Characterization of Drosophila Nidogen/entactin reveals roles in basement membrane stability, barrier function and nervous system patterning.

Basement membranes (BMs) are specialized layers of extracellular matrix (ECM) mainly composed of Laminin, type IV Collagen, Perlecan and Nidogen/entactin (NDG). Recent in vivo studies challenged the initially proposed role of NDG as a major ECM linker molecule by revealing dispensability for viability and BM formation. Here, we report the characterization of the single Ndg gene in Drosophila. Embryonic Ndg expression was primarily observed in mesodermal tissues and the chordotonal organs, whereas NDG protein localized to all BMs. Although loss of Laminin strongly affected BM localization of NDG, Ndg-null mutants exhibited no overt changes in the distribution of BM components. Although Drosophila Ndg mutants were viable, loss of NDG led to ultrastructural BM defects that compromised barrier function and stability in vivo Moreover, loss of NDG impaired larval crawling behavior and reduced responses to vibrational stimuli. Further morphological analysis revealed accompanying defects in the larval peripheral nervous system, especially in the chordotonal organs and the neuromuscular junction (NMJ). Taken together, our analysis suggests that NDG is not essential for BM assembly but mediates BM stability and ECM-dependent neural plasticity during Drosophila development.

Sensing of Substrate Vibrations in the Adult Cicada Okanagana rimosa (Hemiptera: Cicadidae).

Detection of substrate vibrations is an evolutionarily old sensory modality and is important for predator detection as well as for intraspecific communication. In insects, substrate vibrations are detected mainly by scolopidial (chordotonal) sense organs found at different sites in the legs. Among these sense organs, the tibial subgenual organ (SGO) is one of the most sensitive sensors. The neuroanatomy and physiology of vibratory sense organs of cicadas is not well known. Here, we investigated the leg nerve by neuronal tracing and summed nerve recordings. Tracing with Neurobiotin revealed that the cicada Okanagana rimosa (Say) (Hemiptera: Cicadidae) has a femoral chordotonal organ with about 20 sensory cells and a tibial SGO with two sensory cells. Recordings from the leg nerve show that the vibrational response is broadly tuned with a threshold of about 1 m/s2 and a minimum latency of about 6 ms. The vibratory sense of cicadas might be used in predator avoidance and intraspecific communication, although no tuning to the peak frequency of the calling song (9 kHz) could be found.

Independent suboesophageal neuronal innervation of the defense gland and longitudinal muscles in the stick insect (Peruphasma schultei) prothorax.

This study investigates the neuroanatomy of the defense gland and a related muscle in the stick insect Peruphasma schultei with axonal tracing and histological sections. The gland is innervated by three neurons through the Nervus anterior of the suboesophageal ganglion (SOG), the ipsilateral neuron (ILN), the contralateral neuron (CLN) and the prothoracic intersegmental neuron (PIN). The ILN has a large soma which is typical for motoneurons that cause fast contraction of large muscles and its dendrites are located in motor-sensory and sensory neuropile areas of the SOG. The CLN might be involved in the coordination of bilateral or unilateral discharge as its neurites are closely associated to the ILN of the contralateral gland. Close to the ejaculatory duct of the gland lies a dorsal longitudinal neck muscle, musculus pronoto-occipitalis (Idlm2), which is likely indirectly involved in gland discharge by controlling neck movements and, therefore, the direction of discharge. This muscle is innervated by three ventral median neurons (VMN). Thus, three neuron types (ILN, CLN, and PIN) innervate the gland muscle directly, and the VMNs could aid secretion indirectly. The cytoanatomy of motorneurons innervating the defense gland and neck muscle are discussed regarding the structure and functions of the neuropile in the SOG. As a basis for the neuroanatomical study on the defense gland we assembled a map of the SOG in Phasmatodea.

Vibrational sensitivity of the subgenual organ complex in female Sipyloidea sipylus stick insects in different experimental paradigms of stimulus direction, leg attachment, and ablation of a connective tibial sense organ.

