The structure of the cutaneous pedal glands in the banded snail Cepaea hortensis (Müller, 1774)

Although gastropods have been crawling through the ocean and on the land for 60 million years, we still know very little about the sticky mucus produced in their foot. Most research has been focused on marine species in particular and, to a lesser extent, on the well‐known terrestrial species Arion vulgaris and Cornu aspersum. Within this study, we aim to characterize the foot anatomy of a smaller representative of the family Helicidae, the banded snail Cepaea hortensis. We are particularly interested in the microanatomy of the foot glands, their position, and the histochemical nature of their secretory content. Characterization of the dorsal foot region of Cepaea hortensis reveals four glands, differing in their size and in the granules produced. Histochemically, three of them react positively for sugars (PAS staining and lectin affinity tests for mannose, glucose and N‐acetyl‐d ‐glucosamine) and acidic proteins (positive Alcian blue and Toluidine blue staining), indicating the presence of acidic glycosaminoglycans. The fourth gland type does not react to any of these dyes. The ventral pedal region includes two different gland types, which are positive for the presence of acidic glycoproteins, with a lectin affinity for mannose only. A comparison with Helix pomatia indicates differences regarding the number of glands and their contents. In Helix, only three gland types are described in the dorsal region of the foot, which show a similar granular appearance but nevertheless differ in their chemical composition. Congruently, there are two gland types in the ventral region in both species, whereas in Helix an additional sugar moiety is found. This raises the question whether these differences between the pedal glandular systems of both helicid species are the result of protection or size‐related adaptations, as they occur in the same habitat.     

PEDAL AND OPERCULAR SECRETORY GLANDS OF POMATIAS, BITHYNIA AND LITTORINA

The histochemical properties of the pedal and opercular glandcells of three prosobranchs from different habitats were examined.The suprapedal gland of Pomatias elegans contained 3 gland celltypes producing mucoprotein, protein and sulphated muco-polysaccharide.The ventral surfaces of the foot were devoid of gland cellsexcept in the median furrow in which two cell types producea neutral and a sulphated mucopolysacharide. The dorsal surfaceof the foot possesses 5 cell types which produce a variety ofmucosubstances. The anterior pedal gland of Bithynia tentaculata produces neutraland weakly acidic mucoprotein from one cell type. The ventralsurface of the foot is generally populated by gland cells oftwo types producing acid mucopolysaccharide and protein. A furthercell type producing carboxylated mucopolysaccharide is restrictedto a transverse band mid-way down the foot. The dorsal surfaceof the foot is covered by mucus from three cell types producinga variety of mucosubstances. The anterior pedal gland of Littorina littorea possesses twocell types both of which secrete mucoprotein. The ventral surfaceof the foot secretes sulphated and carboxylated mucopolysaccharideand a mucoprotein from three cell types which form a thick subepi-dermalglandular layer. The dorsal surface is lubricated by a sulphatedmucopolysaccharide and a mucoprotein. The secretory cells of the dorsal surface extend into the operculargroove and disc whose specialised cells generally secrete mucopolysaccharideand at least two differently staining proteins. ^*Present address: Department of Zoology, University of Durham,Durham City, U.K. (Received 19 August 1986;     

Immunocytochemical Localisation of Glycosaminoglycan-Like Activity in the Mucus and Associated Tissues of Terrestrial Slug Species (Gastropoda: Pulmonata)

Indirect immunofluorescence assays were conducted on cryotome sections of four terrestrial slug species from three distinct phylogenetic groups, Arion ater (L.), Arion hortensis (Férussac), Tandonia (Milax) budapestensis (Hazay), and Deroceras reticulatum (Müller) using monoclonal antibodies for two glycosaminoglycans (GAGs), heparan sulphate, and chondroitin sulphate. Specific staining for a heparan sulphate-like component was demonstrated in the foot and tail regions of each species and was particularly intense in A. ater and A. hortensis, notably in the epidermis and associated mucus-like material, and in mucus-like material from the pedal gland region of the latter species. Subsequent studies with A. ater confirmed the presence of heparan-sulphate–like activity in the caudal gland duct region. No evidence of specific staining for chondroitin sulphate-like activity was found in any of the slug species. This work suggests that a specific GAG, or a group of closely related GAGs, is a common component of mucus in a range of slug species and of different types of mucus, including trail (pedal) mucus and the more viscous mucus produced by the caudal gland.     

