Vibration detection in the treehopper, Umbonia crassicornis
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1
Binghamton University, United States
Plant-borne vibrations play an important role in the mating behavior of the treehopper, Umbonia crassicornis (Hemipteran, Membracidae). Males and females engage in a vibrational duet, where roving males locate stationary females by following their vibrational calls. Little is known about the neurophysiology of vibration detection in these insects. Similarly, the exact means by which U. crassicornis is able to determine signal directionality has yet to be uncovered.
Our study focuses primarily on males, who need to localize females by following their vibrational signals. To identify baseline sensitivities, we have recorded from sensory neurons in the leg of freely moving male U. crassicornis as they are stimulated with non-directional vibrations. Sensory responses to vibration stimuli were recorded using fine wire electrodes. Individuals were presented with vibrational stimuli that covered a range of frequencies and amplitudes. The lowest intensity thresholds and greatest sensitivities occurred within the 100Hz to 1000Hz range, consistent with the range of frequencies for female U. crassicornis calls. Additionally, the sensory neurons showed peaks in spike activity at 100Hz and 600Hz; two frequencies that correspond closely to the dominant frequencies of U. crassicornis calls (DeLuca and Cocroft 2009). Thus, the sensory system appears to be tuned to detect vibrations over a behaviorally relevant range.
Directional cues can be encoded in vibratory signals as time delays and amplitude gradients. However, for small insects like U. crassicornis, such features are not easily detected. In a previous study, the mechanical movements of the bodies of female U. crassicornis were shown to differ depending on whether the vibration originated from in front or behind the insect (Cocroft et al. 2000). This directional response is also shown by the legs, where the vibration-sensitive sensory neurons are located. The transfer of directional cues from the body motion to the leg sensory receptors could be the key to the insect’s ability to determine the direction of the vibration source.
To determine whether this may be the mechanism used by male U. crassicornis to locate females during courtship, individuals were presented with directional vibrations. The mechanical response of the body was recorded using a laser vibrometer. It was found that males’ bodies exhibit directionally oriented mechanical responses to substrate vibrations, similar to that of females. The greatest amount of mechanical response and therefore the greatest potential source of directional information occurred when vibration frequencies were within the range of female U. crassicornis call frequencies. This is consistent with the responses recorded from the sensory receptors.
Acknowledgements
Sponsored by NSF award IOS 0820435
References
Cocroft, R. B., Tieu, T., Hoy, R.R., and Miles, R. N. (2000). Journal of Comparative Physiology A, 186: 695–705.
De Luca, P. A. and Cocroft, R. B. (2009). Behavioral Ecology and Sociobiology, 63: 1787-1798.
Keywords:
Directionality,
Insect communication,
Umbonia crassicornis,
Vibration
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for participant symposium and student poster award)
Topic:
Sensory: Mechanosensation
Citation:
Payne
AE,
Miles
CI and
Su
Q
(2012). Vibration detection in the treehopper, Umbonia crassicornis.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00274
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Mr. Aaron E Payne, Binghamton University, Binghamton, United States, apayne2@binghamton.edu