Journal of Anatomy最新文献

{"title":"Aging-related morphological changes in the obturator internus and levator ani.","authors":"Satoru Muro, Junichi Tsuchiya, Takuya Ibara, Akimoto Nimura, Keiichi Akita","doi":"10.1111/joa.70256","DOIUrl":"https://doi.org/10.1111/joa.70256","url":null,"abstract":"<p><p>Pelvic floor dysfunction is a common condition in adult women. In addition to the levator ani, the obturator internus, a lateral pelvic wall muscle, has been suggested to be anatomically and mechanically associated with pelvic floor morphology. Here, we quantitatively characterized age-related morphological changes in the obturator internus and levator ani using geometric morphometric analysis. We hypothesized a significant association between principal components accounting for major shape variation and age. This cross-sectional study included 27 adult women aged 25-83 years with gynecological conditions but without pelvic floor disorders based on clinical assessment and imaging findings. Standardized pelvic magnetic resonance imaging scans were obtained between April 2024 and July 2024 at a single tertiary care center. Elliptic Fourier analysis was applied to the segmented obturator internus contours; a landmark-based method was used to evaluate the combined shape of the obturator internus and levator ani. Principal component analysis and linear regression were performed to assess associations with age. Procrustes analysis of variance was used to evaluate the overall shape-age relationships. Elliptic Fourier analysis revealed that increasing age was significantly associated with relative narrowing of the superior portion, an inferior morphological shift of the medial surface groove, and increased prominence of the medial eminence of the obturator internus. A landmark-based analysis revealed similar age-related shape changes, including inferiorly directed shape changes of the groove, verticalization of the levator ani, and widening of the levator hiatus. Procrustes analysis revealed a significant relationship between age and overall shape variation. Aging was associated with coordinated age-related morphological remodeling of the obturator internus and levator ani.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149224209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantitative analysis of intrarenal nerve-associated profiles in the human foetal kidney between 14 and 30 gestational weeks: An S100 immunohistochemical study.","authors":"Ivan Petrović, Ana Balenović, Milana Bosanac, Srdjan Stanković, Isidora Milosavljević, Milena Šunjević, Sandra Trivunić Dajko, Bojana Andrejić-Višnjić","doi":"10.1111/joa.70260","DOIUrl":"10.1111/joa.70260","url":null,"abstract":"<p><p>Quantitative data on the spatial development of intrarenal S100-positive nerve-associated profiles in human foetal kidneys remain limited, despite the established importance of renal nerves. Building on the previously published semiquantitative observations, this study aimed to generate a quantitative, compartment-resolved map of S100-positive nerve-associated profiles in human foetal kidneys. Formalin-fixed, paraffin-embedded human foetal kidney specimens ranging from 14 to 30 gestational weeks were analysed using S100 immunohistochemistry. Based on gestational age, specimens were divided into three groups: ≤18 gestational weeks (G1, n=6), 19-24 gestational weeks (G2, n=6), and ≥ 25 gestational weeks (G3, n=6). Cortical maturation was assessed by measuring nephrogenic zone and maturation zone thickness and calculating the cortical maturation index (CMI). Morphometric analysis of cortical S100-positive nerve-associated profiles was performed using digital image analysis. Distribution patterns of S100-positive profiles were assessed qualitatively. Group-wise analysis demonstrated significantly lower cortical S100-positive area in G1 compared with G2 and G3 (median: 985 μm² vs. 1733 μm² and 2400 μm², respectively; p < 0.001). Cortical S100-positive area increased significantly with gestational age and foetal weight and showed an inverse correlation with CMI (ρ = -0.410, p < 0.001), indicating parallel progression of S100-positive area and cortical maturation. In multivariate linear regression analyses, cortical S100-positive area remained independently associated with gestational age (β = 125.0, p = 0.006) and foetal weight (β = 1.50, p = 0.006), explaining 57.6% of the variance (adjusted R² = 0.485). Perivascular localisation was the most frequently observed distribution pattern, while juxtaglomerular and intraglomerular patterns were also identified, including in the earliest gestational-age group. This study provides the first quantitative, compartment-resolved analysis of intrarenal nerve-associated profiles in the human foetal kidney. Cortical S100-positive area increases with gestational age in parallel with cortical maturation and shows a predominantly perivascular distribution, consistent with a neurovascular co-development model and establishing a morphological framework for future functional studies of renal innervation.