Multicellular Glands Research Articles

Evo Devo of the Vertebrates Integument

All living jawed vertebrates possess teeth or did so ancestrally. Integumental surface also includes the cornea. Conversely, no other anatomical feature differentiates the clades so readily as skin appendages do, multicellular glands in amphibians, hair follicle/gland complexes in mammals, feathers in birds, and the different types of scales. Tooth-like scales are characteristic of chondrichthyans, while mineralized dermal scales are characteristic of bony fishes. Corneous epidermal scales might have appeared twice, in squamates, and on feet in avian lineages, but posteriorly to feathers. In contrast to the other skin appendages, the origin of multicellular glands of amphibians has never been addressed. In the seventies, pioneering dermal–epidermal recombination between chick, mouse and lizard embryos showed that: (1) the clade type of the appendage is determined by the epidermis; (2) their morphogenesis requires two groups of dermal messages, first for primordia formation, second for appendage final architecture; (3) the early messages were conserved during amniotes evolution. Molecular biology studies that have identified the involved pathways, extending those data to teeth and dermal scales, suggest that the different vertebrate skin appendages evolved in parallel from a shared placode/dermal cells unit, present in a common toothed ancestor, c.a. 420 mya.

Morphological and anatomical study of <i>Crataegus submollis</i> Sarg. shoots

Aim to conduct a morphological and anatomical study of dried shoots of soft hawthorn collected during the flowering period.
 Material and methods. The shoots of soft hawthorn were collected during the flowering period in the Botanical Garden of Samara University. The micro-preparations were immersed in an alcohol-water-glycerin mixture (1:1:1). To determine the lignified elements of stems and pedicels, a solution of 2% aniline sulfate in 50% ethanol was used. The samples of raw material were examined in daylight using a magnifying glass and a "Motic DM-39C-N9GO-A" binocular. The microscopic examination was performed in transmitted and reflected light using a digital microscope Carl Zeiss Primo Star 415500-0057-000 (Imaging Software for Microscopy ZEN soge V2.7).
 Results. The study of anatomical and morphological properties of hawthorn shoots revealed their most characteristic feature - the abundant pubescence with simple hairs. In addition, the edge of the leaf blades, bracts and sepals had multicellular glands with brown contents.
 Conclusion. The anatomy of the petiole of the hawthorn leaf was described for the first time. The study allows us to identify characteristic changes in the conducting system of the leaf. The morphological and anatomical analysis allows us to identify the common features of the semi-soft hawthorn and closely related species.

Redescription of Aspidogaster limacoides Diesing, 1834 (Aspidogastrea: Aspidogastridae) from freshwater fishes of northern Germany

Aspidogaster limacoides Diesing, 1834 (Aspidogastridae) is redescribed based on light and scanning electron microscopy of specimens from the stomach and intestine of Abramis brama, Rutilus rutilus and Scardinius erythrophthalmus (Actinopterygii: Cyprinidae). The fishes were sampled during 2018 and 2019 at Lake Tollense in Mecklenburg-Western Pomerania, Germany. The prevalence of A. limacoides was highest in R. rutilus (61.7%) followed by Scardinius erythrophthalmus (7.7%) and A. brama (2.9%), while it was absent in Perca fluviatilis from the same lake. The following structures of A. limacoides are described for the first time: a depression on the ventral side of the neck, variations in the number and the arrangement of alveoli, numerous pits scattered all over the body surface, the presence of a few papillae-like structures posterior lateral to the mouth, the number of marginal organs represented by openings of exocrine multicellular glands as shown in histology and the subterminal position of the excretory pore. These characters can be used to distinguish three species of Aspidogaster, namely, A. ijimai, A. conchicola and A. limacoides, suggesting that SEM is a useful and promising tool in differentiating Aspidogaster species. Comparison of molecular data of the ITS1-5.8S-ITS2 regions showed a 94% similarity to A. limacoides from the European part of Russia. Phylogenetic analysis showed that the present specimens clustered in the same clade with A. limacoides sensu stricto, forming a distinct group to the exclusion of congeners.

