<Emphasis Type="Italic">Engrailed</Emphasis> is expressed in larval development and in the radial nervous system of <Emphasis Type="Italic">Patiriella</Emphasis> sea stars

We documented expression of the pan-metazoan neurogenic gene engrailed in larval and juvenile Patiriella sea stars to determine if this gene patterns bilateral and radial echinoderm nervous systems. Engrailed homologues, containing conserved En protein domains, were cloned from the radial nerve cord. During development, engrailed was expressed in ectodermal (nervous system) and mesodermal (coeloms) derivatives. In larvae, engrailed was expressed in cells lining the larval and future adult coeloms. Engrailed was not expressed in the larval nervous system. As adult-specific developmental programs were switched on during metamorphosis, engrailed was expressed in the central nervous system and peripheral nervous system (PNS), paralleling the pattern of neuropeptide immunolocalisation. Engrailed was first seen in the developing nerve ring and appeared to be up-regulated as the nervous system developed. Expression of engrailed in the nerve plexus of the tube feet, the lobes of the hydrocoel along the adult arm axis, is similar to the reiterated pattern of expression seen in other animals. Engrailed expression in developing nervous tissue reflects its conserved role in neurogenesis, but its broad expression in the adult nervous system of Patiriella differs from the localised expression seen in other bilaterians. The role of engrailed in patterning repeated PNS structures indicates that it may be important in patterning the fivefold organisation of the ambulacrae, a defining feature of the Echinodermata.     

Distribution of SchistoFLRFamide-like immunoreactivity in the adult ventral nervous system of the locust,Schistocerca gregaria

SchistoFLRFamide (PDVDHVFLRF-NH₂) is one of the major endogenous neuropeptides of the FMRF-amide family found in the nervous system of the locust,Schistocerca gregaria. To gain insights into the potential physiological roles of this neuropeptide we have examined the distribution of SchistoFLRFamide-like immunoreactivity in the ventral nervous system of adult locusts by use of a newly developed N-terminally specific antibody. SchistoFLRFamide-like immunoreactivity in the ventral nerve cord is found in a subgroup of the neurones that are immunoreactive to an antiserum raised against bovine pancreatic polypeptide (BPP). In the suboesophageal ganglion three groups of cells stain, including one pair of large posterior ventral cells. These cells are the same size, in the same location in the ganglion and have the same branching pattern as a pair of BPP immunoreactive cells known to innervate the heart and retrocerebral glandular complex of the locust. In the thoracic and abdominal ganglia two and three sets of cells, respectively, stain with both the SchistoFLRFamide and BPP antisera. In the abdominal ganglia the immunoreactive cells project via the median nerves to the intensely immunoreactive neurohaemal organs.     

The distribution of pheromone-biosynthesis-activating neuropeptide (PBAN) immunoreactivity in the central nervous system of the corn earworm moth,Helicoverpa zea

Summary Production of sex pheromone in several species of moths has been shown to be under the control of a neuropeptide termed pheromone-biosynthesis-activating neuropeptide (PBAN). We have produced an antiserum to PBAN from Helicoverpa zea (Lepidoptera: Noctuidae) and used it to investigate the distribution of immunoreactive peptide in the brain-suboesophageal ganglion complex and its associated neurohemal structures, and the segmental ganglia of the ventral nerve cord. Immunocytochemical methods reveal three clusters of cells along the ventral midline in the suboesophageal ganglion (SOG), one cluster each in the presumptive mandibular (4 cells), maxillary (12–14 cells), and labial neuromeres (4 cells). The proximal neurites of these cells are similar in their dorsal and lateral patterns of projection, indicating a serial homology among the three clusters. Members of the mandibular and maxillary clusters have axons projecting into the maxillary nerve, while two additional pairs of axons from the maxillary cluster project into the ventral nerve cord. Members of the labial cluster project to the retrocerebral complex (corpora cardiaca and cephalic aorta) via the nervus corpus cardiaci III (NCC III). The axons projecting into the ventral nerve cord appear to arborize principally in the dorsolateral region of each segmental ganglion; the terminal abdominal ganglion is distinct in containing an additional ventromedial arborization in the posterior third of the ganglion. Quantification of the extractable immunoreactive peptide in the retrocerebral complex by ELISA indicates that PBAN is gradually depleted during the scotophase, then restored to maximal levels in the photophase. Taken together, our findings provide anatomical evidence for both neurohormonal release of PBAN as well as axonal transport via the ventral nerve cord to release sites within the segmental ganglia.Abbreviations A aorta - Br-SOG brain-suboesophageal ganglion complex - CC corpus cardiacum - PBS phosphate-buffered saline - PLI PBAN-like immunoreactivity - TAG terminal abdominal ganglion - VNC ventral nerve cord     

