Morphological Studies Research Articles

Ecomorphology of Longnose Gar (Lepisosteus osseus): on the influence of size, sex, and river location

AbstractEcomorphology is essential to understanding the evolution and biogeography of species. However, morphological studies that focus on nongame or ‘rough’ fish groups such as Gar (Lepisosteidae), outside of a phylogenetic context, are comparatively rare. Herein, we investigate the effects of sex, size, and location in a river to assess the potential for sexual dimorphism, allometry, habitat, or some combination to drive observed morphologic variation. Our dataset includes 230 Longnose Gars (Lepisosteus osseus) made up of both males and females of a wide range of sizes collected from three different sites corresponding to the upper, middle, and lower Great Pee Dee River in South Carolina. Dorsal and lateral photographs were taken from each specimen and landmarked for 2D geometric morphometric analyses. Discriminant function analyses (DFA) were also conducted on a few linear trusses to compare the accuracy of sex-related shape aspects that emerged from morphometrics as a possible field-based tool to help fisheries managers understand their stock populations. Overall, location was a statistically significant predictor of shape, yet the differences were not biologically meaningful. Additionally, sex and size were strong predictors of shape, with the greatest differences seen in the largest individuals. DFA of field measurements found that the Snout Length-to-Total Length ratio accurately predicted sex 71% of the time, with females having longer snouts than males. Differences in ratio between sexes can allow tentative sex assignments without lethal gonadal inspection. This study presents the first standardized whole-body 2D geometric morphometrics protocol for Longnose Gar.

The Modification of Waste Polystyrene and Its Application as a Heavy Oil Flow Improver

The widespread use of polystyrene has brought great convenience to people's lives, but inappropriate recycling practices can also have a significant negative impact on the environment and public health. In this work, waste polystyrene was refined using maleic acid anhydride to produce flow improvers. The effect of the modified polystyrene perception of viscosity reduction and pour point depression of Henan oil was evaluated. The results show that modified polystyrene reduces the viscosity of Henan oil by 96.5% at most and depresses the pour point by 6.1 °C at most. Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1HH NMR) were used to investigate the modified polystyrene. The mechanism of modified polystyrene that improves the fluidity of heavy oil was proposed and analyzed through the study of wax crystal morphology (at 20 °C below the pour point).

MORPHOLOGICAL AND ANATOMICAL RESEARCH OF COMMON MYRTLE LEAVES (MYRTUS COMMUNIS L.)

This paper presents the results of morphological-anatomical study of common myrtle leaves diagnostically significant features (Myrtus communis L.) harvested in the Nikitsky Botanical Garden (Republic of Crimea, Russia). Microscopic analysis of common myrtle leaf petioles was carried out and diagnostic features of dominant biologically active сompounds and tissues luminescence of this plant species leaf petioles were revealed. Morphology and anatomy of common myrtle leaves petioles, luminescence of their tissues were analyzed and summarized and additional diagnostic features of this plant object were revealed. Morphological and anatomical study of common myrtle leaves (Myrtus communis L.) was carried out in accordance with the OFS "Leaves" and "Technique of microscopic and microchemical study of medicinal plant raw materials and medicinal plant preparations" GF RF XIV edition using light microscopy in transmitted and polarized light, as well as luminescence microscopy, which has not been previously studied for this plant. The results of the study concluded that when comparing the luminescence of whole essential oils of myrtle, impure eucalyptus and their components provides a luminescence diagnosis due to the difference in luminescence color; 1,8-cineole is not a diagnostic element in morphological and anatomical luminescence for common myrtle due to the lack of obvious luminescence; euvimal-1 can be used as a diagnostic and luminescence as it has specific luminescence in the form of pink color; the peculiarity of pigmentation of the epithelium of the schizogenic receptacle of the leaf of common myrtle was revealed and the characteristic of its luminescence is species specific for myrtle and can be used as a diagnostic feature in contrast to the impurity raw material of eucalyptus. The results obtained during the study can be further used in the development of the section of the draft pharmacopoeial article “Microscopic features” and other regulatory documentation for a new type of medicinal plant raw material - “Myrtle leaves”, as well as in fundamental botany in the study of species of the family Myrtaceae.

