Postembryonic growth of the antennal lobes and their identified glomeruli in the cockroach Blaberus craniifer burm. (Dictyoptera : Blaberidae): A morphometric study

In the growing antenna and antennal lobe of the cockroach, Blaberus craniifer (Dictyoptera : Blaberidae), the sizes of the various components, when expressed as a function of developmental stage, follow biphasic exponential kinetics. From first to last nymphal stage, the growth rates are constant. They vary widely with components. In the preimaginal phase, between the last nymphal and adult stages, these rates are generally not maintained, with the exception of deutocerebral cell bodies and some glomeruli. The rate of growth of the antenna decreases, whereas it increases for most glomeruli and antennal lobe.The growth rate of each identified glomerulus is characterized by a specific constant. The growth rate of glomerulus 106, the adult male macroglomerulus, is the same in male and female nymphs. During the preimaginal phase, however, it slightly decreases in the female and greatly increases in the male, resulting in adult dimorphism. The distribution of growth rates in the glomerular population is Gaussian. The slowest and most rapidly growing glomeruli are gathered into 3 spatially separate groups. Only one of them (the group comprising the macroglomerulus), includes both rapid and slow growing glomeruli. Glomerular growth in volume paralles growth of the antenna, allowing estimates of the number of antennal neurons per glomerulus to be determined.     

Anatomical and neurochemical classification of the antennal glomeruli in Drosophila melanogaster meigen (Diptera : Drosophilidae)

We are interested in how information about odours is processed in the antennal lobe of Drosophila melanogaster Meigen (Diptera : Drosophilidae). Our ultimate aim is to study how genes specify the development and functioning of the olfactory pathway. Such studies require a thorough knowledge of the anatomy, neurochemistry and development of the antennal system in normal files. This paper is a first attempt towards this end. Toluidine-methylene blue staining has revealed the presence of 22 glomeruli in the antennal lobe of Drosophila melanogaster. The number and size of glomeruli are invariant between individuals and the sexes. Fifteen of the glomeruli demonstrated specific uptake of choline, which is suggestive of some cholinergic innervation. In developmental studies, all glomeruli were found to be morphologically mature by 72 hr after formation of the white pupa. This study is a necessary first step towards an investigation of the role played by the glomeruli as functional units for odour coding.     

Morphological and developmental analysis of peripheral antennal chemosensory sensilla and central olfactory glomeruli in worker castes of Camponotus compressus (Fabricius, 1787)

The antennal lobes of different castes of the ant species Camponotus compressus show a marked diversity in the organization of their olfactory glomeruli. Notably, there is a significant difference in the number and size of glomeruli between the reproductives and the workers and among the different worker castes. In this report, we investigate the notion that these caste-specific differences in glomerular number might be accounted for, at least in part, by the differences in numbers of olfactory sensilla that target the antennal lobe. For this, we examine the number of sensilla on the antennal flagella of all the individual castes of C. compressus. This analysis reveals a striking correlation between sensillar number and the number of antennal glomeruli in a given caste. As a first step in investigating the causal mechanisms that might give raise to this correlation, we carry out an initial characterization of olfactory system development in the minor workers of C. compressus. We analyze the temporal pattern of innervations of the developing antennal lobe by olfactory sensory neuron axons. We document the development of the olfactory glomeruli in the antennal lobe during this process, which occurs during early pupal stages. Our findings provide the basis for future manipulative developmental studies on the role of sensory afferent number in glomerular development of different castes within the same species.     

