Journal of Morphology最新文献

Anatomical variants can be used effectively to identify relationships between individuals in kinship analysis and they may be useful during surgical procedures. These procedures can be better implemented when the cause, appearance and location are understood. Clear representations and definitions of anatomical traits are necessary. A similar morphology of pathologies and variations of normal morphology can lead to confusion and unnecessary intervention. Therefore, there is a considerable need for an anatomical atlas of the particular skeletal elements, such as the talus bone. We have analyzed a total of 925 tali, 591 belonging to different modern and pre-Hispanic samples. Furthermore, 334 tali were analyzed from a reference collection from Athens. We have identified and defined the anatomical variants of the talus bone, of which only some have been mentioned by other researchers. We propose standardized methods that may potentially improve future research in human skeleton anatomy and its applications. We provide information on anatomical variants with the aim of improving their identification, classification and use in medical professions and bioanthropology.

The colonial system of integration (CSI) provides intracolonial nutrient supply in many gymnolaemate bryozoans. In Ctenostomata, its presence is known for species with stolonal colonies, for example, vesicularioideans, but its structure is almost unexplored. The CSI is thought to be absent in alcyonidioideans and other ctenostomes. Here, we present the first detailed description of the CSI ultrastructure in both autozooids and kenozooids of two vesicularioideans, Buskia nitens and Amathia gracilis, and two alcyonidioideans, Alcyonidium hirsutum and Flustrellidra hispida. We revealed differences in the endocyst structure: in studied alcyonioidioideans, it comprises the epidermis, extracellular matrix and coelomic lining, while in the studied vesicularioideans, it includes only the epidermis. In vesicularioidean autozooids, the main CSI cord and the most distal part of the muscular funiculus originate together as a single structure near the caecum apex. However, at a short distance basally, they separate and run to different sites: the main CSI cord reaches the communication pore, and the muscular funiculus attaches to the cystid wall in the proximal part of the autozooids. The CSI in alcyonidioidean autozooids includes a central part, comprising several strands running from the caecum and pylorus to the cystid walls, and a peripheral part, which is located between the epidermis and peritoneum of the cystid walls and reaches the communication pores. The autozooidal CSI in the studied alcyonidioids never reaches kenozooidal communication pores. Nevertheless, the CSI is present in kenozooids of F. hispida; its structure corresponds to that of the peripheral part of the CSI in autozooids. These findings suggest that the CSI likely originated rather early in bryozoan evolution, and its putative initial function is nutrient transport to budding sites and zooids undergoing degeneration-regeneration cycle.

Booidean snakes are a diverse and widespread lineage with an intriguing evolutionary and biogeographic history. By means of cranial morphology and osteology, this study investigates the evolutionary convergence in the Neotropical genera Boa and Corallus on the one hand and the Malagasy clade comprising Acrantophis and Sanzinia on the other. We hypothesize that the mostly arboreal Corallus and Sanzinia present larger jaws and longer teeth to keep hold of the prey and resist gravity and torsional forces acting on their skull while hanging from branches, while terrestrial genera such as Acrantophis show thinner jaws with shorter teeth because they can rely on the full length of their coils to immobilize and constrict the prey together with a substrate that supports the whole of their body. Overall, we highlight how booidean snakes can serve as intriguing subjects for the study of contingency, determinism, and opportunity in the evolution of distant lineages both phylogenetically and geographically. We also provide the first complete description of the skull of Boa constrictor.

The skin of the Komodo dragon (Varanus komodoensis) is covered by a form of armour formed mainly of scales, which often co-occur with osteoderms. Scales are keratinized, non-mineralized structures in the uppermost layer of the epidermis that are in contact with each other to form a system in which individual scales are isolated from each other by a softer skin fold zone. In the Varanus, the surface of the scales is flat and smooth (thoracic limb, abdomen, and tail areas), domed and smooth (head area) or domed with conical ornamentation (dorsal surface, pelvic limb—dorsal surface areas). In contrast, osteoderms are mineralized structures that are an integral part of the skin, located below the epidermal surface and positioned parallel (head, tail, thoracic limb-dorsal surface, thoracic limb-palmar surface, and tail) or obliquely (pelvic limb-dorsal surface, groin, abdomen) to the surface. Regardless of the body region, osteoderms are structures that are completely anchored in the dermis, and their surface is smooth and devoid of ornamentation. Tangential sections of the osteoderms demonstrate concentric resting lines. Histological sections of the varanid dermis show the presence of collagen bundles, parallel interlacing or crossing bundles of collagen fibers of varying thickness and degree of compactness, accompanied by muscle fibers. In the area of skin close to the osteoderm, loosely arranged bundles of collagen fibers are present, while in the zone distal to the osteoderm, a compact arrangement of these fibers is present. This study documents the morphological diversity and distribution of osteoderms and scales in selected areas of the body of V. komodoensis. Scales are characterized by a high polymorphism related to body region, while osteoderms show a high morphological similarity independent of the area of occurrence.

In the phylum Nemertea, the class Hoplonemertea (former Enopla) comprises the largest number of studied species with complex spermatozoa. Asteronemertes gibsoni Chernyshev, 1991, a nemertean species having a symbiotic relationship with sea stars, is characterized by complex filiform spermatozoa. Here, spermatogenesis and spermatozoon structure in A. gibsoni have been examined using light and electron microscopy. Numerous proacrosomal vesicles of two kinds have been found in early spermatogenic cells. In spermatozoa, the elongated acrosomal complex consists of two components: a core, which is a spindle-shaped electron-dense acrosomal vesicle with a long anterior end, and its casing of moderate electron density that covers the acrosomal vesicle completely. The acrosomal complex is located laterally relative to the elongated nucleus. The acrosomal casing bears two rows of small, short channels between the nucleus and the electron-dense acrosomal core. In late spermatids, the elongations of the acrosomal complex and the nucleus occur simultaneously and are mediated by numerous microtubules that disappear during the latest stages of spermiogenesis. The flagellum in spermatogenic cells and spermatozoa contains an axoneme with the usual 9 × 2 + 2 microtubular organization and is posteriorly oriented in spermatozoa. As known to date, A. gibsoni has the most modified spermatozoa among investigated Nemertea, and the complex structure of its sperm is suggested to be associated with the reproductive biology, in particular, with fertilization. Additionally, a number of similar ultrastructural features in spermatozoon organization have been found in A. gibsoni and Kurilonemertes phyllospadicola whose phylogenetic relationship was previously proven.