Estimation of genetic polymorphism in quince (Cydonia oblonga Mill.) genotypes using morphological traits and molecular (DNA barcoding) characterizations

Quince (Cydonia oblonga) is a medicinal plant and a member of family Rosaceae. It is native plant of Asia Minor and Europe. It is used in production of jam and jellies and also as a remedy of several ailments. The present study was conducted to evaluate the genetic polymorphism based on morphological and molecular traits. Different varieties of Quince were collected from different ecological zones of Khyber Pakhtunkhwa Pakistan and a total of 26 different morphological traits were recorded among studied genotypes. Based on qualitative morphological trait study, the variety collected from Tindodag was unique one with highest fruit weight (328.82 g). The lowest fruit weight (68.38 g) was recorded for Talash genotype. The Charbagh and Tindodag genotypes showed highest seed length (10.6 mm) while genotypes of Chitral was recorded as lowest (8.4 mm). Statistically, significant level of variation was noted with coefficient of variance ranged from 2.23% to 30.38%. Based on correlation analysis, fruit length had strongly correlation with fruit weight (r = 0.89**), Average Fruit width was found significant with fruit weight (r = 0.90**). Similarly, the Core Width was found strongly significant with Core Length (r = 0.95**). ANOVA analysis indicated 10 quantitative characters to be highly significant, 2 significant and 1 insignificant. Principal component analysis was also computed for the 13 quantitative traits with Eigen value of 0.48 and a total variance of 97.78%. The first principal component shows total variation of 52.52%. In PC2 the total variation was 80.15%, PC3 94.06% while in PC4 it was 97.78%. The NCBI BLAST results shows that all the genotypes have similar origin except Tindodag genotype, which shows differences in its origin. Accession number for all other genotypes is MN216014.1, while accession number of Tindodag genotype is KF861967.1. Based on this study, it can be concluded that Tindodag genotype is unique out of the studied localities. NCBI BLAST have provided further support for the drawn conclusion.

Morphological and structural analysis of monodispersive silica nanoparticles fabricated by stober method for self-cleaning applications

Abstract In this work, silica nanoparticles have been synthesized via the Stober process on a p-type silicon substrate by spin coating method. Structural and morphological studies have been carried out by x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Microstructural analysis by Raman spectroscopy displays a prominent peak at 524 cm−1 which corresponds to crystalline silicon. Further, the elemental study by using energy dispersive x-ray spectroscopy (EDX) confirms the presence of silica with no other impurities. Besides, the wettability property has been studied by contact angle measurement and found to be around 130° for the 6-layer coated thin film which is quasi-super-hydrophobic. The wettability results obtained signify promising properties for the development of self-cleaning devices and applications.

Sustainable Compatibilizers for Silica Reinforcement on Styrene Butadiene Rubber

Silica is a hydrophilic reinforcing filler for rubbers, whilst styrene butadiene rubber (SBR) is a hydrophobic synthetic rubber. The interaction between silica and SBR is relatively weak causing a poor silica dispersion inside the SBR matrix. The amide substances such as stearamide and oleamide have been used as additives to solve the problem of poor degree of silica dispersion. Both additives were laboratory prepared by reacting stearic acid and urea for stearamide; oleic acid and urea for oleamide. Each of those additives was compounded with SBR and other curing chemicals separately and vulcanized using a semi-efficient vulcanization formulation. It was found that both additives have acted as curative additives and plasticisers for the silica-reinforced SBR compound/vulcanisate. They have improved processing properties which have improved the coefficient of vulcanization of the silica-reinforced SBR. Based on the torsion properties; they also have a successful role as plasticisers which have the capabilities to reduce the viscousness and to improve the dispersion of silica reinforcing filler in the compound of SBR. The morphological (scanning electron microscopy) study has confirmed that the compound of SBR-silica with stearamide or oleamide has morphology images with better silica dispersion.

Ontogenetic and evolutionary trends on cephalopod digestive systems

AbstractMeropelagic octopuses hatch as planktonic paralarvae, being the subject of progressive morphological and behavioural changes ending with settlement on the seafloor as juveniles. The comparative morphological study of digestive systems can help to understand the adaptation to particular niches during this challenging plankton-benthos transition. Here, the morphometric development of the digestive system of the common octopus (Octopus vulgaris) is described through 3D microscopy techniques over the first two months of life. This morphological development is compared with those of adults and the holobenthic cuttlefish Sepia officinalis, as well as with the holopelagic squids Loligo vulgaris and Illex coindetii. Based on present and published results, we suggest four stages for the early development of O. vulgaris: (1) post embryonic, (2) early paralarval, (3) advanced paralarval and (4) early juvenile. The digestive system development was variable over time, with faster growth during the first days of planktonic life and after settlement. All the paralarvae-bearing species showed very proportionally enlarged posterior salivary glands at hatching compared both to more developed conspecifics and to the cuttlefish hatchling. This could reflect a potential common feeding mechanism through external digestion and probably a compensatory mechanism for an early digestive gland underperformance. The proportionally smallest digestive system has been found in L. vulgaris, mainly because of their remarkably smaller digestive glands. All species showed major changes in digestive organs between hatchlings and developed phases, indicating how different ecological contexts over ontogeny are reflected in their digestive structures. Graphical abstract

