Morphology and distribution of antennal sensilla in egg parasitoid, Ooencyrtus nezarae (Hymenoptera: Encyrtidae)

Authors: ROH, GWANG HYUN - Gyeongsang National University; LEE, YEON JEONG - Gyeongsang National University; Zhu, Junwei - Jerry; PARK, CHUNG GYOO - Gyeongsang National University

Submitted to: Microscopy Research and Technique
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2019
Publication Date: 7/1/2019
Publication URL: https://handle.nal.usda.gov/10113/6961216
Citation: Roh, G., Lee, Y., Zhu, J.J., Park, C. 2019. Morphology and distribution of antennal sensilla in egg parasitoid, Ooencyrtus nezarae (Hymenoptera: Encyrtidae). Microscopy Research and Technique. 82(7)972-982. Availble: https://doi.org/10.1002/jemt.23244.
DOI: https://doi.org/10.1002/jemt.23244

Interpretive Summary: There are the presence of two morphological types of olfactory sensilla (s. trichodea: subtypes I and s. placoidea) and five other types (finger-like sensilla, s. chaetica: subtypes I, II and III, s. basiconica, s. coeloconica and s. campaniform) in the antennae of O. nezarae. Among olfactory sensilla, subtype I of s. trichodea was male-specific in O. nezarae, which may suggest that this is responsible for its involvement in sensory perception of conspecific female sex pheromone components. Sensilla placoidea was only present in female as olfactory sensilla. It was assumed that may indicate female parasitoids to detect host associated odors in search of their egg-deposit hosts. Role of s. placoide could be using to detect pheromone compound (EZ) which is released by major host stink bug, R. pedestris male, as kairomone, and its isomer ZE as antagonism. Thus, single sensillum recordings for each sensilla type will be worth in identifying ORNs (olfactory receptor neurons) responsible for the respective chemical reception. Our analyses of the morphology and distribution of antennal various types of sensilla will provide some useful information for further studies of their sensory physiological, mechanical, thermo sensilla related to their and behavioral functions of each type of these sensilla, which thus will improves our understanding of the chemical communication system in between O. nezarae and its hosts/host environment.

Technical Abstract: Morphology of antennal sensilla and their distribution were investigated in adults of Ooencyrtus nezarae, an egg parasitoid of Riptortus pedestris, using scanning electron microscopy. Male antennae was found to be significantly greater in overall length than female antennae. The antenna of O. nezarae was composed of the radicula, scape, pedicel, funicle and clava in both sexes, with seven types of sensilla identified: sensillum trichodea; s. finger-like; s. placoidea; s. chaetica; s. basiconica; s. coeloconica, and s. campaniform. They occur in varying number and distribution along the antennae. Two sensillum types were further categorized into additional subtypes, with two subtypes in s. trichodea and three in s. chaetica. Among all characterized sensilla, s. trichodea subtype 1 and s. placoidea were multiporous, indicating that the primary function of these sensilla is olfactory. Sensillum trichodea was the most abundant sensillum type on the antennae of both sexes. Sexual dimorphism was only observed from the subtype 1 sensilla of s. trichodea in males and the subtype 3 sensilla of s. chaetica in females. The morphological information established in our study may provide useful information for further investigations in sensory physiological function of each morphological type of sensilla and their related behavior in this egg parasitoid.