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23 pages, 1592 KiB

Open AccessReview

The Pheromone Landscape of Apis mellifera: Caste-Determined Chemical Signals and Their Influence on Social Dynamics

by Anna Gryboś, Patrycja Staniszewska, Maciej Sylwester Bryś and Aneta Strachecka

Molecules 2025, 30(11), 2369; https://doi.org/10.3390/molecules30112369 - 29 May 2025

Viewed by 988

A honeybee (Apis mellifera) colony is a superorganism of complex social dynamics. Within the colony, communication between individuals and castes is crucial for maintaining homeostasis. Such complex interactions are possible thanks to semiochemicals called pheromones. The spectrum of pheromonal communication in [...] Read more.

A honeybee (Apis mellifera) colony is a superorganism of complex social dynamics. Within the colony, communication between individuals and castes is crucial for maintaining homeostasis. Such complex interactions are possible thanks to semiochemicals called pheromones. The spectrum of pheromonal communication in bee colonies is wide and differs between castes, especially the queen and the workers. Gland morphology and compounds of secretions result in alterations in both physiological and behavioral responses to certain pheromones in castes. The queen’s glands produce pheromones that maintain her reign and induce division of labor among workers. Workers’ pheromones are adapted to multiple tasks performed by this caste within the colony. This review outlines a neurophysiological pathway in the perception pheromone molecule, with a specific description of the individual anatomical structures essential for the path, such as the morphology of antennae, sensilla, antennal lobes and mushroom bodies. Later on, the study provides insight into specific aspects of the differences between the two castes (queen and workers) in terms of complex pheromonal communication in the hive, by describing the pheromones present in it (QMP, tergal gland pheromone, Dufour gland pheromone, Nasonov pheromone, sting alarm pheromone and tarsal gland pheromone). Full article

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14 pages, 6331 KiB

Open AccessArticle

The Sensory Equipment of Diving Lice, a Host Ecology-Based Comparative Study

by Paula Olivera, Claudio R. Lazzari and María Soledad Leonardi

Insects 2025, 16(6), 574; https://doi.org/10.3390/insects16060574 - 29 May 2025

Viewed by 600

Abstract

Seal lice (Anoplura) parasitize amphibious hosts, such as pinnipeds, and are uniquely adapted to an oceanic environment. As obligate, permanent ectoparasites feed on the blood of their hosts and are completely dependent on them. While studies have begun to explore general diving adaptations, [...] Read more.

Seal lice (Anoplura) parasitize amphibious hosts, such as pinnipeds, and are uniquely adapted to an oceanic environment. As obligate, permanent ectoparasites feed on the blood of their hosts and are completely dependent on them. While studies have begun to explore general diving adaptations, research into seal lice’s sensory biology remains limited. In contrast to the vast majority of insects, including human lice, seal lice are devoid of eyes and depend on antennal sensory reception. This study aims to describe the morphology and putative function of antennal sensilla in five seal lice species: Antarctophthirus microchir, A. carlinii, A. lobodontis, A. ogmorhini, and Lepidophthirus macrorhini, which parasitize the South American sea lion, Weddell seal, crabeater seal, leopard seal, and southern elephant seal, respectively. The antennal structures of each species were analyzed using scanning electron microscopy, and eight morphotypes were identified: spine, cuticular lobe, sensilla squamiformia, sensilla chaetica, sensilla basiconica I and II, tuft organs, and pore organs. The morphology of sensilla and their distribution on the antennal flagellum exhibited variability among genera and species. For instance, the southern elephant louse (Lepidophthirus macrorhini) is characterized by the presence of sensilla squamiformia, while Antarctophthirus spp. are distinguished by sensilla chaetica. Full article

(This article belongs to the Section Medical and Livestock Entomology)

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19 pages, 3902 KiB

Open AccessArticle

Differential Coding of Fruit, Leaf, and Microbial Odours in the Brains of Drosophila suzukii and Drosophila melanogaster

by Claire Dumenil, Gülsüm Yildirim and Albrecht Haase

Insects 2025, 16(1), 84; https://doi.org/10.3390/insects16010084 - 15 Jan 2025

Viewed by 1550

Abstract

Drosophila suzukii severely damages the production of berry and stone fruits in large parts of the world. Unlike D. melanogaster, which reproduces on overripe and fermenting fruits on the ground, D. suzukii prefers to lay its eggs in ripening fruits still on [...] Read more.

