Journal of Morphology最新文献

{"title":"Structural Organization of the Penis in the South American Plains Vizcacha (Lagostomus maximus), a Caviomorph Rodent.","authors":"Mariela Giacchino, Pablo I F Inserra, Juan A Claver, María C Gariboldi, Fernando D Lange, Sergio R Ferraris, Noelia P Leopardo, Alfredo D Vitullo","doi":"10.1002/jmor.70129","DOIUrl":"https://doi.org/10.1002/jmor.70129","url":null,"abstract":"<p><p>The male genital morphology of the plains vizcacha (Lagostomus maximus) remains poorly characterized despite the species' distinctive reproductive biology and its phylogenetic position within Caviomorpha. In this study, we describe the gross anatomy, histology, and ultrastructure of the penis of L. maximus using light microscopy and scanning electron microscopy. The genitalia of the vizcacha shares several features with other caviomorph rodents, including the absence of a pendulous scrotum, subcutaneous inguinal testes, and a retracted inverted S-shaped penile configuration. Notably, we identify a previously undescribed narrow stylet-like distal process supported by hyaline cartilage and bearing caudally oriented surface spine-like projections, representing a novel morphological specialization among caviomorph rodents. These distal specializations may influence copulatory mechanics by enhancing mechanical stimulation of the female reproductive tract. When considered alongside recent evidence suggesting a mixed ovulatory strategy in L. maximus, including a seminal plasma-induced ovulatory process, these findings raise the possibility that penile morphology contributes synergistically to ovulation induction. Our results expand current knowledge of genital diversity in caviomorph rodents and provide a morphological framework for future functional and evolutionary investigations.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 5","pages":"e70129"},"PeriodicalIF":1.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147839239","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":"Ovary Organization and a Putative Germ Plasm in Tubuliferan and Terebrantian Thrips (Thysanoptera).","authors":"Waclaw Tworzydlo, Magda Sochaczewska, Szczepan M Bilinski","doi":"10.1002/jmor.70127","DOIUrl":"https://doi.org/10.1002/jmor.70127","url":null,"abstract":"<p><p>Comparison of the detailed morphology of ovaries allows for an evolutionary conclusion in insects. The current study characterized the ovary/ovariole organization in both thysanopteran subtaxa (Terebrantia and Tubulifera) and confirmed the presence of a (putative) germ plasm in the oocytes. Using transmission and scanning electron microscopy as well as histological methods, we show that the morphology of ovaries in the studied terebrantians and tubuliferans differs in the organization of the anterior ovary/ovariole region, that is, the germaria and terminal filaments. Whereas in tubuliferan, Haplothrips leucanthemi, the terminal filaments and germaria of all four ovarioles constituting a given ovary form single common structures (a common terminal filament and a germarial chamber, respectively), in the analyzed terebrantians (Frankliniella occidentalis and Thrips sp.), they remain individual, as in all other insect orders. Thus, the fusion of the anterior ovariole parts is interpreted as an apomorphy characteristic of tubuliferan thrips only. In contrast, the course of oogenesis in terebrantians and tubuliferans is rather similar and reveals one prominent feature: the presence of a distinct nuage layer encompassing oocyte nuclei. We also show that after reinitiation of the first meiotic division in representatives of both thysanopteran subgroups, a small irregular region of cytoplasm arises at the posterior oocyte extremity. We suggest that this region is homologous to the germ plasm of holometabolous insects.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 5","pages":"e70127"},"PeriodicalIF":1.4,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147839187","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":"Testing the Limits of Morphology: A Comprehensive Morphometric Study of the Sister Lineages Lasiocyano Galleti-Lima, Hamilton, Borges and Guadanucci, 2023 and Lasiodora C. L. Koch, 1850 (Theraphosidae, Mygalomorphae)","authors":"Analice G. Marquezin-Gomes,&nbsp;Arthur Galleti-Lima,&nbsp;Millke J. A. Morales,&nbsp;José Paulo L. Guadanucci","doi":"10.1002/jmor.70123","DOIUrl":"10.1002/jmor.70123","url":null,"abstract":"<p>Morphological conservatism and homoplasy pose significant challenges for the systematics of mygalomorph spiders, limiting the number of reliable morphological characters available for species identification, particularly in Theraphosidae. Closely related taxa frequently display high phenotypic similarity, which limits the resolution of morphology-based approaches. In this study, we conducted the most extensive morphometric analysis to date within Theraphosidae, with the objective of explicitly testing how much morphological information is retained within the <i>Lasiocyano sazimai</i> and <i>Lasiodora</i> lineage. We applied a morphometric framework combining linear morphometry and geometric morphometry, including multivariate statistics, discriminant analyses, and cross-validation, to evaluate interspecific differentiation in this group. Although