Mathematical model of liver cirrhosis formation during morphological and molecular-genetic preclinical studies

BACKGROUND: Currently, researchers describe challenges in developing new treatments for fibrosis and cirrhosis: poor quality of preclinical models, insufficient trial duration, and lack of markers of therapeutic response. A separate task is to standardize the process of liver cirrhosis formation in preclinical trials, which is necessary to obtain accurate quantitative estimates in a short timeframe. AIM: This study aimed to develop a mathematical model for the formation of liver cirrhosis during preclinical trials. MATERIALS AND METHODS: Liver fibrosis and cirrhosis were induced in male Wistar rats using freshly prepared thioacetamide solution for 17 weeks. The area of connective tissue was determined as a percentage of the image area. The area of interlobular veins was measured in µm2. The numbers of cells expressing the FAP marker and the α-SMA marker were counted. The level of mRNA expression of the Vegfa and Yap1 genes was assessed by real-time polymerase chain reaction. A mathematical model for classifying observations into stages was constructed using multiple logistic regression with stepwise selection of predictors, followed by calculation of sensitivity, specificity, and area under the curve with a 95% confidence interval based on ROC analysis. RESULTS: As a result of the analysis, a mathematical model of liver cirrhosis formation was developed. The model is based on the values of two indicators: FAP+ cells and Yap1 mRNA and demonstrated good quality. The resulting value of the area under the ROC curve of 0.883 suggests good results for classifying cases. CONCLUSIONS: The mathematical model makes it possible to differentiate the stage of liver cirrhosis from the stage of fibrosis during preclinical studies. It provides a foundation for studying the pathogenesis of liver fibrosis and cirrhosis, identifying new potential molecular targets for antifibrotic therapy, and reducing the number of expensive, labor-intensive laboratory tests.

Influence of Cu and Co addition on metallurgical and wear characteristics of AlCrFeNi high entropy alloy

The creation of new alloys with improved qualities has become essential in modern industries for high-performance materials. This work’s main objective is to use vacuum arc melting (VAM) to synthesize two different high-entropy alloys (HEAs): AlCrFeNiCu and AlCrFeNiCo. The mechanical properties, phase composition, grain boundaries, and alloy composition of the HEAs were studied. The predominant crystal structure, the Body-Centred Cubic (BCC) phase was obtained for both alloys. Significantly, the Co-containing HEA showed a smaller particle size than the Cu-containing HEA, which led to a 14.21% increase in microhardness. It indicates that the Co-based HEA will likely perform better than the Cu-based HEA in applications prone to abrasion, and indentation, and requiring high hardness levels based on the observed microstructure and hardness parameters. According to wear surface morphology studies, main effects analysis and ANOVA show that increasing loads and sliding distances increase wear rate, whereas sliding velocity has less effect. The best wear rate-reducing parameters are 10 N, 0.5 m/s, and 500 m for Cu-containing HEAs, and the same can be predicted using regression analysis. The study categorizes the intricate worn surface structure by describing different surface properties and wear mechanisms, such as grooves, delamination, adhesive wear, and pitting.

Solution combustion synthesis for rare earth nano metal oxides using D-glycine as fuel: morphological and optical studies

Solution combustion synthesis for rare earth nano metal oxides using D-glycine as fuel: morphological and optical studies

Molluscan systematics: historical perspectives and the way ahead.

