Retractor Muscle Research Articles

Right Lung Agenesis Associated with Dextrocardia in Adulthood

Introduction: Pulmonary agenesis is a rare lung disease, occurring in approximately 1 out of every 100,000 births. Most cases of pulmonary agenesis result in death during the neonatal period. Although survival in cases of pulmonary agenesis is rare, it is possible to encounter lung agenesis in adults. Case: A 26-year-old female patient presented with progressive dyspnea. On physical examination, retraction of the breathing muscles, reduced chest excursions, and decreased breath sounds on the right side were observed. A chest X-ray raised suspicion of pulmonary agenesis. A computed tomography (CT) scan showed hypoplasia of the right lung, accompanied by mediastinal shift, hyperinflation of the left lung, and retraction of the diaphragm and liver to the right. Spirometry showed moderate obstruction. Conclusion: Pulmonary agenesis in adult patients is extremely rare. Chest X-rays and CT scans are the main diagnostic modalities for pulmonary agenesis. There is no specific treatment for asymptomatic cases. Management focuses on conservative and symptomatic care.

Reassessment and phylogenetic position of the overlooked limacoid land snail Trochomorpha sculpticarina Martens, 1883 (Eupulmonata, Ariophantidae), with the description of a new genus

The Malay Peninsula has traditionally been considered to harbour a diverse land-snail fauna, both in terms of a high species richness and a wide variety of conchological traits, especially within the limacoid land snails. A recent survey along the Malay Peninsula of southern Thailand discovered an overlooked limacoid taxon “Trochomorpha” sculpticarina Martens, 1883, previously assigned to genus Trochomorpha of the Trochomorphidae. This genus is herein described as Janbinmorphagen. nov. based on comparative studies of shell morphology, external features, genital anatomy and radular morphology, as well as analyses of partial sequences of two mitochondrial markers, COI and 16S rRNA, and of one nuclear marker, 28S rRNA. This new genus is characterised by a combination of distinct morphological and anatomical features. The most distinguishing features are a depressed trochiform shell with a keeled last whorl, gametolytic organ without a duct, gametolytic sac with two lobes, and proximal epiphallus encircled with a thick sheath and attached by the penial retractor muscle. In addition, an analysis of the differentiation in mitochondrial and nuclear markers confirmed that this new genus, first recognised by morphology, is also genetically distinct. The molecular data also confirm that J. sculpticarinacomb. nov. is a member of the Ariophantidae and has a close evolutionary relationship to Hemiplecta and Maelamaodiscus.

Phascolion kamchatikus sp. nov., the first interstitial sipunculan (Sipuncula, Phascolionidae) from the Pacific Ocean

A new species of meiobenthic sipunculan, Phascolion kamchatikus sp. nov. collected from coarse sand and shell hash in shallow waters in the northwestern Pacific, is described and illustrated using light and electron microscopy. This new species is well distinguished from all other congeners by a unique combination of main taxonomic characters. This is the only sipunculan having only two primary tentacles in both juvenile and sexually mature worms. There are no hooks and holdfast papillae in the adult stages. Because of the presence of three nearly equal in size retractor muscles forming a retractor column divided for most of its length, this species is assigned to the subgenus Isomya of the genus Phascolion. Unlike most other species of the genus Phascolion, P. kamchatikus sp. nov. has an interstitial mode of life moving among the coarse sand grains and shell hash accumulated between rocks and stones in shallow water areas alongside the Pacific coast of Kamchatka, Aleutian Islands and Alaska Peninsula. Phascolion kamchatikus sp. nov. constitutes the only third interstitial species of the phylum Sipuncula. This is also the ninth species of Phascolion in the northwestern Pacific and the first interstitial representative of this genus in the Pacific Ocean.

Full Hill-type muscle model of the I1/I3 retractor muscle complex in Aplysia californica.

