Structure and chemistry of the Dufour gland in Pristomyrmex ants (Hymenoptera, Formicidae)

Billen, J., Ito, F., Tsuji, K., Schoeters, E., Maile, R. and Morgan, E. D. 2000. Structure and chemistry of the Dufour gland in Pristomyrmex ants (Hymenoptera, Formicidae). —Acta Zoologica (Stockholm) 81 : 159–166 All individuals of the three species of Pristomyrmex studied have a Dufour gland with a conspicuous hammer‐shaped distal part, that is connected to a thin‐walled proximal reservoir through a very narrow stalk. The secretory distal part is formed by high columnar cells that are characterized by a highly folded apical wall. The lateral cell junctions apically correspond with the crenel tops, which gives individual cells a peculiar shape with a deep apical depression. The cytoplasm of the secretory cells contains a very well developed smooth endoplasmic reticulum and Golgi apparatus, numerous mitochondria and lysosomes. Histochemical analysis indicates a positive reaction for the presence of a lipid secretion in the hammer‐like part. Gas chromatographic analysis of glands of P. pungens workers reveals the secretion to be formed of a mixture of simple volatile monoterpene hydrocarbons; α–pinene, β–pinene, limonene and camphene. Similar, but species characteristic mixtures of four monoterpenes were found in Pristomyrmex brevispinosus and Pristomyrmex sp.1. Behavioural experiments did not allow a conclusive determination of the function of the gland.     

An evaluation of the possible adaptive function of fungal brood covering by Attine ants

Fungus-growing ants (Myrmicinae: Attini) live in an obligate symbiotic relationship with a fungus that they rear for food, but they can also use the fungal mycelium to cover their brood. We surveyed colonies from 20 species of fungus-growing ants and show that brood-covering behavior occurs in most species, but to varying degrees, and appears to have evolved shortly after the origin of fungus farming, but was partly or entirely abandoned in some genera. To understand the evolution of the trait we used quantitative phylogenetic analyses to test whether brood-covering behavior covaries among attine ant clades and with two hygienic traits that reduce risk of disease: mycelial brood cover did not correlate with mutualistic bacteria that the ants culture on their cuticles for their antibiotics, but there was a negative relationship between metapleural gland grooming and mycelial cover. A broader comparative survey showed that the pupae of many ant species have protective cocoons but that those in the subfamily Myrmicinae do not. We therefore evaluated the previously proposed hypothesis that mycelial covering of attine ant brood evolved to provide cocoon-like protection for the brood.     

Change of Dufour gland contents with age of workers of Formica sanguinea (Hymenoptera: Formicidae)

ABSTRACT The Dufour glands of newly emerged adult workers of F.sanguinea Latr. are almost empty, but the gland fills slowly over several months. The amount and composition of the secretion varies between individuals but the mean values change with age, the composition reaching its final value only in old foraging workers. Undecane is the major component for most of the period, but its proportion decreases with age. The amount of (Z,E)-α-farnesene increases with age and finally becomes the major component. The change in composition may reflect changes in worker function.     

The metapleural gland of ants

The metapleural gland (MG) is a complex glandular structure unique to ants, suggesting a critical role in their origin and ecological success. We synthesize the current understanding of the adaptive function, morphology, evolutionary history, and chemical properties of the MG. Two functions of the MG, sanitation and chemical defence, have received the strongest empirical support; two additional possible functions, recognition odour and territorial marking, are less well supported. The design of the MG is unusual for insects; glandular secretions are stored in a rigid, non‐compressible invagination of the integument and the secretion is thought to ooze out passively through the non‐closable opening of the MG or is groomed off by the legs and applied to target surfaces. MG loss has occurred repeatedly among the ants, particularly in the subfamilies Formicinae and Myrmicinae, and the MG is more commonly absent in males than in workers. MG chemistry has been characterized mostly in derived ant lineages with unique biologies (e.g. leafcutter ants, fire ants), currently precluding any inferences about MG chemistry at the origin of the ants. A synthetic approach integrating functional morphology, phylogenetic transitions and chemical ecology of the MGs of both the derived and the unstudied early‐branching (basal) ant lineages is needed to elucidate the evolutionary origin and diversification of the MG of ants.     

