Change in take‐off elevation angle after limb autotomy mitigates the reduction in jumping distance in rice grasshoppers Oxya yezoensis

Autotomy is the ability to spontaneously self‐amputate a limb or other appendage, often as a reflexive action. This limb amputation typically occurs as a specialized defensive response to an attack from a predator and thereby enables the prey to escape from predation. Despite the benefits of escape, autotomized organisms lose the body part and its associated function. Here, we investigated the jumping behavior and performance of one‐leg‐autotomized and intact rice grasshoppers, Oxya yezoensis, to examine changes in jumping behavior after autotomy. The take‐off elevation of autotomized grasshoppers was 7.8° lower than in intact grasshoppers, resulting in nearly a 45° angle of take‐off, which maximized the jumping distance. Kinematic analyses of the jumping manner revealed that the angle of the femur during jumping differed between intact and autotomized grasshoppers, suggesting that the grasshoppers behaviorally change the take‐off elevation after autotomy. According to analyses of jumping performance, the degree of decline in performance differed between horizontal distance and vertical height. Even though they jumped on only one hind leg, one‐leg‐autotomized grasshoppers realized 69% performance along a horizontal distance relative to intact grasshoppers. In contrast, autotomized grasshoppers realized only a 44% performance in vertical height compared to intact grasshoppers. The difference in take‐off elevation between autotomized and intact grasshoppers is likely related to the observed difference in the magnitude of the decline in performance between horizontal distance and vertical height. These results suggest that rice grasshoppers may alter their take‐off elevation after limb autotomy to minimize the reduction in jumping distance.     

Regeneration and autotomy exhibited by the Black Widow spider,Latrodectus variolus walckenaer

Summary Crustaceans, insects and to a lesser degree arachnids have been employed in regeneration studies. Amputation and ligation of the legs was used to determine occurring in a Black Widow spider complied with the developmental gradient model of regeneration. The occurrence of autotomy in this species was also documented. Amputation indicated the most proximal point from which regeneration of the leg could occur was the femoral mid-point. Amputation proximal to that area did not result in leg regeneration. Autotomy following amputation was not observed. Ligation of the legs resulted in autotomy when applied at and proximal to the mid-point of the tibia, increasing in frequency as more proximal segments were ligated. Autotomy always occurred at the trochanter-coxa joint. Autotomized legs did not regenerate. The regeneration observed complied with the developmental gradient model.     

Scorpion Sheds ‘Tail’ to Escape: Consequences and Implications of Autotomy in Scorpions (Buthidae: Ananteris)

Autotomy, the voluntary shedding or detachment of a body part at a determined cleavage plane, is a common anti-predation defense mechanism in several animal taxa, including arthropods. Among arachnids, autotomy has been observed in harvestmen, mites, and spiders, always involving the loss of legs. Autotomy of the opisthosoma (abdomen) was recently reported in a single species of the Neotropical buthid scorpion genus Ananteris Thorell, 1891, but few details were revealed. Based on observations in the field and laboratory, examination of material in museum collections, and scanning electron microscopy, we document autotomy of the metasoma (the hind part of the opisthosoma, or ‘tail’) in fourteen species of Ananteris. Autotomy is more common in males than females, and has not been observed in juveniles. When the scorpion is held by the metasoma, it is voluntarily severed at the joints between metasomal segments I and II, II and III, or III and IV, allowing the scorpion to escape. After detachment, the severed metasoma moves (twitches) automatically, much like the severed tail of a lizard or the severed leg of a spider, and reacts to contact, even attempting to sting. The severed surface heals rapidly, scar tissue forming in five days. The lost metasomal segments and telson cannot be regenerated. Autotomy of the metasoma and telson results in permanent loss of the posterior part of the scorpion’s digestive system (the anus is situated posteriorly on metasomal segment V) and the ability to inject venom by stinging. After autotomy, scorpions do not defecate and can only capture small prey items. However, males can survive and mate successfully for up to eight months in the laboratory. In spite of diminished predation ability after autotomy, survival allows males to reproduce. Autotomy in Ananteris therefore appears to be an effective, adaptive, anti-predation escape mechanism.     