The coordination of complex behavior requires knowledge of both neural dynamics and the mechanics of the periphery. The feeding system of Aplysia californica is an excellent model for investigating questions in soft body systems' neuromechanics because of its experimental tractability. Prior work has attempted to elucidate the mechanical properties of the periphery by using a Hill-type muscle model to characterize the force generation capabilities of the key protractor muscle responsible for moving Aplysia's grasper anteriorly, the I2 muscle. However, the I1/I3 muscle, which is the main driver of retractions of Aplysia's grasper, has not been characterized. Because of the importance of the musculature's properties in generating functional behavior, understanding the properties of muscles like the I1/I3 complex may help to create more realistic simulations of the feeding behavior of Aplysia, which can aid in greater understanding of the neuromechanics of soft-bodied systems. To bridge this gap, in this work, the I1/I3 muscle complex was characterized using force-frequency, length-tension, and force-velocity experiments and showed that a Hill-type model can accurately predict its force-generation properties. Furthermore, the muscle's peak isometric force and stiffness were found to exceed those of the I2 muscle, and these results were analyzed in the context of prior studies on the I1/I3 complex's kinematics in vivo.

Ankle impingement after extra-articular open fracture of the leg: Full arthroscopic treatment in the supine position

ObjectiveExtra-articular open fractures of the leg often result from high energy trauma. After healing, a painful ankle impingement may occur. In the event of anterior and posterior impingements, arthroscopic treatment may require two surgical positions. We propose an operative strategy to treat anterior and posterior ankle impingement after extra-articular open fracture of the leg. Our hypothesis is that this strategy is simple, effective and with a low risk of complication. Material and methodAnterior ankle impingements were treated by anterior arthroscopy in supine position; anterior and posterior impingements were treated by anterior and posterior arthroscopy in supine position; anterior and posterior impingements associated with retraction of gastrocnemius muscles were treated with anterior arthroscopy in supine position followed by posterior arthroscopy in prone position, and an open tendon lengthening of the calcaneal tendon in the same position. The anterior and posterior arthroscopic release was tested in the cadaver laboratory. Then, the surgical strategy was applied to our patients in our clinical practice. After, we analysed retrospectively the results of the strategy in the first patients treated for a painful ankle impingement after extra-articular open fracture of the leg. The data retrieved were the importance of pain (VAS), the presence of clinical instability, ankle mobility, gastrocnemius retraction and the AOFAS functional score and the post-operative complications. Then, these data were compared before the surgery and at last follow-up. ResultsFrom the cadaver laboratory, anterior and posterior arthroscopic release was possible in all cases without changing position. From our clinical practice, we included 5 patients (3 women and 2 men, mean age 43 years) suffering from an ankle impingement after extra-articular open fracture of the leg (2 patients with isolated anterior impingement, 1 patient with anterior and posterior impingement, and 2 patients with anterior and posterior impingement plus a gastrocnemius retraction). All post-operative parameters (pain, range of motion and AOFAS score) at mean follow-up of 53 months were improved. No post-operative complication was reported. ConclusionWe propose a surgical strategy adapted to the different clinical presentations of ankle impingement after extra-articular open fracture of the leg.

Effects of body mass and taxonomic order on the masses of functionally classified groups of the jaw musculature in birds

Abstract There is increasing interest from evolutionary biologists in the evolution of avian bill shape, how the bill is used during feeding and, in particular, the bite forces the bill can deliver. Bite force exhibits isometry with the total mass of the jaw musculature, but there is variation in the functional categories of the jaw muscles in different avian taxa. Qualitative descriptions of the jaw musculature do not allow analysis of the relative contributions that adductor or retractor muscles play in generating a bite force. This study is a meta-analysis of published data for body mass and the mass of the jaw musculature in 66 bird species from 10 orders. The masses of the different muscles contributing to adduction and retraction in closing the jaw, and to depression and protraction in opening the jaw, were summed and allometric relationships explored before investigating the effects of taxonomic order on these relationships. The categories of muscles, and the masses of each category of jaw musculature varied among avian orders. Some species, such as the flightless ratites, had relatively small jaw muscle mass but parrots had an additional adductor muscle. Phylogenetically controlled relationships between body mass and the mass of each muscle category irrespective of taxonomic order were isometric. However, analysis of covariance revealed significant interactions between body mass and taxonomic order. Most orders had low values for body-mass-specific muscle masses in the jaw with the notable exceptions of the Passeriformes (songbirds) and Psittaciformes (parrots). The values of these orders were 3–4 times greater, although the relative amounts of muscles contributing to adduction and retraction were similar in Psittaciformes, but adduction was markedly higher in Passeriformes. The results of these analyses highlight the lack of species-specific data for most birds, which is adversely impacting our understanding of the anatomical features that are determining the functional properties of the bill during feeding.

