DOI: 10.5061/dryad.v15dv425h
title: Data from: Non-senescent species are not immortal: Stress and decline in two planaria species

description: Potential immortality is observed in several species (e.g., prickly pear
 cactus, hydra, flatworms) and is indicative of their negligible or even
 negative senescence rates. Unlike in senescent species, which experience
 reduced individual performance with age due to physiological degradation,
 species with negligible or negative senescence display mortality rates
 that remain constant or decline with age, respectively. These rates vary
 across taxa and are correlated with life history traits. Yet, the extent
 to which variable resource availability, a key driver of variation in life
 history traits, impacts species that show negligible or negative
 senescence is currently unknown. Here, we examine whether and how
 variation in the quantity, quality, and feeding interval of resources
 impact population structure, population performance, and life history
 trait trade-offs in two long-lived planaria that do not
 senesce: Schmidtea mediterranea and Dugesia tahitiensis. In a
 full factorial design, different combinations of resource quantity
 (reduced intake, standard intake and high intake) and quality (high and
 low quality) were provided in two different feeding intervals (7-day and
 14-day intervals) for 19 weeks. We show that variability in
 resource availability, via decreases in quantity, quality, and frequency
 of resources, does not diminish population viability in either species but
 does result in suboptimal conditions of stress in S.
 Mediterranean. The high population viability we report can be
 attributed to two different mechanisms: increased reproduction or
 increased investment into maintenance at the expense of reproduction.
 Moreover, which mechanism was responsible for said high population
 viability was context-dependent and modulated by the specific life history
 strategy of the two planaria species. We show that suboptimal
 conditions can cause stress responses that have significant impacts on
 non-senescent species. The context-dependent response we observe suggests
 that species that do not senesce but are subject to suboptimal conditions
 of stress may ultimately exhibit declines in performance and ultimately
 die. A clearer understanding of the impact of suboptimal conditions of
 resource availability on non-senescent species is needed to determine the
 extent of stress experienced and ultimately whether a species can truly be
 immortal.
description: # Data from: Non-senescent species are not immortal: stress and decline in
 two planaria species
 [https://doi.org/10.5061/dryad.v15dv425h](https://doi.org/10.5061/dryad.v15dv425h) ## Description of the data and file structure To test our hypotheses regarding how variability in resource availability impacts populations of *S. mediterranea* and *D. tahitiensis*, we randomly assigned populations to a full-factorial design for each of the two species. This design included three resource factors: quality, quantity, and feeding interval. Quality of resource had two levels, differing in energy content and relative protein-to-carbohydrate ratio: high quality (high carbohydrate level, *HQ* hereafter) *vs.* low quality (low carbohydrate level, *LQ* hereafter). The high quality diet was organic calf’s liver and the low quality diet bloodworm. The protein-to-carbohydrate ratio indicates resource quality, with low carbohydrate-to-protein content corresponding to poorer quality (Lee et al. 2008). The two diets differed in their energy content (109 kcal/100g in the liver *vs. *14 kcal/100g in the bloodworm) and in their relative protein-to-carbohydrate ratios (1:0.35 in liver *vs.* 1:0.17 in bloodworm). Quantity of resources had three levels, which differed in the amount of calories available in each feeding: standard calorie intake (*SI*: 0.001g/individual, representative of intake to maintain laboratory populations (Jochen, 2018)), restricted calorie intake (*RI*: 0.0005g/ind.), hyper-calorie intake (*HI*: *ad libitum* which was at least 10 fold, approx. 0.01g/individual, that of the SI). Different combinations of resource quantity and quality were provided at two different intervals: once every seven days (*7D*), or every 14 days (*14D*). The total amount of resources provided over a 14-day period was equivalent for both feeding interval treatments (*i.e.