DOI: 10.5061/dryad.tdz08kq57
title: Dust you shall eat: Complex considerations underlying a simple diet

description: Animals assimilate macronutrients and mineral nutrients in specific
 quantities and ratios to maximize fitness. To achieve this, animals must
 ingest different foods that contain the needed nutrients or facilitate the
 digestion of those nutrients. We explored how these multidimensional
 considerations affect the desert isopods (Hemilepistus reaumuri) food
 selection, using field and laboratory experiments. Wild isopods consumed
 3-fold more macronutrient-poor biological soil crust (BSC) than plant
 litter.  Isopods tightly regulated macronutrient and calcium
 intake, but not phosphorus when eating the two natural foods and when
 artificial calcium and phosphorus sources substituted the BSC. Despite the
 equivalent calcium ingestion, isopods performed better when eating BSC
 compared to artificial foods. Isopods that consumed BSC sterilized by
 gamma-radiation ate more but grew slower than isopods that ate live BSC,
 implying that ingested microorganisms facilitate litter digestion. Our
 work highlights the need to reveal the multifaceted considerations that
 affect food-selection when exploring trophic-interactions.
description: Please refer to the Methods section in the manuscript and
 Appendix 1, which elaborates on the method even further.
description: # Dust you shall eat: Complex considerations underlying a simple diet
 [https://doi.org/10.5061/dryad.tdz08kq57](https://doi.org/10.5061/dryad.tdz08kq57) The data contains 7 CSV files that are correlated to (and named as) the 4 experiments described in the MS. All statistical analyses were performed in SPSS ver. 26 (SPSS Inc., Chicago, IL, USA), therefore no code was uploaded. **1.     First experiment - 'Feeding observations in the field'**: here we identified the isopod diet choices (selection between their two main food sources) in their natural habitat. One file is related to this experiment: 1\) '*1- Feeding observations in the field.csv*' (See **Description of the data and file structure** below) \* The data collected in this exp is not analyzed nor presented in a figure (only described in the results section). **2.     Second experiment - 'Dietary choices - laboratory experiment using artificial foods'**: here we characterized the isopods' intake target for protein, carbohydrates, and calcium. The data is presented in a two-panel figure in Appendix 2 (Fig S1a,b). Two files are related to this experiment: 1\) *'2 - laboratory experiment using artificial foods - Fig 1Sa.csv*' 2\) '*2 - laboratory experiment using artificial foods - Fig 1Sb.csv*' (See **Description of the data and file structure** below) **3.     Third experiment - 'Calcium and Phosphorous regulation - laboratory experiment'**:  here we combined natural and artificial foods in 6 dietary treatments in the lab to explore whether isopods ingest biological soil crust (BSC) to satisfy their calcium (Ca) and phosphorus (P) needs. We recorded the amount eaten from each food type, the isopods' feces, and their assimilation efficiency. Based on the food composition, we calculated the amount of macro and micronutrients consumed. To test how the diet choices and restrictions affected the isopods, at the end of the experiment we measured the isopods' body composition, wet and dry weight, and morphology and calculated their body condition. The data from this experiment is presented in figures 2-5 and the data for each figure is found on a different file. Three files are related to this experiment: 1\) '*3 - Calcium and Phosphorous regulation - laboratory experiment - Fig 2.csv*' 2\) '*3 - Calcium and Phosphorous regulation - laboratory experiment - Fig 3.csv*' 3\) '*3 - Calcium and Phosphorous regulation - laboratory experiment - Fig 4 and 5.csv*' (See **Description of the data and file structure** below) **4.  Forth experiment - 'Digestion assisting agents - laboratory experiment'**: here we tested if the microorganisms in the BSC are another driver for its consumption. We followed the isopods consumption of the three soil types and also their weight gain. One file is related to this experiment: 1\) 4 - Digestion assisting agents - laboratory experiment - Fig 6*.csv*' (See **Description of the data and file structure** below) \** ** **Description of the data and file structure** **1.      First experiment - 'Feeding observations in the field'** File '*1- Feeding observations in the field.csv*' has 5 columns: A)   Date: the date on which the observation was made B)   Mesocosm_ID: the mesocosm in which the observation was made C)   Isopods_located_on_crust: the number of isopods observed feeding on crust (BSC) in the specific observation D)   Isopods_located_on_plant_litter: the number of isopods observed feeding on plant litter in the specific observation E)    Precent_isopods_on_crust: the percentage of isopods feeding on crust (BSC) in the specific observation **2.     Second experiment - 'Dietary choices - laboratory experiment using artificial foods'**: 1\) File *'2 - laboratory experiment using artificial foods - Fig 1Sa.csv*' has 11 columns: A)   Microcosm_number: the microcosm in which the measurement was made. B)   Food_type: the type of food that was measured for its consumption by the isopods. **Prot-carbs **stands for the sum of the two macronutrient-rich foods [protein-rich (19% Protein: 1% Carbohydrates) and carbohydrates-rich food (1% Protein: 19% Carbohydrates)]. **Ca** stands for the macronutrient-deficient Ca-rich artificial food (CaCO3 solidified by 2.5% agar). See Appendix 1 of the paper for details. C-K) Each column stands for each of the 9 different periods throughout the experiment. Each period was 5 days, and the column name represents the period number and the total number of days passed from the beginning of the exp until the specific measurement of that period, i.e., *Period_1_5_days*, *Period_2_10_days*….. * Period_9_45_days*. The value in each cell represents the weight (mg) of the specific food that was eaten in the mesocosm during that period. The value is standardized to the number of isopods that were in the microcosm in that specific period and to the number of days in the period (5 for all). 