Salivary Glands of Vertebrates: Ecological, Morphological and Evolutionary Aspects

The aim of the study was to compare ecological and morphological features and evolutionary dynamics of the salivary glands in representatives of different classes of vertebrates living in different ecological conditions.Material and methods. The glandular structures of the tongue of vertebrates belonging to various taxonomic and ecological groups (fish, amphibians, reptiles, mammals) were studied. The material obtained was processed using histological and histochemical methods.The results of the study demonstrated that in the course of the evolutionary transformations of vertebrates, an increase and complication of the glandular structures of the tongue occurred due to changes in the environmental factors and in the nature of nutrition and food consumed. The evolutionary transformations of the glandular structures of the organ was directed from unicellular intraepithelial glandular structures (for example, in fish) to the complex multicellular salivary glands of higher mammals, in which there was a division into terminal secretory sections and secretory pathways. In the course of evolution, the number of functions performed by the salivary glands of the tongue has also increased. The digestive and endocrine functions were added to the function of protecting the mucous organ from damage. The serous glands of the tongue are phylogenetically younger. Their occurrence is associated with the participation of the glands of the tongue in the initial stages of chemical food processing. The preservation of more ancient mucous glands against the background of the emergence of new organisms in the course of evolution - mucoserous, seromucous and serous glands, - indicates that in the course of evolutionary development, the glandular structures of the tongue demonstrate parallelism of divergent changes.

Stigma, pollen tube transmitting tract, and epidermal micromorphology of the style of Sarracenia purpurea (Sarraceniaceae)

Entomophilous flowers of the genus Sarracenia have a unique umbrella-shaped style, which consists of a broadened and flattened umbrella canopy and a thin cylindrical umbrella stalk. Anatomical and micromorphological features of the style of Sarracenia purpurea L. were studied using light microscopy and scanning electron microscopy. This study found that the pollen tube transmitting tracts (PTTTs) start as a semi-solid canal filled with endotrophic conducting tissue, and run from the peripheral to the center of the canopy where the PTTT becomes a hollow canal supported by ectotrophic conducting tissue. The presence of stomata on the epidermis of the canopy and chloroplasts in its ground parenchyma indicate photosynthetic activities. Convex epidermal cells with intense cuticular striations on the canopy that are similar yet different from those on various regions of the sepals and petals indicate that it may provide contrasting visual cues for pollinators. Multicellular secretory glands and trichomes, which may provide olfactory cues and tactical cues respectively, are also found on the canopy. Thus, the stylar umbrella not only serves as a region for pollen grain capture, pollen germination, and pollen tube transmission but may also play an important role during pollinator–flower interactions.

Parapodial glandular organs in Owenia borealis (Annelida: Oweniidae) and their possible relationship with nephridia

Oweniidae is a basal group of recent annelids and nowadays it attracts the attention of researchers of many biological fields. Surprisingly, details of their anatomy, like the adult excretory system, remain obscure. Researchers recently suggested that the paired organs of tubeworms in the family Oweniidae are related to nephridia. In the current study of Owenia borealis adults, we determined that these structures are parapodial glandular organs (PGOs) and are located in the first two segments of adults. The PGOs are complex subepidermal multicellular glands that contain secretory cells, that is, goblet cells, which are differentiated by the type of the producing tube matter. The goblet cells are surrounded by muscles that are used to extrude material stored in the PGO's lumen into the external environment. The anterior pair of PGOs have very well-developed rough endoplasmatic reticulum in the proximal cells, spacious Golgi complexes, numerous nail-shaped microvilli, and apocrine secretory processes in the goblet cells of the distal parts. The posterior pair of PGOs only consists of cells, which probably produce proteinaceous fibrils. We discuss the homology of goblet cells with specific nail-shaped microvilli that produce β-chitin within annelids. We also discuss the possibility that PGOs and nephridia have a common origin. This study provides new information on the ultrastructure of cells that secrete the organic material used to form the tubes inhabited by tube-dwelling annelids.

