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Journal of Morphology
Alan R. Liss
Journal of Morphology

Alan R. Liss

0362-2525

Journal of Morphology/Journal Journal of MorphologySCIISTPAHCI
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    Morphology of ctenostome bryozoans: 5. Sundanella, with description of a new species from the Western Atlantic and the Multiporata concept

    Schwaha, ThomasWinston, Judith E.Gordon, Dennis P.
    24页
    查看更多>>摘要：Ctenostome bryozoans are a small group of gymnolaemates that comprise only a few hundred described species. Soft-tissue morphology remains the most important source for analysing morphological characters and inferring relationships within this clade. The current study focuses on the genus Sundanella, for which morphological data is scarce to almost absent. We studied two species of the genus, including one new to science, using histology and three-dimensional reconstruction techniques and confocal laser scanning microscopy. Sundanella generally has a thick, sometimes arborescent cuticle and multiporous interzooidal pore plates. The lophophore is bilateral with an oral rejection tract and generally has 30 or 31 tentacles in both species. The digestive tract shows a large cardia in S. floridensis sp. nov. and an extremely elongated intestine in Sundanella sibogae. Both terminate via a vestibular anus. Only parietodiaphragmatic muscles are present and four to six duplicature bands. Both species show a large broad frontal duplicature band further splitting into four individual bands. The collar is vestibular. Sundanella sibogae shows highly vacuolated cells at the diaphragm, whereas S. floridensis sp. nov. has unique glandular pouches at the diaphragmal area of the tentacle sheath. Such apertural glands have never been encountered in other ctenostomes. Both species of Sundanella are brooders that brood embryos either in the vestibular or cystid wall. Taken together, the current analysis shows numerous characteristics that refute an assignment of Sundanella to victorellid ctenostomes, which only show superficial resemblance, but differ substantially in most of their soft-body morphological traits. Instead, a close relationship with other multiporate ctenostomes is evident and the families Pherusellidae, Flustrellidrae and Sundanellidae should be summarized as clade 'Multiporata' in the future.
      原文链接:
    • NSTL
    • Wiley

    The mouthparts of the adult dragonfly Anax imperator (Insecta: Odonata), functional morphology and feeding kinematics

    Josten, BenediktGorb, Stanislav N.Buesse, Sebastian
    19页
    查看更多>>摘要：Insects evolved differently specialized mouthparts. We study the mouthparts of adult Anax imperator, one of the largest odonates found in Central Europe. Like all adult dragonflies, A. imperator possesses carnivorous-type of biting-chewing mouthparts. To gain insights into the feeding process, behavior and kinematics, living specimens were filmed during feeding using synchronized high-speed videography. Additionally, the maximum angles of movement were measured using a measuring microscope and combined with data from micro-computed tomography. The resulting visualizations of the 3D-geometry of each mouthpart were used to study their anatomy and complement the existing descriptive knowledge of muscles in A. imperator to date. Furthermore, confocal laser scanning microscopy-projections allow for estimation of differences in the material composition of the mouthparts' cuticle. By combining all methods, we analyze possible functions and underlying biomechanics of each mouthpart. We also analyzed the concerted movements of the mouthparts; unique behavior of the mouthparts during feeding is active participation by the labrum and distinct movement by the maxillary laciniae. We aim to elucidate the complex movements of the mouthparts and their functioning by combining detailed information on (1) in vivo movement behavior (supplemented with physiological angle approximations), (2) movement ability provided by morphology (morphological movement angles), (3) 3D-anatomy, and (4) cuticle composition estimates.
      原文链接:
    • NSTL
    • Wiley

    No news from old drawings? Stomach anatomy in muroid rodents in relation to body size and ecology

