The locust abdominal muscle receptor organ: response characteristics and its role in the control of segmental distance

A single mutipolar receptor cell is located at the dorsal edge of the lateral internal dorsal muscle in each abdominal segment of the locust (Locusta migratoria). Muscle and receptor cell form the abdominal muscle receptor organ. The receptor cell monitors length changes in the intersegmental muscle, and as a consequence also detects the length of an abdominal segment (cuticule and intersegmental membrane).The muscle receptor organ responds in a phasictonic fashion. The phasic component encodes the rate of change in the stimulus independent from the prevailing length of the muscle receptor organ. The tonic component monitors the absolute length of the muscle.Stimulation of a single muscle receptor organ leads to reflex effects on the ipsilateral longitudinal muscles in at least three adjacent segments. Muscles that shorten the abdomen are activated while their extending antagonists receive reduced activity.The reflex activation of the muscles is polysynaptic. Monosynaptic connections between the receptor and the motoneurones were not found.We identified an interneurone that receives monosynaptic input from the muscle receptor organs in at least three adjacent segments. The interneurone excites motorneurones to the longitudinal muscles of the next posterior segment.Abbreviations aMROII abdominal muscle receptor interneurone 1 - AS3 third abdominal segment - AS4 fourth abdominal segment - AS5 fifth abdominal segment - AS6 sixth abdominal segment - EPSP excitatory postsynaptic potential - MN median nerve - MR multipolar receptor cell - MRO muscle receptor organ - N1 tergal nerve - N2 sternal nerve     

Motor supply of the dorsal longitudinal muscles,I: homonomy and ontogeny of the motoneurones in locusts (Insecta,Caelifera)

The neural supply of the dorsal lingitudinal muscles in successive segments from the prothorax to the pregenital abdomen of adult and larval instar locusts (Locusta migratoria and Schistocerca gregaria) has been studied. Stainings have also been carried out for embryos. The whole complement consists of three muscles, of which one or both of the smaller ones degenerate in the pterothoracic segments during early imaginal life. Based on morphological criteria, several motoneurone types can be distinguished. The neural set is almost identical for all segments, independent of the general organization of each segment. At about 65% of embryogenesis, all neurone types can be identified with respect to soma position and basic features of the central branching pattern. By the end of embryogenesis, a dendritic pattern is established which resembles the adult pattern in all major aspects. The reiteration of homonomous elements suggests that they form part of the basic segmental neural Bauplan generated early in embryogenesis. This study of muscles and motoneurones forming identifiable, reiterated neuromuscular units can serve as a segmental matrix for a comparative study comprising other phylogenetic groups of the Tracheata.Abbreviations DLM dorsal longitudinal muscle - DUM dorsal unpaired median - M muscle (number) - MN motoneurone - N nerve (number)     

Edge effects and intraguild predation in native and introduced centipedes: evidence from the field and from laboratory microcosms

Human alteration of habitat has increased the proportion of forest edge in areas of previously continuous forest. This edge habitat facilitates invasion of exotic species into remaining fragments. The ability of native species to resist invasion varies and may depend on intrinsic variables such as dispersal and reproductive rates as well as external factors such as rate of habitat change and the density of populations of introduced species in edge habitat. We examined the distributional and competitive relationships of two members of the class Chilopoda, Scolopocryptops sexspinosus, a centipede native to the eastern US, and Lithobius forficatus, an exotic centipede introduced from Europe. We found that L. forficatus was most abundant in edge habitat and S. sexspinosus was most abundant in the interior habitat at our field sites. Although L. forficatus was present in habitat interiors at 11 of 12 sites, there was no correlation between fragment size and numbers of L. forficatus in interior habitat. The native centipede was rarely found occupying fragment edges. We used laboratory microcosms to examine potential competitive interactions and to indirectly assess prey preferences of the two species. In microcosms both species consumed similar prey, but the native centipede, S. sexspinosus, acted as an intraguild predator on the introduced centipede. Native centipedes were competitively superior in both intraspecific and interspecific pairings. Our results suggest that intraguild predation may aid native centipedes in resisting invasion of introduced centipedes from edge habitat.     

