@article{MartinCreuzburgOexleWacker2014,
  author    = {Martin-Creuzburg, Dominik and Oexle, Sarah and Wacker, Alexander},
  title     = {Thresholds for sterol-limited growth of Daphnia magna: A comparative approach using 10 different sterols},
  series = {Journal of chemical ecology},
  volume    = {40},
  journal   = {Journal of chemical ecology},
  number    = {9},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {0098-0331},
  doi       = {10.1007/s10886-014-0486-1},
  pages     = {1039 -- 1050},
  year      = {2014},
  abstract  = {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.},
  language  = {en}
}
@article{ScheinerSteinbachClassenetal.2014,
  author    = {Scheiner, Ricarda and Steinbach, Anne and Classen, Gerbera and Strudthoff, Nicole and Scholz, Henrike},
  title     = {Octopamine indirectly affects proboscis extension response habituation in Drosophila melanogaster by controlling sucrose responsiveness},
  series = {Journal of insect physiology},
  volume    = {69},
  journal   = {Journal of insect physiology},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0022-1910},
  doi       = {10.1016/j.jinsphys.2014.03.011},
  pages     = {107 -- 117},
  year      = {2014},
  abstract  = {Octopamine is an important neurotransmitter in insects with multiple functions. Here, we investigated the role of this amine in a simple form of learning (habituation) in the fruit fly Drosophila melanogaster. Specifically, we asked if octopamine is necessary for normal habituation of a proboscis extension response (PER) to different sucrose concentrations. In addition, we analyzed the relationship between responsiveness to sucrose solutions applied to the tarsus and habituation of the proboscis extension response in the same individual. The Tyramine-beta-hydroxylase (T beta h) mutant lacks the enzyme catalyzing the final step of octopamine synthesis. This mutant was significantly less responsive to sucrose than controls. The reduced responsiveness directly led to faster habituation. Systemic application of octopamine or induction of octopamine synthesis by T beta h expression in a cluster of octopaminergic neurons within the suboesophageal ganglion restored sucrose responsiveness and habituation of octopamine mutants to control level. Further analyses imply that the reduced sucrose responsiveness of T beta h mutants is related to a lower sucrose preference, probably due to a changed carbohydrate metabolism, since T beta h mutants survived significantly longer under starved conditions. These findings suggest a pivotal role for octopamine in regulating sucrose responsiveness in fruit flies. Further, octopamine indirectly influences non-associative learning and possibly associative appetitive learning by regulating the evaluation of the sweet component of a sucrose reward. (C) 2014 Elsevier Ltd. All rights reserved.},
  language  = {en}
}