Branchial Arches Research Articles

A new cryptic species of Imparfinis (Siluriformes: Heptapteridae) from the Orinoco River basin, revealed by an iterative approach.

An iterative analysis of Imparfinis, combining phylogenetic analysis based on cytochrome oxidase gene and multivariate morphometrics, revealed a new cryptic species from the Andean tributaries of the Orinoco River basin, which is described here. The new species is sister to a clade constituted by Imparfinis hasemani and Imparfinis pijpersi, both from the river basins of the Guiana Shield, being also the most geographically proximate species. Nonetheless, the new species is most similar in general appearance to Imparfinis guttatus from the Madeira and Paraguay River drainages, being almost undistinguishable by conventional characters of external morphology, differing only by morphometric attributes overall. The new species can be distinguished from the remaining congeners by a unique combination of characters, including lower lobe of caudal fin darker than upper lobe, maxillary barbel reaching or surpassing pelvic-fin insertion, 12-15 gill rakers on first gill arch, 40-42 total vertebrae and 9-10 ribs. The new species constitutes the only representative from the Orinoco River basin belonging to Imparfinis sensu stricto.

Phenotypic and molecular basis of SIX1 variants linked to non-syndromic deafness and atypical branchio-otic syndrome in South Korea

Branchio-oto-renal (BOR)/branchio-otic (BO) syndrome is a rare disorder and exhibits clinically heterogenous phenotypes, marked by abnormalities in the ear, branchial arch, and renal system. Sporadic cases of atypical BOR/BO syndrome have been recently reported; however, evidence on genotype–phenotype correlations and molecular mechanisms of those cases is lacking. We herein identified five SIX1 heterozygous variants (c.307dupC:p.Leu103Profs*51, c.373G>A:p.Glu125Lys, c.386_391del:p.Tyr129_Cys130del, c.397_399del:p.Glu133del, and c.501G>C:p.Gln167His), including three novel variants, through whole-exome sequencing in five unrelated Korean families. All eight affected individuals with SIX1 variants displayed non-syndromic hearing loss (DFNA23) or atypical BO syndrome. The prevalence of major and minor criteria for BOR/BO syndrome was significantly reduced among individuals with SIX1 variants, compared to 15 BOR/BO syndrome families with EYA1 variants. All SIX1 variants interacted with the EYA1 wild-type; their complexes were localized in the nucleus except for the p.Leu103Profs*51 variant. All mutants also showed obvious but varying degrees of reduction in DNA binding affinity, leading to a significant decrease in transcriptional activity. This study presents the first report of SIX1 variants in South Korea, expanding the genotypic and phenotypic spectrum of SIX1 variants, characterized by DFNA23 or atypical BO syndrome, and refines the diverse molecular aspects of SIX1 variants according to the EYA1–SIX1–DNA complex theory.

Focuses, Trends, and Developments in Craniofacial Microsomia From 1992 to 2022: A Bibliometric Analysis.

There is a current lack of scientific bibliometric analyses in craniofacial microsomia (CFM) and relevant fields. Craniofacial microsomia is a congenital disease resulting from a series of structural malformations involving the first and second branchial arches. Craniofacial microsomia and related fields have attracted the attention of clinicians and interested researchers worldwide. This study summarizes the research status and focuses to help researchers fully grasp the current research situation of CFM and relevant fields in the past three decades and drive future research into new publications. Literature data were retrieved from the Web of Science Core Collection database. Results Analysis and Citation Report of Web of Science, and CiteSpace software were used to evaluate and visualize the results, including publication characteristics, disciplines, journals, literature, countries/regions, institutions, authors, research focuses, etc. A total of 949 original articles and reviews were included after manual screening, and the overall trend of the number of annual publications and citations was increasing. According to the analysis, the description of the clinical characteristics of CFM, the classification of CFM, and mandibular distraction osteogenesis have always been the focus of research in this field. Besides, with the continuous progress of new technologies such as gene sequencing and the expansion of researchers' understanding of diseases, research on genetics and etiology related to CFM has been a developing trend.

