Dufour Gland Contents Research Articles

Chemical Characterization of Young Virgin Queens and Mated Egg-Laying Queens in the Ant Cataglyphis cursor: Random Forest Classification Analysis for Multivariate Datasets.

Social insects are well known for their extremely rich chemical communication, yet their sex pheromones remain poorly studied. In the thermophilic and thelytokous ant, Cataglyphis cursor, we analyzed the cuticular hydrocarbon profiles and Dufour's gland contents of queens of different age and reproductive status (sexually immature gynes, sexually mature gynes, mated and egg-laying queens) and of workers. Random forest classification analyses showed that the four groups of individuals were well separated for both chemical sources, except mature gynes that clustered with queens for cuticular hydrocarbons and with immature gynes for Dufour's gland secretions. Analyses carried out with two groups of females only allowed identification of candidate chemicals for queen signal and for sexual attractant. In particular, gynes produced more undecane in the Dufour's gland. This chemical is both the sex pheromone and the alarm pheromone of the ant Formica lugubris. It may therefore act as sex pheromone in C. cursor, and/or be involved in the restoration of monogyny that occurs rapidly following colony fission. Indeed, new colonies often start with several gynes and all but one are rapidly culled by workers, and this process likely involves chemical signals between gynes and workers. These findings open novel opportunities for experimental studies of inclusive mate choice and queen choice in C. cursor.

Egg-laying behavior and morphological and chemical characterization of egg surface and egg attachment glue of the digger wasp Ampulex compressa (Hymenoptera, Ampulicidae)

For providing their offspring females of the digger wasp species Ampulex compressa hunt cockroaches, paralyze them and attach as a rule one egg to the coxa of one of the mid legs of their prey. We observed the egg-laying behavior and examined with light- and scanning microscopy (i) nearly mature eggs from ovaries of freshly dissected females and (ii) eggs immediately after their deposition on the coxae of their prey. The length of the white bean-shaped eggs varied between 2.2 and 3.0 mm, their diameter between 0.66 and 0.72 mm, and their weight between 345 and 832 μg. The surface of fresh, untreated eggs shows even at higher magnifications (>20.000×) a smooth appearance. However, after conventional fixation, dehydration with ethyl-alcohol and critical-point drying the egg-surface exhibited a little bit texture. The eggs are at two-third of their underside glued to the coxa of the prey. With the naked eye the glue appears as a compact mass. The eggs may be mechanically removed from the substrate (their attachment site); however, in doing so the viscous attachment glue appears in a more fibrous consistence. The polypeptide composition washed off the egg surface and the glue revealed no similarities, whereas the molecular mass of two polypeptides were similar between glue and the Dufour's gland contents.

Paralyzing action from a distance in an arboreal African ant species.

Due to their prowess in interspecific competition and ability to catch a wide range of arthropod prey (mostly termites with which they are engaged in an evolutionary arms race), ants are recognized as a good model for studying the chemicals involved in defensive and predatory behaviors. Ants' wide diversity of nesting habits and relationships with plants and prey types implies that these chemicals are also very diverse. Using the African myrmicine ant Crematogaster striatula as our focal species, we adopted a three-pronged research approach. We studied the aggressive and predatory behaviors of the ant workers, conducted bioassays on the effect of their Dufour gland contents on termites, and analyzed these contents. (1) The workers defend themselves or eliminate termites by orienting their abdominal tip toward the opponent, stinger protruded. The chemicals emitted, apparently volatile, trigger the recruitment of nestmates situated in the vicinity and act without the stinger having to come into direct contact with the opponent. Whereas alien ants competing with C. striatula for sugary food sources are repelled by this behavior and retreat further and further away, termites defend their nest whatever the danger. They face down C. striatula workers and end up by rolling onto their backs, their legs batting the air. (2) The bioassays showed that the toxicity of the Dufour gland contents acts in a time-dependent manner, leading to the irreversible paralysis, and, ultimately, death of the termites. (3) Gas chromatography-mass spectrometry analyses showed that the Dufour gland contains a mixture of mono- or polyunsaturated long-chain derivatives, bearing functional groups like oxo-alcohols or oxo-acetates. Electrospray ionization-mass spectrometry showed the presence of a molecule of 1584 Da that might be a large, acetylated alkaloid capable of splitting into smaller molecules that could be responsible for the final degree of venom toxicity.

