Epidermal Glands Research Articles

A novel epidermal gland type in lizards (α-gland): structural organization, histochemistry, protein profile and phylogenetic origins

AbstractChemical signalling is an essential component of the communication system of lizards, and epidermal glands are responsible for producing semiochemicals that regulate many behavioural interactions. Two types of epidermal glands have been previously described for lizards: follicular and generation glands. Generation glands are characterized by the aggregation of novel glandular cell types in the epithelium and the lack of a lumen or external pore. Despite the fact that several subtypes of generation glands have been recognized over the years, the morphology, taxonomic distribution, function and evolutionary origins of generation glands remain nearly unexplored in Neotropical clades. Here, we describe a novel escutcheon-type generation gland (‘α-gland’) for lizards of the South American family Tropiduridae, characterize its structural and ultrastructural organization, and study the homology of the constituent parts in a phylogenetic framework. The α-glands emerged in the ancestor of Eurolophosaurus, Plica, Strobilurus, Tropidurus and Uracentron, and are found in at least 39 species with diverse ecological habits. We preliminarily analysed the protein profile of α-glands and discovered differential expression of protein components between sexes. Our investigations change the general view about epidermal gland homology, leading us to argue that generation and follicular glands are possibly more closely related functionally and evolutionarily than previously thought.

Response to Tilic and Bartolomaeus’s Commentary on the original Research Paper “Unravelling the ultrastructure and mineralogical composition of fireworm stinging bristles” (Zoology, 144)

In their Commentary to our paper recently published in Zoology (Righi et al., 2021a), Tilic and Bartolomaeus question our findings that the chaetae of Hermodice carunculata (Annelida) are hollow and able to store and deliver venoms. They sustain the idea that inflammatory chemicals are secreted through epidermal glands and possibly exposed to predator trough wounds caused by the brittle chaetae. We provide evidence-based arguments in support of our considerations. The sample preparation procedures did not affect the native inner structure of unfixed fireworm chaetae, which is clearly hollow as supported by both ultrastructure observation and crystal-chemical analysis of constituents. Furthermore, our previous and more recent feeding bioassays and chemical analysis indicate both that chaetae retain strong deterrent capacities even when isolated from the body of H. carunculata, and that they contain venoms. The cellular mechanisms involved in fireworm chaeta storage and deliver of chemicals are still unstudied. We strongly believe that this lack of knowledge should draw further attention on H. carunculata biology, pursuing new hypotheses and studies based on the noteworthy information which has been obtained so far.

First data on the structure of tubes formed by phoronids

Phoronids are marine benthic animals that live in tubes in soft sediment or hard substrata; the phoronids form the tubes by digging or boring. Epidermal glands produce much of the material of the tube, which is completely imbedded in the soft sediment or hard substrata. The structure of phoronid tubes has not been previously studied in detail. In the current research, the morphology and microstructure of the tubes were studied by light microscopy, histology, and scanning electron microscopy for the following species: Phoronis ijimai, Phoronis svetlanae, Phoronis hipporcrepia, Phoronis australis, and Phoronopsis harmeri. In most of these species, the tube consists of an inner organic cylinder and an external layer. The inner organic cylinder is formed by three layers (inner, middle, and outer) of thin films. Each film is formed by fibers, whose thickness differs in different species. These fibers form a net, whose density is higher in digging phoronids than in boring phoronids. The middle layer is formed by highly compressed thin films. The outer layer is the densest portion of the inner cylinder and is associated with the external layer. The external layer is absent in some species (P. australis) but is well developed in digging phoronids. The differences in the organization of tube are consistent with the biology of each species and depend on the type of substrata and on the life style of the animal. Tube organization substantially differs between phoronids and sedentary annelids: the inner organic cylinder is much thicker in phoronid than in annelid tubes, and the fibers that form films are randomly oriented in phoronids but regularly oriented in annelids. In annelids but not in phoronids, inorganic particles in the external layer are usually surrounded and glued together by organic material. These differences may be used to distinguish phoronid tubes from annelid tubes in present-day benthic samples and also in fossil samples.