Drosophila suzukii severely damages the production of berry and stone fruits in large parts of the world. Unlike D. melanogaster, which reproduces on overripe and fermenting fruits on the ground, D. suzukii prefers to lay its eggs in ripening fruits still on the plants. Flies locate fruit hosts by their odorant volatiles, which are detected and encoded by a highly specialised olfactory system before being translated into behaviour. The exact information-processing pathway is not yet fully understood, especially the evaluation of odour attractiveness. It is also unclear what differentiates the brains of D. suzukii and D. melanogaster to cause the crucial difference in host selection. We hypothesised that the basis for different behaviours is already formed at the level of the antennal lobe of D. suzukii and D. melanogaster by different neuronal responses to volatiles associated with ripe and fermenting fruit. We thus investigated by 3D in vivo two-photon calcium imaging how both species encoded odours from ripe fruits, leaves, fermented fruits, bacteria, and their mixtures in the antennal lobe. We then assessed their behavioural responses to mixtures of ripe and fermenting odours. The neural responses reflect species-dependent shifts in the odour code. In addition to this, morphological differences were also observed. However, this was not directly reflected in different behavioural responses to the odours tested. Full article

(This article belongs to the Section Insect Behavior and Pathology)

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17 pages, 3879 KiB

Open AccessArticle

A New Genus and Species of Marine Symbiotic Shrimp (Crustacea: Decapoda: Palaemonidae) from New Caledonia

by Zdeněk Ďuriš and Karolína Fišarová

Diversity 2024, 16(8), 493; https://doi.org/10.3390/d16080493 - 13 Aug 2024

Viewed by 1748

Abstract

A single specimen of a new genus and species of marine palaemonid shrimp was collected from the outer slope of the barrier reef of Koumac, northwest New Caledonia. The new shrimp is remarkable due to its unique series of diagnostic characters, i.e., the [...] Read more.

A single specimen of a new genus and species of marine palaemonid shrimp was collected from the outer slope of the barrier reef of Koumac, northwest New Caledonia. The new shrimp is remarkable due to its unique series of diagnostic characters, i.e., the presence of compressed supraorbital teeth, a well-developed orbital cavity, closely set antennal and hepatic teeth on the carapace, swollen eyestalks, fully reduced endites on the maxilla, an anteriorly produced lobe on the fourth thoracic sternite, relatively small second chelipeds, and strongly biunguiculate ambulatory dactyli. This specimen occupies an isolated phylogenetic position among the symbiotic palaemonid shrimp analyzed, only demonstrating a feeble morphological inclination towards the “gnathophyllid” section of these. However, neither the main diagnostic characters nor genetic data allow for further clarification of a closer relationship between this new shrimp and any currently known palaemonid genus as of yet. The new genus and species is described in this report, and its phylogenetic position is discussed based on molecular and morphological characters. Full article

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17 pages, 29000 KiB

Open AccessArticle

Odorant Receptors Expressing and Antennal Lobes Architecture Are Linked to Caste Dimorphism in Asian Honeybee, Apis cerana (Hymenoptera: Apidae)

by Haoqin Ke, Yu Chen, Baoyi Zhang, Shiwen Duan, Xiaomei Ma, Bingzhong Ren and Yinliang Wang

Int. J. Mol. Sci. 2024, 25(7), 3934; https://doi.org/10.3390/ijms25073934 - 1 Apr 2024

Cited by 1 | Viewed by 1699

Abstract

Insects heavily rely on the olfactory system for food, mating, and predator evasion. However, the caste-related olfactory differences in Apis cerana, a eusocial insect, remain unclear. To explore the peripheral and primary center of the olfactory system link to the caste dimorphism [...] Read more.