A rare cause of dysphagia due to retropharyngeal foregut duplication cyst: case report and review of the literature

BackgroundThe retropharyngeal space is a deep compartment of the head and neck region which extends from the base of the skull to the mediastinum, between the posterior pharyngeal wall and vertebral muscles, delimited laterally by carotid sheaths. Pathological processes of the retropharyngeal space are rarely encountered, generally are isolated and painless masses often cystic, and they usually originate from branchial arch anomalies, but only in rare cases, they turn out to be foregut duplication cysts. Foregut duplication cyst is rare congenital malformations arising along primitively derived alimentary tract during the first trimester in the developing embryo, mostly seen in the thorax and abdomen, with just few cases reported in the head and neck region. We report an extremely rare case of a foregut duplication cyst lined with respiratory epithelium located in the retropharyngeal space, at the level of the oropharynx, of an adult patient with dysphagia surgically treated, and we also made an analysis of the published literature about this very uncommon condition.Case presentationA 63-year-old male patient with chronic dysphagia was diagnosed with a retropharyngeal cystic lesion, which was surgically treated. Final pathologic evaluation confirmed the diagnosis of a rare foregut duplication cyst lined with respiratory epithelium. A review of the pertaining published literature about the head and neck foregut duplication cysts was made, with a particular emphasis on retropharyngeal ones.ConclusionsRetropharyngeal foregut duplication cysts are a very rare congenital cyst of the head and neck. Clinical symptoms such as dysphagia and dyspnea should be evaluated with fibrolaryngoscopy, and CT and MRI scans are of great significance for definitive diagnosis, which should include the possibility of a foregut duplication cyst in the differential diagnosis. Surgical excision is the elective treatment for this lesion, in order to prevent complications including infection and compression symptoms or eventually malignant transformation.

Aspects of Choosing the Technique of Computed Tomography in the Diagnostics of Maxillofacial Dysostosis

Maxillofacial dysostoses are congenital malformations of organs of head and neck, developing from the I and II gill arches. It is important to carry out differential diagnostics based on a comprehensive basic and additional examination aimed at determining all intracranial and extracranial symptoms specific for concrete syndrome, which is possible with modern methods of radiological diagnostic — CBCT and MSCT. The purpose of the study is to determine key aspects of choosing the computed tomography technique for diagnostics of maxillofacial dysostoses. From 2009 to 2023 215 MSCT and 86 CBCT were performed in 211 patients aged from 2 to 18 years old with maxillofacial dysostoses for the purpose of differential diagnostics of pathology, indications for choosing the volume of radiological examination were determined.

Antiparasitic activity of medicinal plants against protozoan fish parasite Ichthyophthirius multifiliis

The parasitic ciliate Ichthyophthirius multifiliis infests all freshwater fish species and can cause severe economic losses in aquaculture. The present study aims to evaluate the antiparasitic activity of onion (Allium cepa), sage (Salvia officinalis), menthe (Menthe spicata), garlic (Allium sativum), lavender (Lavandula officinalis) and oregano (Origanum onites) essential oils against I. multifiliis trophonts. Gas Chromatography-Mass Spectrometry (GC-MS) analyses determined these essential oils’ chemical components. The major components were dipropyl disulfide (46.15%) in onion, alpha-thujone (46.80%) in sage, carvone (48.00%) in menthe, diallyl disulfide (32.70%) in garlic, 1,8-cineole (32.65%) in lavender; carvacrol (73.00%) in oregano. I. multifilis trophonts were isolated from infected European catfish’s skin and gill arches (Silurus glanis). Then in vitro, antiparasitic assays obtained those essential oils of sage (0.50 mL L-1), lavender (0.25-, and 0.50-mL L-1), and oregano (0.1, 0.25- and 0.50-mL L-1) have been found as 100% effective against trophonts at the different concentration of after 60 min of exposure, respectively (p<0.05). In addition, onion, menthe, and garlic essential oil had effectiveness with 94%, 94%, and 92% mortalities after 60 min of exposure, respectively. These results suggested that sage, lavender, and oregano essential oils can be eco-friendly in controlling I. multifiliis trophonts.

A new cavefish of Sinocyclocheilus (Teleostei: Cypriniformes: Cyprinidae) from the Nanpanjiang River in Guizhou, China.

