Johan Billen

Johan Billen
KU Leuven | ku leuven · Department of Biology

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297
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Publications

Publications (297)
Article
Full-text available
The morphology of the infrabuccal pocket has been studied with light and electron microscopy (SEM, TEM) in 19 species of Strumigenys ants. The structural organization is similar in workers, queens and males, and supports the involvement of the pocket in the filtration of food particles before they can enter the digestive tract. A carpet of posterio...
Article
Social insects present a great diversity of exocrine glands, which are linked to fundamental roles of social life, and their morphological characterization represents the first step toward the knowledge of their function. We here describe the exocrine glands present in the sting apparatus of queens and workers of the wasp Protopolybia exigua. Histo...
Article
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 conspicuou...
Article
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Recent studies of insect anatomy evince a trend towards a comprehensive and integrative investigation of individual traits and their evolutionary relationships. The abdomen of ants, however, remains critically understudied. To address this shortcoming, we describe the abdominal anatomy of Amblyopone australis Erichson, using a multimodal approach c...
Article
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Many social wasps in the speciose subfamilies Polistinae and Vespinae have two sternal glands—the van der Vecht gland and the Richards gland—that are not found in other insects. The presence of these glands has been confirmed in only 6 of 22 hornet species (genus Vespa) and images of their fine structure have not been produced. Here; we characteriz...
Article
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Previous evidence suggests that cicadas lacking Hodgkinia may harbour the yeast-like fungal symbionts (YLS). Here, we reinforce an earlier conclusion that the pathogenic ancestor of YLS independently infected different cicada lineages instead of the common ancestor of Cicadidae. Five independent replacement events in the loss of Hodgkinia/acquisiti...
Article
Full-text available
The activities of social insect colonies are supported by exocrine glands and the tremendous functional diversity of the compounds that they secrete. Many social wasps in the subfamilies Vespinae and Polistinae have two sternal glands—the van der Vecht and Richards’ glands—that vary in their features and function across the species in which they ar...
Article
Exocrine glands in the legs of social insects are found throughout all leg segments, but studies of exocrine glands in legs of solitary insects are very limited. We discovered a novel gland at the apex of the fore, mid and hind femurs from six representative species of Cicadidae, which we propose to name as the epithelial femoral gland. The epithel...
Article
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Many insects depend on symbiont(s) for survival. This is particularly the case for sap‐feeding hemipteran insects. In this study, we revealed that symbionts harbored in cicadas are diverse and complex, and the yeast‐like fungal symbionts (YLS) are present in most cicada species but Hodgkinia is absent. During vertical transmission, Sulcia became sw...
Article
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The foundation of new ant colonies often involves a solitary phase for the newly mated queens. These queens are subject to high food stress during this period that can last several weeks or months until the appearance of the first workers. The food stress is mainly associated with egg laying, larval feeding, and the queens' own metabolism. The flig...
Article
We describe a novel ventral scape gland in all 19 species of the genus Strumigenys that we examined, confirming the postulated existence of this gland by Bolton (1999). The gland occurs in workers and queens; it belongs to ‘class-1’ and is formed by a layer of epithelial secretory cells that line the ventrodistal tegumental cuticle of the antennal...
Article
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The hypogaeic ant subfamilies Leptanillinae and Martialinae likely form the sister group to the remainder of the extant Formicidae. In order to increase the knowledge of anatomy and functional morphology of these unusual and phyloge-netically crucial ants, we document and describe in detail the cranium of a leptanilline, Protanilla lini Terayama, 2...
Article
Parasites modify their host's appearance, behaviour and physiology to a certain extent. Many of these modifications are seen as purposefully manipulative, serving the parasite's interest. Endgames are particularly intriguing, where the parasite's development requires the host's death. ‘Summit’ or ‘treetop’ disease is one of such spectacular example...
Article
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The mandibular gland of ants releases chemical compounds with functions ranging from nestmate alarm and recognition to antimicrobial defense. While the morphology of this ethologically important gland is well investigated in several species, the mechanism of secretion release in ants was not explicitly addressed so far. To clarify this question, we...