Insects heavily rely on the olfactory system for food, mating, and predator evasion. However, the caste-related olfactory differences in Apis cerana, a eusocial insect, remain unclear. To explore the peripheral and primary center of the olfactory system link to the caste dimorphism in A. cerana, transcriptome and immunohistochemistry studies on the odorant receptors (ORs) and architecture of antennal lobes (ALs) were performed on different castes. Through transcriptomesis, we found more olfactory receptor genes in queens and workers than in drones, which were further validated by RT-qPCR, indicating caste dimorphism. Meanwhile, ALs structure, including volume, surface area, and the number of glomeruli, demonstrated a close association with caste dimorphism. Particularly, drones had more macroglomeruli possibly for pheromone recognition. Interestingly, we found that the number of ORs and glomeruli ratio was nearly 1:1. Also, the ORs expression distribution pattern was very similar to the distribution of glomeruli volume. Our results suggest the existence of concurrent plasticity in both the peripheral olfactory system and ALs among different castes of A. cerana, highlighting the role of the olfactory system in labor division in insects. Full article

(This article belongs to the Special Issue Plant Response to Insects and Microbes 2.0)

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7 pages, 7030 KiB

Open AccessArticle

A New Species of Spelaeometra Polhemus & Ferreira, 2018 (Hemiptera: Heteroptera: Hydrometridae) from a Hotspot of Troglobites in Brazil, Serra do Ramalho Karst Area

by Isabelle R. S. Cordeiro, Maria Elina Bichuette and Felipe F. F. Moreira

Animals 2023, 13(20), 3199; https://doi.org/10.3390/ani13203199 - 13 Oct 2023

Cited by 4 | Viewed by 1421

Abstract

Spelaeometra Polhemus & Ferreira, 2018 (Hemiptera: Heteroptera: Hydrometridae) is a monotypic and troglobitic genus, recently described based on material collected in the state of Minas Gerais, Brazil. From specimens collected in the Gruna do Enfurnado Cave in the Serra do Ramalho karst area, [...] Read more.

Spelaeometra Polhemus & Ferreira, 2018 (Hemiptera: Heteroptera: Hydrometridae) is a monotypic and troglobitic genus, recently described based on material collected in the state of Minas Gerais, Brazil. From specimens collected in the Gruna do Enfurnado Cave in the Serra do Ramalho karst area, municipality of Coribe, state of Bahia, Brazil, we describe Spelaeometra hypogea Cordeiro & Moreira, sp. nov. and compare it with Spelaeometra gruta Polhemus & Ferreira, 2018. The new species is diagnosed by the general body color being pale-yellow to light-brown; antennal segments I and II being subequal in length; the reduced gular lobe, not covering any labial segment; the male proctiger without apical projections; and the male paramere with convex dorsal margin after the curvature, with a narrow hook-like apex. Full article

(This article belongs to the Section Aquatic Animals)

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14 pages, 2700 KiB

Open AccessEditor’s ChoiceArticle

Granger Causality Analysis of Transient Calcium Dynamics in the Honey Bee Antennal Lobe Network

by Marco Paoli, Yuri Antonacci, Angela Albi, Luca Faes and Albrecht Haase

Insects 2023, 14(6), 539; https://doi.org/10.3390/insects14060539 - 9 Jun 2023

Cited by 2 | Viewed by 1785

Abstract

Odorant processing presents multiple parallels across animal species, and insects became relevant models for the study of olfactory coding because of the tractability of the underlying neural circuits. Within the insect brain, odorants are received by olfactory sensory neurons and processed by the [...] Read more.

Odorant processing presents multiple parallels across animal species, and insects became relevant models for the study of olfactory coding because of the tractability of the underlying neural circuits. Within the insect brain, odorants are received by olfactory sensory neurons and processed by the antennal lobe network. Such a network comprises multiple nodes, named glomeruli, that receive sensory information and are interconnected by local interneurons participating in shaping the neural representation of an odorant. The study of functional connectivity between the nodes of a sensory network in vivo is a challenging task that requires simultaneous recording from multiple nodes at high temporal resolutions. Here, we followed the calcium dynamics of antennal lobe glomeruli and applied Granger causality analysis to assess the functional connectivity among network nodes in the presence and absence of an odorous stimulus. This approach revealed the existence of causal connectivity links between antennal lobe glomeruli in the absence of olfactory stimulation, while at odor arrival, the connectivity network’s density increased and became stimulus-specific. Thus, such an analytical approach may provide a new tool for the investigation of neural network plasticity in vivo. Full article

(This article belongs to the Section Insect Physiology, Reproduction and Development)

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20 pages, 20156 KiB

Open AccessArticle

Distribution and Organization of Descending Neurons in the Brain of Adult Helicoverpa armigera (Insecta)

by Xiaolan Liu, Shufang Yang, Longlong Sun, Guiying Xie, Wenbo Chen, Yang Liu, Guirong Wang, Xinming Yin and Xincheng Zhao

Insects 2023, 14(1), 63; https://doi.org/10.3390/insects14010063 - 9 Jan 2023

Cited by 3 | Viewed by 2536

Abstract

The descending neurons (DNs) of insects connect the brain and thoracic ganglia and play a key role in controlling insect behaviors. Here, a comprehensive investigation of the distribution and organization of the DNs in the brain of Helicoverpa armigera (Hübner) was made by [...] Read more.

