Ultrastructural Research Articles

Computational analysis of device-to-device variability in resistive switching through single-layer hexagonal boron nitride and graphene vertical heterostructure model

Abstract We quantify the device-to-device variations in resistive switching by considering a single-layer hexagonal boron nitride and graphene junction as a model. Then, we mimic the variations in the surface of a two-dimensional material in terms of defects and interface states by changing the distance between single-layer hexagonal boron nitride and graphene. We use density functional theory as a methodology to perform simulations at the atomic scale. The results show that the distance affects the current–voltage characterization results and that creating ultra uniform structures is important to reduce the device-to-device variability. These results are crucial to understand the reliability and accuracy of device-to-device variations in memory devices and mimic the neural dynamics beyond the synaptic cleft.

The effect of PEG-content and molecular weight of PEG-PPG-PEG block copolymers on the structure and performance of polyphenylsulfone ultra- and nanofiltration membranes

Thin-film composite (TFC) membranes obtained by forming a selective polyamide (PA) layer on a surface of a porous membrane-substrate via interfacial polymerization (IP) technique are the most effective membranes for nanofiltration (NF). The idea of this study is that addition of polyethylene glycol-polypropylene glycol-polyethylene glycol (PEG-PPG-PEG) block copolymers to the polyphenylsulfone (PPSU) casting solution tunes the pore structure (pore size and porosity), water contact angle and topology of the selective layer of ultrafiltration (UF) membranes. This influences the formation of PA layer via IP since membrane-substrate significantly effects the first stage of IP reaction. For the first time the effect of PEG-PPG-PEG copolymer molecular weight, content of PEG blocks and copolymer concentration in the PPSU casting solution on the structure, hydrophilicity and performance of ultrafiltration and TFC NF membranes was revealed. It was found that increase in PEG block content and PEG-PPG-PEG molecular weight led to the increase in pore size, porosity and hydrophilicity of selective layer of ultrafiltration membranes which results in the formation of thinner and more uniform PA layer with higher cross-linking degree of NF membranes via IP. It was revealed that NF membrane flux increased with the rise in the content of PEG units from 10 to 80 wt% and increase in molecular weight of PEG-PPG-PEG block copolymer. Modification of PPSU membrane-substrate yielded the increase in selectivity of the corresponding TFC NF membranes due to the formation of more uniform and denser defect-free PA layer attributed to the rise in hydrophilicity of membrane-substrate. It was found that membrane-substrate modification by PEG-PPG-PEG results in the enhancement of antifouling performance toward bovine serum albumin (flux recovery ratio is 99–100 %) and long-term stability during 48 h operation compared to the reference membrane. Modification of PPSU membrane-substrate by F38 PEG-PPG-PEG block copolymer (Mn = 5000 g mol−1, PEG block content of 80 wt%) was found to yield the TFC NF membranes with the best combination of permeation, separation and antifouling performance and long-term stability.

Structure of root nodules in <i>Laburnum anagyroides</i> Medik.

The structure of the <i>Laburnum anagyroides</i> root nodules was studied by means of classical light and transmission electron microscopy methods. The ability of cross-inoculation and effective nodulation by rhizobial microsymbionts, effective in other genistean species, was not confirmed in <i>L. anagyroides</i>. However, the seedlings were successfully albeit ineffectively nodulated by non-identified rhizobia from soil sampled under established <i>L. anagyroides</i> trees. The microscopic (ultra)structure of these nodules met the basic criteria of genistoid nodules: their meristem was apically positioned and contained two domains (infected and non-infected one), non-bacteroidal rhizobia persisted in apoplast enclaves, and intra-nodule rhizobial infection was passed from cell to cell by host cell division and not by infection threads. The developmental disturbances detected in the nodules (primarily, formation of multi-bacteroid sacs instead of typical single-bacteroid symbiosomes and proliferation apoplast enclaves with accompanying cell wall discontinuities) suggested that the host plant incorrectly recognized the microsymbiont used in the present study.

Characterization of the pancreas of common pheasant (Phasianus colchicus): A light and transmission electron microscope study.