Muscle degeneration following remote nerve injury

Muscle depends upon innervation and contraction to maintain a differentiated state. Denervation can therefore induce muscle atrophy. In grasshoppers, muscle degeneration can also be triggered by the severing of a leg during autotomy. In this case, the muscles that degenerate are neither damaged nor denervated. This phenomenon suggests the existence of transneuronal mechanisms that influence muscle survival. To characterize this autotomy-induced process, we studied the degeneration of a thoracic tergotrochanteral depressor muscle (M#133b,c) subsequent to the shedding of a hindlimb in the grasshoppers Barytettix psolus and Barytettix humphreysii. Both histochemical and electrophysiological methods were used to follow muscle degeneration 1, 3, 5, 10, and 15 days postautotomy. Muscle fibers began to show denervation-like electrophysiological changes (i.e., depolarized resting membrane potentials and postinhibitory rebound) as soon as 3 days postautotomy. By 10 days, significant muscle degeneration was evident and electrophysiological changes were found in all animals tested. Muscle anatomical degeneration was not induced by synaptic transmission failure, because neuromuscular transmission was maintained in most fibers. The rate of muscle degeneration was not constant. Between 1 and 10 days, mean fiber cross-sectional area did not change on the autotomized side, although this is normally a time of muscle growth. However after 10 days, cross-sectional area became drastically reduced and the number of muscle fibers within M#133b,c was decreased. The variability in rate of fiber degeneration was not dependent upon fiber type, since M#133b,c only contains fast-type fibers. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 497–508, 1998     

Control of muscle degeneration following autotomy of a hindleg in the grasshopper,Barytettix humphreysii

When the grasshopper, Barrytettix humphreysii, sheds a hindlimb during autotomy, certain thoracic muscles degenerate although they are neither directly damaged nor denervated. Muscle degeneration is induced when a leg nerve (N5) that does not innervate the thoracic muscles is severed. Together these results suggest that transneuronal mechanisms influence muscle survival. To further characterize this autotomy-induced process, we studied the degeneration of a thoracic tergotrochanteral muscle (M#133b,c) following autotomy or experimental manipulation in adult animals. Its degeneration is correlated with reduced activity of its neural input and occurs by programmed cell death (PCD). PCD onset is variable between individual muscle fibers, indicating that the trigger of degeneration is fiber specific. Muscle degeneration appears to be triggered by the loss of proprioceptive input from the autotomized limb, since severing of axons from proprioceptive organs, but not exteroceptive chemo- or mechanoreceptors, leads to muscle degeneration. Muscle disuse, neuronal degeneration, or changes in juvenile hormone titer do not appear to play a role in autotomy-induced degeneration. We propose that the loss of proprioceptive input from proximal campaniform sensilla on the tibia deafferents the thoracic muscle motor neurons and leads to a decrease in their activity. Muscle degeneration is ultimately triggered by the loss of normal neural activity.     

Proprioceptors and sensory nerves in the legs of a spider,Cupiennius salei (Arachnida,Araneida)

Summary Retrograde CoS-impregnation was used to trace and map the course of sensory nerves and the distribution and innervation of the various proprioceptor types in all leg segments of Cupiennius salei, a Ctenid spider.1. Sensory nerve branches. In both the tibia and femur, axons of all proprioceptor types ascend in just two lateral nerves which do not merge with the main leg nerve until they reach the next proximal joint region. In the short segments — coxa, trochanter, patella, and tarsus — axons of the internal joint receptors often run separately from those of the other sensilla. Axons of the large lyriform slit sense organ at the dorsal metatarsus and of the trichobothria join with only a few hair axons and form their own nerve branches (Figs. 1, 2, 3).2. Proprioceptors. Each of the seven leg joints is supplied with at least one set of the well-known internal joint receptors, slit sensilla (single slits and lyriform organs), and long cuticular hairs. In addition, we found previously unnoticed hair plates on both sides of the coxa, near the prosoma/coxa joint; they are deflected by the articular membrane during joint movements (Fig. 4).3. Sensory cells and innervation. CoS-impregnation shows that each slit of the slit sense organs — be it a single slit or several slits in a lyriform organ — is innervated by two bipolar sensory cells (Fig. 6). We also confirm previous reports of multiple innervation in the internal joint receptors and in the long joint hairs and cuticular spines.Most of the ascending nerve branches run just beneath the cuticle for at least a short distance (Fig. 5); hence they are convenient sites for electrophysiological recordings of sensory activity even in freely walking spiders.     