    Martin, Louise F.Imper, CorinaMeloro, CarloDuque-Correa, Maria J....
    10页
    查看更多>>摘要：Muroid rodents mostly have a complex stomach: one part is lined with a cornified (nonglandular) epithelium, referred to as a "forestomach", whereas the rest is lined with glandular epithelium. Numerous functions for the forestomach have been proposed. We collated a catalog of anatomical depictions of the stomach of 174 muroid species from which the respective nonglandular and glandular areas could be digitally measured, yielding a "stomach ratio" (nonglandular:glandular area) as a scale-independent variable. Stomach ratios ranged from 0.13 to 20.15, and the coefficient of intraspecific variation if more than one picture was available for a species averaged at 29.7% (+/- 21.5). We tested relationships of the ratio with body mass and various anatomical and ecological variables, including diet. There was a consistent phylogenetic signal, suggesting that closely related species share a similar anatomy. Apart from classifying stomachs into hemiglandular and discoglandular, no anatomical or ecological measure showed a consistent relationship to the stomach ratio. In particular, irrespective of statistical method or the source of dietary information, dietary proxies did not significantly correlate with the stomach ratio, except for a trend towards significance for invertivory (insectivory). Yet, even this relationship was not convincing: whereas highly insectivorous species had high but no low stomach ratios, herbivorous species had both low and high stomach ratios. Thus, the statistical effect is not due to a systematic increase in the relative forestomach size with invertivory. The most plausible hypotheses so far associate the muroid forestomach and its microbiome with a generic protective role against microbial or fungal toxins and diseases, without evident correlates of a peculiar need for this function under specific ecological conditions. Yet, this function remains to be confirmed. While providing a catalog of published depictions and hypotheses, this study highlights that the function of the muroid rodent forestomach remains enigmatic to date.
      原文链接:
    • NSTL
    • Wiley

    Ontogeny of the trigeminal system and associated structures in Alligator mississippiensis

    Lessner, Emily J.Elsey, Ruth M.Holliday, Casey M.
    21页
    查看更多>>摘要：From the appearance of the vertebrate head, the trigeminal system has played a role in behavioral and ecological adaptation. The trigeminal nerve is the primary cranial somatosensory nerve, also innervating the jaw muscles. In crocodylians, the trigeminal nerve plays a role in modulating the high bite force and unique integumentary sensation. In association with these behaviors, crocodylians are known for large trigeminal nerves, a high volume of trigeminal-innervated musculature, and densely packed, specialized sensory receptors. These innovations also occurred in concert with a restructuring of the lateral braincase wall. These morphologies have previously been investigated in phylogenetic and evolutionary contexts, but an ontogenetic, whole-system investigation of trigeminal tissue and associated musculature, cartilage, and bone is lacking, as is an understanding of developmental timing of morphologies significant to hypotheses of homology. Here, we use contrast-enhanced computed tomography imaging to provide description and analysis of the trigeminal system in an ontogenetic series of Alligator mississippiensis from embryonic to adult form. We explore growth rates and allometric relationships of structures and discuss the significance to hypotheses of homology. We find a high growth rate and allometric trajectory of the trigeminal nerve in comparison to other cranial nerves, likely associated with the large volume of trigeminal musculature and high densities of sensory receptors. We identify a similar trend in the pterygoideus dorsalis muscle, the highest contributor to bite force. We narrow ontogenetic timing of features related to the trigeminal topological paradigm and the undeveloped epipterygoid. Overall, we provide a basis for understanding trigeminal development in crocodylians, which upon comparison across reptiles will reveal ontogenetic origins of morphological variation.
      原文链接:
    • NSTL
    • Wiley

    Paleobiological inferences on middle Eocene native ungulates from South America: Functional morphological analysis of Notostylops and Notopithecus

    Vera, BarbaraMedina-Gonzalez, PaulMoreno, Karen
    26页
    查看更多>>摘要：Eocene early-diverging representatives of South American extinct notungulates are traditionally considered to have been "generalists" and "non-specialized" in terms of the appendicular skeleton and locomotor behavior, as is the case with the notostylopid Notostylops, a middle Eocene iconic taxon from Patagonia (Argentina). However, they are mainly known from dental remains, and associated cranial and postcranial elements are scarce. The discovery of a nearly complete specimen attributed to N. murinus allows us to: (1) increase the knowledge of the anatomy of its appendicular skeleton; (2) identify isolated bones from several collections and suggest different taxonomic interpretations for published specimens; (3) perform a biomechanical and functional study using functional morphological analysis to infer its paleoecological attributes (e.g. posture, locomotor habit, estimated speed, and body mass); and (4) establish morphofunctional comparisons, based on possible functional ranges, with other extinct early-diverging notoungulates from the middle Eocene, such as the Notopithecid Notopithecus. Our evidence suggests that Notostylops was a medium-sized mammal (8.5-20 kg), which could achieve a dynamic digitigrade posture that allowed a scansorial secondary locomotor habit and a speed of up to 50 km/h. However, Notopithecus was a small-sized mammal (0.6-1.4 kg) with a plantigrade posture both in a static and dynamic context, terrestrial habits, and a speed of up to 35 km/h. Therefore, we conclude that these Eocene notoungulates show different locomotor capabilities, which can be associated with early niche diversifications, clearly contrasting with the "all-generalists" paradigmatic view.
      原文链接:
    • NSTL
    • Wiley