Strength and activity of the protractor and retractor muscles of the asymptomatic dyskinetic scapula

The role of scapular dyskinesis as a risk factor of shoulder injury has been largely discussed. However, most studies have focused on symptomatic patients and less is known on the asymptomatic dyskinetic scapula. Removing the confounding effects of the pathologies could contribute to better characterize the scapula dyskinesis. As muscle properties (strength, fatigue, nerve injury …) have been identified as causative factors of scapular dyskinesis, this study focuses specifically on characterizing the protractor and retractor muscles of the dyskinetic scapula. Thirteen asymptomatic dyskinetic volunteers were compared to eleven asymptomatic non-dyskinetic control volunteers. Muscle characteristics were evaluated in terms of maximal strength, fatigue resistance and electromyographic activity during a functional closed-chained task. The results did not identify kinematic or muscle activity significant differences between the dyskinetic and the control group even in fatigue conditions. However, the results demonstrated that protractors vs. retractors fatigue resistance ratios were imbalanced (<0.8) in the dyskinetic group and significantly lower than in the non-dyskinetic one. Our study suggests that that strength imbalances are not necessarily related to the presence of pain at the shoulder joint. These results demonstrated the importance to complete the clinical assessments of the scapula with strength evaluations even for asymptomatic sport practitioners.

Feasibility and Analgesic Efficacy of Thoracolumbar Dorsal Ramus Nerve Block Using Multiorifice Pain Catheters for Scoliosis Surgery: A Prospective Cohort Study.

Approximately 38,000 scoliosis surgery correction operations are performed annually in the United States; these operations are associated with considerable postoperative pain which can be difficult to manage. This is largely attributed to an incision spanning multiple vertebral segments with paraspinal muscle dissection and retraction to facilitate the implantation of segmental hardware and rods. Frequently utilized analgesic modalities include intravenous patient-controlled analgesia and epidural analgesia, often in combination. We sought to ascertain the feasibility and analgesic efficacy of continuous thoracolumbar dorsal ramus nerve (TDRN) block using surgically placed multiorifice catheters. Forty-two patients diagnosed with idiopathic scoliosis who underwent a posterior spinal fusion (PSF) were enrolled after consent was obtained. Patients were managed utilizing a standardized Enhanced Recovery After Surgery) protocol including a perioperative opioid-sparing regimen. Data were collected at specified time intervals during the recovery period. These data points included pain scores using the Numeric Rating Scale. Parenteral or both oral and parenteral opioid consumption doses were also collected every 4 hours. Any significant postoperative adverse events were recorded as well. A total of 42 patients had surgically placed TDRN catheters, and 40 patients were included in this study. The patients all reported low to moderate pain scores with low opioid consumption postoperatively, while the TDRN catheter delivery of local anesthetic analgesics did not result in significant complications. A regional technique utilizing TDRN catheters could be a valuable component of the postoperative pain management protocols for PSF surgery, and additional studies are warranted. This study evaluated the feasibility and analgesic efficacy of TDRN catheters for postoperative pain control following multilevel PSF for idiopathic scoliosis. Continuous local anesthetic delivery through TDRN catheters is a feasible and safe technique for postoperative pain control in these patients. Selective blockade of the dorsal rami might have benefits over epidural analgesia or other regional techniques.

Hedgehog signaling is required for larval muscle development and larval metamorphosis of the mussel Mytilus coruscus

