D.N. LAPSHIN, D.D. VORONTSOV
FREQUENCY RETUNING OF TYMPANIC ORGAN OF NOCTUID MOTH (NOCTUIDAE, LEPIDOPTERA)
The aim of this study was to prove experimentally the capability of the hearing system of noctuid moth (Crino satura Schiff., Enargia paleacea Esp.) to change it's frequency tuning during evoked contraction of metathoracic muscles. To measure the threshold intensity of sound stimulus we recorded extracellularly the activity of prothoracic ganglion interneurons. The shape of threshold curves obtained was in general similar to the ones shown before by authors who recorded from tympanic nerve. An application of potassium chloride (3M, 2 mkl) to the haemolymph of metathorax caused local muscle contraction for several minutes and a rise of auditory thresholds at lower frequencies (by up to 10-14 dB SPL at 10-30 kHz). Over 60 kHz there were an opposite change: after KCl application thresholds decreased by 3 dB SPL on average in C.satura. E.paleacea demonstrated the similar effect at frequencies over 70 kHz.
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