The present work was carried out to investigate the structure and ultra structure of the pancreas in the common pheasant (Phasianus colchicus). Totally, five healthy adult pheasant were used. The pancreas was assessed using histochemistry and transmission electron microscopy (TEM). The pancreas was composed of four lobes: dorsal, ventral, third, and splenic lobes. These lobes emptied into ascending duodenum through three excretory ducts as: ventral duct, splenic duct, and a common duct for dorsal and third lobes. The exocrine pancreas was constituted of pyramidal-shaped acinar cells with aggregation of zymogen granules at their apical cytoplasm. The endocrine pancreas was identified as large islet of Langerhans as α islets and small islets as β ones. No mixed islet was observed. At the level of TEM, two types of acinar cells were distinguished: Dark cells with electron dense cytoplasm, and indented nucleus, Light cells with electron lucent cytoplasm, and regular nucleus. The α islets were mainly constituted by A and D cells, whereas the β islets principally contained B cells and a few A cells. No D cells were identified in β islets. B cells were characterized by their polymorphic granules which were surrounded by a narrow halo zone. The granules of D cells were quite different. These cells contained large spherical granules with lower density as compared to the A or B granules surrounded by a limiting membrane. In conclusion, the pancreas of the common pheasant has a species-specific feature which must be considered in phylogenic studies. RESEARCH HIGHLIGHTS: The common pheasant's pancreas was composed of four lobes as dorsal, ventral, third, and splenic lobe. There were three excretory ducts. Ventral duct for ventral lobe, a common duct for both dorsal and third lobes, and a distinct splenic duct for splenic lobe. The exocrine acini were composed of two distinct types of cells: dark cells and light cells. The large alpha islets were composed of alpha cells and a few numbers of delta cells and small beta islets were composed of beta cells and a few numbers of alpha cells.

Postmortem Ultrastructural Analysis of the Retina from COVID-19 Deceased Patients

ABSTRACT Purpose COVID-19 (coronavirus disease 2019) is an infectious disease caused by SARS-CoV-2, first reported in 2019 in Wuhan, China. Among the common complications is a pro-inflammatory and hypercoagulative response that compromises the vasculature among various organs. Methods In this report, we present the postmortem retinal findings of five patients observed by means of optical microscopy and transmission and scanning electron microscopy techniques. Results Clinical manifestations such as retinal hemorrhages and exacerbated inflammatory infiltrate, altered ultra structure with swollen mitochondria and pyknotic cells in both layers of the retina were observed in all analyzed eyes. Conclusion Our data point to the fragility of this tissue in cases of severe COVID-19.

Quality Characteristics and Ultra Structural Changes of Restructured Buffalo Meat Slices with Flaxseed Flour as Binder: A Novel Value Added Technology

In India, spent buffaloes are the main contributors of meat, which is tough and low priced and poor demand in the market. In this context, a new technological intervention is needed for restructuring of meat to enhance value-added meat production. Accordingly, an investigation was carried out to analyze the efficacy of different levels of flaxseed flour (C, T1, T2, and T3) as a novel binder for making of Restructured Buffalo Meat Slices (RBMS). The results revealed that T3 (RBMS added with 6% flaxseed flour) demonstrated significantly (P<0.01) higher cooking yield, water-holding capacity (WHC), batter stability and lower diameter shrinkage than control and RBMS incorporated with 2 % and 4 % flax seed flour. None of the treatments had significant influence on pH, total protein extractability, collagen content and solubility of RBMS. Moreover, T3 revealed significantly (P<0.01) higher moisture, total protein, total fat and total ash content than RBMS formulated with other levels of flax seed flour. Conversely, significantly lower in hardness, springiness, chewiness and higher in cohesiveness than other treatments. However, T3 influenced the colour scores, though at different degrees. Ultra structural images of cooked samples displayed the protein matrix between myofibrils which indicates gel network of flaxseed gum and proteins, subsequently caused more cohesiveness. This implies that the flaxseed flour acted as excellent novel binder for binding meat pieces. T3 has proven significantly greater sensory scores than other treatments. Thus, it is clearly evident that T3 has improved most of the quality attributes of buffalo meat and can be recommended as a novel value added technology for meat industry. Keywords: Buffalo meat; Flaxseed flour; Quality characteristics; Restructuring; Ultra structure

Development of a new manipulator for the laser blow-off system at Wendelstein 7-X

A new manipulator for the existing laser blow-off system, being applied for impurity transport studies, was designed and is installed at Wendelstein 7-X stellarator. The proper choice of suitable materials in combination with a sophisticated, ultra compact structure that takes into account restrictive boundary conditions was an important development step for the whole design. In particular, the limited space, the resistance to thermal loads and vacuum forces, and the influence on and of the magnetic field had to be taken into account. In addition, the design had to consider that the entire system has to be assembled/disassembled quickly in one piece. With all these challenges in mind, a design for the entire diagnostic system was created, built accordingly, successfully tested and operated in the current campaign.