Proteins from femoral gland secretions of male rock lizards Iberolacerta cyreni allow self—but not individual—recognition of unfamiliar males

Individual recognition (IR) plays an important role in modulating social interactions of several animal species. IR may work at two fundamental levels: at class-level (CIR), if it allows group membership identification (e.g. familiar/unfamiliar), or at individual-level (true IR; TIR), if it allows uniquely recognizing conspecifics. Direct and indirect evidences suggest that many lizards are able to recognize conspecifics, notably using the secretions from femoral glands, specialized epidermal structures located in the cloacal region. Such secretions are made of a mix of lipids and proteins, the latter having been poorly studied but hypothesised to convey identity-related information. Using male Iberian Rock lizards, we set up bioassays to test the role of the protein fraction in IR, and specifically whether lizards: (1) can detect proteins from femoral glands, (2) can recognize their own proteins from those of an unfamiliar male (CIR) and (3) can distinguish between two unfamiliar protein signals (TIR). We found that femoral proteins can be actually detected, and the protein signal was enough to allow self-recognition, but not to distinguish between two unfamiliar males. These outcomes support the hypothesis that proteins from lizard femoral glands are used in intraspecific communication, at least at CIR level. The lack of TIR detection has three possible explanations: (1) finer IR abilities are actually absent in this species; (2) TIR requires a more complex and complete chemical signal or (3) a more prolonged and complete set of previous interactions among individuals is needed to lead to familiarity and TIR. The ability to individually distinguish conspecifics is at the basis of many social behaviours. While the sensorial channel through which individual recognition is achieved may vary, the structure of the signal is usually complex and it could be expected different components to play different roles, so which part of the signal is actually responsible for individual recognition? Lizards use the secretion of specialized epidermal glands for intraspecific chemical communication, including individual recognition. Being a mixture of lipids and proteins, we wondered if it was the protein fraction of the secretion (i.e. the heritable part) which conveys identity. Using male Iberian Rock lizards, we showed that proteins allow for self but not for true individual recognition, suggesting that a partial signature may be not enough.

<p class="HeadingRunIn"><strong><em>Astacopsidrilus hibernicu</em><em>s</em> sp. nov. (Phreodrilidae, Oligochaeta, Annelida) from Irish peatlands</strong></p>

The discovery of a large and flourishing population of Phreodrilidae in terrestrial peatlands in northwest Ireland was surprising on two counts: these oligochaete worms are usually aquatic and most of the species occur in the Southern Hemisphere. The phreodrilids were discovered in a project that targeted Enchytraeidae, therefore methods adapted to the investigation of enchytraeids could be applied, including the study of living animals and properly fixed whole mounts. DNA sequencing was also performed. All worms identified here belong to one species, new to science, and placed in the genus Astacopsidrilus, because of the ventral position of the spermathecal pores and the opening of the female funnels inside the spermathecal vestibule. Astacopsidrilus hibernicus sp. nov. is mainly distinguished by thick segmental cushions of epidermal gland cells on the dorsal side of the posterior body half. Male sexual organs and spermathecae are comparatively small and without the often-observed bizarre modifications common in species of this family. DNA sequencing yielded a fragment of the 16S rRNA gene. This is the first description of a phreodrilid species from Europe; the few previous recordings of this family in Ireland and the United Kingdom had been left unidentified.

Epidermal Gland Inspired Self-Repairing Slippery Lubricant-Infused Porous Coatings with Durable Low Ice Adhesion

The limited durability of slippery lubricant-infused porous surfaces (SLIPS) restricts their practical applications. Inspired by the epidermal glands of skins, we developed a facile approach to durable SLIPS with gland-like storage and release functions for icephobicity. By introducing a hybrid surfactant as a lubricant into the polydimethylsiloxane (PDMS) matrix, lubricant capsules were formed and mono-dispersed in the matrix, working as gland-like structures to release lubricant. The obtained SLIPS showed durable low ice adhesion strength and thermal durability simultaneously. In detail, the enhanced durability for icephobicity was demonstrated by 20 icing/deicing tests, in which the lubricant remains on the surface; the coatings showed negligible weight loss when stored at 100 °C for 60 h, displaying pronounced thermal durability of the slippery effect. Our current strategy sheds new light on a facile fabrication of mechanically and thermally durable SLIPS for icephobicity.