Neurochemical characterization of nervous elements innervating the body wall of earthworms (Lumbricus, Eisenia): immunohistochemical and pharmacological studies

The distribution and chemical neuroanatomy of nervous elements and certain pharmacological–physiological characteristics of the innervation of the body wall in earthworms are described. Solitary sensory bipolar cells can be found among the epithelial cells. These bipolar cells contain serotonin, tyrosine hydroxylase, histamine, gamma-amino-butyric acid (GABA), Eisenia tetradecapeptide, proctolin or rhodopsin in various combinations. In the body wall, the plexus submuscularis is composed of nerve fibres only, whereas the plexus subepithelialis and muscularis also contain solitary nerve cells. These cells display histamine, GABA or neuropeptide Y immunoreactivity. The fibres of the three plexuses are reactive to serotonin, histamine, Eisenia tetradecapeptide, proctolin, GABA and neuropeptide Y antibodies. FMRFamide-immunoreactive fibres of the plexus muscularis originate from the central nervous system, whereas axons containing the other studied molecules are derived from both peripheral and central structures. High pressure liquid chromatography assays have revealed serotonin, dopamine and histamine in the body wall. Contractions of the body wall musculature can be elicited with serotonin and FMRFamide. Serotonin-evoked contractions are suppressed by the application of GABA. Serotonin acts both directly on the muscle cell receptors and indirectly through initiating transmitter release from the nervous elements, whereas the FMRFamide-induced contractions seem to be mediated through the muscle cell receptors only. The pharmacological profiles of the serotonin and GABA receptors resemble those of the vertebrate 5-HT₃ and GABA_B receptor types. Our findings indicate that both the sensory and efferent system of the annelid body wall operate by means of a variety of neuroactive compounds, suggesting a complex role of signalling systems in the regulation of this organ.This work was supported by the Hungarian Scientific Research Fund (OTKA; grant nos. T 34106 and T 34160). Márta Wilhelm is in receipt of a János Bolyai Scholarship.     

The distribution of pancreatic polypeptide in the nervous system and gut of the blowfly,Calliphora vomitoria (Diptera)

Summary The distribution of a neuropeptide, previously shown to have the same or a very similar amino acid composition as vertebrate pancreatic polypeptide (PP), has been studied in the nervous system and gut of the blowfly, Calliphora vomitoria. Neurones immunoreactive to a bovine PP antiserum occur in the thoracic and abdominal ganglionic components of the central nervous system, in addition to the brain and suboesophageal ganglion. Pancreatic polypeptide appears to be relayed from its cells of origin to a neurohaemal organ in the dorsal sheath of the thoracic ganglion. PP immunoreactivity is also found in cells of the hypocerebral ganglion of the stomatogastric nervous system and in associated nerve fibres. The mid-gut contains PP-positive material in flask-shaped cells of its epithelial lining.     

Localisation of GYIRFamide immunoreactivity inMacrostomum hystricinum marinum (Plathelminthes,Macrostomida)

The distribution of GYIRFamide immunoreactivity in the nervous system ofMacrostomum hystricinum marinum has been demonstrated by an indirect fluorescence technique in conjunction with confocal scanning laser microscopy (CSLM). Immunostaining was extensive in both the central (CNS) and peripheral (PNS) nervous systems, revealing detailed information on the microanatomy of the peptidergic nervous system of this free-living plathelminth. In the CNS, immunoreactive nerve cell bodies and nerve fibres occurred in the brain and along two pairs of longitudinal nerve cords: the main nerve cords and the ventral nerve cords. In the PNS, immunostaining was prevalent in nerve cells and fibres innervating the pharynx and the gut. The employed antibody is directed against a recently characterised FMRF-amide-related peptide (FaRP), GYIRFamide, isolated from two species of the Tricladida,Dugesia tigrina andBdelloura candida. Phylogenetically, GYIRFamide represents the most ancient neuropeptide thus far identified within the Bilateria     