Understanding the developmental processes and signaling pathways involved in larval myogenesis and metamorphosis is crucial for comprehending the life history and adaptive strategies of marine organisms. In this study, we investigated the temporal and spatial patterns of myogenesis in the mussel Mytilus coruscus (Mc), focusing on the emergence and transformation of major muscle groups during different larval stages. We also explored the role of the Hedgehog (Hh) signaling pathway in regulating myogenesis and larval metamorphosis. The results revealed distinct developmental stages characterized by the emergence of specific muscular components, such as velum retractor muscles and anterior adductor muscles, in D-veliger and umbo larvae, which are responsible for the planktonic stage. In the pediveliger stage, posterior ventral, posterior adductor, and foot muscles appeared. After larval metamorphosis, the velum structure and its corresponding retractor muscles degenerate, indicating the transition from planktonic to benthic life. We observed a conserved pattern of larval musculature development and revealed a high degree of conservation across bivalve species, with comparable emergence times during myogenesis. Furthermore, exposure to the Hh signaling inhibitor cyclopamine impaired larval muscle development, reduced larval swimming activity, and inhibited larval metamorphosis in M. coruscus. Cyclopamine-mediated inhibition of Hh signaling led to reduced expression of four key genes within the Hh signaling pathway (McHh, McPtc, McSmo, and McGli) and the striated myosin heavy chain gene (McMHC). It is hypothesised that the abnormal larval muscle development in cyclopamine-treated groups may be an indirect effect due to disrupted McMHC expression. We provide evidence for the first time that cyclopamine treatment inhibited larval metamorphosis in bivalves, highlighting the potential involvement of Hh signaling in mediating larval muscle development and metamorphosis in M. coruscus. The present study provides insights into the dynamic nature of myogenesis and the regulatory role of the Hh signaling pathway during larval development and metamorphosis in M. coruscus. The results obtained in this study contribute to a better understanding of the evolutionary significance of Hh signaling in bivalves and shed light on the mechanisms underlying larval muscle development and metamorphosis in marine invertebrates.

Scaling of buccal mass growth and muscle activation determine the duration of feeding behaviours in the marine mollusc Aplysia californica.

The mechanical forces experienced during movement and the time constants of muscle activation are important determinants of the durations of behaviours, which may both be affected by size-dependent scaling. The mechanics of slow movements in small animals are dominated by elastic forces and are thus quasistatic (i.e. always near mechanical equilibrium). Muscular forces producing movement and elastic forces resisting movement should scale identically (proportional to mass2/3), leaving the scaling of the time constant of muscle activation to play a critical role in determining behavioural duration. We tested this hypothesis by measuring the duration of feeding behaviours in the marine mollusc Aplysia californica whose body sizes spanned three orders of magnitude. The duration of muscle activation was determined by measuring the time it took for muscles to produce maximum force as A. californica attempted to feed on tethered inedible seaweed, which provided an in vivo approximation of an isometric contraction. The timing of muscle activation scaled with mass0.3. The total duration of biting behaviours scaled identically, with mass0.3, indicating a lack of additional mechanical effects. The duration of swallowing behaviour, however, exhibited a shallower scaling of mass0.17. We suggest that this was due to the allometric growth of the anterior retractor muscle during development, as measured by micro-computed tomography (micro-CT) scans of buccal masses. Consequently, larger A. californica did not need to activate their muscles as fully to produce equivalent forces. These results indicate that muscle activation may be an important determinant of the scaling of behavioural durations in quasistatic systems.

Endoscopic submucosal dissection using a detachable snare for a large colorectal tumor with muscle retraction.

Endoscopic submucosal dissection using a detachable snare for a large colorectal tumor with muscle retraction.

The effect of strabismus surgery on psychosocial and functional quality of life

Aims: To evaluate the effect of strabismus surgery on psychosocial and functional quality of life. Methods: 50 adult strabismus patients who presented to our outpatient clinic with the complaint of strabismus in one eye were included in the study. Routine ophthalmologic examinations and strabismus controls were performed. With the diagnosis of monocular fixed eso/exotropia, unilateral horizontal muscle retraction and resection surgery were planned, and preoperative adult strabismus score (AS-20), Rosenberg self-esteem, body perception, and social appearance anxiety questionnaires were applied. A postoperative PD of 10 or less was considered success, and the questionnaires were repeated at the 2nd postoperative month. Results: The mean age of the patients was 21.54±3.95 (16-32) years. Twenty-two of the patients were female, and 28 were male. Pre-operative and post-operative strabismus AS-20 score, Rosenberg self-esteem, body perception, and social appearance anxiety scales showed statistically significant differences (p&lt;0.05, p&lt;0.001, p&lt;0.001, p&lt;0.001, p&lt;0.001). Conclusion: Strabismus is an important disease that can cause difficulties in social life both in childhood and adulthood. The aim of strabismus surgery is to restore normal facial appearance as well as functional correction. Our study results showed that successful strabismus surgery can improve the psychosocial and functional quality of life.

Direct Anterior Approach in Total Hip Arthroplasty for Severe Crowe IV Dysplasia: Retrospective Clinical and Radiological Study.

