Journal of Morphology最新文献

The feeding organ of cephalopod species, the beak, can be used to reveal important ecological information. In this study, geometric morphometric approaches were employed to investigate the phylogenetic relevance and classification effect of beak lateral profile shape. The two-dimensional beak morphologies of 1164 pairs of 24 species from 13 genera and five families were constructed, and their evolutionary relationships and taxonomic status were confirmed using geometric morphometrics and molecular biology approaches. We also assessed the phylogenetic signals of beak shape. The analysis results show shape variation in the beak mainly in the rostrum, hood, and lateral wall. The overall shape parameters (all PCs) of the upper and lower beak are more useful for species identification. The shapes of the upper and lower beak show a strong phylogenetic signal, and the phenogram based on the beak shape basically reflected the families’ taxonomic positions. We also hypothesized that the shape variation in the beaks of cephalopods may be ascribed to genetic and environmental differences. In summary, beaks are a reliable material for the classification of cephalopod species. Geometric morphometric approaches are a powerful tool to reveal the identification, phylogenetic relevance and phenotypic diversity of beak shape in cephalopods.

Horned frogs, members of the Ceratophryidae family, encompass a group of anurans varying in size and behavior, yet unified by morphological and behavioral traits enabling them to adopt a megalophagous diet (i.e., large prey feeding). Although the group has been the focus of numerous studies, our understanding of its feeding behavior remains limited. In this study, we characterize the feeding mechanism in five species representing the three extant genera of ceratophryid anurans, both in terrestrial and aquatic environments. We also explore the ability of Chacophrys pierottii to adjust feeding behavior based on prey type. Our findings show that all species are capable of wide mouth opening, displaying an asymmetric feeding cycle. While tongue usage is the primary method for capturing prey on land, ceratophryids may use their forelimbs to manipulate prey into their mouths, exhibiting different behavioral patterns. C. pierottii shows modulation of its feeding kinematics and is also capable of some modulation of its feeding in response to prey properties.

The early period of ontogeny is key to understanding the patterns of body plan formation in birds. Most studies of avian development have focused on the development of individual avian characters, leaving their developmental integration understudied. We explored the dynamics and integration of relative percentage increments in body mass, lengths of head, skeletal elements of wing and leg, and primary flight feathers in the embryonic and postnatal development of the Rook (Corvus frugilegus). The relative percentage increments were calculated according to Brody's equation. Groups of similar growing traits (modules) were determined using hierarchical cluster analysis, and the degree of correlation between modules was estimated by PLS analysis. The embryonic and postnatal periods demonstrate significant consistency both in the dynamics of changes in relative percentage increments of studied traits as well as in the clustering of individual modules. The modules mainly include the body mass and head length, as well as the elements that form the fore- and hind limbs. Differences were revealed in the combination of modules into clusters in embryonic and postnatal periods. Hind limb elements clustered together with wing elements in the embryonic period but with body mass and the head in the postnatal period. The strongest modularity was noted for the leg in embryogenesis, and for the wing in postnatal development. The forelimb and especially the primary feathers had more distinctive growth patterns. We suggest the changes in the degree of integration between locomotor modules in ontogenesis are connected with the earlier functioning of the legs in the postnatal period and with the preparation of the wings for functioning after a chick leaves the nest.

Brachiopods have the most complex lophophore in comparison with other lophophorates, i.e., phoronids and bryozoans. However, at early ontogenetic stages, brachiopods have a lophophore of simple morphology, which consists of the oral tentacles. Data on the ultrastructure of the oral tentacles is mostly missing. Nonetheless, it has recently been suggested that the structure of oral tentacles is ancestral for all lophophorates in general, and for brachiopods in particular. The fine structure of the oral tentacles in the brachiopod Hemithiris psittacea is studied using light microscopy, transmission and scanning electron microscopy, cytochemistry and confocal laser scanning microscopy. The oral tentacles have a round shape in transverse section, and four ciliary zones, i.e., one frontal, two lateral, and one abfrontal. Latero-frontal sensory cells occur among the frontal epithelium. Four basiepithelial nerves in the ciliary epithelium are colocalized with ciliary zones. Lophophores of simple morphology in phoronids and brachiopods are characterized by non-specified round forms of tentacles. In phoronids and bryozoans, tentacles have additional latero-frontal ciliary zones that function as a sieve during filtration. In most brachiopods, lateral cilia are involved in the capture of food particles, whereas latero-frontal cells are retained in the frontal zone as sensory elements. The oral tentacles of H. psittacea contain a coelomic canal and have distinct frontal and abfrontal longitudinal muscles, which are separated from each other by peritoneal cells. A similar structure of tentacle muscles occurs in all bryozoans, whereas in phoronids, the frontal and abfrontal tentacle muscles are not separated by peritoneal cells. We suggest that the lophophorates' ancestor had tentacles, which were similar to the tentacles of some phoronids with lophophore of simple morphology. We also assume that the structure of the oral tentacles is ancestral for all brachiopods and the specialization of brachiopod tentacles correlates with the appearance of the double row of tentacles.

