Morphological investigation of the gills of the dusky grouper Epinephelus marginatus (Lowe 1834) using gross anatomy and scanning electron microscopy

Macroscopic, microscopic, and immunofluorescent characterization of the Greek tortoise (Testudo graeca graeca) oropharyngeal floor with concern to its feed adaptation as a herbivorous land reptile

The current investigation focuses on gross anatomy, light, and scanning electron microscopy (SEM) of the Testudo graeca oropharyngeal floor, with particular reference to the immunofluorescence technique to examine its tongue. The T. graeca oropharyngeal floor showed many anatomical structures: the lower rhamphotheca, paralingual ridge, lower alveolar ridge, tongue, laryngeal mound, and glottis. The lower rhamphotheca appeared as a V-shaped jaw line with a highly serrated edge and a median tomium (beak). SEM observations of the lingual apex and the lingual body showed rectangular and conical filiform papillae with porous surfaces and taste pores. Meanwhile, the lingual root had two wings that carried papillae with different shapes: dagger-shaped, conical, bifurcated, and leaf-like papillae, and these papillae lacked taste pores. The laryngeal mound had openings for the laryngeal mucus gland and its secretions. Light microscopy findings showed mucous glands in the propria submucosa and near the mucosal surface of the lingual apex. The lingual root had lingual papillae and two hyaline cartilaginous skeletons between skeletal muscles, and the lingual papillae were elongated filiform, rectangular filiform papillae, and fungiform papillae. The lamina propria constituted the core of the lingual papillae and the mucous gland, they had a positive reaction with the periodic acid schiff (PAS) reagent. The apical surface of the fungiform papillae had taste pores. Under immunofluorescence, the vimentin was detected in taste bud cells, and synaptophysin reacted to the taste buds and nerve bundles. The current study of the Greek tortoise oropharyngeal floor investigated its herbivorous eating habits using its serrated lower rhamphotheca, a large tongue with differently shaped papillae, and numerous mucous glands. RESEARCH HIGHLIGHTS: The Greek tortoise (T. graeca graeca) oropharyngeal floor showed many anatomical structures: lower rhamphotheca, paralingual ridge, lower alveolar ridge, tongue, laryngeal mound, and glottis. SEM and light microscopy observations of the tongue revealed varied types and shapes of lingual papillae with a porous surface on the tongue apex (rectangular or conical filiform papillae), on the tongue body (filiform and fungiform papillae), and on the tongue root (dagger-shaped, conical, bifurcated, and leaf-like papillae). Light microscopy findings: the lamina propria constituted the core of the lingual papillae and had numerous mucous glands that had a slightly magenta-red color with PAS reagent. The apical surface of the fungiform papillae had taste pores. Vimentin and synaptophysin gave a reaction to the taste buds.

A new insight for investigating the prenatal and postnatal ossification centers of pelvic and femur bones in white New Zealand rabbits (Oryctolagus cuniculus) using 3D CT, double stain technique, and morphometry

BACKGROUND

The ossification centers in rabbit limbs are related to fetal age and bone maturation.

OBJECTIVE

To address the limited studies on ossification in the hind limbs of New Zealand rabbits, we investigated the prenatal and postnatal development of the pelvic and femur bones.

METHODS

Double staining with Alcian Blue and Alizarin Red, computed tomography (CT), and 3D reconstruction were employed to visualize and analyze ossification centers in detail.

RESULTS

Using double staining, we observed these patterns: At prenatal days 18 and 21, ossification centers appeared in the ilium. By prenatal days 23 and 25, ossification began in the ischium. On postnatal day 1, ilium ossification centers spread across most of the ilium wings, except for the iliac crest, and new centers appeared in the pubis and cotyloid bones. Most bones had ossified by the third week and one month postnatal, except for the iliac crest and ischial tuberosity. At 1.5 months, both were fully ossified. On day 18 post coitum, an ossification center was visible in the middle of the femur shaft. By day 28 post coitum, ossification extended through the shaft, and postnatally, new ossification spots appeared at the extremities by day one and week one. By the third week, complete ossification of the femur head, lesser trochanter, third trochanter, medial condyle, and lateral condyle was observed. At 1.5 months, the entire proximal extremity was ossified.

