Influence of melatonin on the successful infection of Daphnia dentifera by Metschnikowia bicuspidata
Data files
Nov 11, 2024 version files 95.84 KB
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Hughesetal_2024_CleanNov7.xlsx
94.07 KB
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README.md
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Abstract
Levels of the hormone melatonin fluctuate daily, with higher concentrations often found at night. These fluctuations likely influence multiple aspects of physiology, including the immune response. We demonstrated that the addition of exogenous melatonin increased the proportion of the freshwater zooplankton Daphnia dentifera that became infected by the fungal pathogen Metschnikowia bicuspidata, during the day but not at night. To determine the stage of this host-pathogen interaction at which melatonin may increase susceptibility, we conducted a series of laboratory experiments in which we raised Daphnia in the presence and absence of exogenous melatonin. To complete its life cycle, Metschnikowia must encounter a foraging host, overcome the host’s barrier resistance (gut wall) and evade the host’s immune response (internal clearance). We quantified encounter rate by measuring the gut passage time and the number of spores that entered the gut. We also measured the number of spores that successfully entered the body cavity (barrier resistance), and the hemocyte response to spores entering the body cavity (one metric of internal clearance). Finally, we quantified the effect of exogenous melatonin on triggering molting. The addition of exogenous melatonin lengthened gut passage time and decreased the number of spores present in the gut. We found no effect of melatonin on the percentage of gut spores successfully entering the host’s body cavity nor in the hemocyte response. Melatonin is known to influence the timing of molting and hosts that molted during exposure were more likely to become infected, likely due to a decrease in barrier resistance. In a fully factorial experiment, there was a high death rate, low infection rate, and therefore no discernible effect of melatonin on molting, molting or melatonin on infection. Our results provide insight into the stages of infection where melatonin does and does not have significant effects.
https://doi.org/10.5061/dryad.1zcrjdg1b
Description of the data and file structure
This paper presents the results from five laboratory experiments that investigate the role of exogenous melatonin on infection of the freshwater zooplankton Daphnia dentifera by the fungus Metschnikowia bicuspidata. There are 11 tabs in the datasheet.
Expt1 Infection results from Daphnia exposure to exogenous melatonin either during the day or at night.
Expt1_metadata Experiment 1 metadata
Expt2 Gut passage time of Daphnia exposed to exogenous melatonin and / or Metschnikowia in a fully-factorial experiment.
Expt2_metadata Experiment 2 metadata
Expt3_analysisI Counts of Metschnikowia spores in the gut, gut wall, and body cavity of the Daphnia in the presence and absence of exogenous melatonin. The gut penetrability metric is also calculated.
Expt3_analysisII Calculation of the average number of hemocytes per Metschnikowia spore for those hosts that had penetrating spores.
Expt3_metadata Experiment 3 metadata
Expt4a_analysisI Data for all Daphnia individuals for the analysis of if exposure to Metschnikowia or exogenous melatonin influences molting.
Expt4a_analysisII Data for those Daphnia individuals that were exposed to Metschnikowia to determine the effect of exogenous melatonin on infection.
Expt4b An additional experiment to determine the effect of molting on infection.
Expt4a&b_metadata Experiment 4 metadata
Sharing/Access information
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Code/Software
All analyses and data visualization were conducted in R 4.3.3 (R Core Team 2024) using standard models and packages as described in the methods of the manuscript.