We document the sensitivity to sinusoidal vibrations for chordotonal organs in the stick insect tibia (Sipyloidea sipylus). In the tibia, the scolopidial subgenual organ (~40 scolopidial sensilla), distal organ (~20 scolopidial sensilla), and distal tibial chordotonal organ (~7 scolopidial sensilla) are present. We study the sensitivity of tibial sensory organs in all leg pairs to vibration stimuli as sensory thresholds by recording summed action potentials from Nervus cruris in the femur. The tibia was stimulated with a minishaker delivering vibrational stimuli. Because different experimental procedures may affect the vibration sensitivity, we here analysed possible effects of different experimental conditions: (1) the stimulus direction delivered in either horizontal or vertical direction to the leg; (2) recording responses only from the subgenual organ complex after ablation of the distal tibial chordotonal organ, and (3) the attachment of the leg to the minishaker by plastilin, beeswax-colophony, or freely standing legs. The tibial scolopidial organs give summed responses to vibration stimuli with highest sensitivity between 500 and 1000Hz for all leg pairs. In the different experimental series, we find that (1) thresholds were influenced by stimulation direction with lower thresholds in response to vertical vibrations, (2) ablating the distal tibial chordotonal organ by cutting the distal-most tibia did not change the summed sensory thresholds significantly, and (3) the attachment material between legs and the minishaker (plastilin or beeswax-colophony mixture) did not significant influence the sensory thresholds against free-standing tarsi. The distal tibial chordotonal organ is a connective chordotonal organ attached to a tendon and is likely a proprioceptive organ. These results emphasise that vibrational thresholds are mainly direction-sensitive. Thus, the direction of stimulus delivery during electrophysiological recordings is relevant for comparisons of vibratory sensory thresholds.

Phonotactic flight of the parasitoid fly Emblemasoma auditrix (Diptera: Sarcophagidae).

The parasitoid fly Emblemasoma auditrix locates its hosts using acoustic cues from sound producing males of the cicada Okanagana rimosa. Here, we experimentally analysed the flight path of the phonotaxis from a landmark to the target, a hidden loudspeaker in the field. During flight, the fly showed only small lateral deviations. The vertical flight direction angles were initially negative (directed downwards relative to starting position), grew positive (directed upwards) in the second half of the flight, and finally flattened (directed horizontally or slightly upwards), typically resulting in a landing above the loudspeaker. This phonotactic flight pattern was largely independent from sound pressure level or target distance, but depended on the elevation of the sound source. The flight velocity was partially influenced by sound pressure level and distance, but also by elevation. The more elevated the target, the lower was the speed. The accuracy of flight increased with elevation of the target as well as the landing precision. The minimal vertical angle difference eliciting differences in behaviour was 10°. By changing the elevation of the acoustic target after take-off, we showed that the fly is able to orientate acoustically while flying.

The Auditory System of the Dipteran Parasitoid Emblemasoma auditrix (Sarcophagidae).

Several taxa of insects evolved a tympanate ear at different body positions, whereby the ear is composed of common parts: a scolopidial sense organ, a tracheal air space, and a tympanal membrane. Here, we analyzed the anatomy and physiology of the ear at the ventral prothorax of the sarcophagid fly, Emblemasoma auditrix (Soper). We used micro-computed tomography to analyze the ear and its tracheal air space in relation to the body morphology. Both tympana are separated by a small cuticular bridge, face in the same frontal direction, and are backed by a single tracheal enlargement. This enlargement is connected to the anterior spiracles at the dorsofrontal thorax and is continuous with the tracheal network in the thorax and in the abdomen. Analyses of responses of auditory afferents and interneurons show that the ear is broadly tuned, with a sensitivity peak at 5 kHz. Single-cell recordings of auditory interneurons indicate a frequency- and intensity-dependent tuning, whereby some neurons react best to 9 kHz, the peak frequency of the host's calling song. The results are compared to the convergently evolved ear in Tachinidae (Diptera).

How many mechanosensory organs in the bushcricket leg? Neuroanatomy of the scolopidial accessory organ in Tettigoniidae (Insecta: Orthoptera).

The subgenual organ and associated scolopidial organs are well studied in Orthoptera and related taxa. In some insects, a small accessory organ or Nebenorgan is described posterior to the subgenual organ. In Tettigoniidae (Ensifera), the accessory organ has only been noted in one species though tibial sensory organs are well studied for neuroanatomy and physiology. Here, we use axonal tracing to analyse the posterior subgenual organ innervated by the main motor nerve. Investigating seven species from different groups of Tettigoniidae, we describe a small group of scolopidial sensilla (5-9 sensory neurons) which has features characteristic of the accessory organ: posterior tibial position, innervation by the main leg nerve rather than by the tympanal nerve, orientation of dendrites in proximal or ventro-proximal direction in the leg, and commonly association with a single campaniform sensillum. The neuroanatomy is highly similar between leg pairs. We show differences in the innervation in two species of the genus Poecilimon as compared to the other species. In Poecilimon, the sensilla of the accessory organ are innervated by one nerve branch together with the subgenual organ. The results suggest that the accessory organ is part of the sensory bauplan in the leg of Tettigoniidae and probably Ensifera.

