Anatomical and physiological observations on the organization of mechanoreceptors and local interneurons in the central nervous system of the wandering spider Cupiennius salei

Summary In the wandering spider Cupiennius salei, the functional neuroanatomy of leg mechanosensory receptor neurons and interneurons associated with a single leg neumere was investigated by combined intracellular recording and Lucifer yellow ionophoresis. Trichobothria axons that selectively respond to air currents and to low-frequency airborne vibrations have arborizations restricted to ventral regions of the appropriate leg neuromere. Receptor afferents that respond selectively to substrateborne vibrations are distributed ventrally in the corresponding leg neuromere and extend into certain interganglionic tract neuropiles. Golgi impregnation and intracellular dye filling show that local interneurons originate in ventral sensory neuropiles of leg neuromeres and ascend dorsally to terminate amongst dendrites of motor neurons. Local interneurons generally show higher thresholds for vibration stimuli than do receptors. Local interneurons typically receive inputs from one or several types of receptors. Some respond to stimulation of a single leg, others respond to stimulation of several legs on the same side of the body. The functional morphology of the receptor afferents is correlated with known physiological characteristics of slit sensilla and trichobothria. Structure and activity of the local interneurons are compared with analogous interneurons in other arthropods.     

Central nervous projections of mechanoreceptors in the spider Cupiennius salei Keys.

Summary The basic organization of sensory projections in the suboesophageal central nervous system of a spider (Cupiennius salei Keys.) was analyzed with anterograde cobalt fills and a modified Golgi rapid method. The projections of three lyriform slit sense organs and of tactile hairs located proximally on the legs are described and related to central nerve tracts. There are five main longitudinal sensory tracts in the central region of the suboesophageal nervous mass arranged one above the other. Whereas the three dorsal ones contain fibers from the lyriform organs, the two ventral ones contain axons from the hair receptors. Axons from all three lyriform organs have typical shapes and widely arborizing ipsilateral intersegmental branches and a few contralateral ones. The terminal branches of the afferent projections from identical lyriform organs on each leg form characteristic longitudinal pathways, typical of each organ: U-shaped, O-shaped, or two parallel bundles. The terminations of the hair sensilla are ipsilateral and intersegmental. Two large bilaterally arranged longitudinal sensory association tracts receive inputs from all legs including the dense arborizations from tactile hairs, lyriform organs, and other sense organs. These tracts may serve as important integrating neuropils of the suboesophageal central nervous system.     

Histamine immunoreactivity in the central nervous system of the spider Cupiennius salei

In this study, immunohistochemistry on Vibracut sections is used to demonstrate anti-histamine immunoreactivity in the brain of the spider, Cupiennius salei (Keys.) (Ctenidae). We describe a system of histamine-immunoreactive neurons within the central nervous system that consists of six omnisegmental neurons. These histamine-immunoreactive neurons form two subgroups: a dorsal system with two cells per hemisphere and a ventral system with only one cell per hemisphere. The cells have extended arborizations in the motor and sensory areas of all neuromeres in the suboesophageal ganglionic mass. We have also found histamine immunoreactivity in the photoreceptors of C. salei and suggest that histamine is a neurotransmitter of photoreceptors in all arthropods, since it is also known to occur in the photoreceptors of the other main arthropod taxa (Merostomata, Crustacea, and Insecta).     

Hygro- and thermoreceptors in tip-pore sensilla of the tarsal organ of the spider Cupiennius salei: innervation and central projection

The hygro- and thermoreceptive tarsal organ in the wandering spider Cupiennius salei is located on the tarsus of each walking leg and pedipalp, and consists of a tiny air-filled capsule in the cuticle. This capsule communicates with the outside world through a small aperture and contains seven nipple-shaped sensilla, each with a pore at its tip. In both their external morphology and internal structure, the sensilla are indistinguishable, although one sensillum is innervated by only two sensory cells, whereas the other six sensilla contain three sensory cells. Their dendrites are unbranched and terminate at the tip-pore, where they are enveloped by amorphous material that appears to limit their exposure to the atmosphere. Cobalt fillings reveal that each tarsal organ projects to three different areas within the suboesophageal ganglionic mass: (1) the sensory longitudinal tract 3 and 4; (2) the corresponding pedipalpal or leg ganglion; (3) a structured neuropil (here termed the Blumenthal neuropil) beneath the oesophagus. The multiple representation of sensory afferents from each tarsal organ in different regions of the suboesophageal ganglionic mass suggests parallel processing of hygro-/thermoreceptive information.     

