Kristel has a new paper out in Freshwater Biology asking how toxins produced by cyanobacteria and time spent in the water column influence the infectivity of spores of the common fungal parasite Metschnikowia. This study was inspired by Kristel’s earlier work, published in Proceedings B, which showed that Anabaena and Microcystis diets protected Daphnia against fungal infections. Anabaena and Microcystis are known to produce potent toxins, and Kristel wondered if the protection against infection was due to a direct effect of the toxins on the spores. To test this, Kristel incubated spores in water containing varying levels of toxins for varying amounts of time. She found that toxins did not impact parasite fitness (infection prevalence and spore yield per infected host) or virulence (host lifetime reproduction and survivorship) at the tested concentrations (10 and 30 μg/L). However, spending longer as a transmission spore decreased a spore’s chances for successful infection: spores that were only incubated for 24 hr infected approximately 75% of exposed hosts, whereas spores incubated for 10 days infected less than 50% of exposed hosts. These results show both that spores have a limited time to find a new host, and that the protective effect of Anabaena and Microcystis diets on infection is not due to a direct effect of toxins on spores. Here’s a link to the new paper, and here’s the link to the data and code. Baili Zhong and Jorge Agudelo, both of whom were undergraduates in the lab via the Doris Duke Conservation Scholars Program, are coauthors on the study.
Anabaena collected from North Lake near Ann Arbor.
The Duffy Lab 