Holocrine Secretion Occurs outside the Tight Junction Barrier in Multicellular Glands: Lessons from Claudin-1–Deficient Mice

Holocrine secretion is a specific mode of secretion involving secretion of entire cytoplasmic materials with remnants of dead cells, as observed in multicellular exocrine glands of reptiles, birds, and mammals. Here, we found that sebaceous glands in mice, representative of multicellular exocrine glands of mammals, exhibit a form of polarized stratified epithelium equipped with tight junctions (TJs), and found that holocrine secretion occurred outside the TJ barriers. Sebaceous glands share characteristics of stratified epithelia with interfollicular epidermis, including basal-layer-restricted cell proliferation, TJ barrier formation at a specific single layer of cells with apico-basolateral plasma membrane polarity, and cell death outside the TJ barrier. Knockout of claudin-1, a transmembrane adhesive protein in TJs, in mice caused leakage of the TJ barrier in sebaceous glands and incomplete degradation of the plasma membrane and nuclei during holocrine secretion. Claudin-1 knockout resulted in the accumulation of incompletely degenerated sebocytes in sebaceous ducts, suggesting that the TJ barrier was necessary for differentiation of holocrine secretion. The redefinition of sebaceous glands as TJ-forming stratified epithelia provides an important framework to understand the molecular mechanism of holocrine secretion.

Anatomical and Phytochemical Studies on Benincasa hispida (Thunb.) Cogn. (Cucurbitaceae)

The morphological and anatomical studies of Benincasa hispida (Thunb.) Cogn. from Nigeria was carried out with the view to reporting morphological and anatomical characteristics for the first time. Physical and microscopic (microtomy) observations were used. B. hispida is a monoecious climbing or trailing herb, stem hairy, 5-angled, with suborbicular stipuliform bract at the petiole-base; leaves simple, very hairy on both surface, alternate, blade palmately or ovate in young plant, base cordate. Flowering occurs between April and May. Female flowers solitary, male flowers solitary or in a slender-pedunculate racemes, petals-5, cream, yellow or pale yellow, ovary ellipsoid, ovules many, stigma 3-lobed and stamen 3. Fruits are large, weighs 8.5 - 9.0 kg, succulent, densely hairy when young, with a thick waxy deposit when mature, cylindrical to oblong with hairy stalk. Seeds are ovate-obovate, cream. Leaves and petals of male flower are amphistomatic with anomocytic, tetracytic and anisocytic stomata while petals of the female flower are hypostomatic with anomocytic stomata only on the abaxial surface. It has glandular and non-glandular trichomes with uniseriate stalk, clavate and multicellular gland heads. The midrib, petiole, stem, tendril, male and female flower stalks and tendril have hollow pith with 3, 9, 6-7, 16, 14 and 10 bicollateral vascular bundles respectively. The percentage crude protein, ash, carbohydrate, lipid, crude fibre, alkaloid, flavonoid, tannin and phytate could account for the numerous medicinal properties.

Sodium is the critical factor leading to the positive halotropism of the halophyte Limonium bicolor

Previous studies indicate that the roots of nonhalophytes showed negative halotropism to salt stress to avoid salt damage. However, halotropism of euhalophytes and their possible reasons are little known. Limonium bicolor, a typical recretohalophyte with multicellular salt glands, was used to study halotropism compared with Arabidopsis thaliana under NaCl, KCl and Na2SO4 stress. The elongation of the roots in L. bicolor was significantly promoted by the appropriate concentrations of NaCl, KCl and Na2SO4, but those of A. thaliana was markedly inhibited. However, isosmotic mannitol with 200 mM NaCl did not affect the root growth of both L. bicolor and A. thaliana. The root activity of both L. bicolor and A. thaliana was enhanced by salts. Compared with K+, Cl–, and SO42−, Na+ played a critical role in halotropism of L. bicolor. Furthermore, the gravitropic setpoint angle of L. bicolor increased under NaCl, KCl and Na2SO4 treatments compared with controls, and the phenomenon was most apparent under NaCl treatments. The endogenous IAA content of the NaCl-treated L. bicolor seedlings was significantly higher than that of the controls. These results suggest that the recretohalophyte L. bicolor has positive halotropism and Na+ plays a pivotal role in L. bicolor’s positive root halotropism by regulating IAA.

Getting to the root of scales, feather and hair: As deep as odontodes?