Immunoreactivity to a specific echinoderm neuropeptide in the nervous system of the flatworm Macrostomum hystricinum marinum (Turbellaria,Macrostomida)

Immunocytochemical characterization of the neuropeptides FMRF-amide and serotonin (5-HT) is a well-known method successfully applied to demonstrate nervous-system morphology in several platyhelminths (see Wikgren & Reuter, 1985, and Reuter, 1988, for review). We have immunolabeled whole-mount preparations of Macrostomum hystricinum marinum Rieger from cultures (see Rieger et al., 1988) with anti-SALMF-amide, an antibody specific for the C-terminal pentapeptide sequence of the neuropeptide GNFSALMF-amide recently isolated from echinoderms (source M. Thorndyke, England). Immunoreactivity to SALMF-amide gave a more detailed picture of the nervous system of M. hystricinum than FMRF-amide. Conventional light microscopy (Luther, 1905) shows this nervous system to consist of a bilobed brain, a pharyngeal nerve-ring system, a posterior commissure, and two main ventrolateral nerve cords. Immunostaining reveals, in addition, two thin paired longitudinal nerve strands and fine subepithelial and submuscular nerve nets. Anti-SALMF-amide labels a distinct class of neurons, causing the main lateral longitudinal cords and pharyngeal nerve-ring system to appear more filamentous than with other techniques. Recent fine-structural investigations on the nervous system of Macrostomum hystricinum marinum revealed several axon types with characteristic vesicles and neurotubules (D. R. pers. obs.). Partly supported by FWF grant P7816.     

Evidence for a FMRFamide-like peptide in the heteronemertine Cerebratulus lacteus Leidy

Circular body wall muscles of Cerebratulus lacteus respond to micromolar concentrations of the neuropeptide Phe-Met-Arg-Pheamide (FMRFa), first isolated from molluscan nervous tissue. Comparison of the relative body wall contractural potencies of various FMRFa analogs indicates that the Arg-Pheamide group is necessary for this activity, but the remaining N-terminal region can be altered considerably without loss of activity. The circular muscle failed to respond to met-enkephalin and many other vertebrate neuropeptides. Acetone-soluble extracts of Cerebratulus contained two FMRFa antibody immunoreactive components separable by reversed phase liquid chromatography. Neither component had the same retention time as FMRFa. Bouin's fixed and paraffin embedded Cerebratulus nervous tissues displayed specific immunofluorescence when incubated with FMRFa polyclonal antibody but not monoclonal antibody specific for the molluscan neuropeptide SCP-B. Some giant neuron somas in the lateral nerve cords and in the ventral cerebral ganglia were immunochemically reactive as were axons in the lateral nerve cord and in the circular and transverse body wall muscles. Pre-exposure of the antibody with FMRFa prevented the reaction. Thus several types of evidence suggest the presence of FMRFa-like neuropeptides in Cerebratulus lacteus.     

Sensitive enzyme immunoassay for Manduca allatotropin and the existence of an allatotropin-immunoreactive peptide in Periplaneta americana

Antisera to Manduca sexta allatoropin were raised in rabbits and were used to develop a competitive enzyme immunoassay for this neuropeptide. The detection limit of the assay is less than 2 fmol/well. A useful quantification can be obtained from 2 to 30 fmol/well. No cross-reactivity was observed with several insect peptides, but the enzyme-linked immunosorbent assay does recognize [Ala⁶, Leu⁷, Ser⁸]-allatotropin, a myotropin recently isolated from Locusta migratoria. The assay was used to study the distribution of allatotropin within the nervous system of Manduca sexta. The peptide is present in the retrocerebral complex, the brain, and the ventral nerve cord of this species, in quantities of respectively 0.01, 1.2, and 1.7 pmol per insect. An allatotropin-immunoreactive peptide was found in the nervous system of Periplaneta americana. It is present in the ventral nerve cord (3.3 pmol/insect), brain (1.9 pmol/insect), and retrocerebral complex (0.09 pmol/insect). These data suggest that peptides of this family are generally present in insects. © 1993 Wiley-Liss, Inc.     