蚂蚁的化学通讯

化学通讯是蚂蚁的主要通讯方式,简要介绍了6种主要的外分泌腺体及其所分泌的化学信息物质(信息素)的通讯功能。     

Unusual structural and chemical characteristics of the Dufour gland in the ant Meranoplus diversus

Abstract The Dufour gland of both queens and workers of Meranoplus diversus is very large. The reservoir is lined with flat epithelial cells, which usually contain smooth endoplasmic reticulum but also show the unusual accumulation of electron‐dense inclusions. Chemically, the gland contains an unusual mixture of long‐chain fatty acids and their derivatives, including hydrocarbons, ketones and amines with long‐chain substituents, hydroquinone, and sugars. Some of the substances identified are already known as insect defensive compounds against other arthropods.     

Dufour gland secretion of Polistes wasp: Chemical composition and possible involvement in nestmate recognition (Hymenoptera: vespidae)

The Dufour gland secretion and cuticle lipids of foundresses of Polistes dominulus have been chemically analysed. The gland secretion (analysed for the first time in a polistine species) contains a complex mixture of hydrocarbons, which are the same as those found on the cuticle. The cuticular hydrocarbon mixture and gland secretion differ, however, in the proportions of components: in the first, linear hydrocarbons are more abundant, while in the second we found a higher quantity of dimethylalkanes. Multivariate statistical analysis has shown that foundresses belonging to different colonies are distinguished on the basis of both the composition of their Dufour gland secretion and cuticular hydrocarbon mixture. Branched hydrocarbons seem to be particularly important in distinguishing females according to their colony. We suggest that the Dufour gland may contribute substances to form the hydrocarbon layer on the cuticle.     

Novel mandibular gland volatiles from Apterostigma ants

The fungus-farming ants are a well-studied evolutionary radiation within the subfamily Myrmicinae that associate with a web of symbionts that span kingdoms. Members of the Apterostigma pilosum species group cultivate unique basidiomycete fungi belonging to the coral-mushroom family Pterulaceae, a family of fungi that is distantly related to the Agaricaceae (Leucoagaricus and Leucocoprinus) fungi grown by most fungus-farmers including other members in the genus Apterostigma (A. auriculatum group and A. megacephala). A chemical analysis using gas chromatography–mass spectroscopy of the mandibular gland volatiles of two species – A. dentigerum and A. manni – revealed the presence of an extraordinary diversity of natural products. Many of these compounds are new to Arthropoda, such as a homologous series of 3-methyl-2-alkanones, 2-methyl-2-alkenals, and 1-phenyl-2-propanone in A. dentigerum and 1-phenyl-2-propanol in A. manni. These results identify a remarkable divergence of compounds across the fungus-growing ants and other members in Myrmicinae. Functions of these natural products are proposed and discussed.     

On the similarity of the Dufour gland secretion and the cuticular hydrocarbons of some bumblebees

Abstract. There is a close correspondence in composition between the hydrocarbons of the Dufour gland and the cuticular hydrocarbons of workers of some bumblebee species. This correspondence is characteristic of the species, and independent of the place and time of collection.     

Fine structure of the postpygidial gland in Aenictus army ants

Billen, J., Gobin, B. & Ito, F. 1999. Fine structure of the postpygidial gland in Aenictus army ants. – Acta Zoologica (Stockholm) 80: 307–310
Army ants of the genus Aenictus are characterized by the presence of a conspicuous postpygidial gland, which is the source of the trail pheromone. The paired gland at each side consists of a reservoir sac into which the secretory cells open through their accompanying duct cells. The secretory cells are characterized by a well developed Golgi apparatus, numerous mitochondria and strands of smooth endoplasmic reticulum. The reservoir opens near the abdomen tip, which facilitates deposition of the secretory products onto the substrate. The large reservoir of the postpygidial gland may enable the incessant trail laying of at least one of the investigated species.     