    The forelimbs of Alvarezsauroidea (Dinosauria: Theropoda): Insight from evolutionary teratology

    Guinard, Geoffrey
    16页
    查看更多>>摘要：Alvarezsauroidea (Tetanurae) are nonavian theropod dinosaurs whose forelimb evolution is characterised by the overdevelopment of digit I, at the expense of the other two digits, complemented by a drastic forelimb shortening in derived species (Parvicursorinae). These variations are recognised as evolutionary developmental anomalies. Evolutionary teratology hence leads to a double diagnosis with (1) macrodactyly of digit I and microdactyly of digits II and III, plus (2) anterior micromelia. The teratological macrodactyly/microdactyly coupling evolved first. Developmental mechanisms disturbing limb proportion are thought to be convergent with those of other Tetanurae (Tyrannosauridae, Carcharodontosauridae). As for the manual anomalies, both are specific to Alvarezsauroidea (macrodactyly/microdactyly) and inherited (digit loss/reduction). While considering the frame-shift theory, posterior digits develop before the most anterior ones. There would therefore be a decrease in the area devoted to digits II (condensation 3) and III (condensation 4), in connection with the Shh signalling pathway, interacting with other molecular players such as the GLI3 protein and the Hox system. Developmental independence of digit I (condensation 2) would contribute to generating a particular morphology. Macrodactyly would be linked to a variation in Hoxd-13, impacting Gli3 activity, and increasing cell proliferation. The loss/reduction of digital ray/phalanges (digits II and III), would be associated with Shh activity, a mechanism inherited from the theropodan ancestry. The macrodactyly/microdactyly coupling, and then anterior micromelia, fundamentally changed the forelimb mechanical function, compared to the 'classical' grasping structure of basal representatives and other theropods. The distal ossification of the macrodactylian digit has been identified as physiological, implying the use of the structure. However, the debate on a particular 'adaptive' use is pointless as the ecology of an organism is interactively complex, being both at the scale of the individual and dependent on circumstances. Other anatomical features also allow for compensation and different predation (cursorial hindlimbs).
      原文链接:
    • NSTL
    • Wiley

    Branching patterns of the vascularization and innervation of the primate forelimb

    Vanhoof, Marie J. M.Wagemans, Colettevan Leeuwen, TimoVereecke, Evie E....
    12页
    查看更多>>摘要：In this study, we investigate the branching patterns of the vascularization and innervation of the primate forelimb by performing detailed dissections of five unembalmed nonhuman primate specimens belonging to five different species, that is, rhesus macaque (Macaca mulatta), white-handed gibbon (Hylobates lar), Western gorilla (Gorilla gorilla), chimpanzee (Pan troglodytes), and bonobo (Pan paniscus). Results are compared with five embalmed human specimens (Homo sapiens), and anatomical data of previous studies on nonhuman primates are also included to provide a broader comparative framework. The results show that the overall configuration of the forelimb blood vessels and nerves of the different primate species is similar, although some apparent interspecific differences are found. In all nonhuman primates, in contrast to humans, the superficial vena basilica is absent. Moreover, in gorilla, chimpanzee, and bonobo, the superficial vena cephalica is confined to the forearm. In humans, both an arteria interossea anterior and posterior are present, while in nonhuman primates, only an arteria interossea anterior is present, which migrates to the posterior side at the level of the musculus pronator quadratus. For the innervation, the nervus (n.) medianus and n. ulnaris connect in the forearm of the gorilla and macaque. In the gibbon, the brachial plexus shows some differences in the branching pattern at the fasciculus level compared to the other primates. We conclude that the forelimb innervation branching pattern shows some minor differences between the nonhuman primate species, compared to higher plasticity in the vascularization. However, the exact functional implications of these differences still remain unclear. Therefore, more research on a broader range of primate species and sampling more specimens for each taxon are needed.
      原文链接:
    • NSTL
    • Wiley