Olfactory subsystems in the honeybee: sensory supply and sex specificity

The antennae of honeybee (Apis mellifera) workers and drones differ in various aspects. One striking difference is the presence of Sensilla basiconica in (female) workers and their absence in (male) drones. We investigate the axonal projection patterns of olfactory receptor neurons (ORNs) housed in S. basiconica in honeybee workers by using selective anterograde labeling with fluorescent tracers and confocal-microscopy analysis of axonal projections in antennal lobe glomeruli. Axons of S. basiconica-associated ORNs preferentially projected into a specific glomerular cluster in the antennal lobe, namely the sensory input-tract three (T3) cluster. T3-associated glomeruli had previously been shown to be innervated by uniglomerular projection (output) neurons of the medial antennal lobe tract (mALT). As the number of T3 glomeruli is reduced in drones, we wished to determine whether this was associated with the reduction of glomeruli innervated by medial-tract projection neurons. We retrogradely traced mALT projection neurons in drones and counted the innervated glomeruli. The number of mALT-associated glomeruli was strongly reduced in drones compared with workers. The preferential projections of S. basiconica-associated ORNs in T3 glomeruli together with the reduction of mALT-associated glomeruli support the presence of a female (worker)-specific olfactory subsystem that is partly innervated by ORNs from S. basiconica and is associated with the T3 cluster of glomeruli and mALT projection neurons. We propose that this olfactory subsystem supports parallel olfactory processing related to worker-specific olfactory tasks such as the coding of colony odors, colony pheromones and/or odorants associated with foraging on floral resources.     

Sexual dimorphism in neuronal projections from the antennae of silk moths (Bombyx mori,Antheraea polyphemus) and the gypsy moth (Lymantria dispar)

Summary The antennal lobe of both sexes of the silk moth Bombyx mori contains 55–60 ventrally located antennal glomeruli; in addition, that of the male contains a dorsal macroglomerular complex (MGC). A group of identifiable glomeruli consisting of two lateral large glomeruli (LLG) and four medial small glomeruli (MSG) is present in both sexes, but the LLG are greatly enlarged in the female. A MGC is also present in the male gypsy moth Lymantria dispar and male giant silk moth Antheraea polyphemus. The MGC in all of these species is organized into 3–4 distinct levels of glomeruli. Antennal sensory fibers were stained by cobalt backfills in B. mori, A. polyphemus, and L. dispar. Most fibers stained from cut long hairs (sensilla trichodea) projected to MGC in males and LLG in both sexes of B. mori. The distribution of fibers in the MGC of B. mori was topographically biased in that a majority of fibers from anterior branches projected medially in MGC while most fibers from posterior branches projected laterally or anteriorly. Terminal arborizations of single fibers were each restricted to a single glomerular level of the MGC. Fibers projecting to the posterior antennal center were frequently stained in cut-hair and control preparations, apparently by uptake of cobalt through intact sensilla on flagellar branches.     

Morphology of the reproductive system and antennal lobes of gynandromorphic and normal black cutworm moths,agrotis ipsilon (Hufnagel) (Lepidoptera : Noctuidae)

Sexually dimorphic characteristics of a bilaterally asymmetric gynandromorphic black cutworm moth, Agrotis ipsilon (Hufnagel), were compared with those of normal males and females. On one side of the body, the gynandromorphs wings were larger and darker than on the other side, and the antenna was filiform. On the other side of the body, the wings were smaller and lighter in color, and the antenna was pectinate. Females were usually larger and more pigmented than males. Female antenna were filiform and those of males pectinate. At the tip of the abdomen, the gynandromorph had 2 valves, as normal males do, but the one on the female side was smaller. The antennal lobes of the gynandromorphs brain included only ordinary glomeruli on the female side, and ordinary glomeruli plus a partially developed macroglomerular complex (MGC) at the base of the antenna on the male side. Normal female antennal lobes contained only ordinary glomeruli. Normal male antennal lobes contained ordinary glomeruli and a fully developed MGC, consisting of one large and 3 smaller glomeruli. In the gynandromorph, female reproductive organs were partially developed or absent. A portion of the oviduct was missing together with several ovarioles, and no spermatheca or seminal duct were found. The male reproductive track was complete, except for the paired structures, which in the gynandromorph were single. Normal females had paired accessory glands and ovaries, and single oviduct, bursa copulatrix, and spermatheca. Normal males had fused testes, paired accessory glands, and a single ejaculatory duct and aedeagus. The gynandromorph assumed a calling posture and attracted one male, but it did not respond to the pheromone from females.     

