@article{MartinCreuzburgMassierWacker2018,
  author    = {Martin-Creuzburg, Dominik and Massier, Tamara and Wacker, Alexander},
  title     = {Sex-Specific differences in essential lipid requirements of Daphnia magna},
  series = {Frontiers in Ecology and Evolution},
  volume    = {6},
  journal   = {Frontiers in Ecology and Evolution},
  publisher = {Frontiers Research Foundation},
  address   = {Lausanne},
  issn      = {2296-701X},
  doi       = {10.3389/fevo.2018.00089},
  pages     = {14},
  year      = {2018},
  abstract  = {Sex-specific differences in nutritional requirements may crucially influence the performances of the sexes, which may have implications for sexual reproduction and thus is of great ecological and evolutionary interest. In the freshwater model species Daphnia magna, essential lipid requirements have been extensively studied. Dietary deficiencies in sterols and polyunsaturated fatty acids (PUFA) have been shown to constrain somatic growth and parthenogenetic reproduction of female Daphnia. In contrast, nutrient requirements of male Daphnia have not been studied yet. Supplementation experiments were conducted to investigate differences in sterol (cholesterol) and PUFA (eicosapentaenoic acid, EPA) requirements between female and male D. magna. Thresholds for sterol-limited juvenile growth were higher in females than in males, suggesting that females are more susceptible to dietary sterol deficiencies than males. Sex-specific differences in maximum somatic growth rates were evident primarily in the presence of dietary EPA; females could not exploit their generally higher growth potential in the absence of dietary PUFA. However, the thresholds for EPA-limited growth did not differ between sexes, suggesting that both sexes have similar dietary EPA requirements during juvenile growth. During a life history experiment, the gain in body dry mass was higher in females than in males, irrespective of food treatment. In both sexes, the gain in body dry mass increased significantly upon EPA supplementation, indicating that both sexes benefited from dietary EPA supply also later in life. However, the positive effects of EPA supplementation were most pronounced for female reproduction-related traits (i.e., clutch sizes, egg dry masses, and total dry mass investment in reproduction). The high maternal investment in reproduction resulted in a depletion of nutrients in female somata. In contrast, the comparatively low paternal investment in reproduction allowed for the accumulation of nutrients in male somata. We conclude that males are generally less susceptible to dietary nutrient deficiencies than females, because they can rely more on internal body stores. Our data suggest that the performances of the sexes are differentially influenced by lipid-mediated food quality, which may have consequences for sexual reproduction and thus the production of resting eggs and the maintenance of Daphnia populations.},
  language  = {en}
}
@article{PiephoMartinCreuzburgWacker2012,
  author    = {Piepho, Maike and Martin-Creuzburg, Dominik and Wacker, Alexander},
  title     = {Phytoplankton sterol contents vary with temperature, phosphorus and silicate supply a study on three freshwater species},
  series = {European journal of phycology},
  volume    = {47},
  journal   = {European journal of phycology},
  number    = {2},
  publisher = {Routledge, Taylor \& Francis Group},
  address   = {Abingdon},
  issn      = {0967-0262},
  doi       = {10.1080/09670262.2012.665484},
  pages     = {138 -- 145},
  year      = {2012},
  abstract  = {The understanding of environmentally induced changes in the biochemical composition of phytoplankton species is of great importance in both physiological studies and ecological food web research. In extensive laboratory experiments we tested the influence of two different temperatures (10 degrees C and 25 degrees C) and a phosphorus supply gradient on the sterol concentrations of the three freshwater phytoplankton species Scenedesmus quadricauda, Cryptomonas ovata and Cyclotella meneghiniana. The diatom C. meneghiniana was additionally exposed to a silicate gradient. In two separate experiments we analysed (1) possible interactive effects of temperature and phosphorus supply and (2) the effect of four phosphorus levels and three silicate levels on algal sterol concentrations. We observed that sterol concentrations were higher at 25 degrees C than at 10 degrees C in S. quadricauda and C. meneghiniana, but were not affected by temperature in C. ovata. Interactive effects of temperature and phosphorus supply on sterol concentrations were found in C. meneghiniana. This presumably was due to the bioconversion of one sterol (24-methylenecholesterol) into another (22-dihydrobrassicasterol). Increasing phosphorus supply resulted in species-specific effects on sterol concentrations, viz. an optimum curve response in S. quadricauda, a saturation curve response in C. meneghiniana and no change in sterol concentration in C. ovata. Effects of silicate supply on the sterols of C. meneghiniana equalled the effects of phosphorus supply. Albeit we did not observe a general trend in the three phytoplankton species tested, we conclude that sterol concentrations of phytoplankton are strongly affected by temperature and nutrient supply. Interactive effects point out the importance of taking into account more than just one environmental factor when assessing the effects of environmentally induced changes on phytoplankton sterol concentrations.},
  language  = {en}
}
@article{SchaelickeSobischMartinCreuzburgetal.2019,
  author    = {Sch{\"a}licke, Svenja and Sobisch, Lydia-Yasmin and Martin-Creuzburg, Dominik and Wacker, Alexander},
  title     = {Food quantity-quality co-limitation},
  series = {Freshwater biology},
  volume    = {64},
  journal   = {Freshwater biology},
  number    = {5},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0046-5070},
  doi       = {10.1111/fwb.13272},
  pages     = {903 -- 912},
  year      = {2019},
  abstract  = {Food quantity and quality are highly variable in natural systems. Therefore, their interplay and the associated effects on consumer population growth are important for predator-prey interactions and community dynamics. Experiments in which consumers were exposed to elemental nutrient limitations along food quantity gradients suggest that food quality effects on consumer performance are relevant only at high food quantities. However, elemental nutrients act differently on physiological processes than biochemical nutrients. So far, the interactive effects of food quantity and biochemical compounds on consumer performance have been insufficiently studied. We studied interactive effects of food quantity and biochemical food quality on population growth, including fecundity and survival, of the freshwater rotifer Brachionus calyciflorus. We hypothesised that these life history traits are differently affected by the availability of biochemical nutrients and that food quality effects gain importance with increasing food quantity. In a first experiment, we established food quantity and quality gradients by providing rotifers with different concentrations of a low-quality food, the sterol-free cyanobacterium Synechococcus elongatus, supplemented with increasing amounts of cholesterol. In a second experiment, food quantity and quality gradients were established by providing different proportions of two prey species differing in biochemical food quality, i.e. S.elongatus and the lipid-rich alga Nannochloropsis limnetica, at different total food concentrations. We found that the effects of cholesterol supplementation on population growth increased with increasing food quantity. This interactive effect on population growth was mainly due to food quality effects on fecundity, as effects on survival remained constant along the food quantity gradient. In contrast, when feeding on the mixed algal diet, the food quality effect associated with increasing the proportion of the high-quality alga did not change along the food quantity gradient. The data on survival and fecundity demonstrate the missing interactive effect of food quantity and quality on population growth, as both traits were oppositely affected. Survival was affected by food quality primarily at low food quantity, whereas food quality effects on fecundity were stronger at high food quantity. Our results highlight the significance of essential biochemicals in mediating the interactive effects of food quantity and quality on population growth. The interplay between food quantity and biochemical food quality limitation seems to influence resource allocation patterns in order to optimise survival or reproduction, which may strongly affect population dynamics in variable environments. As opposed to exploring the function of a single nutrient via supplementation, using algae mixtures allowed us to assess food quality effects on consumer performance in a more natural context by taking potential interactive effects of multiple co-limiting nutrients into account.},
  language  = {en}
}