The thoracic muscular system and its innervation in third instar Calliphora vicina Larvae. II. Projection patterns of the nerves associated with the pro‐ and mesothorax and the pharyngeal complex

We describe the anatomy of the nerves that project from the central nervous system (CNS) to the pro‐ and mesothoracic segments and the cephalopharyngeal skeleton (CPS) for third instar Calliphora larvae. Due to the complex branching pattern we introduce a nomenclature that labels side branches of first and second order. Two fine nerves that were not yet described are briefly introduced. One paired nerve projects to the ventral arms (VAs) of the CPS. The second, an unpaired nerve, projects to the ventral surface of the cibarial part of the esophagus (ES). Both nerves were tentatively labeled after the structures they innervate. The antennal nerve (AN) innervates the olfactory dorsal organ (DO). It contains motor pathways that project through the frontal connectives (FC) to the frontal nerve (FN) and innervate the cibarial dilator muscles (CDM) which mediate food ingestion. The maxillary nerve (MN) innervates the sensory terminal organ (TO), ventral organ (VO), and labial organ (LO) and comprises the motor pathways to the mouth hook (MH) elevator, MH depressor, and the labial retractor (LR) which opens the mouth cavity. An anastomosis of unknown function exists between the AN and MN. The prothoracic accessory nerve (PaN) innervates a dorsal protractor muscle of the CPS and sends side branches to the aorta and the bolwig organ (BO) (stemmata). In its further course, this nerve merges with the prothoracic nerve (PN). The architecture of the PN is extremely complex. It innervates a set of accessory pharyngeal muscles attached to the CPS and the body wall musculature of the prothorax. Several anastomoses exist between side branches of this nerve which were shown to contain motor pathways. The mesothoracic nerve (MeN) innervates a MH accessor and the longitudinal and transversal body wall muscles of the second segment. J. Morphol. 271:969–979, 2010. © 2010 Wiley‐Liss, Inc.     

Interactions Between Limb Regeneration and Molting in Decapod Crustaceans

Molting and regeneration of lost appendages are tightly-coupled,hormonally-regulated processes in decapod crustaceans. Precociousmolts are induced by eyestalk ablation, which reduces circulatingmolt-inhibiting hormone (MIH) and results in an immediate risein hemolymph ecdysteroids. Precocious molts are also inducedby autotomy of 5–8 walking legs; adult land crabs (Gecarcinuslateralis) molt 6–8 wk after multiple leg autotomy (MLA).Autotomy of one or more of the 1° limb buds (LBs) that formafter MLA before a critical period interrupts proecdysis until2° LBs re-regenerate and grow to the approximate size ofthose lost. Based on these observations, Skinner proposed thatlimb buds produce two factors that control proecdysial events.Limb Autotomy Factor–Anecdysis (LAF_an), produced by 1°LBs when at least five legs are autotomized, stimulates anecdysialanimals to enter proecdysis. Limb Autotomy Factor–Proecdysis(LAF_pro), produced by 2° LBs in premolt animals when atleast one 1° LB is autotomized, inhibits proecdysial processes.Initial characterizations suggest that LAF_pro is a MIH-likepolypeptide that inhibits the synthesis and secretion of ecdysteroidby the Y-organs.     

