Journal of Morphology最新文献

{"title":"Remodeling of Uterine Tissues During Gestation of Potamotrygon wallacei (Elasmobranchii), a Neotropical Freshwater Stingray Endemic to the Negro River, Central Amazonia","authors":"Michelly Siqueira-Souza,&nbsp;Maria Glauciney Amazonas,&nbsp;Kedma Cristine Yamamoto,&nbsp;Wallice Paxiúba Duncan","doi":"10.1002/jmor.21772","DOIUrl":"https://doi.org/10.1002/jmor.21772","url":null,"abstract":"<div>\u0000 \u0000 <p>Neotropical freshwater stingrays of the subfamily Potamotrygoninae exhibit aplacental viviparity with uterine trophonemata. In this reproductive mode, females nourish and provide oxygenation to the embryo via the mucosa of the uterine wall. The aim of this study was to describe and histologically quantify the tissue components of the gravid uterus in an Amazonian freshwater stingray. Adult females of <i>Potamotrygon wallacei</i> were studied in different reproductive periods: resting stage, pregnant, and postpartum. During reproductive rest, the left ovary has numerous follicles compared to the right side. Therefore, uterine fertility is usually higher on the left side. The presence of an embryo in the right uterus suggests that the right ovary is also functional, although this only occurs in larger females. In females at reproductive rest, the wall of the uterus is formed by a mucosal layer (without the trophonemata) that contributes 16.7% to the thickness, while the myometrium accounts for 83.3% of the thickness. The mass-specific volume of the mucosal layer, inner circular, and outer longitudinal smooth muscle sheets tend to increase in the gravid uterus, indicating hypertrophy and hyperplasia of these components. During pregnancy, the trophonemata undergo marked tissue remodeling. Epithelial cells are organized into glandular acini and have apical secretory vesicles; furthermore, peripheral blood vessels proliferate and become dilated. These characteristics demonstrate that the gravid uterus of <i>P. wallacei</i> presents intense uterolactation activity and provides oxygenation to the fetus. Tissue remodeling occurs only in the uterus with the presence of an embryo. During postpartum, females have low body condition factor indicating a high reproductive cost. This study contributes to the knowledge of the reproductive biology of this species and will help us understand the impacts of climate change on the breeding areas of potamotrygonids.</p></div>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142165608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radular Tooth Coating in Members of Dendronotidae and Flabellinidae (Nudibranchia, Gastropoda, Mollusca)","authors":"Wencke Krings,&nbsp;Stanislav N. Gorb,&nbsp;Charlotte Neumann,&nbsp;Heike Wägele","doi":"10.1002/jmor.21773","DOIUrl":"https://doi.org/10.1002/jmor.21773","url":null,"abstract":"<p>Nudibranchs, with their mesmerizing diversity and ecological significance, play crucial roles in marine ecosystems. Central to their feeding prowess is the radula, a chitinous structure with diverse morphologies adapted to prey preferences and feeding strategies. This study focuses on elucidating wear coping mechanisms in radular teeth of carnivorous molluscs, employing <i>Dendronotus lacteus</i> (Dendronotidae) and <i>Flabellina affinis</i> (Flabellinidae) as model species. Both species forage on hydrozoans. Through scanning electron microscopy, confocal laser scanning microscopy, nanoindentation, and energy-dispersive X-ray spectroscopy, the biomechanical and compositional properties of their teeth were analyzed. Notably, tooth coatings, composed of calcium (Ca) or silicon (Si) and high hardness and stiffness compared to the internal tooth structure, with varying mineral contents across tooth regions and ontogenetic zones, were found. The presence of the hard and stiff tooth coatings highlight their role in enhancing wear resistance. The heterogeneities in the autofluorescence patterns related to the distribution of Ca and Si of the coatings. Overall, this study provides into the biomechanical adaptations of nudibranch radular teeth, shedding light on the intricate interplay between tooth structure, elemental composition, and ecological function in marine molluscs.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.21773","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142165606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrigendum to “Bee Morphology: A Skeletomuscular Anatomy of Thyreus (Hymenoptera: Apidae)”","authors":"","doi":"10.1002/jmor.21777","DOIUrl":"https://doi.org/10.1002/jmor.21777","url":null,"abstract":"<p>O. M. Meira, R. G. Beutel, H. Pohl, et al. 2024. “Bee Morphology: A Skeletomuscular Anatomy of <i>Thyreus</i> (Hymenoptera: Apidae).” <i>Journal of Morphology</i>, 285, e21751.