Ultrastructure of the epidermal gland system of Tetranchyroderma suecicum Boaden, 1960 (Gastrotricha: Macrodasyida) indicates a defensive function of its exudate

Although the phylum Gastrotricha is known and studied for more than 150 years, some cell types, tissues and organ systems are still not well understood in terms of their morphology, ultrastructure, function and role. One of these features is the epidermal gland system (EGS). As yet, there is just a single detailed electron microscopic investigation of the epidermal glands of the species Turbanella cornuta Remane, 1925, plus scattered ultrastructural data of few additional species. We comprehensively investigated the epidermal glands of Tetranchyroderma suecicum Boaden, 1960 by means of serial sectioning and transmission electron microscopy (TEM) and with scanning electron microscopy. Furthermore, light microscopical, confocal laser scanning microscopical and micro-computed tomographical (µCT) techniques were additionally used for this investigation. Computer programs for 3D-reconstructions were used to analyse the data obtained by TEM and µCT. Tetranchyroderma suecicum possesses up to 100, mostly pairwise arranged, glandulocytes. Each single-celled gland contains a large anastomosing secretory cistern with granular content, has a very electron-dense cytoplasm, a basally positioned nucleus, peripherally arranged mitochondria and a cuticulated, ‘chimney-like’ apical neck, which carries the cellular pore. Each merocrine glandulocyte is associated with an adjacent ciliated sensory cell. There is currently no coherent hypothesis of the glandulocytes’ functional role, but different ideas are discussed. We refer to evidence that the secretory product of the EGS of Tetranchyroderma suecicum most likely acts as a repellent against potential predators.

Seasonal Variations in Femoral Gland Secretions Reveals some Unexpected Correlations Between Protein and Lipid Components in a Lacertid Lizard

Animals modulate intraspecific signal shape and intensity, notably during reproductive periods. Signal variability typically follows a seasonal scheme, traceable through the expression of visual, acoustic, chemical and behavioral patterns. The chemical channel is particularly important in lizards, as demonstrated by well-developed epidermal glands in the cloacal region that secrete lipids and proteins recognized by conspecifics. In males, the seasonal pattern of gland activity is underpinned by variation of circulating androgens. Changes in the composition of lipid secretions convey information about the signaler's quality (e.g., size, immunity). Presumably, individual identity is associated with a protein signature present in the femoral secretions, but this has been poorly investigated. For the first time, we assessed the seasonal variability of the protein signal in relation to plasma testosterone level (T), glandular activity and the concentration of provitamin D3 in the lipid fraction. We sampled 174 male common wall lizards (Podarcis muralis) over the entire activity season. An elevation of T was observed one to two months before the secretion peak of lipids during the mating season; such expected delay between hormonal fluctuation and maximal physiological response fits well with the assumption that provitamin D3 indicates individual quality. One-dimensional electrophoretic analysis of proteins showed that gel bands were preserved over the season with an invariant region; a result in agreement with the hypothesis that proteins are stable identity signals. However, the relative intensity of bands varied markedly, synchronously with that of lipid secretion pattern. These variations of protein secretion suggest additional roles of proteins, an issue that requires further studies.