Mollusca, the second-most diverse animal phylum, is estimated to have over 100,000 living species with great genetic and phenotypic diversity, a rich fossil record, and a considerable evolutionary significance. Early work on molluscan systematics was grounded in morphological and anatomical studies. With the transition from oligo gene Sanger sequencing to cutting-edge genomic sequencing technologies, molecular data has been increasingly utilised, providing abundant information for reconstructing the molluscan phylogenetic tree. However, relationships among and within most major lineages of Mollusca have long been contentious, often due to limited genetic markers, insufficient taxon sampling and phylogenetic conflict. Fortunately, remarkable progress in molluscan systematics has been made in recent years, which has shed light on how major molluscan groups have evolved. In this review of molluscan systematics, we first synthesise the current understanding of the molluscan Tree of Life at higher taxonomic levels. We then discuss how micromolluscs, which have adult individuals with a body size smaller than 5 mm, offer unique insights into Mollusca's vast diversity and deep phylogeny. Despite recent advancements, our knowledge of molluscan systematics and phylogeny still needs refinement. Further advancements in molluscan systematics will arise from integrating comprehensive data sets, including genome-scale data, exceptional fossils, and digital morphological data (including internal structures). Enhanced access to these data sets, combined with increased collaboration among morphologists, palaeontologists, evolutionary developmental biologists, and molecular phylogeneticists, will significantly advance this field.

Molecular evolution of toothed whale genes reveals adaptations to echolocating in different environments

BackgroundEcholocation was a key development in toothed whale evolution, enabling their adaptation and diversification across various environments. Previous bioacoustic and morphological studies suggest that environmental pressures have influenced the evolution of echolocation in toothed whales. This hypothesis demands further investigation, especially regarding the molecular mechanisms involved in the adaptive radiation of toothed whales across multiple habitats. Here we show that the coding sequences of four hearing genes involved in echolocation (CDH23, prestin, TMC1, and CLDN14) have different signatures of molecular evolution among riverine, coastal, and oceanic dolphins, suggesting that the evolutionary constraints of these habitats shaped the underlying genetic diversity of the toothed whale sonar.ResultsOur comparative analysis across 37 odontocete species revealed patterns of accelerated evolution within coastal and riverine lineages, supporting the hypothesis that shallow habitats pose specific selective pressures to sonar propagation, which are not found in the deep ocean. All toothed whales with genes evolving under positive selection are shallow coastal species, including three species that have recently diverged from freshwater lineages (Cephalorhynchus commersonii, Sotalia guianensis, and Orcaella heinsohni - CDH23), and three species that operate specialized Narrow Band High Frequency (NBHF) Sonars (Phocoena sinus - prestin, Neophocaena phocaenoides - TMC1 and Cephalorhynchus commersonii - CDH23). For river dolphins and deep-diving toothed whales, we found signatures of positive selection and molecular convergence affecting specific sites on CDH23, TMC1, and prestin. Positively selected sites (PSS) were different in number, identity, and substitution rates (dN/dS) across riverine, coastal, and oceanic toothed whales.ConclusionHere we shed light on potential molecular mechanisms underlying the diversification of toothed whale echolocation. Our results suggest that toothed whale hearing genes changed under different selective pressures in coastal, riverine, and oceanic environments.

Synthesis and characterization of p-CuO/n-ZnO heterostructured composite thin films for the detection of formaldehyde gas.

We report the synthesis and characterization of pure CuO and CuO-ZnO nanostructured composite thin films sprayed on particle-free glass substrates using chemical spray pyrolysis method. The films were systematically analyzed through microstructural, morphological, chemical, and gas-sensing studies. X-ray diffraction (XRD) studies confirmed the polycrystalline nature of the films, with a predominant monoclinic phase along the (002) direction. Key structural parameters, such as crystallite size, dislocation density, strain, and the number of crystallites per unit area, were reported from XRD analysis. Field emission scanning electron microscopy (FESEM) revealed a bundled-like morphology with uniform particle distribution, enhancing the surface area for effective gas interaction. X-ray photoelectron spectroscopy (XPS) results indicated that Cu and Zn ions existed predominantly in the 2+ oxidation state, contributing to the films' reactivity. Significantly, the gas sensing studies were investigated with static liquid distribution method, highlighting the remarkable performance of the 30 wt.% CuO-ZnO composite thin film. This composite exhibited a substantial response to 5 ppm formaldehyde at ambient conditions, showing a recovery time of 22 seconds and a response time of 15 seconds. These findings underscore the potential of CuO-ZnO composites for efficient formaldehyde gas sensing applications, marking a notable advancement in the field of environmental monitoring.

