Last year a small Wisconsin company received national media attention when it offered to implant employees with micro radio-frequency identification tags, which would allow them to circumvent the tedium of normal security measures like logging in to computers and unlocking doors. While the ethical aspects of such technology have been hotly debated, likely most people have direct experience with the non-implanted versions of these tags, whether they know it or not. In fact, anyone using an ID for work, keys for a car made in the last few years, or checked out books at the library has also used RFID tags in everyday life. Such technology works through the use of passive tags and scanners; a scanner produces radio waves which power small RFID tags, which send back a ID number or other information. However, RFID isn’t just useful for manufactured items, but also is of increasing importance for biologists studying animals.
A variety of large RFID tags used for tracking items like books and DVDs in libraries and stores
Tracking living organisms has always been a challenge for biologists, as many studies require long term or detailed observations, and simply having human beings watch these organisms is rarely efficient or practical. This issue is further emphasized with very small animals, those that travel long distances, or any others that may be difficult to track or to distinguish between individuals. We in the HMC Bee Lab have often struggled with this issue: how do you track an entire colony of very small insects, sometimes with more than 100 individuals at one time? One way to combat these problems is to automate this system by using RFID to track insects. With such a system, RFID tags are attached to individual insects allowing for a record of each time an individual moves past a scanner.
One of our turtle ants under the microscope after tagging. The RFID tag is a small square located on the thorax of the ant
However, there are also a lot of challenges when using this technology on actual living organisms. One major one is balancing the size of tags with how far away the RFID tags can be scanned from. The smaller the RFID tag, the closer the scanner has to be in order to property scan the tag. One team of researchers in North Carolina affixed large RFID tags to billbugs, and a metal detector like device was used to relocate these insects in the field. However, in using tags that were twice the body weight of the insects they were observing, the study reported low survival rates in tagged insects. As such, most studies choose to use smaller devices to minimize the effects of the tagging itself, which requires novel ways of ensuring tags are properly scanned. With small RFID tags, insects often need to be less than a centimeter from the reader and oriented in the right direction. One group of researchers led by our collaborator Elva Robinson got around this problem by using RFID triggered doors. In these setups, ants can only enter or leave a nest if their RFID tag triggers the opening of a small door at the nest entrance or exit. In the absence of a door, one study on honey bees used the entryways of a hive to physically constrain bees to walk only one way into the hive, under the RFID scanner. Even with such inventive approaches, however, tagging is a stressful process for insects and can have negative outcomes.
A tagged turtle ant being scanned with an RFID scanner
RFID technology has been used to study a wide variety of different species, with many different goals in mind. While studies on honey bees and billbugs might not be directly related to our current studies with turtle ants, they do provide some insights into the potential difficulties with implementing RFID tagging in our research. However, it also has the potential to open up exciting new possibilities for experiments on turtle ants. Previously, the lab has relied heavily on videos of ant experiments and creating code to automatically track ants from video. Yet, such tracking is difficult, and using video also limits experiments to certain sizes and setups. In order to conduct new experiments with different approaches, like using 3D structures, technology like RFID might be necessary to accurately observe the movement of ants in our lab.
References
Silcox, D. E., J. P. Doskocil, C. E. Sorenson, R. L. Brandenburg. 2011. “Radio Frequency Identification Tagging: A Novel Approach to Monitoring Surface and Subterranean Insects”. American Entomologist 57 (August): 86:93. doi.org/10.1093/ae/57.2.86
Schneider CW, Tautz J, Grünewald B, Fuchs S. 2012. “RFID tracking of sublethal effects of two neonicotinoid insecticides on the foraging behavior of Apis mellifera”. PLoS One 7 (January). doi: 10.1371/journal.pone.0030023
Robinson, Elva J.H., Faith D. Smith, Kathryn M.E. Sullivan, and Nigel R. Franks. 2009. “Do ants make direct comparisons?”. Proc Bio Sci 276 (July): 2635-2641. doi: 10.1098/rspb.2009.0350
Media Credits
No comments:
Post a Comment