Article
The basitarsus of the mid-and/or hindlegs of several Amblyoponinae ants shows a deep longitudinal groove or sulcus on its anterior face in workers and queens. Histological examination reveals this sulcus is associated with a conspicuous novel epithelial gland, which brings the number of exocrine glands in the legs of ants to 25. The ultrastructural...
Article
Many of the phenotypic manifestations present in social insects are related to the development of exocrine glands, well represented by the nest-building behaviors. Among bees, four tribes compose the corbiculate bees, including both solitary and eusocial species: Apini, Bombini, Euglossini and Meliponini, which use wax as an endogenous product to c...
Article
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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 examinat...
Chapter
Full-text available
A great diversity of exocrine glands is found in social insects. The main social function of exocrine glands is the production of pheromones, which are related to the maintenance of social organization of the colony, as interactions of dominance, maintenance of queen status, recruitment for food, search for nesting sites, defense, and reproductive...
Article
Workers, queens and males of all examined Discothyrea species of the ‘sauteri group’, that have laterally expanded frontal lobes and well-developed antennal scrobes, are characterized by two hairy areas on the outer surface of their procoxae. Histological and ultrastructural examination of Discothyrea sauterirevealed that each of these areas is ass...
Article
In this study, we investigated the morphological characteristics of three glands that are associated with the labium and the maxillae in the female castes as well as males of the ant Camponotus japonicus Mayr, 1866 using serial semithin sections and scanning electron microscopy (SEM). We propose to name these glands as the postmentum base gland, th...
Article
The horned gall aphid, Schlechtendalia chinensis, inhabits the productive species of Chinese gallnuts, which have economic value. Aphid wax glands are crucial for the survival of the insects, since the secreted waterproofing wax is important to protect the aphids from predators, pathogens and honeydew contamination. In this study, we investigated t...
Article
As in other Hymenoptera, adult ants cannot secrete silk, unlike the larvae that spin a cocoon prior to metamorphosis. Fisher and Robertson (1999) first showed the existence of a silk gland in the head of adult Melissotarsus beccarii workers, and we confirm this with detailed histology and ultrastructural comparisons of both queens and workers. This...
Article
Invasive species have major impacts on biodiversity and are one of the primary causes of amphibian decline and extinction. Unlike other top ant invaders that negatively affect larger fauna via chemical defensive compounds, the Argentine ant (Linepithema humile) does not have a functional sting. Nonetheless, it deploys defensive compounds against co...
Article
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Abstract. An organism’s morphology plays a crucial role in its interactions with its environment. Therefore, comparative anatomical analysis is a critical basis to understanding the ecology, behavior, and evolution. While our knowledge of ant internal anatomy has con-siderably improved in recent years, it is still highly fragmentary, and many evolu...
Article
The potential utility of RNA interference (RNAi) to control insect pests and viral infections depends largely on the target organism's ability to systemically spread the RNAi response. The efficacy of systemic RNAi varies among insects, though it has been shown to be high in the red flour beetle, Tribolium castaneum. We identified an extracellular...
Article
We collected a queenright colony of the very rare Myopias conicara Xu in Vietnam (1 dealate queen, 41 workers and 38 larvae). Both the queen and workers fed on xystodesmid millipedes. After paralyzing a millipede, its head was first removed by the workers, and then the larvae were put on the opening of the collum (anteriormost ring of the trunk). A...
Article
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Ants are a dominant insect group in terrestrial ecosystems and many myrmecophilous species evolve to associate with ants to gain benefits. One iconic example is myrmecophilous butterflies that often produce ant-mimicking vibrational calls to modulate ant behaviors. Despite its popularity, empirical exploration of how butterflies utilize vibrational...
Article
The infrabuccal pocket (IBP) is a peculiar structure in ants whose detailed morphology and function still remain poorly known in most species, despite first being described more than a century ago. This paper describes the morphology of the IBP in Camponotus japonicus using light and electron microscopy. The IBP occurs in workers, queens and males,...
Presentation
I talked about the potential of anatomical characters to help us understand the evolution of ants and showed some character systems that have been neglected previously. I tried to make clear why it might be insightful to take a closer look at these character systems.
Article
Magnetically removable plasmonic nanoparticles are of great interest for biomedical and catalytical applications. A novel and straightforward method to prepare a core-shell structure consisting of a superparamagnetic Fe 3 O 4 core coated with a plasmonic gold shell is described. The synthesis combines ease of functionalization, limited supervision...
