Journal of Morphology最新文献

Appendicularia comprises about 70 holoplanktonic species traditionally classified in three families: Oikopleuridae, Fritillariidae, Kowalevskiidae. Despite their eminent phylogenetic position and their important role in ocean ecosystems, most research focuses on the model organism Oikopleura dioica while the diversity of appendicularians remains underexplored. Here, we present a comparative morphological analysis of appendicularian endostyles, a pharyngeal gland homologous to the vertebrate thyroid. Based on light- and transmission electron-microscopical investigations in 12 species representing seven (of 15) genera from all three family-level taxa, we describe the 3D-anatomy of endostyles, histologically recognizable cell-types, and discuss our findings in a cladistic framework. We identified seven different cell types arranged in species specific patterns, including the formerly unrecognized ‘bright cells’. Two ciliary bands – the peripharyngeal band and the retropharyngeal band – are associated with the endostyles. Outgroup comparison indicates that repeated apomorphic reductions of cell types, rows of cells, the retropharyngeal band, and the complete endostyle occurred within Appendicularia. We propose a phylogenetic hypothesis that suggests that “Oikopleuridae” is a paraphyletic grouping and supports an evolutionary scenario with multiple reductions functionally related to the evolution of the external filter house of appendicularians. While we document the diversity of endostyle anatomy, more detailed cladistic analysis, including other organ systems, is needed to resolve the phylogenetic relationships and to understand the evolution of appendicularian taxa.

The stifle joint is among the most commonly injured joints in dogs. Detailed functional information is required to identify the causes of damage and determine the most appropriate treatment strategy. The lateral condyle of the femur and its attaching structures play an important role in joint stability, which is essential for proper joint movement. The long digital extensor and popliteus muscles originate from the lateral condyle, and their functions have not been described properlyresulting in contrasting functional interpretations. In this study, we suggest new functional hypothesses for these muscles based on their origin coordinates from the lateral condyle in dogs. The popliteus muscle may act as either an extensor or a flexor depending on the stifle angle during the stance phase, in addition to facilitating rotational movement. The long digital extensor muscle functions as an extensor of the joint and may prevent the lateral condyle from slipping caudally during stifle extension. It may also help prevent cranial tibial thrust on the lateral side of the tibial plateau during extension. From a parcticioner point of view we suggest that, during the stifle surgery, the muscles are preserved as much as possible.

Over a century ago, Dutch anatomist and geologist Eugène Dubois discovered the famous “Java man” and associated mammals in Java. His collection continues to be widely recognised for its significance to palaeontology and palaeoanthropology. Mammal fossil remains from Dubois’ collections have been essential for understanding faunal migrations driven by Quaternary glacial cycles from Southeast Asia to the Sunda Shelf and beyond, and thus the evolution and present distribution of mammals across Island Southeast Asia (ISEA). An important group are the Suinae (pigs). Most extant Eurasian Suinae species belonging to the genus Sus, except the widely distributed Sus scrofa, are mostly found in ISEA, and represent an example of species radiation. Knowledge of the origin, migration, and evolution of the genus Sus is limited, and studies on ecomorphological disparity and phylogeny of fossil Suinae are scarce. Considering the importance of ISEA in the evolutionary history of the genus, a detailed understanding of the fossil Sus species from the region is key to understanding the origin, dispersal, and evolution of Sus. Here, I focus on the anatomy of two endemic species from the Middle Pleistocene of Java (Indonesia), S. brachygnathus and S. macrognathus. A detailed anatomical description and morphological comparison between these species and extant and fossil suids are provided, including hitherto undescribed features of two species in the context of ecomorphology. Finally, aspects of the phylogenetic relationships of both species are discussed in relation to insular evolutionary trends. The importance of these fossil Sus remains from Java lies not only in their key role to understanding the evolutionary history and diversification of Sus, but also in providing insights into the evolutionary trends of insular pigs.

The cephalic musculature of the Pacman catfish Lophiosilurus alexandri (L. alexandri) is described and compared with Pimelodus maculatus, Pimelodus microstoma, Pseudopimelodus mangurus (P. mangurus), Batrochoglanis labrosus (B. labrosus), and Lophiosilurus fowleri (L. fowleri). Besides the distinguished Pacman catfish head shape, which is strongly depressed, broad, and with a large mouth, we hypothesize that the gross morphology of the musculature is related to the phylogenetic background. A phylogenetic analysis of selected characters evidenced three putative synapomorphies for the family Pseudopimelodidae, three for the subfamily Batrochoglaninae, three for the genus Lophiosilurus, two autapomorphies for L. alexandri, one for L. fowleri, one for B. labrosus, and five for P. mangurus. The absence of the retractor tentaculi is interpreted as a putative synapomorphy of Pseudopimelodidae and Pimelodidae. The rounded adductor mandibulae emerge as the predominantly voluminous musculature in L. alexandri and other Pseudopimelodidae, a conspicuous synapomorphy of the family. Profound differences were observed when comparing the cephalic musculatures of L. alexandri with Lophius piscatorius and Chaca bankanensis, which are unrelated species with similar body morphology and ambush behavior. The morphology of cephalic musculature highlights the plasticity of the musculature function and the closer relationship with the phylogenetic history of species and lineages.

The skeleton is a rich source of characters used in phylogenetic studies of teleost fishes. However, the development of bones was studied in a limited number of species and few studies have been published describing the ontogeny of the Characiformes skeleton. We provide the first complete description of the skeleton ontogeny of an anostomid, Leporinus oliveirai, based on specimens bred in captivity and sampling the first 60 days post-hatching, with sizes ranging from 3.8 mm (notochord length, NL) to 33.2 mm (standard length, SL). Sixty-three specimens were cleared and double stained and subsequently dissected and photographed. The developmental sequence of 141 bony elements is documented. Photography of all anatomical complexes is presented during the development. The first bone to develop is the cleithrum (5.1 mm NL) and the last ones are infraorbitals 4, 5 and 6, extrascapular and sclerotic bones (27.2-29.7 mm SL), similar to what is observed in the development of other characiforms. The main discoveries are numerous conical teeth on the premaxilla and dentary from 5.1 mm NL to 10.4 mm SL that are replaced with three or four large incisiform multicuspid teeth, that become unicuspid in juveniles and adults. The infraorbitals 4 and 5, seen only in juveniles, develop fused, a condition that is in contrast to most anostomids. The autopalatine cartilage begins its development straight, becoming curved during development. The developmental sequence is compared with other Characiformes and the unique characteristics of Anostomidae are discussed concerning the phylogenetic relationships among the family members.

The order Hemiptera s. lat. (=Homoptera + Heteroptera), comprising approximately 140 families and 70,000 species, is the largest order among hemimetabolous insects in terms of species diversity. A key trait shared among these insects is their specialized piercing-sucking mouthparts, which have been considered an important factor in their diversification. However, knowledge of how these characteristic hemipteran mouthparts form during embryogenesis remains limited and biased toward model species. In this study, we observed the embryonic development of the heteropteran insect Appasus japonicus (Belostomatidae). We divided its embryonic development into 10 stages and provided a detailed description. Additionally, we examined its developmental processes and compared them with the embryogenesis of closely related groups. As a result, we confirmed that (1) the maxillary plate, one of the structures forming the heteropteran mouthparts, is homologous to the maxillary palp, and (2) most parts of the stylet-like mandibles and maxillae are housed within the labial palp.