*, one 14-day interval equalled two 7-day intervals) (see Fig. 1). As such, across the most extreme diet treatments, there is over a 300-fold difference in calories provided (per individual per unit time). To evaluate interactive effects of resource availability on population structure, population viability, and life history trait trade-offs, we replicated all treatments in the full factorial (n = 12 levels: 2 qualities: *HQvs.LQ*; 3 quantities: *RI*, *SI* & *HI*; 2 intervals: *7Dvs. 14D*) five times for each species. A replicate consisted of a petri dish (25mm deep × 150mm Ø) containing 10 clonal individuals each, henceforth referred to as a population (total n = 600 ind./spp.). For each population, individuals were randomly isolated from one of the three stock cultures and placed in the population 7-8 days before the start of the experiment. During this time, individuals were not fed to ensure individuals across all treatments were in a similar starved state at the start of the experiment. Treatment populations were randomised into three blocks containing 20 populations per species per block. For each species, all experimental blocks lasted 19 weeks (133 days) ### Files and variables #### File: Deere\_et\_al\_Dtah\_size\_spectra\_populations.csv **Description:** Data file of the size spectra slope values for populations of D. tahitiensis ##### Variables * Date: The day the photo of the population was taken * Week: The week that the photo of the population was taken (1 to 19) * Block: The experimental block (1, 2, 3) * Species: The species that was photographed (D. tahitiensis, S.mediterranea) * Treatment: The full treatment identification * HQ_RI_D – HQ, high quality; RI, reduced intake; D, delayed * HQ_SI_D – HQ, high quality; SI, standard intake; D, delayed * HQ_HI_D – HQ, high quality; HI, high intake; D, delayed * HQ_RI_E – HQ, high quality; RI, reduced intake; E, even * HQ_SI_E – HQ, high quality; SI, standard intake; E, even * HQ_HI_E – HQ, high quality; HI, high intake; E, even * LQ_RI_D – LQ, low quality; RI, reduced intake; D, delayed * LQ_SI_D – LQ, low quality; SI, standard intake; D, delayed * LQ_HI_D – LQ, low quality; HI, high intake; D, delayed * LQ_RI_E – LQ, low quality; RI, reduced intake; E, even * LQ_SI_E – LQ, low quality; SI, standard intake; E, even * LQ_HI_E – LQ, low quality; HI, high intake; E, even * Quality: Indicates diet quality (HQ, high quality; LQ, low quality) * Quantity: Indicates diet quantity (RI, reduced intake; SI, standard intake; HI, high intake) * Interval: Indicates feeding interval (D, delayed; E, even)  * Treatment_replicate: Indicates the population replicate for a given full treatment of a species. Each treatment has five replicates. For example: Dtah_HQ_RI_D_1 (Dtah = species; HQ_RI_D = full treatment; 1 = replicate 1) * pop_id: Indicates the population. All populations were given an identity between 1 and 60 representing all the populations used across all treatments for a species * b: The calculated size spectra slope value for a specific population (see main text and supplementary text for more details) * b_low: The lowest calculated size spectra slope value for a specific population * b_high: The highest calculated size spectra slope value for a specific population #### File: Deere\_et\_al\_Smed\_size\_spectra\_populations.csv **Description:** Data file of the size spectra slope values for populations of S. mediterranea ##### Variables * Date: The day the photo of the population was taken * Week: The week that the photo of the population was taken (1 to 19) * Block: The experimental block (1, 2, 3) * Species: The species that was photographed (D. tahitiensis, S.mediterranea) * Treatment: The full treatment identification * HQ_RI_D – HQ, high quality; RI, reduced intake; D, delayed * HQ_SI_D – HQ, high quality; SI, standard intake; D, delayed * HQ_HI_D – HQ, high quality; HI, high intake; D, delayed * HQ_RI_E – HQ, high quality; RI, reduced intake; E, even * HQ_SI_E – HQ, high quality; SI, standard intake; E, even * HQ_HI_E – HQ, high quality; HI, high intake; E, even * LQ_RI_D – LQ, low quality; RI, reduced intake; D, delayed * LQ_SI_D – LQ, low quality; SI, standard intake; D, delayed * LQ_HI_D – LQ, low quality; HI, high intake; D, delayed * LQ_RI_E – LQ, low quality; RI, reduced intake; E, even * LQ_SI_E – LQ, low quality; SI, standard intake; E, even * LQ_HI_E – LQ, low quality; HI, high intake; E, even * Quality: Indicates diet quality (HQ, high quality; LQ, low quality) * Quantity: Indicates diet quantity (RI, reduced intake; SI, standard intake; HI, high intake) * Interval: Indicates feeding interval (D, delayed; E, even)  * Treatment_replicate: Indicates the population replicate for a given full treatment of a species. Each treatment has five replicates. For example: Dtah_HQ_RI_D_1 (Dtah = species; HQ_RI_D = full treatment; 1 = replicate 1) * pop_id: Indicates the population. All populations were given an identity between 1 and 60 representing all the populations used across all treatments for a species * b: The calculated size spectra slope value for a specific population (see main text and supplementary text for