Journal of Morphology最新文献

Birds possess a unique balance organ, the lumbosacral organ (LSO), located in the lumbosacral region of the synsacrum. This organ surrounds the spinal cord and leaves distinct traces of its size and shape on the endocast of the vertebral canal. To date, many questions about the function of the LSO and its implications in bird biology remain. Here, we investigate whether the shape of the synsacral vertebral canal endocast, influenced by the LSO, is related to locomotor habits, pelvic morphology, and phylogeny. We used 2D and 3D geometric morphometrics to characterise the shape of the digital synsacral vertebral canal cast and to test whether its morphology is indicative of locomotor behaviour and pelvic morphology. We also quantified the phylogenetic signal to determine whether phylogeny has an impact on morphology. Our results suggest that the vertebral canal endocast is shaped by the LSO, particularly in predominantly perching birds, where it is proportionally larger than in other locomotor groups. We also show that the pelvic morphology covaries significantly with the vertebral canal morphology. A proportionally larger LSO corresponds to a shorter, wider pelvis, while a smaller LSO corresponds to a longer, more slender pelvis. Finally, in addition to a strong phylogenetic signal in vertebral canal morphology, we identify allometry, indicating that body size also influences LSO morphology.

The white-eared opossum, Didelphis albiventris, is an opportunistic and omnivorous marsupial, whose diet ranges from wild fruits to eggs and birds. Salivary glycoproteins play a key role in the protection of the oral cavity and the formation of the food bolus. Despite the importance of salivary glycoproteins, their detailed investigation in the white-eared is lacking. This study investigated the morphology and glycan composition of the mandibular salivary glands of the white-eared opossum for the first time. Histological and histochemical investigations were conducted on tissue fragments fixed with 4% PBS-buffered paraformaldehyde and embedded in Paraplast. The pattern of glycoproteins was investigated using traditional histochemical methods (PAS, Alcian Blue pH 2.5, and High-Iron Diamine staining) and lectin histochemistry. The glandular parenchyma consisted of acinar secretory units and a duct system characterized by abundant striated ducts. Secretory acini secrete neutral glycans and non-sulfated acid glycans. Mannosylated N-linked glycans terminating in α2,6-sialic acid and fucose are expressed in the secretory acini, containing intraluminal α2,3-sialylated O-linked glycans. The epithelial lining of the striated and interlobular ducts also shows O-linked glycans with terminal Galβ1, 3GalNAc, and αGalNAc residues. Finally, the epithelium and lumen of interlobular ducts are enriched with additional GalNAc-terminated O-linked glycans with the appearance of lactosaminated glycans and the disappearance of α2,3-sialylated glycans. These results suggest that the saliva produced by the mandibular gland of the white-eared opossum consists of a species-specific pattern of glycoproteins, to whose composition the ductal system also contributes. The observed glycan composition is probably related to the diet of the white-eared opossum and its adaptations to the environment and food availability. These results indicate that the mandibular salivary gland of the white-eared opossum Didelphis albiventris has specific histological and molecular characteristics compared to other marsupial species, suggesting that diet and habitat, but not the taxonomic group, influence the mandibular gland features.

Several species of natricine snakes sequester bufadienolides from toads, store them in their nuchal glands, and reutilize them for their defense. This study aimed to examine the presence and morphological features of nuchal glands of natricine snakes distributed in Indonesia, containing several lineages of this group. When the presence of the glands was confirmed, the gland fluids were analyzed to identify their chemical components. Secretions from the parotoid glands of several species of toads in Indonesia were also analyzed. Morphological examination of the glands was conducted by observing the presence or absence of structures and recording the spatial pattern of the glands. The glandular fluids of three snake species and four toad species were extracted and analyzed by liquid chromatography/mass spectrometry (LC/MS). Nuchal glands or organs similar to the glands were found on the head or neck region of preserved or freshly dead specimens of Rhabdophis subminiatus, R. flaviceps, R. rhodomelas, and Rhabdophis spp. of Sulawesi, although such a gland was not found in the other genera of natricine snakes. These Rhabdophis species have different spatial patterns of glands, and particularly Rhabdophis spp. of Sulawesi showed an unusual novel gland form in the temporal and occipital regions of the head, possibly comparable to the nuchal glands. Bufadienolides of the bufogenin and bufotoxin types were identified from all toad gland fluids. In contrast, the glandular fluids of snakes, R. subminiatus, R. flaviceps, and Rhabdophis spp. of Sulawesi store only bufogenin-type bufadienolides. Bufadienolide profiles of snakes and toads indicate that the toxin composition is highly diverse among species. The results suggest that snakes would be able to chemically convert dietary bufadienolides from toads and reutilize some bufadienolides readily. This study demonstrated that the form and location of “nuchal glands” in a snake's body are more diverse than previously recognized.

