Intramandibular Gland Research Articles

Morphology of the Mandibular and Intramandibular Glands of Army Ant Workers of Labidus praedator (Smith 1858) and Labidus coecus (Latreille 1802) (Formicidae: Dorylinae).

Social insects are characterized by having a wide diversity of exocrine glands, with highlights for ants with about 85 glands spreading throughout the body. The mandibular and intramandibular glands are associated with the production of pheromones. The army ants (Dorylinae) play an important role in the structure of the invertebrate community because they are efficient predators and provide suitable conditions for various animals following their invasions in the food search. Labidus coecus (Latreille) is an underground-ameliorating ant and Labidus praedator (Smith) is a generalist surface predator which can deplete invertebrate biomass by up to 75%. This work investigated the morphology of the mandibular and intramandibular glands of L. praedator and L. coecus workers. The glands were analyzed by light microscopy, histochemistry, and scanning electron microscopy. The mandibular and intramandibular glands of the two species were classified as class III glands. The data on the morphology of the mandibular glands has revealed that they have characteristics in common with other subfamilies. The intramandibular glands of the two species of Labidus have similar morphology and chemical composition, which indicates that the components of these glands can have the same function despite their different habits.

Survey of the exocrine glands in workers of the ant Leptanilla clypeata

Our morphological study of the exocrine system in workers of Leptanilla clypeata revealed the presence of at least 23 glands. Among these, the dorsoproximal intramandibular gland represents a novel structure for social insects. Another novel gland may exist in the ventral part of the postpetiolus; both the petiole and postpetiole contain conspicuous clusters of large gland cells. The occurrence of three epithelial glands associated with the 5th, 6th and 7th abdominal sternites clearly differs from the single sternal gland that occurs in other Leptanilla species or the related Protanilla. Several glands could be observed in the legs, although their number probably is an underrepresentation of the real situation. The function of most glands is still unknown and forms a challenge for further behavioural studies when live material of these elusive ants may become available again in future.

The ultrastructure of the intramandibular gland in soldiers of the termite Machadotermes rigidus (Blattodea: Termitidae: Apicotermitinae)

Machadotermes is one of the basal Apicotermitinae genera, living in tropical West Africa. Old observations suggested the presence of a new gland, the intramandibular gland, in Machadotermes soldiers. Here, by combining micro-computed tomography, optical and electron microscopy, we showed that the gland exists in Machadotermes soldiers only as an active exocrine organ, consisting of numerous class III cells (bicellular units made of secretory and canal cells), within which the secretion is produced in rough endoplasmic reticulum, and modified and stored in Golgi apparatus. The final secretion is released out from the body through epicuticular canals running through the mandible cuticle to the exterior. We also studied three other Apicotermitinae, Indotermes, Duplidentitermes, and Jugositermes, in which this gland is absent. We speculate that the secretion of this gland may be used as a general protectant or antimicrobial agent. In addition, we observed that the frontal gland, a specific defensive organ in termites, is absent in Machadotermes soldiers while it is tiny in Indotermes soldiers and small in Duplidentitermes and Jugositermes soldiers. At last, we could also observe in all these species the labral, mandibular and labial glands, other exocrine glands present in all termite species studied so far.

Morphology of the Novel Basimandibular Gland in the Ant Genus Strumigenys (Hymenoptera, Formicidae).