Glomerular interactions in olfactory processing channels of the antennal lobes

An open question in olfactory coding is the extent of interglomerular connectivity: do olfactory glomeruli and their neurons regulate the odorant responses of neurons innervating other glomeruli? In the olfactory system of the moth Manduca sexta, the response properties of different types of antennal olfactory receptor cells are known. Likewise, a subset of antennal lobe glomeruli has been functionally characterized and the olfactory tuning of their innervating neurons identified. This provides a unique opportunity to determine functional interactions between glomeruli of known input, specifically, (1) glomeruli processing plant odors and (2) glomeruli activated by antennal stimulation with pheromone components of conspecific females. Several studies describe reciprocal inhibitory effects between different types of pheromone-responsive projection neurons suggesting lateral inhibitory interactions between pheromone component-selective glomerular neural circuits. Furthermore, antennal lobe projection neurons that respond to host plant volatiles and innervate single, ordinary glomeruli are inhibited during antennal stimulation with the female’s sex pheromone. The studies demonstrate the existence of lateral inhibitory effects in response to behaviorally significant odorant stimuli and irrespective of glomerular location in the antennal lobe. Inhibitory interactions are present within and between olfactory subsystems (pheromonal and non-pheromonal subsystems), potentially to enhance contrast and strengthen odorant discrimination.     

Maxillary palp glomeruli and ipsilateral projections in the antennal lobe of<Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The antennal lobe was examined by Golgi-silver impregnation to differentiate the glomeruli depending on the source and types of inputs. Thirty-five of the 43 ‘identified’ olfactory glomeruli were Golgi-silver impregnated in the present study. Seven glomeruli compared to three, reported previously, were found to be targets of maxillary palp chemosensory neurons. These include glomeruli VA3, VC2, VM5, VA7m/VA7l of the ventral antennal lobe and DC2, DC3, DM5 of the dorsal antennal lobe. The number of glomeruli receiving the maxillary palp sensory projections tallies with the number ofDrosophila olfactory receptors (seven) reported to be expressed exclusively in the maxillary palp. Twenty-eight Golgi-impregnated glomeruli were found to receive input from the antennal nerve. The ratio of glomeruli serving the maxillary palp to those serving the antenna (∼1:5) matches with the ratio ofDrosophila olfactory receptors expressed in these two olfactory organs respectively. In addition to glomerulus V, glomeruli VP1-3, VL1, VL2a/2p and VC3m/3l were found to receive ipsilateral projections. Thus, additional ipsilateral glomeruli have been identified.     

Dimorphic antennal systems in gynandromorphic honey bees,Apis Mellifera l. (Hymenoptera: Apidae)

Gynandromorphic honey bees, Apis mellifera (Hymenoptera: Apidae), were examined to determine characteristic morphological and anatomical features of the antennal system. The antennae of gynandromorphic individuals are predominantly worker or drone-like. Hybrid antennae, composed of female and male tissues, occur only rarely (7 out of 188 examined antennae). Depending on the mosaic pattern of the head, both antennae can be drone-like or worker-like, or one can be drone-like and the other worker-like. Examination of the antennal lobes of six characteristic specimens revealed that antennal lobes, which are innervated by drone-like antennae, always have drone-specific enlarged tracts and macroglomerular complexes, whereas antennal lobes innervated by worker-like antennae always are composed of normally sized glomeruli. Thus, there is a strict correlation between the sexual morphology of the antennae and the sexual organization of the antennal lobe neuropil. In one antennal lobe, innervated by a hybrid antenna, we found a hypertrophied glomerulus, certainly homologous to one of the macroglomerular complexes in drone-like antennal lobes.jy 1999 Elsevier Science Ltd. All rights reserved.     

Anatomical organization of antennal-lobe glomeruli in males and females of the scarab beetle Holotrichia diomphalia (Coleoptera: Melolonthidae)

The glomerular organization of the primary olfactory brain center, the antennal lobe, was studied in males and females of Holotrichia diomphalia adults using serial histological sections labeled by the reduced silver-stain technique. The results revealed an apparent sexual dimorphism. Whereas an enlarged cap-shaped glomerulus was found at the antennal nerve entrance into the antennal lobe in males, no such unit was present in females. Also the size of the antennal lobe differed between the sexes, the antennal lobe of males being larger than that of females. We estimated the total number of glomeruli at approximately 60 units in the female antennal lobe. In males, we could discriminate only those glomeruli that were located in the anterior area of the antennal lobe.     