Homonomies within the ventral muscle system and the associated motoneurons in the locust,Schistocerca gregaria (Insecta,Caelifera)

To understand the segmental reiteration of an insect, the serially arranged neuromuscular system of the locust, Schistocerca gregaria, is studied. The ventral muscle system is chosen and its motoneuronal supply is described in the thoracic and pregenital segments. In general, repetitively arranged, similar sets of motoneurons (MNs) supply the ventral muscles of these segments. Common criteria of both topology of muscles and neural features (nerve branches and motoneuronal supply) suggest possible homonomies of the ventral longitudinal muscles and ventral diaphragm of the thoracic and abdominal system. Based on a segment-by-segment analysis, muscle topology and motor supply match, in most instances. There are, however, cases where such a parallelism is missing. In a particular cases the supply of apparently homonomous muscles shifts from one set of MNs to another. In another case, putatively equivalent MNs of different ganglia supply morphologically different muscle structures in the adult animal. Therefore, it becomes apparent that muscles and their supplying MNs are, in principle, independent elements which might be subjected autonomously to ontogenetic processes. As a consequence, in the search for the basic segmental Bauplan depending on homonomous structures, muscles and MNs have to be regarded as separate entities.Abbreviations A1–6 abdominal ganglion (or neuromere A1–3) - AS1–6 abdominal segment 1–6 - DUM doisal unpaired median - M muscle (number) - MN motoneuron - N nerve (number) - PMN paramedian nerve - T1–3 pro-, meso-, metathoracic ganglion - TS1–3 pro-, meso-, metathoracic segment - VD ventral diaphragm - VM ventral muscle     

Abdominal stretch reception in Dipetalogaster maximus (Hemiptera: Reduviidae)

Each half abdominal segment in 5th-instar larvae of the giant bloodsucking reduviid, Dipetalogaster maximus, contains 3 stretch receptor neurones, one associated with the tergosternal muscles, one with the ventral intersegmental muscles and one with the dorsal intersegmental muscles. Each of the three receptors respond phasically to the onset of stretch in its respective muscle group, but none show persistent activity upon prolonged stretch. By contrast, stretch of the main abdominal nerves (which run between the thoracic ganglion and the ventral intersegmental muscles of each abdominal segment) is accompanied by a prolonged and sustained pattern of discharge by an as yet unidentified neurone, the rate of discharge being proportional to the degree of stretch. In life, the abdominal nerves become stretched to about 145% of their resting length when the larva takes a bloodmeal. Thus it appears that in Dipetalogaster stretch of the abdominal nerves themselves is the only mechanism for stretch reception after a blood meal.     

The musculature of Draculiciteria tessalata (Chaetonotida, Paucitubulatina): implications for the evolution of dorsoventral muscles in Gastrotricha

The muscular system of the marine interstitial gastrotrich Draculiciteria tessalata (Chaetonotida, Paucitubulatina) was analyzed with fluorescent phalloidin. Muscles in circular, longitudinal, helicoidal and dorsoventral orientations were found. Circular muscles were present as discreet rings on the pharynx only. Five pairs of longitudinal muscles were found in dorsal, lateral and ventral positions. One of the two pairs of lateral muscles is newly described for the species. Helicoidal muscles, external to the circular muscles and some longitudinal bands, spiraled around the pharynx and anterior portion of the intestine. Two pairs of segmentally-arranged dorsoventral muscles were also present. Lateral dorsoventral muscles extended from the base of the pharynx to the anterior part of the caudal furca. Medial dorsoventral muscles extended from the pharyngeal-intestinal junction into each ramus of the caudal furca. A hypothesis on the evolution of dorsoventral muscles in D. tessalata is proposed which includes a splitting of circular muscles into separate somatic and splanchnic components with a further displacement of both muscle sets into a dorsoventral orientation.     

Early Metamorphic Insertion Technology for Insect Flight Behavior Monitoring

Early Metamorphosis Insertion Technology (EMIT) is a novel methodology for integrating microfabricated neuromuscular recording and actuation platforms on insects during their metamorphic development. Here, the implants are fused within the structure and function of the neuromuscular system as a result of metamorphic tissue remaking. The implants emerge with the insect where the development of tissue around the electronics during pupal development results in a bioelectrically and biomechanically enhanced tissue interface. This relatively more reliable and stable interface would be beneficial for many researchers exploring the neural basis of the insect locomotion with alleviated traumatic effects caused during adult stage insertions. In this article, we implant our electrodes into the indirect flight muscles of Manduca sexta. Located in the dorsal-thorax, these main flight powering dorsoventral and dorsolongitudinal muscles actuate the wings and supply the mechanical power for up and down strokes. Relative contraction of these two muscle groups has been under investigation to explore how the yaw maneuver is neurophysiologically coordinated. To characterize the flight dynamics, insects are often tethered with wires and their flight is recorded with digital cameras. We also developed a novel way to tether Manduca sexta on a magnetically levitating frame where the insect is connected to a commercially available wireless neural amplifier. This set up can be used to limit the degree of freedom to yawing “only” while transmitting the related electromyography signals from dorsoventral and dorsolongitudinal muscle groups.     