</p><p>In published article, the <i>Thyreus</i> used for our study is incorrect, and is likely <i>T. quinquefasciatus</i> (Smith, F., 1879). This error was due to the switching of two specimen records in a flatfile database. Whereas we reported the scanned <i>Thyreus</i> (scan code BB311) as <i>T. albomaculatus</i> (specimen code: USNMENT01900218), the specimen that was the focal subject of our study is in fact <i>T. quinquefasciatus</i> (specimen code: SMFHYM0005662). Unfortunately, the specific epithet “<i>albomaculatus</i>” is used throughout the text; where this occurs, this should be read as “<i>quinquefasciatus</i>.” Fortunately, no conclusions from the study are affected by this mistake as only one species of <i>Thyreus</i> was used for the study. The revised identification is based on: (1) comparison of the voucher specimen of the present study with the type specimen (NHMUK014022685), which is preserved at the Natural History Museum London, and (2) the limited diversity of <i>Thyreus</i> in Madagascar, which is represented by a single known species. We thank Dr. Michael C. Orr for bringing our attention to this mistake.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.21777","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142165263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thecal and Epithecal Ossifications of the Turtle Shell: Ontogenetic And Phylogenetic Aspects","authors":"Gennady Cherepanov,&nbsp;Igor Danilov","doi":"10.1002/jmor.21768","DOIUrl":"10.1002/jmor.21768","url":null,"abstract":"<div>\u0000 \u0000 <p>The problem of the origin of the bony shell in turtles has a two-century history and still has not lost its relevance. First, this concerns the issues of the homology, the sources of formation and the ratio of bones of different nature, that is, thecal and epithecal, in particular. This article analyzes various views on the nature of the shell elements, and proposes their typification, based on modern data on developmental biology. It is proposed that the defining characteristic of the types of shell ossifications is not the level of their anlage in the dermis (thecality or epithecality), but, first of all, the primary sources of their formation: (1) neural crest (nuchal and plastral plates); (2) vertebral and rib periosteum (neural and costal plates); and (3) dermal mesenchyme (peripheral, suprapygal and pygal plates, as well as epithecal elements). In addition, there is complete correspondence between these types of ossifications and the sequence of their appearance in the turtle ontogenesis. The data show fundamental coincidence of the modifications of the ontogenetic development and evolutionary formation of the shell ossifications and are in agreement with a stepwise model for the origin of the turtle body plan. Particular attention is paid to the origin of the epithecal elements of the turtle shell, which correspond to the additional or supernumerary ossifications and seem to have wider distribution among turtles, than previously thought.</p></div>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142120069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphology of the Digestive Tube of the Amazonian Freshwater Stingray Potamotrygon wallacei (Elasmobranchii: Potamotrygonidae): A Stereological Approach","authors":"Rubia Neris Machado,&nbsp;Wallice Paxiúba Duncan","doi":"10.1002/jmor.21771","DOIUrl":"https://doi.org/10.1002/jmor.21771","url":null,"abstract":"<div>\u0000 \u0000 <p>This work aimed to describe and quantify the tissue components of the digestive tube of the neotropical freshwater stingray, <i>Potamotrygon wallacei</i>. For this, conventional histology and stereological methods were used to estimate tissue volume. The volumes of the four fundamental layers and the tissue components in the stomach (cardiac and pyloric) and spiral intestine were also estimated. In the cardiac stomach, the mucosa layer occupies 44.7% of the total volume of the organ wall. The gastric glands are the main components, and these structures alone represent 49.7% of this layer. This large number of gastric glands suggests a high potential for processing food items with a high protein content. The stereological methods were sensitive enough to show a reduction in the volume of the gastric glands from the cardiac region toward the pyloric region. Gastric glands are absent in the pyloric region of the stomach. However, the muscularis becomes thicker towards the pyloric region. The increase in smooth muscle thickness is due to the thickening of the inner muscular layer. This suggests that the role of the pyloric stomach may be related to the mixing of the chyme and assisting its passage to the spiral intestine. In the spiral intestine, data on the volume of the mucosa layer (and epithelial lining) suggest that the spiral valve has a large absorptive area. In several respects, the morphology of the digestive tube of <i>P. wallacei</i> is similar to that of other batoids. However, its slight morphological variations may be related to the habitat specificity of this species.