December 7, 2012
Hawk Moths Learn To Use Brain To Find Alternative Food Sources
Brett Smith for redOrbit.com - Your Universe Online
When their favorite food isn´t readily available, hawk moths are able to switch to a different olfactory ℠channel´ in their brain, enabling them to learn how to find alternative nectar sources, according to a new report in the journal Science Express.
The two olfactory channels allow the moths to survive in a changing floral environment and the researchers are expecting that better understanding of this mechanism will inform future studies on olfactory systems in humans, who have a similar neurological pathway.
The scientists at the University of Washington and University of Arizona began their study by collecting scent samples from flowers that were regularly visited by hawk moths in the wild. The researchers also collected scents from closely related flowers that hawk moths did not seem to prefer.
"This study is based on observations of wild animals in the real world. We think it's critically important to know what the animals do in the natural world, not just what they do in the lab," explained study co-author John Hildebrand, from the Department of Neuroscience at the University of Arizona. "It's not enough for us to show what the animal can do under artificial conditions — we want to know the basis for what the animal does when it's living out in the world."
Analyzing the scents in the lab, the scientists found most of the favored flowers shared an extremely similar chemical profile even though many of them evolved along timelines that differed by millions of years.
Using electronic probes that were attached to the moths' scent-detecting antennae, they were able to identify the active olfactory channel when the moths were exposed to trigger chemicals from the preferred set of flowers.
The researchers found that the moths ℠cataloged´ those flower scents by the exact same method in the olfactory lobe. They also failed to detect activity in any particular neural pathways when the moths were exposed to non-preferred flower scents.
To expand on these findings, both types of scents were offered to "naive" moths, which were raised without ever being exposed to real flowers.
"What we found was really amazing. A naive moth will go mainly to flowers that had been attractive to moths in the wild, from flower to flower as if they were the same flower, responding in the very same manner," lead author Jeffrey Riffell, a UW assistant professor of biology, said in a statement. "These favored flowers look very different from each other, it's the odor that's driving the behavior."
In their observations, the scientists also noted that while the moths visited preferred flowers, they also took to other flowers, like the agave, which they used to train the insects. In the lab, they taught the moths to associate agave with a sugar-water reward. During the training process, the research team took additional recordings of the moths´ olfactory pathways.
They were able to identify a neural modulator, octopamine, which is released in the moths´ brains as the signal to retain information on an important food resource. The scientists also found that these learned alternate food sources don´t act as replacements for the moth's innate preferences.