The descending neurons (DNs) of insects connect the brain and thoracic ganglia and play a key role in controlling insect behaviors. Here, a comprehensive investigation of the distribution and organization of the DNs in the brain of Helicoverpa armigera (Hübner) was made by using backfilling from the neck connective combined with immunostaining techniques. The maximum number of DN somata labeled in H. armigera was about 980 in males and 840 in females, indicating a sexual difference in DNs. All somata of DNs in H. armigera were classified into six different clusters, and the cluster of DNd was only found in males. The processes of stained neurons in H. armigera were mainly found in the ventral central brain, including in the posterior slope, ventral lateral protocerebrum, lateral accessory lobe, antennal mechanosensory and motor center, gnathal ganglion and other small periesophageal neuropils. These results indicate that the posterior ventral part of the brain is vital for regulating locomotion in insects. These findings provide a detailed description of DNs in the brain that could contribute to investigations on the neural mechanism of moth behaviors. Full article

(This article belongs to the Section Insect Physiology, Reproduction and Development)

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14 pages, 7069 KiB

Open AccessArticle

Pirenzepine Binding Sites in the Brain of the Honeybee Apis mellifera: Localization and Involvement in Non-Associative Learning

by Chaïma Messikh, Monique Gauthier and Catherine Armengaud

Insects 2022, 13(9), 806; https://doi.org/10.3390/insects13090806 - 5 Sep 2022

Viewed by 1938

Abstract

Muscarinic acetylcholine receptors (mAChRs) play a central role in learning and memory in mammals as in honeybees. The results obtained in the honeybee Apis mellifera are based on the detrimental effects of the mAChR antagonists, atropine and scopolamine, on olfactory associative memory. Binding [...] Read more.

Muscarinic acetylcholine receptors (mAChRs) play a central role in learning and memory in mammals as in honeybees. The results obtained in the honeybee Apis mellifera are based on the detrimental effects of the mAChR antagonists, atropine and scopolamine, on olfactory associative memory. Binding sites for the mAChR antagonist BODIPY^® FL pirenzepine were localized in the brain of the honeybee forager. Pirenzepine binding sites were detected indifferently in several somata and neuropilar areas. The highest binding site densities were present in the central complex and in somata of the dorsomedial border of the antennal lobes. An additional binding pattern was found in somata of the subesophageal ganglion. By contrast, Kenyon cell (KC) somata were not stained. Pirenzepine (PZ) effects on non-associative learning were evaluated. Treated animals required more trials for the habituation of the proboscis extension reflex (PER) than controls, and the duration of the PER increased after PZ brain injection. These results suggest that the network mediating habituation of the PER involves PZ binding sites that are not necessarily present on the circuitry mediating olfactory conditioning of the PER. Full article

(This article belongs to the Section Insect Behavior and Pathology)

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12 pages, 3719 KiB

Open AccessArticle

Brain Investigation on Sexual Dimorphism in a Gynandromorph Moth

by Elena Ian, Xi Chu and Bente Gunnveig Berg

Insects 2022, 13(3), 284; https://doi.org/10.3390/insects13030284 - 14 Mar 2022

Cited by 3 | Viewed by 3480

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Collection Insect Sensory Biology)

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10 pages, 652 KiB

Open AccessArticle

Pheromone Receptor Knock-Out Affects Pheromone Detection and Brain Structure in a Moth

by Fotini Koutroumpa, Christelle Monsempès, Sylvia Anton, Marie-Christine François, Nicolas Montagné and Emmanuelle Jacquin-Joly

Biomolecules 2022, 12(3), 341; https://doi.org/10.3390/biom12030341 - 22 Feb 2022

Cited by 7 | Viewed by 3302

Abstract

Sex pheromone receptors are crucial in insects for mate finding and contribute to species premating isolation. Many pheromone receptors have been functionally characterized, especially in moths, but loss of function studies are rare. Notably, the potential role of pheromone receptors in the development [...] Read more.

