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.     

Morphology of the nervous and muscular systems in the heads of pedicellariae from the sea urchin Echinus esculentus L

Light and electron microscopy reveal that simple receptor cells in the jaw epithelium of sea urchin pedicellariae are connected by nerve tracts to the neuropile that coordinates jaw movements. The muscles responsible for jaw opening and closure and for flexion of the stem are all innervated in this neuropile. At least two types of vesicles occur at the simple synapses between neurone profiles and at neuromuscular junctions. The muscles include both striated and smooth fibres; however, their distribution varies according to pedicellaria type, and an unexpected arrangement exists in trifoliate pedicellariae.     

Spatial organization of the antennal lobe in Cylindroiulus punctatus (Leach) (Myriapoda : Diplopoda)

The topography of the antennal afferent pathway has been studied in detail for the first time in a myriapod, Cylindroiulus punctatus, by cellular staining, following localized application of cobalt chloride to the cut end of one antenna. At the lateral entrance of the sensory antennal nerve into the deutocerebrum, 3 main groups of tracts have been distinguished. In the antennal lobe, there are two groups of glomeruli: a ventral group of 3 glomeruli and a dorsal group of 15 or 16 glomeruli. The number, position and dimensions of the glomeruli indicate that the glomerular organization is globally invariant (5 individuals).     

Comparative study of the antennal lobes and their afferent pathway in the worker bee and the drone (Apis mellifera)

Summary The topography of the antennal afferent path-ways was studied comparatively in the worker bee and the drone of Apis mellifera L. by cellular marking, following localized application of cobalt chloride to the cut end of one antenna. This study dealt principally with the first relay of the afferent pathway in the glomeruli of the antennal lobe. The counting and measurement of all the glomeruli were performed on 5 worker bees and 5 drones. An important sexual dimorphism, represented by 4 large and easily identifiable glomerular complexes, was demonstrated in the drone. In both worker bee and drone, four main regions of the glomerular neuropil were distinguished according to corresponding afferent bundles. The worker possessed 166 glomeruli and the drone 103. The number, position and dimensions of the glomeruli indicated that the glomerular organization was unvarying in worker bees and in drones. Concerning the internal structure of the glomeruli, two types were distinguished: the great majority (95%) exhibited a cortical layer, whereas in the 7 posterior glomeruli the synaptic fields of association seemed to be scattered throughout the whole volume. The main results of this work (glomerular invariance, sexual dimorphism) support the hypothesis of the functional unit of the glomeruli.Unité de Recherche Associée au CNRS, UA 483     

The anatomical pathways for antennal sensory information in the central nervous system of the cricket, Gryllus bimaculatus

Antennae are one of the major organs to detect chemo- and mechanosensory cue in crickets. Little is known how crickets process and integrate different modality of information in the brain. We thus used a number of different anatomical techniques to gain an understanding of the neural pathways extending from the antennal sensory neurons up to centers in the brain. We identified seven antennal sensory tracts (assigned as T1?C7) utilizing anterograde dye filling from the antennal nerve. Tracts T1?CT4 project into the antennal lobe (AL), while tracts T5 and T6 course into the dorsal region of the deutocerebrum or the suboesophageal ganglion, and finally, tract T7 terminates in the ventral area of flagellar afferent (VFA). By analyzing autofluorescence images of the AL, we identified 49 sexually isomorphic glomeruli on the basis of shape, relative position and size. On the basis of our sensory-tract data, we assigned the glomeruli into one of four separate groups. We then three-dimensionally reconstructed the internal structures in the AL (glomeruli) and the VFA (layers). Next in the protocerebrum, we identified both the tracts and their terminations from the AL and VFA. We found that 10 tracts originate in the AL, whereas there are at least eight tracts from the VFA. Several tracts from the AL share their routes with those from the VFA, but their termination areas are segregated. We now have a better anatomical understanding of the pathways for the antennal information in cricket.     