The musculature is one of the best studied organ systems in brachiopods, being approachable not only by dissecting recent species of brachiopods, but also by exploring muscle scars in fossil material. In the present study, the muscular anatomy of Novocrania anomala is studied using 3D reconstructions based on microcomputed tomography. Muscles of N. anomala may be subdivided into two groups: those related to movements of the lophophore, and those connected to movements of shell valves. Muscles, their morphology and possible functions, such as brachial protractors, elevators, and retractors, as well as anterior adductors, are described and discussed. We also provide the discussion of craniid muscle terminology, consider the valve-opening mechanism. The investigation of muscle scars on dorsal valves supports the conclusion that the shape of muscle scars should be used for description and distinction of recent and extinct species only when visible distinctness cannot be explained by substrate differences. This study, which is aimed at improving our understanding the anatomy and functioning of muscles in craniids, will be useful not only for zoologists, but also for paleontologists.

Among marsupials, the endangered numbat (Myrmecobius fasciatus) is the only obligate myrmecophage with a diet comprised strictly of termites. Like many other specialised myrmecophagous mammals, numbats have a gracile and highly specialised skull morphology with an elongated rostrum and small braincase. Myrmecobiidae is one of four taxonomic families within the Australasian marsupial order Dasyuromorphia, and to date, the muscular anatomy of any member of this group is relatively poorly known. We utilised microdissection and contrast-enhanced microcomputed tomography scanning to provide the first comprehensive qualitative and quantitative descriptions of jaw muscle anatomy in numbats and quolls (Dasuyrus species). The arrangement of the jaw muscles across these species was conservative, both in gross anatomy and muscle proportions, corresponding to a ‘generalised’ mammalian pattern. In contrast to Dasyurus, the jaw muscles of the numbat were greatly reduced. Many aspects of the muscle anatomy of the numbat were similar to patterns reported in other myrmecophagous species, particularly a greatly reduced temporalis muscle. Unusually, the digastric muscle in the numbat was comprised of a single, large anterior belly while the posterior belly was absent. We propose that the enlarged anterior belly of the digastric may be linked to jaw stabilisation and coordination of tongue movements during feeding. The lateral insertion and fascial connection of the digastric to the tongue in numbats may also aid in distributing stress evenly across the jaw and minimise muscle fatigue. The muscle descriptions and three-dimensional models provided in this study will facilitate further analysis of musculoskeletal adaptation and evolution within the Dasyuromorphia.

The proatlas, a bone located between the skull and the neural spines of the cervical vertebrae, is best known from reptiles. Most previous studies of the proatlas have centered on its developmental, debating the relationship between the proatlas and the cervical neural arches. The present study was intended as a description of the proatlas in the American alligator (Alligator mississippiensis) and an experimental test of its hypothesized role in venous blood and cerebrospinal fluid (CSF) distribution. In Alligator, the proatlas is chevron-shaped; ventrally it has a loose connection to the dorsal surface of the first cervical vertebrae, dorsally it has a robust elastic tissue tether on the otoccipital and supraoccipital bones. The ventral surface of the proatlas parallels the dorsal margin of the foramen magnum and rests on the dorsal surface of the spinal venous sinus. Experimental manipulation of the proatlas demonstrated that displacement of the proatlas causes pressure changes in both the spinal venous sinus and the enclosed spinal CSF. The results of this study represent the first demonstration of an explicit functional role for the proatlas, the circulation of fluids between the cranial and spinal compartments of the central nervous system.

