Functional morphology of the mantle of Nautilus pompilius (Mollusca, Cephalopoda)

This study presents histological and cytological findings on the structural differentiation of the mantle of Nautilus pompilius in order to characterize the cells that are responsible for shell formation. The lateral and front mantle edges split distally into three folds: an outer, middle, and inner fold. Within the upper part of the mantle the mantle edge is divided into two folds only; the inner fold disappears where the hood is attached to the mantle. At the base of the outer fold of the lateral and front mantle edge an endo-epithelial gland, the mantle edge gland, is localized. The gland cells are distinguished by a distinct rough endoplasmic reticulum and by numerous secretory vesicles. Furthermore, they show a strong accumulation of calcium compounds, indicating that the formation of the shell takes place in this region of the mantle. Numerous synaptic contacts between the gland cells and the axons of the nerve fibers reveal that the secretion in the area of the mantle edge gland is under nervous control. The whole mantle tissue is covered with a columnar epithelium having a microvillar border. The analyses of the outer epithelium show ultrastructural characteristics of a transport active epithelium, indicating that this region of the mantle is involved in the sclerotization of the shell. Ultrastructural findings concerning the epithelium between the outer and middle fold suggest that the periostracum is formed in this area of the mantle, as it is in other conchiferan molluscs.     

Morphological studies on the mantle of the fresh-water mussel Amblema (UNIONIDAE): Scanning electron microscopy

The scanning electron microscope has been used to describe the surface morphology of the mantle in mantle-shell preparations from the fresh-water mussel Amblema. In some regions (adductor muscle insertions), the mantle is firmly attached to the shell. In other areas (along the main course of the mantle), transient adhesions between the outer mantle epithelial cells and the nacre appear to temporally further compartmentalize the extrapallial fluid possibly as a prerequisite for the initial crystallization phenomenon. At the mantle edge, as well as at the isthmus, the periostracum was seen to extrude from the periostracal groove. At the siphonal edge, peculiar fingerlike processes were identified; these may represent primitive photoreceptors. The epithelial cells of the outer mantle epithelium are all microvillated whereas those of the inner mantle epithelium are both microvillated and ciliated. Specific differences in surface morphology are described for various regions of the outer mantle epithelium. These may be related to precise regionalized functional differences of this tissue. Several functions of the mantle, in addition to shell formation, and based on its various morphologies, are also discussed.     

大珠母贝外套膜表皮细胞的超微结构

利用透射电系统地观察大珠母贝的外套有皮细胞，结果表明，细胞可分为５种，即柱状表皮细胞、凸细胞、电子透明大粒细胞、电子稠密粒细胞和电子透明小粒细胞。它们在不同区域的分布、形态和数量变化与外套膜的功能分化密切相关，尤其是与贝壳组分的分泌有关。结缔组织中也分布着许多闰细胞和电子稠密粒细胞，它们可作变形运动进入表皮层。     

Epithelial moulds on the shells of the early Palaeozoic brachiopod Lingulella

A fine hexagonal network of microscopic ridges has been discovered on the internal shell surface of the cosmopolitan Lower Palaeozoic inarticulate genus Lingulella. The micro-ornamentation has been recognised on all well-preserved specimens examined, from Cambrian and Ordovician successions in Ireland, North America, Gt. Britain, Spitzbergen, and China. Examination of the mantle of the related Recent genus Lingula revealed that the outer epithelial cells are arranged in a hexagonal close-packed pattern comparable in size and form to the micro-ornamentation in the fossil shells. This fact, along with the discovery of a polygonal pattern on some organic layers in the Lingula shell, suggests that the micro-ornamentation in fossil Lingulella is the mould of the outer epithelium responsible for shell secretion. No trace of epithelial moulds has yet been found in specimens of Lingula from younger Palaeozoic successions. This difference may prove to be a useful diagnostic feature in distinguishing linguloid inarticulates from one another. Epithelial moulds , Lingulella, Palaeoglossa, Lingula, Cambrian, Ordovician, Recent.     