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13669555/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149181650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Developmental perturbations and the robustness of limb modularity: Insights from anuran anatomical networks.","authors":"Mónica C Soliz, Gabriela Fontanarrosa, Virginia Abdala","doi":"10.1111/joa.70255","DOIUrl":"10.1111/joa.70255","url":null,"abstract":"<p><p>Developmental anomalies provide a powerful window into the rules and constraints shaping morphological evolution. Here, we use anatomical network analysis to investigate how congenital perturbations affect the structural organization of anuran limbs. We analyzed a specimen of Leptodactylus bufonius exhibiting bilateral brachydactyly in both fore- and hindlimbs and unilateral polyphalangy, and compared its limb networks to those of a typical conspecific. Developmental perturbations resulted in structural reorganization, including reduced node and link number and increased graph density. At the node level, betweenness centrality markedly declined in stylopodial and zeugopodial elements, disrupting the characteristic proximodistal hub-periphery organization of the limb. This shift reflects a loss of proximodistal polarization associated with distal reduction. Modular organization was robust to these perturbations: module number remained unchanged in the forelimbs and in the left hindlimb, and decreased in the right hindlimb, which exhibited the most extensive morphological reduction. Although module membership showed subtle changes, the overall number and composition of modules remained broadly conserved across reference and anomalous limbs. Thus, despite substantial anatomical perturbation, modular organization was largely maintained, with marked reorganization occurring only in the most severely affected limb. The anomalous morphology studied here demonstrates that developmental systems can accommodate profound modifications while maintaining organismal viability. Our study engages with the broader community discussion on modularity and the methodological frameworks used to investigate it. More broadly, this study highlights how anatomical network approaches can contribute to evo-devo research by quantifying how developmental disruptions reshape the organization of complex morphological systems.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13655320/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149170144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Allometric patterns in Rhamphorhynchus muensteri and their role in the paleoecology, life habits, and taxonomic framework of pterosaurs","authors":"Gabriela Menezes Cerqueira,&nbsp;João Lucas Da Silva,&nbsp;Ingmar Werneburg,&nbsp;Mario Bronzati,&nbsp;Alex Sandro Schiller Aires,&nbsp;Felipe L. Pinheiro,&nbsp;Rodrigo Temp Müller","doi":"10.1111/joa.70146","DOIUrl":"10.1111/joa.70146","url":null,"abstract":"<p>Pterosaurs were the first vertebrates to achieve powered flight, a result of various unique anatomical adaptations, and significant morphological diversity throughout their evolutionary history. Although the pterosaurs body structure was specialized for powered flight, the clade exhibited great disparity from its origins, with later evolution giving rise to multiple phylogenetic lineages and a wide range of body sizes, from small forms such as <i>Anurognathus ammoni</i> to truly giant species like <i>Quetzalcoatlus northropi</i>. This variation led to distinct flight strategies within the group. Here, we assess allometry in the skeletal elements of <i>Rhamphorhynchus muensteri</i> in comparison with Eupterodactyloidea and Euctenochasmatia, examining their implications for paleoecology and flight capacity. The analysis included 127 specimens and assessed 13 skeletal variables using statistical methods, principal components analysis (PCA), and standardized major analysis (SMA). The results reveal differences in size–shape trajectories and functional adaptations related to activity flight. <i>R. muensteri</i> exhibits a trend of negative allometry (PCRW/body, humerus, radius/ulna, metacarpal IV, and femur), indicating distinct allometric scaling patterns and flight style. These patterns suggest behavior and ecological differences, as well differing flight capabilities between <i>R. muensteri</i> likely relied on active flapping flight interspersed with gliding, whereas other taxa may have exhibited greater migratory adaptations within Eupterodactyloidea, and a greater dependence on flapping flight in Euctenochasmatia. The negative allometry in <i>R. muensteri</i> suggests a flight style characterized by early flight capability (precocial flight), whereas Eupterodactyloidea showed positive allometry and Euctenochasmatia isometry. Additionally, the study highlights how allometric patterns influence pterosaur phylogeny, underscoring the importance of incorporating them into future analysis.