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Odor-regulated oviposition behavior in an ecological specialist
Raquel Álvarez-Ocaña1, Michael P Shahandeh1, Vijayaditya Ray2
1Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, CH-1015, Lausanne, Switzerland.
Nature Communications
|May 26, 2023
Summary
Fruit fly evolution shows olfaction guides egg-laying. Specialized fruit flies rely on specific odors, detected by the Ionotropic receptor 75b (Ir75b), for successful reproduction in new environments.
Area of Science:
- Animal behavior evolution
- Insect sensory biology
- Olfactory neuroscience
Background:
- Colonizing new ecological niches often requires behavioral adaptations for reproductive success.
- Drosophila sechellia, a fruit fly species, shows extreme specialization for Morinda citrifolia (noni) fruit, laying most eggs exclusively on this substrate.
- This species-specific preference is not explained by visual, textural, or social cues.
Purpose of the Study:
- To investigate the evolutionary and sensory basis of oviposition behavior in Drosophila sechellia.
- To determine the role of olfaction in the specialized noni fruit preference of D. sechellia.
- To identify specific olfactory components and receptors involved in noni-guided egg-laying.
Main Methods:
- Comparative behavioral assays of egg-laying preference in D. sechellia and D. melanogaster.
- Sensory deprivation experiments (loss of olfactory input) in both species.
- Gas chromatography-mass spectrometry (GC-MS) to identify noni fruit volatile compounds.
- Odor-evoked calcium imaging and electrophysiology to study olfactory responses.
- Receptor exchange experiments by genetically modifying Ir75b in D. melanogaster.
Main Results:
- Loss of olfactory input significantly reduced egg-laying in D. sechellia, indicating olfaction gates gustatory-driven noni preference.
- Noni fruit odors are detected by redundant olfactory pathways.
- Hexanoic acid was identified as a key odorant, and its cognate receptor, Ionotropic receptor 75b (Ir75b), was found to play a crucial role in odor-evoked oviposition.
- Receptor exchange experiments demonstrated that altered odor tuning of Ir75b causally contributes to the evolution of D. sechellia's specialized oviposition behavior.
Conclusions:
- Olfaction is the primary sensory modality driving the specialized noni fruit oviposition preference in Drosophila sechellia.
- Hexanoic acid and the Ir75b receptor are key components in the evolution of this behavior.
- Changes in olfactory receptor tuning can drive the adaptation of reproductive behaviors to novel ecological niches.
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