Histochemical investigations on the secretory cells in the oesophagogastric tract of the Eurasian green toad,Bufo viridis

The secretory cells of the oesophagogastric tract of the Eurasian toad, Bufo viridis, were examined using standard histochemical methods and lectin histochemistry. Two goblet cell types were found in the oesophageal epithelium, differing in their morphology and the histochemical features of the secretory granules. These contained mainly acidic glycoconjugates, both sulphated and carboxylated, and a small amount of pepsinogen. Type I goblet cells contained stable class-III mucosubstances, which were absent in Type II. No pluricellular oesophageal glands were found. The oesophagogastric junction had a superficial epithelium similar to that of the oesophageal epithelium, with alveolar pluricellular glands, secreting stable class-III mucins, and few oxynticopeptic cells. The gastric mucosa presented secretory cells both in the surface epithelium and in the gastric glands. Superficial and foveolar cells produced neutral mucins with Gal1,3GalNAc residues. Neck cells, oxynticopeptic cells and endocrine cells were found in the gastric glands. Neck cells produced stable class-III mucosubstances. A functional gradient was observed in the oxynticopeptic cells from the oral to the aboral fundus, with a decrease in pepsinogen secretion towards the aboral fundus and a possible increase in HCl secretion. In the pyloric mucosa, the oxynticopeptic cells disappeared and the glands produced only neutral mucins, without stable class-III mucosubstances.     

A comparison between the dermal glands in two insects Rhodnius prolixus (Hemiptera) and Calpodes ethlius (Lepidoptera)

The results of histochemical tests performed on the type “B” dermal gland in Rhodnius and the Verson's gland in Calpodes at different stages in their secretory cycle are presented. The secretions of both glands are slightly acidic sulphated mucosubstances. They differ in their main carbohydrate component which in Rhodnius is hyaluronic acid and in Calpodes is sialic acid. The glands, though structurally similar, differ in size, number, and development.     

Functional aspects of the mucus-producing glands of the Systellommatophoran slug, Veronicella floridana

The mucus-producing glands of the tropical slug Veronicella floridana Leidy were examined histochemically. The bulk of the dorsal mucus is a carboxylated mucopolysaccharide produced by deeply embedded gland cells which contribute to inflated common ducts. Little mucus is apparent on the dorsal surface of an unirritated slug, giving the dorsal aspect of the animal a dry appearance. Measurements of the rate of water loss of whole animals indicate that water is lost significantly more slowly than from the equivalent area of water.
The foot possesses regular transverse ridges and the pedal mucus is produced largely by a set of gland cells associated with each ridge. This mucus is a mixture of mucopolysaccharides and protein. The suprapedal gland which also contributes to the pedal mucus is extremely small and produces a weakly acidic and neutral mucopolysaccharide and a protein. There is no specialization in the leading edge of the foot and no Semper's organ. The cleft between the foot and the body is unciliated and bears few specialized gland cells.
Compared with the mucus produced by Limax pseudoflavus , the pedal mucus of Veronicella is of comparable function and composition though produced by glands of different derivations. The dorsal mucus is histochemically different from that of Limax though similar in physical appearance. Whilst the dorsal mucus of Limax is freely distributed over exposed surfaces, that of Veronicella is held in reserve in inflated ducts resulting in a dry leathery appearance and a depressed rate of water loss.     

