The Effect of Vibrational Frequency on the Mojave Dune Scorpion, Smeringus mesaensisJodie Tarpo, Kacey KilpatrickDepartment of Biological SciencesSaddleback CollegeMission Viejo, California 92679The Mojave dune scorpion, perhaps the best studied scorpion, is known to detect vibrationalfrequency through sand substrate to hunt prey and sense changes in its immediate environment.Previous studies have shown a clear positive relationship between amplitude and neural response, asmight be expected. To determine a possible relationship between specific frequency and neuralresponse, six dune scorpions were submitted to various frequencies. Due to the extremely faint signalof the action potential, data was insufficient, and no clear determination could be made.Introduction With very limited visual senses, scorpions rely heavily on other stimuli in order to detect and respond totheir immediate surroundings. Their main senses consist of chemoreception as well as light andvibrational detection (Brownell-Farley, 1978; Gaffin-Knowlton, 2009). In many arachnids, there is seismicsensitivity in the basitarsal-tarsal joints affected by amplitude (Brownell-Farley, 1978; Falgiani, 1999).Their ability to detect vibrational stimuli is invaluable to their ability to detect prey, but in somearachnids it has even been shown to be a form of communication, through drumming (Henschel, 2002).They also have eight specific orientation detectors, similar to visual orientation in mammals. This hasbeen shown behaviorally and through computational theory (Brownell and Farley, 1979b; Brownell-Hemmen, 2001). Each of the eight orientations of sensitivity has been tested and accounts for a changein the ability to detect motion from prey (Brownell-Hemmen, 2001). The basitarsal-tarsal slit sensilla insand scorpions have been shown to detect frequencies at various amplitudes (Brownell-Farley, 1979).The anatomy of the trichobothria on their walking legs has been outlined thoroughly (Messlinger, 1987),but they themselves remain to be fully investigated as sensitive detectors of vibrational motion atvarious frequencies. Pertinent data would give better insight into the mechanisms by which thesecreatures hunt prey, and could potentially be utilized in detectional bio-equipment.Materials and Methods Ten scorpions were purchased at nine dollars each from LLLReptiles (Oceanside, CA; San Diego, CA). Theywere kept in separate eight-by-eleven inch plastic containers to prevent cannibalistic behaviors (Farley,Polis, 1979; Polis, 1980). Holes were drilled into the lids to allow for respiration. The containers werefilled with two inches of sand for the specimens to burrow; small crickets were fed to the scorpions onceevery week. Natural lighting was utilized.Before performing the experiment, each of the largest six scorpions was chilled in a freezer at 4ºC forfour minutes in order to stabilize the specimens and slow down their activity; this did not pose danger tothe organism (Baust- Gonzalez-Whitmore, 1985). Utilizing forceps with gloved hands, a scorpion waspicked up gently and placed onto a translucent CD under a stereo microscope. Wax was then used tobind the specimen’s tail and pedipalps to the CD for stability while performing the test. In addition to theutilization of wax, double-sided tape was also used to keep the 4th right leg still against CD, stabilizing thetest site. The 4th right leg was chosen to test because of its large size, ensuring greater accuracy ofmeasurement. Using a frequency generator, various wavelengths of frequency were emitted through aspeaker, placed 25cm away from the specimen. An oscilloscope was connected to both the frequencygenerator and a platinum wire probe inserted into the BCSS of the 4th right leg of the scorpion, allowingfor comparative visualization. After each scorpion was fixed with the probe inserted, the frequencygenerator was initialized, the signal relayed at constant amplitude and at an initial frequency of 20 Hz.We continued this process in upward steps of 100 Hz. Passed through a music amplifier, the signal wasrelayed into a laptop and recorded with Audacity. Each spike per time interval would be counted as an action potential; hence frequency of potentialscould be determined. Each specimen would be recorded with and without the stimuli for control.ResultsNeither the control test nor the experimental test yielded any response. The mean number of spikes(which was zero) for all specimens was calculated, examined, and compared to frequency.Figure 1. The mean number of spikes per interval (100 Hz) of frequency (n=6, p=incalculable).Figure 2 (left). Setup of experiment. Laptop, music amplifier, frequency generator, oscilloscope, speaker,and stereomicroscope (from left to right). Figure 3 (right). Close-up view of stereomicroscope.DiscussionThe lack of clear spikes in amplitude, indicating action potentials in the neurons of the scorpions, can beattributed to several possible errors. As the scorpion continued to move and eat when fed, it is unlikelythat it had died or remained in a vegetative state. However, it is entirely possible that the noise to signalratio was too high, so that a simple parsing of information was not possible (Kim-Kim, 2000).Further attempts at this study would require a differential amplifier to get a high signal to noise ratio.Other possible cause for error could be a misplacing of the microelectrode, or an insufficient sharpnesstherein. However, even a misplaced probe would display some kind of signal due to a cell potential, sothe greatest likely error was the noise to signal ratio.References Baust, J.G., Gonzalez, R., and Whitmore, D.H. (1985). Scorpion Cold Hardiness. Physiological Zoology , 58(5), 526-537Brownell, Philip & Farley, Roger D. (1978). Orientation to vibrations in sand by the nocturnal scorpionParuroctonus mesaensis: Mechanism of target localization. Journal of Comparative Physiology A,131(1), 31-38.Brownell, P.H. & van Hemmen, L.J. (2001). Vibration sensitivity and a computational theory for prey–localizing behavior in sand scorpions. Oxford Journals, 41(5), 1229-1240. Sept. 13, 2001 Falgiani, Michael (1999). Electrophysiological investigation of the sensitivity of scorpion basitarsalcompound slit sensilla to vibratory stimuli. Henschel, J.R. (2002). Long-Distance