Chemical communication in Ropalidia marginata: Dufour's gland contains queen signal that is perceived across colonies and does not contain colony signal

Queens of the primitively eusocial wasp Ropalidia marginata appear to maintain reproductive monopoly through pheromone rather than through physical aggression. Upon queen removal, one of the workers (potential queen, PQ) becomes extremely aggressive but drops her aggression immediately upon returning the queen. If the queen is not returned, the PQ gradually drops her aggression and becomes the next queen of the colony. In a previous study, the Dufour's gland was found to be at least one source of the queen pheromone. Queen-worker classification could be done with 100% accuracy in a discriminant analysis, using the compositions of their respective Dufour's glands. In a bioassay, the PQ dropped her aggression in response to the queen's Dufour's gland macerate, suggesting that the queen's Dufour's gland contents mimicked the queen herself. In the present study, we found that the PQ also dropped her aggression in response to the macerate of a foreign queen's Dufour's gland. This suggests that the queen signal is perceived across colonies. This also suggests that the Dufour's gland in R. marginata does not contain information about nestmateship, because queens are attacked when introduced into foreign colonies, and hence PQ is not expected to reduce her aggression in response to a foreign queen's signal. The latter conclusion is especially significant because the Dufour's gland chemicals are adequate to classify individuals correctly not only on the basis of fertility status (queen versus worker) but also according to their colony membership, using discriminant analysis. This leads to the additional conclusion (and precaution) that the ability to statistically discriminate organisms using their chemical profiles does not necessarily imply that the organisms themselves can make such discrimination.

Repellent effect on host Formica workers of queen Dufour's gland secretion of the obligatory social parasite ant, Polyergus samurai (Hymenoptera: Formicidae)

Founding queens of the obligatory social parasite ant Polyergus samurai usurp the host Formica japonica colony. The queen secretes chemicals from its gaster when killing the host queen. At this time, the parasite queen is hardly attacked by host workers. We hypothesized that the queen's secretion acts as a repellent to deter host workers' aggression during host queen killing. Gas chromatograph-mass spectrometry analyses confirmed that the chemical composition of Dufour's gland contents of P. samurai queens was almost identical to the chemicals remaining on the body surface of host Formica queens killed by them. Host F. japonica workers were used for bioassays. In an encounter with an intruder ant, the workers' aggression to the intruder was reduced significantly when Dufour's gland extract was applied to the intruder. Treatment of workers with the gland extract significantly increased the receding behavior of nestmates. The host workers receded from a glass dummy treated with the gland extract. The time necessary for a worker to get over a barricade applied with gland extract was significantly longer than that of controls. These results strongly suggest that Dufour's gland secretion acts as a repellent allomone.

Morpho-functional comparison of the Dufour gland in the female castes of the Amazon ant Polyergus rufescens (Hymenoptera, Formicidae)

The Dufour gland is crucially involved in main aspects of the parasite habit of the slave-making ant Polyergus rufescens, i.e. slave-raids and host colony usurpation. Workers use chemicals from this gland as recruitment signals during raid organization, while newly-mated queens use its secretion to appease residents during host nest invasion. Here, we report a comparison of the general morphology and fine structure of the Dufour gland in the female castes of P. rufescens: queens, ergatogynes (intermediate forms), and workers. The analysis clearly shows the link between gland structure and its behavioural role in queens and workers. In particular, queens present a hypertrophied gland with an extended lumen and a thin epithelium no more active in secretory function. This is consistent with the fact that usurper queens use the Dufour gland contents only during the short phase of host nest penetration. Contrary to adult queens, the cytoplasmic organization of the Dufour gland epithelium of raiders is typical for a tissue with secretory activity (abundance of mitochondria, free ribosomes, strands of smooth endoplasmic reticulum and a Golgi apparatus). This is consistent with the continuous raiding activity performed by workers throughout their adult life. The biology of ergatogynes is still an enigmatic matter. Their Dufour gland is intermediate in shape and size between that of queens and workers. It presents a fairly thick epithelium with features that are typical of a quite active secretory tissue.

Dufour gland secretion in the harvester ant genus Pogonomyrmex

Dufour gland secretions of the harvester ants Pogonomyrmex barbatus, P. rugosus and P. maricopa were investigated. The glandular blends exhibit species specific patterns, but more importantly, based on indiviual profiles of Dufour gland contents of colony members it is possible to separate the colonies from each other in each species. It is possible that these collective colony specific cues serve as longer lasting trunk route markers. Behavioral tests demonstrate that workers of P. rugosus prefer homing routes marked by members of their own colony to routes marked by a foreign conspecific colony.

Cuticular compounds of workers and queens in two Leptothorax ant species — a comparison of results obtained by solvent extraction, solid sampling, and SPME

We investigated cuticular hydrocarbons and fatty acids of workers and queens from two ant species, Leptothorax acervorum and L. gredleri. Cuticular compounds were extracted from single ants by solvent extraction, solid sampling, and solid phase microextraction (SPME) with two different polydimethylsiloxane (PDMS) fibers and analyzed using GC and GC-MS. All three methods gave similar results, documenting that SPME can be applied to very small, live ants (body size appr. 3 mm). The hydrocarbon mixtures consisted mostly of branched and unbranched alkanes and alkenes within the range of C25 to C33. Dufour glands of both species contained a blend of hydrocarbons different from those found on the cuticle. In addition, terpenoids, especially tetramorenes were present in the Dufour gland contents. In a principal components analysis based on the relative proportions of cuticular compounds, most nestmate workers clustered in four groups corresponding to the original four investigated colonies. Queens and workers differed significantly in their chemical profiles, suggesting that the two castes bear specific labels.

