Date of this Version
Barrows H. G. 2021. The effects of various nutrient concentrations in algae on infection in Daphnia dentifera.
Nutrient quality in food leading to malnutrition or overnutrition have implications on host immune function. Different nutrient concentrations in Ankistrodesmus falcatus algae were given to Daphnia dentifera and further exposed to their pathogen Metschnikowia bicuspidata spores for 12 hours. This research helps provide more information on host-parasite dynamics and the nutritional impact on an organism’s immune system. I created three algal nutrient treatments: a control treatment, a treatment where the algae was raised in water with half the control amount of nutrients, and a treatment with double the control amount of nutrients. Daphnia were split into three treatment groups and received one of the algal types for the duration of their life. When the D. dentifera were mature, they were exposed to M. bicuspidata spores for 12 hours and maintained for two weeks. After two weeks, I measured each individual’s body size, fecundity (total offspring), and infection intensity (total number of pathogen spores). I found no significant difference in the probability of infection or infection intensity between groups. However, the double nutrient treatment showed the lowest probability of infection. All exposed groups showed anorexic behaviors, and the double nutrient algae treatment had smaller body sizes and lower fecundity rates. This decreased size and fecundity in the double nutrient treatment linked with lower probabilities of infection indicate a life-history trade-off with food stress and immunity. Further research should attempt to answer why organisms display anorexic behaviors when exposed to pathogens and why organisms develop certain life-history traits under poor nutrient conditions.