CONCLUSION

3D CT provided clear imaging of ossification progression in the pelvic and femur bones. This study enhances our understanding of vertebrate skeletal development.

A novel immunofluorescence study of Lingual Salivary Glands in the Egyptian Tortoise (Testudo kleinmanni) and its ecological significance

The Egyptian tortoise (Testudo kleinmanni) is remarkably adapted to its harsh desert environment, a characteristic that is crucial for its survival under extreme conditions. This study was aimed at providing a deeper understanding of the lingual salivary gland structures in the Egyptian tortoise and examining how these structures help the tortoise manage hydration and nutrition in arid conditions. Utilizing a combination of light microscopy and immunofluorescence, this research introduced pioneering methods involving seven different antibodies, marking a first in the study of reptilian salivary glands. Our investigations categorized the tortoise's salivary glands into papillary and non-papillary types. The papillary glands were further classified into superficial, deep, interpapillary, and intraepithelial salivary glands, while non-papillary glands included superficial and deep lingual types. Structurally, these glands are organized into lobules, delineated by interlobular septa, and are equipped with a duct system comprising interlobular, intercalated, and main excretory ducts with gland openings on the tongue's surface and the papillae surfaces. Notably, the superficial glands displayed both tubuloalveolar and acinar configurations, whereas the deep lingual glands were exclusively acinar. Immunofluorescence results indicated that α-smooth muscle actin (α-SMA) was prevalent in myoepithelial cells, myofibroblasts, and blood vessels, suggesting their integral role in glandular function and support. E-cadherin was predominantly found in epithelial cells, enhancing cell adhesion and integrity, which are critical for efficient saliva secretion. Importantly, Mucin 1 (MUC1) and Mucin 5B (MUC5B) staining revealed that most glands were mucous in nature, with MUC5B specifically marking mucin within secretory cells, confirming their primary function in mucous secretion. PDGFRα and CD34 highlighted the presence of telocytes and stromal cells within the glandular and interlobular septa, indicating a role in structural organization and possibly in regenerative processes. Cytokeratin 14 expression was noted in the basal cells of the glands, underscoring its role in upholding the structural foundation of the epithelial barrier. In conclusion, this detailed morphological and immunological characterization of the Egyptian tortoise's salivary glands provides new insights into their complex structure and essential functions. These findings not only enhance our understanding of reptilian physiology but also underline the critical nature of salivary glands in supporting life in arid environments. This study's innovative use of a broad range of immunofluorescence markers opens new avenues for further research into the adaptive mechanisms of reptiles.

Macro- and micro-morphological comparison of the detailed structure of the oral cavity roof in two different feeding habits marine fishes: Pagrus pagrus and Boops boops

The feeding habits and habitats of fish influence the morphology of the oral cavity. This study used gross anatomy, light microscopy, and scanning electron microscopy, in addition to morphometric analysis, to investigate the anatomical characteristics of the oral cavity roof in Pagrus pagrus and Boops boops, which have different dietary habits. The oral cavity roof appeared U-shaped and divided into the palate and upper pharyngeal regions. The upper lip of P. pagrus was broad, while B. boops' upper lip was small and thin. Both species had a stratified squamous epithelium with an irregular shape and a folded surface. P. pagrus had a horseshoe-shaped upper velum with a high middle part, and its surface resembled sea waves with obvious mucous-secreting openings with cilia and many folds and grooves between them. B. boops's upper velum was thin and appeared as a triangle pouch with a pointed cranial apex. The palate in both species was narrow in the front and increased in width backward until it ended. The upper pharyngeal teeth in P. pagrus appeared as two patches, separated by a median longitudinal ridge and an anterior V-shape separator. Meanwhile, in B. boops, they appeared as a ball patch on both sides and a separator ridge in the middle. Because P. pagrus fed on harder structures than B. boops, their feeding habits were reflected in the structure of the oral cavity roof. P. pagrus, a carnivorous species, had several rows of sharp upper jaw and upper pharyngeal teeth, thick spinous tubercles on oblique transverse ridges, and massive mucous glands. On the other hand, B. boops, an omnivorous species, had only one row of upper jaw teeth, a few upper pharyngeal teeth scattered on two oval patches, and thin filaments on the oblique transverse ridges.