FINITE ELEMENT ANALYSIS OF TWIST CHANNEL ANGULAR PRESSING

The article deals with the analysis of the unconventional pressing process of metallic materials by twist channel angular pressing (TCAP) method. TCAP process is a modification of the equal channel angular pressing (ECAP) forming method, which can be used to prepare bulk materials with an ultra fine-grained structure. Simulation of the TCAP process is an important source of information on the effect of design and technological parameters on the grain refinement efficiency. The TCAP process was simulated using 3D finite element method (FEM).

Mode of constant magnetic power effects on Escherichia coli viability and antibiotics activities

Background: The region that a magnetic force has an effect on is known as a magnetic field. Normally, two poles of this field are concentrated. Most magnetic objects are made up of a variety of tiny fields known as domains. There are many different techniques that have been published in the literature for using magnetic energy as a diagnostic tool and for treating illnesses in both humans and animals. Aims: To investigate the effects of different levels of static magnetic field on the ultra structure of Escherichia coli a bacterium as well as their antibiotics activities changes. Materials and Method: Locally created dipolar static magnetic field with strength 400, 800, 1200, and 1600 Gauss and used. Between July and October 2022, ten patients with urinary tract infections at Hawler Teaching Hospital and Raparren Hospital for Children in Erbil were isolated for E. coli and then identified by Vitek test. Bacterial culture medium in equal amounts of broth was subjected to the magnetic field for 24 hours. Additionally, treated E. coli culture media (Vitek test) was compared with untreated negative control samples in the bacterial growth subculture, which was checked for bacterial population using spectrophotometer and Vitek diagnosis kit depended on response to different types of antibiotics. Results: An recognized bacterial strain known as E. coli was subjected to magnetic field with two poles pressures of (400, 800, 1200, and 1600) Gausses while it was incubated for 24 hours at a temperature of 37oC. Optical density (O.D.) measurements at 620 nm were used. The results showed that the microorganisms' exposure to the magnetic field produced noticeable alterations on response to different types of antibiotics (Ceftazidime, Azetroname, Ceftazidime, Cefepime, Minocyclin, Azetroname, Ticarcillin/ Clavulanic acid, Azetroname, Piperacillin, Ceftazidime, Cefepime, Ciprofloxacin, Tobramycin, Imipenem, Meropenem, Amikacin, Nitrofurantin, Trimethoprim/ Sulfamethoxazole and Gentamycin) and significantly reduced the number of cells in the exposed bacteria as compared to the control. Conclusions: We came to the conclusion that due to bacterial mutation, the magnetic field could alter bacterial response to different types of antibiotics and bacterial population.

Dermal Telocytes: A Different Viewpoint of Skin Repairing and Regeneration.

Fifteen years after their discovery, telocytes (TCs) are yet perceived as a new stromal cell type. Their presence was initially documented peri-digestively, and gradually throughout the interstitia of many (non-)cavitary mammalian, human, and avian organs, including skin. Each time, TCs proved to be involved in diverse spatial relations with elements of interstitial (ultra)structure (blood vessels, nerves, immune cells, etc.). To date, transmission electron microscopy (TEM) remained the single main microscopic technique able to correctly and certainly attest TCs by their well-acknowledged (ultra)structure. In skin, dermal TCs reiterate almost all (ultra)structural features ascribed to TCs in other locations, with apparent direct implications in skin physiology and/or pathology. TCs' uneven distribution within skin, mainly located in stem cell niches, suggests involvement in either skin homeostasis or dermatological pathologies. On the other hand, different skin diseases involve different patterns of disruption of TCs' structure and ultrastructure. TCs' cellular cooperation with other interstitial elements, their immunological profile, and their changes during remission of diseases suggest their role(s) in tissue regeneration/repair processes. Thus, expanding the knowledge on dermal TCs could offer new insights into the natural skin capacity of self-repairing. Moreover, it would become attractive to consider that augmenting dermal TCs' presence/density could become an attractive therapeutic alternative for treating various skin defects.