Analysis of the influence of different drying processes on the quality attributes of orange peel

The present research aimed to assess the effect of different drying processes on kinetics, antioxidant content and activity, texture, colour, morphology, and β-carotene content of orange peel (OP). The utilization of microwave drying resulted in a notable increase in the rate of evaporation of water present in the orange peel. This process facilitated the release of bound polyphenols. The OP dried at 600 W exhibited the highest total phenolic compound (24.65 mg GAE/g) and total flavonoid compound (11.73 mg QE/g), as observed in the recorded data. The total antioxidant value exhibited a decrease at both elevated and reduced levels of microwave power compared to raw OP. The study found that the drying model proposed by the Weibull model exhibited the most optimal fit, as evidenced by a low SSerror (1.6 × 10−3-16.12 × 10−3), RMSE (0.02–0.05) and high R2 (0.99–1.00). Among dried products, high hardness (30.92 ± 1.26 N), fracturability (28.31 ± 1.22 N), and lightness (74.01 ± 0.38) were observed in freeze-dried (FD) OP. The browning index was high in microwave drying at 180 W (MWD 180 W), and tray drying (TD) which also produced more vibrant colours, as observed in their high chroma value. The high performance liquid chromatography (HPLC) showed that the retention of β-carotene was observed highest in FD (0.057 ± 0.003 mg/g) and lowest in TD (0.032 ± 0.002 mg/g). The morphological study revealed small-sized particles in high-temperature drying methods (MWD 900 W and TD). Large pores and frequent cracking were observed in microwave drying compared to FD. Four clusters are formed in Principal component analysis (PCA) loading of Fourier transform infrared (FTIR) spectra based on their similar characteristics as found in FTIR. Antioxidant content and texture are closely related to the chemical moieties, as observed in PCA.

Varying the Core Topology in All-Glycidol Hyperbranched Polyglycerols: Synthesis and Physical Characterization.

In the present study, low molecular weight cyclic polyglycidol is used as a macroinitiator for hypergrafting glycidol and producing cyclic graft hyperbranched polyglycerol (cPG-g-hbPG) in the molecular weight range of 103-106gmol-1. Linear graft hyperbranched polyglycerol (linPG-g-hbPG) and hyperbranched polyglycerol (hbPG) are prepared as reference samples. This creates a family of hbPG structures with cyclic, linear, and star cores, allowing to evaluate their properties in solution and in bulk. The morphology study of the high molecular weight structures using atomic force microscopy revealed a spherical shape for cPG-g-hbPG and hbPG, and a cylindrical shape for linPG-g-hbPG in the nanometric range. Small angle X-ray scattering confirmed the compact particle-like structure of this family of hbPG architectures. Interestingly, the glass transition temperature showed a structure dependence, with cPG-g-hbPG having the highest values and hbPG having the lowest values for the same molecular weight. This study is a step forward in the generation of water-soluble polymers with tailored structure and functionality for advanced applications.

The impact of quantum-sized nickel nanoparticles on TiO2 in photovoltaic and photocatalytic systems

The study examines the impact of the incorporation of quantum-sized nickel (Ni) nanoparticles in TiO2 (titanium dioxide) matrix at 1%, 3%, and 5% weight percentages by straightforward, easy, and potentially effective synthesis strategy of direct doping. The structural, morphological, optical, and electrical characterization studies of synthesized films are systematically done and the photovoltaic, photocatalytic applications are evaluated. The integration of nickel into TiO2 influences its photovoltaic properties by enhancing the open-circuit voltage (Voc). However, higher concentrations lead to increased recombination and defects, decreasing efficiency. On conducting photocatalytic studies, TiO2 doped with 1 wt. % nickel exhibits superior photocatalytic efficiency, surpassing that of undoped TiO2. This improvement in photovoltaic and photocatalytic performance is attributed to better charge separation and reduced recombination. However, optimizing nickel levels is crucial for maximizing benefits for the applications using the performed synthesis strategy.

Fish Cell Spheroids, a Promising In Vitro Model to Mimic In Vivo Research: A Review.

In vitro cell culture systems serve as instrumental platforms for probing biological phenomena and elucidating intricate cellular mechanisms. These systems afford researchers the opportunity to scrutinize cellular responses within a regulated environment, thereby circumventing the ethical and logistical challenges associated with in vivo experimentation. Three-dimensional (3D) cell cultures have emerged as a viable alternative to mimic in vivo environments. Within this context, spheroids are recognized as one of the most straightforward and efficacious models, presenting a promising substitute for conventional monolayer cultures. The application of 3D cultures of fish cells remains limited, focusing mainly on physiological and morphological characterization studies. However, given the capacity of spheroids to emulate in vivo conditions, researchers are exploring diverse applications of these 3D cultures. These include eco-toxicology, immunology, drug screening, endocrinology, and metabolism studies, employing a variety of cell types such as fibroblasts, hepatocytes, embryonic cells, gonadal cells, gastrointestinal cells, and pituitary cells. This review provides a succinct overview, concentrating on the most frequently employed methods for generating fish cell spheroids and their applications to date. The aim is to compile and highlight the significant contributions of these methods to the field and their potential for future research.

