Dark tolerance fitness.

<p>Survival through time for ten clones in the a) L:D treatment and b) dark treatment. c) Mean cumulative number of neonates produced by surviving <i>Daphnia</i> in the dark and diel treatments. Capital letters indicate statistically significant differences between treatments for a given clone. d) Relationship between proportion survival in the dark treatment and proportional difference in fecundity between treatments (L:D / dark fecundity). Each data point represents a clone. A value of 1 on the Y-axis represents equal fecundity between diel and dark treatments. Circled point was identified as an outlier (SYSTAT 12). Clone line variability over time should be noted, specifically looking at >80 hours (b) and that clones with the lowest survival at 160+ hours (b) are typically associated with differences in diel and dark tolerances (c) over the course of the experiments.</p

Survival of <i>D</i>. <i>parvula</i>.

<p>Number <i>Daphnia parvula</i> surviving to Day 5 for each of three clones held under dark and L:D conditions. Capital letters designate significant statistical differences between treatments within a clone. Effects of dark conditions on only some clones should be noted.</p

Comparison of Mean Cumulative Fecundity Between the Dark and Diel Treatments (7-day).

<p>Comparison of Mean Cumulative Fecundity Between the Dark and Diel Treatments (7-day).</p

UV tolerance fitness.

<p>Left panels: Proportion survival of six <i>D</i>. <i>parvula</i> clones at Day 5 after phototron exposure to 41, 32, and 18 KJ. Right panel: Relationship between proportion survival after phototron exposure and proportion survival in the dark treatment for six clones. Graph for 41 KJ omitted due to uniform low survival across all clones. Each bar and point represents the mean of three phototron experiments per given clone. Error bars represent ± 1 STD. Letters represent statistically significant differences between clones. Variable UV tolerance is often observed across species of <i>Daphnia</i> but has not been emphasized within clone lines to this degree.</p

The Survival Probabilities of the Diel-Only Treatment.

<p>The Survival Probabilities of the Diel-Only Treatment.</p

Emission spectra.

<p>The emission spectra for the lamp system used to induce DNA damage (left, UV-B Damage) and to photoreactivate damage after induction (right, Repair). This lamp design has been used in many laboratory-based UV studies of freshwater species and has been found to be highly applicable and comparable to what is observed in natural systems (e.g. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159628#pone.0159628.ref015" target="_blank">15</a>] and its references).</p

D. pulex.

<p><i>D</i>. <i>pulex</i> were exposed to ethylene blue for 15 min, rinsed thoroughly, and imaged using a Maximum Intensity Projection Z Plane Stack (10x, Leica SP5 Scanning Laser Confocal Microscope). The intensity image presented here was used as proof of concept during the characterization of ethylene blue.</p

Synthetic route for the preparation of fluorescently labeled vitamin D₃.

<p>The carbodiimidazole (CDI) coupling of vitamin D₃ and the fluorescent dye linker.</p

D. pulex.

<p><i>D</i>. <i>pulex</i> were exposed to ethylene blue for 15 min, rinsed thoroughly, and imaged using a Maximum Intensity Projection Z Plane Stack (10x, Leica SP5 Scanning Laser Confocal Microscope). The intensity image presented here was used as proof of concept during the characterization of ethylene blue.</p

UV-Stressed <i>Daphnia pulex</i> Increase Fitness through Uptake of Vitamin D₃

<div><p>Ultraviolet radiation is known to be highly variable in aquatic ecosystems. It has been suggested that UV-exposed organisms may demonstrate enough phenotypic plasticity to maintain the relative fitness of natural populations. Our long-term objective is to determine the potential photoprotective effect of vitamin D₃ on <i>Daphnia pulex</i> exposed to acute or chronic UV radiation. Herein we report our initial findings in this endeavor. <i>D</i>. <i>pulex</i> survival and reproduction (fitness) was monitored for 5 d as a proof of concept study. Significantly higher fitness was observed in the <i>D</i>. <i>pulex</i> with D₃ than those without (most extreme effects observed were 0% survival in the absence of D₃ and 100% with 10 ppm D₃). Vitamin D₃ was isolated from the culture media, the algal food (<i>Pseudokirchneriella</i>), and the <i>D</i>. <i>pulex</i> and quantified using high performance liquid chromatography (HPLC). Vitamin D₃ was fluorescently labeled using a phenothiazinium dye and added to cultures of <i>D</i>. <i>pulex</i>. Images demonstrating the uptake of D₃ into the tissues and carapace of the <i>D</i>. <i>pulex</i> were acquired. Our initial findings suggest a positive role for D₃ in ecosystems as both UV-stressed algae and <i>Daphnia</i> sequester D₃, and <i>D</i>. <i>pulex</i> demonstrate increased fitness in the presence of D₃.</p></div