Caste and sex specific olfactory glomerular organization and brain architecture in two sympatric ant species Camponotus sericeus and Camponotus compressus (Fabricius, 1798)

We use monoclonal antibodies against synaptic proteins and anterograde tracing with neurobiotin to describe the architecture of the antennal lobes in different castes of two ant species – Camponotus sericeus and Camponotus compressus. The reproductives and worker classes are readily categorized based on size and external morphology. The overall organization of brain neuropile is comparable between castes with differences only in the visual ganglia. Males have a larger fraction of neuropile occupied by the medulla and lobula than females. In the diurnal species, C. sericeus these regions are more highly represented, than in the nocturnal species C. compressus. The most striking differences are in the antennal lobe where males possess a macroglomerulus, which is about ten times larger in volume than the other glomeruli; such a specialization is absent in females. Minor workers possess a significantly larger number of glomeruli than the majors despite the smaller overall volume of the lobe. These caste-specific differences occur mainly within glomerular clusters that receive input from sensory neurons that project in tracts – T4 and T5 – within the antennal nerve. The comparative anatomy of different castes of ants provides an entry point into a future systematic analysis of how divergent brain architectures can arise within a single species.     

Species and sexual differences in antennal lobe architecture and glomerular organization in two parasitoids with different degree of host specificity, Microplitis croceipes and Cotesia marginiventris

The endoparasitic wasps (Hymenoptera: Braconidae), Microplitis croceipes (specialist) and Cotesia marginiventris (generalist), are parasitoids of lepidopteran larvae and differ in their degree of host specificity. Recent studies have reported key differences between the two species in the abundance of antennal olfactory sensilla and their response to host-related volatiles. Here, we have compared antennal lobe architecture and glomerular organization in the two parasitoid species by using a combination of axonal tract tracing techniques and confocal microscopy. In M. croceipes, the medial half of the antennal lobe is larger with a greater number of glomeruli compared with the lateral half, whereas in C. marginiventris, the lateral half is larger than the median half. The volume of the antennal lobe is approximately 2.5 times greater in M. croceipes than in C. marginiventris. However, the number of glomeruli per antennal lobe is only slightly higher in M. croceipes (females: 219–222; males: 220–224) than in C. marginiventris (females: 192–194; males: 193–196). A comparison of males and females within each species demonstrated a striking sexual difference in terms of an enlarged glomerulus (macroglomerulus or MG) at the entrance of the antennal nerve and of a complex of 3–4 MG (CMG) in the posterior region of the antennal lobe of males of both species. Being specific to males, both the MG and CMG might be involved in the detection of female-related odor.     

Phenotypic plasticity in number of glomeruli and sensory innervation of the antennal lobe in leaf‐cutting ant workers (A. vollenweideri)

In the leaf‐cutting ant Atta vollenweideri, the worker caste exhibits a pronounced size‐polymorphism, and division of labor is dependent on worker size (alloethism). Behavior is largely guided by olfaction, and the olfactory system is highly developed. In a recent study, two different phenotypes of the antennal lobe of Atta vollenweideri workers were found: MG‐ and RG‐phenotype (with/without a macroglomerulus). Here we ask whether the glomerular numbers are related to worker size. We found that the antennal lobes of small workers contain ～390 glomeruli (low‐number; LN‐phenotype), and in large workers we found a substantially higher number of ～440 glomeruli (high‐number; HN‐phenotype). All LN‐phenotype workers and some small HN‐phenotype workers do not possess an MG (LN‐RG‐phenotype and HN‐RG‐phenotype), and the remaining majority of HN‐phenotype workers do possess an MG (HN‐MG‐phenotype). Using mass‐staining of antennal olfactory receptor neurons we found that the sensory tracts divide the antennal lobe into six clusters of glomeruli (T1–T6). In LN‐phenotype workers, ～50 glomeruli are missing in the T4‐cluster. Selective staining of single sensilla and their associated receptor neurons revealed that T4‐glomeruli are innervated by receptor neurons from the main type of olfactory sensilla, the Sensilla trichodea curvata. The other type of olfactory sensilla (Sensilla basiconica) exclusively innervates T6‐glomeruli. Quantitative analyses of differently sized workers revealed that the volume of T6 glomeruli scales with the power of 2.54 to the number of Sensilla basiconica. The results suggest that developmental plasticity leading to antennal‐lobe phenotypes promotes differences in olfactory‐guided behavior and may underlie task specialization within ant colonies. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 70: 222–234, 2010.     

