The structure of the egg-shell of Aspiculuris tetraptera Schulz (Nematoda: Oxyuroidea)

Parasitology ◽  
1979 ◽  
Vol 78 (2) ◽  
pp. 145-154 ◽  
Author(s):  
D. A. Wharton
Keyword(s):  
Lipid Layer ◽  
Freeze Etching ◽  
Uterine Secretion ◽  
Egg Shell ◽  
Aspiculuris Tetraptera

The egg of Aspiculuris tetraptera is an ellipsoid measuring 93 × 40 µm. The shell consists of 5 layers: the external uterine layer, internal uterine layer, vitelline layer, chitinous layer and the lipid layer. This nomenclature is based upon the formation and histochemistry of the shell layers. The internal uterine layer contains a system of interconnecting spaces, partly filled by uterine secretion, which open to the exterior of the egg via breaks in the external uterine layer. The surface of the egg is covered by a system of interconnecting grooves. Freeze-etching reveals that the internal uterine layer is open to the exterior via pores, which open into the grooves. Rod-shaped particles are also revealed in the external uterine layer. The operculum of the egg consists of a modification of the uterine and chitinous layers of the shell.

Studies on the function of the oxyurid egg-shell

Parasitology ◽  
1980 ◽  
Vol 81 (1) ◽  
pp. 103-113 ◽  
Author(s):  
D. A. Wharton
Keyword(s):  
Embryonic Development ◽  
Water Loss ◽  
Complex Structure ◽  
Permeability Barrier ◽  
Lipid Layer ◽  
Insect Eggs ◽  
Egg Shells ◽  
Syphacia Obvelata ◽  
Egg Shell ◽  
Aspiculuris Tetraptera

SUMMARYThe egg-shell of Hammerschmidtiella diesingi and Aspiculuris tetraptera reduces the rate of water loss from the egg when exposed to desiccation. Staining of the enclosed larva by acid fuchsin and the collapse of eggs exposed to desiccation indicate that the permeability barrier is heat labile. This suggests that the lipid layer is the main permeability barrie of the shell. The complex structure of the uterine layers has a similar morphology to the respiratory structures of the chorion of some insect eggs. Reflections from the shell, the rate of embryonic development under various conditions and the penetration of lead ions indicate that the shell does not trap a layer of air when immersed in water and the uterine layers cannot, therefore, function as a plastron network. Calculations indicate that if diffusion is limited to the pores in the external uterine layer, the area available for gaseous exchange is reduced by 85·5% in H. diesingi, 95·6% in A. tetraptera and 96·8% in Syphacia obvelata. It is suggested that the uterine layers of oxyurid egg-shells function in a similar fashion to the pores in bird egg-shells and the aeropyles in the chorion of insect egg-shells which do not possess plastron networks. These structures reduce water loss from the egg whilst ensuring an adequate supply of oxygen for embryonic development.

Oogenesis and egg-shell formation in Aspiculuris tetraptera Schulz (Nematoda: Oxyuroidea)

Parasitology ◽  
1979 ◽  
Vol 78 (2) ◽  
pp. 131-143 ◽  
Author(s):  
D. A. Wharton
Keyword(s):  
Vitelline Membrane ◽  
Shell Formation ◽  
Perivitelline Space ◽  
Lipid Layer ◽  
Cytoplasmic Inclusions ◽  
Inner Surface ◽  
Egg Shell ◽  
Aspiculuris Tetraptera ◽  
Lipid Layers

SUMMARYThe ovary of Aspiculuris tetraptera has a prominent terminal cap cell. This is considered to be part of the ovarian epithelium. Oogonia detach from the short rachis and increase in size from 6 to 60 μm; accumulating hyaline granules, shell granules and glycogen. The hyaline granules persist in the egg cytoplasm after shell formation has been completed and are considered to be lipoprotein yolk. The shell granules contribute to the non-chitin fraction of the chitinous layer. A classification of the cytoplasmic inclusions of the nematode oocyte is proposed. Upon fertilization a vitelline membrane is formed which constitutes the vitelline layer of the egg-shell. The chitinous layer is secreted in the perivitelline space, between the vitelline layer and the egg oolemma. Upon completion of chitinous layer synthesis, the egg cytoplasm contracts away from its inner surface. The material of the lipid layer is secreted at the surface of the egg cytoplasm and adheres to the inner surface of the chitinous layer. During secretion of the chitinous and lipid layers by the egg cytoplasm, the uterine cells secrete the unit membrane-like external uterine layer and the crystalline internal uterine layer. A complex system of interconnecting spaces develops in the internal uterine layer. This system is open to the exterior via breaks in the external uterine layer. There is no direct involvement of the uterine cells in the formation of this structure.