Musculature and innervation of the neck of the desert locust,Schistocerca gregaria (Forskål)

The innervation of each of the muscles involved in mediating head movement in the desert locust Schistocerca gregaria is described in detail. The number of motor neurones to each muscle and the neutral pathway and ganglion of origin of each are deduced from both histological and electrophysiological evidence. Only two of the muscles are, on histological evidence, innervated by as few as four different neurones, while several receive more than ten, and one at least 13. Individual muscles are shown physiologically to receive, in a few cases, as many as six different motor neurones. At least six muscles are innervated by motor neurones originating in more than one ganglion. One group of four muscles consisting in total of less than 100 muscle fibres receives more than 20 different motor neurones from three different ganglia through three or four different nerve roots. In these muscles, many single muscle fibres receive innervation from at least two different ganglia. It is concluded that the segmental nature of an insect muscle can not be deduced solely from a knowledge of the ganglion of origin of the motor innervation to that muscle. The innervation patterns that exist today must reflect past evolutionary development, but changes in the peripheral distribution of motor neurones, or migration of motor neurone cell bodies from one ganglion to another, or the development of additional motor neurones, or several of these factors together, must have formed a part of that development.     

Metamorphosis of the ecdysis motor pattern in the hawkmoth, Manduca sexta

Summary The hawkmoth,Manduca sexta, under-goes periodic molts during its growth and metamorphosis. At the end of each molt, the old cuticle is shed by means of a hormonally-activated ecdysis behavior. The pharate adult, however, must not only shed its old cuticle but also dig itself out from its underground pupation chamber. To accomplish this, the adult performs a series of abdominal retractions and extensions; the extensions are coupled with movements of the wing bases. This ecdysis motor pattern is distinct from the slowly progressing, anteriorly-directed, abdominal peristalses expressed by ecdysing larvae and pupae.We have found that the ability to produce the larval-like ecdysis pattern is retained in the adult. Although this behavior is not normally expressed by the adult, larval-like ecdysis could be unmasked when descending neuronal inputs, originating in the pterothoracic ganglion, were removed from the unfused abdominal ganglia. Transformation of the adult-specific ecdysis pattern to the larval-like pattern was accomplished by transecting the connectives between the pterothorax and the abdomen, or by reversibly blocking neuronal activity with a cold-block. A comparative analysis of the ecdysis motor patterns expressed by larvae and by isolated adult abdomens indicates that the two motor patterns are indistinguishable, suggesting that the larval ecdysis motor pattern is retained through metamorphosis. We speculate that its underlying neural circuitry is conserved through development and later modulated to produce the novel ecdysis pattern expressed in the adult stage.Abbreviations A(n) nth abdominal segment - DL dorsal longitudinal - EH eclosion hormone - ISMs intersegmental muscles - MN motoneuron - SEG subesophageal ganglion - T1,T2,T3 prothoracic, mesothoracic, and metathoracic ganglion - TSMs tergosternal muscles - TX thorax     

Organization of the dorsoventral musculature in the wings of the pteropod mollusc Clione limacina

The wings of the pteropod mollusc Clione limacina provide forward propulsive force through flapping movements in which the wings bend throughout their length in both dorsal and ventral directions. The musculature of the wings includes oblique, striated muscle bundles that generate the swimming movements of the wings, longitudinal and transverse (smooth) muscle bundles that collapse the wings and pull them into the body during a wing withdrawal response, and dorsoventral muscles that control the thickness of the wings. All muscles act against a hydrostatic skeleton that forms a central hemocoelic space within the wings. Of these muscle types, all have been thoroughly described and studied except the dorsoventral muscles. The fortuitous discovery that the dorsoventral musculature can be intensely labeled with an antibody against the vertebrate hyperpolarization‐activated cation channel (HCN2) provided the opportunity to describe the organization of the dorsoventral musculature in detail. In addition, electrical recordings and microelectrode dye injections supported the immunohistochemical data, and provided preliminary data on the activity of the muscle fibers. The organization and activity of the dorsoventral musculature suggests it may be involved in regulation of wing stiffness during the change from slow to fast swimming.     

