Journal of Morphology最新文献

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.

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.

For over a century researchers have marveled at the square-shaped toe tips of several species of climbing salamanders (genus Aneides), speculating about the function of large blood sinuses therein. Wandering salamanders (Aneides vagrans) have been reported to exhibit exquisite locomotor control while climbing, jumping, and gliding high (88 m) within the redwood canopy; however, a detailed investigation of their digital vascular system has yet to be conducted. Here, we describe the vascular and osteological structure of, and blood circulation through, the distal regions of the toes of A. vagrans using histology in tandem with live-animal videos. Specifically, we sectioned a toe of A. vagrans at 0.90 μm, embedded it in Spurrs resin, and stained the tissue with toluidine blue. An additional three toes were sectioned at 10 μm, embedded in paraffin, and after sectioning and mounting, treated with Verhoeff and Quad stains. For living salamanders, we recorded real-time videos of blood flowing within individual toes upon a translucent surface oriented both horizontally (0°) and vertically (90°) to simulate both prostrate and vertical clinging scenarios, then analyzed the image sequences using ImageJ. We found that the vascularized toe tips have one large sinus cavity that is divided more proximally into two chambers via a septum, and there are mucous and granular glands in the dorsal and dorsolateral integument of the digit tips. Live-animal trials revealed variable sinus-filling both within and between toes, seemingly associated with variable pressure applied to the substrate when standing, stepping, clinging, and climbing. We conclude that A. vagrans, and likely other climbing salamanders, can functionally fill, trap, and drain the blood in their vascularized toe tips to optimize attachment, detachment, and complex arboreal locomotion (e.g., landing after gliding flight). Such an adaptation could provide insights for bioinspired designs.

Dental impressions, developed for accurate capture of oral characteristics in human clinical settings, are seldom used in research on nonlivestock, nonprimate, and especially nonmammalian vertebrates due to a lack of appropriate tools. Studies of dentitions in most vertebrate species usually require euthanasia and specimen dissection, microCT and other scans with size and resolution tradeoffs, and/or ad-hoc individual impressions or removal of single teeth. These approaches prevent in-vivo studies that factor in growth and other chronological changes and separate teeth from the context of the whole mouth. Here, we describe a non-destructive method for obtaining high-resolution dentition-related traits that can be used on both living animals and museum specimens for almost all vertebrates, involving a customizable and printable dental impression tray. This method has repeatedly and accurately captured whole-mouth morphology and detailed features at high resolution in the living non-teleost actinopterygian fish, Polypterus senegalus, in a laboratory setting. It can be used for comparative morphology and to observe temporal changes such as the presence of microwear, tooth replacement rates, and occlusal and morphological changes through ontogeny.

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.

The barn owl is a common research subject in auditory science due to its exceptional capacity for high frequency hearing and superb sound source localization capabilities. Despite longstanding interest in the auditory performance of barn owls, the function of its middle ear has attracted remarkably little attention. Here, we report the middle ear transfer function measured by laser Doppler vibrometry and direct measurements of inner ear pressures. Our results illustrate that the barn owl middle ear produces a pressure gain between the ear canal and the inner ear vestibule of up to 35 dB, which is comparable to that seen in mammals. The footplate velocity transfer function magnitudes overlap with those measured in other bird species, however the differences in phase between the footplate velocity and the sound pressure stimulus indicate a middle ear group delay that is notably shorter than other birds. This work brings us closer to a more complete understanding of the physiology of hearing in a model organism in auditory science.

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.

Skeletochronology and growth dynamics are intensively investigated in vertebrate osteohistology. These techniques are particularly important for interpreting the life history of long-lived species, such as crocodilians. To understand the longevity, growth dynamics, sexual maturity, and sexual dimorphism of caimans we studied an almost complete ontogenetic series of captive and wild specimens of Caiman latirostris from different localities of Argentina. We identified both cyclical and noncyclical growth marks in juvenile caimans, and we suggest that the latter are associated with environmental stress. By overlapping the growth marks of different individuals, we were able to estimate the minimum age of each specimen. Variations in growth rate are evident in different bones, with the femur and scapula having the highest growth rates, while the fibula and pubis have much slower growth rates. We were able to determine the approximate age of sexual maturity from growth curves deduced from osteohistology, which concurred with those assessed in ecological studies. Additionally based on the growth curves we were able to document different growth dynamics which may be related to sexual dimorphism. This study provides valuable insights into the life history and ecological dynamics of crocodilians, shedding light on their growth patterns, attainment of sexual maturity, and the influence of environmental factors on growth. Furthermore it documents the intraspecific and interelemental osteohistological variation in crocodilians and has direct implications for studies that assess the life history of extinct archosaurs and other sauropsids.

Muscle fibre architecture is an important aspect of anatomy to consider when estimating muscle properties. How fibre architecture varies across species specialising in different locomotor functions is not well understood in anurans, due to difficulties associated with fibre extraction in small animals using traditional methods. This paper presents the first digital analysis of fibre architecture in frogs using an automated fibre-tracking algorithm and contrast-enhanced µCT scans. We find differences in hindlimb muscle fibre architecture between frogs specialising in different locomotor modes, as well as examples of many-to-one mapping of form to function. The trade-off between fibre length and muscle physiological cross-sectional area, and therefore contractile speed, range of motion and muscle force output, differs significantly between jumpers and swimmers, but not walker-hoppers. Where species place on this functional spectrum of fibre architecture largely depends on the muscle being examined. There is also some evidence that fibre length may be adjusted to increase contractile speed without undertaking the metabolically expensive process of growing and maintaining larger muscles. Finally, we make a detailed outline of the remaining gaps in our understanding of anuran fibre architecture that can now be addressed with this valuable digital method in future research.