Host plant selection based on taste in butterflies: adult egg laying and larval feeding

Abstract

Butterflies use their sense of taste to select their specific host plants. In this study, morphological distribution and electrophysiological responses of taste sensilla were investigated in a butterfly, Atrophaneura alcinous. In oviposition behavior, females detect two plant compounds of an alkaloid (aristolochic acid) and a monosaccharide (sequoyitol) with tarsal taste sensilla on the forelegs. In the fifth tarsi on the forelegs, adult males have two types of taste sensilla, whereas females have the same types as males and also have a female-specific type of taste sensilla (long B type). Adult females use long B type sensilla when searching for oviposition sites to discriminate between host plant compounds and other chemicals. In larvae, there were two types of styloconic sensilla and pharyngeal sensilla on the larval mouthparts, which detect host plant compounds for selecting host plants as food. To understand the transduction mechanism involved in oviposition stimulants at the molecular level, oviposition stimulant binding protein (OSBP) was isolated from the tarsi on the forelegs of female adults of A. alcinous. Immunochemistry revealed that OSBP was expressed only in the females. Using a highly sensitive fluorescent micro-binding assay, OSBP was shown to be bound to aristolochic acid. Adults and larvae of A. alcinous have evolved specialized chemosensory systems for detecting host plant compounds as stimulants for oviposition and feeding.