Dataset Information

UV-Stressed Daphnia pulex Increase Fitness through Uptake of Vitamin D3.

ABSTRACT: 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 Daphnia pulex exposed to acute or chronic UV radiation. Herein we report our initial findings in this endeavor. D. pulex survival and reproduction (fitness) was monitored for 5 d as a proof of concept study. Significantly higher fitness was observed in the D. pulex 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 (Pseudokirchneriella), and the D. pulex and quantified using high performance liquid chromatography (HPLC). Vitamin D3 was fluorescently labeled using a phenothiazinium dye and added to cultures of D. pulex. Images demonstrating the uptake of D3 into the tissues and carapace of the D. pulex were acquired. Our initial findings suggest a positive role for D3 in ecosystems as both UV-stressed algae and Daphnia sequester D3, and D. pulex demonstrate increased fitness in the presence of D3.

SUBMITTER: Connelly SJ

PROVIDER: S-EPMC4492615 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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UV-Stressed Daphnia pulex Increase Fitness through Uptake of Vitamin D3.

Connelly Sandra J SJ Walling Kelly K Wilbert Steven A SA Catlin Diane M DM Monaghan Cailin E CE Hlynchuk Sofiya S Meehl Pamela G PG Resch Lauren N LN Carrera J Valerie JV Bowles Stephanie M SM Clark Michael D MD Tan Loraine T LT Cody Jeremy A JA

PloS one 20150706 7

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 Daphnia pulex exposed to acute or chronic UV radiation. Herein we report our initial findings in this endeavor. D. pulex survival and reproduction (fitness) was monitored for 5 d a ...[more]

PMID: 26147286

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Project description:BackgroundAcidity exerts a determining influence on the composition and diversity of freshwater faunas. While the physiological implications of freshwater acidification have been intensively studied in teleost fish and crayfish, much less is known about the acid-stress physiology of ecologically important groups such as cladoceran zooplankton. This study analyzed the extracellular acid-base state and CO2 partial pressure (P(CO2)), circulation and ventilation, as well as the respiration rate of Daphnia pulex acclimated to acidic (pH 5.5 and 6.0) and circumneutral (pH 7.8) conditions.ResultsD. pulex had a remarkably high extracellular pH of 8.33 and extracellular P(CO2) of 0.56 kPa under normal ambient conditions (pH 7.8 and normocapnia). The hemolymph had a high bicarbonate concentration of 20.9 mM and a total buffer value of 51.5 meq L(-1) pH(-1). Bicarbonate covered 93% of the total buffer value. Acidic conditions induced a slight acidosis (DeltapH = 0.16-0.23), a 30-65% bicarbonate loss, and elevated systemic activities (tachycardia, hyperventilation, hypermetabolism). pH 6.0 animals partly compensated the bicarbonate loss by increasing the non-bicarbonate buffer value from 2.0 to 5.1 meq L(-1) pH(-1). The extracellular P(CO2) of pH 5.5 animals was significantly reduced to 0.33 kPa, and these animals showed the highest tolerance to a short-term exposure to severe acid stress.ConclusionChronic exposure to acidic conditions had a pervasive impact on Daphnia's physiology including acid-base balance, extracellular PCO2, circulation and ventilation, and energy metabolism. Compensatory changes in extracellular non-bicarbonate buffering capacity and the improved tolerance to severe acid stress indicated the activation of defense mechanisms which may result from gene-expression mediated adjustments in hemolymph buffer proteins and in epithelial properties. Mechanistic analyses of the interdependence between extracellular acid-base balance and CO2 transport raised the question of whether a carbonic anhydrase (CA) is involved in the catalysis of the CO2-HCO3(-)-H(+) reaction, which led to the discovery of 31 CA-genes in the genome of D. pulex.

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UV-Stressed Daphnia pulex Increase Fitness through Uptake of Vitamin D3.

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UV-Stressed Daphnia pulex Increase Fitness through Uptake of Vitamin D3.

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