A new species, Sinocyclocheilus xingyiensis, is described based on specimens collected from a karst cave in Guizhou Province, China. The authors used an integrated taxonomic approach, including morphological and molecular data, to identify the new species as a member of the Sinocyclocheilu angularis group, and it can be distinguished from all other members of this group by a combination of the following features: two pairs of long barbels and long pectoral fins, 42-46 lateral-line scales, 7 (13-14) on outer (inner) side of the first gill arch and 35 (14-15 + 4 + 16 - 17) vertebrae. Phylogenetic analyses based on the cytochrome b (cyt b) gene fragment suggest that S. xingyiensis is a sister lineage to Sinocyclocheilus flexuosdorsalis. The genetic distance (Kimura 2-parameter) between the S. xingyiensis and S. angularis groups of Sinocyclocheilus species based on cyt b gene fragment ranged from 1.2% to 15.4%.

Case report – A rare syndromic association (Goldenhar syndrome)

ABSTRACT Goldenhar syndrome is a diverse and poorly understood continuum of disorders of unknown etiology. It is a complex of developmental disorders (face, ears, eyes, spine, etc.), varying in severity in each patient. The estimated incidence of the syndrome ranges from 1 in 3500 to 5600 live births. The male-to-female ratio is approximately 3:2. Most cases of Goldenhar syndrome occur sporadically, although several case reports have documented occurrences in successive generations that require consideration of autosomal recessive, dominant, or multifactorial inheritance. Since there are other syndromes with similar features, there is still confusion regarding which cases should be classified specifically as Goldenhar syndrome. Goldenhar syndrome is a malformation complex of varying severity, involving the structures arising from the first and second branchial arches, the first pharyngeal pouch, the first branchial cleft and the primordia of the temporal bone. We are presenting a rare case of 2 ½ months old male, with asymmetry of the frontonasal area, left auricle anotia, preauricular tags, epicanthus, and left facial nerve palsy. The child had thoracic hemivertebra and fused right ectopic kidney on left side with grade IV VUR. The child had H type trachea esophageal fistula which was confirmed on CT thorax which was a cause of recurrent chest infections in child.

Study of changes in the histological structure of the gills of carp and zander living in lake Balkhash

The problem of adaptation and reactivity of an organism to various environmental factors is one of the central problems in theoretical and practical biology. At present, the attention of researchers is especially attracted bythe issues of ecological adaptation. Morphological works that shed light on the corresponding structural and functional rearrangements of fish gills in connection with their ecology are still poorly understood. In particular, the issues of comparative morphological assessment of the adaptive responses of gas exchange organs have not been developed. The impact of the enterprises of the metal and mining complex is reflected in the tissues of the organs of fish. Thus, environmental factors, such as the accumulation of heavy metals in water, subject the fish body to a structural and functional rearrangement, thereby changing the normal tissue structure. In this regard, the purpose of the study was to study changes in the histological structures of the gills of carp and zander living in Lake Balkhash. Changes in the tissue structure of the gill arch of fish were in the form of emerging pathologies, the frequency of which was noted using a comparative analysis. For the implementation of this work, a histological, morphometric and statistical study of the tissues of the gills of the studied fish individuals was also carried out. The following pathological processes were observed in the structure of the gills of carp and zander: changes in the shape of secondary lamellae, hyperplasia of the gill epithelium, necrosis and edema of the respiratory epithelium, as well as foci of hemorrhages. The detected changes in the histological structures of fish gills indicate the impact of external environmental factors, one of which, in this article, is the accumulation of heavy metals in water. This study was carried out from a natural ecosystem, thus, literary sources are used to compare the data obtained.

Patterns of senescence and apoptosis during development of branchial arches, epibranchial placodes, and pharyngeal pouches.

Many developmental processes are coregulated by apoptosis and senescence. However, there is a lack of data on the development of branchial arches, epibranchial placodes, and pharyngeal pouches, which harbor epibranchial signaling centers. Using immunohistochemical, histochemical, and 3D reconstruction methods, we show that in mice, senescence and apoptosis together may contribute to the invagination of the branchial clefts and the deepening of the cervical sinus floor, in antagonism to the proliferation acting in the evaginating branchial arches. The concomitant apoptotic elimination of lateral line rudiments occurs in the absence of senescence. In the epibranchial placodes, senescence and apoptosis appear to (1) support invagination or at least indentation by immobilizing the margins of the centrally proliferating pit, (2) coregulate the number and fate of Pax8+ precursors, (3) progressively narrow neuroblast delamination sites, and (4) contribute to placode regression. Putative epibranchial signaling centers in the pharyngeal pouches are likely deactivated by rostral senescence and caudal apoptosis. Our results reveal a plethora of novel patterns of apoptosis and senescence, some overlapping, some complementary, whose functional contributions to the development of the branchial region, including the epibranchial placodes and their signaling centers, can now be tested experimentally.