Article
This paper describes the morphology and ultrastructure of the infrabuccal pocket in workers of the carnivorous ant Ectomomyrmex javanus, using SEM and TEM. The infrabuccal pocket is a flexible bag with a diameter of 330 ± 30 μm. In its anterior part, the pocket wall reaches a thickness of 24.45 ± 3.45 μm, which is thicker than the wall lining the r...
Article
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Background While thousands of ant species are arboreal, very few are able to tunnel through living wood. Ants of the genus Melissotarsus (subfamily Myrmicinae) inhabit tunnel systems excavated under the bark of living trees, where they keep large numbers of symbiotic armoured scale insects (family Diaspididae). Chewing through healthy wood requires...
Article
Cuticle quality is of vital importance in insects. It prevents desiccation, provides mechanical strength and protects against pathogens. The within-species variation of cuticular structure is affected by many factors. We investigated the relationship of the presence/absence of the ectoparasitic fungus Rickia wasmannii and cuticle thickness of its a...
Article
Besides the common labial and metapleural glands, four novel exocrine glands are described in the thorax of both workers and queens of the ponerine ant Myopias hollandi. From anterior to posterior, these glands were designated as the propleural pit gland, the posterolateral pronotal gland, the anterolateral propodeal gland and the metasternal proce...
Article
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Wax production is one of the stingless bee activities that is related with nest building. We studied wax gland size in workers of the stingless bee Friesella schrottkyi at nine different ages: 0, 4, 5, 8, 10, 13, 14, 15, and 20 days. In the large majority of workers, we observed a conspicuous epithelium in abdominal tergites III, IV, and V. Our res...
Article
Normal gut function is vital for animal survival, and deviations from such function can contribute to malnutrition, inflammation, increased susceptibility to pathogens, diabetes, neurodegenerative diseases, and cancer. In the fruit fly Drosophila melanogaster, mutation of the gene drop-dead (drd) results in defective gut function, as measured by en...
Article
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 secon...
Article
The 'samsum ant' Brachyponera sennaarensis is an invasive species in Saudi Arabia, where it forms a serious threat because of its painful sting. As part of a morphological survey of the exocrine system of this species, we studied the mandibular gland of males, queens and workers of this species. The gland of males is similar to the common anatomica...
Article
The Dufour's and venom glands are two important exocrine glands in ants. In this study, the morphology and fine structure of these two glands are described in the ant Camponotus japonicus Mayr. The Dufour glands have a characteristic bilobed shape and show a difference in size and color between the female castes (minor and major workers, alate and...
Presentation
Full-text available
Among thousand species of arboreal ants, relatively few build their nests inside living wood. Melissotarsus is an Afrotropical ant that dig galleries under the bark of living trees, where they keep scale insects as symbionts. Chewing through healthy wood requires tremendous power, intuitively unexpected in 2.5mm-long individuals. Using histology, s...
Article
Reflex bleeding is an effective defensive mechanism against predators. When attacked, some insects emit hemolymph, which coagulates, quickly entangling their aggressor. Bleeding occurs at weak intersegmental membranes or through dedicated organs which can be associated or not with glandular cells. Here, we describe the behavior and morphological st...
Article
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Background: Reproductive division of labor is one of the key features of social insects. Queens are adapted for reproduction while workers are adapted for foraging and colony maintenance. In many species, however, workers retain functional ovaries and can lay unfertilized male eggs or trophic eggs. Here we report for the first time on the occurrenc...
Article
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The Dufour gland of two Myzinum females was studied with light and electron microscopy, and is formed by a large sac lined with a monolayered secretory epithelium. The epithelium displays a crenellate appearance, which is the result of the peculiar shape of the secretory cells, that have a cupola-like central portion and a more flattened appearance...
Article
We studied the internal and external appearance of the metapleural gland in the five castes of Technomyrmex vitiensis. All castes do possess the gland, but with a clear gradient from queens (most developed gland), via intercastes, workers and wingless males to winged males (least developed). Also the size and the shape of the atrium differ among ca...
Article
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Three ant species nest obligately in the swollen-thorn domatia of the African ant-plant Vachellia (Acacia) drepanolobium, a model system for the study of ant-defence mutualisms and species coexistence. Here we report on the charac- teristic fungal communities generated by these ant species in their domatia. First, we describe behavioural difference...