Changes in marine turbot (Scophthalmus maximus) epidermis and skin mucus composition during development from bilateral larvae to juvenile flat fish

Alike other flat fish, marine turbot has the particularity that changes from larvae with bilateral symmetry to adult with asymmetry, in terms of the position of the eyes. As expected, the skin configuration of this species is also affected by the development and transformation suffered by fish during metamorphosis. In this context, changes in the epidermis of marine turbot were studied using conventional staining and histochemical techniques using six lectins (UEA-I, PNA, RCA-I, WGA, Con A and SBA). During development from larvae to juvenile (3–300 days post-hatching), the epidermis increased in both thickness and the number of cell layers. In fact, the simple cuboidal epithelium observed in larvae at day 3 already became stratified at days 10–12, which sequentially increase in thickness with fish development. Turbot epidermis is composed basically of four cell types: epithelial and mucous or secretory cells that are present through the development, and pigmented cells and a type that the authors described as club-like cells that appear during and post-metamorphosis. The Alcian blue-periodic acid Schiff (AB-PAS) histochemical method revealed the presence of neutral glycoconjugates in mucous and club-like cells at post-metamorphic stages of fish. Accordingly, lectin analysis showed mucous cells containing glycoproteins rich in fucose (UEA-I labelling) and glycoconjugates rich in the sequence galactose-N-acetyl galactosamine (PNA and RCA-I labelling) when this cell type appears. Interestingly, melanophores were observed in the dorsal epidermis of post-metamorphic juveniles. This type of cell contains a black-to-brown pigment that provides the skin the typical colour of this fish species. Changes in mucous coat composition were observed during fish development, which was attributed to different roles of the glycoconjugates.     

Differentiation and Growth of the Brachiopod Mantle

Cell differentiation in the mantle edge of Notosaria, Thecidelhnaand Glottidia, representing respectively, the impunctate andpunctate calcareous articulate and chitinophosphatic inarticulatebrachiopods, is described. Comparison of electron micrographssuggests that outer epithelium which secretes periostracum andmineral shell, is separated from inner epithelium by a bandof "lobate" cells, of variable width, exuding an impersistentmucopolysaccharide film or pellicle. The lobate cells alwaysoccupy the same relative position on the inner surface of theouter mantle lobe; but the outer epithelium is commonly connectedwith the inner surface of the periostracum by papillae and protoplasmicstrands which persist during mineral deposition and ensure thatboth shell and attached mantle remain in situ relative to theoutwardly expanding inner surface of the outer mantle lobe.In the prototypic brachiopod, the lobate cells are likely atfirst to have occupied the hinge of the mantel fold but laterto have been displaced into their present position by the rigidoutward growing edge of the mineral shell.     

Ultrastructural studies on the brachiopod pedicle

Studies of the ultrastructure of representative articulate and inarticulate pedicles show that there are similarities in secretory activity between pedicle epithelia of both classes and the outer mantle epithelium of the inarticulates. Rootlet epithelial cells of the articulate pedicle produce small vesicles which pass to the junction between rootlet and substrate and probably play a part in the breakdown of the substrate. Scanning electron microscopy shows that dissolution of a bivalve shell acting as a substrate often follows the boundary of a single nacre tablet, and transmission electron microscopy shows that the rootlet extends its infiltration along the conchiolin walls. The inarticulate pedicle ending is modified to collect adherent sand grains.     