Olfactory perception and learning in the honey bee (Apis mellifera): calcium imaging in the antenna lobe

Honey bees are a key-model in the study of learning and memory, because they show considerable learning abilities, their brain is well described and is accessible to a wide range of physiological recordings and treatments. We use in vivo calcium imaging to study olfactory perception in the bee brain, and combine this method to appetitive olfactory conditioning to unravel the neural substrates of olfactory learning. Odours are detected by receptor neurons on the antennae. Each receptor neuron projects to the first-order neuropile of the olfactory pathway, the antennal lobe, connecting to projection neurons in one of its 160 functional units, the glomeruli. In calcium imaging experiments, each odour elicits a particular activity pattern of antennal lobe glomeruli, according to a code conserved between individuals. The antennal lobe is also a site where the olfactory memory is formed. Using optical imaging, two studies have shown modulations of odour representation in the antennal lobe after learning, with different effects depending on the type of conditioning used. While simple differential conditioning (A + B- training) showed an increased calcium response to the reinforced odour, side-specific conditioning (A + B-/B + A- training) decorrelated the calcium responses of odours between brain sides. This difference may owe to the formation of different memories, which will be addressed in future work. By specifically staining antennal lobe neuronal subpopulations, we hope to be able in the future to study synaptic plasticity in the honey bee.     

The antennal lobe of Libellula depressa (Odonata,Libellulidae)

Here we describe the antennal lobe of Libellula depressa (Odonata, Libellulidae), identified on the basis of the projections of the afferent sensory neurons stemming from the antennal flagellum sensilla. Immunohistochemical neuropil staining as well as antennal backfills revealed sensory neuron terminal arborizations covering a large portion of the antennal lobe. No clear glomerular structure was identified, thus suggesting an aglomerular antennal lobe condition as previously reported in Palaeoptera. The terminal arbors of backfilled sensory neurons do, however, form spherical knots, probably representing the connections between the few afferent neurons and the antennal lobe interneurons. The reconstruction revealed that the proximal part of the antennal nerve is divided into two branches that innervate two spatially separated areas of the antennal lobe, an anterioventral lobe and a larger posteriodorsal lobe. Our data are consistent with the hypothesis that one tract of the antennal nerve of L. depressa contains olfactory sensory neurons projecting into one of the sublobes, while the other tract contains thermo-hygroreceptive neurons projecting into the other sublobe.     

Geometric considerations of nitric oxide-cyclic GMP signalling in the glomerular neuropil of the locust antennal lobe

Using NADPH-diaphorase staining as a marker for nitric oxide (NO) synthase and an antiserum against cyclic GMP, we recently reported the anatomical distribution of nitric oxide donor and target cells in the antennal lobe, the principal olfactory neuropile of the locust. The most striking NADPH-diaphorase activity in the olfactory pathway is concentrated in a cluster of intensely stained local interneurons innervating the glomeruli. After incubation of tissue in a nitric oxide donor and inhibition of phospodiesterase activity, neurons of this cluster expressed cyclic GMP-immunoreactivity in the cell body and neurites. Here we examine the importance of the arrangement of NO donor and target cells for information processing in the glomeruli. The cellular organization of the NO-cyclic GMP system in olfactory interneurons, and the dendritic branching pattern, suggest that nitric oxide may not only act as intercellular, but also as intracellular messenger molecule in the glomerular neuropile of the antennal lobe. <br>     

Developmental study of afferented and deafferented bee antennal lobes.

The role of antennal sensory projections on the ontogeny of the bee antennal lobe was analyzed using both light and transmission electron microscopy. Normal and deafferented developing antennal lobes were examined. The results obtained show that (1) initiation of synaptogenesis in the antennal lobe is independent of the arrival of sensory inputs; (2) sensory inputs are necessary for setting up the glomerular antennal lobe organization; (3) regressive events, such as the reduction of synapse density, occur during the development of the antennal lobe; and (4) glomeruli formation appears as related to glia development.     