Simple SummaryAnts form a diverse group of social insects that are characterized by an overwhelming variety of exocrine glands, that play a key function in the communication system and social organization of the colony. Our focus goes to the genus Strumigenys, that comprise small slow-moving ants that mainly prey on springtails. We discovered a novel gland inside the mandibles of all 22 investigated species, using light and electron microscopy. As the gland occurs close to the base of the mandibles, we name it ‘basimandibular gland’ according to the putative description given to this mandible region in a publication by the eminent British ant taxonomist Barry Bolton in 1999. The gland exists in both workers and queens and appeared most developed in the queens of Strumigenys mutica. These queens in addition to the basimandibular gland also have a cluster of gland cells near the tip of their mandibles. The queens of this species enter colonies of other Strumigenys species and parasitize on them. We expect that the peculiar development of these glands inside the mandibles of these S. mutica queens plays a role in this parasitic lifestyle, and hope that future research can shed more light on the biology of these ants.In 1999, Barry Bolton postulated the presence of a basimandibular gland in the mandibles in all species of the ant genus Strumigenys, solely based on scanning microscopy observations. We now confirm the presence of this putative gland in the proximal outer part of the mandibles of 22 investigated species by histological and ultrastructural examination, including 10 short- and 12 long-mandibulate species. All species have a basimandibular gland, that is formed by 15–25 µm thick epithelial cells and belongs to class-1 following the standard classification of insect exocrine glands. We consider it a novel gland because of its peculiar bowl-shape and special arrangement of the microvilli that are confined to large vacuolar spaces instead of reaching the cuticle. The gland is most pronounced in S. mutica, particularly in the queen. In addition to this gland, we also found scattered class-3 intramandibular gland cells in the mandibles. Queens of S. mutica are peculiar in having a cluster of these cells in the distal tip of their mandibles. As this species is a social parasite, further research is required to determine whether the development of these mandibular glands is related to its parasitic lifestyle.

Description of the Intramandibular Gland II in Polybia emaciata Lucas (Hymenoptera, Vespidae)

The intramandibular gland II in Polybia emaciata Lucas is described. This species is among the few that uses mud for nest construction, and their nests persist for a long time following abandonment. The intramandibular gland II has been found in single representatives of the genera Mischocyttarus, Apoica and Leipomeles, and this record is the second for the genus Polybia. Despite expectations derived from the nest characteristics of the species, gland dimensions such as cell diameter were well within the range observed for other species, with the cell number even comparatively small. Gland function remains to be investigated.

Post-embryonic development of intramandibular glands of Friesella schrottkyi (Friese, 1900) (Hymenoptera: Apidae) workers

Exocrine glands play important role in social organization of insects, such as caste and inter-caste differentiation. Due their functional and structural plasticity, morphological studies on such glands contribute to better understanding the biology of social bees. Therefore, the aim of the study was to characterize the sequence of the post-embryonic development of intramandibular glands of Friesella schrottkyi (Friese, 1900) (Hymenoptera: Apidae) workers using histological and histochemical analyses. The mandibles of pupae at different developmental stages and newly emerged adults were analyzed. The intramandibular glands of F. schrottkyi presented two types: class I glands, in the mandible epidermis and class III glands, inside the mandible cavity that open onto external surface. The intramandibular glands of F. schrottkyi developed during the transition from the prepupae to the white-eyed pupae, as shown by the morphological changes. Black-eyed pupae of F. schrottkyi presented fully developed intramandibular glands.

A novel intramandibular gland in the ant Brachyponera sennaarensis

One of the diagnostic characters of the ponerine ant genus Brachyponera is the presence of a mandibular pit near the insertion of the mandible. This paper describes the morphology and ultrastructure of a novel intramandibular gland in B. sennaarensis, that is associated with this pit. The gland appears as a conspicuous epithelium that lines the invaginated cuticle of the pit, and that extends distally into the upper and lower outer wall of the mandible. This novel ‘mandibular pit gland’ occurs in both workers and queens, but is absent in males. At the ultrastructural level, the cytoplasm of the cylindrical secretory cells is dominated by a well-developed smooth endoplasmic reticulum. Apical microvilli and clear transcuticular channels allow secretion to reach the mandibular surface. Although the function of this novel gland is not yet known, the cytoplasmic organization is in line with the production of a pheromonal secretion.

The function of intramandibular glands of the antNeoponera villosa(Fabricius, 1804) (Hymenoptera: Ponerinae)

In social insects, secretions of the exocrine gland may modulate their behavior. Although many glands have their functions elucidated, this is absent for the intramandibular glands in ants. To study the function of intramandibular gland secretions in the ant Neoponera villosa, its compounds were subjected to behavioral analyses. These analyses revealed a significant increase in the walking time of ants exposed to the nestmate mandible extract. The results suggest that intramandibular gland compounds of N. villosa may play the role of alarm or scent trial pheromones.

