To describe the structural development of the liver in young guppies (Poecilia reticulata) and complement the adult characterisation, we conducted a histological study at 7, 17, and 28 days post-birth. We used serial sections to trace the organisation of blood vessels, bile ducts, and pancreatic tissue within and around the liver. At all ages, the liver was highly cellular and composed mainly of hepatocytes. Pigmented melanomacrophage centres or aggregates were not observed, whereas rodlet cells were rare and restricted to extrahepatic connective tissue. At 7 days, we identified four distinct venous entry points. This multi-afferent pattern persisted at Days 17 and 28. Arterioles remained restricted to the outer hilar region and were not observed within the liver. The gallbladder and common hepatic duct were recognisable at Day 7. In contrast, intrahepatic bile ducts were not discernible at Day 7, were scarce at Day 17, and were more frequent, although still limited, at Day 28. Exocrine pancreatic tissue was mainly extrahepatic at Day 7; intrahepatic pancreatic acini were detected in one fish at this age and were increasingly observed at Days 17 and 28 in association with afferent venous tracts. No vascular-biliary associations comparable to those described in adult guppies were observed. These findings establish a histological baseline for normal post-hatching liver development in guppies and provide a reference for future studies in comparative anatomy and of environmentally associated changes in liver structure during early life stages.
Segmental aplasia of the caudal vena cava is a rare variant, primarily reported in dogs. We describe herein a cat with this anomaly. The caudal vena cava was formed by confluence of the right and left common iliac veins and a common trunk of the right and left renal veins. The caudal vena cava continued to the right azygos vein and joined into the cranial vena cava. A confluence of hepatic veins drained into the right atrium as in the normal caudal vena cava. Detailed reports of venous variations are important for providing appropriate veterinary care.
The ichthyofauna of the lower Doce River basin has been exposed to multiple anthropogenic stressors. Among these, the collapse of the Fundão mining tailings dam in Mariana, Minas Gerais, Brazil, in 2015 resulted in massive fish mortality and widespread contamination of aquatic environments. In this context, morphological and histological analyses of gonadal development and larval malformations are valuable tools for assessing biological responses to environmental degradation. This study was designed as an ecosystem-level biomonitoring assessment involving native and non-native species to evaluate gonadal maturation stages (SGM), gonadal histopathology, and craniofacial deformities in fish larvae. Fish were collected from lakes, tributaries, reservoirs, and the main channel of the lower Doce River during rainy and dry seasons using gill nets and cast nets. Histological analyses revealed reproductive alterations, including accumulation of interstitial proteinaceous fluid, oocyte atresia, and yolk liquefaction in several species. Non-native species exhibited a higher frequency of spawned gonadal maturation stages than native species in the main channel of the Doce River and its tributaries. Morphological and histological analyses of the telencephalon and optic tectum of Pygocentrus nattereri and Prochilodus costatus larvae revealed tissue eversion and abnormal displacement of neural structures associated with craniofacial deformities. Histometric analyses demonstrated significantly higher nuclear intersection counts and reduced inter-nuclear distances in normal tissues compared with malformed tissues (p < 0.05). The occurrence of reproductive and neural alterations across multiple species suggests ecosystem-level biological impairment and highlights the value of fish assemblages as indicators of environmental quality in the lower Doce River basin.
Current understanding of the fascial structures within the human carotid sheath (CS) is largely based on static anatomical descriptions, with limited knowledge of their dynamic developmental process. This study aimed to characterise the developmental progression of the fascial architecture surrounding neurovascular components within the CS across four stages in the New Zealand White rabbit. Twenty New Zealand White rabbits were divided into four groups (n = 5 each): early foetal (Gestational Day 10), late foetal (Gestational Day 20), newborn (3 days postnatal) and adult (3-4 months). Whole transverse cervical sections were processed with H&E staining and α-SMA immunohistochemistry. In the rabbit, the common carotid artery, internal jugular vein and vagus nerve within the CS consistently exhibited a three-layered fascial organisation comprising an inner fascial layer, an intermediate zone and an outer fascial layer. The arterial inner fascia showed the earliest onset and most pronounced thickening, forming a dense multilayered fibrous structure, while the venous and neural inner fasciae remained comparatively thin. This differential thickening pattern corresponds to the varying levels of intrinsic pulsatile haemodynamic stress among the three structures. The outer fascial layers of adjacent structures showed potential fusion, likely reflecting extrinsic mechanical interactions from surrounding tissues. This study demonstrates a consistent three-layered fascial organisation within the CS across developmental stages, and these histomorphological findings are consistent with a possible role of dual mechanical influences in CS development.