The Ultrastructure of the Nervous System of Gyratrix hermaphroditus (Turbellaria, Rhabdocoela)

The peripheral nervous system and the synapses of G. hermaphroditus are studied with the electron microscope. There is a submuscular as well as a subepithelial plexus. The subepithelial plexus is found among the muscles and between the muscles and the basement membrane. It consists of fibres containing large lucent and lysosome-like vesicles and fibres with only small lucent (synaptic) vesicles. In the deeper lying submuscular plexus also dense and dense-cored vesicles occur in the fibres. Cell bodies are not observed in the plexuses. The separate nerve supplies of the pharynx and the gonads contain nerve cells of the neurosecretory type. Fibres of the same kinds as in the brain are also seen here. The synapses in the neuropile are of two kinds. 1. Symmetrical synapses with an additional presynaptic network are most common. 2. Synapses without thickenings of membranes are observed between lateral membranes of neurites. In the peripheral nervous system are two other kinds of synapses also observed. 1. Asymmertical synapses with a denser and wider postsynaptic thickening and 2. neuromuscular junctions. Neurites containing accumulations of small vesicles against the basement membrane are also described. The organization of the peripheral nervous system is described and discussed in relation to the systematic position of G. hermaphroditus.     

Developmental study of afferented and deafferented bee antennal lobes

The role of antennal sensory projections on the ontogeny of the bee antennal lobe was analyzed using both light and transmission electron microscopy. Normal and deafferented developing antennal lobes were examined. The results obtained show that (1) initiation of synaptogenesis in the antennal lobe is independent of the arrival of sensory inputs; (2) sensory inputs are necessary for setting up the glomerular antennal lobe organization; (3) regressive events, such as the reduction of synapse density, occur during the development of the antennal lobe; and (4) glomeruli formation appears as related to glia development.     

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.     

Distribution of glutamate decarboxylase-like immunoreactivity in the sixth abdominal ganglion of the cockroach Periplaneta americana

Summary An antiserum against glutamate decarboxylase (GAD) of the rat brain was used to locate GAD activity in sections of the nervous system of the cockroach, Periplaneta americana. The sixth abdominal ganglion was chosen because electrophysiological evidence suggests the presence of GABAergic inhibitory synapses in the cereal-giant interneuron system. Groups of somata and numerous fibres and tracts were positively labelled by the GAD antiserum. A posterior group of labelled somata could be identified close to the entry of the cereal nerves. A line of somata clusters lay along a ventro-lateral furrow. Another discrete row of GAD-like cells was located dorso-laterally. Some small cells among the dorsal unpaired neurons were labelled. A small central group appeared under these cells. An abundance of GAD-like processes and transversal tracts were found within the neuropile. The different systems of GABAergic inhibitors in the ganglion are discussed; in particular we show that the fibres of cereal nerve X are not labelled. This demonstrates that the latter act on the giant fibres via interneurons. We suggest that the group that sends axons into the overlapping region between the cereal nerve and the giant fibre could be the inhibitory interneurons involved in this system.     

Glial patterning during postembryonic development of central neuropiles in the brain of the honeybee

 Glial cells are involved in several functions during the development of the nervous system. To understand potential glial contributions to neuropile formation, we examined the cellular pattern of glia during the development of the mushroom body, antennal lobe and central complex in the brain of the honeybee. Using an antibody against the glial-specific repo-protein of Drosophila, the location of the glial somata was detected in the larval and pupal brain of the bee. In the early larva, a continuous layer of glial cell bodies defines the boundaries of all growing neuropiles. Initially, the neuropiles develop in the absence of any intrinsic glial somata. In a secondary process, glial cells migrate into defined locations in the neuropiles. The corresponding increase in the number of neuropile-associated glial cells is most likely due to massive immigrations of glial cells from the cell body rind using neuronal fibres as guidance cues. The combined data from the three brain regions suggest that glial cells can prepattern the neuropilar boundaries. Received: 3 November 1996 / Accepted: 7 February 1997     

光肩星天牛的脑部结构

通过Mallory和HE染色,对光肩星天牛Anoplophora glabnpenn脑部显微结构进行了观察.结果表明,光肩星天牛的脑由前脑、中脑、后脑三部分组成.前脑叶髓层包括一对蕈形体、一个中央体、一个脑桥体和一对附叶,其中每个蕈形体仅有一个帽状的蕈体冠.中脑触角叶较大,由九簇放射状排列的触角神经束组成,中央的一束较粗,说明其嗅觉发达.后脑较小.     