While every jawed vertebrate, or its recent ancestor, possesses teeth, skin appendages are characteristic of the living clades: skin denticles (odontodes) in chondrichthyans, dermal scales in teleosts, ducted multicellular glands in amphibians, epidermal scales in squamates, feathers in birds and hair-gland complexes in mammals, all of them showing a dense periodic patterning. While the odontode origin of teleost scales is generally accepted, the origin of both feather and hair is still debated. They appear long before mammals and birds, at least in the Jurassic in mammaliaforms and in ornithodires (pterosaurs and dinosaurs), and are contemporary to scales of early squamates. Epidermal scales might have appeared several times in evolution, and basal amniotes could not have developed a scaled dry integument, as the function of hair follicle requires its association with glands. In areas such as amnion, cornea or plantar pads, the formation of feather and hair is prevented early in embryogenesis, but can be easily reverted by playing with the Wnt/BMP/Shh pathways, which both imply the plasticity and the default competence of ectoderm. Conserved ectodermal/mesenchymal signalling pathways lead to placode formation, while later the crosstalk differs, as well as the final performing tissue(s): both epidermis and dermis for teeth and odontodes, mostly dermis for teleosts scales and only epidermis for squamate scale, feather and hair. We therefore suggest that tooth, dermal scale, epidermal scale, feather and hair evolved in parallel from a shared placode/dermal cell unit, which was present in a common ancestor, an early vertebrate gnathostome with odontodes, ca. 420million years ago.

Morphological and anatomical study of stevia leaves (Stevia rebaudiana (Bertoni) Hemsley)

Topicality . Stevia rebaudiana (Bertoni) Hemsley is a perennial plant that originates from Paraguay and southern Brazil. In Ukraine the plant is cultivated. Stevia is a natural low-calorie sweetener with a wide range of health care properties. It is used as a hypoglycemic, anticarcinogenic, antioxidant, bactericidal, antiviral, anti-inflammatory and antihypertensive agent. Aim . The aim of our study was to analyse the morphological and anatomical structure of Stevia rebaudiana (Bertoni) Hemsley leaves. Materials and methods . Stevia leaves were harvested on the research area of the cultural flora department of M. M. Gryshko National botanical garden NAS of Ukraine during the mass blossoming of plants in 2016. Specimens production was carried out by conventional methods. We used a microscope MC 10 (glasses X5, X10, 15, lenses X10, X40). Photomicrographs were made with a camera Samsung PL50. We analysed the agents of epidermis from the surface (edge, the middle of the upper and lower sides of the leaf blade, its cross cut), cross cuts of a petiole. Results and discussion . Morphological structure : leaves are opposite, short, without stipules, lanceolate or ovoid, with a serrated edge, gently wrapped down. Reticulated nervation. The leaf is more pubescent on the lower side, over the nerves and along the edge of the leaf blade. The leaves are more pubescent on the top of the plant. The colour of the leaf blade on top is green and on bottom is a little lighter. The taste is sweet, spicy with a slightly bitter aftertaste. The smell is pleasant, fragrant. Microscopic analysis: epidermis of a leaf blade is covered with multicellular hairs and glands. The cells of the upper epidermis are with thin, sinuous walls, few stomata, anisocytic type. Many simple hairs of different thickness and length. The cells of the lower epidermis have sinuous walls and stroke cuticle, many stomata. The anatomical structure of the blade is amfistomatic, dorsiventral. On cross cuts the petiole is oval, with a small notch on the adaxial side and with small side wings. The main area of the petiole takes parenchyma. The leading system of the petiole consists of five rounded vascular bundles: one central, two lateral of about the same size and two small, located closer to the wings of the petiole. Bundles are collateral, with a small area of the phloem, small, without the mechanical elements. The epidermis of a petiole is with hairs and glands. Conclusions . The main morphological and anatomical characteristics of Stevia rebaudiana (Bertoni) Hemsley leaves were found on the basis of macro and microscopic analysis, that were used during the drafting of the quality control methods project on a new herb “Stevia leaves”.