Tessellated cartilage forms much of the skeleton of sharks and rays, in contrast to most other aquatic vertebrates who possess a skeleton of bone. Interestingly, many species of sharks and rays also regularly generate exceptionally high forces in the execution of day-to-day activities, such as when feeding on bony fish, mammals, and hard-shelled invertebrates. Tessellated cartilage differs from other types of cartilage in that they are covered by an outer layer of small mineralized tiles (tesserae) that are connected by fibrous connective tissue. Tesserae, therefore, are hypothesized to play a role in stiffening the cartilaginous skeleton for food capture and other activities that require the generation of high forces. In this study, the hyomandibula and ceratohyal cartilages, which support the jaw and throat regions of sharks and rays, were tested under compressive load in a material testing system to determine the contribution of tesserae to stiffness. Previous hypotheses suggest an abrupt upward shift in the slope of the stress–strain curve in tessellated materials due to collision of tesserae. Young's Modulus (E) was calculated and used to evaluate cartilage stiffness in a range of elasmobranch species. Our results revealed that there was an abrupt shift in Young's Modulus for elements loaded in compression. We postulate that this shift, characterized by an inflection point in the stress–strain curve, is the result of the tesserae approaching one another and compressing the intervening fibrous tissue, supporting the hypothesis that tesserae function to stiffen these cartilages under compressive loading regimes. Using published data for nontessellated cartilage for comparison, we show that this shift is, as expected, unique to tessellated cartilage.

Bryozoan colonies consist of zooids, which can differ in structure and function. Most heteromorphic zooids are unable to feed and autozooids supply them with nutrients. The structure of the tissues providing nutrient transfer is poorly investigated. Here, I present a detailed description of the colonial system of integration (CSI) and communication pores in autozooids and avicularia of the cheilosome bryozoan Terminoflustra membranaceotruncata. The CSI is the nutrient transport and distribution system in the colony. In both autozooids and avicularia it consists of a single cell type, that is, elongated cells, and has a variable branching pattern, except for the presence of a peripheral cord. The general similarity in the CSI structure in avicularia and autozooids is probably due to the interzooidal type of the avicularium. Interzooidal avicularia are likely to consume only a part of the nutrients delivered to them by the CSI, and they transit the rest of the nutrients further. The variability and irregularity of branching pattern of the CSI may be explained by the presence of single communication pores and their varying number. The structure of communication pores is similar regardless of their location (in the transverse or lateral wall) and the type of zooid in contact. Rosette complexes include a cincture cell, a few special cells, and a few limiting cells. Along each zooidal wall, there are communication pores with both unidirectional and bidirectional polarity of special cells. However, the total number of nucleus-containing lobes of special cells is approximately the same on each side of any zooidal wall. Supposing the polarity of special cells reflects the direction of nutrient transport, the pattern of special cells polarity is probably related to the need for bidirectional transport through each zooidal wall. The possibility for such transport is important in large perennial colonies with wide zones of autozooids undergoing polypide degeneration.

Mammalian middle ear cavities differ from those of other taxa as they comprise three ossicles and in rodents, can be encapsulated by an auditory bulla. In small mammals, the middle ear cavity (bulla) was found to be enlarged in the desert-dwelling species; however, differences in bullar size could have been due to ancestry. In this study, we sampled seven species from three genera (Myotomys, Otomys, and Parotomys) of the African murid tribe Otomyini (laminated-toothed rats), and compared the bullar volumes and shapes between the otomyine species and within the species Myotomys unisulcatus. Photographs of museum skull specimens were taken from ventral and lateral views, and the volumes of the bullae were estimated digitally from the photographs. No sexual dimorphism in bullar volumes was found in any of the species. Corrected bullar volumes were significantly different between species and larger bullae were seen in individuals inhabiting regions with lower annual rainfall. Bullar shape (estimated using geometric morphometrics) was significantly different between the genera and the species. Parotomys have tympanic meatuses that face more anteriorly compared to both, Otomys and Myotomys. When comparing bullae within M. unisulcatus, those inhabiting regions with lower annual rainfall had significantly larger bullar volumes, but no significant difference was found in bullar shape between the regions. This study shows that otomyine rodents in more xeric habitats have different auditory structures to those inhabiting wetter habitats.