Three-dimensional antennal lobe atlas of the oriental fruit moth, <Emphasis Type="Italic">Cydia molesta</Emphasis> (Busck) (Lepidoptera: Tortricidae): comparison of male and female glomerular organization

The oriental fruit moth Cydia molesta is an important pest and the behavioural role of olfactory signals such as pheromones and plant volatiles have been studied extensively in both sexes. To understand odour processing further, however, detailed knowledge of the anatomy of the olfactory system is crucial. In the present study, an atlas of the antennal lobe (AL) is presented based on the three-dimensional reconstructions of both ALs of three male and three female brains by means of neuroanatomical and computational approaches. We identified 48–49 "ordinary" glomeruli and one large glomerulus situated at the entrance of the antennal nerve in males, and 49–52 "ordinary" glomeruli and one large glomerulus in the ventro-medial part of the AL in females. Anomalous supernumerary, anomalous missing and sexually dimorphic glomeruli were found in the studied individuals in greater numbers than in other lepidopteran species. Male and female maps were compared with respect to glomerular size and position with 45 glomeruli being matched, indicating a conserved glomerular pattern between the sexes. Three additional glomeruli were sexually dimorphic in size and five male-specific and six female-specific glomeruli were also found. Palp backfills resulted in the staining of a unique glomerulus in both sexes identified as the sexually dimorphic glomerulus 45. This glomerulus was never stained from antennal backfills, which stained the other glomeruli of the AL. The three-dimensional atlas can now be used to elucidate the functional role of individual glomeruli in both sexes of C. molesta. Nélia Varela and Louise Couton contributed equally to this work. This study was supported by research grants from INRA (Projet Jeune Equipe and Projet S.P.E.) to S.A. and J.P.R. and by the Spanish Ministry of Science and Technology (research grant AGL2004-05812/AGR to J.A. and C.G., Spanish Science and Education Department, MEC). N.V. was financed by fellowship no. BES-2005-7605 (MEC, Spain).     

Organization of the antennal lobe in the queen honey bee,Apis mellifera L. (Hymenoptera : Apidae)

Antennal afferent pathway topography was studied in the queen honey bee, Apis mellifera L. (Hymenoptera : Apidae) by staining with cobalt chloride applied directly to the cut antennal axons. Antennal lobe organization in the queen was compared with those in worker and drone bees. The organization is similar in queen and worker bees. For the first time in a female insect the possible existence of a macroglomerulus is shown, which may be involved in the processing of species-specific information. A comparative quantitative neuromorphological study of the glomeruli was performed between young queens (8-day old) and 1-yr-old queens. The mean volume of the glomeruli is 46% greater in the older queens.     

Experimentally induced puromycine aminonucleoside nephrosis (PAN) in rats: evaluation of angiogenic protein platelet-derived endothelial cell growth factor (PD-ECGF) expression in glomeruli

Background

In experimentally induced puromycine aminonucleoside nephrosis (PAN) animal models, nephrotic syndrome with minimal change disease and focal and segmental sclerosis-like nephritis similar to that in human is demonstrated; however, the real mechanism of PAN is not yet elucidated. Platelet derived endothelial cell growth factor (PD-ECGF), an endothelial mitogen protein, is believed to take part in microvessel formation and in stimulation of angiogenesis and its expression has not been totally demonstrated in PAN rats yet. In this study, we aimed to examine PD-ECGF expression in acute and chronic PAN induced in rats and find out the association between its expression and the stages of angiogenesis in kidney.

Methods

For the experiment, twenty-four Male Wistar Albino rats were used and divided into four groups; control group (n = 6), pre-proteinuria group (n = 6), acute group (n = 6) and chronic group (n = 6). We compared statistically all data by One-way ANOVA Test followed by Dunn Multiple Comparison Test.

Results

Proteinurea levels in control and pre-proteinuria groups were not statistically different; however, it was remarkably higher in the acute nephrosis group and significantly greater in the chronic nephrosis group than control group (p < 0.0025). In pre-proteinuria group, the serum albumin and creatinine clearances also did not significantly differ from the control group. On the other hand, in the acute and chronic nephrosis groups, serum albumin and creatinine clearances progressively decreased (p < 0.05). In our immunohistochemical studies, we showed elevated PD-ECGF expression in glomeruli of acute and chronic PAN rats. Microscopic and ultrastructural appearances of the glomeruli of acute and chronic PAN showed various sequential steps of angiogenesis, macrophages and immature capillaries with primitive lumens and apoptotic endothelial cells in the increased mesangial matrix.

