Direct Muscles Research Articles

Удосконалена мініінвазивна ретромускулярна алопластика в пацієнтів із діастазом прямих м’язів живота

Diastasis recti abdominis contributes to the occurrence of defects with the formation of hernias of the white line. The recurrence of diastasis after alloplasty may also be associated with the presence of thinned posterior aponeurotic walls of the rectus abdominis muscles. Aim - to іncrease the effectiveness of surgical treatment of diastasis recti abdominis by using minimally invasive retromuscular techniques. Materials and methods. An analysis of surgical treatment of patients with diastasis recti abdominis was conducted in 126 patients. Average age - 51±1.2 years old. Diastasis width from 3 to 10 cm. In the I (main) group (n=64) surgical treatment it was performed according to the mini-invasive method we improved retromuscular technique. In the II group (comparison) (n=62) surgical treatment was performed according to the traditional «onlay» technique. In the postoperative period in patients of the I and II groups evaluated term stay of a patient in a hospital, direct and remote results. The methods of variational statistics were used: the averages for each studied feature, the errors of the arithmetic mean. Results. Term stay in a hospital patients of the I group was 2.1 days, the II group - 6.2 days. Among complications and on the side of the surgical wound in patients of the I group, a hematoma was observed in 2 (3.1%), seroma - in 4 (6.2%), wound infection was not observed, while in patients of the II group a hematoma was observed in 6 (9.7%), seroma - in 10 (16.1%), wound infection - in 3 (4.8%). Distant the results in terms of 2 to 36 months showed that among 35 patients of the II group, chronic postoperative pain was relapses were diagnosed in 2 (3.1%). diastasis direct muscles occurred in 7 (11.3%), and among 34 patients of the I group chronic postoperative pain diagnosed in 6 (9.7%) and relapse only in 1 (1.5%). Conclusions. Advanced mini-invasive retromuscular alloplasty is more effective, which is confirmed by a decrease in hospital stay and a decrease in postoperative complications. The research was carried out in accordance with the principles of the Declaration of Helsinki. The research protocol was approved by the Local Ethics Committee of the specified institution. Informed consent of the patients was obtained for the research. The authors declare no conflict of interest.

Physiotherapy in a patient with diastasis of the rectus abdominis muscle after childbirth.

Examination for the presence of diastasis of the rectus abdominis muscle and examination of the entire posture is very important in postpartum women. Currently, examination by 2D ultrasound, caliper and palpation is used. It is examined at rest and during stress tests. Case study of a patient with diastasis of the direct abdominal muscle after a first spontaneous uncomplicated delivery at the age of 32 years. Examination to confirm diastasis of the rectus abdominis muscle - the width of linea alba was measured with a 2D linear probe by ultrasound 4.5 cm above the umbilicus, in the region of the umbilicus and 4.5 cm below the umbilicus. Lying on the back at rest, and with elevation of the lower limbs. The degree of severity was classified into four grades. A standard physiotherapy postural examination was performed. A part of the intervention was individual exercise with activation of the m. transversus abdominis to reduce diastasis of the direct abdominal muscles. The exercise program included postural adjustment, modification of breathing stereotype and quality, and activation of pelvic floor muscles. Exercises to reduce pain in the ligamentous apparatus and training in correct ergonomics were also performed. The dosage of exercise was 15 min per day in the 1st week of treatment, 2-4 week of treatment 20 min per day, 5-12 week of treatment 30 min per day, 5 days per week, for 12 weeks. The effect of exercise with activation of m. transversus abdominis on the reduction of diastasis of the direct abdominal muscle in the postpartum patient was objectively proven by the above mentioned objectification methods.

The thoracic anatomy of Pselaphus heisei (Pselaphinae, Staphylinidae, Coleoptera).