The fine structure of the planarianPolycelis tenuis ijima

Summary The fine structure of the pharynx is presented and demonstrates that the pharyngeal epithelial system is a continuous one. The epithelial lining of the pharyngeal cavity with its characteristic fibrous secretory bodies merges with the outer pharyngeal epithelium at the point of anchorage of the pharynx. A few of these cells are insunk, the nuclei occurring beneath the underlying muscular layers. The nature of the outer epithelium changes towards the free end of the pharynx; the cells become ciliated and in contents come to resemble the inner epithelium which it joins at the tip.The gut cells merge at a transitional zone with the inner pharyngeal epithelium and at this point both bear microvilli and contain rod-shaped apical bodies. Some of these cells are also insunk. Towards the mouth the epithelium shows a greater degree of insinking and exhibits microapocrine secretion. Both inner and outer epithelia bear sense receptors which are concentrated at the lip.At the point of pharyngeal insertion, the sub-epithelial tissue resembles planarian parenchyma, but is rich in gland cells. These glands open on to the outer epithelium especially towards the free end of the pharynx.This research was supported by the Scientific Research Council. Grant No. B/RG/086.     

TEM immunocytochemistry of a 48 kDa MW organic matrix phosphoprotein produced in the mantle epithelial cells of the Eastern oyster (Crassostrea virginica)

Immunohistochemical TEM of Eastern oyster (Crassostrea virginica) mantle epithelial cells using a polyclonal antibody to a gel purified 48 kDa MW oyster shell phosphoprotein revealed that it is phosphorylated in the Golgi, packaged into secretory vesicles and subsequently exocytosed across the apical membrane of specialized cells. These phosphoprotein producing cells are concentrated along the mantle side facing the shell, in the region of the outer mantle lobe. A layer of calcium enriched immuno-reactive mucous is associated with the apical microvilli of these cells. The 48 kDa phosphoprotein forms a component of the fibrous organic matrix and appears to be involved in calcium supply thus enabling crystal growth at the mineralization front.     

淡水贝类贝壳多层构造形成研究

对几种淡水贝（包括蚌、螺）进行形态及组织学观察，并通过实验方法重现贝壳三种物质，即：角质、棱柱质、珍珠质的生成过程，结果表明：外套膜外表皮细胞是由相同类型细胞组成，这些相同细胞在不同的作用条件下形成贝壳多层构造。     

Endocochliate embryo model in the Mesozoic Ammonitida

An endocochliate embryo model for the Mesozoic Ammonitida is proposed based on scanning electron microscopy of the ammonitella (= embryonic shell) stage of well‐preserved Japanese Cretaceous specimens belonging to nine species of five superfamilies. As in other specimens described previously, the ammonitella wall succeeding from the initial chamber ("protoconch") in the species examined consists of the inner prismatic, middle subprismatic and outer prismatic layers, with minute tubercles resting on the outer. Developmental patterns of these structures and their comparison with primary shell formation in modern Nautilus and Spirula suggest that the outer thin prismatic layer with microtubercles was secreted by the exterior epithelium after the completion of the main ammonitella wall by the interior shell gland. Thus, the early ammonite embryo might have had an endocochliate structural plan as in coleoids, and at the time of hatching the overlying mantle epithelium had shifted anteriorly to become an ectocochliate condition.     

Ultrastructural and cytochemical studies in the mantle of Anodonta cygnea

The large central region of the mantle of Anodonta cygnea was studied using transmission and scanning electron microscopy (TEM and SEM) for ultrastructural analysis and light microscopy (LM) and TEM for cytochemical analysis. X-ray diffraction studies of the organic matrix pellicle deposited on the inner surface of the shell were also carried out. Two groups of columnar cells presenting desmosomes on the apical region were observed in the outer epithelium. One group secretes a structural and neutral mucopolysaccharide (MPS) identified with chitin, normally excreted to form the organic matrix of the shell. Another group presents numerous cytoplasmic vesicles and constitutes the predominant cells of this epithelium. Two different types of mucous cells were found in the inner epithelium. One type secretes a faintly acid mucopolysaccharide (MPS) with sulphate groups and another type secretes an association of this polysaccharide with a neutral MPS. Staining for sulfhydryl groups (probably cysteine) was also positive, suggesting the presence of proteoglycans in these secretions. A third type of cells was also observed presenting a very different ultrastructural aspect (columnar form) without large secretion masses. They may correspond to the replacing cells in this highly secretory epithelium. Elastic fibers were found on the base of the outer epithelium and amoebocytes were observed in the interepithelial tissue.     