In the reproductive dynamics of anurans, the male gonads have a fundamental relationship with the kidneys. Although reproductive aspects have been widely studied in this group, there are still considerable gaps in understanding the morphology and physiology of the reproductive system of neotropical anurans. Most research has emphasized aspects such as spermatogenesis and reproductive ecology, without information on the structure of the male reproductive tract and the dynamics of spermatogenesis in different species. To better understand the reproductive diversity of anurans, it is essential to comprehend reproductive morphology in a broad sense and simultaneously at different organizational levels. In this context, the present study aimed to characterize the components of the male reproductive tract and assess testicular cell proliferation in Leptodactylus podicipinus throughout its reproductive cycle, using histological, immunohistochemical, and computerized microscopy techniques. The male reproductive tract of this species comprises intratesticular ducts that converge into a longitudinal collecting duct, which gives rise to extratesticular efferent vessels entering the kidneys through lateral ducts. These ducts take the sperm through the glomeruli to the collecting ducts, leading to the Wolffian duct. Differences were observed in the intratesticular ducts of individuals in the reproductive and nonreproductive periods. Additionally, the proliferation of the initial germ cells (spermatogonia and spermatocyte I) exhibited positive PCNA staining, with distinct differences between the two periods analyzed.

The avian quadrate plays a critical role in cranial kinesis, but few comparative studies exist of its morphological variation across higher-level taxa. The present paper surveys the occurrence of a markedly concave articular facet of the condylus medialis. It is detailed that this feature, for which the term trochlea lateralis is introduced, may represent an apomorphy of a higher-level clade that includes the Aequornithes (gaviiforms, procellariiforms, suliforms, pelecaniforms, and allies), Phaethontimorphae (tropicbirds, sunbittern, and kagu), Mirandornithes (flamingos and grebes), and Gruiformes (cranes and allies). Like many other morphological characters, the occurrence of the trochlea lateralis shows homoplasy. However, at least one analysis of sequence data found a clade including the aforementioned four taxa, the interrelationships of which are not conclusively resolved in other studies. A trochlea lateralis is present in birds with different cranial morphologies and feeding adaptations, so that its occurrence often seems to have a phylogenetic (shared common ancestry) rather than a functional origin. The morphology of the condylus medialis of the quadrate may also bear on the affinities of some fossil taxa, such as the early Eocene Halcyornithidae and Messelasturidae, in which a trochlea lateralis is present.

Understanding how extinct animals moved is a central goal in paleobiology, yet interpreting locomotor function from anatomy alone is complicated by convergent and divergent morphologies. One promising approach is the construction of morphofunctional spaces (MFSs), which integrate multiple biomechanical indices and comparative statistics to refine functional inference. This study investigates forelimb adaptations for digging in Caraguatypotherium munozi (Notoungulata, Mesotheriidae), a mid-sized Miocene notoungulate lacking extant analogs. We developed an MFS based on osteological measurements and mechanical advantage (MA) models at the elbow and wrist. These were derived from fossil material and comparative data across 38 extant mammal species representing 21 families and 5 locomotor habits—terrestrial, fossorial (digger), climbing, swimming, and flying—as well as 5 mesotheriid specimens, including the holotype of C. munozi. Multivariate and inferential statistical analyses were used to identify functional patterns and evaluate locomotor hypotheses. Results show that C. munozi occupies an intermediate position in MFS, adjacent to but outside the core regions of extant fossorial, climbing, and terrestrial mammals. It exhibits the highest wrist flexor MA (31.4%) in the data set, 9%–13% above the range of living scratch-diggers, and a low elbow extensor MA (~19%), below the fossorial mean (~31.6%). Notably, incorporating manus length (MTCIII-L) into the elbow model lowers MA further but places C. munozi within the statistical range of extant diggers, suggesting partial mechanical similarity. This biomechanical pattern supports a wrist-dominant excavation strategy, reflecting a distinct mechanical pathway that enabled C. munozi to perform the motor gesture of scratch-digging through enhanced distal force generation, rather than relying on proximal joint leverage as in extant fossorial mammals. The integration of MA with osteological indices within a multivariate framework provides novel insights into extinct mammalian locomotion and underscores the utility of MFS models for reconstructing context-dependent motor capabilities and locomotor habits.