Histological features and histochemistry of the mucous glands in ventral skin of the frog (Rana fuscigula)

The glycoconjugate components of secretory granules were analyzed in cells of mucous glands in ventral skin from Rana fuscigula. The analysis was done with standard histochemical methods on semithin glycol methacrylate-embedded tissues. The staining patterns in semithin sections were comparable to those using paraffin-embedded tissue while the cytological detail was better preserved. The mucous glands contained at least two different types of secretory cells lining the lower two-thirds of the mature gland: a principal cell type filled with dense staining secretory granules and a solitary type containing paler staining, globular secretory granules. The principal type of cell contained variable amounts of acid glycoconjugates; predominantly carboxylated but also variably carboxylated and weakly sulfated glycoproteins. Other secretory cells contained mainly neutral glycoproteins. The results indicated that the mucus is a heterogeneous substance and that one cell type may produce different secretory products. We suggested that the variability in histochemical staining might be related to the sequence of biosynthesis of the secretory granule.     

Structural and ultrastructural features of boar bulbourethral glands

The morphological features of boar bulbourethral glands were examined by light and transmission microscopy. Bulbourethral glands are compound tubuloalveolar glands surrounded by a capsule of dense connective tissue and arranged in multiple lobules formed by endpieces and excretory ducts. Endpieces and excretory ducts are both lined by a single epithelium of mucous cells with a basal nucleus. Epithelial cells accumulate secretory granules containing neutral and carboxylated acid mucosubstances and a small amount of sulphated acid mucosubstances. The ultrastructure of epithelial cells varies according to the secretory cycle. In initial stages, the cells show a columnar shape and secretory granules unevenly distributed in the cytoplasm. As the synthesis of mucosubstances progresses, the amount of the secretory granules increases and the cellular shape becomes pyramidal. Secretory granules can contain inclusions and present differences among them according to their different phases of formation. In pyramidal cells, secretory products are released into the lumen by a merocrine mechanism.     

The mucus producing glands and the distribution of the cilia of the pulmonate slug Limax pseudoflavus

The gross anatomy and histochemistry of the mucus-producing glands of Limax pseudoflavus Evans were investigated. The body mucus can be divided into three areas. The dorsal body surface is covered with a sulphated acid mucopolysaccharide/protein mixture secreted largely by five cell types. The pedal mucus is a mixture of neutral mucopolysaccharide from the suprapedal gland. The dorsal and pedal mucus sheets are separated by the peripodal groove whose cells secrete a weakly acid mucus. The duct of the suprapedal gland, the epidermis around the pneumostome, the ventral surface of the peripodal groove and the centre of the underside of the foot are ciliated. The dorsal and pedal mucus remain stationary relative to the body and the substrate respectively and the only rejection currents seen in the mucus are around the pneumostome.
It is suggested that the pedal mucus is formed by the mixture of the products of the suprapedal gland and the mucoprotein secreting gland in the leading edge of the foot, thus producing a mucus suitable for locomotion. Many areas of the animal (e.g. the head, pneumostome, sole and the leading edge of the foot) are capable of producing both a fluid (neutral or weakly acid) and a viscous (acid) mucus. It is postulated that such an arrangement allows for both adhesion and lubrication at different times.     

Morphological phenotypes and functional capabilities of submandibular parenchymal cells of the ferret investigated by protein, mucosubstance and enzyme histochemistry

Submandibular glands obtained post-mortem from mature ferrets of both sexes were examined with the use of light microscopical histochemical methods for proteins, mucosubstances and enzymes associated with cell functions or organelles. Demilunar cells showed carboxylated mucosubstances that were mainly non-sulphated, and diffuse activity for peroxidase, E600-sensitive esterase and acid phosphatase. Thiol groups were also detected in these cells. Central acinar cells showed sulphated mucosubstances, disulphides and reticular staining for thiamine pyrophosphatase. Intercalary ducts showed diffuse activity for NADH and NAD(P)H dehydrogenases. Striated ducts contained protein, tryptophan, disulphides, neutral mucosubstances and E600-sensitive esterase periluminally. Basally, the striated ductal cells showed variable activity for peroxidase, cytochrome oxidase, succinate dehydrogenase and acid phosphatase. Basolateral plasma membranes of these cells exhibited ouabain-sensitive Na,K-ATPase activity. The collecting ducts were characterized by variable periluminal staining for acid phosphatase, -glucuronidase, acid -galactosidase and E600-resistant esterase. The results suggest that the histological appearances of the acini of the submandibular gland of the ferret are dependent on the synthesis of secretory acid glycoproteins, that the striated ducts are involved with the secretion of tryptophan-rich product comprising neutral glycoproteins and showing esterase activity and with marked transport of ions and that the collecting ducts are involved with absorption.     