Morphology, histochemistry and biochemistry of the oviduct of the toad, Bufo vulgaris (Anura, Amphibia), during the annual reproductive cycle.

On the basis of histological and histochemical characteristics the oviduct of adult Bufo vulgaris can be separated into six zones. These characteristics include mainly the relative abundance of secretory and ciliated epithelial cells, mucosal foldings, tubular glands and the staining properties of the secretory elements. The VI zone (uterine segment) is totally deprived of tubular glands and is prodoundly rich in epithelial secretory cells. These cells and the tubular glands, when well-developed, are rich in neutral and acid mucins in the preovulatory phase, whereas this content is greatly diminished after ovulation. Similarly, the weight and the length of the oviduct displays a marked seasonal pattern. The same is observed for its protein content and acid and alkaline phosphatases. These parameters show the highest values in the preovulatory period and lowest after ovulation. The toad oviduct also displays marked hydroxysteroid dehydrogenase activity along the mucosal epithelium. Its functional significance remains a matter of debate, however. A marked parallelism between the present data and those obtained by others in other amphibians indicates the existence of a common pattern of seasonal modifications correlated mainly with the release of the eggs and the formation of their multi-layered coat.     

Changes in lectin-binding pattern in the digestive tract of Xenopus laevis during metamorphosis. I. Gastric region.

The distribution of structural and secretory glycoconjugates in the gastric region of metamorphosing Xenopus laevis was studied by the avidin-biotin-peroxidase (ABC) histochemical staining method using seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin I, UEA-I; and wheat germ agglutinin, WGA). Throughout the larval period to stage 60, the epithelium consisting of surface cells and gland cells was stained in various patterns with all lectins examined, whereas the thin layer of connective tissue was positive only for RCA-I. At the beginning of metamorphic climax, the connective tissue became stained with Con A, SBA, and WGA, and its staining pattern varied with different lectins. The region just beneath the surface cells was strongly stained only with RCA-I. With the progression of development, both the epithelium and the connective tissue gradually changed their staining patterns. The surface cells, the gland cells, and the connective tissue conspicuously changed their staining patterns, respectively, for Con A and WGA; for Con A, PNA, RCA-I, SBA, and WGA; and for Con A, RCA-I, and WGA. At the completion of metamorphosis (stage 66), mucous neck cells became clearly identifiable in the epithelium, and their cytoplasm was strongly stained with DBA, PNA, RCA-I, and SBA. These results indicate that lectin histochemistry can provide good criteria for distinguishing among three epithelial cell types, namely, surface cells, gland cells, and mucous neck cells, and between adult and larval cells of each type.     

Histochemical and ultrastructural analysis of the epidermal gland cells of Branchiomma luctuosum (Polychaeta, Sabellidae)

Abstract. This histochemical and ultrastructural study describes the epidermal gland cells of a tubicolous polychaete, Branchiomma luctuosum . The histochemistry was carried out using standard techniques and FITC-labelled lectins. Four types of secretory cells were identified in two categories: orthochromatic cells (Type 1) and metachromatic cells (Types 2, 3, and 4). The secretory product of the Type-1 orthochromatic cells contains neutral glycoproteins with Galβ1,3GalNAc residues. Metachromatic cells produce acidic, mainly sulfated, glycoconjugates with Galβ1,3GalNAc residues (Type 2) or glucosidic and/or mannosidic residues (Types 3 and 4). In sialylated chains, terminal sialic acid is bound to the penultimate GalNAc and Galβ1,3GalNAc residues. The complex composition of the mucus produced by epidermal gland cells of B. luctuosum may be correlated with its different functions. Ultrastructural studies of the epidermal gland cells showed differing morphology, and the presence in the gland cells of Types 3 and 4 of a funnel-shaped structure for the extrusion of the secretory material.     