2\) File *'2 - laboratory experiment using artificial foods - Fig 1Sb.csv*' has 11 columns: A)   Microcosm_number: the microcosm in which the measurement was made. B)   Food_type: the type of food that was measured for its consumption by the isopods. **Protein **stands for the protein-rich food (19% Protein: 1% Carbohydrates). **Carbs** stands for the carbohydrates-rich food (1% Protein: 19% Carbohydrates)]. C-K) Each column stands for each of the 9 different periods throughout the experiment. Each period was 5 days, and the column name represents the period number and the total number of days passed from the beginning of the exp until the specific measurement of that period, i.e., *Period_1_5_days*, *Period_2_10_days*….. * Period_9_45_days*. The value in each cell represents the weight (mg) of the specific food that was eaten in the mesocosm during that period. The value is standardized to the number of isopods that were in the microcosm in that specific period and to the number of days in the period (5 for all). **3.    Third experiment - 'Calcium and Phosphorous regulation - laboratory experiment'**:  1\) File '*3 - Calcium and Phosphorous regulation - laboratory experiment - Fig 2.csv*' has 8 columns: A)   Microcosm_number: the microcosm in which the measurement was made. B)   Group: the group to which the microcosm belongs (see Appendix 1 for details).   C)   Treatment: the dietary treatment provided in the specific microcosm (see explanations for the abbreviations in the methods section). D-H) Each column stands for each of the 5 different food types provided in the experiment: **Crust** – Biological soil crust, **Litter** – Plant litter, **CaCO3** - Ca-rich artificial food, **1_percent_P** - a mixture of CaCO3 and CaHPO4 (1% P), **2_percent_P** - a mixture of CaCO3 and CaHPO4 (1% P). See the methods section in the paper for further information on the food types used in the experiment. The value in each cell represents the weight (mg) of the specific food that was eaten in the mesocosm during the entire experiment. The value is standardized to the average weight of the isopods in the specific microcosm throughout the experiment. Multiple cells contain a value of 0 since only part of the foods were provided in each microcosm (depending on the dietary treatment). 2\) File '*3 - Calcium and Phosphorous regulation - laboratory experiment - Fig 3.csv*' has 7 columns: A)   Microcosm_number: the microcosm in which the measurement was made. B)   Group: the group to which the microcosm belongs (see Appendix 1 for details).  C)   Treatment: the dietary treatment provided in the specific microcosm (see explanations for the abbreviations in the methods section). D-H) Each column stands for a type of nutrient which its consumption was evaluated: **Calcium, Phosphorus, proteins, and Carbohydrates. ** The value in each cell represents the amount (mg) of the specific nutrient that was eaten in the mesocosm throughout the entire experiment. The value is standardized to the average weight of the isopods in the specific microcosm throughout the experiment. 3\) File '*3 - Calcium and Phosphorous regulation - laboratory experiment - Fig 4 and 5.csv*' has 14 columns: A)   Microcosm_number: the microcosm in which the isopod was in. B)   Group: the group to which the microcosm of that specific isopod belongs (see Appendix 1 for details).  C)   Treatment: the dietary treatment provided in the microcosm in which the isopod was (see explanations for the abbreviations in the methods section). D)   Isopods_number: the number of the isopod that was measured (arbitrary). E)    Isopods_sex: the sex of the isopod that was measured (m=male, f=female). F)    Final_wet_weight_g: The wet weight of the isopods at the end of the experiment (g) G)   Final_dry_weight_g: The dry weight of the isopods at the end of the experiment (g) H)   Precent_moisture: The isopod's moisture at the end of the experiment [calculated as (wet weight – dry weight)/wet weight X 100]. I)     Fifth_segment_width_µm: The wisth of the fifth segment of the isopod (µm). J-N) These columns present the elemental content of the isopods. Each column stands for a specific element or ratio of two elements: **Phosphorus**, **Calcium**, **Nitrogen**, **Carbon**, and **Carbon:Nitrogen ratio**. The value in each cell represents the percentage of the specific element in the isopod that was tested.  (mg) of the specific food that was eaten in the mesocosm during the entire experiment. Multiple cells are empty since only part of the isopods were tested for their body content (see method section for details).   **4.    Forth experiment - 'Digestion assisting agents - laboratory experiment'** 1\) File '*4 - Digestion assisting agents - laboratory experiment - Fig 6.csv*' has 7 columns: A)   Microcosm_ID: the microcosm in which the measurement was made. B)   Isopods_family: the family from which the experimental isopods were taken (serves as a random factor). C)   Treatment: the dietary treatment provided in the microcosm. D)   Plant_Litter_eaten: plant litter eaten throughout the experiment. The value in each cell represents the amount (mg) eaten by the isopods in the microcosm throughout the entire experiment. The value is standardized to the average weight of the isopods in the specific microcosm throughout the experiment. (mg) of the specific food that was eaten in the mesocosm during the entire experiment. Multiple cells are empty since only part of the isopods were tested for their body content (see method section for details).  E)    Soil_eaten: soil eaten throughout the experiment. The value in each cell represents the amount (mg) eaten by the isopods in the microcosm throughout the entire experiment. The value is standardized to the average weight of the isopods in the specific microcosm throughout the experiment. (mg) of the specific food that was eaten in the mesocosm during the entire experiment. Multiple cells are empty since only part of the isopods were tested for their body content (see method section for details).  F)    Soil_to_litter_ratio: the ratio between the amount of soil and litter eaten. G)   Mass_gain: the increase in isopods weight (mg) throughout the experiment.  Values are standardized to the number of mean isopods found in the microcosm throughout the experiment. \* Microcosms with no values (N/A) in the cells are thus in which there was high mortality and were taking out of the analysis (see method section and Appendix 1 for details).