The crenellate lining of the Dufour gland in the genus Aenictus: a new character for interpreting the phylogeny of Old World army ants (Hymenoptera, Formicidae, Dorylinae)

The Dufour gland epithelium in Aenictus has a crenellate appearance, a condition previously found only in the primarily African genus Dorylus . This character, taken alone, strongly suggests that these two genera share a common ancestry, as is presently reflected in their placement in the subfamily Dorylinae, and that an independent, convergent origin for them, as has been proposed in the triphyletic hypothesis for army ant evolution, is incorrect.     

Identification of mellein in the mandibular gland secretions of carpenter ants

The mandibular gland secretions of males of the ants $\text{Camponotus herculeanus, C. ligniperda}$, and $\text{C. pennsylvanicus}$ contain three major volatile substances. These compounds have been identified as 3,4-dihydro-8-hydroxy-3-methylisocoumarin (mellein or ochracin), methyl 6-methylsalicylate, and 10-methyldodecanoic acid. Mellein has not been isolated previously from animal sources.     

膜翅目昆虫杜氏腺形态结构、内分泌物与功能的研究进展

杜氏腺为膜翅目雌性昆虫生殖器官中的一外分泌腺体,外形呈囊腔状,内含丰富的油状分泌物。其内分泌物主要为饱和与不饱和烃类化合物,有着辅助产卵、释放信息素及作幼虫食物等多方面的功能。本文对杜氏腺的形态结构、内分泌物合成途径、化学组分及其生理和生态学功能进行了综述。     

The subepithelial gland in ants: a novel exocrine gland closely associated with the cuticle surface

Two glandular systems were discovered that secrete their products onto the cuticular surface in ants. The first, the subepithelial gland, was previously undescribed in ants, and is found throughout the body just beneath the epithelium. This gland consists of independent secretory units, each made up of a single gland cell and an associated duct cell that penetrates the cuticle. Its ultrastructural appearance is consistent with possible hydrocarbon production. Examining 84 ant species, the subepithelial gland was found in eight subfamilies (out of 13), although not necessarily in all species. In a single ant species, Harpegnathos saltator, it was the epithelium itself that was enlarged and functioned as a gland. The enlarged epithelial cells secrete their products directly onto the cuticle through distinct cuticular crevasses.     

Dufour gland secretions of Myrmica rugulosa and Myrmica schencki workers

The chemical composition and behavioural activities of the secretions of the Dufour glands of Myrmica rugulosa and M. schencki have been studied, as part of an extended study on Myrmica ants. Chemically, the Dufour gland of M. rugulosa is filled with a mixture of hydrocarbons dominated by straight chain alkanes and alkenes with 13 to 19 carbon atoms, as found in M. rubra. Significant quantities of (Z,E)-α-farnesene and its homologues, homofarnesene and bishomofarnesene, are also present. In M. schencki, the major compounds present are homofarnesene and bishomofarnesene. In both species, the very volatile portion of the Dufour gland secretion is identical to that analysed in M. rubra. From an ethological point of view, this very volatile part is efficient in attracting workers at a distance (6 to 8 cm) and in decreasing their wandering movements. No specificity was observed when performing cross-tests with Dufour glands freshly isolated from workers of other Myrmica species, but obvious specificities were detected when testing the less volatile part of the Dufour glands' contents, known to be used for marking newly discovered areas.     

Morphology and ultrastructure of the Dufour gland in workers of social wasps (Hymenoptera, Vespidae)

The Dufour gland in workers of vespine wasps appears as an unpaired tubiform gland that opens in close proximity to the sting base. The epithelial cells that line the central reservoir are characterized by apical microvillus-like projections and deep basal invaginations. Their cytoplasm contains a well-developed Golgi apparatus, numerous mitochondria, as well as strands of smooth endoplasmic reticulum. The Dufour gland duct occurs ventrally to the venom gland duct, and bends downward near the sting base to open in the dorsal vaginal wall. In this region, the duct is dorsoventrally flattened, and shows conspicuous bundles of parallel microtubules in the epithelial cells, that transmit the pulling forces of the myofilaments of the underlying muscular supply to the cuticle. This results in an active opening mechanism regulated by muscular contraction, while passive closure probably results from the return of the cuticular intima to a rest position.     