Position-dependent hearing in three species of bushcrickets (Tettigoniidae, Orthoptera).

A primary task of auditory systems is the localization of sound sources in space. Sound source localization in azimuth is usually based on temporal or intensity differences of sounds between the bilaterally arranged ears. In mammals, localization in elevation is possible by transfer functions at the ear, especially the pinnae. Although insects are able to locate sound sources, little attention is given to the mechanisms of acoustic orientation to elevated positions. Here we comparatively analyse the peripheral hearing thresholds of three species of bushcrickets in respect to sound source positions in space. The hearing thresholds across frequencies depend on the location of a sound source in the three-dimensional hearing space in front of the animal. Thresholds differ for different azimuthal positions and for different positions in elevation. This position-dependent frequency tuning is species specific. Largest differences in thresholds between positions are found in Ancylecha fenestrata. Correspondingly, A. fenestrata has a rather complex ear morphology including cuticular folds covering the anterior tympanal membrane. The position-dependent tuning might contribute to sound source localization in the habitats. Acoustic orientation might be a selective factor for the evolution of morphological structures at the bushcricket ear and, speculatively, even for frequency fractioning in the ear.

Neurons of self-defence: neuronal innervation of the exocrine defence glands in stick insects.

BACKGROUND: Stick insects (Phasmatodea) use repellent chemical substances (allomones) for defence which are released from so-called defence glands in the prothorax. These glands differ in size between species, and are under neuronal control from the CNS. The detailed neural innervation and possible differences between species are not studied so far. Using axonal tracing, the neuronal innervation is investigated comparing four species. The aim is to document the complexity of defence gland innervation in peripheral nerves and central motoneurons in stick insects. RESULTS: In the species studied here, the defence gland is innervated by the intersegmental nerve complex (ISN) which is formed by three nerves from the prothoracic (T1) and suboesophageal ganglion (SOG), as well as a distinct suboesophageal nerve (Nervus anterior of the suboesophageal ganglion). In Carausius morosus and Sipyloidea sipylus, axonal tracing confirmed an innervation of the defence glands by this N. anterior SOG as well as N. anterior T1 and N. posterior SOG from the intersegmental nerve complex. In Peruphasma schultei, which has rather large defence glands, only the innervation by the N. anterior SOG was documented by axonal tracing. In the central nervous system of all species, 3-4 neuron types are identified by axonal tracing which send axons in the N. anterior SOG likely innervating the defence gland as well as adjacent muscles. These neurons are mainly suboesophageal neurons with one intersegmental neuron located in the prothoracic ganglion. The neuron types are conserved in the species studied, but the combination of neuron types is not identical. In addition, the central nervous system in S. sipylus contains one suboesophageal and one prothoracic neuron type with axons in the intersegmental nerve complex contacting the defence gland. CONCLUSIONS: Axonal tracing shows a very complex innervation pattern of the defence glands of Phasmatodea which contains different neurons in different nerves from two adjacent body segments. The gland size correlates to the size of a neuron soma in the suboesophageal ganglion, which likely controls gland contraction. In P. schultei, the innervation pattern appears simplified to the anterior suboesophageal nerve. Hence, some evolutionary changes are notable in a conserved neuronal network.

Parasitoid flies exploiting acoustic communication of insects-comparative aspects of independent functional adaptations.

Two taxa of parasitoid Diptera have independently evolved tympanal hearing organs to locate sound producing host insects. Here we review and compare functional adaptations in both groups of parasitoids, Ormiini and Emblemasomatini. Tympanal organs in both groups originate from a common precursor organ and are somewhat similar in morphology and physiology. In terms of functional adaptations, the hearing thresholds are largely adapted to the frequency spectra of the calling song of the hosts. The large host ranges of some parasitoids indicate that their neuronal filter for the temporal patterns of the calling songs are broader than those found in intraspecific communication. For host localization the night active Ormia ochracea and the day active E. auditrix are able to locate a sound source precisely in space. For phonotaxis flight and walking phases are used, whereby O. ochracea approaches hosts during flight while E. auditrix employs intermediate landings and re-orientation, apparently separating azimuthal and vertical angles. The consequences of the parasitoid pressure are discussed for signal evolution and intraspecific communication of the host species. This natural selection pressure might have led to different avoidance strategies in the hosts: silent males in crickets, shorter signals in tettigoniids and fluctuating population abundances in cicadas.