Essential oil composition and leaf trichomes of Pegolettia baccharidifolia and Pegolettia retrofracta (Asteraceae)

The essential oils obtained by hydrodistillation from Pegolettia baccharidifolia Less. and P. retrofracta (Thunb.) Kies were studied for the first time, using GC/MS and GC/FID techniques. A total of 178 components were identified, representing between 85.3% and 100.0% of the total oils. Some differences were observed in the composition of the essential oils of the two species but pronounced differences were also observed between different provenances of P. baccharidifolia from geographically separated populations. Five compounds, δ-cadinene, caryophyllene oxide, T-cadinol, T-muurolol and δ-cadinol (=α-muurolol, torreyol) were present in almost all Pegolettia samples. Of interest was the discovery of thymyl and isothymyl derivatives in two populations of P. baccharidifolia from the Vanwyksdorp area which were mainly in a dormant growth stage. However, 8,9-dehydrothymol was also present in two samples of P. baccharidifolia (0.1 and 0.2% of total yield) that were taken from actively growing plants, and 8,9-dehydrothymol isobutyrate was present in P. retrofracta at 2.1%. All other thymyl and isothymyl derivatives (thymol isobutyrate, 8,9-dehydrothymyl isobutyrate, 8,9-dehydrothymol, isothymyl valerate, thymyl valerate, isothymol, 8,9-dehydroisothymol isobutyrate, 10-isobutyryloxy-8,9-dehydrothymol isobutyrate, and 10-acetoxy-8,9-epoxythymol isobutyrate) were found only in the two Vanwyksdorp populations. The two species differ markedly in the shape and margins of the leaves, as well as in their surface appearance (glossy and bright green in P. baccharidifolia, dull green in P. retrofracta). However, the leaf trichomes (multicellular glands, probably the site of essential oil production and/or accumulation) are very similar in both species.

Survey of Foliar Trichomes in Combretum Loelf. (Combretaceae) in Parts of West Africa

We studied the foliar trichome types, density and distribution among the genus Combretum Loelf. in parts of West Africa. Fresh and herbarium specimens were used. These specimens were fixed, peeled, trichome types identified and micro-photographed using a Leica WILD MPS 52 microscope camera on a Leitz Diaplan microscope. Generally, two major trichome groups were identified among these species studied. These include glandular trichomes: multicellular gland head with uniseriate stalk (MGU), cylindrical uniseriate clavate trichome (CUCT), unicellular gland with unisariate stalk (UGHU), cylindrical uniseriate trichome (CUT), paltate gland head (PGH) and combretaceous eglandular (non-glandular) conical trichome (long and short types). The eglandular trichome types were the most widely distributed trichome found in the species and could be used to distinguish the genus. They occurred in all the species studied except C. glutinosum and C. micranthum. Among the glandular trichomes, cylindrical uniseriate trichome was the most dominant occurring in 11 species namely; C. aculeatum, C. bracteatum, C. collinum subsp. binderianum, C. collinum subsp. hypopilinum, C. constrictum, C. capitatum, C. hispidum, C. nigricans, C. panuculatum, C. platypterum and C. zenkeri. This is followed by multicellular gland head with uniseriate stalk (MGU) trichome type which occurred in 9 species (C. bracteatum, C. collinum subsp. binderianum, C. collinum subsp. hypopilinum, C. constrictum, C. excelsum, C. hispidum, C. mooreanum, C. platypterum and C. racemosum). The trichome density varied from 1.25±0.44 trichomes per 100 cells to 600 trichomes per 100 cells. The distribution/occurrence, density and type of these trichomes formed dependable character for delimitating Combretum species. The findings of this study showed that trichomes provide good taxonomic characters useful for in differentiating the genus Combretum in West Africa.

Morphological Changes in Skin Glands During Development in Rhinella Arenarum (Anura: Bufonidae).

Avoiding predation is critical to survival of animals; chemical defenses represent a common strategy among amphibians. In this study, we examined histologically the morphology of skin glands and types of secretions related to chemical skin defense during ontogeny of Rhinella arenarum. Prior to metamorphic climax the epidermis contains typical bufonid giant cells producing a mucous substance supposedly involved in triggering a flight reaction of the tadpole school. An apical layer of alcianophilic mucus covers the epidermis, which could produce the unpleasant taste of bufonid tadpoles. Giant cells disappear by onset of metamorphic climax, when multicellular glands start developing, but the apical mucous layer remains. By the end of climax, neither the granular glands of the dorsum nor the parotoid regions are completely developed. Conversely, by the end of metamorphosis the mucous glands are partially developed and secrete mucus. Adults have at least three types of granular glands, which we designate type A (acidophilic), type B (basophilic) and ventral (mucous). Polymorphic granular glands distribute differently in the body: dorsal granular glands between warts and in the periphery of parotoids contain protein; granular glands of big warts and in the central region of parotoids contain catecholamines, lipids, and glycoconjugates, whereas ventral granular glands produce acidic glycoconjugates. Mucous glands produce both mucus and proteins. Results suggest that in early juveniles the chemical skin defense mechanisms are not functional. Topographical differences in adult skin secretions suggest that granular glands from the big warts in the skin produce similar toxins to the parotoid glands.