Scanning electron microscopy and morphometric analysis of the hair in dromedaries with SEM-EDX in relation to age

BACKGROUND

Hair characterization is critical for determining animal individuality throughout life. This study aimed to assess the morphological features of dromedary camel hair in relation to age.

MATERIALS AND METHODS

Hair samples were obtained from the camel humps of 30 dromedary camels separated into three groups: G1 (n:10) aged one-year, G2 (n:10) aged 3-5 years, and G3 (n:10) at the age of 8-10 years. The hair was examined using light microscopy, SEM, and SEM-EDX.

RESULTS

The Maghrebi camel had varied medulla patterns and structures across the ages. In the G1 group 75% had continuous medulla patterns and amorphous medulla structures, compared to 70% in G2, and 90% in G3. The medulla index increased with age, rising from 0.3 to 0.77%. The shaft width grew in size from G1 to G2, then fell to approximately one-third of the G2 size at G3. The cortex and cuticle widths were also determined by age, and they increased in the G1 compared to G3 camels. The shape of the cuticle scales in G1 camels was wavy, like mountain tops with irregular edges, within G2 camels the scales were particularly long, oval-shaped scales with smooth, wavy borders. The scales of the older G3 camels were quite long and rectangular. SEM-EDX spectra recognized carbon, oxygen, nitrogen, sulfur, calcium, aluminum, silicon, and potassium at the medulla and cortex. Sulfur levels were highest in the G2 samples but lowest in the G1 samples.

CONCLUSION

The dromedary camel's hair structure and mineral content, particularly carbon and nitrogen, differed as camels aged.

Comparative morphological analysis of telson and uropods in Penaeus canaliculatus (Olivier, 1811), Penaeus semisulcatus (De Haan, 1844), and Metapenaeus stebbingi (Nobili, 1904) using scanning electron microscopy and EDX analysis

The telson and uropods collectively form the tail fan, playing crucial roles in locomotion, buoyancy, defense, and respiration. We aimed to compare telson and uropod structures in three shrimp species-Penaeus canaliculatus, Penaeus semisulcatus, and Metapenaeus stebbingi-to identify the species with the most robust telson for its environment. Our analysis involved morphological measurements and scanning electron microscopy (SEM), supplemented by a novel approach-Energy-Dispersive X-ray (EDX) spectroscopy, a technique not previously utilized in studies on these three species. M. stebbingi exhibited the longest telson length, whereas P. semisulcatus had the longest uropod. P. canaliculatus featured a single pair of fixed spines, while P. semisulcatus had evenly spaced small conical spines along the sides of the median elevation and groove. A distinctive feature of M. stebbingi was the telson, which had three pairs of large spines. Diverse setae on telsons included simple, unipennate, and plumose setae. Notably, specialized branched tubular setae on uropods' endopods may aid in grooming or swimming behavior. EDX spectroscopy revealed that the telson cuticle primarily consists of carbon, nitrogen, and oxygen, with significantly high concentrations alongside comparatively lower calcium and phosphorous concentrations. P. semisulcatus exhibited the highest calcium and phosphorus content among the three species. In conclusion, M. stebbingi's telson is structurally robust, emphasizing the importance of morphology, while P. semisulcatus demonstrated a hard telson through EDX analysis. Our study underscores not solely relying on morphology for telson strength assessment but considering telson composition. These variations among species may be attributed to diverse ecological and physiological adaptations.

