Journal of Morphology最新文献

Traditional methods for studying the morphology of microturbellarian flatworms rely on light microscopy, which often lacks the resolution necessary to capture fine structural details. Therefore, we present a protocol to improve the visualisation of structural morphological details in microturbellarians by means of scanning electron microscopy (SEM). We demonstrate this method by imaging the sclerotised copulatory organs of three species of Trigonostomum (Rhabdocoela, Trigonostomidae): T. venenosum, T. setigerum, and T. penicillatum. Additionally, we successfully visualise the bursal appendage of T. penicillatum. SEM imaging offered new morphological insights for the genus, and corrected earlier interpretations made with light microscopy. The method requires precision and careful handling, especially during the isolation of the hard parts. However, it is cost-effective and straightforward to carry out in any standard laboratory setting. Hence, our SEM protocol complements traditional light microscopy and opens new avenues for taxonomical research in microturbellarian taxa with hard parts.

Ants occur in a remarkable diversity of species, many of which fulfill essential ecological roles and exhibit complex eusocial behaviors. Among their unique adaptations are specialized exocrine glands, such as the pre-pharyngeal and pharyngeal glands, which produce secretions crucial for physiology and social cohesion. Despite their importance, these glands are poorly studied in Paraponerinae and Ponerinae species. This study examines the morphology and chemical composition of these glands in workers of Paraponera clavata (Paraponerinae) and Pachycondyla crassinoda (Ponerinae). The results document distinct morphological and morphometric differences: the pre-pharyngeal gland in P. clavata is larger, with cells rich in proteins and glycoproteins, whereas in P. crassinoda, the gland has more extensive secretory cells and a higher concentration of lipids. Additionally, the pharyngeal glands in P. clavata are tubular, while in P. crassinoda, they have large lobes with internal cuticular projections. Chemical analyses identified shared hydrocarbons between the species, as well as unique compounds that may reflect specific behavioral and ecological adaptations. These findings suggest that morphological and chemical differences in these ants' glands are potentially associated with dietary habits and behavioral traits.

Circulatory systems are characteristic of most multicellular animals. In parasitic organisms, which may differ strikingly from their free-living relatives, such systems remain the least studied. Rhizocephala (Pancrustacea: Cirripedia) are among the morphologically most derived parasitic crustaceans. In the adult rhizocephalan female, transport presumably takes place along the lacunar system inside the interna rootlets and the externa. The aim of our study was to visualize and describe the lacunar and muscular systems in the externa of Polyascus polygeneus and Parasacculina pilosella (fam. Polyascidae) using micro-computed tomography and confocal microscopy. The lacunar system in the externae of both species consists of the stalk lumen, mesentery lacuna accompanying the visceral mass and mantle lacunae. These elements of the lacunar system are similar to those previously described in Peltogasterella gracilis (fam. Peltogasterellidae). However, the interposition of these elements differs. The organization of the muscular system mostly corresponds to previous descriptions in other rhizocephalan species, however some unexpected results were obtained. For example, P. polygeneus has an age-related differentiation of mantle musculature, which was not described before for any rhizocephalan species. Obtained data on lacunar and muscular systems organization allow us to assume the change in the externa body axes in the family Polyascidae.

The morphology of the superficial fascia in the canine hindlimb is still poorly understood and incompletely described. The present study aimed to elucidate the macroscopic and microscopic structures of the superficial fascia, thereby clarifying its functional role. Cadavers were investigated for anatomic description (N = 38), ultrasonic scanning (N = 2), and histological analyses (N = 10) of this tissue in the hindlimb. The superficial fascia was identified as a shiny, white fibroelastic layer that adhered to the skin through fibrous septa. It was organized into sublayers enveloping the cutaneous muscle and large blood vessels. In certain areas, superficial fascia fused with the deep fascia or skin, creating fascial bursae. These bursae included the ischiatic bursa, an iliac bursa, a prepatellar subfascial bursa, a prepatellar subcutaneous bursa, and the tarsal fascial bursa. Microscopically, the superficial fascia presented as a layer of dense connective tissue characterized by irregularly arranged collagen and elastic fibers. The superficial fascia was firmly attached to the skin and deep fascia by numerous fibrous tissue strands. Within both, the superficial fascia and fascial bursae, several mechanoreceptors and nerve endings were identified, including Ruffini's corpuscles, Pacinian corpuscles, and Golgi-Mazzoni corpuscles. The organization of the superficial fascia and its attachments suggest a mechanical role in supporting structures and resisting loads during movement. The fibrous septa anchors fascia to the skin, providing stability and resistance against external forces, as well as protecting the nerves and blood vessels that pass towards the skin. Existing fascial bursae probably assist in decreasing pressure and facilitating freedom of movement adjacent to bony prominences. Elasticity and connectivity of the superficial fascia may explain the various responses to multidirectional loading. Furthermore, the presence of free nerve endings and mechanoreceptors within the fascia suggests that it may contribute to proprioception of the hindlimb, enhancing the awareness of body movement.

Over the course of its evolution, the human soleus muscle has rapidly increased in size and gained a more important role in bipedal locomotion. However, the detailed processes underlying these morphological changes remain uninvestigated. When discussing these morphological changes in muscles, the innervation patterns among primates is an important criterion to consider and compare. In this study, we comprehensively investigated the detailed intramuscular nerve distribution patterns of the soleus muscle in nine extant primate species and provide new evolutionary implications. The human soleus muscle is innervated by two branches of the tibial nerve: the posterior nerve branch innervates the major posterior part of the soleus muscle, and the anterior nerve branch innervates the anterior bipennate part of the soleus muscle. The soleus muscle is innervated by the posterior branch in all species and by the anterior branch in five of the nine primate species. The prevalence and distribution patterns of the anterior branches varies even between closely related species. However, these variations were not associated with the intramuscular distribution patterns of the posterior branches. Therefore, the distribution of the anterior and posterior branches may have evolved independent of each other. In humans, the anterior branch and intramuscular subbranch of the posterior branch—that innervates the muscle fascicles originating from the soleal line on the tibia—are distributed more widely within the soleus muscle than in non-human primates. This rapid increase in size and medial expansion of the soleus muscle over the course of human evolution may be due to the expansion of the two parts of the soleus muscle innervated by these two branches.

Scanning electron microscopy (SEM) is a fundamental technique to study the morphology of anuran embryos and tadpoles. Here, we present a drying method for SEM imaging of late frog embryos using commonly available dehydration solvents such as ethanol or methanol, xylene, and applying low temperature vacuum freeze drying. Briefly, embryos from early embryonic gills development to hatching were fixed with a paraformaldehyde—glutaraldehyde mix, then dehydrated to ethanol or methanol, and then slowly dried using low temperature and constant vacuum pressure. An extra step of clearing using xylene after ethanol dehydration improved results considerably. Our protocol successfully preserved embryo shape and the morphology of fragile and delicate superficial structures (e.g., external embryonic gills, apical ectodermal microridges and surface ciliation), while avoiding the use of some SEM toxic reagents.