Sex pheromone receptors are crucial in insects for mate finding and contribute to species premating isolation. Many pheromone receptors have been functionally characterized, especially in moths, but loss of function studies are rare. Notably, the potential role of pheromone receptors in the development of the macroglomeruli in the antennal lobe (the brain structures processing pheromone signals) is not known. Here, we used CRISPR-Cas9 to knock-out the receptor for the major component of the sex pheromone of the noctuid moth Spodoptera littoralis, and investigated the resulting effects on electrophysiological responses of peripheral pheromone-sensitive neurons and on the structure of the macroglomeruli. We show that the inactivation of the receptor specifically affected the responses of the corresponding antennal neurons did not impact the number of macroglomeruli in the antennal lobe but reduced the size of the macroglomerulus processing input from neurons tuned to the main pheromone component. We suggest that this mutant neuroanatomical phenotype results from a lack of neuronal activity due to the absence of the pheromone receptor and potentially reduced neural connectivity between peripheral and antennal lobe neurons. This is the first evidence of the role of a moth pheromone receptor in macroglomerulus development and extends our knowledge of the different functions odorant receptors can have in insect neurodevelopment. Full article

(This article belongs to the Special Issue Insect Receptors: Biochemical, Physiological and Molecular Studies)

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13 pages, 1249 KiB

Open AccessReview

Evolution of the Sex Pheromone Communication System in Ostrinia Moths

by Dan-Dan Zhang

Insects 2021, 12(12), 1067; https://doi.org/10.3390/insects12121067 - 28 Nov 2021

Cited by 7 | Viewed by 3553

Abstract

It remains a conundrum in the evolution of sexual communication how the signals and responses can co-ordinate the changes during speciation. The genus Ostrinia contains several closely related species as well as distinctive strains with pheromone polymorphism and represents an example of ongoing [...] Read more.

It remains a conundrum in the evolution of sexual communication how the signals and responses can co-ordinate the changes during speciation. The genus Ostrinia contains several closely related species as well as distinctive strains with pheromone polymorphism and represents an example of ongoing speciation. Extensive studies in the genus, especially in the species the European corn borer O. nubilalis (ECB), the Asian corn borer O. furnacalis (ACB) and the adzuki bean borer O. scapulalis (ABB), have provided valuable insights into the evolution of sex pheromone communication. This review presents a comprehensive overview of the research on pheromone communication in different Ostrinia species over the past four decades, including pheromone identification and biosynthesis, the ligand profiles of pheromone receptor (PR) genes, the physiology of peripheral olfactory sensory neurons (OSNs) and the projection pattern to the antennal lobe. By integrating and comparing the closely related Ostrinia species and strains, it provides an evolutionary perspective on the sex pheromone communication in moths in general and also outlines the outstanding questions that await to be elucidated by future studies. Full article

(This article belongs to the Collection Insect Sensory Biology)

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18 pages, 3348 KiB

Open AccessArticle

OBP14 (Odorant-Binding Protein) Sensing in Adelphocoris lineolatus Based on Peptide Nucleic Acid and Graphene Oxide

by Wenhua Tian, Tao Zhang, Shaohua Gu, Yuyuan Guo, Xiwu Gao and Yongjun Zhang

Insects 2021, 12(5), 422; https://doi.org/10.3390/insects12050422 - 8 May 2021

Cited by 4 | Viewed by 2838

Abstract

OBPs play a crucial role in the recognition of ligands and are involved in the initial steps of semiochemical perception. The diverse expression of OBP genes allows them to participate in different physiological functions in insects. In contrast to classic OBPs with typical [...] Read more.

OBPs play a crucial role in the recognition of ligands and are involved in the initial steps of semiochemical perception. The diverse expression of OBP genes allows them to participate in different physiological functions in insects. In contrast to classic OBPs with typical olfactory roles in A. lineolatus, the physiological functions of Plus-C OBPs remain largely unknown. In addition, detection of the expression of insect OBP genes by conventional methods is difficult in vitro. Here, we focused on AlinOBP14, a Plus-C OBP from A. lineolatus, and we developed a PNA-GO-based mRNA biosensor to detect the expression of AlinOBP14. The results demonstrated that AlinOBP14 plays dual roles in A. lineolatus. The AlinOBP14 is expressed beneath the epidermis of the vertex and gena in heads of A. lineolatus, and it functions as a carrier for three terpenoids, while AlinOBP14 is also expressed in the peripheral antennal lobe and functions as a carrier for endogenous compounds such as precursors for juvenile hormone (JH) and JHⅢ. Our investigation provides a new method to detect the expression of OBP genes in insects, and the technique will facilitate the use of these genes as potential targets for novel insect behavioral regulation strategies against the pest. Full article