Microscopic Focus on the Thyroid Follicles of the One-Humped Camel (Camelus dromedarius)

The microstructure of the thyroid gland of the one-humped camel (Camelus dromedarius) was described using morphometric, histological, immunohistochemical staining, and ultrastructural standard techniques. The follicular secretory units of the thyroid glands displayed comparable and variable sizes where the large follicles were situated at the peripheral margins; however, the small ones were located in the central region. Semisquamous epithelium (low cuboidal) lined the large thyroid follicles, while high cuboidal (columnar) epithelium lined the small ones. Our electron microscopic findings revealed that the low-sized cuboidal follicular cells lack organelles and are hypoactive. The high cuboidal follicular cells are active cells and rich in cellular organelles such as cisternae of rough endoplasmic reticulum, mitochondria, colloid droplets, scrolled Golgi apparatus, and secretory vesicles. A few degenerate follicular cells appeared on rare occasions. The parafollicular cells appeared with a more prominent and conspicuous nucleus than the follicular cells. The follicular cells were classified as active, inactive, or degenerated using transmission electron microscopy. The follicular and parafollicular cells showed calcitonin-positive immunoreactivity. Overall, the presented results showed particular convergences of the morphostructural aspects of the thyroid gland of C. dromedarius to that of other mammals with some distinctive features to cope with their physiology and harsh niche.

Investigating the role of Purkinje fibers and synaptic connectivity in balance regulation through comprehensive ultrastructural and immunohistochemical analysis of the donkey's (Equus asinus) cerebellum

The donkey's extraordinary capacity to endure substantial loads over long distances while maintaining equilibrium suggests a distinctive cerebellar architecture specialized in balance regulation. Consequently, our study aims to investigate the intricate histophysiology of the donkey's cerebellum using advanced ultrastructural and immunohistochemical methodologies to comprehend the mechanisms that govern this exceptional ability. This study represents the pioneering investigation to comprehensively describe the ultrastructure and immunohistochemistry within the donkey cerebellum. Five adult donkeys' cerebella were utilized for the study, employing stains such as hematoxylin, eosin, and toluidine blue to facilitate a comprehensive histological examination. For immunohistochemical investigation, synaptophysin (SP), calretinin, and glial fibrillary acidic protein were used and evaluated by the Image J software. Furthermore, a double immunofluorescence staining of SP and neuron-specific enolase (NSE) was performed to highlight the co-localization of these markers and explore their potential contribution to synaptic function within the donkey cerebellum. This investigation aims to understand their possible roles in regulating neuronal activity and synaptic connectivity. We observed co-expression of SP and NSE in the donkey cerebellum, which emphasizes the crucial role of efficient energy utilization for motor coordination and balance, highlighting the interdependence of synaptic function and energy metabolism. The Purkinje cells were situated in the intermediate zone of the cerebellum cortex, known as the Purkinje cell layer. Characteristically, the Purkinje cell's bodies exhibited a distinct pear-like shape. The cross-section area of the Purkinje cells was 107.7 ± 0.2 µm2 , and the Purkinje cell nucleus was 95.7 ± 0.1 µm2 . The length and diameter of the Purkinje cells were 36.4 × 23.4 µm. By scanning electron microscopy, the body of the Purkinje cell looked like a triangular or oval with a meandrous outer surface. The dendrites appeared to have small spines. The Purkinje cells' cytoplasm was rich with mitochondria, rough endoplasmic reticulum, ribosomes, Golgi apparatus, multivesicular bodies, and lysosomes. Purkinje cell dendrites were discovered in the molecular layer, resembling trees. This study sheds light on the anatomical and cellular characteristics underlying the donkey's exceptional balance-maintaining abilities.