We document external and internal thoracic structures of the free-living pselaphine beetle Pselaphus heisei (Pselaphitae) using a set of traditional and modern techniques. Like in the specialized myrmecophile Claviger testaceus (Clavigeritae), the skeletal elements of the pro- and pterothorax are highly compact, with largely reduced inter- and intrasegmental sutures. Features previously listed as synapomorphies of staphylinid subgroups, to which Pselaphinae belong, are confirmed for P. heisei. The only previously proposed thoracic synapomorphy of Pselaphinae, the mesoventral foveae, is likely transformed in P. heisei: we assume that the concavities are directed mesad and internally fused, thus forming a broad channel ("perforation") extending through the keel-like median region of the mesoventrite. The prothoracic foveal system is strongly reduced, with only one pair of pits present in front of the procoxae. Their internal invaginations form a transverse ventral endoskeletal bar that stabilizes the prothorax. The condition observed in the free-living P. heisei is in contrast with previous hypotheses linking the reduction of the foveal system with myrmecophily. Moreover, traces of the mesoventral foveae are even preserved in the highly specialized inquiline C. testaceus. Gland cells are associated with areas of hyaline squamose setae on different body regions, suggesting release of secretions on the ventral side of the head, pro- and mesothorax, and abdominal base. Similar specialized setal patches are common in Pselaphini and related groups within Pselaphitae. The prothoracic musculature in P. heisei is more complex than that in the myrmecophilous C. testaceus and the free-living, unspecialized Creophilus maxillosus (Staphylininae). The metathoracic muscle system is strongly simplified, demonstrating that P. heisei cannot fly, even though wings, some skeletal elements of the flight apparatus, and some small direct flight muscles are preserved. It cannot be fully excluded that indirect flight muscles and thus a functional flight apparatus is preserved in a certain percentage of individuals.

Flight muscle structure and flight capacity of females of the long‐distance migratory armyworm,Spodoptera frugiperda: effect of aging and reproduction, and trade‐offs between flight and fecundity

AbstractInsects in flight achieve the highest metabolism rates and wing beat frequency known in the animal kingdom, but how they do this is not fully understood. Here, we demonstrate the structure and arrangement of flight muscles in the thorax ofSpodoptera frugiperdaSmith & Abbot (Lepidoptera: Noctuidae). Dorsoventral direct flight muscles are stronger and more complicated than dorsoventral indirect flight muscles, which may be important for the moth to swiftly control the trajectory. The abundance of giant mitochondria and the extensive tracheolar system in flight muscle are two prominent features that are well adapted to the special requirements of flight. Parameters of flight muscle and flight capacity were lower in young females, and then increased with time and peaked in middle‐aged females. Mating accelerated the deterioration of the structure and function of flight muscles. Virgin females showed lower ovarian development rate but higher flight capacity than mated females. Further analysis found that female flight capacity was significantly negatively correlated to her fecundity, suggesting a trade‐off between flight and reproduction. The resource allocation to flight and egg production may be the result of a balance between the intensity of natural and sexual selection on both traits.

Minute workers and large soldiers in the subterranean ant Carebara perpusilla: Musculoskeletal consequences of Haller's rule in the thorax

Many organismal traits vary with body size, often reflecting trade-offs in the face of size-dependent constraints. For example, Haller's rule, the allometric pattern whereby smaller organisms have proportionally larger brains, can have carry-on effects on head design as the brain competes for space with other structures. Ant species with polymorphic worker castes are interesting cases for helping us understand these allometric effects. Here, we examine the effects of miniaturization on the ant power core, the mesosoma (thorax), with particular attention to how the scaling of nervous system structures affects the skeletomuscular elements involved with load bearing and locomotion. Using X-ray computed microtomography (microCT), we studied the thorax of Carebara perpusilla, an African ant species that has minute workers (1.5 mm-long) and larger soldiers (3.0 mm-long), allowing strong intraspecific comparisons. We find that the thoracic nervous system is relatively larger in minute workers, similar to Haller's rule, with consequences on the skeletomuscular organisation. Minute workers have relatively smaller petiole muscles and indirect head muscles, but relatively larger external trochanter muscles and direct head muscles. We link these allometric trade-offs to miniaturization and division of labor, and discuss how thorax design underlies the success of minute ants.