The Larval Nervous System of Polygordius lacteus Scheinder, 1868 (Polygordiidae,Polychaeta): Immunocytochemical Data

The nervous system of the planktotrophic trochophore larva of Polygordius lacteus has been investigated using antibodies to serotonin (5-HT) and the neuropeptide FMRFamide. The apical ganglion contains three 5-HT-ir neurons, many FMRFamide-ir neurons and a tripartate 5-HT-ir and FMRFamide-ir neuropil. A lateral nerve extends from each side of the apical ganglion across the episphere and the ventral hyposphere, where the two nerves combine to form the paired ventral nerve cord. These nerves have both 5-HT-ir and FMRFamide-ir processes. Three circumferential nerves are associated with the ciliary bands: two prototroch and one metatroch nerve. All contain 5-HT-ir and FMRFamide-ir processes. An oral nerve plexus also contain both 5-HT-ir and FMRFamide-ir processes develops from the metatroch nerve, and an esophageal ring of FMRFamide-ir processes develops in later larval stages. In young stages the ventral ganglion contains two 5-HT-ir and two FMRFamide-ir perikarya; during development the ventral ganglion grows caudally and adds additional 5-HR-ir and FMRFamide-ir perikarya. These are the only perikarya that could be found along the lateral nerve and ventral nerve cord. The telotroch nerve develops from the ventral nerve cord. The 5-HT-ir and FMRFamide-ir part of the nervous system is strictly bilateral symmetric. and much of the system (i.e. apical ganglion, lateral nerves ventral nerve cord, dorsal nerve and oral plexus) is retained in the adult.     

The organization of the nervous system in Plathelminthes. The neuropeptide F-immunoreactive pattern in Catenulida,Macrostomida, Proseriata

The organization of the nervous system of Archilopsis unipunctata Promonotus schultzei and Paramonotus hamatus (Monocelididae, Proseriata) and Stenostomum leucops (Catenulida) and Microstomum lineare (Macrostomida) was studied by immunocytochemistry, using antibodies to the authentic flatworm neuropeptide F (NPF) (Moniezia expansa). The organization of the nervous system of the Monocelididae was compared to that of the nervous system of Bothriomolus balticus (Otoplanidae), a previously studied species of another family of the Proseriata. The results show that the main nerve cords (MCs), independent of lateral or ventral position in the Monocelididae and the Otoplanidae, correspond to each other. The study also confirms the status of the lateral cords as main cords (MCs) in S. leucops and M. lineare. Common for MCs in the members of the investigated taxa are the following features: MCs consist of many fibres, originate from the brain and are adjoined to 5-HT-positive neurons. In Monocelididae and Otoplanidae, the MCs additionally have the same type of contact to the pharyngeal nervous system. Also common for both proseriate families is the organization of the two lateral nerve cords, with weaker connections to the brain, and the pair of dorsal cords running above the brain. The organization of the minor cords differs. The Monocelididae have a pair of thin ventral cords forming a mirror image of the dorsal pair. Furthermore, an unpaired ventral medial cord connecting medial commissural cells was observed in P. schultzei. Marginal nerve cords, observed in Otoplanidae, are absent in Monocelididae. All minor nerve cords are closely connected to the peripheral nerve plexus. The postulated trends of condensation of plexal fibres to cords and/or the flexibility of the peripheral nerve plexus are discussed. In addition, the immunoreactivity (IR) pattern of NPF was compared to the IR patterns of the neuropeptide RFamide and the indoleamine, 5-HT (serotonin). Significant differences between the distribution of IR to NPF and to 5-HT occur. 5-HT-IR dominates in the submuscular and subepidermal plexuses. In the stomatogastric plexus of M. lineare, only peptidergic IR is observed in the intestinal nerve net. The distribution of NPF-IR in fibres and cells of the intestinal wall in M. lineare indicates a regulatory function for this peptide in the gut, while a relationship with ciliary and muscular locomotion is suggested for the 5-HT-IR occurring in the subepidermal and submuscular nerve, plexuses. In M. lineare, the study revealed an NPF- and RFamide-positive cell pair, marking the finished development of new zooids. This finding indicates that constancy of these cells is maintained in this asexually reproducing and regenerating species.     