Conclusions

It is reported that acute and chronic PAN progressively increase PD-ECGF expression and following induction of angiogenesis in the affected glomeruli.     

Postembryonic development of the antennal lobes in Periplaneta americana L.

Summary The postembryonic development of the antennal lobes of Periplaneta americana L. was examined with light- and electron-microscopical methods. There is no difference in the number of glomeruli and neurons in the antennal lobes of larval and adult animals. At hatching, the first larva already possesses the adult number of approximately 125 glomeruli and 500 to 560 deutocerebral neurons in the dorsolateral cell group of each antennal lobe. During postembryonic development the volume of the deutocerebral neurons increases three- to fourfold. The glomeruli of the first larva have about 7 % of the volume of the corresponding adult glomeruli. Since number, pattern, and size ratio of glomeruli (with the exception of the macroglomerulus) are constant in all larval stages and adult animals, it is possible to identify individual glomeruli. During the whole postembryonic development the ordinary glomeruli show a continuous volume increase, which parallels the increase in antennal sensory input. The macroglomerulus develops by way of special growth of two to four neuropil units, but not before the last three to four larval stages and only in males. Its growth precedes the formation of antennal pheromone receptors during the final molt; these receptors are known to project into the macroglomerulus. The development of the macroglomerulus in the last larval stages of the male may be caused by a genetically fixed growth program of specific deutocerebral neurons.Supported by the Deutsche Forschungsgemeinschaft (Scha 291/1)     

New insights into an ancient insect nose: the olfactory pathway of Lepismachilis y-signata (Archaeognatha: Machilidae)

Hexapods most likely derived from an aquatic ancestor, which they shared with crustaceans. During the transition from water to land, their sensory systems had to face the new physiological demands that terrestrial conditions impose. This process also concerns the sense of smell and, more specifically, detection of volatile, air-borne chemicals. In insects, olfaction plays an important role in orientation, mating choice, and food and host finding behavior. The first integration center of odor information in the insect brain is the antennal lobe, which is targeted by the afferents from olfactory sensory neurons on the antennae. Within the antennal lobe of most pterygote insects, spherical substructures called olfactory glomeruli are present. In order to gain insights into the evolution of the structure of the central olfactory pathway in insects, we analyzed a representative of the wingless Archaeognatha or jumping bristletails, using immunocytochemistry, antennal backfills and histological section series combined with 3D reconstruction. In the deutocerebrum of Lepismachilis y-signata, we found three different neuropil regions. Two of them show a glomerular organization, but these glomeruli differ in their shape from those in all other insect groups. The connection of the glomerular neuropils to higher brain centers remains unclear and mushroom bodies are absent as reported from other archaeognathan species. We discuss the evolutionary implications of these findings.     

Physiology and antennal lobe projections of olfactory receptor neurons from sexually isomorphic sensilla on male <Emphasis Type="Italic">Heliothis virescens</Emphasis>

The neurophysiology and antennal lobe projections of olfactory receptor neurons (ORNs) within sexually isomorphic short trichoid sensilla of male Heliothis virescens (Noctuidae: Lepidoptera) were investigated using cut-sensillum recording and cobalt-lysine staining. A total of 202 sensilla were sorted into 14 possible sensillar categories based on odor responses and physiology of ORNs within. Seventy-two percent of the sensilla identified contained ORNs stimulated by conspecific odors. In addition, a large number of ORNs were specifically sensitive to ß-caryophyllene, a plant-derived volatile (N = 41). Axons originating from ORNs associated with individual sensilla were stained with cobalt lysine (N = 67) and traced to individual glomeruli in the antennal lobe. ORNs with responses to female sex pheromone components exhibited similar axonal projections as those previously described from ORNs in long sensilla trichodea in male H. virescens. Antennal lobe axonal arborizations of ORNs sensitive to hairpencil components were also located in glomeruli near the base of the antennal nerve, whilst those sensitive to plant odorants projected to more medial glomeruli. Comparisons with ORNs described from female H. virescens supports the notion that glomeruli at the base of the antennal nerve are associated with conspecific and interspecific odorants, whereas those located medially are associated with plant volatiles.