CURRENT PRINCIPLES OF TREATING ABDOMINAL COMPLICATIONS

Abdominal plastic is one of the most common operations in the field of plastic surgery. The main goal of abdominal plastic is to improve the body contours in the area of the anterior abdominal wall, by excising excessive skin and fat tissues, suturing diastasis of the direct abdominal muscles. Although abdominal plastic is considered a safe surgery with a high level of positive outcomes, there are still various kinds of complications, the treatment of which requires the use of modern methods. The work is based on the analysis of literature data on abdominal plastic and analysis of the postoperative period of 172 patients operated on in plastic surgery clinics in Krasnoyarsk from 2017 to 2020. Statistical data on abdominal plastic prevalence among aesthetic procedures were analyzed. Based on the identified data, it is shown that various types of abdominal plastic are quite in demand, which dictates the need to study possible complications after surgery, and modern methods of treating complications. The article analyzes common types of complica­tions after abdominal plastics and describes the algorithms for treating these complications. A comparative analysis of the incidence of complications in plastic surgery clinics in Krasnoyarsk was carried out with data from European plastic surgery clinics. Complications after abdominal plastic vary in severity and in the effect they have on aesthetic outcomes. Most complications can be treated in an outpatient setting, following modern standards, with satisfactory results.

AUTHOR’S MODIFICATION OF DIASTASIS SUTURING AND NEOPUS FORMATION

The aim of the study is to reduce the incidence of pup necrosis after suturing diastasis of the direct abdominal muscles.
 Materials and methods. The study included 34 patients. Abdominal volumes and diastasis levels were assessed. The presence of diastasis of the direct abdominal muscles was confirmed physically and by additional instrumental research methods: data from ultrasound examination of the anterior abdominal wall and electromyography of the direct abdominal muscles. Patients were divided into 2 groups depending on the type of diastasis suturing: 1 the group of diastasis of the right abdominal muscles was sutured in the traditional way, the study included women operated on in 2013–2016, in women 2 the group sutured diastasis of the right abdominal muscles by the author’s method (patent of the Russian Federation 2749475 from 11.06.21). Patients of group 2 were operated on from 2017 to 2022.
 Results. In comparison groups, the method of suturing diastasis was approached differently. In the postoperative period, there were significantly different complications. In the distant period, there was no relapse in the groups. Improvement in the functional state of the anterior abdominal wall also occurs noted patients after surgery. A year after the intervention, patients according to the survey: indicate a significantly smaller chronic pain syndrome in the umbilical ring and white line in both comparison groups and an improvement in cosmetic satisfaction of patients increased significantly, but in the second group it was slightly higher.
 Conclusion. Application of author’s modification in diastasis suturing and formation of neopoup reduces frequency of navel necrosis and improves cosmetic appearance of the latter.

Functional state of abdominal muscles in operative treatment of abdominal wall defects

The article presents the results of skin electromyography for 90 patients with umbilical hernias in combination with direct muscle diastasis, an assessment of the functional state of abdominal muscles before and after surgical treatment was carried out. The subjects were divided into two groups depending on the method of hernioplasty. The first group included 47 women (52,2%) the second group – 43 (47,7%) patients, each group was divided into a subgroup taking into account the size of the hernial defect and the stage of diastasis. In the formed groups, the functional state of the straight and lateral muscles was determined by recording amplitude and frequency during conditional contraction of the anterior abdominal wall. The study showed that the frequency of muscle contractions and the amplitude of fluctuations after surgical treatment in subgroups 1.1. and 1.2 was higher than subgroups 2.1. and 2.2 with respect to both the direct and lateral abdominal muscles. It was established that patients with umbilical hernias in combination with diastasis of the straight abdominal muscles need to perform combined hernioplasty in order to improve functional muscle activity and eliminate the imbalance between the straight and lateral muscles.