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":"249 5","pages":"1005-1020"},"PeriodicalIF":2.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/joa.70146","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147838071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The variability of giraffe skull morphology","authors":"Nikolaos Kargopoulos,&nbsp;Jesús Marugán-Lobón,&nbsp;Anusuya Chinsamy-Turan,&nbsp;Bernard R. Agwanda,&nbsp;Michael Butler Brown,&nbsp;Stephanie Fennessy,&nbsp;Sara Ferguson,&nbsp;Rigardt Hoffman,&nbsp;Fredrick Lala,&nbsp;Arthur Muneza,&nbsp;Ogeto Mwebi,&nbsp;Moses Otiende,&nbsp;Alice Petzold,&nbsp;Sven Winter,&nbsp;Abdoul Razack Moussa Zabeirou,&nbsp;Julian Fennessy","doi":"10.1111/joa.70157","DOIUrl":"10.1111/joa.70157","url":null,"abstract":"<p>Giraffe (<i>Giraffa</i> spp.) are among the most unique and charismatic extant animals, largely due to their distinct morphology. The evolutionary and developmental origin of ossicones is a key factor in giraffid biology, yet other features building their characteristic head physiognomy remain poorly studied. Here, we analysed the cranial diversity of extant <i>Giraffa</i> using a continent-wide sample with a balanced sex ratio and ontogenetic growth series, using shape analysis (3D geometric morphometrics). Detailed comparisons showed significant differences in cranial morphology across the four <i>Giraffa</i> species, and in some cases also between subspecies of the same species. The analyses revealed that females reach adult cranial form at an earlier age (around 4 years old), while males continue growing until the eighth year, aligning with the onset of sexual maturity for each of the sexes. Multivariate methods unambiguously prompt significant covariation between skull parts. Such high covariation patterns indicate that <i>Giraffa</i> skull morphology largely evolves as a whole (i.e., morphologically integrated), even though parts of it (such as the ossicones) develop in different magnitudes. Considering their role in territorial and mating behaviours, we suggest that ossicone morphology influences the parapatric evolution of <i>Giraffa</i> through sexual selection. Palaeontological evidence shows that development of larger ossicones is a relatively recent trait for members of the genus <i>Giraffa</i>, with the cranial morphology of the southern giraffe (<i>Giraffa giraffa</i>) being the closest to that of the ancestral forms, possibly through plesiomorphy or paedomorphosis.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":"249 5","pages":"1068-1086"},"PeriodicalIF":2.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/joa.70157","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147815325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An investigation of the functional significance of the pyramidalis muscle using shear wave elastography","authors":"Craig L. Short,&nbsp;Troy Morrison,&nbsp;Tania N. Crotti,&nbsp;Kent Algate,&nbsp;Marc A. Gladman,&nbsp;Christen D. Barras","doi":"10.1111/joa.70160","DOIUrl":"10.1111/joa.70160","url":null,"abstract":"<p>The pyramidalis (Py) is a small triangular-shaped anterior abdominal wall muscle, the function of which remains uncertain. We used brightness-mode (B-mode) ultrasound to determine Py prevalence and tested the hypothesis that Py contributed to stiffness of the linea alba (LA) using shear wave elastography (SWE). Py prevalence was observed and documented using conventional B-mode ultrasound in 20 participants (7 male). LA stiffness was measured using SWE with Py relaxed and during Py contraction in 10 of the participants (3 male, mean [SD] age 26.3 ± 8.0 years). Py activity was controlled using neuromuscular electrical stimulation (NMES), while lower rectus abdominis activity was monitored using electromyography (EMG). Py was present bilaterally in 15 of 20 (75%) participants, unilaterally in 2 (10%) and absent in 3 (15%). A statistically significant difference <i>(p</i> &lt; 0.002) in the mean LA stiffness was observed when comparing SWE measurements of the Py at relaxed (15.7 kPa ± 6.1 kPa, 95% CI 11.4–20.1 kPa) and during contraction (24.2 kPa ± 10.8 kPa, 95% CI 16.5–32.0 kPa). No statistically significant difference in lower rectus abdominis activity was observed between the presence and absence of NMES (<i>p</i> = 0.517), indicating accurate and isolated Py stimulation. Our results indicate that Py muscle is commonly present (75% participants) and that Py contraction results in a significant increase in LA stiffness, supporting the previously unvalidated hypothesis that the function of Py, at least in part, is to increase LA stiffness and contribute to the biomechanics of the trunk.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":"249 5","pages":"1130-1137"},"PeriodicalIF":2.