some analyses recovered statistically significant differences among taxa, extensive morphological overlap, high intraspecific variation, and pronounced overfitting in cross-validated classifications consistently reduced the discriminatory power of the methods. As a result, none of the approaches provided reliable diagnostic separation between <i>Lasiocyano sazimai</i> and <i>Lasiodora</i> species. Our results indicate that morphology alone reaches clear limits of resolution within this lineage. The only characters that remained consistently informative for distinguishing the genera were the presence of stridulatory setae in <i>Lasiodora</i> and the distinctive blue-purplish setae of <i>Lasiocyano</i>. By explicitly testing the limits of morphometric and morphological inference in a morphologically conservative group, this study helps clarify the actual scope and limitations of morphology-based systematics in Theraphosidae.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 4","pages":""},"PeriodicalIF":1.4,"publicationDate":"2026-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jmor.70123","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147668577","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":"Adaptation in the Avian Middle Ear-The Columellar Annular Ligament in Aquatic and Diving Birds.","authors":"John Peacock","doi":"10.1002/jmor.70124","DOIUrl":"10.1002/jmor.70124","url":null,"abstract":"<p><p>The effective detection of environmental vibrations such as sound waves depends on the transmission of tympanic membrane motion through the middle ear to the inner ear hair cells. In birds, the bony element of the middle ear is the columella; its distal end joins the cartilaginous extracolumella and tympanic membrane, while its basal expansion (the footplate) interfaces with inner ear fluid at the oval window, where it is held in place by the stapedial (columellar) annular ligament. Variation in footplate and oval window geometry can alter the annular ligament's size and shape, thereby influencing middle ear mechanics. Previous studies have noted relatively small footplates in aquatic birds as compared to their terrestrial relatives, and suggested that the adaptive significance of these may relate to their influence on the relative size of the annular ligament. Here, I examine a taxonomically and ecologically broad sample of bird species to test the hypothesis that aquatic lineages have convergently evolved proportionally larger annular ligaments. Results show larger ligaments are characteristic of aquatic, and particularly diving species, while narrower ligaments occur in high-frequency specialists. These patterns are polyphyletic and, alongside their strong ecological associations, indicate repeated functional adaptation of the middle ear. Larger ligaments are consistent with reduced system stiffness and enhanced low-frequency transmission, a hypothesis which is plausible for pelagic seabirds. In contrast, the extreme ligament enlargement in diving taxa is unlikely to be related to hearing, and instead may play a role in protection from barotrauma.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 4","pages":"e70124"},"PeriodicalIF":1.4,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13094323/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147723097","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":"Post-Oviposition Embryonic Staging Scheme for the Delicate Skink, Lampropholis delicata.","authors":"Jinglin Wen, Oliver William Griffith","doi":"10.1002/jmor.70126","DOIUrl":"https://doi.org/10.1002/jmor.70126","url":null,"abstract":"<p><p>Skinks are an important model in evolutionary research because they have evolved a suite of features of interest in vertebrate biology, from limb loss to viviparity. Furthermore, they have been a model for understanding ecophysiology and behavior, particularly the impact of climate change on ectothermic animals. Despite studies on the impact of developmental processes on skink biology, researchers have relied on embryonic staging schemes from species that diverged from skinks over 170 million years ago. We describe Lampropholis delicata as a model and establish the first embryonic development staging scheme for a skink. We detail the morphology of post-oviposition embryos at different stages and compare them with other reptile lineages. Embryos across 14 stages are described based on the development of limbs, eyes, brain, branchial arches, frontonasal prominence, otic vesicle, scales, and pigmentation. We distinguish early stages via the shape of the otic vesicle, and find the pineal organ is present earlier than in Zootoca and Anolis embryos. This skink embryonic staging scheme serves as a valuable tool for ongoing research into skink biology and can be used as a benchmark for genetic, evolutionary, and physiological research.