Journal of Morphology最新文献

A major goal of evolutionary ecology is to understand the interaction between ecological differences and the functional morphology of organisms. Studies of this type are common among flying birds but less so in penguins. Penguins (Spheniscidae) are the most derived extant underwater flying birds using their wings for swimming and beak when foraging. The Humboldt Penguin (Spheniscus humboldti) and Magellanic Penguin (S. magellanicus) occur along the coast of South America and their morphology was compared in allopatry and sympatry throughout their ranges. Measurements included: mass, tarsus length, four beak/head dimensions, bite force, wing loading, and aspect ratio. A thin-plate spline/relative warp analysis was also used to detect subtle differences in wing shape. Both species generally overlapped in trait morphology, but Magellanic Penguins showed greater trait diversity. Wing morphology was more homogenous between species than beak morphology indicating a similar mode of locomotion but potential differences in prey procurement. Morphological character displacement in sympatry was only evident in beak length. Local adaptation was common in other traits, and Punta Norte (Argentina) was often distinct in having high variation, notably in beak depth, wing loading, and wing shape (relative warp 1). This may be attributed to the fact that penguins here dive deep and forage farther from their colony; they also have a greater colony size that may contribute to greater intraspecific competition for resources. These results support a potentially optimal wing design for aquatic movement, which likely applies to other penguin species. Differences in morphology may also be related to differences between Atlantic and Pacific ecosystems.

Although numerous studies have addressed some aspects of the cranial osteology of Nearctic dipsadid species, only the species within the genera Heterodon and Carphophis have a formal published description of their skull. Similarly, vertebral data on such species are extremely scarce, and most of the available literature is focused on fossils. Such group has a complex phylogenetic history, being recovered as monophyletic or nonmonophyletic depending on the approach. In this paper, we provide detailed and comparative descriptions of the osteology of dipsadid species distributed in the Nearctic region based on 69 specimens of dry material and high-resolution computed tomography (CT) scans. Additionally, we explore the morphological variation of the skull and cervical vertebrae within the context of distinct phylogenetic hypotheses previously proposed. Only two suprageneric groups previously proposed shared exclusive morphological traits: (Carphophis amoenus + Contia tenuis), proposed by three studies, and (Diadophis punctatus (Ca. amoenus + Co. tenuis)), proposed by one study. Large and detailed studies on the skull, mandible, and vertebrae represent an important step toward the understanding of the evolution of species, especially when they also show intraspecific variation.

Dental anomalies are frequent in boars and pigs, and they generally affect the first premolar loci. The prevalence of these dental anomalies was investigated in a large number of populations around the world. These studies mainly focused on the influence of domestication, size, sexual dimorphism or food hardness on these anomalies. However, they rarely considered ontogenetic aspects, while these are crucial for understanding their aetiology during animal growth and how the dental row-jaw complex is affected. Here, we studied the incidence of missing first upper and lower premolars in a French population of captive wild boars to discuss the functional and developmental reasons for missing teeth and to assess the impact of missing teeth on the growth of the dental row-jaw complex. Using the CT-scan data of the cranium and mandible of 24 wild boars investigated six times each during their growth, and presenting a balanced sex ratio, we recorded the number of missing teeth. We then quantified the shape of the upper and lower jaws using 3D geometric morphometrics. We found a similar prevalence of missing first premolar (37.5%) between the upper and the lower jaws, which is higher than the frequencies observed in most continental populations of wild boars. The increasing number of anomalies during ontogeny suggests a relaxed constraint on the dentition associated with a different feeding behaviour in captivity. The absence of first premolars does not appear to be associated with size variation or sexual dimorphism, nor does it affect the place of the dentition within the jaw, the latter being more influenced by the dimorphic shape of the canines and the timing of dental eruption.

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.