The subgenus Persicargas (Ixodoidea: Argasidae: Argas): A. (P.) arboreus central nervous system anatomy and histology

The anatomy and histology of the adult Argas (Persicargas) arboreus central nervous system are described and compared with these properties in other ticks. The single, integrated, central nerve mass (CNM) is formed by a fused supra-esophageal part (protocerebrum, cheliceral ganglia, palpal ganglia, and stomodeal pons) and a subesophageal part (4 pairs of pedal ganglia and the complex opisthosomatic ganglion). Single peripheral nerves (pharyngeal and recurrent) and paired peripheral nerves (compound protocerebral, cheliceral, palpal, pedal and opisthosomatic) extend from the CNM to body organs and appendages. Optic nerves, described in other Argas species, are not found in A. (P.) arboreus. Histologically, the CNM is enclosed by a thin-walled periganglionic blood sinus and invested by a collagenous neural lamella followed by a perineurial layer composed of glial cells and containing fine reticular spaces, a cortical layer of association, motor and neurosecretory cell bodies and glial cells, and inner neuropile regions of fiber tracts forming 5 horizontal levels of connectives and commissures.     

Changes in the amount of the diapause factor in the subesophageal ganglion during development of the silkworm, Bombyx mori

Changes in the diapause factor content of the subesophageal ganglion of the silkworm were examined from the viewpoint of sex and voltinism differences. The diapause factor content was comparatively low from the 4th larval ecdysis to the larval-pupal ecdysis, irrespective of sex and voltinism. However, remarkable changes occurred after the larval-pupal ecdysis. An interesting finding is that the diapause factor content in the female diapause egg-producer decreased gradually with pupal-adult development, but in the male diapause egg-producer as well as in the non-diapause egg-producer it increased up to the half-way stage in the pupal-adult development. This suggests that the diapause factor is not secreted from the subesophageal ganglion of the male pharate adult of the diapause egg-producer. This finding was confirmed by implantation experiments using brain-subesophageal ganglion complex or only subesophageal ganglion.     

CNS microstructure in the wandering wolf spider Arctosa kwangreungensis (Araneae: Lycosidae)

The supraesophageal ganglion of the wolf spider Arctosa kwangreungensis is made up of a protocerebral and tritocerebral ganglion, whereas the subesophageal ganglionic mass is composed of a single pair of pedipalpal ganglia, four pairs of appendage ganglia, and a fused mass of abdominal neuromeres. In the supraesophageal ganglion, complex neuropile masses are located in the protocerebrum which include optic ganglia, the mushroom bodies, and the central body. Characteristically, the only nerves arising from the protocerebrum are the optic nerves, and the neuropiles of the principal eyes are the most thick and abundant in this wandering spider. The central body which is recognized as an important association center is isolated at the posterior of the protocerebrum and appears as a complex of highly condensed neurons. These cells give off fine parallel bundles of axons arranged in the mushroom bodies. The subesophageal nerve mass can be divided into two main tracts on the basis of direction of the neuropiles. The dorsal tracts are contributed to from the motor or interneurons of each ganglion, whereas the ventral tracts are from incoming sensory axons.     

The allometry of the central nervous system during the postembryonic development of the spider Eratigena atrica

During ontogenesis, the size of a spider body, tissues and organs increases dramatically. The aim of the study was to estimate changes in the central nervous system of postembryonic stages of Eratigena atrica and compare them with the literature data on species differing in behavioural traits. Allometric analysis involved evaluation of histological slides embedded in paraffin and stained with hematoxylin and eosin. The reduced major axis regression (RMA) was applied to find allometric relationships between the volumes of the particular parts of the body. All the measured parts of the central nervous system (CNS) were negatively allometrically related to the volume of the prosoma, showing that the increment of the CNS was lower than that of the entire body. The growth of the brain was negatively allometrically related to the growth of the CNS but the increment of the subesophageal ganglion was greater than that of the CNS, exhibiting a positive allometry. Within both these structures, the increase in neuropil volume was greater than the growth of the cortex (cell body rind). Thus, in postembryonic development, the share of the subesophageal ganglion and neuropil in the total volume of the CNS increased, whereas that of the brain and cortex decreased. The mode of the CNS development in E. atrica is similar to that observed in other arthropods, including Argiope aurantia, a spider of different ecology and behaviour.     