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 4","pages":"e70126"},"PeriodicalIF":1.4,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13111900/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147774176","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":"Guess Who: Delineating Post-Metamorphic Amphibian Life Stages and Sexes Using a Standardised Visible Approach.","authors":"John Gould, Loren Louise Fardell, Alex Callen, Colin McHenry","doi":"10.1002/jmor.70125","DOIUrl":"https://doi.org/10.1002/jmor.70125","url":null,"abstract":"<p><p>Among animals, adulthood is synonymous with sexual maturity and often defined by the capacity of an individual to store and/or use functional gametes. Yet, under field conditions, where evidence of gametes cannot always be easily ascertained, researchers rely on other cues of maturity, such as size and sex-based traits, which also enable for the differentiation of the sexes. In this study, we used a multi-season data set to help define adulthood for the green and golden bell frog, Randoidea [Litoria] aurea males and females that improves upon past methods using externally visible attributes. Our decision-making approach is nuanced as it considers both the presence and level of expression of visibly detectable sex attributes, namely nuptial pad colouration and gravidity level, with expression levels of these traits also used to define minimum size thresholds of maturity for each sex independently. This protocol allows individuals with high expressions of sex-based traits of maturity to be assigned as adults even if they are below minimum size thresholds, thus accounting for precocious development, and for individuals above these thresholds to be assigned as adults regardless of trait expression, thus accounting for temporal variability in these traits within the adult life stage that are related to hormone cycles. We believe this decision-making pipeline can be applied to other amphibians by adjusting trait thresholds to species- or population-specific specifications.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 4","pages":"e70125"},"PeriodicalIF":1.4,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13111902/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147774208","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 Dermal Skeleton of Stem-Actinopterygian Moythomasia durgaringa and Its Implications for the Nature of the Ancestral Osteichthyan","authors":"Xianren Shan,&nbsp;Edine Pape,&nbsp;Joseph N. Keating,&nbsp;Martin Rücklin,&nbsp;Davide Pisani,&nbsp;Philip C. J. Donoghue","doi":"10.1002/jmor.70120","DOIUrl":"10.1002/jmor.70120","url":null,"abstract":"<p>The dermal skeleton is the most primitive component of the vertebrate mineralized skeleton, and features of its structure and development are key to resolving the evolutionary relationships of early vertebrates and bony fishes. In particular, the nature and phylogenetic distribution of cosmine, a dermal complex of hard tissue and vascular systems, have been the focus of debate over the nature of the ancestral osteichthyan and the timing of actinopterygian–sarcopterygian divergence. In large part, this controversy occurs because of a paucity of knowledge of the nature of the dermal skeleton in stem-actinopterygians. Here, we describe the dermal skeletal histology of stem-actinopterygian <i>Moythomasia durgaringa</i> using Scanning Electron Microscopy and Synchrotron Radiation X-ray Tomographic Microscopy with a reconstruction of its topological variation and development. The dermal skeleton of <i>Moythomasia</i> consists of a superficial layer of stacked odontodes that undergo extensive odontogenic resorption and a basal layer of lamellar bone. A middle vascular bone layer is variably developed in cranial dermal bones but is completely absent in postcranial dermal elements. Additional histological variation among dermal elements includes the number of odontode generations, odontode growth patterns and the relative thickness of osteogenic and odontogenic tissues. A comparison of the histological condition in <i>Moythomasia</i> and stem- and early crown-osteichthyans reveals numerous similarities, including the presence of a three-layered dermal skeleton, stacked odontodes and odontogenic resorption. Phylogenetic comparative analyses on early jawed vertebrates indicate that features associated with cosmine evolved in groups outside Rhipidistia, whereas true cosmine remains restricted to this group comprising Dipnomorpha and Tetrapodomorpha. The concept of cosmine is phylogenetically uninformative because of the multiplicity of its definitions and usage. These findings suggest that fossil taxa currently classified as stem-sarcopterygians may instead be stem-actinopterygians, or even stem-osteichthyans, with implications for the nature of the ancestral bony fish and the timing of osteichthyan diversification.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 3","pages":""},"PeriodicalIF":1.4,"publicationDate":"2026-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13003200/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147486407","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":"Gonadal Development in Larvae of the Paedomorphic Ambystoma mexicanum (Amphibia: Urodela)","authors":"Jessica Lucía Sánchez-Ortiz,&nbsp;Eva Mendoza-Cruz,&nbsp;Maricela Villagrán-SantaCruz","doi":"10.1002/jmor.70118","DOIUrl":"10.1002/jmor.70118","url":null,"abstract":"<p>The axolotl (<i>Ambystoma mexicanum</i>) is an endemic amphibian of the order Urodela, which has the ability to reproduce while retaining its larval characteristics. The primary objective of this study was to outline the stages of gonadal development leading to sexual maturity. Gonads from