Characterization of Antennal Sensilla and Immunolocalization of Odorant-Binding Proteins on Spotted Alfalfa Aphid, Therioaphis trifolii (Monell)

Abstract

The spotted alfalfa aphid [Therioaphis trifolii (Monell), Homoptera, Drepanosiphidae] is a well-known destructive pest that can significantly reduce alfalfa yields. Herein, the morphology of antennal sensilla of T. trifolii has been examined by using scanning electron microscopy and the ultrastructure of sensilla stellate and placoidea was described by transmission electron microscopy. Stellate sensilla, placoid sensilla, and coeloconic sensilla were found on the 6th segment, and a single sensillum placoidea was located on the 5th segment. Placoid sensilla were also present on the 3rd antennal segment of alate and apterous aphids, and the number was similar between two morphs. Two types of trichoid sensilla and coeloconic sensilla were found on the antennae, respectively. The results of ultrastructure showed that stellate sensilla are innervated by three neurons, while placoid sensilla present three groups of neurons, equipped with 2–3 dendrites in each neuron group. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of sensilla stellate and placoidea, and we observed that the antiserum against OBP6 intensively labeled all placoid sensilla from both primary and secondary rhinaria. OBP7 and OBP8 could also be detected in placoid sensilla, but less strongly than OBP6. In addition, OBP6, OBP7, and OBP8 were densely labeled in stellate sensilla, suggesting OBP6, OBP7, and OBP8 may sense alarm pheromone germacrene A in T. trifolii.

Polyphenism in Antennal Sensilla Among Different Adult Morphs of Nonhost-Alternating, Holocyclic Sitobion avenae (Hemiptera: Aphididae)

“…davazhamci , and Rhi. tuberculata ( Kanturski and Barjadze 2018 , Kanturski and Stekolshchikov 2018 , Kanturski et al 2020 , Song et al 2020 ). In this study, fundatrices, apterous virginoparae, and apterous sexuparae had one or two secondary rhinaria, whereas oviparae had no secondary rhinarium in S. avenae .…”

“…The number and distribution of small multiporous placoid sensilla (secondary rhinaria) vary among the morphs of conspecies, with males possessing the greatest abundance of secondary rhinaria ( Du et al 1995 , Zhang and Zhang 2000 , Park and Hardie 2002 ). Alate virginoparae and gynoparae also have a large number of secondary rhinaria, while in apterous virginoparae and oviparae these rhinaria are present in small number or disappear completely ( Du et al 1995 , Zhang and Zhang 2000 , Park and Hardie 2002 , Kanturski et al 2020 , Song et al 2020 ). Secondary rhinaria showed a substantially greater response to nepetalactone and nepetalol in males and gynoparae but not in alate virginoparae ( Park and Hardie 2002 , 2004 ).…”

Comparative morphology and plant volatile responses of antennal sensilla in Cinara cedri (Hemiptera: Lachninae), Eriosoma lanigerum (Hemiptera: Eriosomatinae), and Therioaphis trifolii (Hemiptera: Calaphidinae)

“…Based on the SEM observation of primary rhinaria in C. cedri and E. lanigerum , and previous reports about similar observations in T. trifolii (Song et al, 2020 ), we conducted functional characterizations of ORNs housed in the placoid sensilla of primary rhinaria and how they responded to 18 chemicals derived from plant volatiles ( Table 1 ). Functional profiles of primary rhinaria in the three aphid species were divided into three classes.…”

“…Primary rhinaria are present on the 4th, 5th, and 6th segments in C. cedri , but only on the 5th and 6th segments in the other aphid species (Song et al, 2020 ). The primary rhinarium on the 6th segment was composed of one large placoid sensillum (LP6), two small placoid sensilla (SP6), and four coeloconic sensilla ( Figures 2D – H ).…”

“…In aphids, antennae are the main olfactory organs, and are filiform and composed of 5–6 segments, including a scape, a pedicel, and a flagellum with 3–4 flagellomeres (Kanturski et al, 2017 ; Song et al, 2020 ; Wu et al, 2022 ). The main sensory structures are called rhinaria (Wensler, 1974 , 1977 ; Bromley and Anderson, 1982 ; Pickett et al, 2013 ).…”