Diversity and morphology of abdominal glands in workers of the ant genus Myopias (Formicidae,Ponerinae)

Histological examination of serial sections through the abdomen of workers of three species of Myopias ants revealed the presence of several exocrine glands. These include the common venom and Dufour glands as well as the pygidial gland, but also more specific sternal glands and glands associated with the sting base and the gonostyli. Two of these glands have not been reported previously among ants: one is the paired oblong plate gland, that occurs next to the oblong plate and may have a pheromonal function. The other novel gland is the paired sting shaft gland, that occurs at the dorsal side in the proximal region of the sting shaft. A remarkable characteristic of these Myopias ants is that all glands of class-3 show ducts with gradually widening internal diameter. Myopias emeryi shows a clearly more simple variety of abdominal glands than Myopias maligna and M. sp.1.     

Morphology and ultrastructure of the dufour's and venom gland in the ant,Myrmica rubra (L.) (Hymenoptera : Formicidae)

The morphology and fine structure of the Dufour's and venom gland, as well as their entrance into the sting, are described in the myrmicine ant, Myrmica rubra (Hymenoptera : Formicidae). The epithelial cells that constitute the Dufour's gland wall, contain a well-developed smooth endoplasmic reticulum. Older workers, compared with younger ones, show an increasing number of multilamellar inclusions. The venom gland secretory cells are arranged in 2 free filaments that carry the secretion to the reservoir. Their cytoplasm shows an intracellular collecting ductule with surrounding microvillar sheath, and an abundance of free ribosomes. However, a well-organized granular endoplasmic reticulum, which is typical in species with a more powerful sting, does not occur. Both the Dufour's and venom gland ducts are characterized by the insertion of extensive muscle fibres, which act as a precise and mutually independent control mechanism for the discharging activities of the 2 glands.     

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.     

Distribution and comparative morphology of the cloacal gland in ants (Hymenoptera : Formicidae)

The cloacal gland is a paired exocrine structure, which has so far been described only in the formicine species, Camponotus ephippium and Cataglyphis savignyi (Hymenoptera : Formicidae). The gland is formed by 2 clusters of bicellular units with slender duct cells, releasing the glandular secretion through the cloacal membrane. In the present work, a number of ant species, largely of the Formicinae subfamily, have been surveyed for the presence of a cloacal gland. The gland is present in nearly all formicines screened, albeit with a variable development. Cataglyphis, one of the genera with a very prominent cloacal gland, was chosen for a more detailed comparative study. At the ultrastructural level, secretory cells were observed having a well-developed smooth endoplasmic reticulum and Golgi apparatus, typical for pheromone-producing glandular cells. The gland is also present in all dolichoderines screened, but in none of the species of the Aneuretinae, Myrmeciinae, Myrmicinae, Nothomyrmeciinae, or Pseudomyrmecinae investigated. This provides tentative evidence that the cloacal gland is a synapomorphy of the Formicinae and Dolichoderinae, giving support for their hypothesized sister group relationship. Up to now, the function of the cloacal gland remains largely enigmatic.     

Foraging Area Marking in Two Related Tetramorium Ant Species (Hymenoptera: Formicidae)

The related ants Tetramorium caespitum and T. impurum mark their foraging area in a species-specific, home range and short-lasting manner. Indeed, ants reaching a new area have a slow linear speed which increases during the marking. Conspecific ants are arrested and attracted by marked areas, while heterospecific ants are reluctant to visit them. However, when the latter do visit marked areas, they move more quickly and less sinuously than conspecific ants and do not stay on the areas. The marking is performed in about 3 min by T. caespitum and in 3 to 6 min by T. impurum. If not reinforced, the marking vanishes in the same time intervals. Neither poison gland nor last sternite extracts reproduce the activity of naturally marked areas, whereas a Dufour gland extract does exactly that. Foraging ants touch the ground with the tip of their gaster. Consequently, we can postulate that the workers mark their foraging area with the contents of this gland, which is associated with the sting apparatus, and that they deposit with the extremity of the gaster. Alien conspecific ants are seldom aggressive to one another, even on marked areas. When encountering each other on unmarked areas, heterospecific ants present some aggressive reactions. On marked areas, their aggressiveness is enhanced and intruder ants are restless, while resident ones walk freely. On ground marked by T. impurum, ants of this species are more aggressive than antagonistic T. caespitum workers. The marking of foraging areas thus induces defense against heterospecifics but not against conspecific ants.     