Anatomy of the major lacrimal gland of rhesus monkeys (Macaca mulatta)

The major lacrimal gland of rhesus monkeys is impalpable within the fatty connective tissue of the upper lateral quadrant of the orbit. Acini of the lacrimal glands are composed of both sparsely and heavily granulated cells that histochemically resemble serous acinar cells of the submandibular salivary gland. The cytoplasmic granules are strongly periodic acid-Schiff (PAS)-positive, and some are also stained by alcian blue for acidic mucosubstances. The lacrimal gland has a simple duct system of intralobular ducts and interlobular excretory ducts. Lymphocytes and plasma cells are common in the periductal stroma. Major lacrimal glands of rhesus monkeys are suitable for comparative and correlative studies of lacrimal and salivary diseases and radiation responses.     

Ultrastructure and cytochemistry of secretory cells in the skin of the leech,Dina lineata

The ultrastructure and histochemical features of the two types of secretory cells in leech skin are described. Pear-shaped cells secrete mucus containing carboxylated mucosubstances, while tubular cells produce a mucus containing a mixture of neutral, carboxylated, and sulfated mucosubstances. Pear-shaped secretory cells have two types of neuroglandular junctions, one containing dense-core serotonergic vesicles and the other small clear vesicles. Tubular secretory cells have large terminals, with many clear vesicles thought to be cholinergic. © 1993 Wiley-Liss, Inc.     

Morphological changes in the male accessory glands and testes in Vespula vulgaris (Hymenoptera,Vespidae) during sexual maturation

Abstract. The present study documents the pace of accessory gland and testes degeneration in the wasp Vespula vulgaris by means of a histological and metric approach, that has not been carried out for social wasps so far. To a certain extent, comparison is made with the degenerative processes of the mucus glands of the honeybee drone. In V. vulgaris, no generative tissue is left by the end of 9 d of age, and so degeneration is a fast process. The three different parts of the accessory glands (muscle layer, gland epithelium, and lumen) change with respect to age. The secretory cells of the epithelium reach their maximum activity during the first days of adult life, which results in a maximally filled gland lumen by 9 d. We also provide, for the first time, a histological study of testes degeneration for this species. At eclosion, well‐defined cystic structures are still visible, whereas at 9 d, it is no longer possible to distinguish different cystic structures. The diameter of the testes decreases with respect to age.     

The ultrastructure and histology of the perinotal epidermis and defensive glands of two species of Onchidella (Gastropoda: Pulmonata)

Histology and electron microscopy were used to describe and compare the structure of the perinotal epidermis and defensive glands of two species of shell-less marine Systellommatophora, Onchidella capensis and Onchidella hildae (Onchidiidae). The notum of both species is composed of a layer of epithelial and goblet cells covered by a multi-layered cuticle. Large perinotal multi-cellular glands, that produce thick white sticky mucus when irritated, are located within the sub-epidermal tissue. The glands are composed of several types of large secretory cell filled with products that stain for acidic, sulphated and neutral mucins, and some irregularly shaped support cells that surround a central lumen. The products of the secretory cells are produced by organelles that are basal in position. The entire gland is surrounded by a well-developed capsule of smooth muscle and collagen, and in addition smooth muscle surrounds the cells within the glands. Based on the size of the gland cells, their staining properties, and the appearance of their stored secretions at the transmission electron microscope level, five different types of secretory cells were identified in O. capensis and four in O. hildae. The products of these cells, which are released by holocrine secretion, presumably mix in the lumen of the duct as they are forced out by contraction of the smooth muscle. The structural similarity of these glands to those of siphonariids, suggest that they have a common ancestry.     