This study evaluated histomorphometric and histochemical changes in the mare tuba uterina during different reproductive stages and under follicular cyst conditions. Forty nonpregnant mares were classified into follicular, luteal, post-ovulation and follicular cyst groups (n = 10/group). Histological evaluation of the isthmus, ampulla and infundibulum was performed using haematoxylin and eosin staining, while periodic acid-Schiff (PAS) staining was used to assess epithelial secretory activity. Morphometric parameters included number of primary mucosal folds, fold length, epithelial height and fold thickness. Descriptive observations indicated that the infundibulum possessed the most elaborate mucosal architecture, whereas the isthmus exhibited the simplest organization. Comparisons among reproductive stages were performed separately within each oviductal region. Across all oviductal regions, the follicular phase demonstrated the highest morphometric values, characterized by increased fold number, epithelial height and fold dimensions (p < 0.05). In contrast, most morphometric parameters decreased during the luteal and post-ovulation stages. For most variables, post-ovulation values remained higher than those observed during the luteal phase. The ampulla exhibited the strongest PAS reactivity during the luteal phase, with abundant apical PAS-positive granules indicating enhanced epithelial secretory activity, whereas moderate staining was observed during the follicular phase. Mares with follicular cysts showed the lowest morphometric values in all oviductal regions and weak, irregular PAS reactivity. These findings demonstrate that the mare tuba uterina undergoes pronounced cyclical remodelling influenced by ovarian status. Follicular cysts were associated with altered histological and secretory characteristics of the oviduct, which may compromise the physiological environment required for normal reproductive function.
In mammals, thigh muscles are compartmentalized into three groups: extensor, flexor, and adductor muscles, and these are innervated by the femoral nerve, sciatic nerve (tibial and common peroneal nerve divisions), and obturator nerve, respectively. However, amphibians show a different pattern of innervation. In this study, the extensor and flexor muscles, their innervation, and relation to the muscle compartment (by the lateral femoral intermuscular septum) were examined and noted in bullfrog thighs. Ten thighs of five bullfrog specimens were examined macroscopically and partially histologically. The extensor and flexor muscles were identified, and these two muscle groups were separated by the lateral femoral intermuscular septum in the dorsal thigh of bullfrogs. However, the nerve from the common peroneal nerve division of the sciatic nerve coursed dorsal to the ischiopubis and innervated both most of the extensor muscles (vastus lateralis, rectus femoris, and vastus intermedius muscles) and the flexor muscles, unrelated to the muscle compartment by the septum. Additionally, the vastus medialis muscle was innervated by the crural nerve (mammalian femoral nerve-like nerve) that coursed ventral to the ischiopubis. Thus, the extensor quadriceps femoris muscle is innervated by two types of nerves that take different routes to reach the muscles from the plexus. The innervating branches of the three extensor muscles are speculated to have been re-routed from the dorsal to the ventral side of the ischiopubis and merged into the crural nerve, thereby giving rise to the mammalian femoral nerve in the tetrapod evolutionary process. This nerve re-routing of the branches to the extensor muscles is presumably attributed to interspecific differences in hindlimb position and septum structure.
The morphogenesis of the diaphragm requires a coordinated development of different components with potential of malformation. Diaphragmatic herniation has rarely been reported in large animals and has not been described in a rhinoceros. An 8-day-old- female southern white rhinoceros calf was diagnosed with congenital diaphragmatic hernia with large parts of the intestine translocated in the thoracic cavity. Gross necropsy revealed bilateral Bochdalek hernia, severe damage of the intestinal tract and congestion of both lungs. Histologic findings demonstrated lung hypoplasia and severe pneumonia due to regurgitation and aspiration of nutritional components.