Worker size polymorphism and ethological role of sting associated glands in the harvester ant Messor barbarus

Summary: Though harvester ants are closely similar in ecology, species differ in their worker size polymorphism as well as in the glandular source of their trail pheromones and defensive compounds. In the harvester ant Messor barbarus, we find that the recruitment trail pheromone is located in the Dufour gland, while defence-alarm substances are produced in the poison gland. We also investigated how the glandular development and the ethological response to these abdominal glands are related to worker body size. For both glands, M. barbarus workers show monophasic and nonisometric growths with slopes of allometric regression lines lower than 1. The highest trail-following response is elicited by the Dufour gland secretion from media workers, responsible for most foraging activities in M. barbarus. Aggressive behaviour is more frequently observed in the presence of poison gland secretions from medium and large-sized workers. Differences between species and between worker size classes in the ethological role of sting associated glands are discussed in relation to the foraging ecology and defensive characteristics of harvester ants.     

The nasus gland: A new gland in soldiers of Angularitermes (Termitidae,Nasutitermitinae)

Termites have developed many exocrine glands, generally dedicated to defence or communication. Although a few of these glands occur in all termite species, or represent synapomorphies of larger clades, others are morphological innovations of a single species, or a few related species. Here, we describe the nasus gland, a new gland occurring at the base of the nasus of Angularitermes soldiers. The nasus gland is composed of class 1, 2, and 3 secretory cells, a rare combination that is only shared by the sternal and tergal glands of some termites and cockroaches. The ultrastructural observations suggest that the secretion is produced by class 2 and 3 secretory cells, and released mostly by class 3 cells. The base of the nasus has a rough appearance due to numerous pits bearing openings of canals conducting the secretion from class 3 secretory cells to the exterior. We tentatively assign a defensive function to the nasus gland, although further research is needed to confirm this function. Although the gland is described only from species of Angularitermes, other genera of Nasutitermitinae also present a rough nasus base, suggesting the presence of a similar, possibly homologous, gland.     

An integumentary gland secreting a territorial marking pheromone in Atta sp.: Detailed structure and histochemistry

An abdominal pheromone-producing gland in Atta sp. was examined using light and electron microscopy techniques. The gland is composed of a bunch of juxtaposed secretory units in which the secretory ductules open on to a cribellum close to the sting base.The structure and cycles of the secreting units are described. Each includes a secretory cell with an ‘end apparatus’, ductule cells and epidermal cells. The secretory cycle of glycoproteins accumulated in the ‘end apparatus’ is discussed and a functional interpretation of the morphological components of the application system is proposed.     

Pygidial gland chemistry and potential alarm-recruitment function in column foraging,but not solitary,Nearctic Messor harvesting ants (Hymenoptera: Formicidae: Myrmicinae)

We investigated the role of the pygidial gland on foraging behavior in two ecologically dominant column foraging Nearctic harvesting ants (Messor pergandei and Messor andrei). Using chemical analyses and behavioral tests, we show that n-tridecane is the major biologically active compound of pygidial gland secretions in both species, and that this chemical functions as a powerful alarm-recruitment pheromone. Another major compound of pygidial gland contents is benzaldehyde; this substance does not release behavioral reactions in M. pergandei workers but might function as a defensive secretion. Six solitary foraging Nearctic Messor and two column foraging Palearctic Messor species, did not have large pygidial gland reservoirs.     

Identification of factors that function in Drosophila salivary gland cell death during development using proteomics

Proteasome inhibitors induce cell death and are used in cancer therapy, but little is known about the relationship between proteasome impairment and cell death under normal physiological conditions. Here, we investigate the relationship between proteasome function and larval salivary gland cell death during development in Drosophila. Drosophila larval salivary gland cells undergo synchronized programmed cell death requiring both caspases and autophagy (Atg) genes during development. Here, we show that ubiquitin proteasome system (UPS) function is reduced during normal salivary gland cell death, and that ectopic proteasome impairment in salivary gland cells leads to early DNA fragmentation and salivary gland condensation in vivo. Shotgun proteomic analyses of purified dying salivary glands identified the UPS as the top category of proteins enriched, suggesting a possible compensatory induction of these factors to maintain proteolysis during cell death. We compared the proteome following ectopic proteasome impairment to the proteome during developmental cell death in salivary gland cells. Proteins that were enriched in both populations of cells were screened for their function in salivary gland degradation using RNAi knockdown. We identified several factors, including trol, a novel gene CG11880, and the cop9 signalsome component cop9 signalsome 6, as required for Drosophila larval salivary gland degradation.     