Dufour gland contents of ants of the Cataglyphis bicolor group.

The species of desert-dwelling ants of the Cataglyphis bicolor (Hymenoptera: Formicidae) group are difficult to distinguish by morphological features. Analysis of the secretion from the Dufour glands of workers of a number of colonies was undertaken to see if it provided a clear test of species. Linked 6c-ms showed in all samples straight and branched-chain alkanes, linear alkenes, ketones, aldehydes, acetates, and a group of C22 to C28 esters not previously identified in this genus. Contents of the Dufour glands of C. savignyi from Tunisia and Egypt were similar, and comprised straight and branched-chain alkanes, alkenes and small amounts of esters. C. bicolor from Tunisia contained compounds similar to C. savignyi but was distinguished from the latter by larger amounts of the esters. The major compound in the glands of C. viaticus was tridecane, in contrast to the pentadecane of other species. It also contained a branched alkane, 3-methyltridecane as a major component. Branched-chain esters and a wide variety of acetates were also found in this species. C. diehlii had a limited range of compounds, with branched alkanes almost completely absent and high proportions of pentadecene and dodecyl acetate. C bombycinus, a sympatric species. but recognized as not belonging to the bicolor group by its different mandibular gland substances, was notable in having butanoate esters in its Dufour glands. Despite these differences among species, both the great variability of individuals from a single colony and the among between conspecific colonies make species diagnosis from a few individuals difficult, in contrast with postpharyngeal glands, which, as recently reported, give a clearer indication of species.

Comparison of reproductive strategies and raiding behaviour in facultative and obligatory slave-making ants: the case of Formica sanguinea and Polyergus rufescens

A review of field and laboratory research concerning raiding behaviour, mating strategies and colony founding in Formica sanguinea and Polyergus rufescens (respectively facultative and obligatory parasites of the Serviformica species) is presented. The analysis and comparison of these crucial and peculiar moments in the life cycle of dulotic colonies may be a valid tool to clarify the evolutionary origins of slavery in ants.¶Concerning the reproductive behaviour, F. sanguinea females mate only in nuptial flights. P. rufescens females mate on the ground around their natal nest, or return to a dulotic colony after mating flights and wait for a raid, or mate directly during a raid. Moreover, field observations suggest that F. sanguinea adopts a strategy similar to the "male aggregation syndrome", whereas P. rufescens mating strategy can be considered similar to the "female calling syndrome". In the field, newly-mated queens of both slave-makers participate in raiding swarms: following a slave raid is an advantageous strategy to locate and invade host nests and to establish a new dulotic colony.¶For colony formation, F. sanguinea presents a great variety of possible strategies (independent foundation and dependent foundation including alliance, adoption, usurpation, and brood sack). This provides evidence of a behavioural plasticity that confirms its nature as a facultative parasite. On the contrary, P. rufescens depends only on usurpation, during which the Dufour's gland contents seem to play a crucial role in the appeasement of the residents of the target colony.¶Also the raiding behaviour of F. sanguinea is less specialized than that shown by P. rufescens. In fact, in the obligatory slave-maker the important role of scouts in the organization of slave-raids is confirmed, which are rapid and effective. By contrast, raids of F. sanguinea may be regarded as a continuation and expansion of common foraging and predatory activity, as predicted by Darwin's hypothesis for the origin and evolution of slavery in ants. Nevertheless, the intraspecific raids conducted by P. rufescens emphasize also the important role of territorial competition as evolutive cause of dulosis.

Species-specificity in trail pheromones and Dufour's gland contents ofCamponotus atriceps andC. floridanus (Hymenoptera: Formicidae)

By means of gas chromatography, gas chromatographic coupled mass spectrometry, trail-following experiments and electrophysiological recordings from worker antennae, the major trail pheromone components from the hindgut of the formicine speciesCamponotus atriceps andC. floridanus were identified as 3,5-dimethyl-6-(1′-methylpropyl)-tetrahydropyran-2-one and nerolic acid, respectively. The Dufour's gland contents of both species, investigated by gas chromatographic coupled mass spectrometry, show significant differences.