Immunohistochemical Localization of Annetocin, an Earthworm Oxytocin-Related Peptide, and Identification and Ultrastructural Characteristics of the Annetocin-Secretory Cells in the Oligochaete Earthworm Eisenia foetida

Annetocin is an egg-laying-inducing oxytocin-related peptide which we have previously isolated from the earthworm, Eisenia foetida. Here we report the results of immunohistochemical and ultrastructural studies on annetocin-secretory cells in the earthworm. Annetocin-immunoreactive (IR) cell-somata were located mainly at the ventro-lateral side of the subesophageal ganglion. Only four annetocin-IR cells were seen in the cerebral ganglion. Some annetocin-IR cells displayed unipolar-like structure with a process directing to the core region (the neuropile) of the ganglion. Annetocin-IR fibers were also observed in the neuropile of the ventral ganglia and the ventral nerve cord between the 4th and the 30th segments including the clitellum, but not in the posterior segments (31-55th). The number of annetocin-IR fibers decreased from the 4th to the 30th segment. The annetocin-secretory cells were identified by the immunogold staining, and filled with gold-labeled vesicles, 200-250 nm in diameter, which included moderately electron dense material. The annetocin-secretory cells possessed a euchromatic nucleus, well-developed rough endoplasmic reticulum and Golgi apparatus. Some of the annetocin-secretory cells were found to form a neurohemal-like structure, where somata or fibers with loose glial investment came in contact with the coelomic space at the ventral side of the subesophageal ganglion. The results suggest that annetocin is a neuropeptide produced and secreted by the neuron in the cerebral and subesophageal ganglia of the earthworm.     

The development of the insect nervous system. I. An analysis of postembryonic growth in the terminal ganglion of Acheta domesticus

This study describes the post-embryonic growth of the terminal ganglion in Acheta domesticus in terms of volume and cell number. All measurements were made at the beginning of each instar from hatching until the final moult on animals reared under controlled conditions. The terminal ganglion increases about 40-fold in volume from 2 × 10⁶ μ³ in the first instar to 85 × 10⁶ μ³ in the adult. A double logarithmic plot of ganglion volume against body weight shows that the ganglion volume is a function of body weight to the 0.56 power. Initially the neuropile grows at a greater rate than the cortex; in later stages they increase at the same rate. Increase in cell number was determined from serial sections. The total number of cells, based on corrected nuclear counts, increases from 3,400 to 20,000. There is little or no increase in the number of neurons. There are approximately 2,000 association neurons and 100 motor neurons in all stages. The number of glial cells increase from 1,000 to 17,000. Their multiplication rate appears to be related to the increase in neuron volume. Despite the increase in glial cell number, increase in cell volume is primarily responsible for the increase in total volume of the ganglion.     

The glycosaminoglycans of the thoracic ganglia of the nymphal stages of the cockroach, Periplaneta americana, and the locust, Locusta migratoria: A histochemical study

The glycosaminoglycans of the connective tissue matrices of the developing meso- and metathoracic ganglia of locusts and cockroach nymphs have been characterized. The neural lamella contains only chondroitin sulphate in the early nymphs, but gradually keratan sulphate accumulates in the later nymphs. The glial lacunar system cannot be detected histochemically in first instar locust nymphs, but it can be seen in the youngest cockroach nymphs; it is clearly visible in the older nymphs of both species. It contains only hyaluronate.A stereological analysis of the developing meso- and meta-thoracic ganglia of the cockroach shows that the relative volumes occupied by the neurones, neuropile, glial cells and glial lacunar system change during post-embryonic development.The physiological functions of the glycosaminoglycans in the neural lamella and glial system are discussed.     

The nervous system of the tube-worm Chaetopterus variopedatus (Polychaeta)