Intersegmental sensory tracts and contralateral motor neurons in the leg ganglia of the spider Cupiennius salei Keys

Summary Cobalt filling into spider legs reveals plurisegmental receptor endings and the plurisegmental origin of motor neurons. Motor neuron dendrites are organized into two domains, one interacting with plurisegmental receptors, the other arborizing within the lateral neuropil of the leg neuromere. The intersegmental organization of both motor and sensory elements supports behavioural studies demonstrating inhibitory connections between legs.     

Acetylcholine and histamine are transmitter candidates in identifiable mechanosensitive neurons of the spider Cupiennius salei: an immunocytochemical study

Histochemical and indirect immunocytochemical techniques were used to search for neuroactive substances and transmitter candidates in identified sensory neurons of two types of cuticular mechanoreceptors in the spider Cupiennius salei Keys.: (1) in lyriform slit-sense organ VS-3 (comprising 7-8 cuticular slits each innervated by 2 bipolar neurons), and (2) in tactile hairs (each supplied by 3 bipolar sensory cells). All neurons are mechanosensitive. A polyclonal antibody against choline acetyltransferase (ChAT) strongly labeled all cell bodies and afferent fibers of both mechanoreceptor types. Western blot analysis using the same antibody against samples of spider sensory hypodermis and against samples from the central nervous system demonstrated a clear band at 65 kDa, corresponding to the molecular mass of ChAT in insects. Moreover, staining for acetylcholine esterase (AChE) revealed AChE activity in one neuron of each mechanoreceptor type. Incubation with a polyclonal antibody against histamine clearly labeled one neuron in each set of sensilla, whereas activity in the remaining one or two cells was near background. All mechanoreceptor preparations treated with a polyclonal antiserum against serotonin tested negative, whereas sections through the central nervous system of the same spiders were clearly labeled for serotonin. The presence of ChAT-like immunoreactivity and AChE implicates acetylcholine as a transmitter candidate in the two mechanoreceptive organs. We assume that histamine serves as a mechanosensory co-transmitter in the central nervous system and may also act at peripheral synapses that exist in these sensilla. Received: 15 July 1996 / Accepted: 26 August 1996     

Embryonic expression patterns of Wnt genes in the RTA-clade spider Cupiennius salei

Spiders represent widely used model organisms for chelicerate and even arthropod development and evolution. Wnt genes are important and evolutionary conserved factors that control and regulate numerous developmental processes. Recent studies comprehensively investigated the complement and expression of spider Wnt genes revealing conserved as well as diverged aspects of their expression and thus (likely) function among different groups of spiders representing Mygalomorphae (tarantulas), and both main groups of Araneae (true spiders) (Haplogynae/Synspermiata and Entelegynae). The allegedly most modern/derived group of entelegyne spiders is represented by the RTA-clade of which no comprehensive data on Wnt expression were available prior to this study. Here, we investigated the embryonic expression of all Wnt genes of the RTA-clade spider Cupiennius salei. We found that most of the Wnt expression patterns are conserved between Cupiennius and other spiders, especially more basally branching species. Surprisingly, most differences in Wnt gene expression are seen in the common model spider Parasteatoda tepidariorum (a non-RTA clade entelegyne species). These results show that data and conclusions drawn from research on one member of a group of animals (or any other organism) cannot necessarily be extrapolated to the group as a whole, and instead highlight the need for comprehensive taxon sampling.     

Peripheral synapses at identifiable mechanosensory neurons in the spider Cupiennius salei : synapsin-like immunoreactivity

Indirect immunocytochemical tests were used at the light- and electron-microscopic levels to investigate peripheral chemical synapses in identified sensory neurons of two types of cuticular mechanosensors in the spider Cupiennius salei Keys.: (1) in the lyriform slit-sense organ VS-3 (comprising 7–8 cuticular slits, each innervated by 2 bipolar sensory neurons) and (2) in tactile hair sensilla (each supplied with 3 bipolar sensory cells). All these neurons are mechanosensitive. Application of a monoclonal antibody against Drosophila synapsin revealed clear punctate immunofluorescence in whole-mount preparations of both mechanoreceptor types. The size and overall distribution of immunoreactive puncta suggested that these were labeled presynaptic sites. Immunofluorescent puncta were 0.5–6.8 μm long and located 0.5–6.6 μm apart from each other. They were concentrated at the initial axon segments of the sensory neurons, while the somata and the dendritic regions showed fewer puncta. Western blot analysis with the same synapsin antibody against samples of spider sensory hypodermis and against samples from the central nervous system revealed a characteristic doublet band at 72 kDa and 75 kDa, corresponding to the apparent molecular mass of synapsin in Drosophila and in mammals. Conventional transmissionelectron-microscopic staining demonstrated that numerous chemical synapses (with at least 2 vesicle types) were present at these mechanosensory neurons and their surrounding glial sheath. The distribution of these synapses corresponded to our immunofluorescence results.Ultrastructural examination of anti-synapsin-stained neurons confirmed that reaction product was associated with synaptic vesicles. We assume that the peripheral synaptic contacts originate from efferents that could exert a complex modulatory influence on mechanosensory activity. Received: 20 April 1998 / Accepted: 18 August 1998     