Comparative morphology of ultimate and walking legs in the centipede Lithobius forficatus (Myriapoda) with functional implications

BackgroundIn the context of evolutionary arthopodial transformations, centipede ultimate legs exhibit a plethora of morphological modifications and behavioral adaptations. Many species possess significantly elongated, thickened, or pincer-like ultimate legs. They are frequently sexually dimorphic, indicating a role in courtship and mating. In addition, glandular pores occur more commonly on ultimate legs than on walking legs, indicating a role in secretion, chemical communication, or predator avoidance. In this framework, this study characterizes the evolutionarily transformed ultimate legs in Lithobius forficatus in comparison with regular walking legs.ResultsA comparative analysis using macro-photography, SEM, μCT, autofluorescence, backfilling, and 3D-reconstruction illustrates that ultimate legs largely resemble walking legs, but also feature a series of distinctions. Substantial differences are found with regard to aspects of the configuration of specific podomeres, musculature, abundance of epidermal glands, typology and distribution of epidermal sensilla, and architecture of associated nervous system structures.ConclusionIn consideration of morphological and behavioral characteristics, ultimate legs in L. forficatus primarily serve a defensive, but also a sensory function. Moreover, morphologically coherent characteristics in the organization of the ultimate leg versus the antenna-associated neuromere point to constructional constraints in the evolution of primary processing neuropils.

First experimental evidence that proteins from femoral glands convey identity-related information in a lizard

Transferring identity-related information (IRI) to conspecifics may give advantage in effectively tuning intraspecific behaviour. Some lizard species use the secretions of specialized epidermal glands (femoral or cloacal) to convey IRI. Those secretions are made of lipids and proteins, the former been suggested to inform about signaller quality, the latter suspected to communicate IRI to conspecifics. Here, we tested the hypothesis that proteins broadcast IRI by analysing the movement patterns of 28 male common wall lizards (Podarcis muralis) under strictly controlled experimental conditions. Lizards were videotaped in plastic terraria where the substrate scent was manipulated by filling it with a solution bearing (i) the proteins extracted from the secretions of the tested lizard (SELF); (ii) the proteins from a never-met donor from other nearby populations (NON-SELF); and (iii) the solvent alone. Lizards showed higher behavioural response to the NON-SELF treatment with respect to both CTRL and SELF ones. Further, protein concentration did not affect behavioural response, suggesting an all-or-nothing effect. Both results agree with the hypothesis that proteins may be used in chemical communication and convey IRI, demonstrating for the first time that they can be used as intraspecific signal.

A new scent organ for Gymnodactylus lizards (Squamata: Phyllodactylidae) and an updated evolutionary scenario for the origin of squamate epidermal glands

A new scent organ for Gymnodactylus lizards (Squamata: Phyllodactylidae) and an updated evolutionary scenario for the origin of squamate epidermal glands

Nevus Sebaceous Syndrome

Nevus sebaceous (NS) is a hamartomatous disorder of the skin and adjacent tissues characterized by epidermal, follicular, sebaceous, and apocrine gland abnormalities. It occurs in approximately 1 in 1,000 live births. A hyperactivation of Ras pathways has been recently assumed to be the cause of this phenotype. NS lesions may be isolated or coupled with extracutaneous manifestations, mostly of the central nervous, ocular, and skeletal systems, or kidneys; in this case, the term “NS syndrome” is used. Cutaneous distribution of NS usually follows the linear patterns known as “lines of Blaschko,” with lines that do not follow the segmental trajectory of the peripheral sensory nerves but instead reflect the streams or trends of growth of embryonic tissues. Histological characteristics of the lesions appear to be actually more decisive than the clinical evaluation to distinguish between the types of epidermal nevus: the typical NS has both papillated epidermal hyperplasia and a predominance of subjacent abnormal follicular–sebaceous glands.Seizures, mental retardation, and/or cognitive developmental delay are the most common neurologic abnormalities associated with NS and usually are present within the first months of life; eye and skeletal involvement may be present as well.The definitive treatment of NS is full-thickness excision. However, the necessity and timing of excision to prevent possible future malignancy are not clear; lasers and photodynamic therapy are alternatives currently being explored for the treatment of NS, with varying degrees of success.

Lithobius (Monotarsobius) meifengensis, a new species of centipede from high altitude forest in central Taiwan (Chilopoda, Lithobiomorpha, Lithobiidae).