The spontaneous mouse mutant low set ears (Lse) is caused by tandem duplication of Fgf3 and Fgf4.

The external ear develops from an organized convergence of ventrally migrating neural crest cells into the first and second branchial arches. Defects in external ear position are often symptomatic of complex syndromes such as Apert, Treacher-Collins, and Crouzon Syndrome. The low set ears (Lse) spontaneous mouse mutant is characterized by the dominant inheritance of a ventrally shifted external ear position and an abnormal external auditory meatus (EAM). We identified the causative mutation as a 148Kb tandem duplication on Chromosome 7, which includes the entire coding sequences of Fgf3 and Fgf4. Duplications of FGF3 and FGF4 occur in 11q duplication syndrome in humans and are associated with craniofacial anomalies, among other features. Intercrosses of Lse-affected mice revealed perinatal lethality in homozygotes, and Lse/Lse embryos display additional phenotypes including polydactyly, abnormal eye morphology, and cleft secondary palate. The duplication results in increased Fgf3 and Fgf4 expression in the branchial arches and additional discrete domains in the developing embryo. This ectopic overexpression resulted in functional FGF signaling, demonstrated by increased Spry2 and Etv5 expression in overlapping domains of the developing arches. Finally, a genetic interaction between Fgf3/4 overexpression and Twist1, a regulator of skull suture development, resulted in perinatal lethality, cleft palate, and polydactyly in compound heterozygotes. These data indicate a role for Fgf3 and Fgf4 in external ear and palate development and provide a novel mouse model for further interrogation of the biological consequences of human FGF3/4 duplication.

Identification of Myxobolus distalisensis n. sp. (Cnidaria: Myxozoa) infecting yellow catfish Tachysurus fulvidraco (Richardson), with a supplement description of M. voremkhai (Akhmerov, 1960) Landsberg and Lom, 1991.

With growing scale of intensive fish cultivation, the risk of parasite infection in commercial fish is increased. Precisely identifying and characterizing the parasites that infect the farmed fish is critical to understanding the dynamics of their communities. Here, two species of Myxobolus were identified in farmed yellow catfish Tachysurus fulvidraco (Richardson) in China. Myxobolus distalisensis n. sp. developed plasmodia in the gill filaments, with oval to elliptical myxospores measuring 11.3 ± 0.6 (10.4-12.6) × 8.1 ± 0.3 (7.5-8.6) × 5.5 ± 0.2 (5.2-5.8) μm. Two pyriform polar capsules of equal size were measured 5.3 ± 0.4 (4.5-6.3) × 2.7 ± 0.1 (2.3-3) μm. Myxobolus voremkhai (Akhmerov, 1960) Landsberg and Lom, 1991 developed plasmodia in the gill arch and had a myxospore morphology similar to the conspecific isolates described in previous studies. The consensus sequences of M. distalisensis was remarkably distinct from those deposited in the GenBank, with exception of whereas M. voremkhai showing 99.84% identity. The genetic data on both isolates differed considerably from each other, revealing only 86.96% molecular identity. Histologically, M. distalisensis resided in the filament cartilage, and the aggressive proliferation of the sporogenic stages led to lytic cartilage corrosion. In contrast, plasmodia of M. voremkhai grossly observed at the base of the gill filament were embedded by the connective tissue in the gills arch. Phylogenetically, both isolates were separately placed in different subclades, indicating difference in their evolutionary history. Besides, the taxon under the family Myxobolidae was demonstrated non-monophyletic origins, and parasite radiation largely followed their host affinity.

Effect of Aqueous Extract of Ichthyotoxic Plant Bridelia micrantha (Hochst) (Baill) on Haematology, Histopathology and Carcass Characteristics of African Catfish (Clarias gariepinus) (BURCHELL, 1822) Juvenile

