TY - JOUR A1 - Sperfeld, Erik A1 - Wacker, Alexander T1 - Maternal diet of Daphnia magna affects offspring growth responses to supplementation with particular polyunsaturated fatty acids JF - Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica N2 - Previous studies examining the effects of food quality on zooplankton often controlled for maternal effects of resource provisioning using standardized maternal diets. However, varying nutritional history of mothers may change resource provisioning to their progeny, especially regarding polyunsaturated fatty acids (PUFAs), which may change the interpretation of previously observed fitness responses of offspring. To assess PUFA-mediated maternal provisioning effects on offspring, we raised females of the cladoceran Daphnia magna on diets differing considerably in PUFA composition and raised their offspring on a PUFA-lacking diet supplemented with the omega 3 PUFAs alpha-linolenic acid (ALA) and/or eicosapentaenoic acid (EPA). The mass-specific growth responses of offspring to their own diets were affected by the maternal diet regime, probably due to varying maternal PUFA provisioning. A low maternal provisioning of EPA or ALA was sufficient to prevent growth limitation of offspring by these PUFAs until reaching maturity. A comparison with results of published ALA and EPA supplementation experiments suggests that the previously observed limitation effects depended on the usage of a single algae genus as maternal diet. Therefore, we suggest that maternal diets should be deliberately varied in future studies assessing ecological relevant food quality effects on zooplankton, especially regarding PUFAs. KW - Food quality KW - Maternal effects KW - Nutritional ecology KW - Resource provisioning KW - Zooplankton Y1 - 2015 U6 - https://doi.org/10.1007/s10750-015-2244-y SN - 0018-8158 SN - 1573-5117 VL - 755 IS - 1 SP - 267 EP - 282 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Lukas, Marcus A1 - Wacker, Alexander T1 - Daphnia's dilemma: adjustment of carbon budgets in the face of food and cholesterol limitation JF - The journal of experimental biology N2 - We studied the carbon (C) metabolism in Daphnia when the amount of C (food quantity) and/or the content of biochemical nutrients (food quality) was limiting. Growth performances and C budgets of Daphnia magna (assimilation, faeces egestion, excretion and respiration measured by [C-14]-tracing) were analysed when animals were raised on different food quantities and concentrations of cholesterol, an essential biochemical food compound. Cholesterol is of special interest because it not only acts as limiting nutrient but also contributes to the overall C pool of the animals. As the tissue cholesterol concentration in Daphnia is quite low, we hypothesized the selective exclusion of cholesterol from C budgeting and tested this using radiolabelled cholesterol. Somatic growth rates of D. magna were highest at high quantity and quality and were reduced to a moderate value if either the food quantity or the cholesterol concentration was low. Growth was lowest at low food quantity and quality. The measurements of C budgets revealed high regulative response to low food quality at high food quantity only. Here, low dietary cholesterol caused bulk C assimilation efficiency (AE) to decrease and assimilated (excess) C to be increasingly respired. Additionally, Daphnia enhanced efficient adjustment of C budgets when facing cholesterol limitation by (1) increasing the AE of the cholesterol itself and (2) not changing cholesterol respiration, which was still not detectable. In contrast, at low food quantity, Daphnia is unable to adjust for low food quality, emphasizing that food limitation could overrule food quality effects. KW - Biochemical limitation KW - Carbon budgets KW - Zooplankton KW - Carbon pathway KW - Food quality KW - Food quantity Y1 - 2014 U6 - https://doi.org/10.1242/jeb.094151 SN - 0022-0949 SN - 1477-9145 VL - 217 IS - 7 SP - 1079 EP - 1086 PB - Company of Biologists Limited CY - Cambridge ER - TY - JOUR A1 - Martin-Creuzburg, Dominik A1 - Oexle, Sarah A1 - Wacker, Alexander T1 - Thresholds for sterol-limited growth of Daphnia magna: A comparative approach using 10 different sterols JF - Journal of chemical ecology N2 - Arthropods are incapable of synthesizing sterols de novo and thus require a dietary source to cover their physiological demands. The most prominent sterol in animal tissues is cholesterol, which is an indispensable structural component of cell membranes and serves as precursor for steroid hormones. Instead of cholesterol, plants and algae contain a variety of different phytosterols. Consequently, herbivorous arthropods have to metabolize dietary phytosterols to cholesterol to meet their requirements for growth and reproduction. Here, we investigated sterol-limited growth responses of the freshwater herbivore Daphnia magna by supplementing a sterol-free diet with increasing amounts of 10 different phytosterols and comparing thresholds for sterol-limited growth. In addition, we analyzed the sterol composition of D. magna to explore sterol metabolic constraints and bioconversion capacities. We show that dietary phytosterols strongly differ in their potential to support somatic growth of D. magna. The dietary threshold concentrations obtained by supplementing the different sterols cover a wide range (3.5-34.4 mu g mg C-1) and encompass the one for cholesterol (8.9 mu g mg C-1), indicating that certain phytosterols are more efficient in supporting somatic growth than cholesterol (e.g., fucosterol, brassicasterol) while others are less efficient (e.g., dihydrocholesterol, lathosterol). The dietary sterol concentration gradients revealed that the poor quality of particular sterols can be alleviated partially by increasing dietary concentrations, and that qualitative differences among sterols are most pronounced at low to moderate dietary concentrations. We infer that the dietary sterol composition has to be considered in zooplankton nutritional ecology to accurately assess potential sterol limitations under field conditions. KW - Cholesterol KW - Daphnia KW - Food quality KW - Nutrition KW - Phytosterols KW - Sterols Y1 - 2014 U6 - https://doi.org/10.1007/s10886-014-0486-1 SN - 0098-0331 SN - 1573-1561 VL - 40 IS - 9 SP - 1039 EP - 1050 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Spijkerman, Elly A1 - Wacker, Alexander T1 - Interactions between P-limitation and different C conditions on the fatty acid composition of an extremophile microalga JF - Extremophiles : life under extreme conditions N2 - The extremophilic microalga Chlamydomonas acidophila inhabits very acidic waters (pH 2-3.5), where its growth is often limited by phosphorus (P) or colimited by P and inorganic carbon (CO(2)). Because this alga is a major food source for predators in acidic habitats, we studied its fatty acid content, which reflects their quality as food, grown under a combination of P-limited and different carbon conditions (either mixotrophically with light + glucose or at high or low CO(2), both without glucose). The fatty acid composition largely depended on the cellular P content: stringent P-limited cells had a higher total fatty acid concentration and had a lower percentage of polyunsaturated fatty acids. An additional limitation for CO(2) inhibited this decrease, especially reflected in enhanced concentrations of 18:3(9,12,15) and 16:4(3,7,10,13), resulting in cells relatively rich in polyunsaturated fatty acids under colimiting growth conditions. The percentage of polyunsaturated to total fatty acid content was positively related with maximum photosynthesis under all conditions applied. The two factors, P and CO(2), thus interact in their effect on the fatty acid composition in C. acidophila, and colimited cells P-limited algae can be considered a superior food source for herbivores because of the high total fatty acid content and relative richness in polyunsaturated fatty acids. KW - Acidophilic algae KW - Cellular P quota KW - Chlamydomonas acidophila KW - Chlorophyceae KW - Colimitation KW - CO(2) KW - Fatty acid composition KW - Food quality KW - Glucose KW - Mixotrophy KW - Photosynthesis KW - Phytoplankton KW - Phosphorus limitation Y1 - 2011 U6 - https://doi.org/10.1007/s00792-011-0390-3 SN - 1431-0651 VL - 15 IS - 5 SP - 597 EP - 609 PB - Springer CY - Tokyo ER - TY - JOUR A1 - Martin-Creuzburg, Dominik A1 - Wacker, Alexander A1 - Ziese, Christine A1 - Kainz, Martin J. T1 - Dietary lipid quality affects temperature-mediated reaction norms of a freshwater key herbivore JF - Oecologia N2 - Temperature-mediated plasticity in life history traits strongly affects the capability of ectotherms to cope with changing environmental temperatures. We hypothesised that temperature-mediated reaction norms of ectotherms are constrained by the availability of essential dietary lipids, i.e. polyunsaturated fatty acids (PUFA) and sterols, as these lipids are involved in the homeoviscous adaptation of biological membranes to changing temperatures. A life history experiment was conducted in which the freshwater herbivore Daphnia magna was raised at four different temperatures (10, 15, 20, 25A degrees C) with food sources differing in their PUFA and sterol composition. Somatic growth rates increased significantly with increasing temperature, but differences among food sources were obtained only at 10A degrees C at which animals grew better on PUFA-rich diets than on PUFA-deficient diets. PUFA-rich food sources resulted in significantly higher population growth rates at 10A degrees C than PUFA-deficient food, and the optimum temperature for offspring production was clearly shifted towards colder temperatures with an increased availability of dietary PUFA. Supplementation of PUFA-deficient food with single PUFA enabled the production of viable offspring and significantly increased population growth rates at 10A degrees C, indicating that dietary PUFA are crucial for the acclimation to cold temperatures. In contrast, cumulative numbers of viable offspring increased significantly upon cholesterol supplementation at 25A degrees C and the optimum temperature for offspring production was shifted towards warmer temperatures, implying that sterol requirements increase with temperature. In conclusion, essential dietary lipids significantly affect temperature-mediated reaction norms of ectotherms and thus temperature-mediated plasticity in life history traits is subject to strong food quality constraints. KW - Daphnia KW - Food quality KW - Phenotypic plasticity KW - Polyunsaturated fatty acids KW - Sterols Y1 - 2012 U6 - https://doi.org/10.1007/s00442-011-2155-1 SN - 0029-8549 VL - 168 IS - 4 SP - 901 EP - 912 PB - Springer CY - New York ER -