The structure and formation of the egg-shell of Hammerschmidtiella diesingi Hammerschmidt (Nematoda: Oxyuroidea)

Parasitology ◽  
1979 ◽  
Vol 79 (1) ◽  
pp. 1-12 ◽  
Author(s):  
D. A. Wharton
Keyword(s):  
Reproductive System ◽  
Mature Oocyte ◽  
Lipid Layer ◽  
Cytoplasmic Inclusions ◽  
Freeze Etching ◽  
Egg Shell ◽  
Discrete Spaces

SUMMARYThe structure and chemistry of the egg-shell of Hammerschmidtiella diesingi was examined. The shell consists of 5 layers: external uterine layer, internal uterine layer, vitelline layer, chitinous layer and lipid layer. The uterine layers contain discrete spaces which open to the exterior via pores. Freeze etching revealed particles of 8·0 nm diameter in the external uterine layer and fibres measuring 2·6–3·1 nm in the chitinous layer. The morphology of the reproductive system, the cytoplasmic inclusions of the mature oocyte and the formation of the layers of the egg-shell are described.

Studies on the structure of the female reproductive system and egg-shell formation inAspiculuris tetrapteraSchulz, (Nematoda: Oxyuroidea)

Parasitology ◽  
1964 ◽  
Vol 54 (4) ◽  
pp. 699-719 ◽  
Author(s):  
A. O. Anya
Keyword(s):  
Reproductive System ◽  
Shell Formation ◽  
Female Reproductive System ◽  
High Concentration ◽  
Classical Study ◽  
Quinone Tanning ◽  
Phenolic Substances ◽  
Egg Shell ◽  
Exogenous Origin ◽  
Aspiculuris Tetraptera

The histological anatomy of the female reproductive system of an oxyuroid nematode,Aspiculuris tetraptera, Schulz, has been described.The process of egg-shell formation in this animal has been followed in detail while the structural and chemical characteristics of the egg-shell have been studied by histochemical and other methods. It is shown that there are three layers: a lipoprotein layer, a ‘chitinous’ layer and the so-called vitelline (glycosidal) membrane. Evidence is presented for the exogenous origin of the lipoprotein layer: this being formed by the cells of the upper uterus which are shown to be secretory.The question of quinone-tanning in the egg-shell ofA. tetrapteraand in other oxyuroids and ascarids is considered. It is shown that neither a polyphenol oxidase nor a high concentration of phenolic substances (apart from protein tyrosine) exists in this system. The significance of these and other observations is discussed in relation to the mechanism of tanning as elucidated in insects and trematodes.I have to acknowledge with gratitude the support of many during these investigations. To Dr P. Tate for his encouragement and provision of facilities at the Molteno Institute; to Dr D. L. Lee, for much useful discussion and permission to refer to some of his unpublished electron micrographs of nematodes; to Professor J. D. Smyth, who kindly read through the manuscript; to the Cambridge Philosophical Society for a grant that made possible the translation of Fauré-Frémiet's classical study onAscaris;and to the Department of Technical Cooperation for financial assistance.

The tylenchid (Nematoda) egg shell: formation of the egg shell in Meloidogyne javanica

Parasitology ◽  
1976 ◽  
Vol 72 (1) ◽  
pp. 29-39 ◽  
Author(s):  
Michael A. McClure ◽  
A. F. Bird
Keyword(s):  
Endoplasmic Reticulum ◽  
Meloidogyne Javanica ◽  
Distal Portion ◽  
Shell Formation ◽  
Lipid Layer ◽  
Dense Cytoplasm ◽  
Cytoplasmic Bridges ◽  
Pass Through ◽  
Egg Shell ◽  
Lipid Layers

SummaryOogonia of Meloidogyne javanica are radially arranged around a central rachis to which they are attached by cytoplasmic bridges. As the oocytes mature the rachis disappears and the oocytes pass through the oviduct in tandem. The oviduct-spermatotheca valve is constructed of two rows of tightly packed cells of which there are four per row. The nuclei of these cells are large and contain balloon-shaped cytoplasmic invaginations. The spermatotheca is characterized by microtubules which extend to its lumen and by invaginations of plasmalemma. Cells of the distal uterine region contain large intracytoplasmic spaces bordered by endoplasmic reticulum whereas proximal uterine cells have dense cytoplasm and large areas of compact endoplasmic reticulum. Egg-shell formation begins in the spermatotheca with the modification of the oolemma to form the vitelline layer. The chitinous layer begins in the distal portion of the uterus and appears to originate from the egg. Proline-containing protein is incorporated into the chitinous and lipid layers as the egg passes through the mid-region of the uterus and formation of the lipid layer in this region completes egg development.