Chemical constituents of Dufour's gland in the ant, Myrmica rubra

The volatile constituents of the Dufour gland in Myrmica rubra have been examined by gas chromatography-mass spectrometry. The principal constituents are 8-heptadecene, n-pentadecane, n-heptadecane, and 9-nona-dencene. The other constituents comprise mainly other alkanes, alkenes, and a few sesquiterpenes. The sting gland does not contain volatile materials.     

Structure, chemical composition and putative function of the postpharyngeal gland of the emerald cockroach wasp, Ampulex compressa (Hymenoptera, Ampulicidae)

The postpharyngeal gland (PPG) plays a major role in the social integration of ant colonies. It had been thought to be restricted to ants but was recently also described for a solitary wasp, the European beewolf (Philanthus triangulum). This finding posed the question whether the gland has evolved independently in the two taxa or has been inherited from a common ancestor and is hence homologous. The latter alternative would be supported if a PPG was found in more basal taxa. Therefore, we examined a species at the base of the Apoidea, the solitary ampulicid wasp Ampulex compressa, for the existence of a PPG. Both sexes of this species possess a cephalic gland that branches off the posterior part of the pharynx, is lined by a cuticular intima and surrounded by a monolayered epithelium with the epithelial cells bearing long hairs. Most of these morphological characteristics conform to those of the PPG of ants and beewolves. Chemical analysis of the gland content revealed that it contains mainly hydrocarbons and that there is a congruence of the pattern of hydrocarbons in the gland, on the cuticle, and in the hemolymph, as has also been reported for both ants and beewolves. Based on these morphological and chemical results we propose that the newly described cephalic gland is a PPG and discuss its possible function in A. compressa. The present study supports the view of a homologous origin of the PPG in the aculeate Hymenoptera.     

Functional role of phenylacetic acid from metapleural gland secretions in controlling fungal pathogens in evolutionarily derived leaf-cutting ants

Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors'' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants'' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens.     

An integumentary pheromone-secreting gland in Atta sp: Territorial marking with a colonyspecific pheromone in Atta cephalotes

Workers of Atta cephalotes mark the area around their nest with a pheromone that has at least two components, one of which is colony-specific. Another, which was isolated and tested for its activity, is genus- or species-specific in its action; it appears to be similar in A. sexdens and A. cephalotes, but differs in Acromyrmex octospinosus. The pheromone is produced in a newly described gland, located near the sting. A synthetic trail pheromone component in very low concentrations stimulates some behavioural effects similar to those of the territorial pheromone.     

The pretarsal footprint gland of the ant Amblyopone reclinata (Hymenoptera,Formicidae) and its role in nestmate recruitment

Workers of the ant Amblyopone reclinata employ solitary prey retrieval when prey is small, but recruit nestmates to large prey. In the latter case, the scout forager paralyses the prey with its powerful sting, and quickly returns to the nest. During this homeward journey, it deposits a trail pheromone, that originates from the well developed footprint glands in its hindlegs. Recruited workers follow this trail to reach the prey, which is then jointly dragged to the nest. The footprint gland is only found in ants of the genus Amblyopone, and is formed by a glandular differentiation of the dorsal tegumental epidermis in the hindleg pretarsi. The secretory epithelium is approximately 15–20 μm thick, and shows apical microvilli and basal invaginations. The cytoplasm contains numerous mitochondria. Narrow pores with a diameter of 0.1 μm run through the cuticle, although they were not seen to open at the pretarsus external surface. Careful observation of trail-laying workers reveals that during trail-laying the hindleg pretarsus is twisted in a peculiar position, which explains how secretion from the dorsally located footprint gland is deposited onto the substrate.     

Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.)

