Abstract
Simple SummaryThe noctuid moth, Helicoverpa armigera, is one of the globally most damaging agricultural pest insects. Generally, exploration of the male- and female-specific neural architecture underlying its reproductive behavior is crucial for developing biological and environment-friendly alternatives to the traditional pest control management. In this study, we utilized the opportunity to uncover putative sex differences in H. armigera by comparing details in the brain anatomy between the male and female hemispheres in one gynandromorphic individual. The methods included synapsin immunostaining, confocal microscopy, and the digital reconstruction of several brain areas involved in processing input about odor and vision, respectively. The results demonstrated sex-specific arrangements applying to distinct olfactory neuropils, including not only the primary olfactory center, the antennal lobe, but also higher order levels involved in odor-associated memory formation.The present study was dedicated to investigating the anatomical organization of distinct neuropils within the two brain hemispheres of a gynandromorphic moth of the species Helicoverpa armigera. High quality confocal imaging of a synapsin immuno-stained preparation combined with three-dimensional reconstructions made it possible to identify several brain structures involved in processing odor input and to measure their volumes in the male and female hemispheres. Thus, in addition to reconstructing the antennal lobes, we also made digital models of the mushroom body calyces, the pedunculus, and the vertical and medial lobes. As previously reported, prominent sexual dimorphism was demonstrated in the antennal lobes via the identification of a male-specific macroglomerular complex (MGC) and a female-specific complex (Fc) in each of the two brain hemispheres of the gynandromorph. Additionally, sex-specific differences were found in volume differences for three other neuropil structures—the calyces, pedunculus, and vertical lobe. The putative purpose of larger volumes of three mushroom body neuropils in females as compared to males is discussed.
Highlights
Introduction iationsDimorphic individuals, in which the bodies consist of both female and male parts, were observed before the term gynandromorphism was coined and described by Rudolfi for the moth species, Gastropacha quercifolia, in 1825
Digital reconstruction of the prominent and recognizable brain areas allowed a comparison of anatomical traits and volumes of the paired neuropils of two hemispheres in a bilateral gynandromorphic brain
Each neuropil is in a shade of green/magenta, representing the male and the female hemispheres, respectively
Summary
In which the bodies consist of both female and male parts, were observed before the term gynandromorphism was coined and described by Rudolfi for the moth species, Gastropacha quercifolia, in 1825. Though this phenomenon is more commonly reported in insects than in other animal classes, the estimated occurrence of insect gynandromorphs is about 0.01 to 0.05%. Gynandromorphism has been observed in several insect orders including Lepidoptera, Hymenoptera, Coleoptera, Diptera, and Orthoptera, but its occurrence across orders is not even [1]. Several thousands have been reported in Lepidoptera in comparison with 90 in Hymenoptera; this fact could be due to recognizable sexual dimorphic features in the former order [2].
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