The tylenchid (Nematoda) egg shell: structure, composition and permeability

Parasitology ◽  
1976 ◽  
Vol 72 (1) ◽  
pp. 19-28 ◽  
Author(s):  
Alan F. Bird ◽  
M. A. McClure
Keyword(s):  
Basic Structure ◽  
Vitelline Membrane ◽  
Chemical Components ◽  
Rotylenchulus Reniformis ◽  
Lipid Layer ◽  
Tylenchulus Semipenetrans ◽  
Different Temperatures ◽  
Egg Shells ◽  
Egg Shell ◽  
Lipid Layers

SummaryThe fine structure of egg shells of four different genera belonging to the order Tylenchida has been examined. The species examined were Meloidogyne javanica, Rotylenchulus reniformis, Tylenchulus semipenetrans and Pratylenchus minyus. They are all similar in their basic structure, being composed of vitelline membrane, chitin and lipid layers, but there is considerable variability in the thickness of these layers.We have retained the conventional nomenclature because of its convenience, but it is clear that these layers have a variety of chemical components. However, they do appear to contain the compounds from which they take their name. Thus chitin occurs in the chitin layer, and lipid in the lipid layer. The latter is removed by the technique used in isolating the shell from the egg. Chemical analysis of the hydrolysis products of these shells has revealed a high (35 %) proline content which appears to be a characteristic of those nematode egg shells which have been examined so far. These analyses and treatment with enzymes indicate that the chitin layer is a chitin–protein complex.Experiments on the permeability of eggs of M. javanica at different temperatures indicate that changes in permeability are not due to the melting of a single lipid with a distinct melting point as had been thought in the past. We have found that Arrhenius activation energies calculated from the two slopes of an Arrhenius plot were 17·8 kcal/mol and 43·0 kcal/mol respectively, the transition from one to the other taking place at 62°C. We think that these changes are due to changes in the properties of lipoprotein membranes in the lipid layer. These membranes appear to be of paramount importance in controlling the permeability of the nematode egg shell.

scholarly journals The egg-shell ultrastructure of Blatticola blattae (Graeffe, 1860) (Oxyuridomorpha: Thelastomatidae)

2012 ◽  
Vol 49 (4) ◽  
pp. 253-258
Author(s):  
E. Guzeeva ◽  
S. Spiridonov
Keyword(s):  
Complex System ◽  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Honeycomb Structure ◽  
Lipid Layer ◽  
Transmission Electron ◽  
Egg Shell

AbstractThe egg-shell ultrastructure of Blatticola blattae has been studied under scanning and transmission electron microscopy. Similar to other studied oxyurids, it consists of five layers: a lipid layer, a chitinous layer, a vitelline layer, internal and external uterine layers. Unlike in the closely related thelastomatid Hammerschmidtiella diesingi, the external uterine layer of B. blattae has a honeycomb structure, the complex system of tightly joined prismatic chambers.

Ultrastructural observations on oogenesis and shell formation in Gyrinicola batrachiensis (Walton, 1929) (Nematoda: Oxyurida)

Parasitology ◽  
1983 ◽  
Vol 86 (3) ◽  
pp. 489-499 ◽  
Author(s):  
M. L. Adamson
Keyword(s):  
Dorsal Horn ◽  
Lipid Droplets ◽  
Reproductive Tract ◽  
Ventral Horn ◽  
Multivesicular Bodies ◽  
Shell Formation ◽  
Lipid Layer ◽  
Protein Coat ◽  
Large Numbers ◽  
Egg Shell

SUMMARYIndividual females of Gyrinicola batrachiensis produce 2 types of eggs: thin-shelled auto-infective eggs are produced in the ventral horn of the reproductive tract and thick-shelled eggs (transmission agents) are produced in the dorsal horn. Fine structure of oogenesis and egg-shell formation in the 2 horns of the reproductive tract were studied and compared. Early stages of oogenesis were similar in both horns but mature oocytes differed considerably. Those in the dorsal horn were larger than those in the ventral horn; they contained large numbers of lipid droplets, peripheral patches of glycogen and several types of cytoplasmic granules presumably acting as yolk or playing a role in shell formation. Mature oocytes in the ventral horn contained large amounts of glycogen, relatively few lipid droplets and large multivesicular bodies. Four shell layers formed around ova in the dorsal horn: a vitelline layer, a lipid layer, a chitinous layer and an outer protein coat similar to that described in other oxyurids. Only the vitelline layer formed around thin-shelled eggs. Thick-shelled eggs did not embryonate in utero but thin-shelled eggs nearest the vagina contained larvae. The first moult in eggs of G. batrachiensis was described in a previous communication and it is suggested here that the thin fibrous layer loosely applied to the cuticle of infective larvae in thin-shelled eggs is the moulted 2nd-stage cuticle.

