Hearing and frequency dependence of auditory interneurons in the parasitoid fly <Emphasis Type="Italic">Homotrixa alleni</Emphasis> (Tachinidae: Ormiini) |
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Authors: | Andreas Stumpner Geoff R Allen Reinhard Lakes-Harlan |
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Institution: | 1.Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Abt. Neurobiologie,Georg-August Universit?t G?ttingen,G?ttingen,Germany;2.School of Agricultural Science/TIAR,University of Tasmania,TAS,Australia;3.Institut für Tierphysiologie, AG Integrative Sinnesphysiologie,Justus-Liebig Universit?t Giessen,Giessen,Germany |
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Abstract: | The parasitoid tachinid fly Homotrixa alleni detects its hosts by their acoustic signals. The tympanal organ of the fly is located at the prothorax and contains scolopidial
sensory units of different size and orientation. The tympanal membrane vibrates in the frequency range of approximately 4–35 kHz,
which is also reflected in the hearing threshold measured at the neck connective. The auditory organ is not tuned to the peak
frequency (5 kHz) of the main host, the bush cricket Sciarasaga quadrata. Auditory afferents project in the three thoracic neuromeres. Most of the ascending interneurons branch in all thoracic neuromeres
and terminate in the deutocerebrum of the brain. The interneurons do not differ considerably in frequency tuning, but in their
sensitivity with lowest thresholds around 30 dB SPL. Suprathreshold responses of most neurons depend on frequency and intensity,
indicating inhibitory influence at higher intensities. Some neurons respond particularly well at low frequency sounds (around
5 kHz) and high intensities (80–90 dB SPL), and thus may be involved in detection of the primary host, S. quadrata. The auditory system of H. alleni contains auditory interneurons reacting in a wide range of temporal patterns from strictly phasic to tonic and with clear
differences in frequency responses. |
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Keywords: | Auditory system Host detection Interneurons Temporal pattern Sensory adaptation |
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