A comprehensive exploration of diverse skin cell types in the limb of the desert tortoise (Testudo graeca) through light, transmission, scanning electron microscopy, and immunofluorescence techniques

The Greek tortoise, inhabiting harsh desert environments, provides a compelling case for investigating skin adaptations to extreme conditions. We have utilized light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and immunofluorescence analysis to describe the structure of the arid-adapted limb skin in the Greek tortoise. Our aim was to identify the cell types that reflect the skin adaptation of this tortoise to arid conditions. Utilizing seven antibodies, we localized and elucidated the functions of various skin cells, shedding light on how the tortoise adapts to adverse environmental conditions. Our findings unveiled numerous scales on the limbs, varying in size and color, acting as protective armor against abrasions, bites, and other potential threats in their rocky habitats. The epidermis comprises four layers: stratum basalis, stratum spinosum, peri-corneous layer, and stratum corneum. Cytokeratin 14 (CK14) was explicitly detected in the basal layer of the epidermis, suggesting a role in maintaining epidermal integrity and cellular function. Langerhans cells were observed between epidermal cells filled with ribosomes and Birbeck granules. Numerous dendritic-shaped Langerhans cells revealed through E-Cadherin signify strong immunity in tortoises' skin. Melanophores were identified using the Melan-A antibody, labeling the cytoplasm, and the SOX10 antibody, labeling the nucleus, providing comprehensive insights into melanophores morphology and distribution. Two types of melanophores were found: dendritic below the stratum basalis of the epidermis and clustered oval melanophores in the deep dermal layer. Varied melanophores distribution resulted in a spotted skin pattern, potentially offering adaptive camouflage and protection against environmental challenges. Numerous myofibroblasts were discerned through alpha-smooth actin (α-SMA) expression, indicating that the Greek tortoise's skin possesses a robust tissue repair and remodeling capacity. B-cell lymphocytes detected via CD20 immunostaining exhibited sporadic distribution in the dermis, concentrating in lymphoid aggregates and around vessels, implying potential roles in local immune responses and inflammation modulation. Employing Tom20 to identify skin cells with abundant mitochondria revealed a notable presence in melanophores and the basal layer of the epidermis, suggesting high metabolic activity in these cell types and potentially influencing cellular functions. These findings contribute to our comprehension of tortoise skin anatomy and physiology, offering insights into the remarkable adaptations of this species finely tuned to their specific environmental habitats.

The tongue of the red-eared slider (Trachemys scripta elegans): morphological characterization through gross, light, scanning electron, and immunofluorescence microscopic examination

The red-eared slider (Trachemys scripta elegans) is renowned for its remarkable adaptations, yet much of its complex biology remains unknown. In this pioneering study, we utilized a combination of gross anatomy, scanning electron microscopy (SEM), light microscopy, and immunofluorescence techniques to examine the tongue's omnivorous adaptation in this species. This research bridges a critical knowledge gap, enhancing our understanding of this intriguing reptile. Gross examination revealed a unique arrowhead-shaped tongue with a median lingual fissure and puzzle-piece-shaped tongue papillae. SEM unveiled rectangular filiform, conical, and fungiform papillae, with taste pores predominantly on the dorsal surface and mucous cells on the lateral surface of the papillae. Histologically, the tongue's apex featured short rectangular filiform and fungiform papillae, while the body exhibited varying filiform shapes and multiple taste buds on fungiform papillae. The tongue's root contained lymphatic tissue with numerous lymphocytes surrounding the central crypt, alongside lingual skeletal musculature, blood and lymph vessels, and Raffin corpuscles in the submucosa. The lingual striated muscle bundles had different orientations, and the lingual hyaline cartilage displayed a bluish coloration of the ground substance, along with a characteristic isogenous group of chondrocytes. Our research represents the first comprehensive application of immunofluorescence techniques to investigate the cellular intricacies of the red-eared slider's tongue by employing seven distinct antibodies, revealing a wide array of compelling and significant findings. Vimentin revealed the presence of taste bud cells, while synaptophysin provided insights into taste bud and nerve bundle characteristics. CD34 and PDGFRα illuminated lingual stromal cells, and SOX9 and PDGFRα shed light on chondrocytes within the tongue's cartilage. CD20 mapped B-cell lymphocyte distribution in the lingual tonsil, while alpha smooth actin (α-SMA) exposed the intricate myofibroblast and smooth muscle network surrounding the lingual blood vessels and salivary glands. In conclusion, our comprehensive study advances our knowledge of the red-eared slider's tongue anatomy and physiology, addressing a significant research gap. These findings not only contribute to the field of turtle biology but also deepen our appreciation for the species' remarkable adaptations in their specific ecological niches.