Evolutionary origin of the insect wing via integration of two developmental modules

SUMMARY Insect wing is a key evolutionary innovation for insect radiation, but its origins and intermediate forms are absent from the fossil record. To understand the ancestral state of the wing, expression of three key regulatory genes in insect wing development, wingless (wg), vestigial (vg), and apterous (ap) was studied in two basal insects, mayfly and bristletail. These basal insects develop dorsal limb branches, tracheal gill and stylus, respectively, that have been considered candidates for wing origin. Here we show that wg and vg are expressed in primordia for tracheal gill and stylus. Those primordia are all located in the lateral body region marked by down‐regulation of early segmental wg stripes, but differ in their dorsal–ventral position, indicating their positions drifted within the lateral body region. On the other hand, ap expression was detected in terga of mayfly and bristletail. Notably, the extensive outgrowth of the paranotal lobe of apterygote bristletail developed from the border of ap‐expressing tergal margin, and also expressed wg and vg. The data suggest that two regulatory modules involving wg–vg are present in apterygote insects: one associated with lateral body region and induces stick‐like dorsal limb branches, the other associated with the boundary of dorsal and lateral body regions and the flat outgrowth of their interface. A combinatorial model is proposed in which dorsal limb branch was incorporated into dorsal–lateral boundary and acquired flat limb morphology through integration of the two wg–vg modules, allowing rapid evolution of the wing.     

The phylogenetic interrelationships of the higher taxa of apterygote hexapods

The phylogeny of the basal hexapods, the so-called apterygote insects, was studied using parsimony analysis procedures. Most analyses took into account 47 characters mainly based on external morphology, and 19 taxa including 14 apterygote representatives, 3 pterygotes and also 2 distantly related myriapods were used as outgroups. The binary and multistate characters are discussed in detail and treated as unordered and equally weighted. Other analyses were performed using a second data set in which 28 characters, based on internal anatomy and already used in a previous work ( Bitsch & Bitsch 1998 ), were added to the first data set. This second matrix was restricted to 12 terminal taxa, the same as those of our previous work. The results of the different analyses are generally congruent. They strongly support the monophyly of several orders (Protura, Collembola, Archaeognatha) and of two groupings (Ectognatha, Dicondylia). Three other assemblages (Ellipura, Diplura, Entognatha) appear as parsimonious phylogenetic hypotheses, but they are never supported by the cladistical analyses and are based on a very small number of autapomorphies; so, the monophyly of each of them is not firmly established. Archaeognatha appears as the sister group of the Dicondylia. The three unresolved representatives of the Zygentoma are found as the sister group of the Pterygota. The results are discussed in the light of current concepts in hexapod phylogeny.     

Muscular architecture of <Emphasis Type="Italic">Milnesium tardigradum </Emphasis>and <Emphasis Type="Italic">Hypsibius </Emphasis>sp. (Eutardigrada,Tardigrada) with some data on <Emphasis Type="Italic">Ramazottius oberhaeuseri</Emphasis>

The architecture of the musculature of the eutardigrade species Milnesium tardigradum Doyère, 1840, Hypsibius sp. and Ramazzottius oberhaeuseri (Doyère in Ann Sci Nat Zool Sér 2(14):269–369, 1840) is investigated by phalloidin staining and confocal laser scanning microscopy. There are methodological problems in staining eutardigrades due to physiological alterations under stress (anhydrobiosis) and due to penetration problems of the cuticle. It is helpful to fix specimens in the state of asphyxy, where animals are stretched following an oxygen shortage in their environment. The musculatures of all three species correspond in their general architecture, but differ in detail, such as in the number of muscles. All muscles are isolated muscle strands. There are on each body side two dorsal and one ventral muscle strands, in addition to a system of dorsoventral, lateral and lateroventral muscles. Seven median ventral attachment points give rise to dorsoventral, ventrolateral and appendage muscles. The appendages receive several muscles originating dorsally and ventrally. The number of muscles and the arrangement differ in each appendage. The fourth appendage shows the greatest differences with a far smaller number of muscles compared to other species. The musculature shows comparably few strict segmental patterns, for example, the musculature of each appendage differs from the other ones. By comparison with literature data on the same species and data of Macrobiotus hufelandi it can be shown that eutardigrades have a roughly comparable muscular architecture, but that there are several differences in detail. Dedicated to Professor Westheide on the occasion of his 70th birthday.     