A Cyborg Insect Reveals a Function of a Muscle in Free Flight

While engineers put lots of effort, resources, and time in building insect scale micro aerial vehicles (MAVs) that fly like insects, insects themselves are the real masters of flight. What if we would use living insect as platform for MAV instead? Here, we reported a flight control via electrical stimulation of a flight muscle of an insect-computer hybrid robot, which is the interface of a mountable wireless backpack controller and a living beetle. The beetle uses indirect flight muscles to drive wing flapping and three major direct flight muscles (basalar, subalar, and third axilliary (3Ax) muscles) to control the kinematics of the wings for flight maneuver. While turning control was already achieved by stimulating basalar and 3Ax muscles, electrical stimulation of subalar muscles resulted in braking and elevation control in flight. We also demonstrated around 20 degrees of contralateral yaw and roll by stimulating individual subalar muscle. Stimulating both subalar muscles lead to an increase of 20 degrees in pitch and decelerate the flight by 1.5 m/s2 as well as an induce in elevation of 2 m/s2.

Age-Related Changes of Gene Expression Profiles in Drosophila

An individual’s gene expression profile changes throughout their life. This change in gene expression is shaped by differences in physiological needs and functions between the younger and older organism. Despite intensive studies, the aging process is not fully understood, and several genes involved in this process may remain to be identified. Here we report a transcriptomic analysis of Drosophila melanogaster using microarrays. We compared the expression profiles of two-day-old female adult flies with those of 45-day-old flies. We identified 1184 genes with pronounced differences in expression level between young and old age groups. Most genes involved in muscle development/maintenance that display different levels of expression with age were downregulated in older flies. Many of these genes contributed to sarcomere formation and function. Several of these genes were functionally related to direct and indirect flight muscles; some of them were exclusively expressed in these muscles. Conversely, several genes involved in apoptosis processes were upregulated in aging flies. In addition, several genes involved in resistance to toxic chemicals were upregulated in aging flies, which is consistent with a global upregulation of the defense response system in aging flies. Finally, we randomly selected 12 genes among 232 genes with unknown function and generated transgenic flies expressing recombinant proteins fused with GFP protein to determine their subcellular expression. We also found that the knockdown of some of those 12 genes can affect the lifespan of flies.

Hydrophilic and opened canals in honey bee tongue rods endow elastic structures with multiple functions

The honey bee (Apis mellifera L.) tongue is a sophisticated and dexterous probing device that can bend and twist, adapting to various surfaces for liquid imbibition and/or gustatory sensing. The tongue exhibits remarkable extendibility, flexibility, and durability, which may be essentially ascribed to the internal elastic rod that supports the entire tongue. However, neither the material composition nor the structural features of the rod, especially a peculiar inner canal that facilitates feeding, have been studied in relation to their function. Herein, by combining a set of imaging techniques, including optical microscopy, high-speed videography, scanning electron microscopy, micro-computed tomography (micro-CT), and confocal laser scanning microscopy, we characterize the spatial morphology, surface wettability and material composition of honey bee tongue rods. By performing mechanical testing, including atomic force microscopy, fracture testing, and finite element analysis, we provide the first evidence that the internal canal of the rod may represent a specialized structure for water retention due to the specific chemistry of resilin, which is an elastomeric protein that dominates the entire rod and renders it highly elastic, compliant and robust. Numerical simulations also suggest that the opening of the canal may facilitate larger deformations in twisting, extending the flexibility of the rod. Statement of significanceThe honey bee is one of the most important pollinators around the world and is capable of foraging a wide spectrum of liquid sources by dipping into them with a miniature hairy tongue. However, there are no direct muscles distributed inside the tongue, instead, there is a conspicuous elastic rod with a hollow core. The rod extends for its full length and, according to our study, structurally reinforces the entire tongue to achieve functional versatility, and suggests a water containing function of the rod canal for maintaining the elasticity of the protein (resilin) that constitutes the rod. Our results broaden understandings of the relationship among morphology, materials science, and function of a honey bee tongue.

Single-cell transcriptomics of the Drosophila wing disc reveals instructive epithelium-to-myoblast interactions.