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13399048/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147771796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphological study of the supratrochlear foramen in Canis lupus ssp.","authors":"Mariana Batista,&nbsp;Maria Soares,&nbsp;Eduardo Marcelino,&nbsp;Luísa Mendes-Jorge,&nbsp;Graça Alexandre-Pires,&nbsp;Cleia Detry,&nbsp;Sónia Gabriel,&nbsp;Dulce Ferreira,&nbsp;Ana Elisabete Pires,&nbsp;Joana Catita","doi":"10.1111/joa.70153","DOIUrl":"10.1111/joa.70153","url":null,"abstract":"<p>The domestic dog (<i>Canis lupus familiaris</i>), a species characterized by remarkable phenotypic diversity resulting from selective breeding, is among the several mammals that may exhibit an anatomical perforation of the humeral condyle, designated as the supratrochlear foramen (STF). The prevalence of the STF varies considerably across mammalian species and has been proposed to reflect functional adaptations linked to evolutionary and biomechanical factors, particularly in the human humerus. To the best of our knowledge, comprehensive studies on STF variation within present-day canine populations remain scarce. This study aimed to determine the prevalence and morphology of the STF in extant dogs, and to compare these findings with those from Roman Imperial Period dogs, and Iberian wolves (<i>Canis lupus signatus</i>), a subspecies considered representative of the dog's wild ancestor, in order to explore evolutionary changes within <i>Canis lupus</i> subspecies. We analyzed 269 humeri (123 extant dogs, 76 ancient dogs, 70 Iberian wolves) using osteometric measurements and statistical analysis. Our results demonstrate that the STF was observed in 73.17% of extant dogs, compared to 82.89% in ancient dogs and 98.57% in Iberian wolves, suggesting a reduction in its prevalence over time in domestic lineages that may be linked to human-driven selection processes. In all studied groups, the STF was consistently located closer to the lateral humeral epicondyle, and its predominantly transversely elongated shape reveals a common morphological pattern across <i>Canis lupus</i> subspecies. Despite differences in humeral size among groups, STF dimensions showed a positive correlation with overall humeral measurements, with larger humeri exhibiting proportionally larger and more frequent STFs. Extant dogs displayed the smallest STF dimensions, followed by ancient dogs, with Iberian wolves having the largest. Considering the potential impact of the STF on the biomechanical properties of the distal humerus, this study provides new insights into its anatomical variability in dogs, emphasizing its clinical relevance for orthopedic diagnostic accuracy and surgical treatments in veterinary medicine.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":"249 5","pages":"1170-1180"},"PeriodicalIF":2.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13398924/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147690403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterisation of human hair follicle development","authors":"Zoe R. Sudderick,&nbsp;James D. Glover,&nbsp;Cameron Batho-Samblas,&nbsp;Barbara Bo-Ju Shih,&nbsp;Denis J. Headon","doi":"10.1111/joa.70150","DOIUrl":"10.1111/joa.70150","url":null,"abstract":"<p>Humans have a characteristic distribution of hair across the body. Visible, relatively long and thick terminal hair fibres are present on the scalp and eyebrows in childhood, and are stimulated to grow on other parts of the body, such as the beard and armpits, by hormones during puberty. The short and fine vellus hairs, in contrast, are not readily visible and cover most of the body, including the face. Here we report quantification of the timing and characteristics of hair follicle development in human embryogenesis, from gestational Weeks 8–19, and compare this to mouse hair follicle development. We find that human hair follicles develop first on the head, where we identify several distinct initiation sites, followed by the torso. Clustered follicular units are produced by secondary hair follicles budding off the epidermis from sites close to earlier-forming primary follicles. Arrector pili muscles are detected from gestational Week 17. Although terminal and vellus hair follicles have clear differences in the adult, both hair types initially develop from placodes and dermal condensates of similar size. Once their development is initiated, we find that human hair follicles grow and mature at the same rate, regardless of anatomical location, but have different density at different body sites. These findings demonstrate that regional differences in hair characteristics of human skin, such as the distinction between scalp and forehead, are largely caused by processes that act after the initial stages of hair follicle morphogenesis. Efforts to understand the evolution of human ‘hairlessness’ should, therefore, focus on genetic and cellular events that take place after hair follicle morphogenesis. We compared human skin appendages, including eccrine sweat glands, with those in mouse. We found that molecular markers, such as EDA, EDAR, SOX2 and WNT pathway components, are broadly similar in expression between both species, although species-specific differences do exist. Notably, SOX2 expression, which distinguishes different hair follicle types in the mouse, is detected in all human hair follicle types, though with a later onset of expression than that observed in mouse. Together with comparison of morphology and gene expression, these results support the use of embryonic mouse primary hair follicles as a model for human hair follicle development.