A female hawkmoth (Manduca sexta) locates sources of nectar and decides where to lay its eggs via olfactory cues. Researchers reported last week (February 27) in Cell Reports that a different area in the olfactory center of the moth’s brain is involved in processing egg-laying from feeding cues.
“By using diagnostic odors to stimulate each single moth in our test series, we established a functional atlas of the antennal lobe,” says first author Sonja Bisch-Knaden, a neuroethologist at the Max Planck Institute for Chemical Ecology, in a press release. “We were able to address two-thirds of the visible olfactory glomeruli in each animal and then study the moths’ responses to a large set of odors.”
The researchers first analyzed the concentration of calcium ions in nerve cells while they presented moths with different odors to map precisely which glomeruli—spherical structures in the olfactory center where synapses are located—were activated by each stimulus. They then placed moths in a wind tunnel and observed their behavioral responses to different odors. Certain odors prompted the moths to unroll their proboscises and attempt to drink nectar or bend their abdomens to try to lay eggs.
The researchers were surprised by their results. “We had not expected that a single chemical compound could be as attractive to hungry moths in search for food as would be a complex flower bouquet,” says Bisch-Knaden. “It was pretty fascinating that a few odors also caused virgin females to lay their eggs on the filter paper, which obviously had not been fertilized.”
S. Bisch-Knaden et al., “Spatial representation of feeding and oviposition odors in the brain of a hawkmoth,” Cell Reports, doi:10.1016/j.celrep.2018.01.082, 2018.