The nervous system ofNectonema munidae andGordius aquaticus,with implications for the ground pattern of the Nematomorpha

 The nervous system of Nectonema munida is shown to be composed of a brain, a ventral nerve cord with an anterior and a posterior enlargement, a dorsal nerve cord and a plexus-like basiepidermal nervous system. The ultrastructure of these parts is given. Additionally, the ventral nerve cord of Gordius aquaticus is ultrastructurally described. The results are compared with the literature to work out the ground pattern of the Nematomorpha according to the nervous system. This contains a circumpharyngeal brain with a main subpharyngeal portion and a weak suprapharyngeal portion, a ventral and dorsal intraepidermal nerve cord and a peripheral nervous system. The ground pattern of the nervous system of Nematomorpha is then compared to that of other Nemathelminthes. The form of the brain and the distribution of perikarya are derived characters of the Nematomorpha. The existence of an unpaired ventral and an unpaired dorsal nerve cord and the position of these two cords in epidermal cords are synapomorphies of the Nematomorpha and the Nematoda. Accepted: 7 July 1996     

Immunoreactivity to the pancreatic polypeptide family in the nervous system of the adult human blood fluke,Schistosoma mansoni

Summary The presence and distribution of neuropeptides belonging to the pancreatic polypeptide family have been demonstrated by an indirect immunofluorescence technique in the nervous systems of adult male and female Schistosoma mansoni. Seven antisera of differing regional specificity to pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) were employed on both whole-mount and cryostat-sectioned material. Positive immunoreactivity (IR) was obtained with all antisera except an N-terminally-directed antiserum to NPY. In the CNS, immunoreactivity was restricted to cell bodies and nerve fibres in the anterior ganglia, central commissure and dorsal and ventral nerve cords of both sexes, whereas, in the PNS, positive-IR was present in the plexuses innervating the subtegumental musculature and the oral and ventral suckers. Intense immunoreactivity was observed in a plexus of nerve fibres and cell bodies in the lining of the gynaecophoric canal and in fine nerve fibres innervating the dorsal tubercles of the male. In contrast, in the female, strong immunoreactivity was evident in nerve plexuses innervating the lining of the ovovitelline duct and in the wall of the ootype, but most notably in a cluster of cells in the region of Mehlis' gland. Results suggest that molecules with C-terminal homology to the PP-family are present in S. mansoni. These peptides would appear to be important regulatory molecules in the parasite's nervous system and may play a role in the control of egg production.     

Immunoreactivity to molluskan neuropeptides in the central and stomatogastric nervous systems of the earthworm, Lumbricus terrestris L.

Polyclonal antisera against two related command neuropeptides (CNP2 and CNP4) described in neurons of the terrestrial snail Helix were used in a study of the nervous system of the earthworm Lumbricus. The CNP-like peptides belong to the same neuropeptide subfamily and bear a C-terminal signature sequence Tyr-Pro-Arg-X. The distribution patterns of immunoreactive (IR) neurons were studied in the central nervous system (CNS), skin, and stomatogastric nervous system of the earthworm. IR neurons were found in all CNS ganglia, the patterns being similar for both antibodies used. Several clusters of IR cells were observed in the cerebral and subesophageal ganglia. In the ventral cord ganglia, the number of IR cells decreased in the rostro-caudal direction, and the IR cells sent their fibers mostly into the median fiber bundle. Segmental nerves contained no IR fibers. After injury of the worm body, the number of IR neurons in the CNS significantly increased. In the skin, IR sensory neurons were present in sensory buds. The stomatogastric ganglia only contained IR fibers. Numerous scattered IR neurons were found in the inner subepithelial layer of the esophagus and formed the enteric plexus in which the cell bodies displayed a segmentally repeated pattern. Possible involvement of CNP-like-IR neurons in central integratory processes, sensory processes, and the regulation of feeding is discussed.This work was supported by INTAS (grant 01-2117), CRDF (grant RB1-2321-MO-02), and the Russian Foundation for Basic Research (grants 05-04-48724 and 03-04-48179).     