Mechanism of signal production in the vibratory communication of the wandering spider Cupiennius getazi (Arachnida,Araneae)

The communication with substrate vibrations produced by vibrations of the body or its appendages is widespread among arthropods, especially among spiders. Its biomechanics, however, is poorly understood. Males of the wandering spider Cupiennius getazi produce such substrate vibrations during courtship by means of dorsoventral movements of their opisthosoma without hitting their dwelling plant.Simultaneous recordings of the plant vibrations (accelerometry), of the opisthosoma movements (laser Doppler vibrometry) and of the electromyograms of the opisthosomal depressor muscle, revealed that the main frequency of the vibratory signal of about 80 Hz originates from the activity of the opisthosomal depressor muscle. The transfer functions of the spider's body show resonances which could amplify the main frequency before it is transmitted into the plant.A low frequency component of the opisthosomal movement (duration c. 0.3 s, displacement c. 6 mm (peak-peak) 30° deflection angle, frequency 10–20 Hz) can be distinguished from a main frequency component (duration c. 0.1 s, displacement c. 0.5 mm 2.5° deflection angle, frequency c. 80 Hz). The main frequency component is superimposed on an upward movement of the low frequency component.     

Neuroanatomy of the central nervous system of the wandering spider,Cupiennius salei (Arachnida,Araneida)

Summary In Cupiennius salei (Ctenidae), as in other spiders, the central nervous system is divided into the supraoesophageal ganglion or brain and the suboesophageal ganglia (Fig. 1). The two masses are interconnected by oesophageal connectives. The brain gives off four pairs of optic and one pair of cheliceral nerves. From the suboesophageal ganglia arise a pair of pedipalpal, four pairs of leg, and several pairs of opisthosomal nerves (Fig. 2). 1. Cell types. In the brain a total of 50900 cells were counted, in the suboesophageal ganglia 49000. They are all monopolar cells, found in the ganglion periphery and may be classified into four types: (a) Small globuli cells (nuclear diameter 6–7 m) forming a pair of compact masses in the protocerebrum (Fig. 10b); (b) Small and numerous cells (cell diameter 12–20 m) with processes forming the bulk of the neuropil in the brain and suboesophageal ganglia; (c) Neurosecretory cells (cell diameter ca. 45 m) in the brain and suboesophageal ganglia; (d) Large motor and interneurons (cell daimeter 40–112 m), mostly in the suboesophageal ganglia (Figs. 10a and c). 2. Suboesophageal mass. The cell bodies form a sheet of one to several cell layers on the ventral side of each ganglion and are arranged in groups. Three such groups were identified as motor neurons, four as interneurons. At the dorsal, dorso-lateral, and mid-central parts of the ganglion there are no cell somata. The fibre bundles arising from them form identifiable transverse commissural pathways (Fig. 9b). They form the fibrous mass in the central part of the suboesophageal mass.Neuropil is well-formed in association with the sensory terminations of all major nerves (Fig. 9a). As these proceed centrally they break up into five major sensory tracts forming five layers one above the other. There are six pairs of additional major longitudinal tracts arranged at different levels dorsoventrally (Fig. 8). They ascend into the brain through the oesophageal connectives and terminate mostly in the mushroom bodies and partly in the central body. 3. Protocerebrum. Fine processes of the globuli cells form the most important neuropil mass in the fibrous core, called the mushroom bodies. These consist of well developed glomeruli, hafts, and bridge which are interconnected with the optic masses of the lateral eyes and most fibre tracts from the brain and suboesophageal mass (Fig. 7). The median eye nerves form a small optic lamella and optic ganglia, connected to the central body through an optic tract. Each posterior median and posterior lateral eye nerve ends in large optic lamellae (Fig. 13a). These are connected through chiasmata to a large optic mass where fibres from globuli cells form conspicuous glomeruli. There are 10–12 large fibres (diameter 9 m) of unknown origin on each side, terminating in the optic lambella of the posterior lateral eye.The central body, another neuropil mass (Fig. 13b) in the protocerebrum, is well developed in Cupiennius and located transversely in its postero-dorsal region (Fig. 10d). It consists of two layers and is interconnected with optic masses of the median and lateral eyes through optic tracts. Fibre tracts from the brain and suboesophageal mass join the central body.     