Histochemistry and ultrastructure of amphibian lingual glands and phylogenetic relations

Synopsis The lingual glands of amphibians are confined to the dorsal face of the tongue and are formed by invaginations of the lingual epithelium. The secretory products have a heterogeneous composition. Mucosubstances are usually associated with proteins. The secretory product of the outer glandular cells is rich in mucosubstances of an acidity varying with species. In Anourans and Urodeles, the secretory product of the tubes contains abundant proteins and, where present, mucosubstances are less abundant and less acid than those produced at the surface of the tongue. Proteins and mucosubstances coexist in the same secretory granules, which exhibit a more or less homogeneous appearence in Gymnophiona and in Anourans while having a complex structure in Urodeles.In spite of their primitive anatomical features, the amphibian lingual glands present histochemical signs of a complete cellular evolution.     

Seasonal lectin binding variations of thumb pad in the frog (Pelophylax ridibundus)

The thumb pad is one of the most common secondary sexual characteristics in frogs. Although it is known that amphibian skin has affinity for several lectins, there is no report regarding lectin‐binding affinity of the thumb pad or its structural components. This study investigated localization and seasonal variation of specific carbohydrate moieties of glycoconjugates in both the epidermal and dermal components of the frog thumb pad at the light microscopic level using lectin histochemistry. The study consisted of four seasonal groups of the frog species, Pelophylax ridibundus (Synonym of Rana ridibunda): active, prehibernating, hibernating and posthibernating. Four horseradish peroxidase conjugated lectins were employed. It was found that dolichos biflorus agglutinin (DBA), wheat germ agglutinin (WGA), and ulex europaeus (UEAI) gave positive reactions in both epidermal layers and breeding glands. These three lectins bound specific secretory cells in the breeding glands, and the distribution of the cells and epithelial lectin reactions exhibited seasonal changes. In addition, UEA‐I and peanut agglutinin (PNA) showed an affinity in granular glands and the granular zone of mixed glands. Generally, epidermal lectin binding showed dense affinity during the posthibernation period. DBA, UEA‐I, and WGA‐specific cells in the mucous gland decreased gradually until the posthibernation period. These findings suggest that differences of lectin binding in the thumb pad may be related to functional activities and, thus, seasonal adaptations. Moreover, the presence of specific lectin‐binding cells in the breeding glands indicated that they consisted of heterogeneous secretory cell composition or that the cells were at different secretory stages. J. Morphol. 275:76–86, 2014. © 2013 Wiley Periodicals, Inc.     

Tumor-like lesions in the mantle of the mussel Modiolus difficilis from the Sea of Japan

Two inner growths in the mantle beneath the epithelium were found in 1 of 1000 mussels Modiolus difficilis from Amursky Bay, Sea of Japan, within the city precincts of Vladivostok. Both growths were about 2000 microns in maximal diameter in section and elevated slightly above the mantle surface. The mantle epithelium near the growths formed deep invaginations, and clusters of mucous cells were numerous beneath the epithelium. Histological and histochemical methods were employed. Two different kinds of growth were revealed. The off-white growth consisted of cells with thin granular or vesicular cytoplasm containing glucosaminoglycans, proteins and a small amount of neutral polysaccharides. Growth cells were pure white in color after treatment of preparations with 1% H2SO4 and differed markedly from the mantle cells. The yellow growth consisted of large granular cells with neutral polysaccharides and proteins. Although growths were composed of different kinds of cells, they seemed to be derived from subepithelial mucous cells. This was supported by histological and histochemical staining reactions of some tumor and mantle epithelial cells. Mitotic indices (MI) of growths and subepithelial mucous cells were zero, MI of ciliated mantle epithelium reached 0.07%. The lesions were areas of strongly altered mucous cells of mantle epithelium and were non-neoplastic.