Muscles and nerves of the posterior abdomen and genitalia of male Periplaneta americana (L.) (Dictyoptera : Blattidae)

Segmental and intersegmental muscles of abdominal segments 7–10 are described for adult, male Periplaneta americana (L.) (Dictyoptera : Blattidae). Locations of extrinsic and intrinsic genitalic muscles are documented, and the actions of those associated with the right phallomere are hypothesized. Muscles of the 5 abdominal segments are innervated by branches from 5 pairs of segmental nerves and 3 pairs of transverse nerves. These stem from a terminal synganglion, formed during embryogenesis by fusion of neuromeres of abdominal segments 7–11. One pair of segmental nerves issues from each of the 5 neuromeres, and one pair of transverse nerves arises from neuromeres of abdominal segments 7–9. The nerves are traced to the muscles, integument, and reproductive glands, and their peripheral unions are characterized. Serial homologies of the nerves and muscles are proposed, and comparisons are made with neuromusculature of the female.     

Regeneration of Walking Legs in the Fiddler Crab Uca pugilator

SYNOPSIS. Regeneration of walking legs in the fiddler crab Ucapugilator is most efficient when it follows autotomy (the reflexiveloss of a limb). Closure of the wound and would healing occurimmediately following autotomy and visible regeneration beginswithin a few days. Regeneration of the walking leg occurs intwo distinct stages: The first stage, called Basal Growth, involvesmitosis and differentiation. The second stage involves primarilyprotein synthesis and water uptake and is called ProecdysialGrowth. Proecdysial Growth is, in part, under direct hormonalstimulation.     

Terrapin muscle afferents studied by cord dorsum potential analyses

Rostro-caudal ramification of terrapin hindlimb afferent nerves have been studied by cord dorsum potential analyses. Stimulation of muscle and cutaneous nerves evoke different waveforms, related to the difference in fibre diameter spectra. Afferents of small muscles enter the cord through one spinal nerve, while afferents of large muscles are connected to the cord by up to four spinal roots. In their entrance segment muscle afferents bifurcate into branches extending in rostral and caudal direction over at least three segments.     

Plasticity in the cockroach neuromuscular system

The retrograde transport of wheat germ agglutinin-conjugated horseradish peroxidase extracellularly injected into a leg muscle was used to identify the regenerating cockroach motor neurons that have grown an axonal branch into that muscle. At least 66% of the animals with crushed nerve roots eventually reform the original innervation pattern of this muscle with no mistakes. In spite of this apparent specificity the cockroach neuromuscular system can express plasticity as evidenced by the correction of mistakes made at early stages of regeneration. These mistakes are corrected through elimination during the time interval between 40 and 60 days after nerve crush. In addition, when the distal segments of the leg are removed, thus depriving some motor neurons of their normal target muscles, many of them form stable inappropriate axonal branches in denervated as well as fully innervated muscles. These observations are discussed in terms of possible mechanisms responsible for the specificity of the cellular interactions and in terms of their relevance to understanding the development of vertebrate neuromuscular systems.     

Leave it all behind: a taxonomic perspective of autotomy in invertebrates

Autotomy is defined herein as the shedding of a body part, where (1) the loss of the body part is defensive (autotomy helps prevent the whole animal from being compromised and is in response to external stimuli); (2) shearing occurs by an intrinsic mechanism along a breakage plane (there has been selection for certain body parts to be pulled off easily); and (3) the loss is controlled - the animal moves away from the trapped limb, the loss is under some form of central control (neural or hormonal), or the body part is detached quickly. Autotomy (under this defensive definition) has evolved independently for a diverse array of body parts in many taxa; we have summarised available information for over 200 invertebrate species. The advantages of autotomy include escape from entrapment, an effective form of attack, expulsion of an infected body part or in limiting wounding. We discuss how the incidence of autotomy may therefore be correlated with various traits such as limb function, sex differences, other defence mechanisms, habitat disturbance, and sociality. There are also costs associated with autotomy. Short-term costs include loss of a specialised appendage or organ, reduced speed and stability, or even death. Long-term costs include compromised foraging and feeding (often leading to reduced growth), altered anti-predator, competitive or reproductive behaviour, and even defective development. Regenerating lost appendages may also incur significant costs for the individual. We examine the costs and benefits of autotomy, and discuss the evolutionary selective pressures that contribute to the prevalence and effectiveness of autotomy in invertebrates.     