Uncovering head gland diversity in neotropical Polistinae wasps (Hymenoptera, Vespidae): Comparative analysis and description of new glands

Exocrine glands are involved in several wasp colony activities; however, the number of known glands in the Vespidae is rather low when compared to other social insect groups. The aim of this study is to survey the head of Neotropical social wasps and to provide a detailed comparative study of the glands found in the Polistinae. A total of 33 species distributed over 13 genera were studied with serial histological sections of the head, excluding the labiomaxillary complex. Additionally, the exoskeleton was explored using scanning electron microscopy looking for associated modifications. A total of eleven exocrine glands were observed, five are structures recorded for the first time for the Hymenoptera, three are new records for the Polistinae and three are previously known organs. The glands studied are: ocellar gland I, ocellar gland II, periocular gland, subantennal gland, hypopharyngeal gland, clypeal gland, posterobasal genal gland, ectal mandibular gland, mesal mandibular gland, intramandibular gland I, and intramandibular gland II. The widespread distribution of most of these glands suggests an origin prior to the evolution of the Polistinae. Our results highlight the importance of detailed morphological studies to unveil the significance of chemical communication in one of the most characteristic groups of social animals.

Chemical composition of the intramandibular glands of the ant Neoponera villosa (Fabricius, 1804) (Hymenoptera: Ponerinae)

Products of exocrine glands modulate the behavior of social in sects. Among the exocrine glands, the function of intramandibular glands has not been well characterized in social Hymenoptera. To study the effects of exocrine gland secretions on the behavior of the ant, Neoponera villosa, identification of cuticular and intramandibular gland compounds was performed. Fifteen different compounds were identified in workers and queens of N. villosa. Linear alkanes C26, C27, C28, C30 and C36, as well as the methyl alkanes 13-, 11- MeC28, 3 MeC29, 13-, 11- MeC32, 13-, 11- MeC33, 13- MeC36, 13,17-; 15,19-DiMeC37 and 18-, 17-, 13-MeC38 and esters triacontyl acetate were found on the body and mandible surface of both workers and queens. The sterols, cholesterol and sitosterol were found only in the mandibles, with cholesterol present in both workers and queens, and sitosterol present only in queens. The results suggest that intramandibular gland compounds of N. villosa may play a role in worker activity. The presence of hydrocarbons and cholesterol in workers and sitosterol in the mandible of queens may be associated with caste profile.

Exocrine glands of the antMyrmoteras iriodum

This paper describes the morphological characteristics of nine major exocrine glands in workers of the formicine ant Myrmoteras iriodum. The elongate mandibles reveal along their entire length a conspicuous intramandibular gland, which contains both class-1 and class-3 secretory cells. The secretory cells of the mandibular glands show a peculiar appearance, with a branched end apparatus, which is unusual for ants. The other major glands (pro- and postpharyngeal gland, infrabuccal cavity gland, labial gland, metapleural gland, venom gland and Dufour gland) show common features for formicine ants. The precise function of the glands could not yet be experimentally demonstrated, and to clarify this will depend on the availability of live material of these enigmatic ants in future.

Morphology of mandibular and intramandibular glands in workers and virgin queens of Melipona scutellaris

The interactions of insect societies are associated with chemical signals released by the exocrine glands that control some insect behaviors. Exocrine glands can be classified into different classes: class I release substances that cross the body cuticle and class III glands that have a conducting canal. This study compares the morphology of intramandibular and mandibular glands in virgin queens of different ages, as well as in nurses and forager workers of Melipona scutellaris. We have found the occurrence of two types of glands inside the mandible; glands of class I, corresponding to a well-developed epithelium, secretory only in virgin queens, and glands of class III. On the other hand, mandibular glands have been found to be well-developed in workers and queens and they also have high amounts of mitochondria and smooth endoplasmic reticulum. Together, these data show that the mandibular and intramandibular glands of M. scutellaris virgin queens have morphological features that indicate the synthesis of compounds that are lipid in nature. Furthermore, both glands have a similar developmental degree in newly emerged and 7-day-old ones.