Polydactyly is a rare anomaly that has been described in many vertebrate species including several deer species. The case described in this communication is believed to be only the second documented example of additional metatarsae in roe deer (Capreolus capreolus). In addition to normally developed digits III and IV and the dewclaws, a right hind foot of an adult female from Germany had two additional digits lateral to digit V. Both originated from additional metatarsal elements. This case offers significant insights into the developmental plasticity of the cervid limb and extends the morphological spectrum of cervid polydactyly.
The distribution of amylin-like substances was investigated by immunohistochemistry in the pancreas of the Japanese eel (Anguilla japonica). Amylin-immunoreactive cells were observed in pancreatic islets. These immunostaining profiles were not observed by the preabsorption of the anti-amylin serum with synthetic amylin, indicating that the serum specifically recognized eel amylin-like peptide. Almost all amylin-immunoreactive cells were immunopositive for peptide YY, suggesting that amylin and peptide YY co-secreted from the islet cells might participate in the modulation of insulin and glucagon secretion in the pancreatic islets. In addition, weakly glucagon-immunopositive cells, but not densely glucagon-immunopositive cells, also corresponded to amylin-immunoreactive cells. The subpopulation of glucagon-immunoreactive and glucagon-like peptide-1-immunoreactive cells was also immunopositive for peptide YY. These results suggest that amylin and peptide YY, and also presumably glucagon-like peptide-1, are co-secreted from the amylin/peptide YY cells, and these three peptides modulate food intake through the central nervous system in addition to intrainsular functions.
Anatomical variations of the left gastric artery (LGA) and right gastric artery (RGA) are clinically relevant for gastric surgery and endovascular interventions. This study aimed to characterize the origin, anatomical distribution and morphometric features of the LGA and RGA using 64-slice computed tomography (CT). A cross-sectional descriptive study was conducted on 385 individuals who underwent contrast-enhanced abdominal CT at Binh Dan Hospital between September 2024 and April 2025. The LGA originated from the celiac trunk in 91.9% of cases and was most frequently located between the lower one-third of T12 and the upper one-third of L1 (> 61%). Its mean diameter and length were 2.7 ± 0.3 mm and 30.3 ± 9.3 mm, respectively, with the Type I branching pattern predominating, characterized by branches supplying the oesophagus, gastroesophageal junction and the lesser curvature. The mean distance from the abdominal aorta to the LGA was 19.6 ± 6.1 mm. The RGA was identified in 88.3% of cases and most commonly arose from the proper hepatic artery (72.9%), with a mean diameter of 1.6 ± 0.2 mm. An arterial arcade along the lesser curvature was observed in 81.3% of cases. These findings provide quantitative anatomical data that may support accurate identification of vascular landmarks during gastric surgery and facilitate appropriate catheter selection for endovascular procedures involving the LGA and RGA.
The vertebrate eye, while commonly perceived as a soft-tissue structure, is reinforced in numerous taxa by an internal ocular skeleton composed of scleral cartilage and ossicles. This manuscript presents a histological case report documenting scleral cartilage in the Himalayan Golden Eagle (Aquila chrysaetos daphanea) and integrates these findings with a comprehensive synthesis of current understanding of the ocular skeleton's evolution, development and functional morphology. These findings are consistent with previously described avian scleral architecture. Although based on a single specimen, the study contributes additional histological observations for a large raptor species and provides a comparative perspective on vertebrate ocular skeletal organization. We demonstrate that the ocular skeleton is not merely a passive structural component but a dynamic, highly plastic system that has actively enabled visual radiations in response to distinct ecological demands. Histological examination of the eagle eye revealed a well-developed scleral stroma containing hyaline cartilage extending from the optic nerve posteriorly to the corneoscleral limbus anteriorly, consistent with the avian scleral cartilage sensu stricto cup morphology. By integrating ecological drivers of visual performance with comparative anatomy and developmental biology, we construct a unified model revealing how birds and teleosts leveraged homologous ancestral cartilage to solve fundamentally different biomechanical challenges: optical precision under accommodation-induced pressure in air versus hydrodynamic integrity during high-speed locomotion in water.