Electron microscopy and histopathological examination of canine papilomavirus

Diagnosis of canine papillomavirus (CPV) infection by histopathology, transmission and scanning electron microscopy is presented. The study is based on data obtained by examining nonregressing papillomas (warts) from naturally infected dogs with clinical manifestations of CPV infection. Papules on the mouth and lips were common bilaterally in all dogs. Confirmatory diagnosis of sick dogs was made by clinical findings, histopathology, transmission and scanning electron microscopy. Histopathological examination of hematoxylin and eosin stained papillomas revealed lymphoplasmocytic cell infiltration and fibrosis, parakeratosis in the dermis, papillary proliferation and intranuclear vacuole degeneration in the stratum spinosum. Electron microscopy demonstrated viral icosahedral capsid formation and non-enveloped viral structure of CPV. Transmission electron microscopy demonstrated viral particles and virions in the nuclei of infected cells, viral crystal mode formation in the nucleus. Scanning electron microscopy demonstrated virions and virus-like particles budding in the infected tissue. The findings of the study reveal that electron microscopy and histopathology are effective and sensitive methods in the diagnosis of CPV infection. Electron microscopy is the only imaging technique that allows direct visualization of viruses, along with affected tissues and cells, due to its nanometer-scale resolution. This study reveals the intracellular and extracellular viral pathogenesis, viral ultra structure and structural components of CPV. Present findings indicate canine papillomavirus causes canine papillomatosis, inclusion bodies are common in nonregressive infection, papillomavirus induces cytopathic effect and pathogenesis, viral particles located in the cell and forms crystal mode in nuclear space.

Assessment of TiO2 Nanoparticle Impact on Surface Morphology of Chinese Hamster Ovary Cells.

The process of nanoparticles entering the cells of living organisms is an important step in understanding the influence of nanoparticles on biological processes. The interaction of nanoparticles with the cell membrane is the first step in the penetration of nanoparticles into cells; however, the penetration mechanism is not yet fully understood. This work reported the study of the interaction between TiO2 nanoparticles (TiO2-NPs) and Chinese hamster ovary (CHO) cells using an in vitro model. The characterization of crystalline phases of TiO2 NPs was evaluated by transmission electron microscopy (TEM), X-ray diffraction (XRD) spectrum, and atomic force microscopy (AFM). Interaction of these TiO2 nanoparticles (TiO2- NPs) with the CHO cell membrane was investigated using atomic force microscopy (AFM) and Raman spectroscopy. The XRD analysis result showed that the structure of the TiO2 particles was in the rutile phase with a crystallite size of 60 nm, while the AFM result showed that the particle size distribution had two peaks with 12.1 nm and 60.5 nm. The TEM analysis confirmed the rutile phase of TiO2 powder. Our study showed that exposure of CHO cells to TiO2-NPs caused morphological changes in the cell membranes and influenced the viability of cells. The TiO2-NPs impacted the cell membrane surface; images obtained by AFM revealed an ‘ultra structure‘ with increased roughness and pits on the surface of the membrane. The depth of the pits varied in the range of 40–80 nm. The maximal depth of the pits after the treatment with TiO2-NPs was 100% higher than the control values. It is assumed that these pits were caveolae participating in the endocytosis of TiO2-NPs. The research results suggest that the higher maximal depth of the pits after the exposure of TiO2-NPs was determined by the interaction of these TiO2-NPs with the cell’s plasma membrane. Moreover, some of pits may have been due to plasma membrane damage (hole) caused by the interaction of TiO2-NPs with membrane constituents. The analysis of AFM images demonstrated that the membrane roughness was increased with exposure time of the cells to TiO2-NPs dose. The average roughness after the treatment for 60 min with TiO2-NPs increased from 40 nm to 78 nm. The investigation of the membrane by Raman spectroscopy enabled us to conclude that TiO2-NPs interacted with cell proteins, modified their conformation, and potentially influenced the structural damage of the plasma membrane.

An evaluation of remineralised MIH using CPP-ACP and fluoride varnish: An in-situ and in-vitro study.

Molar incisor hypomineralization (MIH) affected teeth have enamel with altered mineral content like decreased calcium and phosphorus and increased carbon content leading to porous enamel and subsequent post-eruptive breakdown. An in situ study was conducted to evaluate and compare the effects of a Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP)-based cream and fluoride varnish on the remineralization of MIH affected teeth. Enamel slabs were prepared from MIH affected teeth that had been extracted for various reasons and inserted in appliances of 30 participants who were undergoing interceptive orthodontic therapy. They were randomly divided into two groups using block randomization technique: Group A-daily single application of CPP-ACP cream (n = 15); Group B-professional application of fluoride varnishes every 3months (n = 15). After 6months of regular wear of the appliance, the enamel slabs were placed under Field Emission Scanning Microscope (FESEM) and Energy-Dispersive Spectroscopy (EDS) for evaluation of ultra structure and mineral content, respectively. A significant increase in calcium and phosphorus content, and a decrease in carbon content was observed within the 6months period, suggesting remineralization in both the groups. On comparing the Ca:P and Ca:C ratios, a significant increase in the Ca:C ratio was evident in the two groups. No significant difference was seen in the Ca:P ratio in the CPP-ACP group at six months. The inter-group comparison did not reveal any significant difference between the two groups either at baseline or at 6months post-intervention. Remineralization can be achieved in MIH affected teeth with the use of remineralizing agents.