Background and Objectives: total hip arthroplasty (THA) for Crowe IV hip dysplasia poses challenges due to severe leg shortening, muscle retraction and bone stock issues, leading to an increased neurological complication, and revision rate. The direct anterior approach (DAA) is used for minimally invasive THA but its role in Crowe IV dysplasia is unclear. This retrospective study examines if DAA effectively restores hip biomechanics in Crowe IV dysplasia patients with <4 cm leg length discrepancy, managing soft tissue and yielding functional improvement, limb length correction, and limited complications. Materials and Methods: 19 patients with unilateral Crowe IV hip osteoarthritis and <4 cm leg length discrepancy undergoing DAA THA were reviewed. Surgery involved gradual soft tissue release, precise acetabular cup positioning, and stem placement without femoral osteotomy. Results: results were evaluated clinically and radiographically, with complications recorded. Follow-up revealed significant Harris Hip Score and limb length discrepancy improvements. Abductor muscle insufficiency was present in 21%. The acetabular component was accurately placed, centralizing the prosthetic joint's rotation. Complications occurred in 16% of cases, including fractures, nerve issues, and infection. DAA in THA showcased positive outcomes for hip function, limb length, and biomechanics in Crowe IV dysplasia. Conclusions: the technique enabled accurate cup positioning and rotation center adjustment. Complications were managed well without implant revisions. DAA is a viable option for Crowe IV dysplasia, restoring hip function, biomechanics, and reducing limb length discrepancy. Larger, longer studies are needed for validation.

Marteilia pararefringens infections are more frequent than revealed by the Norwegian surveillance programme, highlighting the need for its improvement.

Norway had historically been considered free of marteiliosis in bivalves since the disease surveillance programme began in 1995. However, in 2016, Marteilia pararefringens, a protistan parasite of mussels Mytilus spp., was described in a heliothermic lagoon-a poll-previously used to produce flat oyster spat. To study whether the parasite was introduced, and possibly spread, via the historical flat oyster networks on the south and west coast, we sampled aquaculture polls that were part of different networks of farmers and wild, natural polls with no aquaculture activity. Additionally, we sampled mussel banks influenced by polls and sheltered bays that could have a similar environment to that of polls. We identified 7 sites with M. pararefringens-infected mussel populations: 5 were polls used in flat oyster production and 2 were in fjord areas with no known connection to any bivalve aquaculture. Prevalence ranged between 2 and 88%. At one site, Trysfjorden, we found M. pararefringens in atypical organs, including the gills, mantle, and intestine. Marteilia-like cells were also observed in the epithelium, lumen, and surrounding connective tissue of metanephridia and in the sinus of the anterior retractor muscle. Our results demonstrate that the parasite is more widespread than previously thought and is neither isolated to polls nor connected directly to aquaculture activity. Lastly, our findings highlight the need for an improved sampling strategy in surveillance programmes to detect marteiliosis in mussels.

Loss of domain and reduction in median suture tension

Abdominal wall reconstruction in large incisional hernia/laparostoma poses aparticular challenge. A loss of domain is the extreme form of intestinal volume displacement. The challenge lies in overcoming retraction of the lateral abdominal muscles. Experienced surgeons have access to avariety of techniques aimed at gaining lateral length along the abdominal wall or reducing suture tension at the midline. These techniques are intended to facilitate reconstruction even in complex cases and are outlined in this article from apractical perspective. The application of botulinum toxinA (BTA) and progressive pneumoperitoneum (PPP) are described as preoperative methods to gain abdominal wall length. Peritoneal flaps, intraoperative fascial traction (IFT) and component separation including transversus abdominis muscle release (TAR) are available for the surgical reconstruction of the abdominal wall. Bridging and the intraperitoneal onlay mesh approach are fallback techniques. All these techniques were integrated into apractical algorithm for complex abdominal wall reconstruction including preoperative and postoperative care and assessed by the authors with respect to effort, effectiveness and complexity. In the opinion of the authors, the status of complex abdominal wall reconstruction is currently best described by acombination of the most effective and proven techniques in terms of a"categorical algorithm". The combination of BTA, IFT and TAR presently appears to be the most effective method; however, experience and expertise are aprerequisite.