The tylenchid (Nematoda) egg shell: structure, composition and permeability

Parasitology ◽  
1976 ◽  
Vol 72 (1) ◽  
pp. 19-28 ◽  
Author(s):  
Alan F. Bird ◽  
M. A. McClure
Keyword(s):  
Basic Structure ◽  
Vitelline Membrane ◽  
Chemical Components ◽  
Rotylenchulus Reniformis ◽  
Lipid Layer ◽  
Tylenchulus Semipenetrans ◽  
Different Temperatures ◽  
Egg Shells ◽  
Egg Shell ◽  
Lipid Layers

The fine structure of egg shells of four different genera belonging to the order Tylenchida has been examined. The species examined were Meloido-gyne javanica, Rotylenchulus reniformis, Tylenchulus semipenetrans and Pratylenchus minyus. They are all similar in their basic structure, being composed of vitelline membrane, chitin and lipid layers, but there is considerable variability in the thickness of these layers.We have retained the conventional nomenclature because of its convenience, but it is clear that these layers have a variety of chemical components. However, they do appear to contain the compounds from which they take their name. Thus chitin occurs in the chitin layer, and lipid in the lipid layer. The latter is removed by the technique used in isolating the shell from the egg. Chemical analysis of the hydrolysis products of these shells has revealed a high (35 %) proline content which appears to be a characteristic of those nematode egg shells which have been examined so far. These analyses and treatment with enzymes indicate that the chitin layer is a chitin-protein complex.Experiments on the permeability of eggs of M. javanica at different temperatures indicate that changes in permeability are not due to the melting of a single lipid with a distinct melting point as had been thought in the past. We have found that Arrhenius activation energies calculated from the two slopes of an Arrhenius plot were 17·8 kcal/mol and 43·0 kcal/mol respectively, the transition from one to the other taking place at 62°C. We think that these changes are due to changes in the properties of lipoprotein membranes in the lipid layer. These membranes appear to be of paramount importance in controlling the permeability of the nematode egg shell.

scholarly journals Is Change in Electrical Potential or pH a Hatching Signal for Heterodera glycines?

2002 ◽  
Vol 92 (5) ◽  
pp. 456-463 ◽  
Author(s):  
S. M. Pike ◽  
R. Heinz ◽  
T. Walk ◽  
C. Jones ◽  
G. A. Kraus ◽  
...  
Keyword(s):  
Surface Charge ◽  
Heterodera Glycines ◽  
Electrical Potential ◽  
Similar Degree ◽  
Lipid Layer ◽  
Ph Measurements ◽  
Second Stage ◽  
Stage Juvenile ◽  
Egg Shell

This study explored the possibilities that changes in the egg shell/lipid layer electrical potential or pH communicate external hatching conditions to the Heterodera glycines second-stage juvenile (J2) within the mature egg and that electrophysiology could measure effects of chemicals on emergence. Potentials were measured following application of the emergence inducers (ZnSO4 and ZnCl2), ions that do not affect emergence, or synthetic emergence inhibitors. Results were compared with pH measurements and emergence bioassays. Healthy appearing eggs had negative resting potentials. Application of ZnSO4 caused a smooth depolarization. However, eggs containing J2 and immature eggs depolarized to a similar degree when ZnSO4 was added. In addition, ZnSO4, synthetic emergence inhibitors, and CaCl2 caused similar depolarization, and some depolarization was measured in dye-permeable eggs and empty shells. Results suggest that change in cation surface charge contributed to depolarization and that Cl¯ penetrated the egg shell/lipid layer without causing potential changes. In bioassays, zinc consistently stimulated emergence to a greater degree than H2O, other cations, or buffers, and counteracted emergence inhibitors. Zinc-caused emergence stimulation was independent of pH. In summary, it is concluded that depolarization and pH are not emergence signals and electrophysiology is unlikely to measure effectiveness of emergence stimulators or inhibitors.

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