Ultrastructure of Chemosensilla on Antennae and Tarsi ofEctropis obliqua(Lepidoptera: Geometridae)

Abstract

Tea geometrid Ectropis obliqua Prout (Lepidoptera: Geometridae) is a devastating defoliator throughout the tea plantations in China. To explore the putative functions of chemosensilla involved in host selection, the morphology and ultrastructure of antennal and tarsal sensilla in E. obliqua moths were visualized by scanning and transmission electron microscopy. Eight types (including 15 subtypes) of sensilla were identified. On antennae, sensilla trichodea (STR I and STR II) were the most abundant sensillum type characterized by porous cuticle and dendrites in the sensillum lymph. Sensilla chaetica (SCH I–SCH III) possessed a terminal pore and thick nonporous wall, with dendrites in the inner lymph cavity. Three subtypes of sensilla basiconica (SBA I–SBA III) and one type of sensilla auricillica were equipped with thin porous cuticular walls and multiple dendrites in the lymph. Sensilla styloconica were equipped with two or three dendrites that lacked cuticular pores. Sensilla coeloconica possessed four to seven dendrites and were double walled with spoke channels. Böhm bristles and sensilla squamiformia were also observed on the antennae. On tarsi, two subtypes of sensilla chaetica (SCH IV and SCH V) comprised the majority of chemosensilla, and are believed to function in gustatory perception. We summarize the validated functions of related sensilla, and propose potential functions of the corresponding sensilla in E. obliqua . These findings provide a working basis for investigating sensillum function and sensory mechanisms in this pest species.