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":"249 5","pages":"1033-1049"},"PeriodicalIF":2.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13398818/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147963921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Issue Cover (November 2026)","authors":"","doi":"10.1111/joa.70253","DOIUrl":"https://doi.org/10.1111/joa.70253","url":null,"abstract":"<p>Cover image: see V. Trinidad et al., ‘Comparative histological analysis of vertebrates reveals Triassic climate variability across southern Pangea’, this issue.</p><p>\u0000 \u0000 <figure>\u0000 <div><picture>\u0000 <source></source></picture><p></p>\u0000 </div>\u0000 </figure>\u0000 </p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":"249 5","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/joa.70253","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149099467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scratching beneath the surface: Quantification of muscle architecture and myosin heavy chain content in the forelimbs of black-tailed prairie dogs (Cynomys, Rodentia)","authors":"Luke A. Scheetz,&nbsp;Carter A. Burnett,&nbsp;Benjamin R. Kimble,&nbsp;David A. Eads,&nbsp;Michael T. Butcher","doi":"10.1111/joa.70158","DOIUrl":"10.1111/joa.70158","url":null,"abstract":"<p>Black-tailed prairie dogs (<i>Cynomys ludovicianus</i>) excavate burrow systems for a variety of reasons, including social organization and predator avoidance. As such, they have evolved a suite of musculoskeletal traits in their forelimbs that are employed for scratch-digging (i.e., digging motion performed by alternating power and recovery strokes). However, the degree to which their muscular anatomy has become modified in response to the selective pressures of their semi-fossorial lifestyle is unknown. To better understand the functional capacities of their forelimb musculature, dissections of <i>C. ludovicianus</i> (<i>N = 9</i>) were conducted to quantify limb mechanical advantage, muscle architectural properties, and myosin heavy chain (MHC) isoform content. Compared with previous data from other ground squirrels, forelimb muscle mass distribution in black-tailed prairie dogs is broadly similar with a large investment of scapular and shoulder muscle mass that accounts for two-thirds of the total forelimb muscle mass. The majority of muscles have long fascicles with correspondingly high fascicle length-to-muscle length (<i>L</i>_F/ML) ratios, whereas aside from the main carpal and digital flexors/extensors, selected intrinsic shoulder flexors/extensors, and the smallest elbow extensors, most muscles have low physiological cross-sectional area to muscle mass (PCSA/MM) ratios. Notably, only the massive m. pectoralis superficialis was considered to be a high power muscle by its architectural properties, although several muscles are modified for large joint torque or torque range, including m. latissimus dorsi and a well-developed m. triceps brachii long head. Mechanical advantage is correspondingly greatest at the shoulder joint, intermediate at the elbow joint, and low at the carpal joint. Lastly, muscle composition is fast-contracting by moderate expression of fast MHC-2B and low expression of slow MHC-1. That said, %MHC isoform content shows a predominance of fast MHC-2A as predicted, which progressively increases distally throughout the forelimb. These findings collectively suggest that <i>C. ludovicianus</i> is less specialized among burrowing rodents as hypothesized. Its forelimb musculoskeletal properties are likely constrained by a preference for medium soil types and cooperative social behavior, and may further represent a trade-off between terrestrial locomotor behavior and digging function. Nonetheless, the modifications observed are comparible with other semi-fossorial members of the Marmotini tribe with respect to distinctive traits for scratch-digging. Future work is needed to quantify muscle properties in additional genera (e.g., <i>Tamias</i>, <i>Spermophilus</i>) to better assess selection for burrowing in ground squirrels.</p>","PeriodicalId":14971,"journal":{"name":"Journal of Anatomy","volume":"249 5","pages":"1181-1207"},"PeriodicalIF":2.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13398623/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147815373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}