Lithobius (Monotarsobius) meifengensis sp. n. occurring at Mei-Feng Farm, Highland Experimental Farm of National Taiwan University, Nantou, Taiwan, is characterised by a male secondary sexual character on leg 15, a very large ventral swelling occupying almost 50% of the ventral surface of the femur; the gently curved apical region bearing approximately 20 short setae and numerous very small pores of flexo-canal epidermal glands. This male secondary sexual character is described for the first time in the genus Lithobius.

Histological evidence of a glandular tubercle at the abdominal tergite in three species of katydids (Orthoptera: Tettigoniidae)

Three species of Hyperophora Brunner von Wattenwyl have a tubercle on the second abdominal tergite with different external appearance among species. We predicted that the tubercles are a glandular structure for their morphology and anatomical position. In H. major Brunner von Wattenwyl and H. brasiliensis Brunner von Wattenwyl the tubercle is low and broad, whereas in H. minor Brunner von Wattenwyl it is high. In all species the tubercle does not have an external opening, but it has many chemosensory sensilla, evidenced by long setae with an internal cavity with a membrane-like content. The cuticular surface of the tubercle has many pores with ∼1–2μm in diameter scattered among the sensilla. On the inner surface of the tubercular region occur epidermal gland cells, evidenced by a mass of large globular cells with an irregular and well-developed nucleus with predominance of decondensed chromatin and a large nucleolus. The cytoplasm of these cells is rich in small clear vacuoles, and has an end apparatus, a feature of epidermal gland cells of class III. Each gland cell has a conducting canal that opens into a cuticular pore. These results support the hypothesis that the tubercles are indeed of glandular nature.

Reliable proxies for glandular secretion production in lacertid lizards

The epidermal glands of lizards are considered an important source of semiochemicals involved in lizard communication. Many features of the lizard epidermal gland system vary among and within species (e.g. gland number, size, and shape), and some are believed to reflect the degree of intra- and interspecific variation in glandular secretion production, and by extension, the chemical signalling investment of lizards. Traditionally, herpetologists estimate secretion production based on the number of glands or the size of the glands, rather than quantifying the amount of secretion produced. Still, the reliability of these proxies for secretion production has never been validated. Here, I explored the relationship among secretion production (in mass), pore size (surface area, diameter), and gland number in three species of lacertid lizards ( Acanthodactylus boskianus , Timon lepidus , Holaspis guentheri ), and tested which proxies predicted secretion production variation best, and examined whether the same trend is true for all species. The findings of this study show that the total secretion production of lacertids is highly variable among and within species. Variation in secretion production among-species (but not within-species) could partly be explained by variation in body size. While both measures of pore size were positively related with secretion production, my tests revealed the model with only pore diameter as contributing variable explaining absolute secretion production variation (both within and across species) as the best one. Although gland number appeared a suboptimal estimate for secretion production in the three lacertids under study, only family-wide, multi-species comparative tests counting large within-species sample sizes can provide further insight on the matter.

Anti-inflammatory Activity of the Epidermal Glandular Extract of Cyclosorus parasiticus in Experimental Animals

The present study was designed to establish scientific evidence for the traditional claim on the use of fern Cyclosorus parasiticus in the treatment of rheumatism (inflammatory disease). Anti-inflammatory activity of the acetone extract of epidermal glands was tested by two models, viz., carrageenan and egg albumin-induced hind paw oedema. Before that, acute toxicity was performed following the OECD guidelines. No mortality was observed in experimental animals to the acetone extract at the test dose of 2000 mg/kg b.w. p.o. There were no signs and symptoms of toxicities. Hence, the extract was considered to be safe. The acetone extract of the epidermal glands showed dose-dependent activity against the development of oedema in experimental rats compared to the standards. The acetone extract significantly reduced the paw volume (*P<0.001 at 200 mg/kg and *P<0.01 at 100 mg/kg) compared to control. The results of the investigation substantiate and provide scientific evidence for the traditional claim against rheumatism. However, isolation of the bioactive compound from the acetone extract and its scientific screening by pre-clinical and clinical methods is a prerequisite to translate the traditional claim into plant-based drug to treat rheumatism.

