Chemoreception of amino acids by female fourth‐ and sixth‐instar larvae of the spruce budworm

Abstract

AbstractAn electrophysiological approach was used to record the responses of maxillary styloconic sensilla of fourth‐ and sixth‐instar larvae of the spruce budworm Choristoneura fumiferana to 14 amino acids. One cell in the lateral styloconic sensillum was identified as an amino acid‐sensitive neuron. All of the amino acids tested, except l‐proline and l‐arginine, were detected by this cell. Arginine did not evoke a response from either the medial or lateral styloconic sensilla. Proline evoked responses from a cell in the medial styloconic sensillum. It is known from previous behavioural work that l‐proline is a phagostimulant and l‐valine inhibits feeding in Choristoneura; we thus further characterized the responses to these two amino acids. For both instars, l‐proline was detected as low as 0.001 mmol/l and the maximal response was at 50 mmol/l. Stimulation of fourth‐ and sixth‐instar larvae with l‐valine showed that the maximum firing frequency was obtained at 1 mmol/l. Above and below this concentration, firing frequency decreases. Sensory responses to the amino acids stimuli did not correlate with known behavioral responses to similar stimuli.