</p></div>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142100238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative morphology of the rhinarium and upper lip in sigmodontine rodents: Refined nomenclature, intertribal variation in a phylogenetic framework, and functional inferences","authors":"Ulyses F. J. Pardiñas,&nbsp;Jorge Brito,&nbsp;Erika Cuellar Soto,&nbsp;Carola Cañón","doi":"10.1002/jmor.21760","DOIUrl":"https://doi.org/10.1002/jmor.21760","url":null,"abstract":"<p>Rodents have received substantial attention in the study of olfaction. However, the rhinarium, the naked part of the nose, which plays an important role in chemical, tactile, and thermal perception, has been relatively overlooked. This study presents a comprehensive analysis of the rhinarium morphology and spatially associated structures (i.e., upper lip, and philtrum) in sigmodontines, a diverse group within the Cricetidae rodents. The research covers 483 specimens representing 145 species, accounting for 74% of genera in the clade, including all 13 recognized tribes, three incertae sedis genera, and the murid representatives <i>Mus musculus</i> and <i>Rattus norvegicus</i>. The inconsistent use of terminology in describing rhinarium traits across the literature poses a challenge for comparative analyzes. To address this issue, a standardized terminology was proposed to characterize the rhinarium. A paired complex protuberance typically with epidermal ridges (i.e., rhinoglyphics), termed here the tubercle of Hill, was identified as a distinctive feature in muroid rhinaria. Comparative assessments among tribes revealed unique sets of features defining each major clade, encompassing variations in hairiness, dorsum nasi complexity, size and positioning of the tubercle of Hill, and other key attributes. Two primary rhinarium configurations were discerned: one shared by Oryzomyalia and Sigmodontini and another specific to Ichthyomyini. The former groups display a ventrally positioned rhinarium prominently featuring the tubercle of Hill and sculptured areola circularis. In contrast, Ichthyomyini exhibit a frontally directed rhinarium characterized by an enlarged dorsum nasi fused to the tubercle of Hill, resulting in a distinctive “cherry” appearance. Convergent rhinarium structures observed in fossorial species, characterized by well-developed plica alaris and hair fringes, are presumed to mitigate potential damage during digging. Conversely, semiaquatic carnivorous sigmodontines showcase an integrated apical structure in their rhinarium, facilitating enhanced somatosensory capabilities crucial for predation activities during diving expeditions.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142099951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Male genitalia, hierarchical homology, and the anatomy of the bullet ant (Paraponera clavata; Hymenoptera, Formicidae)","authors":"Brendon E. Boudinot,&nbsp;Thomas van de Kamp,&nbsp;Patricia Peters,&nbsp;Katja Knöllinger","doi":"10.1002/jmor.21757","DOIUrl":"10.1002/jmor.21757","url":null,"abstract":"<p>The male genitalia of insects are among the most variable, complex, and informative character systems for evolutionary analysis and taxonomic purposes. Because of these general properties, many generations of systematists have struggled to develop a theory of homology and alignment of parts. This struggle continues to the present day, where fundamentally different models and nomenclatures for the male genitalia of Hymenoptera, for example, are applied. Here, we take a multimodal approach to digitalize and comprehensively document the genital skeletomuscular anatomy of the bullet ant (<i>Paraponera clavata</i>; Hymenoptera: Formicidae), including hand dissection, synchrotron radiation microcomputed tomography, microphotography, scanning electron microscopy, confocal laser scanning microscopy, and 3D-printing. Through this work, we generate several new concepts for