In both vertebrates and invertebrates, generating a functional appendage requires interactions between ectoderm-derived epithelia and mesoderm-derived cells. To investigate such interactions, we used single-cell transcriptomics to generate a temporal cell atlas of the Drosophila wing disc from two developmental time points. Using these data, we visualized gene expression using a multilayered model of the wing disc and cataloged ligand-receptor pairs that could mediate signaling between epithelial cells and adult muscle precursors (AMPs). We found that localized expression of the fibroblast growth factor ligands, Thisbe and Pyramus, in the disc epithelium regulates the number and location of the AMPs. In addition, Hedgehog ligand from the epithelium activates a specific transcriptional program within adjacent AMP cells, defined by AMP-specific targets Neurotactin and midline, that is critical for proper formation of direct flight muscles. More generally, our annotated temporal cell atlas provides an organ-wide view of potential cell-cell interactions between epithelial and myogenic cells.

The specialized thoracic skeletomuscular system of the myrmecophile Claviger testaceus (Pselaphinae, Staphylinidae, Coleoptera)

External and internal structures of the thorax of the myrmecophile beetle Claviger testaceus (Clavigeritae, Pselaphinae) were examined and documented with state-of-the-art visualization techniques. Following a general trend in the omaliine lineage (Staphylinidae), the skeletal elements of the pro- and pterothorax in Claviger reach a maximum degree of compactness, with largely reduced inter- and intrasegmental sutures and skeletal elements linked with the flight apparatus. The musculature, especially metathoracic direct and indirect flight muscles, also shows a high degree of reduction. Two forms of wings were found among individuals of C. testaceus, both non-functional and representing an advanced stage of reduction. However, that wing vestiges are still present and the metanotum, only slightly reduced, suggests that loss of flight in this species is likely the result of a young evolutionary process. Several structures are linked with myrmecophilous habits: small body size facilitates transportation of beetles by ant workers and makes it easier to move inside nest tunnels; the remarkably compact body and mechanically robust appendages make the beetles less vulnerable to attacks by ant mandibles; the improved elytral interlocking mechanism and unusually expanded epipleura enhance the protection of vulnerable dorsal parts of the pterothorax and anterior abdomen; and glands associated with trichomes on the posterolateral elytral angle produce secretions attractive for ants. Various modifications of the thorax and anterior abdomen lead to an optimization of intimate associations with ants. The morphological syndrome enabling these beetles to cope with life in ant colonies evolved in several steps. This is suggested by an increasing solidification of the thoracic skeleton in related non-myrmecophilous groups and also by less modified related clavigerites;for instance, ant-associated tropical species are still able to fly.

Дифференциальный подход к ушиванию диастаза прямых мышц передней брюшной стенки

Aim of study. To reduce the rate of recurrence after diastasis suturing. Material and methods. The study included 86 female patients. Abdominal volumes and diastasis levels were assessed. The presence of diastasis of rectus abdominis was confirmed (physically and by additional instrumental research methods: ultrasound of the anterior abdominal wall and electromyography of the direct abdominal muscles). All patients were divided into 4 groups based on the level of diastasis. In group 1, aponeurosis was normal, diastasis of the direct abdominal muscles was not observed. In group 2, diastasis of the direct abdominal muscles was observed in the epigastric region (from the xiphoid process to the navel, diastasis suturing was performed in the defect region). In group 3, diastasis of the direct abdominal muscles was observed in the hypogastrium (from the umbilicus to the womb, suturing of the diastasis was performed in the defect region). In group 4, diastasis was observed in straight abdominal muscles along the entire white abdominal line (from the umbilicus to the womb, diastasis suturing was performed in the defect area). Results. The surgery utilised a differential approach to diastasis suturing depending on the level of diastasis. In the long term, there was no relapse in the relapse groups. Improvement in the functional state of the anterior abdominal wall was also noted by the patients after surgery. A year after the intervention, patients underwent a survey and indicated a significantly smaller chronic pain syndrome in the umbilical ring and white line as well as significant improvement of cosmetic satisfaction. Conclusion. Application of differential approach and additional instrumental examination in the preoperative period (ultrasound examination of the anterior abdominal wall and electromyography of direct abdominal muscles) reduces the frequency of postoperative relapse of diastasis

A cell atlas of adult muscle precursors uncovers early events in fibre-type divergence in Drosophila.