The catecholaminergic system of an annelid (Ophryotrocha puerilis,Polychaeta)

Summary The complex catecholaminergic (CA) nervous system of the polychaete Ophryotrocha puerilis is documented using glyoxylic acid induced fluorescence (GIF) and immunohistochemistry. CA-neurons are found both in the central and peripheral nervous system. In the brain, about 50 CA-neurons are present in the perikaryal layer together with numerous CA fibres. Two pairs of CA perikarya are characteristic for each ganglion of the ventral nerve cord. CA-neurites in the ventral nerve cord are mainly arranged in 4 strands paralleling the longitudinal axis of the worm. Fluorescent neurons with receptive ciliary structures are present in body appendages (antennae, palps, urites, parapodial cirri), in the body-wall, and within the oesophageal wall. Furthermore, a subepidermal nerve net of free CA nerve endings has been found. After incubation of specimens with dopamine prior to the development of GIF more fluorescent perikarya could be observed; the fluorescence was also intensified. Pre-incubation with reserpine reduced the intensity of GIF. Results of high pressure liquid chromatography and immunostaining with a polyclonal antibody against a dopamine-glutaraldehyde-complex suggest that dopamine is the major CA transmitter. It is thought that dopaminergic neurons together with ciliary receptive structures act as mechano- and/or chemoreceptors.     

Cellular expression patterns of acetylcholinesterase activity during grasshopper development

We examined the expression of acetylcholinesterase (AChE) in the nervous system and epidermal body structures during embryonic and larval development of two grasshopper species: Locusta migratoria and Schistocerca americana. Histochemical labelling was blocked by the enzyme inhibitors eserine and BW284c51, but not by iso-OMPA, showing that the staining reflected true AChE activity. The majority of staining was localized on the cell surface but granular intracellular staining was also visible in many cell bodies. In both species, the cellular expression of AChE followed a similar but complex spatiotemporal staining pattern. Initially, mainly epidermal tissue structures were stained in the various body appendages (stages 25%–30%). Labelling subsequently appeared in outgrowing neurons of the central nervous system (CNS) and in the nerves innervating the limbs and dorsal body wall (stages 30%–40%). The latter staining originated in motoneurons of the ventral nerve cord. In a third phase (after 45%), the somata of certain identified mechanosensory neurons started to express AChE activity, presumably reflecting cholinergic differentiation. Staining was also found in repo-positive glial cells of the CNS, longitudinal glia of connectives, glia of the stomatogastric nervous system and glial cells ensheathing peripheral nerves. Glial cells remained AChE-positive during larval to adult development, whereas motoneurons lost their AChE expression. The expression pattern in non-neuronal cells and glutamatergic motoneurons and the developmental appearance of AChE prior to synaptogenesis in the CNS suggest non-cholinergic functions of AChE during grasshopper embryogenesis. Financial support was provided by the Deutsche Forschungsgemeinschaft (Bi 262/7-1 and 262/11-1)     

PBAN/pyrokinin peptides in the central nervous system of the fire ant, <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

The pyrokinin/pheromone-biosynthesis-activating neuropeptide (PBAN) family of peptides found in insects is characterized by a 5-amino-acid C-terminal sequence, FXPRLamide. The pentapeptide is the active core required for diverse physiological functions, including the stimulation of pheromone biosynthesis in female moths, muscle contraction, induction of embryonic diapause, melanization, acceleration of puparium formation, and termination of pupal diapause. We have used immunocytochemical techniques to demonstrate the presence of pyrokinin/PBAN-like peptides in the central nervous system of the fire ant, Solenopsis invicta. Polyclonal antisera against the C-terminal end of PBAN have revealed the location of the peptide-producing cell bodies and axons in the central nervous system. Immunoreactive material is detectable in at least three groups of neurons in the subesophageal ganglion and corpora cardiaca of all adult sexual forms. The ventral nerve cord of adults consists of two segmented thoracic ganglia and four segmented abdominal ganglia. Two immunoreactive pairs of neurons are present in the thoracic ganglia, and three neuron pairs in each of the first three abdominal ganglia. The terminal abdominal ganglion has no immunoreactive neurons. PBAN immunoreactive material found in abdominal neurons appears to be projected to perisympathetic organs connected to the abdominal ganglia. These results indicate that the fire ant nervous system contains pyrokinin/PBAN-like peptides, and that these peptides are released into the hemolymph. In support of our immunocytochemical results, significant pheromonotropic activity is found in fire ant brain-subesophageal ganglion extracts from all adult fire ant forms (queens, female and male alates, and workers) when extracts are injected into decapitated females of Helicoverpa zea. This is the first demonstration of the presence of pyrokinin/PBAN-like peptides and pheromonotropic activity in an ant species. This research was supported in part by a US-Israel Binational Science Foundation Grant (no. 2003367).     