PHYSICAL THERAPY AND NEUROREHABILITATION OF PATIENTS WITH CEREBROVASCULAR STROKE

Cerebral stroke represents an acute disturbance of circulation in the brain, which occurs with local and general brain symptoms. Main etiological factors are: arteriosclerosis, increased blood pressure, arterial hypotension, heart diseases, malformations of brain blood vessels, etc. Stroke is the most common neurological disease and the leading cause of mortality in the world, right after cardiovascular and malignant diseases. Cerebrovascular stroke is a focal neurological deficit caused by intracerebral hemorrhage. It is a condition that occurs due to a change in blood circulation in the brain and a very low supply of oxygen and nutrients to parts of the brain, which results in their damage and disruption of the functions that depend on them. There are two types of cerebrovascular stroke: ischemic - thrombosis and thromboembolism (85%) and hemorrhagic – intracerebral and subarachnoid bleeding (15%). The clinical picture can develop gradually or, the patient can suddenly fall into a coma. Absence of movements of the affected limbs predominates, always opposite to the side of the impact with an outburst of the facial nerve of the central type. Hemiplegia is a loss of the voluntary movements of one half of the body, caused by damage to the opposite brain hemisphere. The musculature is atonic, tendon reflexes are reduced or lost. The aim of the research is to determine the effectiveness of physical therapy and neurorehabilitation in patients with cerebrovascular brain stroke. Treatment of stroke: In the acute stage, physical therapy is aimed at preventing complications of the loco-motor apparatus (contractures, muscle and tendon retraction, heterotropic ossifications), the respiratory system (hypostatic pneumonia) and the skin (decubitus). This is achieved through treatment with position (frequent change of the position of the body in bed), passive exercises performed according to strictly defined rules, breathing exercises, exercises for healthy limbs and great care of the skin. The trophic changes of the skin are treated with ultraviolet radiation in suberythemic doses or with D’Arsonval currents. The research was conducted at the University of Southeast Europe - (Stul University) at the Faculty of Health Sciences in the Department of Physical Therapy and Rehabilitation, over a period of 6 months, from the beginning of From the beginning of May - to the end of October 2023. The research included 27 stroke patients, of which 11 patients had a left-sided stroke, and the remaining 14 patients had a right-sided stroke. According to the gender structure, 12 patients are male and the remaining 15 patients are female. After completing the six-month treatment with physical therapy, kinesitherapy and the methods of Vojta and Carl and Bertha Bobat, the results show great progress in almost all parameters. A decrease in tonic primitive reflexes, neck and labyrinthine tonic reflexes, reduction of extensor hypertonia, improvement of motor-reflex activity, proprioceptive afference, coordination, reduction of neck tone, foot reflex, stimulation of the grip reflex and improvement of the position of the neck, limbs and body. The presented results shows significant improvement in both groups of participants. Physical therapy and rehabilitation combined with kinesitherapy have an exceptional positive effect in: prevention of pathological primitive reflexes;creation and automation of normal active movements;saving irregular positions of the limbs and the whole body;establishment of balance and correct pattern of movement; fight against spasticity, secondary contractures and deformities; improvement of coordination and awareness of the body in relation to the environment.

Facing the facts: adaptive trade-offs along body size ranges determine mammalian craniofacial scaling.