Flower anatomy related to blooming development of Berberis microphylla G. Forst Berberida microphylla G. Forst (berberidaceae)

Berberis microphylla G. Forst. is a Patagonian native shrub commonly named “calafate”, which has a growing economic potential due to its dark blue berries that are consumed fresh, as jams and preserves, and are used for the production of soft drinks and ice cream. Moreover, the fruits have a high content of carbohydrates, phenols and antioxidants. The objective of this work was to show the changes observed in the flower from the emergence in relation to the floral phases and the importance that they have on pollination and fertilization. During the anthesis, the nectar is excreted inside and outside of the petal through the epidermis of the secretory tissue. The epidermis of the stigma is papillae with cells of greater length in the periphery of this structure simulating an additional ring. Secretory tissue is also present on the area of the fusion carpel. During anthesis, the epidermis glands of the stigma showed active secretion and these conditions favor pollen grain germination. Germinated pollen grains were observed after 12 hours of pollination and ten days later the pollen tube reached the ovule area. Pollen tube grew surrounded the ovules and probably some of them already accomplished the fertilization.

Ultrastructure of the salivary glands in Lithobius forficatus (Myriapoda, Chilopoda, Lithobiidae) according to seasonal and circadian rhythms

The salivary glands (mandibular epidermal glands) of adult males and females of Lithobius forficatus (Myriapoda, Chilopoda) were isolated during spring, summer and autumn. In addition, the organs were isolated at different times of the day – at about 12:00 (noon) and about 00:00 (midnight). The ultrastructure of these organs depending on seasonal and circadian rhythms was analyzed using transmission and scanning electron microscopy and histochemical methods. The paired salivary glands of L. forficatus are situated in the vicinity of the foregut and they are formed by numerous acini that are surrounded by the fat body, hemocytes and tracheolae. The salivary glands are composed of a terminal acinar component and a system of tubular ducts that are lined with a cuticle. The glandular part is composed of secretory epithelial cells that are at various stages of their secretory activity. The saliva that is produced by the secretory cells of the acini is secreted into the salivary ducts, which are lined with a simple epithelium that is based on the non-cellular basal lamina. The ultrastructural variations suggest that salivary glands function differently depending on seasonal rhythms and prepare the animal for overwintering. Therefore, the salivary glands of the centipedes that were analyzed participate in the accumulation of proteins, lipids and polysaccharides during the spring, summer and autumn. Subtle differences in the ultrastructure of the secretory cells of the salivary glands during the circadian cycle must be related to the physiological reactions of the organism. The salivary ducts showed no differences in the specimens that were analyzed during the day/night cycle or during the seasonal cycle.

Notas sobreLimonium(Plumbaginaceae) en el Noroeste Ibérico, I:Limonium serpentinicum, Nueva Especie

As part of the ongoing investigation on the group that includes Limonium binervosum (G. E. Sm.) C. E. Salmon in the northwestern Iberian Peninsula, a new species (L. serpentinicum R. Pino, F. J. Silva-Pando & J. J. Pino) is described here. It is characterized by its small size, the occurrence of abundant epidermal glands along the stem, the acuminate outer bracts, and the very narrow internal bracts, and known for its tendency to grow on serpentine substrates.

A novel epidermal abdominal gland in the cricket Ectecous segregatus Gorochov, 1996 (Orthoptera: Grylloidea: Phalangopsidae)

Ectecous segregatus (Grylloidea: Phalangopsidae) presents a modification in some abdominal tergites hypothesized to be openings for epidermal glands. This feature however has been described in the literature only on the basis of its external morphology. This study describes the morphology of E. segregatus abdominal glands associated with cuticular modifications. Histological and ultrastructural data show the presence of abdominal glands in males of E. segregatus, represented by an epidermis with columnar cells classified as type I glands. This is the first study that shows the presence of an abdominal gland associated with external cuticular modifications in crickets.