The Effect of Vibrational Frequency on the Mojave Dune Scorpion, Smeringus mesaensis
Jodie Tarpo, Kacey Kilpatrick
Department of Biological Sciences
Saddleback College
Mission Viejo, California 92679
The Mojave dune scorpion, perhaps the best studied scorpion, is known to detect vibrational frequency 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, as might be expected. To determine a possible relationship between specific frequency and neural response, six dune scorpions were submitted to various frequencies. Due to the extremely faint signal of 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 to their immediate surroundings. Their main senses consist of chemoreception as well as light and vibrational detection (Brownell-Farley, 1978;Gaffin-Knowlton, 2009). In many arachnids, there is seismic sensitivity 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 some arachnids 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 has been 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 change in the ability to detect motion from prey (Brownell-Hemmen, 2001). The basitarsal-tarsal slit sensilla in sand 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 at various frequencies. Pertinent data would give better insight into the mechanisms by which these creatures 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). They were 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 were filled with two inches of sand for the specimens to burrow; small crickets were fed to the scorpions once every week. Natural lighting was utilized.
Before performing the experiment, each of the largest six scorpions was chilled in a freezer at 4ºC for four minutes in order to stabilize the specimens and slow down their activity; this did not pose danger to the organism (Baust- Gonzalez-Whitmore, 1985). Utilizing forceps with gloved hands, a scorpion was picked up gently and placed onto a translucent CDunder a stereo microscope. Wax was then used to bind the specimen’s tail and pedipalps to the CD for stability while performing the test. In addition to the utilization of wax, double-sided tape was also used to keep the 4th right leg still against CD, stabilizing the test site. The 4th right leg was chosen to test because of its large size, ensuring greater accuracy of measurement. Using a frequency generator, various wavelengths of frequency were emitted through a speaker, placed 25cm away from the specimen. An oscilloscope was connected to both the frequency generator and a platinum wire probe inserted into the BCSS of the 4th right leg of the scorpion, allowing for comparative visualization. After each scorpion was fixed with the probe inserted, the frequency generator 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 was relayed into a laptop and recorded with Audacity.
Each spike per time interval would be counted as an action potential; hence frequency of potentials could be determined. Each specimen would be recorded with and without the stimuli for control.
Results
Neither 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.
Discussion
The lack of clear spikes in amplitude, indicating action potentials in the neurons of the scorpions, can be attributed to several possible errors. As the scorpion continued to move and eat when fed, it is unlikely that it had died or remained in a vegetative state. However, it is entirely possible that the noise to signal ratio 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 sharpness therein. However, even a misplaced probe would display some kind of signal due to a cell potential, so the 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), 526-537
Brownell, Philip & Farley, Roger D. (1978). Orientation to vibrations in sand by the nocturnal scorpion Paruroctonus 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 basitarsal compound slit sensilla to vibratory stimuli.
Henschel, J.R. (2002). Long-Distance Wandering and Mating by the Dancing White Lady Spider (Leucorchestris arenicola) (Araneae, Sparassidae) Across Namib Dunes. The Journal of Arachnology, 30(2):321-330.
Kim, K., & Kim, S. (2000). Neural Spike Sorting Under Nearly O-dB Signal-to-Noise Ratio Using Nonlinear Energy Operator and Artificial Neural-Network Classifier.IEEE Transactions On Biomedical Engineering,47(10), 1406.
Knowlton, Elizabeth D. & Gaffin, Douglas D. (2009). A new approach to examining scorpion peg sensilla: the mineral oil flood technique. TheJournal of Arachnology.
Messlinger, Karl (1987). Fine structure of scorpion trichobothria(Arachnida, Scorpiones). Zoomorphology, 107(1), 49-57.
Polis, G.A. (1980). The effect of cannibalism on the demography and activity of a natural population of desert scorpions.Behavioral Ecology and Sociobiology 7: 25–35.
Polis, G.A. and Farley, R.D. (1979). Behavior and ecology of mating in the cannibalistic scorpion , Paruroctonus mesaensis Stahnke (Seorpionida : Vaejovidae). J. Arachnol. 7 :33-46.
Review Form
Department of Biological Sciences
SaddlebackCollege, Mission Viejo, CA92692
Author (s):___Jodie Tarpo and Kacy Kilpatrick______
Title:___The Effect of Vibrational Frequency on the Mojave Dune Scorpion, Smeringus mesaenis ______
Summary
Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you understood the paper.
Scorpions were subjected to frequencies from 20Hz to 1020Hz to determine which frequency was the best for stimulation of the action potentials in the brains of the scorpion. The set up involved a laptop, music amplifier, frequency generator, oscilloscope, speaker, and a stereomicroscope. The control for this experiment was no frequency. The mean number of spikes was zero and the p value was incalculable. A possible explanation for the lack of spikes could have been the noise to signal ratio.
General Comments
Generally explain the paper’s strengths and weaknesses and whether they are serious, or important to our current state of knowledge.
Since we are learning about action potentials in lecture as well as animals relating to the scorpion in lab, it was appropriate that the group decided to perform this research experiment. The paper has a lot of information from references which shows a lot of thought and research put into this experiment. The materials and methods were clear and easily followed. There is no real weakness to the paper other than the lack of results. Also in the discussion there was explanation of the possible errors about misplacing the electrode. That should be left out because it shows that there was only one attempt when there could have been a another run because there was enough time for an experiment like this. Also there were ten scorpions purchased but only six were used in the experiment.
Technical Criticism
Review technical issues, organization and clarity. Provide a table of typographical errors, grammatical errors, and minor textual problems. It's not the reviewer's job to copy Edit the paper, mark the manuscript.
-Headings need to be centered
-There needs to be a space between the measurement and the unit. ( ex: 25 cm)
-Ten scorpions purchased, but six used in experiment (possible typo?)
This paper was a final version This paper was a rough draft
Recommendation
This paper should be published as is
This paper should be published with revision X
This paper should not be published
Signature:______Date:___11/29/11______