Experimental infection of a periodical cicada (Magicicada cassinii) with a parasitoid (Emblemasoma auditrix) of a proto-periodical cicada (Okanagana rimosa).

BACKGROUND: The proto-periodical cicada Okanagana rimosa is subject to infection by the acoustically orientating parasitoid fly Emblemasoma auditrix. Furthermore, it is also the only known host of E. auditrix. Here we test the question, whether the highly adapted parasitoid can also infect other cicadas, like the periodical cicada (Magicicada cassinii) and which steps of the parasitization process can be completed. The experiments might also reveal whether such a parasitoid could hypothetically have been involved in the evolution of periodicity. RESULTS: The hearing threshold of E. auditrix matches with the spectrum of the calling song of M. cassinii, indicating potential host localization. Behaviourally, host localization is possible by the parasitoid as it approaches a loudspeaker broadcasting the buzz part of the calling song of M. cassinii. Magicicada cassinii is readily accepted as host and for host infection the parasitoid uses the same behavioural sequence as for its host O. rimosa. A larva is deposited into the timbal of the cicada. By contrast to O. rimosa the development of the fly larva is delayed and eventually suppressed in M. cassinii. CONCLUSIONS: The host range of E. auditrix is mainly determined by acoustic parameters. This filter is important, as other sensory cues seem not to be involved in the host selection process and larva will not develop in unsuited host. Although the recent parasitoid-host system seems to be stable in terms of coexistence of both species, an acoustically hunting parasitoid could have been a selective force during evolution of prime numbered periodicity in cicadas.

Acoustic defence in an insect: characteristics of defensive stridulation and differences between the sexes in the tettigoniid Poecilimon ornatus (Schmidt 1850).

Many insects exhibit secondary defence mechanisms upon contact with a predator, such as defensive sound production or regurgitation of gut contents. In the tettigoniid Poecilimon ornatus, both males and females are capable of sound production and of regurgitation. However, wing stridulatory structures for intraspecific acoustic communication evolved independently in males and females, and may result in different defence sounds. Here we investigate in P. ornatus whether secondary defence behaviours, in particular defence sounds, show sex-specific differences. The male defence sound differs significantly from the male calling song in that it has a longer syllable duration and a higher number of impulses per syllable. In females, the defence sound syllables are also significantly longer than the syllables of their response song to the male calling song. In addition, the acoustic disturbance stridulation differs notably between females and males as both sexes exhibit different temporal patterns of the defence sound. Furthermore, males use defence sounds more often than females. The higher proportion of male disturbance stridulation is consistent with a male-biased predation risk during calling and phonotactic behaviour. The temporal structures of the female and male defence sounds support a deimatic function of the startling sound in both females and males, rather than an adaptation for a particular temporal pattern. Independently of the clear differences in sound defence, no difference in regurgitation of gut content occurs between the sexes.

Differential inductions of phenylalanine ammonia-lyase and chalcone synthase during wounding, salicylic acid treatment, and salinity stress in safflower, Carthamus tinctorius.

Safflower (Carthamus tinctorius L.) serves as a reference dicot for investigation of defence mechanisms in Asteraceae due to abundant secondary metabolites and high resistance/tolerance to environmental stresses. In plants, phenylpropanoid and flavonoid pathways are considered as two central defence signalling cascades in stress conditions. Here, we describe the isolation of two major genes in these pathways, CtPAL (phenylalanine ammonia-lyase) and CtCHS (chalcone synthase) in safflower along with monitoring their expression profiles in different stress circumstances. The aa (amino acid) sequence of isolated region of CtPAL possesses the maximum identity up to 96% to its orthologue in Cynara scolymus, while that of CtCHS retains the highest identity to its orthologue in Callistephus chinensis up to 96%. Experiments for gene expression profiling of CtPAL and CtCHS were performed after the treatment of seedlings with 0.1 and 1 mM SA (salicylic acid), wounding and salinity stress. The results of semi-quantitative RT-PCR revealed that both CtPAL and CtCHS genes are further responsive to higher concentration of SA with dissimilar patterns. Regarding wounding stress, CtPAL gets slightly induced upon injury at 3 hat (hours after treatment) (hat), whereas CtCHS gets greatly induced at 3 hat and levels off gradually afterward. Upon salinity stress, CtPAL displays a similar expression pattern by getting slightly induced at 3 hat, but CtCHS exhibits a biphasic expression profile with two prominent peaks at 3 and 24 hat. These results substantiate the involvement of phenylpropanoid and particularly flavonoid pathways in safflower during wounding and especially salinity stress.