Gill arch and raker morphology of common carp (Cyprinus carpio, Linnaeus, 1758) sampled in aquaculture system

The study aimed to investigate the morphologic aspects of common carp's gill arch and gill rakers (Cyprinus carpio, Linnaeus, 1758), an omnivore and highest-produced aquaculture species. The study used 10 common carp (395.35 ± 45.06 g) grown entirely under aquaculture conditions. The fish tissues were fixed with Glutaraldehyde (2.5%) for scanning electron microscopy and with formalin (10%) for stereomicroscopic examination. In the SEM examination, two types of taste papillae (Type II and Type III) were observed in the pharyngeal mucosa. Microridge-like structures in the epithelial layer were found to have two forms. The study findings indicate a significant decrease in gill arch lengths from cranial to caudal and a significant increase in rakers per unit area, as determined through digital calliper measurements and stereomicroscopic examinations (p < 0.05). However, there was no significant difference in measurements of gill arches and raker numbers between the bilateral symmetry of the gill arches (p > 0.05). In conclusion, it was observed that the epithelial structure on the common carp gill arch contained two types of microridge-like structures: the gill arch length decreased from cranial to caudal, and the rake density on these arches increased caudally.

Unveiling Cellular Diversity in the Buffalo Corneal Stroma: Insights into Telocytes and Keratocytes Using Light Microscope, Transmission Electron Microscope, and Immunofluorescence Analysis

Telocytes and keratocytes are important cells that maintain the structure and function of the cornea. The buffalo cornea, known for its resilience in harsh conditions, has not been extensively studied regarding the presence and role of telocytes and keratocytes. We used light microscopy, transmission electron microscopy (TEM), and immunofluorescence assays with platelet-derived growth factor receptor alpha (PDGFRα), CD34, and Vimentin markers to investigate their expression and localization in the cornea. TEM analysis confirmed the presence of spindle-shaped keratocytes with intercellular connections, while telocytes exhibited small spindle-shaped bodies with long, thin branches connecting to corneal keratocytes. Immunofluorescence findings showed that CD34 was more abundant near the endothelium, Vimentin was prominently expressed near the epithelium, and PDGFRα was uniformly distributed throughout the corneal stroma. Co-expression of CD34 and Vimentin, PDGFRα and Vimentin, as well as CD34 and PDGFRα, was observed in keratocytes and telocytes within the stroma, indicating the potential presence of mesenchymal cells. These results suggest the involvement of telocytes and keratocytes in corneal wound healing, transparency maintenance, and homeostasis. The co-expression of these markers highlights the critical role of telocytes and keratocytes in regulating corneal physiological functions, further enhancing our understanding of corneal biology in the buffalo model.

New insights into the retinal microstructure-diurnal activity relationship in the African five-lined skink (Trachylepis quinquetaeniata) (Lichtenstein, 1823)

BACKGROUND

The retinae of diurnal vertebrates have characteristics. Most lizards are strictly diurnal, and their retinal morphology is still unknown.

MATERIALS AND METHODS

The retina of the African five-lined skink (Trachylepis quinquetaeniata) was studied using light and transmission electron microscopy.