Post-embryonic Development of Intramandibular Glands in Pachycondyla verenae (Forel) (Hymenoptera: Formicidae) workers

The current knowledge of intramandibular glands in Hymenoptera is focused on occurrence and morphology in adult insects. This is the first report regarding the post-embryonic development of intramandibular glands in a “primitive” ant, Pachycondyla verenae. In this study, we analyzed mandibles of prepupae, white-eyed, pink-eyed and black-eyed pupae, pupa of pigmented body pupae, and adults. Adult workers of P. verenae have intramandibular glands with epidermal secretory cells of class I and isolated glands of class III, and both glands have onset differentiation in pink-eyed pupae. Some histological sections were submitted to histochemical test for total proteins and neutral polysaccharides. Histochemical tests showed occurrence of polysaccharides and proteins in epidermal secretory cells of class I from the white-eyed pupae, polysaccharides and proteins in pink-eyed pupae to black-eyed pupae in both glands classes I and III and presence of polysaccharides in adult ants also in both gland classes I and III. Intramandibular glands of classes I and III in P. verenae workers differentiate during pupation, with onset occurring in pink-eyed pupae, and completion occurring in black-eyed pupae.

Ultrastructure of the Intramandibular Gland of Workers and Queens of the Stingless Bee,Melipona quadrifasciata

The intramandibular glands of workers and queens of Melipona quadrifasciata Lepeletier (Hymenoptera: Apidae), at different ages and from different functional groups, were studied using light and transmission electron microscopy. The results demonstrated that these glands are composed of two types of secretory structures: 1.A hypertrophied epidermis on the dorsal side of the mandible that is an epithelial gland. 2. Free secretory cells filling the inner spaces of the appendices that constitute a unicellular gland. The epithelial gland is larger in the young (1-2-day-old workers), and the gland becomes involuted during the nurse worker stage. The unicellular glands of the workers posses some secretion during all of the studied phases, but secretory activity is more intensive in the foraging workers. Vesicles of secretion are absent in the unicellular glands of queens. These results demonstrate that these glands show functional adaptations in different castes corresponding to the functions of each caste.

Morphology and histochemistry of the intramandibular glands in Attini and Ponerini (Hymenoptera, Formicidae) species

An understanding of the internal morphology of the ant mandible is important in explaining the relationship between the exocrine system and the behavioral and phylogenetic characteristics of different subfamilies of Formicidae. In this study, we investigated the occurrence of intramandibular glands in ants from the Ponerini (Ponerinae) and Attini (Myrmicinae). These ants possess glands from classes I and III, and secretory epithelial cells with a reservoir. The intramandibular glands show a distinct histology in the studied species, varying in their location, degree of development, and chemical content. Using this information, it is possible to hypothesize that the glands from different tribes produce different substances, which may indicate a variety of functions, depending on the chemical nature of the cellular constituents. A cladistic analysis using the characters of the intramandibular glands separated both tribes, suggesting that structural differences in the intramandibular glands may contribute to future phylogenetic studies of the Formicidae.

Morphology of the Head Salivary and Intramandibular Glands of the Stingless BeePlebeia Emerina(Hymenoptera: Meliponini) Workers Associated with Propolis

AbstractPlebeia emerina (Friese) (Hymenoptera: Meliponini), like other stingless bees, collect large amounts of vegetal resin and store these materials, called propolis, in individualized clusters inside the nest that remain in a viscous state. The development of intramandibular and head salivary glands in P. emerina workers was studied in different life stages, aiming to relate gland functionality with the age in which they work at propolis maceration, biting the propolis clusters with the mandibles. The morphology of intramandibular and head salivary glands from newly emerged, 20–30 d old, and forager bees was analyzed. The greatest size of the head salivary glands occurred in 20–30-d-old worker bees, and the ultrastructure of this gland showed the presence of rough endoplasmic reticulum and lipid droplets. The intramandibular glands were of two types: glandular units (class 3 glands), present throughout the worker bee life span, and the secretory epithelium (class 1 glands), which hypertrophies in 20–30-d-old and forager bees. The development of the head salivary glands and the mandibular epithelium suggest that their products are added to the propolis clusters, supporting the hypothesis that they may serve in maintaining its viscous state.