the structure and form of the male genitalia of Hymenoptera, such as for the endophallic sclerite (=fibula ducti), which we were able to evaluate in detail for the first time for any species. Based on this phenomic anatomical study and comparison with other Holometabola and Hexapoda, we reconsider the homologies of insect genitalia more broadly, and propose a series of clarifications in support of the penis-gonopod theory of male genital identity. Specifically, we use the male genitalia of <i>Paraponera</i> and insects more broadly as an empirical case for hierarchical homology by applying and refining the 5-category classification of serial homologs from DiFrisco et al. (2023) (DLW23) to all of our formalized concepts. Through this, we find that: (1) geometry is a critical attribute to account for in ontology, especially as all individually identifiable attributes are positionally indexed hence can be recognized as homomorphic; (2) the definition of “structure” proposed by DLW23 is difficult to apply, and likely heterogeneous; and (3) formative elements, or spatially defined foldings or in- or evaginations of the epidermis and cuticle, are an important yet overlooked class of homomorphs. We propose a morphogenetic model for male and female insect genitalia, and a model analogous to gene-tree species-tree mappings for the hierarchical homology of male genitalia specifically. For all of the structures evaluated in the present study, we provide 3D-printable models – with and without musculature, and in various states of digital dissection – to facilitate the development of a tactile understanding. Our treatment of the male genitalia of <i>P. clavata</i> serves as a basic template for future phenomic studies of male insect genitalia, which will be substantially improved with the development of automation and collections-based data processing pipelines, that is, collectomics. The Hymenoptera Anatomy Ontology will be a critical resource to include in this effort, and in best practice concepts should be linked.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.21757","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142080549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"First soft body morphological data on the tracemaker of the endolithic bryozoan trace fossil Terebripora ramosa d'Orbigny, 1842","authors":"Sebastian H. Decker,&nbsp;Felipe Aguilera,&nbsp;Ahmed J. Saadi,&nbsp;Thomas Schwaha","doi":"10.1002/jmor.21770","DOIUrl":"10.1002/jmor.21770","url":null,"abstract":"<p>Terebriporidae is one of the four extant endolithic ctenostome bryozoan families, with colonies immersed into carbonate substrates like molluscan shells. This monogeneric family comprises 17 species, with 11 extant and 6 fossil species. It is currently considered closely related to vesicularioid ctenostomes, a group characterized by colonies interconnected by polymorphic stolons and a distinct gizzard as part of their digestive systems. However, confusion persists regarding the correct species identities and affiliations of many terebriporid species, and even the description of the entire family is based solely on a few external features of their boring traces, rendering the family an ichnotaxon (trace fossil). Our molecular analysis does not support a vesicularioid affinity, but corroborate a close relationship to <i>Immergentia</i>, another genus of boring bryozoans. Consequently, this study aims to untangle the systematic confusion surrounding Terebriporidae by examining the tracemaker of the type species of the family, <i>Terebripora ramosa</i> from Chile, and investigating its morphology and histology using modern techniques. The current analysis could not confirm typical vesicularioid characters such as a gizzard or true polymorphic stolons. Instead, all characters point towards a closer relationship to Immergentiidae as suggested by a recent molecular phylogeny. In fact, these two taxa share several characters such as cystid appendages and duplicature bands, and appear closely related, with the only difference being a characteristic vane with tubulets present in the tracemaker of <i>T. ramosa</i>. The sister-group relationship of the tracemaker and the genus <i>Immergentia</i> infers that these borers share a common boring ancestor, but also emphasizes that additional species from the ichnogenus <i>Terebripora</i> need to be studied for more clarity.