Useless hearing in male Emblemasoma auditrix (Diptera, Sarcophagidae)--a case of intralocus sexual conflict during evolution of a complex sense organ?

Sensory modalities typically are important for both sexes, although sex-specific functional adaptations may occur frequently. This is true for hearing as well. Consequently, distinct behavioural functions were identified for the different insect hearing systems. Here we describe a first case, where a trait of an evolutionary novelty and a highly specialized hearing organ is adaptive in only one sex. The main function of hearing of the parasitoid fly Emblemasoma auditrix is to locate the host, males of the cicada species Okanagana rimosa, by their calling song. This task is performed by female flies, which deposit larvae into the host. We show that male E. auditrix possess a hearing sense as well. The morphology of the tympanal organ of male E. auditrix is rather similar to the female ear, which is 8% broader than the male ear. In both sexes the physiological hearing threshold is tuned to 5 kHz. Behavioural tests show that males are able to orient towards the host calling song, although phonotaxis often is incomplete. However, despite extensive observations in the field and substantial knowledge of the biology of E. auditrix, no potentially adaptive function of the male auditory sense has been identified. This unique hearing system might represent an intralocus sexual conflict, as the complex sense organ and the behavioural relevant neuronal network is adaptive for only one sex. The correlated evolution of the sense organ in both sexes might impose substantial constraints on the sensory properties of the ear. Similar constraints, although hidden, might also apply to other sensory systems in which behavioural functions differ between sexes.

The subgenual organ complex in the cave cricket Troglophilus neglectus (Orthoptera: Rhaphidophoridae): comparative innervation and sensory evolution.

Comparative studies of the organization of nervous systems and sensory organs can reveal their evolution and specific adaptations. In the forelegs of some Ensifera (including crickets and tettigoniids), tympanal hearing organs are located in close proximity to the mechanosensitive subgenual organ (SGO). In the present study, the SGO complex in the non-hearing cave cricket Troglophilus neglectus (Rhaphidophoridae) is investigated for the neuronal innervation pattern and for organs homologous to the hearing organs in related taxa. We analyse the innervation pattern of the sensory organs (SGO and intermediate organ (IO)) and its variability between individuals. In T. neglectus, the IO consists of two major groups of closely associated sensilla with different positions. While the distal-most sensilla superficially resemble tettigoniid auditory sensilla in location and orientation, the sensory innervation does not show these two groups to be distinct organs. Though variability in the number of sensory nerve branches occurs, usually either organ is supplied by a single nerve branch. Hence, no sensory elements clearly homologous to the auditory organ are evident. In contrast to other non-hearing Ensifera, the cave cricket sensory structures are relatively simple, consistent with a plesiomorphic organization resembling sensory innervation in grasshoppers and stick insects.

Lesion-induced insights in the plasticity of the insect auditory system.

The auditory networks of Orthoptera offer a model system uniquely suited to the study of neuronal connectivity and lesion-dependent neural plasticity. Monaural animals, following the permanent removal of one ear in nymphs or adults, adjust their auditory pathways by collateral sprouting of afferents and deafferented interneurons which connect to neurons on the contralateral side. Transient lesion of the auditory nerve allows us to study regeneration as well as plasticity processes. After crushing the peripheral auditory nerve, the lesioned afferents regrow and re-establish new synaptic connections which are relevant for auditory behavior. During this process collateral sprouting occurs in the central nervous networks, too. Interestingly, after regeneration a changed neuronal network will be maintained. These paradigms are now been used to analyze molecular mechanism in neuronal plasticity on the level of single neurons and small networks.

Sensory neuroanatomy of stick insects highlights the evolutionary diversity of the orthopteroid subgenual organ complex.