Silver impregnation of serial histological sections of the tubeworm Chaetopterus variopedatus revealed the presence of a subepidermal nervous system. The anterior nervous system is delimited by the first 11 segments and comprises (1) two dorsolateral cerebral ganglia and lateral instead of ventral nerve cords which are widely separated and thus connected by unusually long commissures, (2) a pharyngeal ganglion in the fourth segment which is connected to the cerebral ganglia by pharyngeal nerves and constitutes along with the pharyngeal plexus a stomatogastric or enteric nervous system, and (3) small, presumably segmental ganglionic swellings along the lateral nerve cords from which emerge commissures and parapodial nerves. No subesophageal ganglion or periesophageal connective could be identified. The lateral nerve cords converge toward the midline in the 12th segment to form the posterior nervous system comprising a pair of ventromedian nerve cords with their repetitive segmental ganglia from which emerge numerous short commissures and three segmental nerves coursing toward the dorsal and ventral regions of parapods and toward the neuropod. Light and electron microscopic investigations of cerebral and segmental ganglia showed an arrangement of inner neuropile and of unipolar neuron somata at the periphery. The neuropile comprises numerous neurites ranging in diameter from 0.5 to 10 μm and making polarized or symmetrical synaptic junctions with each other. The pharyngeal ganglion consists of a similar neuropile and of a large mass of cell bodies which is traversed by an elaborate network of sinuses and harbors three types of neurosecretory cells in addition to the conventional neuron somata. These findings are interpreted in the framework of the highly specialized morphological features and habits of Chaetopterus, and the welldeveloped stomatogastric system is considered to be related to control of the feeding activities.     

Distribution and ultrastructure of neurosecretory cells in the cerebral ganglion of the earthworm

Neurosecretory (Nsy) cells within the cerebral ganglion of Lumbricus terrestris were classified ultrastructurally. The Nsy cells within the subesophageal ganglion, nerve cord ganglion, and the peripheral nervous system were also examined. A comparative survey of Nsy cells of four other species of oligochaetes, Eisenia feotida, octolasion cyaneum, Dendrobeona subrubicunda, and Allolophora longa, was also carried out. Seven cell types (A1, A2, A3, A4, A5, C, and SEF), distinguished by special cytological and ultrastructural features, were found within the cerebral ganglion. Distribution of these cells inside and outside the cerebral ganglion was studied in detail by light and electron microscopy. The nerve terminals of each cell type were followed into the neuropile region. Exocytosis from cell bodies appears to be the main release mechanism for the Nsy granules, whereas small Nsy vesicles are released through synapses in the neuropile. Peripheral fibers of some cell types (A1, A2, and A3) extend through the capsule to the pericapsular epithelium. It is possible that Nsy cells secrete hormones from their cell bodies and peripheral processes and that their centrally directed axons release modulators/transmitters within the neuropile.     

Certain Histological and Anatomical Features of the Central Nervous System of a Large Indian Spider, Poecilotheria

SYNOPSIS. Some of the finer details of the anatomical organizationof the subesophageal ganglion of the spider, Poecilotheria sp.were studied in Palmgren silver-stained sections at the lightmicroscopic level. The ganglionic mass is differentiated intoa central fibrous core and a peripheral layered mass of cellularcortex. The neuropile is heterogeneous, consisting of both diffuseand glomerular types, and is considered the primary place forintegration. The dorsal region is motor, and the ventral issensory. The processes of motor cells and endings of sensoryneurons are restricted mostly to a single ganglion. Each largemotor neuron possesses a long stem-process, short and highlybranched dendritic ramifications, and a smooth, unbranched axon.Larger interneurons are more diversified, and extend from oneto several ganglia. These are of ascending or descending oreven decussating types. Smaller interneurons are mostly restrictedto one or a few ganglia. On the basis of this organization theprobable synaptic junctions between neurons are discussed.     

Ultrastructure of the frontal ganglion of Chaoborus and observations on neurosecretory cells during the annual cycle

The frontal ganglion contains approximately 20 cells and rests on the two posterior elevator muscles of the roof of the pharynx, thus locating the ganglion ventral and anterior to the brain. Two frontal nerves, a pair of lateral connectives, and the single recurrent nerve connect with the ganglion. There is a centrally located neuropile which is surrounded by the perineurium which in turn is covered by the neural lamella. The perineruium contains numerous glial cells and neurons with two large neurosecretory cells located in a dorsal lateral position of the ganglion.The neurosecretory cells were examined on five occasions during the year, and no significant changes occurred in the fine structure of the organelles or cellular products. The cells appear to be engaged in the synthesis of elementary neurosecretory granules throughout the year. This observation differs from previous studies on diapausing lepidopterous larvae and pupae. Axons from these two cells enter the lateral connectives and extend toward the protocerebrum.     

