DOI: 10.5061/dryad.44j0zpcvd
title: Fasting reduces viral susceptibility in oysters until energy depletion becomes detrimental

description: While abundant food supplies support host immunity, they may also fuel
 pathogen proliferation, whereas food limitation restricts resources for
 both host and parasite. The balance between these processes, and the
 physiological limits to fasting as a protective strategy, remain poorly
 understood. Here, we tested how the duration and timing of food
 deprivation relative to pathogen exposure affect resistance to infection,
 using the oyster Magallana gigas and its pathogen, Ostreid herpesvirus 1.
 We used a cross-over design with two sequences differing in the timing of
 starvation relative to infection. We hypothesized that (i) survival would
 increase with fasting duration until a threshold is reached where energy
 depletion becomes detrimental, and (ii) fasting would only protect when it
 immediately precedes infection, because its effect relies on reduced host
 metabolism. Consistent with these hypotheses, oysters fasted immediately
 before infection showed increased survival peaking after 14-28 days,
 followed by a sharp decline, while prior fasting with refeeding provided
 no benefit. Biochemical analyses revealed that advanced protein catabolism
 may underlie the tipping point where starvation shifts from protective to
 detrimental effects on disease resistance.
description: # Fasting reduces viral susceptibility in oysters until energy depletion
 becomes detrimental Dataset DOI:
 [10.5061/dryad.44j0zpcvd](https://doi.org/10.5061/dryad.44j0zpcvd) ##
 Description of the data and file structure This dataset contains
 measurements obtained during controlled oyster feeding and starvation
 experiments during exposure to a viral disease. The dataset includes
 environmental data, survival tracking, morphological measurements, and
 biochemical analyses. All data are contained in tab-delimited files with a
 comma decimal. #### Env_data.csv Water chemistry and tank conditions
 recorded during acclimation (n/a: not applicable, NA: not available). |
 Column | Description | Units | | :----------- |
 :---------------------------------------------------------------------- |
 :--------------------------------------------------------------------------------- | | Date | Date of measurement | DD-MMM | | Food | Feeding condition | Fed or starved | | Period | Experiment phase | Acclimation or virus exposure (infection) | | Tank | Tank identification number | From 1 to 6 | | Diet | Algal diet | Iso: *T-Isochrysis lutea*, Chaeto: *Chaetoceros sp.,* Skel: *Skeletonema costatum* | | Inlet | Phytoplancton cell concentration at water inlet | um^3^ uL⁻¹ | | Outlet | Phytoplancton cell concentration at water outlet (um^3^ per uL⁻¹) | um^3^ uL⁻¹ | | In\_Out | Difference between inlet and outlet (`Inlet - Outlet`) (um^3^ per uL⁻¹) | um^3^ uL⁻¹ | | O2 | Dissolved oxygen | mg L⁻¹ | | pH | pH of seawater | pH unit | | T | Temperature | °C | | Salinity | Salinity | PSU | | Flow\_L\_h-1 | Flow rate | L·h⁻¹ | #### Survival_data.csv Data used for plotting survival curve and survival analyses | Column | Description | Units | | :--------------- | :------------------------------------------- | :--------------------------------------- | | NTOT | Total number of oyster (initial) | - | | Tank\_I | Tank number at the onset of the experiment | From 1 to 6 | | Rep | Replicate tank number | From 1 to 3 | | Food | Food regime | Fed or starved | | Line | Oyster line | NSI or F14 | | ID | - | - | | Tank\_F | Tank number at the end of the experiment | From 1 to 6 | | Sequence | 1: Fed to staved, 2: starved to fed | 1 or 2 | | Time of transfer | Days of transfer | Days | | Date of transfer | Date | DD-MMM,DDMMMYYYY, or n/a: not applicable | | Feeding time | Feeding duration | Days | | Starving time | Starving duration | Days | | HPI | Hours post-infection | H | | Dead | Number of dead oysters | - | | Sampling | Number of sampled oysters | - | | Cumn | Cumulative number of counted oysters | - | | n | number of censored oysters (dead or sampled) | - | | Censoring | 1=dead, 0=sampled | 0 or 1 | 
 
 ### Biometry_data.csv Morphometric data of oysters | Column | Description
 | Units | | :--------------- | :-----------------------------------------
 | :------------- | | Tank\_I | Tank number at the onset of the experiment
 | From 1 to 6 | | Tank\_F | Tank number at the end of the experiment |
 From 1 to 6 | | Line | Oyster line | NSI or F14 | | Food | Food regime |
 Fed or starved | | Sequence | 1: Fed to staved, 2: starved to fed | 1 or 2
 | | Time of transfer | Days of transfer | Days | | Mass\_I | Initial
 biomass of oysters | g | | Mass\_F | Final biomass of oysters | g | |
 d\_mass | Final-Initial | g | | Starving time | Starving duration | Days |
 | Mean\_length\_15 | Mean shell length of 15 individual oysters | mm | ###
 Biochemistry_data.csv Tissue composition (carbohydrates, proteins,
 lipids), and related derived metrics (NA: not available) | Column |
 Description  | Units | | :------------ |
 :----------------------------------------- | :------------- | | Tank\_I |
 Tank number at the onset of the experiment | From 1 to 6 | | Tank\_F |
 Tank number at the end of the experiment | From 1 to 6 | | Line | Oyster
 line | NSI or F14 | | Food | Food regime | Fed or starved | | ID | - | - |
 | Starving time | Starving duration | Days | | Carbo\_pct | mass
 percentage of fresh flesh | % | | TAG\_ST | triacylglycerol-to-sterol
 ratio | - | | Prot\_pct | mass percentage of fresh flesh | % | ##
 Code/software All analyses were performed in **R v. 4.3.2**. **Survival
 analyses** were conducted using the `survival` package for Kaplan–Meier
 estimates and Cox proportional hazards models, and the `coxme` package for
 mixed-effects Cox models. **Analyses of variance (ANOVA)** were conducted
 using the `aov()` function from base R.