Eelen D., Børgesen L.W. and Billen J. 2006. Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.). —Acta Zoologica (Stockholm) 87 : 101–111 The postpharyngeal gland (PPG) is unique to ants and is the largest exocrine gland in their head. In queens of the pharaoh's ant, Monomorium pharaonis, the gland contains approximately 15 finger‐like epithelial extensions on each side and opens dorsolaterally in the posterior pharynx. In these ants the PPG morphology varies considerably according to age and mating status. The epithelial thickness increases with age and reaches a maximum at 3 weeks in both virgin and mated queens. A considerable expansion of the lumen diameter occurs in both groups between 4 and 7 days. Virgin queens release their secretion into the gland lumen from an age of 7 days, whereas mated queens accumulate large amounts of secretion in their epithelium. The increasing epithelial thickness, together with the increasing lumen diameter, the presence of numerous inclusions in the epithelium and the release of secretion, are indicative for increasing gland activity. The gland ultrastructure indicates involvement in lipid metabolism and de novo synthesis of lipids. The PPG of workers consists of 12 finger‐like tubes at each side. There is a significant difference in epithelial thickness between nurses and repletes and between nurses and foragers. We suggest the PPG serves different purposes in pharaoh's ants: it is likely that the PPG of workers and virgin queens is used to feed larvae. In mated queens the gland probably plays a role in providing the queen with nutritious oils for egg production. The PPG may also function in signalling species nestmate and caste identity, as well as in the reproductive capacity of the queens.     

Survey of the exocrine system in Protanilla wallacei (Hymenoptera,Formicidae)

We studied the exocrine system of both workers and ergatoid queens of Protanilla wallacei using light, scanning and transmission electron microscopy. Our survey revealed the presence of 26 glands, of which 6 had never been found before in ants. Five of these represent novel discoveries for social insects in general. The overall novel discoveries comprise an epithelial stipes gland, a pharyngeal wall gland, a central petiole gland, a lateral postpetiole gland and a foot-sole gland in the hindleg pretarsi. The intramandibular epithelial gland was already reported in some bees previously, but is now for the first time also reported in ants. The exocrine system of workers and ergatoid queens is very similar, with only the spermathecal gland showing an obvious difference. This is in line with the limited anatomical as well as behavioural difference between both castes in Protanilla compared to the situation in Leptanilla.     

Dufour's gland secretion as a repellent used during usurpation by the slave-maker ant Rossomyrmex minuchae

In slave-making ants, the invasion of the host colony by newly mated queens is a critical stage. We studied the strategy used by Rossomyrmex minuchae queens to invade their host Proformica longiseta. Field observations revealed that queens enter the host nest unchallenged by the host workers in the vicinity of the nest entrance. Pre-usurpation queens were found to possess a highly inflated Dufour's gland, which considerably reduces in size after successful usurpation. Chemical analysis of these queen glands revealed tetradecanal to be the major product in pre-usurpation Rossomyrmex queens, but to be almost absent in queens that have been adopted by P. longiseta. We consequently hypothesized that tetradecanal is a repellent that is used by queens to prevent host worker aggression. We tested its repellent effect by attempting to deter starved, highly motivated workers from a droplet of honey. Tetradecanal indeed proved to be highly repellent both to host worker P. longiseta and non-host worker Formica selysi. It was even more powerful than limonene, a reported general ant repellent. These results are consistent with the hypothesis that R. minuchae queens use Dufour's gland secretion as a weapon during nest usurpation. The general use of tetradecanal as a defensive compound, and its seemingly non-specific repellent effect on ants, indicate that it may act as a general ant repellent. Its adoption by R. minuchae queens thus provides them with an efficient defensive and offensive chemical weapon during their long and risky search for new host nests.     

Rubbing behavior and morphology of van der Vecht's gland inBelonogaster petiolata (Hymenoptera: Vespidae)

Females of the social wasp, Belonogaster petiolata,rub the secretion of van der Vecht's gland, located on their terminal gastral sternite, onto the nest pedicel. In bioassays, the secretion was repellent to two species of ants, while shortchain acids were effective releasers of rubbing behavior. Rubbing was associated with pedicel enlargement and departure from the nest in preemergence colonies. Its frequency was high where wasps were often exposed to ants and low where ants were rare or absent. Rubbing also decreased significantly from the pre-to the postemergence stage of the colony cycle. In both stages, subordinate foundresses rubbed more often than queens or workers. These observations support the hypothesis that rubbing behavior and the secretion of van der Vecht's gland function in chemical defense of the nest against ant predation. The general morphology of the gland in B. petiolataresembles that of the four other independent-founding polistine wasp genera.     

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.