Volatile chemical release by bethylid wasps: identity, phylogeny, anatomy and behaviour

The structures of volatile chemicals released by parasitic wasps in the family Bethylidae are shown to correspond to the subfamily to which the species belong. Species in the Epyrinae release skatole (3-methylindole) and species in the Bethylinae release a spiroacetal (2-methyl-1,7-dioxaspiro [5.5]undecane): these compounds are chemically very different. The enantiomeric composition of the spiroacetal differs between congeneric species. Chemical release is a discrete event under the active control of both male and female wasps. Structural differences between the mandibular glands and intramandibular glands suggest the mandibular glands to be the source of released volatiles. Real-time mass spectrometry shows that the spiroacetal is released by Goniozus nephantidis females during dyadic resource contests, with release more common during more aggressive interactions. Chemical tagging with deuterium further shows that the volatile is released by the loser of an agonistic interaction and not the winner. The function of spiroacetal and skatole release by bethylids is discussed.

The intramandibular gland of leaf-cutting ants (Atta sexdens rubropilosa Forel 1908)

The eusociality developed in Hymenoptera and Isoptera is driven by an efficient interaction between exocrine glands and jointed appendages, both in close interaction with the environment. In this context, the mandible of ants plays an important role, since, in addition to being the main jointed appendage, it possess glandular functions. As an example we might name the two glands associated with the mandible: the mandibular and the intramandibular glands. The intramandibular gland is found inside the mandible and consists of a hypertrophied secretory epithelium and secretory cells in the mandible's lumen. The secretion of the secretory epithelium is liberated through intracuticular ducts that open at the base of hairs at the mandible's surface. The secretion of the intramandibular gland (epithelium and secretory cells) reacted positively to tests for the detection of polysaccharides and proteins, thus suggesting that it consists of glycoproteins. The ultrastructure of the secretory epithelium presents variations related to the developmental stage of the individual, showing a large number of ribosomes and microvilli close to the cuticle in young individuals, while in the older specimens it was possible to note the formation of an intracellular reservoir. These variations of secretory epithelium, as also the interaction between the cellular groups inside the mandible, are important information about this gland in leaf-cutting ants.

Mandible associated glands in queens of the slave-making ant Polyergus rufescens (Hymenoptera, Formicidae)

A first description of the structural organization of two exocrine glands associated with the mandibles of queens of the obligatory slave-making ant Polyergus rufescens is reported. The mandibular gland consists of clustered bicellular secretory units connected by means of cuticular ducts to a big reservoir. The reservoir continues in a duct that opens proximally on the mandible cuticle. Intramandibular glands are isolated bicellular secretory units connected to the external pores through a cuticular duct. No reservoir has been observed. In both cases the secretory cells belong to the 3rd class. Functional aspects of the investigated glands are discussed taking also into account for the parasitic habit of this slave-making species.

The intramandibular gland, a novel exocrine structure in ants (Insecta, Hymenoptera)

A novel glandular structure is described within the mandibles of a series of representatives of the Formicidae. It consists of a variable number of secretory cells with their accompanying duct cells, located in the vicinity of the mandibular cuticle. Because of its localization inside the mandibles, we propose to designate this structure as the intramandibular gland of ants. Ultrastructural observations reveal the development of smooth endoplasmic reticulum in the glandular cells. Several electron-lucid and electron-dense inclusions occur in the cytoplasm. Until now, the function of this widespread gland among the Formicidae remains unknown.