RESULTS

The retina's ten layers were all detected. The inner nuclear layer was the thickest by an average of 67.66 μm, and the inner plexiform layer was 57.564 μm. There were elliptical, long cylindrical, and spherical melanosomes (small and large) in the pigment epithelial layer of the retina. The cylindrical melanosomes had a large area on the lateral surfaces of cones to increase light scatter absorption. The photoreceptor layer of the retina had cones only. There were single and double cones, with the double cones consisting of principal and accessory cones. The cones had inner and outer segments separated by oil droplets. A spherical paraboloid body existed between the limiting membrane and the ellipsoid. All single cones had a paraboloid, and double cones had a large paraboloid in the accessory cone. The presence of paraboloids and large ellipsoids with mitochondria of varying sizes may have helped focus the light on cone segments.

CONCLUSION

The African five-lined skink's eye was light-adapted due to a variety of retinal specializations related to the demands of its diurnal lifestyle in its environment.

Ossa cordis and os aorta in the one-humped camel: Computed tomography, light microscopy and morphometric analysis

The present study describes the morphological characteristics of the camel heart Ossa cordis, and os aorta using computed tomography soft tissue window (CT) alongside 3D render volume reconstructions and light microscopy. The current study techniques demonstrated the Ossa cordis and os aorta in the cardiac window with more precision than the black and white (ghost), and angiography images. Transverse and sagittal CT images additionally demonstrated the presence of Ossa cordis and os aorta. This study is the first to record two small Ossa cordis sinistrum and one os aorta in the camel heart, in addition to the more commonly observed singular, large, os cordis dextrum. The os cordis dextrum was always located in the upper part of the interventricular septum, near to its junction with the atrium, forming an elongated rectangular shape when observed transversally. The wider cranial part was composed from bone, whereas the caudal aspect was narrow and contained both bone and cartilage. Light microscopy identified that the os cordis dextrum consisted of trabecular bone, marrow spaces, and hyaline cartilage. Two Ossa cordis sinistrum were detected on the left side of the heart, one in the right fibrous ring and another in the interventricular septum, microscopy showed that both contained only trabecular bone with osteocytes, osteoblasts, and osteoclasts. At the level of ascending aorta, there was also trabecular bone containing osteocytes, an os aorta.

Morphological comparison of the detailed structure of gill rakers from three different feeding habits of marine fish species

The feeding habits and habitat of different fish species influence the morphology and functions of their gill rakers. This study used gross anatomy and scanning electron microscopy to investigate the morphological features of the gill rakers in Siganus luridus, Boops boops, and Pagrus pagrus. The gill rakers appeared as medial and lateral rows in all studied fishes. Except for Pagrus pagrus, which had a unique gill rakers arrangement in which the medial row of the 4th gill arch had the most gill rakers, the longest and most gill rakers were on the 1st gill arch in all studied fishes. The gill rakers of Siganus luridus were smooth, with various spine-like shapes, such as spine-like gill rakers, which were bifid or trifid spines, or duck toe-shaped gill rakers. According to SEM of the Siganus luridus' gill rakers, the trifid end gill rakers resembled caterpillars, and the duck toe-like gill rakers had three or four finger-like spines connected by inter-spine tissue. The Boops boops had long conical gill rakers with pointed ends on the lateral sides of the 1st gill arch, and the remaining rows had short gill rakers. According to SEM of the Boops boops' gill rakers, the long gill rakers were semi-conical and only had needle-like spines on the medial surface. The short gill rakers were projected as a boat and had three different shapes based on spine distributions. Gill rakers include those with a median crest and long spine laterals, those with only lateral spines, those with usually dorsal spines, and those with long wedge-shaped spines. Pagrus pagrus’ gill rakers were short, with fine-needle spines covering their tops. By SEM of the Pagrus pagrus' gill rakers, they appeared as a cylindrical elevation with spines on top. The spines were conical in shape with pointed curved or straight ends. The maximum value of the gill rakers’ lengths was discovered in the lateral row of the 1st gill arch, while the minimum value was in the medial row of the 4th gill arch. As a result, this is the first study of the three fish species' gill rakers. In the studied fishes, the morphological characteristics of gill rakers demonstrated unique structural specifications in feeding behavior.