First Description of a Palatal Organ in Chimaera monstrosa (Chondrichthyes, Holocephali).

Chimaeroid fishes are the only extant Holocephali, a subclass of Chondrichthyes. We describe for the first time a well evidenced structure localized in the palate of the chimaeroid Chimaera monstrosa, here named a palatal organ (PO). Attention has been paid to the holocephalan head morphology, but there has been no mention of this particular organ in the literature. The PO is a soft-tissue mass located within a slight hollow in between the two vomerine toothplates, and it protrudes into the oral cavity, resembling the mammalian incisive papilla. It is characterized by dense connective tissue with abundant collagen and elastic fibers and no muscular tissue. The robust innervation but low density of taste buds suggest a role in gustation for the PO, but primary utility in general mechanical sensitivity likely implicated in food sorting. The presence of numerous multicellular serous glands in the anterior/dorsal part of the PO is quite surprising because, in gnathostome fish, the presence of multicellular glands within the mouth has been reported in only the rare case of teeth-associated venom glands. Hypothesized roles for these glands could include food lubrication, digestion and defense against pathogens. In the literature, the presence of a PO has been demonstrated in many published images of chimaeroid fishes, but has gone unnoticed. This trait could represent a peculiar characteristic of all or a subset of holocephalans.

Histological and ultrastructural reconstruction of ventral epidermal glands of Spio (Polychaeta, Spionidae, Annelida)

With present study, we confirm that the ventral structures on anterior and middle chaetigers of two species of Spio are special kind of intraepidermal multicellular glands. The general anatomy and coherence morphology of these ventral epidermal glands (VEGs) were 3D-reconstructed based on semithin section series. Specific anatomical characters were explored using electron microscopy, such as scanning electron microscopy for characterization of gland pores and transmission electron microscopy for investigation into cytoanatomical details. The VEGs are tubular or acinar; their pores are spherical or lens-shaped. The glands consist of three cell types: secretory cells, sheath cells and canal cells, forming and strengthening the short gland duct and the pore region. The secretory cells are tightly packed into a single-layered, curved glandular epithelium. Secretory cells are separated from each other by thin projections of interstitial sheath cells. The apices of the secretory and sheath cells surround a tubular or vase-shaped extracellular space, the reservoir. The reservoir is traversed by microvilli of the secretory and sheath cells. Two sorts of microvilli characterize the apex of secretory cells: slender, elongated ones located at the periphery (outer microvilli), and shorter but thicker ones, arranged in a distinct collar in the centre (inner microvilli). Secretion, encased in regular secretory granules and discharged only at the apex’ centre, is guided through the space enclosed by the collar of inner microvilli. Though also consisting of numerous cells, the VEGs of Spio spp. are not comparable to parapodial glands described in other spionid taxa since they remain in a strictly intraepidermal position, are distant from parapodia and contain sheath cells. Nonetheless, the VEGs are very helpful for taxonomic work on representatives of the genus Spio and closely related genera.

Effect of mercuric chloride on terrestrial slug Semperula maculata and histopathology of reproductive organs: a comprehensive study

Since the last few decades, terrestrial diversity is found to be under stress due to the contamination by various chemicals and gases of aquatic and agricultural media. The bioaccumulation of these compounds at certain concentrations in different tissues produces histopathological changes leading to behavioral changes in target animals. This study focused on terrestrial molluscan slug, Semperula maculata, against lethal concentrations of mercury chloride (HgCl2). Bioaccumulation of Hg was highest in ovotestis, while lowest in the molluscan penis. Histopathological changes were observed in the cellular arrangement of reproductive organs. Alterations in the penis and the dart gland included dilated unicellular, multicellular glands, and muscular dystrophy, dilated peripheral glandular cells, respectively; dilation being maximal in the prostate gland. Ovotestis showed depleted number of gametocytes. Vacoulized pre-vitellogenic oocytes with early vitellogenic oocytes were noted under light microscopy. Mercury produced toxicity on secretory functions and lowered the rate of reproduction in animals. Evidence indicates that Hg produced gamete degeneration, impacted reproductive capacity and survival of this species in the ecosystem.