Central projections of a homoeotic regenerate, antennapedia, in a stick insect, Carausius morosus (Phasmida)

Homoeotic appendages provide a system for the analysis of neural path-finding in which the appendage is mismatched with its segmented ganglion. Central projections of sensory neurons from homoeotic antennapedia regenerates induced by antennal amputation in the stick insect, Carausius morosus, are described. The majority of afferent axons project to the olfactory lobe as in the normal antennal nerve, but they do not give rise to compact glomeruli. Nor does the form of the projection resemble that of leg sensory nerves in thoracic ganglia. The projection of antennapedia regenerate neurons in Carausius resembles the antennapedia mutant of Drosophila except that some primary afferents bypass the olfactory lobe and take several courses through the brain, sometimes reaching distant contralateral areas. It appears that these wandering fibers, having bypassed the olfactory lobe, tend to follow established tracts and to arborize or to deviate at circumscribed synaptic areas. The behavioral evidence for sensory input from antennapedia regenerates is equivocal.     

Intrinsic organization of snake dorsomedial cortex: an electron microscopic and golgi study.

The cellular populations present in dorsomedial cortex in the snakes Constrictor constrictor, Natrix sipendon and Thamnophis sirtalis are described at the light microscopic level using Nissl and Golgi preparations as well as at the ultrastructural level. This area plays a central role in cortical organization in snakes by participating in major commissural and association projections. Systematic analyses of Golgi preparations indicate that five populations of neurons are present in dorsomedial area and have a preferential laminar distribution. Layer 1 stellate cells have somata positioned in the center of the outermost cortical layer, layer 1. Their dendrites are confined to this layer. Double pyramidal cells have their somata loosely packed in layer 2. Their dendrites bear a moderate population of spines, ascending through layer 1 to the pial surface and descending partially through layer 3. Some double pyramidal cells have somata displaced downwards into the upper third of layer 3. These neurons closely resemble the layer 2 double pyramidal cells. Layer 3 stellate cells have somata positioned in the middle third of layer 3. Their dendrites extend in all directions throughout layer 3 and through layer 2 into layer 1. Finally, horizontal cells have their somata positioned deep in layer 3, near the ventricle, and dendrites aligned concentric with the ventricle. Comparison of the organization of the known afferents to dorsomedial area with the distribution of the five cell types suggests that the laminations of both afferent fibres and dorsomedial neurons places specific neuronal populations in synaptic contact with specific sets of afferents.     

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.     

Immunocytochemical identification of neuroactive substances in the antennal lobe of the male silkworm moth Bombyx mori

As a first step towards understanding the functional role of neuroactive substances in the first olfactory center of the male silkworm moth Bombyx mori, we carried out an immunocytochemical identification of antennal lobe neurons. Antibodies against gamma-aminobutyric acid (GABA), FMRFamide, serotonin, tyramine and histamine were applied to detect their existence in the antennal lobe. In the present immunocytochemical study, we clarified four antenno-cerebral tracts from their origin and projection pathways to the protocerebrum, and revealed the following immunoreactive cellular organization in the antennal lobe. 1) Local interneurons with cell bodies in the lateral cell cluster showed GABA, FMRFamide and tyramine immunoreactivity. 2) Projection neurons passing through the middle antenno-cerebral tract with cell bodies in the lateral cell cluster showed GABA and FMRFamide immunoreactivity. Projection neurons passing through the outer antenno-cerebral tract with cell bodies in the lateral cell cluster showed FMRFamide immunoreactivity. 3) Centrifugal neurons passing through the inner antenno-cerebral tract b with cell bodies located outside the antennal lobe showed serotonin and tyramine immunoreactivity. Our results revealed basic distribution patterns of neuroactive substances in the antennal lobe and indicated that each projection pathway from the antennal lobe to the protocerebrum contains specific combination of neuroactive substances.