title: Olfactory preference for egg laying on citrus substrates in Drosophila.
abstract: BACKGROUND
  Egg-laying animals, such as insects, ensure the survival of their offspring by depositing their eggs in favorable environments. To identify suitable oviposition sites, insects, such as the vinegar fly Drosophila melanogaster, assess a complex range of features. The fly selectively lays eggs in fermenting fruit. However, the precise cues and conditions that trigger oviposition remain unclear, including whether flies are also selective for the fruit substrate itself.
  
  
  RESULTS
  Here, we demonstrate that flies prefer Citrus fruits as oviposition substrate. Flies detect terpenes characteristic of these fruits via a single class of olfactory sensory neurons, expressing odorant receptor Or19a. These neurons are necessary and sufficient for selective oviposition. In addition, we find that the Citrus preference is an ancestral trait, presumably representing an adaptation toward fruits found within the native African habitat. Moreover, we show that endoparasitoid wasps that parasitize fly larvae are strongly repelled by the smell of Citrus, as well as by valencene, the primary ligand of Or19a. Finally, larvae kept in substrates enriched with valencene suffer a reduced risk of parasitism.
  
  
  CONCLUSIONS
  Our results demonstrate that a single dedicated olfactory pathway determines oviposition fruit substrate choice. Moreover, our work suggests that the fly's fruit preference--reflected in the functional properties of the identified neuron population--stem from a need to escape parasitism from endoparasitoid wasps.
authors: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany.
authors: Hany K M
authors: HK
authors: Dweck
authors: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany.
authors: Shimaa A M
authors: SA
authors: Ebrahim
authors: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany.
authors: Sophie
authors: S
authors: Kromann
authors: International Institute of Tropical Agriculture, PMB 5320, Oyo Road, 200001 Ibadan, Nigeria.
authors: Deni
authors: D
authors: Bown
authors: International Institute of Tropical Agriculture, PMB 5320, Oyo Road, 200001 Ibadan, Nigeria.
authors: Ylva
authors: Y
authors: Hillbur
authors: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany.
authors: Silke
authors: S
authors: Sachse
authors: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany. Electronic address: hansson@ice.mpg.de.
authors: Bill S
authors: BS
authors: Hansson
authors: Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany. Electronic address: marcus.stensmyr@biol.lu.se.
authors: Marcus C
authors: MC
authors: Stensmyr
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002957:Citrus / Q000737:chemistry*; D053138:Cyclohexenes / Q000032:analysis / Q000494:pharmacology; D029721:Drosophila Proteins / Q000502:physiology; D004331:Drosophila melanogaster / Q000469:parasitology / Q000502:physiology*; D006790:Host-Parasite Interactions; D000077222:Limonene; D010058:Oviposition; D018035:Receptors, Odorant / Q000502:physiology; D012717:Sesquiterpenes / Q000032:analysis / Q000494:pharmacology; D013729:Terpenes / Q000032:analysis / Q000494:pharmacology; D014863:Wasps / Q000502:physiology
chemical_list: D053138:Cyclohexenes; D029721:Drosophila Proteins; D018035:Receptors, Odorant; D012717:Sesquiterpenes; D013729:Terpenes; C506706:valencene; D000077222:Limonene