Chemoreception of amino acids in larvae of two species of Pieris

Abstract

ABSTRACT. Specificity and sensitivity of gustatory neurones in response to twenty‐two amino acids were studied in larvae of Pieris brassicae L. and Pieris rapae L. (Lepidoptera: Pieridae) using electrophysiological methods. Twelve amino acids stimulated a specific amino acid receptor cell in the lateral styloconic sensillum on the maxillary galea of both species, and a further two evoked single unit responses in the same sensillum of P.brassicae only. Histidine, phenylalanine and tryptophane were the weakest stimulants for P.brassicae, but were among the four best stimulants for P.rapae. In both species, eight amino acids were ineffective. Significant differences in stimulatory effectiveness were found between amino acids. Nutritionally essential amino acids were more effective in both species, as in five other lepidopterous species. Similarities with postulated sites for amino acid recognition in the dipteran Boettcherisca peregrina were found.Concentration‐response (C/R) relations were studied for five amino acids. Significant differences were found in saturated response levels. Parameters characterizing C/R relations were estimated using a logistic model. Comparing C/R parameters with phytochemical data on concentrations of free amino acids in a common host plant, Brassica oleracea L., shows that amino acids are effective stimuli at their natural concentrations. The amino acid chemoreceptor seems able to transmit information about concentration differences of amino acids in the plant tissue.