In Drosophila, the wing disc‐associated muscle precursor cells give rise to the fibrillar indirect flight muscles (IFM) and the tubular direct flight muscles (DFM). To understand early transcriptional events underlying this muscle diversification, we performed single‐cell RNA‐sequencing experiments and built a cell atlas of myoblasts associated with third instar larval wing disc. Our analysis identified distinct transcriptional signatures for IFM and DFM myoblasts that underlie the molecular basis of their divergence. The atlas further revealed various states of differentiation of myoblasts, thus illustrating previously unappreciated spatial and temporal heterogeneity among them. We identified and validated novel markers for both IFM and DFM myoblasts at various states of differentiation by immunofluorescence and genetic cell‐tracing experiments. Finally, we performed a systematic genetic screen using a panel of markers from the reference cell atlas as an entry point and found a novel gene, Amalgam which is functionally important in muscle development. Our work provides a framework for leveraging scRNA‐seq for gene discovery and details a strategy that can be applied to other scRNA‐seq datasets.

EFFECT OF CONNECTIVE INSUFFICIENCY AND SIZES OF MEDIAN HERNIAS ON BEFORE AND POSTOPERATIVE FUNCTION OF THE ABDOMINAL MUSCLE

The article analyzes the results of electromyography of the abdominal muscles in 189 patients with median postoperative hernia of the anterior abdominal wall of different sizes before and after the combined methods of hernioplasty, including considering the level of connective tissue failure. In the preoperative period, electromyography was performed in 69 (36,6%), after combined hernioplasty, 120 (63,4%) patients. The patients were divided into a group of 161 (85,1%) patients with clinically significant or histologically confirmed connective tissue insufficiency and into a group of 28 (14,9%) patients without it. The distribution of patients in the examination groups was carried out using an original method of assessing the degree of deviation of collagen fibers from the projection of the Langer lines in microscopic specimens of the skin areas excised during the operation and based on the results of a retrospective analysis of case histories with determination of the intraoperative adhesions of the adhesions in the abdominal cavity or hernial sac. In the formed groups, we studied the amplitude, frequency, front and area of electromyograms obtained from the direct and lateral muscles of the anterior abdominal wall. It was found that in patients with median postoperative hernias, mesenchymal dysplasia was the main reason for the decrease in functional activity and the imbalance of forces between the direct and lateral abdominal muscles. Optimal restoration of electroactivity of the abdominal muscles after combined hernioplasty occurred among patients without clinically significant connective tissue insufficiency. When reaching a giant postoperative hernia of gigantic size in patients with a clinically significant level of connective tissue dysplasia, the functioning of the abdominal muscles decreased by 26%, and in patients without it only by 15%. The pathology of collagen in skin grafts excised during surgery was detected in 91,5% of patients with mid-incisional hernias.

Embryological evidence substantiates the subcoxal theory on the origin of pleuron in insects

The lateral body plate pleuron is a significant structure in insects that contributes to the development and elaboration of wings and limbs (appendages). Although the pleuron is thought to originate from the proximal-most appendicular segment, the subcoxa, details remain unclear, and the morphological boundary between the dorsal body plate tergum and appendage (BTA) has not been clearly specified. Employing low-vacuum scanning electron microscopy (SEM) and the nano-suit method for SEM, we followed, in detail, the development of the thoracic segments of the two-spotted cricket Gryllus bimaculatus and succeeded in clearly defining the BTA. This study demonstrates the subcoxal origin of the pleuron, suggests the tergal origin of spiracles, and reveals that the wing proper originates exclusively from the tergum, whereas the wing hinge and direct muscles may be appendicular in origin, suggesting the dual origin (i.e., tergal plus appendicular origin) of wings.

Using the aponeurotic hypotensive suture in surgical treatment of patients with median postoperative ventral hernias

One of the operation about the median postoperative ventral hernia is retromuscular plastic Stoppa-Rives. For large defects closure rear sheets of the sheaths of direct muscles associated with the eruption of the seams. The authors propose a new hypotensive aponeurotic suture located opposite each other of the chains of stitches oriented in the transverse direction. This seam is used in 14 patients. All patients were able to take in rear sheets of the sheaths of direct muscles under the control of intra-abdominal pressure. During the early postoperative period without complications. Patients viewed through 6-20 months. Recurrence was not detected. It is concluded that the use of this seam is safe and effective closure of the fascia when alloplasty.