Anatomical origin and isolation of an ethological factor found on the last sternite of the workers of Myrmica rubra L. ( Formicidae, Myrmicinae)

On the basis of a logical series of deductions from experiments, it has been shown that the previously described ethological factor found on the last visible sternite of Myrmica rubra workers is a small amount of Dufour gland contents modified on the inner face of the last sternite. The factor may soak the outer surface of the sting or the gonostyles. This factor has, among others, a synergistic effect on the trail pheromone. When laying a trail, food-collecting ants deposit this factor on the ground together with the trail pheromone from their poison glands. The factor can be isolated on silica-gel plates and eluted once with acetone; its R f is 0.36. It resists a temperature of 100°C for at least 5 min and is more volatile than 3-ethyl-2,5-dimethylpyrazine, the trail pheromone of the species.

Chemical defense in the three European species ofCrematogaster ants

The composition of the Dufour gland of the antC. scutellaris has been reinvestigated by gas chromatography/mass spectrometry. The major components of the gland are (2E,5E,12Z)-4-oxoheneicosa-2,5,12-trien-1-ol acetate (1a) itsΔ 14 andΔ 16 double bond isomers (1b and1c), and the corresponding (Z,Z)-dienes5a and5b, all containing an acetylated C21 chain. The previously proposed structures1d, 1e, and5c, which are based on an homologous acetylated C23 chain, correspond to minor derivatives present in the gland. Traces of acetylated C19 homologs, tentatively identified as1g-1i, have also been found. The Dufour gland contents of the two other EuropeanCrematogaster species have also been studied.C. auberti is very similar toC. scutellaris in producing mainly1a, 1b and1c, together with the same higher and lower homologs, but it lacks the dienic derivatives5, whereasC. sordidula contains essentially the acetylated C19 compounds1g, 1h, and1i, accompanied by acetylated C17 homologs.

The Dufour gland contents of three species of Euro-African Messor ants and a comparison with those of North American Pogonomyrmex (Hymenoptera: Formicidae)

Key Word Index--Messor minor; Messor capitatus; Messor bouvieri; workers; queens; Dufour gland; harvester ants; caste differences. Abstract--The Dufour gland secretions of Messor minor, Messor capitatus and Messor bouvieri differ from those of other myrmicine ants so far studied in having no sesquiterpenoids present. M. minor resembles the North American harvester ants, Pogonomyrmex, in containing branched chain hydrocarbons. Messor and Pogonomyrmex appear anomalous among myrmicines and more closely resemble some formicines in this respect. M. minor queens contain chiefly pentadecene (57%), a substance absent from workers (major substance, tridecane, 33%), but are otherwise similar. M. capitatus workers contain tridecane (28%) and nonadecane (26%) and no branched hydrocarbons. M. bouvieriworkers contain linear hydrocarbons, with heptadecadiene (50%) as the major substance, but also small quantities of citronellyl decanoate, a new natural product.

Dufour gland contents of three species ofMyrmecia (Hymenoptera: Formicidae), primitive ants of australia

Chemical investigation of the Dufour gland contents of three species ofMyrmecia by GC and GC-MS showed thatM. gulosa andM. nigriceps contain predominantly linear hydrocarbons, whereasM. pilosula contains acetates, aldehydes, and propionates. The major components ofM. gulosa andM. nigriceps are (Z)-8-heptadecene, pentadecane, and heptadecane. Their chemical profiles are similar to each other and to that ofNothomyrmecia macrops, the most primitive living ant, placed by itself in a separate subfamily. The major components ofM. pilosula are hexadecyl acetate, (Z)-9-octadecenyl acetate, (Z)-11-eicosenyl acetate, and (Z)-11-eicosenal. Some geographical variation was observed in the relative proportions of the components. The chemotaxonomic significance for the primitive Australian ant subfamilies Myrmeciinae and Nothomyrmeciinae is considered. The possibility is discussed that 11-eicosenal or geranylcitronellol, minor components of the Dufour gland secretion ofM. gulosa, may be responsible for the aggressive behavior released by the natural stinging secretions.

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.

Chemical investigations of the Dufour gland contents of Attine ants

The Dufour glands of workers of the two subspecies Atta sexdens and Atta sexdens rubropilosa are completely filled with linear alkanes and alkenes in the C 15 to C 23 chain length range in microgram amounts. There are quantitative differences in the hydrocarbon composition between workers of the two subspecies. The major glandular component of A. s. sexdens is (Z)-9-tricosene, in A. s. rubropilosa the most abundant component is (Z)-9-nonadecene. From a chemical taxonomic viewpoint A. s. rubropilosa and A. s. sexdens could be regarded as separate species. The Dufour gland of Atta cephalotes is only partially filled with linear alkanes and alkenes in the C 12 to C 19 chain length range in nanogram amounts; n- heptadecane is the most abundant alkane and (Z)-9-nonadecene is the most abundant alkene.