Interactive Effect of Elevated CO2 and Drought Stress on Leaf Anatomy in Brassica Species

The aim of present study was to understand how the ultrastructure of the leaf mesophyll cells in Brassica leaf can be altered under elevated CO2 by interactive effect of elevated CO2 on leaf anatomy and ultra structure of Brassica species under moisture stress conditions. Results of the experiment revealed that the crop genotypes differ greatly in response to elevated CO2 and moisture stress conditions. Elevated CO2 brought about an increase in cell and chloroplast expansion in Brassica genotypes. Elevated CO2 also increased the thickness of epidermis, size ofmesophyll cells, accumulation of starch and size and number of starch granules per chloroplast in Brassica juncea and Brassica juncea cultivars. These alterations in the ultra structure of cells in plants might help to plant adjustment to changing climate in the future.

Ultra structural study on different sensory structure and some associated body parts of mango mealy bug, Drosicha mangiferae (G.) by scanning electron microscopy

Ultra structural study on different sensory structure and some associated body parts of mango mealy bug, Drosicha mangiferae (G.) by scanning electron microscopy

Spore morphology of Selected Pteridophytes Found in the Western Ghats of India

The currents study evaluated the morphology (apperture, size, perine structures and surface ornamentation) of treated spores of 45 selected fern species from the Western Ghats of India, using Scanning Electron Microspcopy (SEM). Twenty-six species of fern spores were trilete type, while 19 of them had monolete aperture types. The size of the spore were found to be highly variable (20X20µm to 60X60µm) with an average mean spore size of 44 µmX38µm. Further more the spores were found to have a highly diverse perine ornementaion with 11 different types of perine structures. Gammate and psilatetype of perine ornamentation,and Globose and ellipsoidal spore shape were found to be the most common within the studies fern spore samples.The variability found in the spore ultra structure and perispore ornamentation of the selected pteridophytes species reflects the morphological differences observed in the sporophyte. The spores could be an important source of characteristics with systematic value in fern taxonomy.The spore morphology of the examined pteridophytes studied common, endemicor otherwise will find a significant role in future taxonomic surveys, and other morphology, Palynology, discrimination, and identification studies of pteridophytesin the Western Ghats.

A new type of electron microscope rapid collection device foratmospheric particles and its application cases.

A device for collecting atmospheric particulates matter for on-line electron microscopy was designed and manufactured by using 3D modeling and printing technology. The device was used to collect atmospheric particulates matter in Xining city of Qinghai province for seven consecutive days and used to collect atmospheric particulates matter in Jinan city of Shandong province for 30 consecutive days. And the samples were analyzed by electron microscopy. Through it can obtain ultra structure and size distribution information of atmospheric particulates matter. The experimental results reflected the distribution of atmospheric particulate matter in real time. The on-line acquisition device for electron microscopy is practical, fast, and convenient, which greatly shortens the sampling period and can be carried to any place outdoors for real-time sampling. The morphological structure and particle size distribution of atmospheric particles in sampling area was observed by electron microscope. The device has reference value to the study of PM2.5 and PM10 in atmosphere and air pollution. This acquisition device is convenient for the detection of sample by electron microscopy. It can further expand and simplify the sampling technology of large-scale instruments and equipment. This new method of real-time monitoring of air pollution is worth popularizing and applying.

Effect of Interleukin-17 gene on glomerular ultrastructure and podocyte injury in adriamycin nephropathy rat models.