Comparative thoracic anatomy of the wild type and wingless (wg1cn1) mutant of Drosophila melanogaster (Diptera)

Genetically modified organisms are crucial for our understanding of gene regulatory networks, physiological processes and ontogeny. With modern molecular genetic techniques allowing the rapid generation of different Drosophila melanogaster mutants, efficient in-depth morphological investigations become an important issue. Anatomical studies can elucidate the role of certain genes in developmental processes and point out which parts of gene regulatory networks are involved in evolutionary changes of morphological structures. The wingless mutation wg1 of D. melanogaster was discovered more than 40 years ago. While early studies addressed the external phenotype of these mutants, the documentation of the internal organization was largely restricted to the prominent indirect flight muscles. We used SEM micrographs, histological serial sections, μ-computed tomography, CLSM and 3D reconstructions to study and document the thoracic skeletomuscular system of the wild type and mutant. A recently introduced nomenclature for the musculature of neopteran insects was applied to facilitate comparisons with closely or more distantly related taxa. The mutation is phenotypically mainly characterized by the absence of one or both wings and halteres. The wing is partly or entirely replaced by duplications of mesonotal structures, whereas the haltere and its associated muscles are completely absent on body sides showing the reduction. Both the direct and indirect mesothoracic flight muscles are affected by loss and reorientation of bundles or fibers. Our observations lead to the conclusion that the wingless mutation causes a homeotic transformation in the imaginal discs of wings and halteres with a direct effect on the development of skeletal structures and an indirect effect on the associated muscular system.

The thorax of the cave cricket Troglophilus neglectus: anatomical adaptations in an ancient wingless insect lineage (Orthoptera: Rhaphidophoridae).

BackgroundSecondary winglessness is a common phenomenon found among neopteran insects. With an estimated age of at least 140 million years, the cave crickets (Rhaphidophoridae) form the oldest exclusively wingless lineage within the long-horned grasshoppers (Ensifera). With respect to their morphology, cave crickets are generally considered to represent a `primitive’ group of Ensifera, for which no apomorphic character has been reported so far.ResultsWe present the first detailed investigation and description of the thoracic skeletal and muscular anatomy of the East Mediterranean cave cricket Troglophilus neglectus (Ensifera: Rhaphidophoridae). T. neglectus possesses sternopleural muscles that are not yet reported from other neopteran insects. Cave crickets in general exhibit some unique features with respect to their thoracic skeletal anatomy: an externally reduced prospinasternum, a narrow median sclerite situated between the meso- and metathorax, a star-shaped prospina, and a triramous metafurca. The thoracic muscle equipment of T. neglectus compared to that of the bush cricket Conocephalus maculatus (Ensifera: Tettigoniidae) and the house cricket Acheta domesticus (Ensifera: Gryllidae) reveals a number of potentially synapomorphic characters between these lineages.ConclusionsBased on the observed morphology we favor a closer relationship of Rhaphidophoridae to Tettigoniidae rather than to Gryllidae. In addition, the comparison of the thoracic morphology of T. neglectus to that of other wingless Polyneoptera allows reliable conclusions about anatomical adaptations correlated with secondary winglessness. The anatomy in apterous Ensifera, viz. the reduction of discrete direct and indirect flight muscles as well as the strengthening of specific leg muscles, largely resembles the condition found in wingless stick insects (Euphasmatodea), but is strikingly different from that of other related wingless insects, e.g. heel walkers (Mantophasmatodea), ice crawlers (Grylloblattodea), and certain grasshoppers (Caelifera). The composition of direct flight muscles largely follows similar patterns in winged respectively wingless species within major polyneopteran lineages, but it is highly heterogeneous between those lineages.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0612-5) contains supplementary material, which is available to authorized users.