The equine cervical intervertebral foramina (IVF) represent vital anatomical regions facilitating the passage of spinal nerves and associated vasculature. An in-depth understanding of their anatomy is imperative for the safe implementation of diagnostic and surgical interventions. Despite their clinical significance, anatomical descriptions of the equine cervical IVF remain under-characterised in the existing literature, particularly in relation to the needs of equine veterinary surgeons. Our study provides comprehensive anatomical analysis of the IVF at the cervical vertebral levels C5/C6 and C6/C7 in the domestic horse (Equus caballus), targeting advancing clinical methodologies pertinent to cervical foraminotomy procedures. A series of anatomical dissections on equine cadavers' necks was performed to comprehensively evaluate the external musculature and establish contextual orientation, subsequently leading to more intricate dissections and descriptions. This study aimed to undertake descriptive anatomical dissections of the C5/C6 and C6/C7 IVF, employing direct observation of clinical and surgical importance. Data analysis included visual documentation with development of annotated diagrams to elucidate the spatial relationships between skeletal, muscular, neural, and vascular structures within and surrounding the C5/C6 and C6/C7 foramina. The results present a final, sequential, detailed anatomical characterisation of the IVF at the specified cervical levels, highlighting morphological descriptions, structural orientation, and adjacent tissue planes. Critical features relevant to clinical practice are delineated, notably the proximity of neurovascular structures to bony landmarks frequently encountered during surgical interventions. The descriptive anatomy in this study provides novel anatomical interpretations of the equine cervical IVF region and advocates for safer, evidence-based clinical practices in managing conditions that require clinical and surgical interventions.
The blood-spleen barrier (BSB) is essential for filtering blood-borne particles, removing damaged erythrocytes, and initiating immune responses. Therefore, this study aimed to investigate the location, structural components, and functional implications of the BSB in fruit bats (Cynopterus titthaecheilus and Rousettus leschenaultii) using intravenous India ink injection as a tracer. A total of seven wild-caught bats were examined histologically after splenic sampling and staining with haematoxylin-eosin, toluidine blue, and Masson's trichrome. Carbon particles were distributed in several splenic compartments, but the highest accumulation occurred in the marginal zone, ellipsoid, and periellipsoidal lymphoid sheaths, suggesting these regions as the principal BSB sites. Additional deposits in the splenic cord and sinus reported further downstream filtration within the red pulp. Carbon residues were also observed in the white and red pulp, suggesting continued inclusion in specific immune induction and phagocytic clearance after primary filtration. The splenic microcirculation of both species comprised open and closed pathways. The results showed that fruit bat spleen possessed a well-developed BSB centered in the marginal zone ellipsoid-PELS complex, with subsequent processing in red pulp structures, supporting integrated innate and adaptive immune defence against blood-borne material. The understanding of splenic filtration architecture was also refined in chiropteran mammals.
This study describes the gross anatomy and histological organization of the digestive tract of the mudskipper Scartelaos histophorus from the Mekong Delta, Vietnam. Thirty adult specimens were collected from intertidal mudflats, and the digestive tract was examined using gross anatomical observation and routine paraffin histology with haematoxylin and eosin staining. Gross anatomical observation differentiated the digestive tract into the oesophagus, stomach, intestine and rectum, whereas histological examination focused on the stomach, intestine and rectum. The stomach was characterized by prominent mucosal folds, a well-developed lamina propria and numerous gastric glands. These features provide strong histological evidence for the presence of a glandular stomach in S. histophorus. The intestinal mucosa formed long and slender folds lined by columnar epithelial cells and mucus-secreting cells, whereas the rectum showed shorter mucosal folds and a comparatively thick muscular layer. The regional differentiation of the stomach, intestine and rectum suggests structural specialization of the digestive tract in relation to the omnivorous feeding habit of this amphibious fish. These findings provide the first histological description of the main digestive regions in S. histophorus and contribute to comparative knowledge of digestive morphology within Oxudercidae.
