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

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.

Re-emergence and diversification of a specialised antennal lobe morphology in ithomiine butterflies

“…In Methona 4 males were analysed in this way to confirm the apparent lack of both MGs and MGCs (see results). Males were chosen for this initial assessment as the MGs are larger in Godyris males (Montgomery and Ott, 2015), as is commonly observed across moths (Rospars and Hildebrand, 1992; Huetteroth and Schachtner, 2005; El Jundi et al, 2009b; Løfaldli et al, 2010; Yan et al 2019). Subsequent visual inspection of females did not reveal any glomeruli specifically enlarged in females.…”

“…While MGCs are ubiquitous in moths (Rospars and Hildebrand, 2000; Huetteroth and Schachtner, 2005; El Jundi et al, 2009b; Løfaldli et al, 2010; Yan et al 2019), including diurnal species (Stöckl et al 2016), they are absent in several phylogenetically disparate butterflies (Rospars, 1983; Carlson et al 2011; Heinze and Reppert, 2012; Montgomery et al 2016) suggesting they were lost at the origin of Papilionoidea. This has been interpreted as reflecting an increased reliance on visual cues, and the decreased importance of long-distance chemical signalling in butterfly mating behaviours (Rospars, 1983; Rutowski, 1991; Andersson et al 2007).…”

Anatomical Comparison of Antennal Lobes in Two Sibling Ectropis Moths: Emphasis on the Macroglomerular Complex

“…Neurobiotin backfilled antennal nerves were counterstained with propidium iodide (PI; MedChem Express, Monmouth Junction, NJ, USA). The neurobiotin concentration applied (1%) was the same used in similar studies on other insect species (Yan et al, 2019 ). The insect was fixed in a cone-shaped plastic tube exposing the head and the antennae out of one tip of the tube.…”

“…The AL is the primary olfactory center of the brain responsible for integrating complex olfactory information (Homberg et al, 1989 ; Kuebler et al, 2012 ). Glomerulus, as the olfactory functional unit, is a subcompartment of the AL and is formed by dense synaptic and recipient dendrites from the ORNs that convey olfactory information from the antenna (Skiri et al, 2005 ; Yan et al, 2019 ). The number of glomeruli is species-specific, and their total volume and position are closely related to the complexity of odorant recognition (Berg et al, 2014 ; Wu et al, 2015 ).…”

“…The macroglomerular complex (MGC) specifically translates sex pheromone information and is a male-specific structure in moth species. Although some species possess a single MGC component (Varela et al, 2009 ), most moth species have three to four MGC glomeruli (Hansson et al, 1994 ; Lee et al, 2006 ; Namiki et al, 2014 ; Nirazawa et al, 2017 ; Jiang et al, 2019 ; Yan et al, 2019 ; Dong et al, 2020 ). Different groups of moth species display different anatomical features.…”