The subgenual organ is a scolopidial sense organ located in the tibia of many insects. In this study the neuroanatomy of the subgenual organ complex of stick insects is clarified for two species, Carausius morosus and Siyploidea sipylus. Neuronal tracing shows a subgenual organ complex that consists of a subgenual organ and a distal organ. There are no differences in neuroanatomy between the three thoracic leg pairs, and the sensory structures are highly similar in both species. A comparison of the neuroanatomy with other orthopteroid insects highlights two features unique in Phasmatodea. The subgenual organ contains a set of densely arranged sensory neurons in the anterior-ventral part of the organ, and a distal organ with 16-17 scolopidial sensilla in C. morosus and 20-22 scolopidial sensilla in S. sipylus. The somata of sensory neurons in the distal organ are organized in a linear array extending distally into the tibia, with only a few exceptions of closely associated neurons. The stick insect sense organs show a case of an elaborate scolopidial sense organ that evolved in addition to the subgenual organ. The neuroanatomy of stick insects is compared to that studied in other orthopteroid taxa (cockroaches, locusts, crickets, tettigoniids). The comparison of sensory structures indicates that elaborate scolopidial organs have evolved repeatedly among orthopteroids. The distal organ in stick insects has the highest number of sensory neurons known for distal organs so far.

Spatial organization of tettigoniid auditory receptors: insights from neuronal tracing.

The auditory sense organ of Tettigoniidae (Insecta, Orthoptera) is located in the foreleg tibia and consists of scolopidial sensilla which form a row termed crista acustica. The crista acustica is associated with the tympana and the auditory trachea. This ear is a highly ordered, tonotopic sensory system. As the neuroanatomy of the crista acustica has been documented for several species, the most distal somata and dendrites of receptor neurons have occasionally been described as forming an alternating or double row. We investigate the spatial arrangement of receptor cell bodies and dendrites by retrograde tracing with cobalt chloride solution. In six tettigoniid species studied, distal receptor neurons are consistently arranged in double-rows of somata rather than a linear sequence. This arrangement of neurons is shown to affect 30-50% of the overall auditory receptors. No strict correlation of somata positions between the anterio-posterior and dorso-ventral axis was evident within the distal crista acustica. Dendrites of distal receptors occasionally also occur in a double row or are even massed without clear order. Thus, a substantial part of auditory receptors can deviate from a strictly straight organization into a more complex morphology. The linear organization of dendrites is not a morphological criterion that allows hearing organs to be distinguished from nonhearing sense organs serially homologous to ears in all species. Both the crowded arrangement of receptor somata and dendrites may result from functional constraints relating to frequency discrimination, or from developmental constraints of auditory morphogenesis in postembryonic development.

Temporal patterns of intra- and interspecific acoustic signals differ in two closely related species of Acanthoplus (Orthoptera: Tettigoniidae: Hetrodinae).

Males of the closely related African tettigoniids Acanthoplus discoidales and Acanthoplus longipes produce a long-lasting calling song and a short disturbance sound. The temporal patterns of the sounds were analysed in respect to species differences and song type differences. The calling songs of both species consist of impulses which are separated into verses of two syllables, with fewer impulses in the first syllable. A. longipes produces more impulses in each syllable than A. discoidales and has longer verse durations, verse intervals and syllable intervals. Also, the disturbance sounds, produced after mechanical stimulation, contain distinct verses of impulses. The disturbance sound of A. longipes has a higher number of impulses per verse than that of A. discoidales. The frequency spectra of the songs in both species have similar peak frequencies (around 12.5 kHz) and both species have their greatest hearing sensitivity in the range between 5 and 10 kHz. Females of A. longipes perform phonotaxis only to songs with a species-specific temporal pattern. By contrast, females of A. discoidales react positively to calling songs of both species.

Morphological and physiological regeneration in the auditory system of adult Mecopoda elongata (Orthoptera: Tettigoniidae).

Orthopterans are suitable model organisms for investigations of regeneration mechanisms in the auditory system. Regeneration has been described in the auditory systems of locusts (Caelifera) and of crickets (Ensifera). In this study, we comparatively investigate the neural regeneration in the auditory system in the bush cricket Mecopoda elongata. A crushing of the tympanal nerve in the foreleg of M. elongata results in a loss of auditory information transfer. Physiological recordings of the tympanal nerve suggest outgrowing fibers 5 days after crushing. An anatomical regeneration of the fibers within the central nervous system starts 10 days after crushing. The neuronal projection reaches the target area at day 20. Threshold values to low frequency airborne sound remain high after crushing, indicating a lower regeneration capability of this group of fibers. However, within the central target area the low frequency areas are also innervated. Recordings of auditory interneurons show that the regenerating fibers form new functional connections starting at day 20 after crushing.