more details) * b_low: The lowest calculated size spectra slope value for a specific population * b_high: The highest calculated size spectra slope value for a specific population #### File: Deere\_et\_al\_Planaria\_count\_data.csv **Description:** Data file of the weekly population counts for both species of planaria (D. tahitiensis and S. mediterranea) ##### Variables * Date: The day the population was counted * Week: The week that the population was counted (1 to 19) * Block: The experimental block (1, 2, 3) * Species: The species that was photographed (D. tahitiensis, S.mediterranea) * Treatment: The full treatment identification * HQ_RI_D – HQ, high quality; RI, reduced intake; D, delayed * HQ_SI_D – HQ, high quality; SI, standard intake; D, delayed * HQ_HI_D – HQ, high quality; HI, high intake; D, delayed * HQ_RI_E – HQ, high quality; RI, reduced intake; E, even * HQ_SI_E – HQ, high quality; SI, standard intake; E, even * HQ_HI_E – HQ, high quality; HI, high intake; E, even * LQ_RI_D – LQ, low quality; RI, reduced intake; D, delayed * LQ_SI_D – LQ, low quality; SI, standard intake; D, delayed * LQ_HI_D – LQ, low quality; HI, high intake; D, delayed * LQ_RI_E – LQ, low quality; RI, reduced intake; E, even * LQ_SI_E – LQ, low quality; SI, standard intake; E, even * LQ_HI_E – LQ, low quality; HI, high intake; E, even * Quality: Indicates diet quality (HQ, high quality; LQ, low quality) * Quantity: Indicates diet quantity (RI, reduced intake; SI, standard intake; HI, high intake) * Interval: Indicates feeding interval (D, delayed; E, even)  * Treatment_replicate: Indicates the population replicate for a given full treatment of a species. Each treatment has five replicates. For example: Dtah_HQ_RI_D_1 (Dtah = species; HQ_RI_D = full treatment; 1 = replicate 1) * Total_no: Indicates the total number of individuals in the population * New_indivs: Indicates the number of new individuals within the population (compared to the previous week) * Pop_surv: Indicates if the population has survived to the date in question (1, survived; 0, extinct) * Location: Indicates the location of the population during the experiment (Department lab, Home lab) #### File: Deere\_et\_al\_Planaria\_size\_data.csv **Description:** Data file of the weekly population size measurements for each individual in a population for both species of planaria (D. tahitiensis and S. mediterranea) ##### Variables * Date: The day the photo of the population was taken * Week: The week that the photo of the population was taken (1 to 19) * Block: The experimental block (1, 2, 3) * Species: The species that was photographed (D. tahitiensis, S.mediterranea) * Treatment: The full treatment identification * HQ_RI_D – HQ, high quality; RI, reduced intake; D, delayed * HQ_SI_D – HQ, high quality; SI, standard intake; D, delayed * HQ_HI_D – HQ, high quality; HI, high intake; D, delayed * HQ_RI_E – HQ, high quality; RI, reduced intake; E, even * HQ_SI_E – HQ, high quality; SI, standard intake; E, even * HQ_HI_E – HQ, high quality; HI, high intake; E, even * LQ_RI_D – LQ, low quality; RI, reduced intake; D, delayed * LQ_SI_D – LQ, low quality; SI, standard intake; D, delayed * LQ_HI_D – LQ, low quality; HI, high intake; D, delayed * LQ_RI_E – LQ, low quality; RI, reduced intake; E, even * LQ_SI_E – LQ, low quality; SI, standard intake; E, even * LQ_HI_E – LQ, low quality; HI, high intake; E, even * Quality: Indicates diet quality (HQ, high quality; LQ, low quality) * Quantity: Indicates diet quantity (RI, reduced intake; SI, standard intake; HI, high intake) * Interval: Indicates feeding interval (D, delayed; E, even)  * Treatment_replicate: Indicates the population replicate for a given full treatment of a species. Each treatment has five replicates. For example: Dtah_HQ_RI_D_1 (Dtah = species; HQ_RI_D = full treatment; 1 = replicate 1) * Individual: Indicates the individual that was measured within a population * Area_px: Indicates the size of the individual measured in pixels * Area_mm: Indicates the size of the individual measured in mm (based on a conversion factor; see main text and supplementary information text for more details) ## Code/software CellProfiler was used to measure individual planaria within each population. A project file for each species was created with unique settings, these project files are labelled as 'Deere et al_Smed.cpproj' for the species S. mediterranea and 'Deere et al_Dtah.cpproj' for D. tahitiensis. R version 4.0.3 was used for the body size and population count analysis. A Bayesian framework was used with the following packages installed:     'dplyr', 'brms', 'tidybayes', 'posterior'. Scripts for the analysis can be found in the files labelled 'Deere_et_al_Population_count_analysis.R' and 'Deere_et_al_Size_spectra_slope_analysis.R'