Comparative myoanatomy of cycliophoran life cycle stages

The metazoan phylum Cycliophora includes small cryptic epibionts that live attached to the mouthparts of clawed lobsters. The life cycle is complex, with alternating sexual and asexual generations, and involves several sessile and free‐living stages. So far, the morphological and genetic characterization of cycliophorans has been unable to clarify the phylogenetic position of the phylum. In this study, we add new details on the muscular anatomy of the feeding stage, the attached Prometheus larva, the dwarf male, and the female of one of the two hitherto described species, Symbion pandora. The musculature of the feeding stage is composed of myofibers that run longitudinally in the buccal funnel (two fibers) and in the trunk (variable number of fibers). The mouth opening is lined by a myoepithelial ring musculature. A complex myoepithelial sphincter is situated proximal to the anus. In the attached Prometheus larva, three longitudinal sets of myofilaments run dorsally, laterally, and ventrally along the entire anterior‐posterior body axis. The muscular architecture of the dwarf male is complex, especially close to the penis, in the posterior part of the body. An X‐shaped muscle structure is found on the dorsal side, whereas on the ventral side, longitudinal muscles and a V‐shaped muscle structure are present. These muscles are complemented by additional dorsoventral muscles. The mesodermal muscle fibers attach to the cuticle via the epidermis in all life cycle stages studied herein. The musculature of the female is similar to that of the Pandora larva of Symbion americanus and includes dorsoventral muscles and longitudinal muscles that run in the dorsal and ventral body region. Overall, our results reveal striking similarities in the muscular arrangement of the life cycle stages of both Symbion species. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Drosophila neural pathways

Summary TheDrosophila giant axon pathways cervical connective — thoracic indirect flight muscles were studied by a combined electrophysiological and genetic analysis. A functional coupling of the left and right giant axon pathways was revealed by intracellular recordings of electrical responses of the thoracic indirect flight muscles, when evoked by electrical stimulation of cervical connective (Fig. 2). This functional coupling was demonstrated in wild-type flies and in flies of the single gene, temperature-sensitive paralytic mutation,para ^ts . The functional coupling was evident also in selected bilateral gynandromorph flies, mosaics for thepara ^ts mutation (Fig. 1), even at restricted elevated ambient temperature (Tables 1–3). Analysis of neurally evoked electrogenic muscle responses of wild-type flies, following injection of picrotoxin, verifies the notion that both the dorsoventral and the dorsolongitudinal flight muscles share a common activating pathway (Fig. 3). Picrotoxin application to gynandromorph flies demonstrated the existence of neuronal elements additional to the giant axon pathways, that evoke the indirect flight muscles in response to cervical stimulation (Figs. 4, 5). An unexpected finding was the poor correlation between the mosaic external phenotype of the gynandromorph flies ofpara ^ts mutation and the genotype of neural pathways activating their thoracic flight muscles, as evidenced by the intracellular recordings.Abbreviations GA giant axon - DVM dorsoventral muscle - DLM dorsolongitudinal muscle - PSI peripherally synapsing interneuron - ts temperature sensitive     

Ultrastructure and regeneration of midgut epithelial cells in Lithobius forficatus (Chilopoda,Lithobiidae)

Lithobius forficatus (Myriapoda, Chilopoda, Lithobiidae) is a widespread species of centipede that is common across Europe. Its midgut epithelial cells are an important line of defense against toxic substances that originate in food, such as pathogens and metals. Despite this important role, the biology of the midgut epithelium is not well known. Here we describe the ultrastructure of the midgut epithelium, as well as the replacement of degenerated midgut epithelial cells. The midgut epithelium of L. forficatus is composed of digestive, secretory, and regenerative cells. The cytoplasm of digestive cells shows regionalization in organelle distribution, which is consistent with the role of these cells in secretion of enzymes, absorption of nutrients, and accumulation of lipids and glycogen. Secretory cells, which do not reach the luminal surface of the midgut epithelium, possess numerous electron‐dense and electron‐lucent granules and may have an endocrine function. Hemidesmosomes anchor secretory cells to the basal lamina. Regenerative cells play the role of midgut stem cells, as they are able to proliferate and differentiate. Their proliferation occurs in a continuous manner, and their progeny differentiate only into digestive cells. The regeneration of secretory cells was not observed. Mitotic divisions of regenerative cells were confirmed using immunolabeling against BrdU and phosphohistone H3. Hemocytes associate with the midgut epithelium, accumulating between the visceral muscles and beneath the basal lamina of the midgut epithelium. Hemocytes also occur among the digestive cells of the midgut epithelium in animals infected with Rickettsia‐like microorganisms. These hemocytes presumably have an immunoprotective function in the midgut.     