Ultrastructure and organization of the epineural canal and the nerve cord in sea urchins (Echinodermata,Echinoida)

Summary The radial nerve cord ofMespilia globulus has been examined as an example of echinoid nerve cords. In the radius of echinoids only the ectoneural component of the nerve cord is present which is a derivative of the ectoderm. The nerve cord runs in the interior of the body and is accompanied by the epineural canal. In echinoids, the neuroepithelium makes up the upper and side walls of the epineural canal. Each lateral branch of the nerve cord forms a sort of neural tube. It encloses a branch of the epineural canal which represents an open connection with the sea water. Thus, the epineural canal exhibits numerous openings which probably allow sea water to flow back and forth. This organization is unique in echinoderms. — The neuroepithelium exhibits the organization of an epidermis with well-developed nervous elements. Glial cells are not present. The support cells are the true epithelial cells. Their monociliated cell bodies border the lumen and, by means of cytoplasmic stems that contain a bundle of filaments, they reach up to the basal lamina. The nerve cells and their trunk of nerve fibres fill the spaces between the support cells. — Three types of nerve cells can be distinguished according to their polarity: (1) Primary sensory cells that project a cilium into the epineural canal, the axon hillock region is at the opposite pole. (2) Subluminal cells whose cilium originates in the axon hillock region. (3) Neurones that lie within the trunk of nerve fibres. They are highly stretched in the direction of the nerve cord and are also provided with a cilium. Types 2 and 3 may be homologized with the basal nerve cells of the epidermis. They are possibly multipolar. — The lateral nerve cords make contact with the ampulla and pass the ambulacral plate parallel to the channel that connects the ampulla and the tube foot. The activity of the tube foot-ampulla system is possibly controlled by means of transmitter substances that diffuse through the connective tissue layer between the nerve cord and the myoepithelia of the ampulla and the tube foot respectively.     

Novel aspects of the nervous system of Bonellia viridis (Echiura) revealed by the combination of immunohistochemistry, confocal laser-scanning microscopy and three-dimensional reconstruction

The Echiura have been placed in close phylogenetic affinity to the Annelida on the basis of numerous homologous characters including the mode of development, the nearly identical formation of a trochophore larva, as well as the development and ultrastructure of chaetae and spermatozoa. Furthermore, phylogenetic analysis of elongation factor-1 gene sequences supports placement of the Echiura within the Annelida. Nevertheless, the Echiura are generally excluded from the Annelida due to their lack of segmentation. However, it must be considered that this lack could represent a secondary condition and that Echiura are derived from formerly segmented ancestors. In the present study, the combination of methods applied reveals several novel aspects of the central nervous system in developmental stages of Bonellia viridis. The most important of these is the metameric organization of the ventral nerve cord. Antibodies against different neurotransmitters label discrete repetitive units of perikarya in the ventral nerve cord. This organisation is additionally supported by the distribution of peripheral nerves as shown by labelling of neurotubules. These nerves are clearly paired and are evenly distributed, corresponding to the serial units of serotoninergic neurons. Different methods of computer-aided three-dimensional reconstruction display the precise spatial distribution of perikarya and peripheral nerves allowing the repetitive units to be discerned on the basis of relative size, position and number of labelled cells. The repetitive units in the nervous system of B. viridis correspond to segmental ganglia of various Annelida and are interpreted as an indication that Echiura are derived from formerly segmented ancestors, thus supporting the systematic inclusion of the Echiura within the Annelida.