Purification, cDNA structure and biological significance of a single insulin-like growth factor-binding domain protein (SIBD-1) identified in the hemocytes of the spider Cupiennius salei

Cupiennius salei single insulin-like growth factor-binding domain protein (SIBD-1), which exhibits an IGFBP N-terminal domain-like profile, was identified in the hemocytes of the spider C. salei. SIBD-1 was purified by RP-HPLC and the sequence determined by a combination of Edman degradation and 5′–3′- RACE PCR. The peptide (8676.08 Da) is composed of 78 amino acids, contains six intrachain disulphide bridges and carries a modified Thr residue at position 2. SIBD-1 mRNA expression was detected by quantitative real-time PCR mainly in hemocytes, but also in the subesophageal nerve mass and muscle. After infection, the SIBD-1 content in the hemocytes decreases and, simultaneously, the temporal SIBD-1 expression seems to be down-regulated. Two further peptides, SIBD-2 and IGFBP-rP1, also exhibiting IGFBP N-terminal domain variants with unknown functions, were identified on cDNA level in spider hemocytes and venom glands. We conclude that SIBD-1 may play an important role in the immune system of spiders.     

Drop and swing dispersal behavior of a tropical wandering spider: experiments and numerical model

Summary When exposed to certain air flows spiderlings of the wandering spider Cupiennius getazi (Ctenidae) drop from their dwelling plant and swing in the wind from a gradually lengthening dragline. If body contact is made with a nearby substrate the spiderling detaches. We refer to this form of aerial dispersal as the drop and swing dispersal behavior (DASDB). The dragline being only up to about 70 cm long and only rarely ruptured by the drag forces of the wind, this is a close range type of dispersal as opposed to the ballooning known for many other species of spiders. DASDB is readily elicited in spiderlings at an age of ca. 9 days (outside egg sac). At this age their mass is 1.26 ±0.35 mg and their yolk usually depleted. They then start to catch prey and escape from the unfavorable conditions in the small space around the egg sac where hundreds of spiderlings compete. Air flow rates effectively eliciting DASDB in the laboratory are between 0.2 m/s and 1.5 m/s. The number of spiderlings showing DASDB increases considerably if the air flow is turbulent as opposed to laminar. A numerical model defining the window within which DASDB is supported mechanically was developed from theoretical considerations. Taking the effective wind speeds and the mechanical properties of the dragline, the model accounts very well for the fact that actual rupture of the dragline was observed only rarely in C. Getazi. Other features of the DASDB are also correctly predicted. The model is not only applicable to DASDB but also to the drop and swing preballooning behavior known to occur in several other species of spiders.Abbreviations DASDB drop and swing dispersal behavior     

The synaptic organization of visual interneurons in the lobula complex of flies

Summary The synaptic organization of three classes of cobalt-filled and silver-intensified visual interneurons in the lobula complex of the blowfly Calliphora (Col A cells, horizontal cells and vertical cells) was studied electron microscopically. The Col A cells are regularly spaced, columnar, small field neurons of the lobula, which constitute a plexus of arborizations at the posterior surface of the neuropil and the axons of which terminate in the ventrolateral protocerebrum. They show postsynaptic specializations in the distal layer of their lobula-arborizations and additional presynaptic sites in a more proximal layer; their axon terminals are presynaptic to large descending neurons projecting into the thoracic ganglion. The horizontal and vertical cells are giant tangential neurons, the arborizations of which cover the anterior and posterior surface of the lobula plate, respectively, and which terminate in the perioesophageal region of the protocerebrum. Both classes of these giant neurons were found to be postsynaptic in the lobula plate and pre- and postsynaptic at their axon terminals and axon collaterals. The significance of these findings with respect to the functional properties of the neurons investigated is discussed.     

