DOI: 10.5061/dryad.d51c5b0c4
title: Data from: Virulence and transmission biology of the widespread, ecologically important pathogen of zooplankton, Spirobacillus cienkowskii

description: Spirobacillus cienkowskii (Spirobacillus, hereafter) is
 a widely distributed bacterial pathogen that has significant impacts on
 the population dynamics of zooplankton (Daphnia spp.), particularly in
 months when Daphnia are asexually reproducing. Yet
 little is known about Spirobacillus’ virulence,
 transmission mode and dynamics. As a result, we cannot explain the
 dynamics of Spirobacillus epidemics in nature or
 use Spirobacillus as a model pathogen,
 despite Daphnia’s tractability as a model-host. Here, we
 work to fill these knowledge gaps experimentally. We found
 that Spirobacillus is among the most virulent
 of Daphnia pathogens, killing its host within a week and
 reducing host fecundity. We further found
 that Spirobacillus did not transmit horizontally among
 hosts unless the host died or was destroyed (i.e., it is an “obligate
 killer”). In experiments aimed at quantifying the dynamics of horizontal
 transmission among asexually reproducing Daphnia, we demonstrated
 that Spirobacillus transmits poorly in the laboratory. In
 mesocosms, Spirobacillus failed to generate epidemics; in
 experiments wherein individual Daphnia were
 exposed, Spirobacillus’ transmission success was low. In
 the (limited) set of conditions we
 considered, Spirobacillus’ transmission success did not
 change with host density or pathogen dose and declined following
 environmental incubation. Lastly, we conducted a field survey
 of Spirobacillus’ prevalence within egg-cases (ephippia)
 made by sexually reproducing Daphnia. We
 found Spirobacillus DNA in ∼40% of ephippia, suggesting
 that, in addition to transmitting horizontally among asexually
 reproducing Daphnia, Spirobacillus may transmit
 vertically from sexually reproducing Daphnia. Our work fills
 critical gaps in the biology of Spirobacillus and illuminates new
 hypotheses vis-à-vis its life-history.
description: Data was collected in the laboratory of M.A. Duffy (U. Michigan)
 between 2016-2019, according to the experimental methods described in the
 publication. Broadly, individual <em>Daphnia </em>or cohorts
 of <em>Daphnia </em>were exposed to <em>Spirobacillus
 cienkowskii </em>and their symptoms (coloration) and fitness
 (survival, reproduction) was tracked. 
description: # Data from: Virulence and transmission biology of the widespread,
 ecologically important pathogen of zooplankton, *Spirobacillus
 cienkowskii*
 [https://doi.org/10.5061/dryad.d51c5b0c4](https://doi.org/10.5061/dryad.d51c5b0c4) ## Description of the data and file structure ### Files and variables In all cases, missing values indicated by "NA" #### File: ephippia\_survey.csv Data from a field survey of ephippia for *Spirobacillus cienkowskii* ##### Variables * sample_id: unique id of each ephippium * concentration_ul: no. copies gene per microliter. Note that samples containing &lt;0.048 = are deemed negative.  * total_sample: no. copies gene per sample. Note that samples containing &lt;0.048= are deemed negative.  * lake: lake from which sample collected * species: species of *Daphnia* to which ephippium belongs #### File: exp\_5b.csv Data from experiment 5b. ##### Variables * exp.day: experimental day, where 0 is the day recipients were exposed to putatively infectious material. * block: experimental block * f.waittime: days after water inoculated * rep: replicate id within a treatment * red: appearance of recipient animal. 1 = red; 0.5 =white or less transparent than normal, 0 = transparent * dead: 1 = dead, 0 = alive * stopped: indicates whether/when animal was removed from experiment for a non-biological reason e.g., accidental spillage, animal could not be observed. 1 = yes ; 0 = no * comments: experimenter observations or comments * unq.id: unique id of each animal, across whole experiment #### File: exp\_5a.csv Data from experiment 5a. ##### Variables * day: experimental day, where day 0 is the day when recipients exposed to infectious material.  * day_removed: days after inoculation that primary cohort removed, equivalent to f.waittime in exp. 5a. * beaker: id of beaker containing cohort at time of observation * cohort: cohort to which recipients belong. primary = cohort added to beaker at day of inoculation and later removed after day_removed no. days; secondary = cohort added to focal mesocosom after primary cohort removed * any_red: indicates whether red animals were present. y = yes; n = no * \#red: no. animals red in appearance * pink: no. animals pink in appearance * cohortid: unique cohort id * beaker_id: unique id of focal mesocosm #### File: exp\_1\_pilot.csv Data from preliminary experiment used to design experiment 1. Data is presented in the supplement. ##### Variables * id: unique animal id * hour: hours after experiment started i.e., after which all red animals were added to beakers * dead: 1 = dead, 0 = alive * mobile: 1 = yes, 0 = no * breathing: 1 = yes, 0 = no * comments: experimenter observations or comments #### File: exp\_3.csv Data from experiment 3 ##### Variables * day: experimental day, where day 0 is the day on which recipients exposed * block: experimental block  * dose: no. donor animals worht of material to which recipients exposed * id: unique recipient id, within a block * treatment: as" dose" but where c = control (0 donors) * rep: replicate id within a treatment * babies: number of offspring observed and removed * red: appearance of recipient animal. 1 = red; 0.5 = white or less transparent than normal, 0 = transparent * stopped: indicates whether/when animal was removed from experiment for a non-biological reason e.g., accidental spillage, animal could not be observed. 1 = yes ; 0 = no * dead: 1 = dead, 0 = alive * unq.id: unique id of each animal across whole experiment #### File: exp\_4.csv Data from experiment 4. ##### Variables * block: experimental block  * day: experimental day, where day 0 is the day on which recipients were exposed * treatment: no. recipients in beaker. single (1 recipient); double (2 recipients) * beaker: unique id of beaker within a block * animal_id: Used to track the status of animals in the "double treatment" and to ensure the status of two animals was recorded. When both animals were alive and asymptomatic, "a" and "b" were not distinguishable. "b" was assigned to the animal remaining in a "double" beaker if the other animal died or which became symptomatic after the first.  * id: unique animal id within an block * red: appearance of recipient animal. 1 = red; 0.5 =white or less transparent than normal, 0 = transparent * babies_removed: whether offspring observed and removed from beaker. 1 = yes; 0 = no * stopped: indicates whether/when animal was removed from experiment for a non-biological reason e.g., accidental spillage, animal could not be observed. 1 = yes ; 0 = no  * dead: 1 = dead, 0 = alive * unq.id: unique id of each recipient across whole experiment #### File: exp\_2.csv Data from experiment 2. ##### Variables * flask: id of mesocosm * day: experimental day, where day 0 is the day donors added to the mesocosm. * sample_id: id of the subsample taken to assess prevalence from a particular mesocosm, on a particular experimental day * symp_alive: no. alive symptomatic animals observed in subsample * asymp_alive: no. alive asymptomatic animals observed in subsample * total: total number animals in subsample * symp_dead: no. dead symptomatic animals observed * exp: as "block" in other experiments * volume: volume in ml of flask at time of inoculation * fl.id: unique id of each flask across the whole experiment * susceptible_seed: no. of recipients on day 0 * infected_seed: no. of recipients on day 0 #### File: exp\_1.csv Data from experiment 1 ##### Variables * id: unique id of each animal * initials: intitials of person who made observation * day: experimental day, where 0 is the day recipients placed in beakers and exposed to donor and/or crushed remains of infected animal * rep: replicate id within a treatment * color: appearance of recipient animal. 1 = red; 0.5 =white or less transparent than normal, 0 = transparent * dead: 1 = dead; 0 = alive * stopped: indicates whether/when animal was removed from experiment for a non-biological reason e.g., accidental spillage, animal could not be observed. 1 = yes ; 0 = no * babies: number of offspring counted * order.inspected: order in which recipient status was assessed following exposure on day 0, where "1" indicates animal was inspected first * focal_alive: indicates whether recipient animal was alive after the exposure period. y = yes * treatment: status of donor animal (as described in experimental methods) * bioday: day post-exposure, where 0 is the day recipient first exposed to putatively infectious material. Accounts for the fact that animals in the dead treatment were exposed on day 1 so they are biologically one day behind. * rlzd.tmt: as per treatmentt but when "alive" animal died during the exposure period assigned "donor-dead".