Macroglomeruli for fruit odors change blend preference in Drosophila

Area of Science:

• Neuroscience
• Olfactory system
• Animal behavior

Background:

• The link between olfactory processing and behavioral responses in Drosophila is not fully understood.
• Drosophila sechellia, a specialist species, overrepresents a specific olfactory sensillum (ab3) sensitive to hexanoate esters, found in its host fruit.
• This overrepresentation corresponds to an enlarged olfactory glomerulus (DM2).

Purpose of the Study:

• To investigate how alterations in olfactory circuitry influence odor preference in Drosophila.
• To determine the ecological significance of the ab3B neuron and its associated glomerulus in D. sechellia.

Main Methods:

• Comparative analysis of olfactory circuitry between Drosophila melanogaster and its sibling species.
• Identification of odorant tuning for the ab3B neuron.
• Behavioral experiments assessing odor preference in response to specific volatile compounds.

Main Results:

• The ab3B neuron in D. sechellia is tuned to 2-heptanone (HP), another volatile from its host fruit.
• Axons of the ab3B neuron project to a second enlarged glomerulus.
• Drosophila sechellia exhibits a reversed odor preference compared to D. melanogaster, showing attraction to high concentrations of key odor ligands, particularly blends.

Conclusions:

• Simple changes in olfactory sensillar abundance and glomerular size can significantly alter the olfactory code.
• These alterations can lead to substantial shifts in odor preference.
• Drosophila sechellia has adapted its olfactory system to align with its specific ecological niche.