===== Introduction =====
{{http://media.nordicmicroalgae.org/large/Planktothrix%20agardhii_1.jpg?100 |Planktothrix agardhii}} Trophic interactions between phytoplankton (primary producers) and zooplankton (consumers) govern the flow of energy in aquatic systems. //Planktothrix agardhii// is an abundant aquatic cyanobacteria that can form algal blooms in freshwater lakes.
{{ https://upload.wikimedia.org/wikipedia/commons/4/4e/Daphnia_pulex.png?100|Daphnia sp.}} This small phytoplanktonic species displays resistance to grazing by zooplankton such as //Daphnia galeata// because of its filamentous morphology, production of toxins and low nutritional value. However, //Planktothrix// can be infected and killed by the obligate parasite //Rhizophydium megarrhizum//, a chytrid fungus. These parasitic fungi, in turn, have a free-living stage that is highly nutritional and an important food source for zooplankton. Thus, parasitic //Rhizophydium// fungi create an important trophic link between cyanobacteria and zooplankton termed the "//mycoloop//" (Agha et al. 2016).
{{:2020:groups:g2:polycentric-chytrid-feeding-on-filamentous-cyanobacteria-after-karling-1977.png?150 |Chytrid fungi feeding on filamentous cyanobacteria, Karling, J.S. (1977) Chytridiomycetarium Iconographia.}}Additionally, when //Planktothrix// cells are infected by //Rhizophydium//, their morphology and nutritional value change and, consequently, they become more edible to //Daphnia//. This way, //Rhizophydium// infection facilitates the grazing of //Planktothrix// by //Daphnia//, further strengthening the trophic link between phytoplankton and zooplankton.
===== Assignment =====
Propose and analyse a mathematical model that describes the trophic dynamics among cyanobacteria (primary producer/host), chytrids (parasite/prey) and zooplankton (grazer/predator).
===== Suggested questions =====
- Under what conditions can cyanobacteria, chytrid fungi and zooplankton coexist?
- Under what conditions do cyanobacteria blooms form?
Further well-grounded questions from the group are welcome.
===== References =====
T. Frenken et al. (2017) Integrating chytrid fungal parasites into plankton ecology: research gaps and needs. Environ Microbiol, 19: 3802-3822. DOI: [[https://doi.org/10.1111/1462-2920.13827|10.1111/1462-2920.13827]]
R. Agha, M. Saebelfeld, C. Manthey, T. Rohrlack and J. Wolinska. (2016) Chytrid parasitism facilitates trophic transfer between bloom-forming cyanobacteria and zooplankton (//Daphnia//). Scientific Reports 6:35039 DOI: [[https://www.doi.org/10.1038/srep35039|10.1038/srep35039]]. \\