Histochemical reactions of gastrointestinal mucosubstances with orcein,high iron diamine and alcian blue after prior oxidation of tissue sections

Summary The histochemical orcein reaction (orc) for mucosubstances in tissue samples from the human gastrointestinal tract was compared with PAS, high iron diamine (HID) and Alcian blue reactions at pH 1.0 or 2.5 (AB 1 and AB 2.5). Orc, HID and AB 1 reactions were performed also with prior oxidation of the tissue sections with potassium permanganate or performic acid (ox-orc, ox-HID and ox-AB reactions, respectively). Orc reaction stained mucosubstances similarly to HID and AB 1; only the brush border and goblet cells in the colon were stained. The reactions of the mucosubstances obtained with ox-orc differed from those with PAS, HID, AB 1 or AB 2.5 but were similar to those with ox-HID or ox-AB; the mucosubstances in the brush border and the goblet cells in the colon and small bowel and in the foveolar epithelium of the stomach were strongly stained. Pyloric and cardiac glands were stained faintly with ox-orc but not with ox-HID or ox-AB. Brunner's glands were negative with ox-orc, ox-HID and ox-AB reactions. It was assumed that the orc reaction stains, like HID or AB 1, sulphate groups in epithelial mucosubstances, and that sulphonic acid residues, resulting from oxidation of disulphide groups in the protein core of mucus glycoproteins, are responsible for the ox-orc as well as for the ox-HID and ox-AB reactions.The study was supported by grants from the Cancer Society of Finland, Foundation of Orion Corporation and from the Paulo's Foundation, Helsinki, Finland     

Oviducal gland microstructure of Raja miraletus and Dipturus oxyrinchus (Elasmobranchii,Rajidae)

We studied the morphology and histology of the oviducal gland (OG) in the brown ray (Raja miraletus) and the long‐nosed skate (Dipturus oxyrinchus) to understand its functional role in the reproductive strategy of these species. The external morphology of the gland was similar in both species, with lateral extensions like those found in other members of the Rajidae. Microscopic analysis showed a similar internal organization in both species. Immature and developing glands did not react to histochemical techniques. On reaching maturity, the OG had the largest width due to an increase in the production of secretory materials. In both species, the club zone of the gland showed a strong reaction to Periodic acid‐Schiff (PAS) and alcian blue (AB) stains, indicating production of neutral and sulfated acid mucins. The secretory material produced by the papillary zone varied greatly between the two species. Both displayed tubular glands similar to those observed in the club zone, but in D. oxyrinchus the region near the lumen was intensely PAS+, whereas the last row of tubules of the brown ray stained intensely for a mixture of neutral and sulfated mucins. The baffle zone was the most conspicuous and extensive segment of all OGs, and it did not react to PAS/AB. The terminal zone, which is responsible for production of hair filaments, differed between the two species in terms of composition and organization of serous and mucous glands. This difference probably is related to the different substrates in which they release the egg capsules. Individual sperm detected in the brown ray baffle lamellae could be the result of a recent mating, whereas their presence in the deep recesses of the baffle and in the terminal zone of the long‐nosed skate might indicate sperm storage. J. Morphol. 276:1392–1403, 2015. © 2015 Wiley Periodicals, Inc.     

Comparative analysis of the male reproductive accessory glands of bats Noctilio albiventris (Noctilionidae) and Rhynchonycteris naso (Emballonuridae)

