Glomerular Organization of the Antennal Lobes of the Diamondback Moth, Plutella xylostella L.

Xizhong Yan,Chi Hao,Jiaoxin Xie,Zhiyu Wang,Caiping Deng,Xuejun Sun

doi:10.3389/fnana.2019.00004

Xizhong Yan, Chi Hao + Show 4 more

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https://doi.org/10.3389/fnana.2019.00004

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Abstract

The antennal lobe of the moth brain is the primary olfactory center processing information concerning pheromones and plant odors. Plutella xylostella is a major worldwide pest of cruciferous vegetables and its behavior is highly dependent on their olfactory system. However, detailed knowledge of the anatomy and function of the P. xylostella olfactory system remains limited. In the present study, we present the 3-Dimentional (3-D) map of the antennal lobe of P. xylostella, based on confocal microscopic analysis of glomerular segmentation and Neurobiotin backfills of Olfactory Receptor Neurons (ORNs). We identified 74–76 ordinary glomeruli and a macroglomerular complex (MGC) situated at the entrance of the antennal nerve in males. The MGC contained three glomeruli. The volumes of glomeruli in males ranged from 305.83 ± 129.53 to 25440.00 ± 1377.67 μm3. In females, 74–77 glomeruli were found, with the largest glomerulus ELG being situated at the entrance of the antennal nerve. The volumes of glomeruli in females ranged from 802.17 ± 95.68 to 8142.17 ± 509.46 μm3. Sexual dimorphism was observed in anomalous supernumerary, anomalous missing, shape, size, and array of several of the identified glomeruli in both sexes. All glomeruli, except one in the antennal lobe (AL), received projections of antennal ORNs. The glomeruli PV1 in both sexes received input from the labial palp nerve and was assumed as the labial pit organ glomerulus (LPOG). These results provide a foundation for better understanding of coding mechanisms of odors in this important pest insect.

Highlights

In insects, the olfactory system plays a highly important role in detecting odorants involved in sexual communication, social integration, host recognition, and escaping from enemies over a distance (Lopes et al, 2002; Gill et al, 2013; Sun et al, 2014; Xu et al, 2016)
The macroglomerular complex (MGC) receives and processes information regarding the female sex pheromone, calcium imaging in Heliothis virescens confirms that sex pheromone responses are restricted to the male-specific MGC, plant odors to ordinary glomeruli (Galizia et al, 2000), and sex pheromone-specific receptor neurons arborize in the MGC (Hansson et al, 1992; Ochieng et al, 1995)
We presented a complete 3-D reconstruction of the glomerular organization of P. xylostella, based on the systematic

Summary

Introduction

The olfactory system plays a highly important role in detecting odorants involved in sexual communication, social integration, host recognition, and escaping from enemies over a distance (Lopes et al, 2002; Gill et al, 2013; Sun et al, 2014; Xu et al, 2016). The most prominent sensillum types have olfactory functions and contain olfactory receptor neurons (ORNs), which send projections directly to the antennal lobe (AL), the primary olfactory center of the insect brain. Sexual dimorphism with respect to specific glomeruli is observed, e.g., the AL of male Lepidoptera contains enlarged glomeruli that form the macroglomerular complex (MGC) at the entrance of the antennal nerve into the Al in Mamestra brassicae (Rospars, 1983) and Trichoplusia ni (Todd et al, 1992). The one ORN class to one glomerulus and to one PN class relationship in the Drosophila olfactory system is likely an extreme situation as, in other species, this may vary as the glomeruli numbers vary dramatically. The MGC receives and processes information regarding the female sex pheromone, calcium imaging in Heliothis virescens confirms that sex pheromone responses are restricted to the male-specific MGC, plant odors to ordinary glomeruli (Galizia et al, 2000), and sex pheromone-specific receptor neurons arborize in the MGC (Hansson et al, 1992; Ochieng et al, 1995)

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