Unique Structural Features Facilitate Lizard Tail Autotomy

Autotomy refers to the voluntary shedding of a body part; a renowned example is tail loss among lizards as a response to attempted predation. Although many aspects of lizard tail autotomy have been studied, the detailed morphology and mechanism remains unclear. In the present study, we showed that tail shedding by the Tokay gecko (Gekko gecko) and the associated extracellular matrix (ECM) rupture were independent of proteolysis. Instead, lizard caudal autotomy relied on biological adhesion facilitated by surface microstructures. Results based on bio-imaging techniques demonstrated that the tail of Gekko gecko was pre-severed at distinct sites and that its structural integrity depended on the adhesion between these segments.     

Investigations on the Incorporation of a Tritiated Ganglioside, GM1, in the Injured and Intact Sciatic Nerves of the Rat

Following injury of their left sciatic nerves by means of a standardized procedure, male rats received intravenous injections of a tritiated ganglioside. GM1, on different days during the process of regeneration. The rats were killed at two different times after the injection and the concentrations of the total radioactivity, nonvolatile radioactivity, and labelled GM1 were estimated in six segments of the crushed and intact sciatic nerves. The segments of the damaged nerves showed higher concentrations of radioactivity and a higher content of GM1 than the corresponding segments of the contralateral nerves. Within the immediate area of the lesion the highest levels were found on the 3rd and 6th days after the injury; the segments distal from the lesion showed the highest levels of activity on days 9 and 12. The nerve segments proximal to the site of the injury showed a low rate of radioactivity incorporation. The higher concentrations of [3H]GM1 in damaged nerves as well as the rate of incorporation as a function of time indicate that exogenous gangliosides may be involved in the processes of regeneration and have a bearing on the latter.     

The process of total tail autotomy in the South-American rodent, Proechimys

Tail autotomy in Proechimys cuvieri was studied both morphologically and histologically. The rupture always occurs at the base of the external tail, e.g. in the immediate vicinity of its junction with the body. It thus concerns the whole caudal appendage. The distal epiphysis is separated from the fifth caudal vertebra and lost with the rest of the tail. There is no single reason responsible for the constancy of this breaking point, but several morphological factors can act together: these include strong binding of the five first caudal vertebrae to the body, disappearance of the plurisegmental muscles beyond this level, and the great extent and loose structure of the epiphyseal plates. Autotomy is a biological event occurring throughout the life of the animals, but it is of a cumulative nature. Tail loss is much more prevalent in older and heavier animals than in juveniles. Overall, about 9% of wild populations show this loss. Owing to the increasing percentage of occurrence from young to old, tail autotomy seems to enhance the survival chances of its owner, although direct proof of any predation influence are still lacking.     

Thenar and hypothenar muscles and their innervation by the ulnar and median nerves in the human hand.

The thenar and hypothenar muscles as well as their supplying nerves were analyzed with an improved dissecting method. Among the four thenar muscles, the m. abductor pollicis brevis (AbPB) has a separate muscle belly, whereas the m. opponens pollicis (OP), the superficial and deep heads of the flexor pollicis brevis (sFPB and dFPB), and the adductor pollicis (AdP) are fused with each other to make a single mass (deep thenar muscle group). These muscles are innervated by branches of the recurrent nerve and the accessory recurrent nerve from the median nerve as well as by terminal branches of the deep branch (ramus profundus) of the ulnar nerve. These three nerves frequently form a loop within the deep thenar muscle group (thenar loop), and a branch to the OP and one to deep parts of the sFPB often make a smaller loop (intrathenar loop), whereas the AbPB receives a separate nerve branch. Among the hypothenar muscle, the m. abductor digiti minimi and the m. flexor digiti minimi brevis are fused with each other, and their supplying nerves frequently form a loop in these muscles (intrahypothenar loop), whereas the m. opponens digiti minimi is separated from the others and receives a separate nerve branch. In the distribution pattern of supplying nerves to the thenar and hypothenar muscles, we find regularities in that they branch off in a regular manner from the ulnar and the median nerve, and that nerve branches to those muscles with fused bellies frequently communicate with each other to make loops.     