The mammalian cranium (skull without lower jaw) is representative of mammalian diversity and is thus of particular interest to mammalian biologists across disciplines. One widely retrieved pattern accompanying mammalian cranial diversification is referred to as 'craniofacial evolutionary allometry' (CREA). This posits that adults of larger species, in a group of closely related mammals, tend to have relatively longer faces and smaller braincases. However, no process has been officially suggested to explain this pattern, there are many apparent exceptions, and its predictions potentially conflict with well-established biomechanical principles. Understanding the mechanisms behind CREA and causes for deviations from the pattern therefore has tremendous potential to explain allometry and diversification of the mammalian cranium. Here, we propose an amended framework to characterise the CREA pattern more clearly, in that 'longer faces' can arise through several kinds of evolutionary change, including elongation of the rostrum, retraction of the jaw muscles, or a more narrow or shallow skull, which all result in a generalised gracilisation of the facial skeleton with increased size. We define a standardised workflow to test for the presence of the pattern, using allometric shape predictions derived from geometric morphometrics analysis, and apply this to 22 mammalian families including marsupials, rabbits, rodents, bats, carnivores, antelopes, and whales. Our results show that increasing facial gracility with size is common, but not necessarily as ubiquitous as previously suggested. To address the mechanistic basis for this variation, we then review cranial adaptations for harder biting. These dictate that a more gracile cranium in larger species must represent a structural sacrifice in the ability to produce or withstand harder bites, relative to size. This leads us to propose that facial gracilisation in larger species is often a product of bite force allometry and phylogenetic niche conservatism, where more closely related species tend to exhibit more similar feeding ecology and biting behaviours and, therefore, absolute (size-independent) bite force requirements. Since larger species can produce the same absolute bite forces as smaller species with less effort, we propose that relaxed bite force demands can permit facial gracility in response to bone optimisation and alternative selection pressures. Thus, mammalian facial scaling represents an adaptive by-product of the shifting importance of selective pressures occurring with increased size. A reverse pattern of facial 'shortening' can accordingly also be found, and is retrieved in several cases here, where larger species incorporate novel feeding behaviours involving greater bite forces. We discuss multiple exceptions to a bite force-mediated influence on facial proportions across mammals which lead us to argue that ecomorphological specialisation of the cranium is likely to be the primary driver of facial scaling patterns, with some developmental constraints as possible secondary factors. A potential for larger species to have a wider range of cranial functions when less constrained by bite force demands might also explain why selection for larger sizes seems to be prevalent in some mammalian clades. The interplay between adaptation and constraint across size ranges thus presents an interesting consideration for a mechanistically grounded investigation of mammalian cranial allometry.

WntA and Wnt4 during the regeneration of internal organs in the holothurian Eupentacta fraudatrix.

Over the past few years, it has been established that wnt genes are involved in the regenerative processes of holothurians. The wnt4 gene was identified as one of the most active genes in Eupentacta fraudatrix regeneration using differential gene expression analysis and qPCR of individual genes. Also, the wntA gene was found in holothurians, which is present only in invertebrates and can perform unique functions. In this regard, both these genes and proteins were studied in this work. During regeneration, the Wnt4 protein is found in the cells of the coelomic and ambulacral epithelium, retractor muscles, and radial nerves. Single cells with this protein are also found in the connective tissue of the developing aquapharyngeal bulb and in the hypoderm of the body wall. Cells with WntA are found exclusively in the hypoderm of the body wall. We assume that both genes are involved in regeneration, but Wnt4 coordinates the formation of the epithelial tissue structure, while WntA maintains the state of the intercellular substance of the body wall.

Musculature of an Early Cambrian cycloneuralian animal.

Cycloneuralians are ecdysozoans with a fossil record extending to the Early Cambrian Fortunian Age and represented mostly by cuticular integuments. However, internal anatomies of Fortunian cycloneuralians are virtually unknown, hampering our understanding of their functional morphology and phylogenetic relationships. Here we report the exceptional preservation of cycloneuralian introvert musculature in Fortunian rocks of South China. The musculature consists of an introvert body-wall muscular grid of four circular and 36 radially arranged longitudinal muscle bundles, as well as an introvert circular muscle associated with 19 roughly radially arranged, short retractors. Collectively, these features support at least a scalidophoran affinity, and the absence of muscles associated with a mouth cone and scalids further indicates a priapulan affinity. As in modern scalidophorans, the fossil musculature, and particularly the introvert circular muscle retractors, may have controlled introvert inversion and facilitated locomotion and feeding. This work supports the evolution of scalidophoran-like or priapulan-like introvert musculature in cycloneuralians at the beginning of the Cambrian Period.

Litophellia enoplosa sp. nov., a new species of sea anemone (Actiniaria, Metridioidea) from cold-water coral environments in the North-western Mediterranean Sea

A new species of sea anemone (Actiniaria, Metridioidea) is described and illustrated from cold-water coral environments at 600 m depth at the Blanes Canyon in the north-western Mediterranean Sea. Litophellia enoplosa sp. nov. is characterized by a column divisible into scapus and scapulus, the former with cuticle forming tenaculi, a mesogleal marginal sphincter muscle, more mesenteries proximally than distally arranged octomerously, and a single pair of directive mesenteries; it has strong retractor and parietobasilar muscles, and acontia with basitrichs and p-mastigophores B2a. Litophellia enoplosa sp. nov. is the second species described in the genus and it can be distinguished from the other species by the cuticle in the column, size ranges of the cnidae, and geographic and bathymetric distribution.