Antennal motor system of the cockroach, <Emphasis Type="Italic">Periplaneta americana</Emphasis>

The organization of the antennal muscles, nerves, and motor neurons has been investigated in the cockroach, Periplaneta americana. Antennal movements have been observed by video analysis, muscle actions have been determined by dissection and direct mechanical testing, and the motor neurons innervating each muscle have been defined with a recently developed selective backfill method. A model of the antennomotor system of Periplaneta has thus been established and compared with that of crickets. Five muscles located within the head capsule insert on the most proximal antennal segment, the scape. By their action, they allow the scape to move in essentially any direction within the dorsoventral and anteroposterior planes. An additional pair of muscles, one dorsal and one ventral, are found within the scape. They insert on the pedicel and move the pedicel in the dorsal-ventral plane. These seven muscles are controlled by at least 17 motor neurons with somata located in the deutocerebrum. By their action, these motor neurons enable cockroaches to move the long flagellum of each antenna through a wide range of positions in the frontal space, medio-laterally, and also allow depression toward the substrate and elevation well above the level of the head. The antennal motor neurons have been classified into five morphological types based on soma and axon location. Each morphological type has been correlated with a particular pattern of muscle innervation and control. The neurites of all motor neurons are located along the medial aspect of the dorsal lobe of the deutocerebrum. This research was supported by grant nos. IBN 96-04629 and 04-22883 from the National Science Foundation.     

Numbers and biomass of centipedes (Lithobiomorpha: Chilopoda) in a Betula-Alnus woodland in N.E. England

Summary Over a period of 1 year the mean monthly population densities of L. forficatus varied between 7.58 m^-2 (February) and 24.07 m^-2 (October). The equivalent values for L. crassipes were 17.05 m^-2 (February) and 64.17 m^-2 (October). The annual mean population density of the two species was estimated at 51 m^-2 with a biomass of 0.585 g live wt m^-2. Less than 4% of the total lithobiid population was found in decaying logs and tree stumps, most of the population inhabited the soil/litter layers.Seasonal fluctuation in numbers was shown to be unimodal in L. forficatus and bimodal in L. crassipes. A similar pattern was noted in the status of the ovaries, L. forficatus appears to have a single peak breeding period (September) while L. crassipes has two (June and September).In terms of biomass, the relative importance of centipedes among other woodland invertebrate predators is high.     

The whole-body shortening reflex of the medicinal leech: motor pattern,sensory basis,and interneuronal pathways

The leech whole-body shortening reflex consists of a rapid contraction of the body elicited by a mechanical stimulus to the anterior of the animal. We used a variety of reduced preparations — semi-intact, body wall, and isolated nerve cord — to begin to elucidate the neural basis of this reflex in the medicinal leech Hirudo medicinalis. The motor pattern of the reflex involved an activation of excitatory motor neurons innervating dorsal and ventral longitudinal muscles (dorsal excitors and ventral excitors respectively), as well as the L cell, a motor neuron innervating both dorsal and ventral longitudinal muscles. The sensory input for the reflex was provided primarily by the T (touch) and P (pressure) types of identified mechanosensory neuron. The S cell network, a set of electrically-coupled interneurons which makes up a fast conducting pathway in the leech nerve cord, was active during shortening and accounted for the shortest-latency excitation of the L cells. Other, parallel, interneuronal pathways contributed to shortening as well. The whole-body shortening reflex was shown to be distinct from the previously described local shortening behavior of the leech in its sensory threshold, motor pattern, and (at least partially) in its interneuronal basis.Abbreviations conn connective - DE dorsal excitor motor neuron - DI dorsal inhibitor motor neuron - DP dorsal posterior nerve - DP:B1 dorsal posterior nerve branch 1 - DP:B2 dorsal posterior nerve branch 2 - MG midbody ganglion - VE ventral excitor motor neuron - VI ventral inhibitor motor neuron