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.21770","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142055832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The mammary hair of Monodelphis domestica and homology of the mammary pilosebacous unit","authors":"Daniel J. Stadtmauer,&nbsp;Günter P. Wagner","doi":"10.1002/jmor.21769","DOIUrl":"10.1002/jmor.21769","url":null,"abstract":"<p>The unitary mammary gland is a synapomorphy of therian mammals and is thought to have evolved from the pilosebaceous organ in the mammalian stem lineage from which the lactogenic patch of monotremes is also derived. One of the key lines of evidence for the homology of the nipple and the lactogenic patch is that marsupials have retained a transient hair associated with developing mammary glands. However, these structures have not been documented since the early 20th-century drawings of Ernst Bresslau. In this study, we examine the developing mammary organs of <i>Monodelphis domestica</i> and document the presence of mammary hairs in 12-week-old females, as well as their absence after 18 weeks of age. Histochemical staining for cystine confirms the structures as keratinized hairs. Milk ducts of both juvenile and adult nipples show a division between KRT18⁺ luminal epithelium and KRT14⁺ ACTA2⁺ myoepithelium. These patterns match those in eutherians and suggest a conserved ductal morphology and mechanism of milk expulsion. Finally, PTHLH, a peptide hormone which promotes homeotic transformation of hairy skin into hairless nipples in the mouse, was detected in the <i>Monodelphis</i> milk duct during the mammary hair stage, suggesting that the mutual exclusivity of “hairless nipple” and “hair” organ identity is derived in eutherian mammals. These results reveal shared characteristics of the <i>M. domestica</i> nipple with both the eutherian nipple and the pilosebaceous organ, consistent with the evolutionary derivation of the mammary gland from an ancestral hair organ via developmental individualization of pilosebaceous and mammary identities.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.21769","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142073097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Chewing shrews: Examining the morphology and function of the masticatory musculature in Soricidae via diffusible iodine-based contrast-enhanced computed tomography","authors":"Sebastian D. V. Pommerening,&nbsp;Thomas Martin","doi":"10.1002/jmor.21761","DOIUrl":"10.1002/jmor.21761","url":null,"abstract":"<p>Essential for sustaining a high metabolic rate is the efficient fragmentation of food, which is determined by molar morphology and the movement of the jaw. The latter is related to the jaw morphology and the arrangement of the masticatory muscles. Soricid jaw apparatuses are unique among mammals, as the articulation facet on the condylar process is separated into a dorsal and a ventral part, which has often been linked to more differentiated jaw motions. Soricidae also possess a remarkably elongated angular process. However, the precise function of the unique morphology of soricid jaw apparatuses has not been fully understood yet. By digitally reconstructing the masticatory musculature via the diffusible iodine-based contrast-enhanced computed tomography technique, we show how the unique jaw morphology is reflected in the spatial organization as well as the inner architecture and respective fascicle orientations of the muscles. From the lines of action of the <i>m. masseter</i> and the <i>m. pterygoideus internus</i>, both muscles inserting on the lateral and medial side of the angular process, respectively, we infer that the angular process is substantial for roll and yaw rotations of the mandible. The <i>m. masseter</i> is subdivided into four and the <i>m. pterygoideus internus</i> into five subunits, each exhibiting a slightly different line of action and torque. This enables Soricidae to adjust and adapt these rotational movements according to the properties of the ingested food, allowing for more efficient fragmentation. Additionally, those guided rotational motions allow for precise occlusion despite tooth wear. The temporalis is the largest of the adductor muscles and is mainly responsible for exerting the bite force. Overall, the unique jaw bone morphology in conjunction with the complex muscle arrangement may contribute towards a more efficient energy gain and the maintenance of a high metabolic rate, which is crucial for small-bodied mammals such as shrews.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"285 9","pages":""},"PeriodicalIF":1.5,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.21761","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142046827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}