A re‐examination and re‐evaluation of salamander orbital glands

The amphibian integument contains numerous multicellular glands. Although two of these, the nasolabial and orbital glands and the associated nasolacrimal duct (NLD), have historically received considerable attention, interpretation of the original observations can be problematic in the context of current literature. Salamanders, in particular, are frequently regarded as at least indicative of aspects of the morphology of the common ancestor to all extant tetrapods; hence, an understanding of these glands in salamanders might prove to be informative about their evolution. For this study, the orbitonasal region of salamanders from three families was histologically examined. Three themes emerged: (1) examination of the effect of phylogeny on the nasolabial gland and NLD revealed a combination of features that may be unique to plethodontid salamanders, and may be correlated to their nose-tapping behavior by which substances are moved into the vomeronasal organ; (2) ecology appears to impact the relative development of the orbital glands, but not necessarily the nasolabial gland, with smaller glands being present in the aquatic species; (3) the nomenclature of the salamander orbital gland remains problematic, especially in light of comparative studies, as several alternate possibilities are viable. From this nomenclatural conundrum, however, it could be concluded that there may be a global pattern in the location of tetrapod orbital gland development. Molecular questions in terms of ontogeny and genetic homology affect the nature of the debate on orbital gland nomenclature. These observations suggest that rather than reflecting an ancestral condition, salamanders may instead represent a case of specialized, convergent evolution.

Discovery and anatomy of the arenophilic system of cuspidariid clams (Bivalvia: Anomalodesmata)

The arenophilic system of anomalodesmatan clams comprises multicellular glands, muscular papillae, and radial lines of adhesive secretion, which glue sand grains and other extraneous particles to the external surface of the shell. The presence and morphology of these organs have been established in an increasing number of taxa, but arenophilic glands were not previously known to occur in the deep-sea, carnivorous family Cuspidariidae. Dissections, histological sections and ultrastructural examination of members of the cuspidariid genera Cuspidaria and Cardiomya revealed a functional arenophilic system positioned around the siphonal apparatus. Glands are contained in muscular papillae at the posterior tip of the siphonal sheath, from where they deposit their adhesive secretion onto the shell rostrum. Discovery of an arenophilic system in cuspidariid clams adds support to the idea that the glands are a synapomorphy of Anomalodesmata, secondarily absent in only one of the major component branches (the clade joining Thraciidae, Cleidothaeridae, and Myochamidae). Moreover, similarity between the arenophilic papillae we observed on the siphonal sheath of Cuspidaria, Cardiomya, and Myonera, and literature reports on the crown of tentacles of Multitentacula is puzzling and highlights the need for further studies of the latter genus.

Structure of the lateral pedal defensive glands of Trimusculus costatus (Gastropoda: Trimusculidae)

When attacked by predators or subjected to mechanical disturbance, trimusculid limpets, like many other marine pulmonates, produce white sticky mucus from glands located in the lateral regions of the headfoot. Histology and electron microscopy were used to describe the structure of the glands of Trimusculus costatus. Based on the histochemistry and appearance of their secretory products, three types of unicellular gland cell were identified. Type 1, which was the most prevalent and largest (up to 200 m � 30 mm), stained positively for neutral mucins only and had a secretory product that was electron-lucent. Types 2 and 3 were smaller (up to 50 mm) and stained positively for acidic, neutral and sulphated mucins as well as protein. The secretory product of Type 2 glands was homogenously electron-dense, whereas that of Type 3 was vesicular and granular in appearance. Each gland releases its contents by holocrine secretion through an opening between the epithelial cells. Unlike other marine pulmonates (Siphonariidae and Onchidellidae), T. costatus does not have large multicellular glands encapsulated in a well-developed muscle layer. Its glands are more similar in structure to those of some terrestrial pulmonates.