AN ANATOMICAL STUDY OF THE ABDOMINAL NERVOUS AND MUSCULAR SYSTEMS OF DRAGONFLY (AESHNIDAE) NYMPHS

The musculature of the fourth to eighth abdominal segments is typically composed of twenty pairs of segmental muscles associated with the body wall. In the first to third and ninth and tenth segments certain modifications to the basic plan occur in association with the abdominal-thoracic junction, the respiratory apparatus and the anal appendages. In some segments there are also paired muscles associated with the alimentary canal. Two large transverse muscles are present in the abdomen. There are eight abdominal ganglia, the first seven of which each give rise to three pairs of lateral nerves, the eighth to five pairs. In addition there are ten median abdominal nerves. The innervation fields of the various nerves are described. The first three pairs of lateral nerves of the last ganglion are homologous with the lateral nerves of the other abdominal ganglia; the fourth pair innervates most of segment nine; and the fifth pair innervates the remainder of segment nine, segment ten and the anal appendages. Certain of the abdominal muscles are innervated by branches from two different nerve roots. In segments six and seven the anterior point of attachment of the longitudinal stretch receptors is normally different from that in the other abdominal segments. This is discussed in the light of the types of movement which involve the abdomen and it seems apparent that these receptors are affected not only by swimming and abdominal flexion, as are the other longitudinal stretch receptors, but also by respiratory movements. Two distinct types of epidermal sensilla are present on the abdomen, spines and hairs. The former are the more numerous on the body, the latter on the anal appendages.     

小地老虎雄性外生殖器的肌肉系统及神经分布

小地老虎Agrotis ypsilon Rott.雄性外生殖器由第8腹节的5对肌肉支持,它具有充分功能的抱器(clasper)和第9腹节的侧骨片,具有8对外生殖器特有的肌肉。具有一对由第9,10,11节原始腹部神经节的侧神经组成的成对的粗大神经干9+10+11,神经干的神经分支分布神经到外生殖器。     

The ecology and evolution of autotomy

Autotomy, the self‐induced loss of a body part, occurs throughout Animalia. A lizard dropping its tail to escape predation is an iconic example, however, autotomy occurs in a diversity of other organisms. Octopuses can release their arms, crabs can drop their claws, and bugs can amputate their legs. The diversity of organisms that can autotomize body parts has led to a wealth of research and several taxonomically focused reviews. These reviews have played a crucial role in advancing our understanding of autotomy within their respective groups. However, because of their taxonomic focus, these reviews are constrained in their ability to enhance our understanding of autotomy. Here, we aim to synthesize research on the ecology and evolution of autotomy throughout Animalia, building a unified framework on which future studies can expand. We found that the ability to drop an appendage has evolved multiple times throughout Animalia and that once autotomy has evolved, selection appears to act on the removable appendage to increase the efficacy and/or efficiency of autotomy. This could explain why some autotomizable body parts are so elaborate (e.g. brightly coloured). We also show that there are multiple benefits, and variable costs, associated with autotomy. Given this variation, we generate an economic theory of autotomy (modified from the economic theory of escape) which makes predictions about when an individual should resort to autotomy. Finally, we show that the loss of an autotomizable appendage can have numerous consequences on population and community dynamics. By taking this broad taxonomic approach, we identified patterns of autotomy that transcend specific lineages and highlight clear directions for future research.