Localization of a SALMFamide Neuropeptide in the Larval Nervous System of the Sand Dollar Dendraster excentricus

Using immunocytochemical methods we describe the localization of serotonin and the SALMFamide peptide, S1 (GFNSALMFamide), during embryonic and larval development of the echinoid Dendraster excentricus. Anti-SI immunoreactivity first appears in the apical ganglion in late gastrulae at the same time as anti-serotonin immunoreactivity. Initially, anti-S1 immunoreactivity is restricted to fibres of the neuropile, but in later feeding stages, cell bodies are also immunoreactive. Anti-S1 immunoreactivity appears as 2–4 cells in the oral ganglion of early prism stage larvae, whereas anti-serotonin immunoreactivity does not occur in the oral ganglion until the 8-arm stage. Anti-S1 immunoreactivity also occurs in diffuse fibres in the oesophagus and in a single fibre encircling the pyloric sphincter of the gut. A reticular network associated with the apical surface of the epithelial cells of the vestibule of the adult rudiment was anti-S1 immunoreactive. In double-labelling experiments, anti-serotonin and anti-S1 immunoreactivity co-localize in the neuropile of the apical ganglion. The distribution of S1, in association with putative sensory cells in the apical and oral ganglia and with muscles of the oesophagus and gut, suggests S1 may have diverse functions in the larval nervous system. The distribution of anti-S1 immunoreactivity in echinoid embryos and larvae supports the proposal that SALMFamide-like peptides are widely shared in echinoderms and potentially have a fundamental role in neural function.     

Social influences on nymphal development in the cockroach, Diploptera punctata

Solitary male nymphs of the cockroach Diploptera punctata (Eschscholtz) (Blattaria: Blaberidae) took significantly longer to reach adulthood than males paired with either a male or female nymph or grouped with four other male nymphs since birth. When isolated throughout nymphal development, 15.8% of males passed through 3 stadia before adult eclosion, and the remainder went through 4 stadia. In contrast, 61.3% of paired males became adults in 3 stadia. Males need not, however, be isolated or paired for the entire nymphal period to express isolated or paired patterns of development. About 60% of males paired in just the first stadium or its initial 9 days became adults in 3 stadia, and only 20.4% of males isolated in the first stadium and the first 3 days of the second reached adulthood within 3 stadia. Although the first stadium was a critical period in which social condition determined the course of future development, analyses of covariance showed that isolated males gained less weight than paired ones, not only in the first stadium, but in the second as well. Moreover, the degree of growth of a male in the second stadium, measured as either weight gain or relative growth rate, did not depend on the male's social condition in the first stadium, because isolated second-instar males grew less than paired ones, even when both sets of insects had been paired in the first stadium. Female nymphal development, unlike that of males, was not greatly affected by social factors.     

Role of the perineurium and glial lacunar system in nutrition and storage of nutrients in the central nervous system of Spodoptera litura Fabr. (Lepidoptera: Noctulidae) at the time of reorganisation of the neural lamella during metamorphosis

Brains and nerve cords of Spodoptera litura (Fabr.) of various stages during metamorphosis were tested for acid mycopolisaccharides (AMPS), PAS-positive substances, glycogen, proteins and lipids. During reorganisation of the neural lamella in pupal period glycogen and PAS-positive substances are stored in perineurium and AMPS in the glial lacunar system (GIS) and below the perineurium as a thin layer. Lipids and AMPS diffuse in the GIS. The perineurium and GIS serve for the passage as well as storage of nutrients. In neuropile, only proteins are present. Significances of these findings is discussed.     

Intralamellar neurohemal complexes in the cerebral commissure of the leech Macrobdella decora (Say, 1824): An electron microscope study

Electron microscopy of the cerebral ganglionic commissure of the leech Macrobdella decora (Say, 1824) revealed numerous neurosecretory axons terminating in the neural lamella of both the inner and outer capsules, and in the neural lamella deep within the neuropile. The proximal protions of the terminals, with an investment of glial tissue, contain either numerous large homogeneously electron dense granules, or numerous large granules of varying electron density. The distal portions, often devoid of glia, display numerous infoldings, omega profiles, and electron dense focal sites, and contain numerous neurosecretory granules, small lucent vesicles, and, occasionally, acanthosomes. Statistical analysis of the size distribution and morphology of the neurosecretory granules showed that in many individual terminals the granules are not significantly different from those seen within four groups of neurosecretory cells found in the cerebral ganglion. These terminals, because of their diffuse nature, probably represent a neurohemal complex of a primitive nature. The term “intralamellar complexes” is proposed to describe the form and location of these neurosecretory terminals.     