The Bridelia micrantha (Hochst.) (Phyllanthaceae) is an ichthyotoxic plant used in catching fish in Nigeria. The toxicity of aqueous extract of B. micrantha on Clarias gariepinus was investigated under statics bioassay conditions. The concentrations of the leaves extract used were 0.00, 0.10, 0.20, 0.30, 0.40, 0.50 and 0.0.60ml/l. The 24hrs, 36hrs, 48hrs, 72hrs, and 96hrs LC50 were 0.40mg/l, 0.30mg/l, 0.26mg/l, 0.22mg/l and 0.21mg/l respectively, with the range of maximum admissible concentration (MATC) were 0.004 – 0.04, 0.003 – 0.03, 0.0026 – 0.026, 0.0022 – 0.022, and 0.0021 – 0.021 respectively. The opercula ventilation and loss of reflex increased with an increase in the concentrations of the leaves extract at the end of 96-hour exposure period. Respiratory distress, loss of balance, settling at the bottom motionless and erratic swimming was observed before death during the exposure period. There was no significant difference in physicochemical parameters of test media (P<0.05) before, during and after the experimental period. Total Dissolved Solids and Conductivity increased significantly (p<0.05) with increase in extract concentration. Temperature had nonsignificant (p<0.05) reduction at all extract concentrations. Blood analysis revealed significant (P<0.05) reduction in the blood parameters (Haemoglobin, Packed Cell Volume, Red Blood Cells, White Blood Cells, Platelet, Mean Corpuscular Volume and Mean Corpuscular Haemoglobin) of exposed fish. There was severe reduction in Carcass/Proximate (Moisture, Crude Protein, Crude Lipid, Ash, NFE, and Energy) composition of Clarias gariepinus juvenile exposed to B. micrantha. Histopathological examinations of the test fish showed some pathological disruptions, such as skin layer with severe superficial spreading of melanoma, The liver cells revealed hepatic tissue with severe ground glass (GG) appearance of the cytoplasm and intra hepatic hemorrhage (IHH), The gill showed severe effect on the gill architecture with hypertrophy of the gill arch, gill filament and aggregate of inflammation (AI), while the kidney revealed severe degeneration of the renal tissue with severe intra renal necrosis (TN). The result of this study calls for the need to discourage the use of toxic plants for catching fish in Cross River and Nigeria water bodies.

Branchio‐oto‐renal syndrome with submucous cleft palate: A case report

AbstractBackgroundBranchio‐oto‐renal (BOR) syndrome is an autosomal dominant disorder characterized by malformations of the second branchial arch, hearing impairments, and renal anomalies.Case presentationA male infant diagnosed with BOR syndrome presents with an asymmetrical face, forehead protrusion, auricle dysplasia, left external auditory canal closure, hearing impairment, mandibular hypoplasia, submucous cleft palate, facial nerve palsy, renal atrophy, and malalignment of the second toe. Palatoplasty was performed.ConclusionThis case report and related literature review have contributed to existing knowledge regarding BOR syndrome, a rare disorder.

Troglonectes canlinensis sp. nov. (Teleostei: Nemacheilidae), a New Troglomorphic Loach from Guangxi, China.

A new species of the genus Troglonectes is described based on specimens from a karst cave in Andong Town, Xincheng County, Liuzhou City, Guangxi, China. Troglonectes canlinensis sp. nov. can be distinguished from its congener species by the following combination of characteristics: eye degenerated into a black spot; whole body covered by scales, except for the head, throat, and abdomen; incomplete lateral line; forked caudal fin; 8-10 gill rakers on the first gill arch; 13-14 branched caudal fin rays; 8-9 branched dorsal fin rays; 5-6 anal fin rays; 9-10 pectoral fin rays; upper adipose keel depth mostly 1/2 of the caudal peduncle depth; and caudal fin forked.

Pathogenicity of two lineages of infectious hematopoietic necrosis virus (IHNV) to farmed rainbow trout (Oncorhynchus mykiss) in South Korea

In May 2015, a high mortality event in farmed rainbow trout occurred in Jeollabuk-do province in Korea. Histopathological analysis revealed necrosis in the kidney, liver, branchial arch, and gills of moribund fish, and infectious hematopoietic necrosis virus (IHNV) was detected in the lesions by immunohistochemistry. Cytopathic effects were observed in EPC, FHM, and RTG-2 cell lines after inoculation with kidney and spleen tissues and IHNV was detected by reverse transcription polymerase chain reaction (PCR). The amplified PCR product was sequenced, and phylogenetic analysis placed IHNV in the JRt Nagano group. Both in vivo and in vitro trials were performed to compare the virulence properties between RtWanju15 isolate, which causes 100% mortality in imported fry, and a previous isolate RtWanju09 of the JRt Shizuoka group isolated from eggs of healthy broodfish. In vivo challenge with high dose on specific pathogen free (SPF) rainbow trout fry performed in Denmark with isolates RtWanju09, RtWanju15 and DF04/99 isolates showed a survival rates of 60%, 37.5% and 52.5% (average), respectively without statistical difference. The replication efficiency of the two isolates in the in vitro challenge was similar.