both male and female larvae, aged 4–12 months, were histologically processed and characterized according to their developmental stage. Histological analysis of the ovaries revealed that larvae aged 4–8 months were immature. At 9 and 10 months, the oocytes showed early signs of maturity, characterized by an increase in volume, yolk accumulation, and the presence of cortical pigment at one cellular pole. At 12 months, mature oocytes are predominant, as indicated by a significant increase in size and the migration of the germinal vesicle toward the pigmented animal pole. Male larvae have immature gonads at 4–5 months of age. By 7 to 8 months, the beginning of the spermatogenic process is evident, regionalizing the testis in a cephalocaudal and lateromedial direction. In 9-month-old males, the spermiation process begins, becoming dominant by 10 months. In 12-month-old males, a clear regionalization of the testis is evident; while spermiation continues in the caudal and medial regions, spermatogenesis restarts in the more cephalic and dorsal areas. This early and accelerated gametogenesis in males signifies a gonadal maturity that occurs sooner than in females, which reflects a process of heterochrony. The relatively early attainment of sexual maturity for both sexes, a direct result of their paedomorphic condition, is an advantageous adaptive strategy.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 3","pages":""},"PeriodicalIF":1.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12989787/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147463559","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":"Effects of Increased Distal Limb Mass on Stability During Arboreal Locomotion in the Laboratory Rat (Rattus norvegicus)","authors":"Andrew R. Lammers,&nbsp;Grace L. Schepelmann,&nbsp;Olivia Safady,&nbsp;Benjamin N. Lammers","doi":"10.1002/jmor.70119","DOIUrl":"10.1002/jmor.70119","url":null,"abstract":"<p>Traveling on arboreal substrates requires behavioral and morphological adaptations to reduce the likelihood of falls. Many arboreal specialists have greater distal limb mass compared with closely related terrestrial taxa. In this study, we test the hypothesis that augmenting the distal limb mass will increase stability during locomotion, allowing a quadrupedal mammal to rely less on static methods of stability when moving on a cylindrical support. Thus, we predict that weighted bracelets will result in less crouching, greater vertical oscillation, lower duty factor, and higher limb phase. We trained four laboratory rats to walk on a “rope-mill,” the arboreal equivalent of a treadmill. We marked the fur over the glenohumeral joint and the greater trochanter, and then encouraged the animals to run either unmodified, wearing sham bracelets, or weighted bracelets (1.8 g each) on the wrists and ankles. From two video cameras, we extracted sequences of 15 strides for each experimental setup and digitized the right shoulder, hand, hip, and foot. When the rats walked with weighted distal limbs, the limb phase was lower, but duty factor was unchanged. The shoulder height was somewhat greater, whereas vertical accelerations were lower. The hip height and vertical accelerations were unchanged. Each individual adjusted to increased distal limb mass in a variety of ways. We conclude that adding mass to the distal parts of limbs did not enhance stability. We suggest that neuromuscular and developmental differences among individuals contribute to the variability among animals in responding to wearing weighted bracelets.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 3","pages":""},"PeriodicalIF":1.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12989785/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147463557","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":"Osteology of the Feeding Apparatus of Chilean Flamingo Phoenicopterus chilensis (Aves: Phoenicopteridae)","authors":"Oscar Aldana Ardila,&nbsp;Caio J. Carlos","doi":"10.1002/jmor.70116","DOIUrl":"10.1002/jmor.70116","url":null,"abstract":"<p>Flamingos (Phoenicopteridae) feed using a uniquely adapted bill that extracts small particles from the water and sediments. This study provides a detailed osteological description of the skull of the Chilean Flamingo (<i>Phoenicopterus chilensis</i>), with particular emphasis on feeding-related features. The skull exhibits a broad, flattened frontal region that articulates with an elongated upper jaw, which is deflected ventrally at approximately 45° and aligns seamlessly with the laterorostrally curved mandible, forming a configuration well suited for filter feeding. The mandible exhibits a low mechanical advantage, indicating an adaptation for rapid and repetitive movements rather than forceful biting. Jaw muscle attachment sites, including the fossa subtemporalis, fossa temporalis, and fossa ventralis palatini, are reduced, suggesting the presence of relatively small muscles that favor speed and precision.</p>","PeriodicalId":16528,"journal":{"name":"Journal of Morphology","volume":"287 3","pages":""},"PeriodicalIF":1.4,"publicationDate":"2026-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12963700/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147365540","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}