Marsupials lack a corpus callosum; in its place Diprodontia have a fasciculus aberrans connecting the hemispheres. However, despite this uniqueness, the realm of marsupial brain anatomy remains largely unexplored, especially through the lens of modern imaging techniques. Currently, there is a glaring absence of publicly available reference materials to explore normal brain morphometry to aid in defining and investigating marsupial neurodegenerative brain diseases. This study segmented magnetic resonance images of a wombat brain with an overall size of 41,745.46 mm3 to create a three-dimensional atlas. The volume and ratio to the overall brain size of each segment were quantified. The common wombat has a moderate hippocampal formation (2464.34 mm3; 5.90%), thick hippocampal commissure (535.19 mm3; 1.28%), well-developed tectum (481.42 mm3; 1.15% and a large epithalamus; 53.96 mm3; 0.13%). The common wombat's moderately sized cerebellum (5181.99 mm3; 12.41%) with prominent folia and fissures but less folding may suggest the low need for complex motor movement when burrowing. The common wombat also has a large diencephalon (3104.70 mm3; 7.44%), large thalamus (2206.81 mm3; 5.29%), a moderately sized hypothalamus (530.71 mm3; 1.27%), moderately sized basal ganglia (caudoputamen) (1345.26 mm3; 3.22%) and moderately sized pons and medulla (2475.26 mm3; 5.93%).
The mature rat adrenal medulla is characterized by a pronounced asymmetry in the 3D organization of chromaffin tissue as a whole and by oppositely directed gradients in the distribution of adrenaline-storing (A-) and noradrenaline-storing (NA-) cells. The aim of this study was to characterize the 3D organization of the rat maturing adrenal medulla. Adrenal glands from 1- to 2-week-old Wistar rats were processed using a highly specific chromaffin reaction according to Honoré, which allows differentiation between A- and NA-cells. A 3D reconstruction of the adrenal medulla was obtained from complete sets of serial sections after A- and NA-cells, blood vessels, nerve fibres, neurons and stroma had been marked on each section. By the time of final differentiation of A- and NA-cells (end of the first postnatal week), the two-level asymmetry of chromaffin tissue characteristic of the mature adrenal medulla and its close association with bundles of nerve fibres was already clearly evident. At the craniomedial margin, where the main nerve bundles enter the medulla, chromaffin tissue formed cones and cords composed almost exclusively of A-cells, whereas towards the caudolateral margin A-cell density decreased and NA-cell density increased. Integrating these data with published information on embryonic migration of sympathoadrenal precursors and on the development of adrenal medullary innervation and vascularization, we propose the 'access points' hypothesis. It proposes that opposite A- and NA-cell gradients result from asynchronous arrest of migrating groups of A- and NA-cell precursors (chromaffinoblasts) as they reach discrete microdomains that provide access to nerve terminals and microvasculature ('access points'), with earlier-settling A-blasts accumulating near the nerve entry zone and later-settling NA-blasts occupying remaining access points.
Accessory bones are generally considered to be developmental anomalies consisting of unfused ossification centers. These ossicles, which have no clearly defined function, can become infected and dislocated and can also be confused with avulsion fractures. In this study, we aimed to determine the morphometric characteristics and frequency of accessory bones in the foot. Foot computed tomography (CT) images (187 right, 213 left) of 400 individuals (239 men and 161 women) aged 18-86 years who underwent foot CT scans for various reasons were retrospectively reviewed. The surface area and the long and short diameters of the accessory bones were measured and recorded. Of the 400 ft, 270 (67.5%) had at least one accessory bone. The incidence was 57.6% in younger individuals, increasing to 81.4% in older individuals. 2.75% of accessory bones were bipartite. The most common were the accessory navicular bone (41.5%), os trigonum (14%) and os peroneum (13%). One accessory bone was identified that was not described in the available literature. Accessory bones have been proven to be quite common and may increase further in older age groups. The morphometric data obtained and the discovered accessory bone can contribute to the literature and guide clinicians in the diagnosis of related foot pathologies.