Structural organization of the brain and subesophageal ganglion of male Aedes aegypti (L.) (Diptera : Culicidae)

The brain and subesophageal ganglion of male Aedes aegypti (L.) (Diptera : Culicidae) are described from cryofractures and silver-stained, semithin (0.5 μm) serial sections of whole heads observed in the scanning and light microscopes. The brain and subesophageal ganglion of male A. aegypti are fused. The major structures of the brain include the protocerebral lobes and bridge, the mushroom bodies, central complex of the protocerebrum, the mechanosensory regions and olfactory loves of the deutocerebrum, and the tritocerebrum. Major commissures of the brain are the anterior optic tract, central commissure, posterior dorsal commissure, and subesophageal commissure. The structural associations of brain components with each other and the subesophageal ganglion, as well as the paths of the major nerve tracts in male A. aegypti are described and compared with those in other Diptera.     

Immunocytochemical localization of prolactin-like antigenic determinants in the neuroendocrine system of the honeybee (Apis mellifica)

In the brain of the adult worker bee (Apis mellifica) prolactin-like (PRL) immunoreactive cells were localized in the lateral neurosecretory cell region and the subesophageal ganglion by means of the PAP procedure. These cells emit nerve fibers which pass through the neuropile of the brain to the corpora cardiaca where a great number of immunoreactive axon terminals is present. Test with antisera against rat pituitary prolactin and human luteinizing hormone were negative. These results indicate that hPRL material is produced in neurosecretory cells of the bee brain and transferred via axons to the corpora cardiaca for storage and subsequent release into haemolymph.     

The projections of neurosecretory cells in the brain of the North-American medicinal leech,Macrobdella decora,using intracellular injection of horseradish peroxidase

The projections of four anatomically distinct groups of putative neurosecretory cells found within the supra-oesophageal ganglion of the leech Macrobdella decora were studied by intracellular injection of horseradish peroxidase. All four groups have their own characteristic branching pattern while sharing the common feature of possessing primary branches that project into the dorsal commissure. Numerous secondary processes extend from these primary branches to terminate within the neural lamella, as well as within the neuropile. Electron microscopy of the regions into which these secondary processes project reveals numerous neurosecretory terminals. The data suggests that the midregion of the dorsal commissure constitues a neurohemal complex. These observations strengthen the argument that the four groups of identified cells are indeed neurosecretory.     

Fine structure of the CNS ganglia in the geometric spider Nephila clavata (Araneae: Nephilidae)

As web spiders usually hang with their head downward, geometrical differences in body position could affect the organization of their central nervous system (CNS). Nevertheless, most of our knowledge of spider's CNS is dependent on what has been revealed from wandering spiders. To fill the gap, we describe here the fine structural organization of the ganglionic neurons and nerves in the geometric orb web spider Nephila clavata. Nerve cells in the supraesophageal ganglion in N. clavata are packed in the frontal, dorsal and lateral regions, but the nerve cells of the subesophageal mass are only restricted to the ventral and ventrolateral regions. High resolution transmission electron microscopy (TEM) reveals the fine structural details of the neuroglial cells and the neuronal cells which have a conspicuous Golgi apparatus, rough ER, free ribosomes and well‐developed mitochondria. Comparing fine structural characteristics of the CNS ganglia with those of wandering spiders in most respects, it has been revealed that the geometrical difference may affects to the arrangement of receptors in the central body known as an important association center for web building behavior. In particular, remarkable differences can be detected in the protocerebral area by the extraordinary development of the central body including absence of the globuli and associated mushroom bodies.     

Fine Structural Analysis of the Central Nervous System in the Spider, Achaearanea tepidariorum (Theridiidae: Araneae)

ABSTRACT Central nervous system (CNS) of arachnids is still mysterious and has a rich unexplored field compare to what is known in insects or crustaceans. The CNS of the spider, Achaearanea tepidariorum, consists of a dorsal brain or supraesophageal ganglion and circumesophageal connectives joining it to the subesophageal mass. As the segmentation of the arachnid brain is still under discussion, we classify the brain as a protocerebral and tritocerebral ganglion depending on the evidences which generally accepted. The subesophageal nerve mass underneath the brain is the foremost part of the ventral nerve cord. All of this nerve mass is totally fused together, and forming subesophageal ganglia in this spider. In the brain, the nerve cells are packed in the frontal, dorsal and lateral areas, but are not absent from the posterior and ventral regions. In addition, the nerve cells of the subesophageal and abdominal ganglia are only restricted to the ventral and ventolateral regions. The CNS of the spider, Achaearanea tepidariorum is similar in feature to the Family Araneidae.