(This article belongs to the Collection Biology and Management of Sap-Sucking Pests)

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25 pages, 5261 KiB

Open AccessArticle

Effects of Multi-Component Backgrounds of Volatile Plant Compounds on Moth Pheromone Perception

by Lucie Conchou, Philippe Lucas, Nina Deisig, Elodie Demondion and Michel Renou

Insects 2021, 12(5), 409; https://doi.org/10.3390/insects12050409 - 1 May 2021

Cited by 4 | Viewed by 3306

Abstract

The volatile plant compounds (VPC) alter pheromone perception by insects but mixture effects inside insect olfactory landscapes are poorly understood. We measured the activity of receptor neurons tuned to Z7-12Ac (Z7-ORN), a pheromone component, in the antenna and central neurons in male Agrotis [...] Read more.

The volatile plant compounds (VPC) alter pheromone perception by insects but mixture effects inside insect olfactory landscapes are poorly understood. We measured the activity of receptor neurons tuned to Z7-12Ac (Z7-ORN), a pheromone component, in the antenna and central neurons in male Agrotis ipsilon while exposed to simple or composite backgrounds of a panel of VPCs representative of the odorant variety encountered by a moth. Maps of activities were built using calcium imaging to visualize which areas in antennal lobes (AL) were affected by VPCs. We compared the VPC activity and their impact as backgrounds at antenna and AL levels, individually or in blends. At periphery, VPCs showed differences in their capacity to elicit Z7-ORN firing response that cannot be explained by differences in stimulus intensities because we adjusted concentrations according to vapor pressures. The AL neuronal network, which reformats the ORN input, did not improve pheromone salience. We postulate that the AL network evolved to increase sensitivity and to encode for fast changes of pheromone at some cost for signal extraction. Comparing blends to single compounds indicated that a blend shows the activity of its most active component. VPC salience seems to be more important than background complexity. Full article

(This article belongs to the Collection Insect Sensory Biology)

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15 pages, 17851 KiB

Open AccessArticle

The Antennal Pathway of Dragonfly Nymphs, from Sensilla to the Brain

by Silvana Piersanti, Manuela Rebora, Gianandrea Salerno and Sylvia Anton

Insects 2020, 11(12), 886; https://doi.org/10.3390/insects11120886 - 16 Dec 2020

Cited by 8 | Viewed by 4817

Abstract

Dragonflies are hemimetabolous insects, switching from an aquatic life style as nymphs to aerial life as adults, confronted to different environmental cues. How sensory structures on the antennae and the brain regions processing the incoming information are adapted to the reception of fundamentally [...] Read more.

Dragonflies are hemimetabolous insects, switching from an aquatic life style as nymphs to aerial life as adults, confronted to different environmental cues. How sensory structures on the antennae and the brain regions processing the incoming information are adapted to the reception of fundamentally different sensory cues has not been investigated in hemimetabolous insects. Here we describe the antennal sensilla, the general brain structure, and the antennal sensory pathways in the last six nymphal instars of Libellula depressa, in comparison with earlier published data from adults, using scanning electron microscopy, and antennal receptor neuron and antennal lobe output neuron mass-tracing with tetramethylrhodamin. Brain structure was visualized with an anti-synapsin antibody. Differently from adults, the nymphal antennal flagellum harbors many mechanoreceptive sensilla, one olfactory, and two thermo-hygroreceptive sensilla at all investigated instars. The nymphal brain is very similar to the adult brain throughout development, despite the considerable differences in antennal sensilla and habitat. Like in adults, nymphal brains contain mushroom bodies lacking calyces and small aglomerular antennal lobes. Antennal fibers innervate the antennal lobe similar to adult brains and the gnathal ganglion more prominently than in adults. Similar brain structures are thus used in L. depressa nymphs and adults to process diverging sensory information. Full article

(This article belongs to the Collection Insect Sensory Biology)

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