Panga (Pangasionodon hypophthalmus) is a freshwater fish with increasing production and consumption worldwide. However, the knowledge concerning the nutrition, food management and reproduction in male fish is still scarce, especially regarding the interaction between different protein levels in commercial diets and the reproductive process during gonadal maturation. Thus, the current study aimed to characterise the gonadal and sperm morphology of male P. hypophthalmus fed with two crude protein (C.P.) levels (28% and 36%) in commercial feed. For this, for three months, 50 male specimens were distributed in two excavated tanksand fed with commercial feed with 28% and 36% C.P. The gonads were removed and evaluated by macroscopic, microscopic, histological assessment of the testicular parenchyma and ultrastructural analysis of sperm by Scanning Electron Microscopy. Results showed that fish fed with 36% C.P. had greater testicular weight and gonadosomatic index (GSI) than those fed with 28% C.P. Both crude protein levels contributed to the gonadal maturation of the panga. Fish fed both diets showed similar gonadal and spermatic morphology. However, fish fed with 36% C.P. presented better reproductive performance in terms of total testicular mass gain and GSI parameters compared to fish fed with 28% C.P. Overall, nutritional management with different C.P. levels could contribute to the increase in the reproductive performance of P. hypophthalmus.
The ovary of mammals is a unique organ that is characterized by morphological tissue rearrangements, which include the development and death of germ cells, alongside the development and atresia of follicles. Additionally, the initiation of meiosis in germ cells, the development of follicles, and the onset of puberty likely involve cellular mechanisms such as autophagy. Despite some knowledge has been gained, there remains a gap in understanding the precise role of autophagy in these processes, particularly with the emergence of a specific variant termed mitophagy in reproductive sciences. In addition to its role in regulating energy metabolism and maintaining cellular homeostasis, autophagy can either facilitate cell survival or induce cell death. Considering the critical time points during female gonad development where autophagy may be involved in various cellular processes, we assessed the ultrastructural and histological characteristics of autophagy. This evaluation included Beclin-1 immunodetection as an autophagy marker in the embryonic ovary of female mice at 13.5 days post coitum, as well as in ovaries collected from newborns at 1 postnatal day and prepubertal at 21 postnatal days. The study revealed ultrastructural features of autophagy and mitophagy in embryonic and neonatal germ cells, as well as in follicular development and atresia in the ovaries of prepubertal mice. This process was confirmed by the detection of Beclin-1 protein expression. Moreover, our findings indicate a heightened level of Beclin-1 immunodetection in the oocytes of preantral and antral atretic follicles, which was correlated with the progress of atresia.
Passive stabilisers of the canine shoulder joint include the articular surfaces, glenoid labrum, joint capsule and glenohumeral ligaments, in functional entity with the biceps brachii tendon. Their anatomical description differs widely. This explorative study aimed to screen a heterogeneous group of dogs on variations of these structures. Twenty-three canine forelimbs were dissected. The glenoid cavity outlines, their circularity values, and the configuration of the glenoid labrum and ligaments were recorded, as well as their relationship to the biceps brachii tendon. The shape of the glenoid cavity differed between dogs and left/right limb (circularity 0.73-0.83). A protruding, fibrocartilaginous labrum was present caudolaterally in 45% of the limbs. The medial glenohumeral ligament occurred in all dogs, in three shape variants. The lateral ligament was present in few dogs. Between the joint socket and the ligaments or 15% of the biceps brachii tendons was a synovium-lined space. More frequently, the gap between tendon and joint socket was filled with loose connective tissue. There was no clear relation between size, body condition score and muscle mass of the dog and occurrence of variants of the analysed structures. The biomechanical implications of the individual variants still need to be studied.