In eutherian mammals, the male reproductive accessory glands (RAGs) comprise the prostate, bulbourethral glands, ampullary glands, and the seminal vesicles. Their composition, anatomy and function vary widely between species. This study aimed to characterize histologically and compare the RAGs of bats. The RAGs of Noctilio albiventris (Noctilionidae) and Rhynchonycteris naso (Emballonuridae) were studied using anatomical and histological methods, and were reconstructed three dimensionally. The RAGs of N. albiventris and R. naso are composed of a compact glandular complex that surrounds the urethra and a pair of bulbourethral glands, which are extra‐abdominally located in the inguinal region. In both species, the glandular complex is composed of two well‐defined prostatic regions (ventral and dorsal). The ventral region showed an atypical epithelium (holocrine), where no obvious cellular limits were observed, and PAS‐positive secretion. The dorsal region had a pseudostratified cuboidal epithelium, with basal and secretory cells, and PAS‐negative secretion. Noctilio albiventris also had urethral glands (Littre glands) surrounding the urethra, however, R. naso had only muscles. Both species had bulbourethral glands, with simple columnar epithelium and PAS‐positive secretion. In conclusion, the RAGs of N. albiventris and R. naso comprised a pair of bulbourethral glands and an intra‐abdominal complex, composed of a prostate with two different regions (ventral and dorsal), while the ampullary glands and seminal vesicles were missing in both species. This morphology was more closely related between N. albiventris and R. naso, and to species of the family Phyllostomidae than to families Molossidae and Vespertilionidae. J. Morphol. 277:1459–1468, 2016. © 2016 Wiley Periodicals, Inc.     

Localization of some enzymes in the main venom glands of viperid snakes

Several secretory and nonsecretory enzymes were localized histochemically in the main venom gland of 13 viperid snakes. All secretory cells show the intracellular oxidative enzymes succinate dehydrogenase and monoamine oxidase. The granular reactions obtained for both enzymes resemble mitochondria in distribution. Distinctive cells with a very high succinate dehydrogenase activity are dispersed among the secretory cells of all species except Atractaspis. Nonspecific acid phosphatase activity is found in the supranuclear region of the secretory cells in species that do not secrete this enzyme and throughout the cytoplasm in snakes that secrete the enzyme. Nonspecific alkaline phosphatase activity occurs in the secretory cells of those snakes whose venom shows this activity. Leucine amino peptidase (aryl amidase) activity is found in the venom and in the secretory cells of all the species. In Vipera palaestinae both the venom and the secretory cells of the main venom gland contain nonspecific esterase, L-amino acid oxidase and phosphodiesterase activities. The localization of phosphodiesterase and L-amino acid oxidase do not show major differences between glands at different intervals from an initial milking. Adenosine-monophosphate phosphatase activity is localized in the supranuclear region of the secretory cells in the glands of Vipera palaestinae and Aspis cerastes. Its activity is found in the venom of Aspis only.     

Carbohydrate histochemistry of the opossum submandibular and major sublingual glands.

Submandibular and major sublingual salivary glands of the opossum contain histochemically demonstrable neutral mucosubstances, nonsulfated acid musosubstances and sulfomucins. Sialomucins could not be demonstrated conclusively with the methods used in this study. Special serous cells of the opossum submandibular gland contained low concentrations of acidic mucosubstances but no appreciable concentration of neutral mucosubstances was seen. Sulfomucins were not observed in special serous cells. The mucous tubules of the submandibular gland contained high concentrations of neutral mucosubstances. No appreciable acidic mucosubstance was demonstrated in the submandibular gland mucous tubules. Unlike the mucous tubules of the submandibular gland, the major sublingual gland mucous tubules contained high concentrations of both neutral and acidic mucosubstances. The mucous tubules often contained sulfomucin-positive cells interspersed among cells that contained high concentrations of non-sulfated acidic mucosubstance. Marked staining of sulfated acidic mucosubstance was seen only in the major sublingual gland, in both the mucous tubules and in the seromucous demilunes. The seromucous demilunes contained both sulfated and non-sulfated acidic mucosubstances.     

Histochemistry of mucosubstances in the mantle of fresh water mussel, Parreysia corrugata var. nagpoorensis (Lea) II. Mucosubstances of the middle marginal fold.

The results of the various histochemical reactions on mucosubstances indicate that in the middle fold of the mantle edge two types of mucus cells exist, one producing sulphomucins and the other neutral mucosubstances. The cells secreting neutral mucosubstances are few in number. The sulphated mucus is strongly alcianophilic. The alcianophilia persists when the tissues are stained with alcian blue in concentration up to 0-5 M magnesium chloride. Testicular hyaluronidase has no effect on the staining pattern of the mucus.