Parathyroid cyst-An unusual presentation

Parathyroid cyst is one of the least common causes of neck and mediastinal mass and often mistaken be thyroid cyst. Despite advancement in radiological and cytological investigations diagnosing a parathyroid cyst had always been a clinical challenge and mistaken for thyroid pathology and it is only diagnosed during histopathological examination post-surgical resection. The pathogenesis of parathyroid cyst includes the embryological remnant of the 3 or 4 branchial arch with accumulation of colloid material within it. These are classified into functioning and non -functioning depending on whether they are secreting parathyroid hormone and resulting in hypercalcemia. Surgery is indicated in all functioning Parathyroid cysts to alleviate the symptoms of hypercalcemia, larger Parathyroid cysts, and recommended in Parathyroid cysts that recur following more conservative approaches.

Three-dimensional anatomy of the early Eocene Whitephippus (Teleostei, Lampriformes) documents parallel conquests of the pelagic environment by multiple teleost lineages

ABSTRACT The early Eocene fossil assemblage of the London Clay (Southeastern England) is a key window to the early Paleogene diversification of teleost fishes in the open ocean. Despite their three-dimensional preservation that offers unique insight into skeletal anatomy, the London Clay fossils are still poorly described for the most part. †Whitephippus tamensis is a fossil teleost from this assemblage, known by several well-preserved specimens. Based on a complete description of the known material, including previously hidden structures (braincase, hyoid, and branchial arches) revealed through 3D microtomography, we reinterpret †Whitephippus as an early member of the teleost group Lampriformes. More specifically, the anatomy of †Whitephippus indicates that it is likely a member of the so-called ‘pelagic clade’ including modern opahs and oarfishes. This redescription of †Whitephippus provides the earliest definitive evidence of lampriforms conquering the pelagic environment, alongside numerous other teleost lineages.

Dysfunction of programmed embryo senescence is linked to genetic developmental defects.

Developmental senescence is a form of programmed senescence that contributes to morphogenesis during embryonic development. We showed recently that the SIX1 homeoprotein, an essential regulator of organogenesis, is also a repressor of adult cellular senescence. Alterations in the SIX/EYA pathway are linked to the human branchio-oto-renal (BOR) syndrome, a rare congenital disorder associated with defects in the ears, kidneys and branchial arches. Here, we have used Six1-deficient mice, an animal model of the BOR syndrome, to investigate whether dysfunction of senescence underpins the developmental defects associated with SIX1 deficiency. We have focused on the developing inner ear, an organ with physiological developmental senescence that is severely affected in Six1-deficient mice and BOR patients. We show aberrant levels and distribution of senescence markers in Six1-deficient inner ears concomitant with defective morphogenesis of senescent structures. Transcriptomic analysis and ex vivo assays support a link between aberrant senescence and altered morphogenesis in this model, associated with deregulation of the TGFβ/BMP pathway. Our results show that misregulation of embryo senescence may lead to genetic developmental disorders, significantly expanding the connection between senescence and disease.

Hydrodynamic analysis of bioinspired vortical cross-step filtration by computational modelling.

Research on the suspension-feeding apparatus of fishes has led recently to the identification of novel filtration mechanisms involving vortices. Structures inside fish mouths form a series of 'backward-facing steps' by protruding medially into the mouth cavity. In paddlefish and basking shark mouths, porous gill rakers lie inside 'slots' between the protruding branchial arches. Vortical flows inside the slots of physical models have been shown to be important for the filtration process, but the complex flow patterns have not been visualised fully. Here we resolve the three-dimensional hydrodynamics by computational fluid dynamics simulation of a simplified mouth cavity including realistic flow dynamics at the porous layer. We developed and validated a modelling protocol in ANSYS Fluent software that combines a porous media model and permeability direction vector mapping. We found that vortex shape and confinement to the medial side of the gill rakers result from flow resistance by the porous gill raker surfaces. Anteriorly directed vortical flow shears the porous layer in the centre of slots. Flow patterns also indicate that slot entrances should remain unblocked, except for the posterior-most slot. This new modelling approach will enable future design exploration of fish-inspired filters.