Ultrastructure of an integumental organ with probable sensory function in Paragordius varius (nematomorpha)
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Abstract The cuticle of late parasitic stages of Paragordius varius (Leidy, 1851) is composed of a layer with large fibres and a second layer (often named the areolar layer) distal from it. In this paper, organs are described that start at the basal side of the epidermis, pass the epidermis and the fibrous layer of the cuticle and merge with large, cushion‐like structures in the distal layer of the cuticle. The epidermal part of the organs is composed of darkly stained cells, which are probably in contact with the basi‐epidermal nervous system. Up to four processes of this cell traverse the cuticle. These processes might include cilia, because they contain microtubule‐like structures. The probable connection to nerve cells and the connection to the cushion‐like structures in the outer cuticular layer make it likely that the organs described here are sensory in function.Keywords:
Epidermis (zoology)
Cuticle (hair)
Arthropod cuticle
Integumentary system
Granular layer
The epidermis of Palpigradi is a typical single‐layered squamous epithelium. The epidermal cells of the ventral plate are highly modified as an exchange epithelium. The cuticle of Palpigradi, like that of other arthropods, consists of the procuticle and the epicuticle. The procuticle is very thin in the opisthosoma and but thicker and more sclerotized in the ventral region of the prosoma, where it is two‐layered, i.e. stratified into an endo‐ and an exocuticle. Typical pore canals of different shape and size are found in the cuticle. A thin exocuticle covers the cuticle.
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Integumentary system
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Structure of the cuticle of Tetranychus urticae (Acari, Tetranychidae) is described by means of electron microscopy. The cuticle is composed of an epicuticle and a lamellated procuticle. The epicuticle exhibits an inn er dense layer which shows a weak fibrillar appearence, a cuticulin layer, a wax layer and an outer cement layer. The procuticle can be differentiated in an outer exocuticle which extends to the ridges and lobes, characteristic of the cuticular surface, and an inner lamellated endocuticle. Lamellae are formed of helicoid arranged electron lucent microfibrils embedded in an electron dense matrix. Pores penetrate ali cuticular layers. Structure of the cuticle is compared to published information on the insect cuticle.
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Viral tegument
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Diflubenzuron
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ABSTRACT The cuticle overlying most of the body consists of 2 major layers only, the lamellate endocuticle and the epicuticle, and is very thin (1 to μ). Three major cuticular layers are found in the slightly thicker cuticle of certain areas (2 to 3 μ thick) and in the thickest regions (8 to 10μ)a distinct sclerotized exocuticle is present. The epicuticle consists of 1 to 4 laminae, the ‘inner’, ‘cuticulin’, ‘wax’, and ‘cement’ layers, and the distribution of these laminae is described. The outer surface of the cuticle is thrown into major tubercles of approximately 3 μ pitch, with minor tubercles super-imposed upon them. Modification of the cuticle at the bases of setae is described and related to the mechanical requirements of the setal insertion and suspension. The nature of the muscle insertion is also considered. The epidermis is fully cellular and the cells contain the granules of black pigment which impart the black coloration to the insect. Specializations of the epidermis in the regions of ocelli, setae, muscle insertions, and the vesicles of the ventral tube are described, along with modifications of the overlying cuticle.
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1. The epicuticle on honeybee antennae differentiates in correlation with sclerotization to give qualitatively different reactions on different parts.2. The procuticle of the antennae shows a novel and unorthodox sequence of sclerotization involving two stages. The first stage begins at the outer surface and spreads inwardly, the second begins at the inner surface and spreads outwardly (Figs. 40-46). As a result the entire thickness of cuticle becomes sclerotized but still shows reducing power for osmic acid and ammoniacal silver nitrate. In contrast, the cuticle of thorax and abdomen shows the orthodox sequence of sclerotization proceeding from the outer surface inwardly.3. Argentophile granules disappear during sclerotization from epidermal cells of areas that undergo sclerotization. Large numbers of argentaffin-positive granules remain in the cell cluster under the sense plates.4. In the strip containing sense plates, the antennal cuticle develops a dark brown color in its inner half. This browning, which is additional to the usual sclerotization, is not found in the strip which is devoid of sense plates.5. The cuticle over sense hairs and sense pegs becomes completely sclerotized; the cuticle over sense plates and sunken setae undergoes only the first of the two stages involved in sclerotization.6. It follows that the cuticle over chemoreceptors cannot be assumed to have the same penetration properties as cuticle on other parts of the body. Also, different sensilla with cuticles of similar thickness cannot be assumed to have similar-penetration properties.7. The color of sclerotized antennal cuticle is not noticeably affected by prolonged treatment with hot water (100° C.) but lack of complete resistance to the reatment is shown by a change from near isotropic to readily recognizable birefringence.8. The sense plates are differentiated early in the formation of the adult cuticle. They develop a complicated micelle pattern involving both radial and tangential orientations (Fig. 4). Other sensilla also differentiate early.9. Balken are divisible into smaller fibrils of micellar dimensions. Viewed from the surface they form a crossed-fiber pattern on the antenna with four recognizable orientations: longitudinal, circumferential and two oblique (Fig. 1). At the ends of the segments these Balken fuse into rims which show completely circumferential orientation; the rims in turn join intersegmental membranes which show completely longitudinal orientation.
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1. The cuticular structure of three female pseudococcids, Pseudococcus adonidum L., Epicoccus sp., and E. acaciac (Maskell), has been investigated.2. The cuticle of P. adonidum consists of a two-layered epicuticle, overlying a thin procuticle, almost all of which is endocuticle.3. The cuticle of Epicoccus sp., is highly Specialized. Its epicuticle closely resembles that of P. adonidum. The dorsal cuticle is relatively thick, and is much modified chemically. Most of it consists of mesocuticle in which Millon's reagent delimits three well-defined zones which differ greatly in their reactions to stains and histochemical reagents. The endocuticle is much reduced. A thin layer of procuticle between the hypodermis and the endocuticle is impregnated with lipoid to from a "lipoid zone."4. The cuticle of E. acaciae is thick. It differs from that of Epicoccus sp. principally in that there is no chemical zonation of the procuticle, and the lipoid zone s nielanin-pigmented.5. Wax glands are numerous in the cuticle of P. adonidum. The contents of their reservoirs ("protowax") differ chemically from the surface wax. In Epioccus. many of the glands have atrophied; typical glands are confined to lateral parts of the cuticle in contact with the host plant, and these secrete large quantities of wax which fixes the insect permanently in position.6. The specialized cuticle of Epicoccus appears to have evolved over a long period. during which the insects have been exposed to adverse environmental conditions.
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ABSTRACT The structural features of the cuticle of Streptocephalus are described. The epicuticle and endocuticle, unlike those of other Crustacea, stain alike and show similar chemical characters (apart from the absence of chitin in the epicuticle). This feature appears to be related to the absence of tanning of the cuticle, which remains soft and colourless in all stages of growth. In the epicuticle the outermost very thin layer, whose presence can be inferred from chemical tests, seems to correspond to the outer epicuticle of Crustacea, but this layer lacks histological distinctness. The protein constituent of the cuticle is unlike that of other arthropod cuticles so far studied. It differs markedly from arthropodin or sclerotin and recalls collagen. The significance of the peculiarities of the cuticle is discussed. It is suggested that the structure and chemical characteristics of the cuticle may indicate that it represents a generalized and unspecialized condition of the arthropod cuticle.
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