Chemical congruence of the complex odoriferous secretions from Dufour's gland in three species of ants of the genus Formica

Forty-six volatile compounds were identified in the secretions from Dufour's gland of worker ants of the species Formica nigricans, F. rufa, and F. polyctena using combined gas chromatography-mass spectrometry and capillary gas chromatography. In both methods the natural volatile material has been driven off excised glands using a precolumn technique.The composition of the secretions from the three species are very similar but there are also some distinct differences, especially between F. nigricans on the one hand and F. rufa and F. polyctena on the other. Straight-chain, saturated hydrocarbons are the quantitatively dominating compounds, with undecane as the largest individual component, followed by tridecane, pentadecane, and heptadecane. Straight-chain, monounsaturated hydrocarbons and methyl-branched, saturated hydrocarbons are also present and a few straight-chain, doubly unsaturated hydrocarbons are present in trace amounts.In the region of lower volatility two isoprenoids identified as all-trans-geranylgeraniol and the corresponding acetate all-trans-geranylgeranyl acetate, have been found together with octadecyl acetate. The relative amounts between these compounds are the main difference between the secretions from the three species. Octadecyl acetate is thus present only in trace amounts in the secretion of F. nigricans.In addition to the compounds mentioned a few aliphatic acetates and alcohols present in small amounts have been identified.The secretions are thought to have many functions which are reflected in their complex composition. This is discussed in comparison with results from other formicine ants. The species specificity in the composition of the secretion from Dufour's gland and the taxonomic value of this specificity are also discussed.     

The Dufour gland closing apparatus in Formica sanguinea Latreille (Hymenoptera,Formicidae)

Summary A closing apparatus of the Dufour gland is described in the formicine ant Formica sanguinea Latreille 1798. Four sets of muscles are involved, two of which directly attach to the slit-like duct. The latter shows a considerable cuticular thickening of its intima at this level. Ultrastructural observations reveal that the muscles are attached to a cuticula by means of intracellular microtubules in the duct cells. These microtubules run parallel to the myofilaments. Together with the increased contact area for muscular attachments they are believed to ensure the accurate muscular mechanism assuring a well-controlled spraying activity of this gland. Opening of the duct is probably achieved by active muscular contractions, while its closure may be achieved by a passive return to the rest position of the thickened cuticular intima.Research assistant of the Belgian National Fund for Scientific Research     

Chemical warfare between fungus-growing ants and their pathogens

Fungus-growing attine ants are under constant threat from fungal pathogens such as the specialized mycoparasite Escovopsis, which uses combined physical and chemical attack strategies to prey on the fungal gardens of the ants. In defence, some species assemble protective microbiomes on their exoskeletons that contain antimicrobial-producing Actinobacteria. Underlying this network of mutualistic and antagonistic interactions are an array of chemical signals. Escovopsis weberi produces the shearinine terpene-indole alkaloids, which affect ant behaviour, diketopiperazines to combat defensive bacteria, and other small molecules that inhibit the fungal cultivar. Pseudonocardia and Streptomyces mutualist bacteria produce depsipeptide and polyene macrolide antifungals active against Escovopsis spp. The ant nest metabolome is further complicated by competition between defensive bacteria, which produce antibacterials active against even closely related species.     

Comparative study of the metatibial gland in ants (Hymenoptera,formicidae)

A novel glandular structure is described within the metatibia in ants of the poneroid group. This metatibial gland has been considered a major synapomorphic character of the subfamilies belonging to the doryline section. Histological investigations combined with scanning electron micrograph studies revealed a remarkably complex gland, consisting of a glandular epithelium and a cuticular pore plate, the morphology of which varies considerably between the species. This gland is also present in species of the generaDiacamma andPachycondyla (Ponerini). Based on the morphology of glandular epithelia and pore plates, it is not possible to decide whether this structure is homologous or analogous to that of the doryline section subfamilies. In workers of certain species of the genusDiacamma, the secretions of this gland are involved in sexual calling behavior.