The aim of this study was to investigate the mechanism of interleukin-17 (IL-17) gene in renal tissues of rats suffering from adriamycin (ADM) nephropathy and its effect on the expression level of characteristic proteins, such as Podocalyxin and Nephrin, in podocytes. Sprague-Dawley (SD) rats were randomly divided into a control group (treated with normal saline) and an ADM group (treated with adriamycin). ADM model rats were transfected with lentivirus and divided into a transfection group (transfected with recombinant plasmid IL-17-shRNA) and a negative control group (transfected with plasmid shNC). Coomassie brilliant blue G-250 (CBB) method was adopted to detect the levels of albumin in urine to validate the model. The ultrastructure of rat glomeruli was observed, and the ratio of T helper 17 cells/regulatory T cells (Th17/Treg) was measured by flow cytometry (FCM). The expression levels of IL-17, forkhead box P3 (Foxp3), Nephrin, and Podocalyxin were detected by real-time quantitative PCR (RT-qPCR) and western blot analysis. Results of the study showed that the proteinuria content of the ADM group was significantly higher than that of the control group (P<0.05). In the ADM group, the glomerular basement membrane had uneven thickness and incomplete structure, which showed foot process fusion and electron dense accumulation. However, the glomerular basal membrane in the transfected rats was thin and intact, and a small amount of epithelial foot process fusion and electron density accumulation were observed. The percentages of Th17 cells and IL-17 levels in the ADM group were significantly higher than those in the control group, while the percentages of Treg cells, Foxp3, Nephrin, and Podocalyxin levels were significantly lower than those in the control group (P<0.05). The percentages of Th17 cells, IL-17, Nephrin, and Podocalyxin in the transfection group were significantly higher than those in the ADM group and the negative control group, while the percentages of Treg cells and Foxp3 were significantly lower than those in the ADM group and the negative control group (P<0.05). The results of this study showed that abnormal activation of Th17/IL-17 cells caused podocyte injury and promoted the occurrence and progression of ADM nephropathy. In addition, inhibition of IL-17 gene expression could improve the imbalance of number of Th17 and Treg cells, which may be potentially applied in treatment of patients with primary nephrotic syndrome (PNS).

Sinorhizobium medicae 419 vs S. meliloti 1021: differences in root nodules induced by these two strains on the Medicago truncatula host

Symbiosis between plants of family Fabaceae and bacteria genus Rhizobium is the most widespread interaction, in which atmospheric nitrogen is reduced into ammonia. This highly oxygen-sensitive process is performed by endosymbiotc forms of rhizobia called bacteroids, which occupy newly formed plant organs called root nodules. The goal in this paper was to explore the differences in the (ultra)structure and Reactive Oxygen Species (ROS) localization in two symbiotic interactions between legume model plant Medicago truncatula Gaertn. and bacteria from genus Sinorhizobium. Two bacterial strains—Sinorhizobium meliloti 1021 and Sinorhizobium medicae 419 have the ability of inducing root nodules on the Medicago truncatula, however, such nodules differ in effectiveness of biological nitrogen fixation. We demonstrated that root nodules made of S. medicae 419 [fully effective (F++)] induce a lower number of nodule per plant in comparison to S. meliloti 1021—(partially effective F±). Although the differences in the structure are scant, there are some discrepancies in the ultrastructure. In the meristem of F± nodules, there are Cajal bodies and a lower number of vacuole profiles by larger size in comparison to the F++. Nodules F++ have a thicker interzone and store less starch than F+/, while they have higher esterase activity. Localization of different ROS seems to be comparable in the two type of nodules but interestingly, there is not any Nitric Oxide (NO) in the infection thread of F± root nodules.

Studies on Cocoons of Three Epigeic Earthworm Species Perionyx excavatus (Perrier), Perionyx ceylanensis (Michaelsen) and Eudrilus eugeniae (Kinberg) with SEM Observations

Present study deals with cocoon biology of tropical epigeic earthworm Perionyx excavatus (Perrier), Perionyx ceylanensis (Michaelsen) and Eudrilus eugeniae (Kinberg). Ultra structure observed under Scanning Electron Microscope (SEM) revealed that wall of the cocoon is porous (which helps in aeration) and the terminal part of the cocoon is softer than that of middle part which facilitates the hatching process. The size of the cocoon varies among the species and is related to the diameter and length of the clitellum. All the epigeic species under study are continuous breeder with high fecundity. Among the studied species shortest incubation period, highest fecundity and highest hatching rate were observed in P. ceylanensis. Cocoon production in these three epigeic species increases in summer and monsoon season and decreases in the winter season. Temperature is the limiting factor for cocoon production as well as incubation period of cocoon. Cocoon production was affected by temperature and body weight of the earthworm. Thus it can be considered that cocoon production in epigeic earthworm species depends on biological factor (body mass), as well as, ecological factor (temperature). Continuous breeding strategy, high fecundity, high rate of cocoon production, as well as high hatching rate, indicates greater usefulness of P. ceylanensis followed by E. eugeniae than P. excavatus in the vermiculture based biotechnology in North-East India.