Evening Geniuses
When you walk into your apartment late in the evening you might spot a couple of cockroaches scurrying around to find a dark hiding spot. From previous studies, the reasoning was that they are light sensitive and prefer to be out in the dark, so when you turn your lights on at night they favor to be somewhere dark and hidden. A new study at Vanderbilt University decided to look at the sensory systems instead of the visual systems of the cockroach species, Leucophaea madera, and see how well the cockroaches’ olfactory systems respond at different periods of the day.
Individual cockroaches were trained at different times of the 24 hour day/night period to associate with smells. For a cockroach, the olfactory sense is stronger than its vision. Cockroaches move by use of their antennae. The antennae produce small electrical charges in the presence of certain chemicals and they respond to odor stimuli. Cockroaches leave chemical trails in their feces that other cockroaches follow that lead to sources of food and water.
In this study there were three scents that were used as a standard for cockroaches. Cockroaches can associate and react well with these particular scents. The peppermint scent cockroaches disliked the most, sugar water is a scent that they prefer and vanilla is a scent that the cockroaches find appealing and like the most. Researchers observed how long these cockroaches could remember the smell over periods of the day.
When the results came in they discovered that in the morning, cockroaches are least active and incapable of forming a new memory. However, in the evening they are very active and can retain a memory for several days. Terry L. Page, a professor of biological science said:
“An interesting question is why the animal would not want to learn at a particular time of day. We have no idea…the fact that our study involves the olfactory system suggests that the circadian cycle could be influencing a number of senses beyond vision.”
The discovery that cockroaches’ memory is strongly modulated by the circadian cycle opens up a new area of research. This is the first example of an insect whose ability of learning is based by its biological clock. It shows that there is more interaction with the cockroaches between biological clocks and memory and learning in general. It will be interesting to see what else they can find out about these small species. After all, who would have thought that a small cockroach could retain new information for several days?
Source:
Science Daily
http://www.sciencedaily.com/releases/2007/09/070927132543.htm
Posted by: Nelina Bridge (1)
posted by PWH @ 2:44 PM
7 comments
7 Comments:
It is a very interesting post about how cockroaches are more active in the dark and inactive in day time. It reminds me that when I was in China, I could see the cockroaches are partying in the street at night. But I less likely see them during day time. It was amazing to test out that cockroaches can retain several day of memory in the dark but not in day time. I am wondering whether their vision is good enough to see in the dark or using their smell.
Posted by Xuni Li (1)
This is definitely an interesting study. Has there been any evidence or theories that suggests the reason for the cockroaches' ability to be able to learn during the night? Also why were those 3 specific smells chosen to test the cockroaches' olfactory stimulation?
Posted by Ben Williams (1)
That was a very interesting article. You'd think that the reason cockroaches scatter like that is that they simply don't like the light. I'd never have thought there might be a more complicated reason like memory. I would be interested to see what other implications the circadian rhythms could have on other animal senses and if there are more interesting motivations behind some of the animal behaviors we take for granted.
Posted by Jon Hicks (1).
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Thank you for your comments. I have done some researching and I have not been able to find any theories that suggest a reason for cockroaches being able to learn during the night but I think it may be because it is the point when all of its senses are working the best. During the day time, cockroaches struggle with vision because their eyes are sensitive to light. At night, cockroaches are in an environment which is most fitting for them, allowing them to learn better during this particular time. If you do find any theories I would be interested to hear about them.
Thank you once again!
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Insects never cease to amaze me. So many people see insects as simple, primitive creatures, when really arthropods have had just as much time to evolve, diversify and specialize. Plus their short generation time allows traits to pervade populations quickly. Another example of a behavior many didn't believe possible of an insects is individual colony member identification by Polistes wasps. These hymenopterans use yellow and black markings on their faces and abdomens to recognize colony members so that dominance does not have to be repeatedly established on every encounter. I will be very interested to hear the adaptive significance of this circadian cockroach behavior.
Posted by Morkeski (1)
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