N6-甲基化腺嘌呤RNA甲基化修饰在中枢神经系统中的作用研究进展

mRNA存在多种转录后修饰,这些修饰调控mRNA的稳定和剪接、翻译、转运等多个过程,进而影响细胞发育、机体免疫、学习认知等重要生理功能。其中m⁶A修饰是转录后修饰中最丰富的一种,广泛存在于mRNA中,调控mRNA的代谢活动,影响基因表达。m⁶A修饰的稳态对神经系统的发育和功能维持至关重要。近年研究发现,在神经退行性疾病、精神疾病和脑肿瘤中均存在m⁶A修饰的身影。因此本文对近几年m⁶A甲基化修饰在中枢神经系统发育、功能及相关疾病中的作用进行总结,为神经系统疾病提供潜在的临床治疗靶点。     

Two-dimensional gel analysis of proteins in cell lines from the central nervous system of larvalDrosophila

Summary High resolution two-dimensional gel electrophoresis was used to quantitatively analyze the patterns of protein synthesis in three different clones of a nerve cell line (ML-DmBG2) ofDrosophila melanogaster. When patterns of pulse-labeled proteins of the three different clones were compared, I observed quantitative variations affecting the rate of synthesis by twofold or more in 25–30% of the polypeptides and qualitative differences, always affecting less than 2% of the polypeptides. Patterns of protein synthesis were analyzed during the 24 d of culture, revealing both quantitative (increase or decrease; 40%) and qualitative (presence or absence; 3%) differences. More than 70 proteins synthesized in these cultures were secreted into the medium. Among them were two major groups of acidic proteins which disappeared with culture time. When cell lines and intact central nervous systems were compared, large differences in protein synthesis were observed. In fact, only 20% of the synthesized proteins were common to both isolated cells grownin vitro and the original nervous systemin vivo.     

Immunohistochemical investigation of neuropeptides in the central nervous system of the amphioxus,Branchiostoma belcheri

The immunohistochemical localization of nine different neuropeptides was studied in the central nervous system of the amphioxus, Branchiostoma belcheri. In the brain, perikarya immunoreactive for urotensin I and FMRFamide were localized in the vicinity of the central canal. One of the processes of each of these perikarya was found to cross the dorso ventral slit-like lumen of the central canal. Oxytocin-immunoreactive short fibers, but not perikarya, were detected in the ventral part of the brain. Perikarya immunoreactive for arginine vasopressin/vasotocin, oxytocin and FMRFamide were widely distributed in the spinal cord. Arginine vasopressin/vasotocin-immunoreactive fibers often made contacts with Rohde cell axons. Angiotensin II-immunoreactive perikarya were observed in the posterior half of the spinal cord, and urotensin I-immunoreactive perikarya were found in the caudal region of the spinal cord. Cholecystokinin/gastrin-immunoreactive fibers, but not perikarya, were detected in the spinal cord; some extended as far as the ependymal layer of the cerebral ventricle. No colocalization of the peptides examined was observed. No immunoreactivity for atrial and brain natriuretic peptides nor for urotensin II was detected. The present study indicates that there are at least six separate neuronal systems that contain different peptides, respectively, in the central nervous system of the amphioxus. Their functions remain to be determined.Part of this investigation has previously been presented in abstract form (Uemura et al. 1989)     

Distribution of serotonin-containing neurons in the central nervous system of the snail Helix pomatia

Summary The distribution of serotonin (5HT)-containing neurons in the central nervous system of the snail Helix pomatia has been determined in whole-mount preparations by use of immunocytochemical and in vivo 5,6-dihydroxy-tryptamine labelling. 5HT-immunoreactive neuronal somata occur in all but the buccal and pleural ganglia. Immunoreactive fibres are present throughout the central nervous system. The 5HT-immunoreactive neuronal somata characteristically appear in groups, located mainly in the cerebral, pedal, visceral and right parietal ganglia. The majority of 5HT-immunoreactive neurons is located in the pedal ganglia. Additionally a dense network of 5HT-immunoreactive varicose fibres is found in the neural sheath of the central nervous system including all the nerves and ganglia. The number and distribution of 5HT-immunoreactive neurons correlates with that demonstrated by 5,6-dihydroxytryptamine labelling method.     

Dissecting planarian central nervous system regeneration by the expression of neural-specific genes

The planarian central nervous system (CNS) can be used as a model for studying neural regeneration in higher organisms. Despite its simple structure, recent studies have shown that the planarian CNS can be divided into several molecular and functional domains defined by the expression of different neural genes. Remarkably, a whole animal, including the molecularly complex CNS, can regenerate from a small piece of the planarian body. In this study, a collection of neural markers has been used to characterize at the molecular level how the planarian CNS is rebuilt. Planarian CNS is composed of an anterior brain and a pair of ventral nerve cords that are distinct and overlapping structures in the head region. During regeneration, 12 neural markers have been classified as early, mid-regeneration and late expression genes depending on when they are upregulated in the regenerative blastema. Interestingly, the results from this study show that the comparison of the expression patterns of different neural genes supports the view that at day one of regeneration, the new brain appears within the blastema, whereas the pre-existing ventral nerve cords remain in the old tissues. Three stages in planarian CNS regeneration are suggested.