Article
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The climbing abilities of two bed bug species, Cimex lectularius L. and Cimex hemipterus (F.), were determined by evaluating their escape rates from smooth surface pitfall traps using four commercial bed bug monitors (Verifi Bed Bug Detector, ClimbUp Insect Interceptor, BlackOut Bed Bug Detector, and SenSci Volcano Bed Bug Detector). All detectors...
Article
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The great evolutionary success of insects is partly linked to the innovation of the cuticle, which underlies a complex exoskeleton with varied functions. Cuticle development is costly since chitin and cuticular proteins require ingested nitrogen. Studying cuticle thickness on a comparative basis allows an insight in the trade-off between offspring...
Article
The role of queens in caste regulation of pharaoh ant colonies has been puzzling biologists for decades. Worker-fertility-inhibiting pheromones are lacking, as workers of this polygynous species are completely sterile. Yet, fertile queens possess inhibiting powers over the production of new gynes and males. Here we test whether queen-produced cutic...
Article
Full-text available
Purpose Homeostatic turnover of the trabecular meshwork extracellular matrix (ECM) is essential to regulate aqueous humor outflow and to maintain intraocular pressure homeostasis. In this study, we evaluated aqueous humor turnover, intraocular pressure, and trabecular meshwork organization in MMP-9 null mice. Methods Intraocular pressure and aqueo...
Article
Charidotella ambita offers a unique opportunity for unambiguously locating its gold reflector by comparing the structure of reflecting and non-reflecting cuticle of the elytron and pronotum. Using light microscopy and TEM, the reflector was located underneath the macrofiber endocuticle just above the epidermis. The reflector is a multilayer compris...
Article
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Among the many associations between fungi and ants, the associations involving the ectoparasitic fungi Laboulbeniales (Ascomycota: Laboulbeniales) have remained largely enigmatic even today. However, for two of the six ant-parasitizing Laboulbeniales, it has been found that parasitism is correlated with diminished survival of their hosts, especiall...
Article
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We studied the external and internal pretarsus structure of the ants Brachyponera sennaarensis (Mayr, 1862) and Daceton armigerum (Latreille, 1802) in relation to their very different climbing ability. B. sennaarensis is a ground-dwelling species that is not able to climb vertical smooth walls. They have a pair of straight pretarsal claws with an a...
Article
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 inv...
Article
The maxillary and propharyngeal gland of all 3 castes of Monomorium pharaonis were examined with light and electron microscopy. Although both glands possess a pouch in which secretion can be stored temporarily, a proper reservoir is lacking. The paired maxillary gland opens at the base of the maxilla and consists of 4 secretory cells, which are sma...
Article
The mandibular gland in workers of the formicine ant Myrmoteras iriodum differs from other ants both in its general morphology and ultrastructural organization. The secretory cells appear in a pseudo-epithelial arrangement that gives them a clear polarity. At their apical side, the cells are characterized by a large cup-like extension of the reserv...
Article
Reproductive division of labor is one of the crucial features in social insects, however, the developmental mechanisms leading to modifications in the reproductive apparatus of workers are still not very clear. Ants show a remarkable diversity in the morphological specialization of the worker's reproductive apparatus, that allows to distinguish fou...
Article
Workers of Aneuretus simoni have a well-developed Pavan's gland, which is the exocrine character that makes the Aneuretinae and Dolichoderinae sister groups. The secretory epithelium of the gland consists in both minor and major workers of an anterior and a posterior part, which makes them different from the Dolichoderinae where the gland is formed...
Article
Aneuretus simoni workers have a conspicuous intramandibular gland, formed by round to polygonal class-3 secretory cells with a diameter around 16-17 μm and their accompanying duct cells. Both in minor and major workers, approx. 8 cells open through the proximal upper surface of the mandible, approx. 12 cells open through the proximal lower surface....
Article
The defensive function of petiole spines in queens and workers of the formicine ant Polyrhachis lamellidens was investigated using the ant predating tree frog Hyla japonica. Ant workers have hook-like large spines on their petiole while the queen petiole has only small slightly curved spines. Intact workers of P. lamellidens are unpalatable while w...