Hierarchical Structures of Amino Acid Derived Polyhydroxyurethanes: Promising Candidates as Drug Carriers and Cell Adhesive Scaffolds.

In this study, we examined the self-assembly of a series of biodegradable and biocompatible amino acid-based polyhydroxyurethanes (PHUs), investigating the structural influence of these polymers on their self-assembly and the resulting morphological features. The presence of hydrophilic and hydrophobic segments, along with carbonyl urethane, ester, and hydroxyl groups in the PHU backbone, facilitates intermolecular hydrogen bonding, enabling the formation of self-assemblies with hierarchical nanodimensional morphologies. We determined the critical aggregation concentration (CAC) and found that it largely depends on the PHU's structure. In-depth morphological studies demonstrated that the evolution of morphology proceeds in four steps: (1) the initial formation of micelles, which act as seeds at very low concentrations, (2) the elongation of these micelles into nanorod or nanopalette shapes below the CAC range, (3) the epitaxial growth of nanofibers at the CAC, and (4) the complete formation of fibrous mats above the CAC. Additionally, these hierarchical structures were utilized for the encapsulation and release of the drug doxorubicin (DOX). We observed that 75% of the encapsulated DOX was readily released in a mildly acidic environment, similar to the physiological conditions of cancer cells. Cellular uptake studies confirmed the effective uptake of the drug-loaded nanoassemblies into the cytoplasm of cells. Our studies also confirmed that these self-assembled structures can serve as effective cell adhesive scaffolds for tissue engineering applications.

Layout optimization and Performance of Large Array of imaging atmospheric Cherenkov Telescope (LACT)

Abstract Large Array of imaging atmospheric Cherenkov Telescope (LACT) is an array of 32 Cherenkov telescopes with 6-meter diameter mirrors to be constructed at the LHAASO site. In this work, we present a study on the layout optimization and performance analysis of LACT. We investigate two observation modes: large zenith angle observations for ultra-high energy events and small zenith angle observations for lower energy thresholds. For large zenith angles (60°), simulations show that an 8-telescope subarray can achieve an effective area of $3 ~\rm km^2$ and excellent angular resolution. For small zenith angles, we optimize the layout of 4-telescope cells and the full 32-telescope array. The threshold of the full array is about $200~\rm GeV$, which is particularly crucial for studying transient phenomena, including gamma-ray bursts (GRBs) and active galactic nuclei (AGNs). This study provides important guidance for the final LACT layout design and performance estimates under different observational conditions, demonstrating LACT's potential for deep observations of ultra-high energy \gray sources and morphological studies of PeVatrons, as well as time-domain \gray astronomy.

Unusual body division and epithelium structure in unusual phoronid Phoronis embryolabi

Phoronida is a small phylum of benthic marine invertebrates that can occur in large numbers globally. The study of phoronid morphology and anatomy is important for understanding phoronid biology and the function of benthic communities dominated by phoronids. Because all phoronids are tube-living animals, the study of the morphology and ultrastructure of the body wall is an important step toward understanding the processes of the tube formation, growth, and renovation. This study used epoxy histology, scanning and transmission electron microscopy to describe the body regionalization and ultrastructure of the body wall epithelium of the unusual Phoronis embryolabi, which lives as a commensal in burrows of digging shrimps. The trunk of P. embryolabi consists of 8 zones, which are clearly distinguishable in living individuals. These zones are as follows: long head region, median sphincter with its three different parts (waist, upper and lower), muscular region, reproductive region, zone 7, and ampulla. Such body division can correlate with specificity of life style of P. embryolabi. The ultrastructure of the epithelium of all zones differ from each other in thickness, set and abundance of gland cells, structure of the extracellular matrix that underlies the epithelium, and abundance of neurites. The capacity and distribution of glandular cells correlate with tube formation and remodelling. Bacteria of two different types are described along body wall of all parts of the trunk; reciprocally advantageous phoronid-bacteria interaction is suggested. Our data suggest that P. embryolabi is able to build the tube at the anterior end rather than at the posterior end, as previously suggested for other phoronid species. At the same time, the certain mechanism of phoronid tube growth and remodelling is still unknown for phoronids as well as for many other tube-living invertebrates.