Grooming Helps Insects Keep Their Senses Sharpened

Feb. 4, 2013 — Like a self-absorbed teenager, insects spend a lot of time grooming. In a study that delves into the mechanisms behind this common function, North Carolina State University researchers show that insect grooming — specifically, antennal cleaning — removes both environmental pollutants and chemicals produced by the insects themselves.

These are electron microscopy images of ungroomed, groomed and hexane washed male cockroach antennae. Grooming keeps olfactory senses keen. (Credit: NC State University)

The findings, published online this week in Proceedings of the National Academy of Sciences, show that grooming helps insects maintain acute olfactory senses that are responsible for a host of functions, including finding food, sensing danger and even locating a suitable mate.

The findings could also explain why certain types of insecticides work more effectively than others.

Insects groom themselves incessantly, so NC State entomologist Coby Schal and post-doctoral researchers Katalin Boroczky and Ayako Wada-Katsumata wanted to explore the functions of this behavior.

They devised a simple set of experiments to figure out what sort of material insects were cleaning off their antennae, where this material was coming from, and the differences between how groomed and ungroomed antennae functioned. Schal likened the straightforwardness of some of the experiments to something you’d see in a well-equipped high-school science lab.

The researchers compared cleaned antennae of American cockroaches with antennae that were experimentally prevented from being cleaned. They found that grooming cleaned microscopic pores on the antennae that serve as conduits through which chemicals travel to reach sensory receptors for olfaction. Cockroaches clean their antennae by using forelegs to place the antennae in their mouths; they then methodically clean every segment of the antenna from base to tip.

The researchers found that both volatile and non-volatile chemicals accumulated on the ungroomed antennae of cockroaches, but most surprising was the accumulation of a great deal of cuticular hydrocarbons — fatty, candlewax-like substances secreted by the roaches to protect them against water loss.

“It is intuitive that insects remove foreign substances from their antennae, but it’s not necessarily intuitive that they groom to remove their ‘own’ substances,” Schal says.

The researchers also tested groomed and ungroomed cockroach antennae to gauge how well roaches picked up the scent of a known sex pheromone compound, as well as other odorants. Clean antennae responded to these signals much more readily than ungroomed antennae.

The researchers then put carpenter ants, houseflies and German cockroaches to many of the same tests. Although they groom a bit differently than cockroaches — flies and ants seem to rub their legs over their antennae to remove particulates, with ants then ingesting the material off their legs — the tests showed that these insects also accumulated more cuticular hydrocarbons when antennae went ungroomed.

“The evidence is strong: Grooming is necessary to keep these foreign and native substances at a particular level,” Schal says. “Leaving antennae dirty essentially blinds insects to their environment.”

Schal adds that there could be pest-control implications to the findings. An insecticide mist or dust that settles on a cockroach’s antennae, for instance, should be ingested by the roach rather quickly due to constant grooming. That method of insecticide delivery could be more effective than relying on residual insecticides to penetrate the thick cuticle, for instance.

Finally, Schal says the study can also be used as a caution to other researchers who use insects in experiments. Gluing shut an insect’s mouth to prevent it from feeding, for example, also prevents the insect from grooming its antennae. Experimental results could be skewed as a result of this sensory deprivation, Schal suggests.

Dale Batchelor, a researcher in NC State’s Analytical Instrumentation Facility, co-authored the paper, as did Marianna Zhukovskaya at the Russian Academy of Sciences. The research was supported by the National Institute of Food and Agriculture, the U.S. Department of Agriculture, the National Science Foundation and the Blanton J. Whitmire Endowment at NC State.


Story Source:

The above story is reprinted from materials provided byNorth Carolina State University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.


Journal Reference:

  1. Katalin Böröczky, Ayako Wada-Katsumata, Dale Batchelor, Marianna Zhukovskaya, and Coby Schal.Insects groom their antennae to enhance olfactory acuityPNAS, February 4, 2013 DOI:10.1073/pnas.1212466110
North Carolina State University (2013, February 4). Grooming helps insects keep their senses sharpened. ScienceDaily. Retrieved February 5, 2013, from http://www.sciencedaily.com/releases/2013/02/130204153603.htm
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Smelling a Skunk After a Cold: Brain Changes After a Stuffed Nose Protect the Sense of Smell

ScienceDaily (Aug. 12, 2012) — Has a summer cold or mold allergy stuffed up your nose and dampened your sense of smell? We take it for granted that once our nostrils clear, our sniffers will dependably rebound and alert us to a lurking neighborhood skunk or a caramel corn shop ahead.

(Credit: http://www.sheridanent.com/)


 

That dependability is no accident. It turns out the brain is working overtime behind the scenes to make sure the sense of smell is just as sharp after the nose recovers.

A new Northwestern Medicine study shows that after the human nose is experimentally blocked for one week, brain activity rapidly changes in olfactory brain regions. This change suggests the brain is compensating for the interruption of this vital sense. The brain activity returns to a normal pattern shortly after free breathing has been restored.

Previous research in animals has suggested that the olfactory system is resistant to perceptual changes following odor deprivation. This new paper focuses on humans to show how that’s possible. The study is published in the journal Nature Neuroscience.

“You need ongoing sensory input in order for your brain to update smell information,” said Keng Nei Wu, the lead author of the paper and a graduate student in neuroscience at Northwestern University Feinberg School of Medicine. “When your nostrils are blocked up, your brain tries to adjust to the lack of information so the system doesn’t break down. The brain compensates for the lack of information so when you get your sense of smell back, it will be in good working order.”

For the study, Wu completely blocked the nostrils of 14 participants for a week while they lived in a special low-odor hospital room. At night, participants were allowed to breathe normally while they slept in the room.

After the smell deprivation, researchers found an increase in activity in the orbital frontal cortex and a decrease of activity in the piriform cortex, two regions related to the sense of smell.

“These changes in the brain are instrumental in maintaining the way we smell things even after seven days of no smell,” Wu said.

When unrestricted breathing was restored, people were immediately able to perceive odors. A week after the deprivation experience, the brain’s response to odors had returned to pre-experimental levels, indicating that deprivation-caused changes are rapidly reversed.

Such a rapid reversal is quite different from other sensory systems, such as sight, which typically have longer-lasting effects due to deprivation. The olfactory system is more agile, Wu suggested, because smell deprivation due to viral infection or allergies is common.

This study also has clinical significance relating to upper respiratory infection and sinusitis, especially when such problems become chronic, at which point ongoing deprivation could cause more profound and lasting changes, Wu noted.

“It also implies that deprivation has a significant impact on the brain, rather than on the nose itself,” Wu said. “More knowledge about how the system reacts to short-term deprivation may provide new insights into how to deal with this problem in a chronic context.”

Other Northwestern authors include Bruce K. Tan, James D. Howard, David B. Conley and Jay A. Gottfried, the senior author.

 

Story Source:

The above story is reprinted from materials provided byNorthwestern University, via EurekAlert!, a service of AAAS.


Journal Reference:

  1. Keng Nei Wu, Bruce K Tan, James D Howard, David B Conley, Jay A Gottfried. Olfactory input is critical for sustaining odor quality codes in human orbitofrontal cortexNature Neuroscience, 2012; DOI: 10.1038/nn.3186
Citation:

Northwestern University (2012, August 12). Smelling a skunk after a cold: Brain changes after a stuffed nose protect the sense of smell.ScienceDaily. Retrieved August 14, 2012, from http://www.sciencedaily.com/releases/2012/08/120812151714.htm