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.     

Venom and Dufour's gland secretions in an Australian species of Camponotus

Constituents of the venom (1) and Dufour's gland (25) have been characterized in an Australian representative of the highly evolved ant subfamily Formicinae. The venom reservoir of this ant, Camponotus intrepidus, contains formic acid, identified as the benzyl ester. The Dufour's gland contains a major hydrocarbon and a minor fatty acid fraction. Hydrocarbons include the normal alkanes, C₁₀ to C₁₇ (82 per cent); two series of monomethylalkanes, C₁₂, C₁₃, C₁₄, C₁₆, and C₁₇, the 3-methyl derivatives comprise approximately 16 per cent, and the 5-methylalkanes 2 per cent of the total; there are trace proportions of the n-alkenes, C₁₂, C₁₃, and C₁₅. The minor fatty acids, myristic, pentadecanoic, palmitic, and stearic are present in the ratio 2 : 2 : 12 : 11.     

Phéromones agrégeant les ouvrières de Myrmica rubra

The workers of Myrmica rubra aggregate around a source of one of their secretions, which can be called ‘alarm pheromone’, and also around workers of Lasius flavus. The mechanism of these aggregations differ.Both L. flavus workers and a solution in liquid paraffin of 3-octanol, one of the mandibular gland compounds, act as an arrestant for the workers of M. rubra. Both Dufour's gland secretion and a source of 3-octanone, the major compound of the mandibular gland secretion, are true attractants.The poison gland secretion, a mixture of 3-octanone and 3-octanol in liquid paraffin and a solution in liquid paraffin of 3-nonanone, a minor mandibular gland compound, all induce klinokinesis. The secretion of the mandibular glands and the secretion of the venom apparatus both cause positive klinokinesis and taxis. These locomotory reactions increase the probability that an object, marked by nest mates with these secretions, will be detected by several workers.When presented alone, 3-octanone is the only attractive compound in the mandibular gland secretion. However, a mixture of 3-octanone and 3-octanol (15 per cent of 3-octanol in the vapour phase) is detected more easily by the ants. The diffusion coefficients of the two compounds are different, and a mixture of these substances creates not only a quantitative but also a qualitative odour gradient. This may explain the synergy of the mixture.     

Fire ant trail pheromones: Analysis of species specificity after gas chromatographic fractionation

The specificity of the trail pheromones of four Solenopsis species was determined using natural trails. Dufour's gland extracts, and purified fractions from Dufour's gland extracts collected after gas-chromatographic separation. S. richteri and S. invicta possess species-specific major trail pheromones, while S. geminata and S. xyloni appear to have a common trail pheromone. Preliminary chemical characterization of the main trail pheromone of S. richteri indicates a M.W. of 218 and empirical formula of C₁₆H₂₆. The trail pheromone system of S. richteri consists of a blend of compounds and this phenomenon may also occur in the other species. The lowest concentration of their trail pheromone that workers of S. richteri could detect was about 10 fg per cm. The significance of blends of pheromones being utilized to generate chemical trails is discussed.     

Convergent evolution of the Dufour’s gland secretion as a propaganda substance in the slave-making ant genera Protomognathus and Harpagoxenus

Slave-making ants are social parasites which exploit the workforce of heterospecific slaves for their own reproduction, and to this end they have developed a variety of morphological and behavioural adaptations. Furthermore, social parasites utilize the chemical communication system of their hosts by breaking their nestmate recognition code, and some slave-maker species additionally employ semiochemicals as weapons during colony foundation and slaveraiding. Here, we demonstrate the use of such a ‘propaganda allomone’ by the North American myrmicine slave-maker Protomognathus americanus. This substance is produced in the Dufour’s gland and may be employed during slave raids to elicit panic among defending host workers. Slave-maker Dufour’s gland secretions evoked agitation and heightened levels of activity among host workers when applied directly on a host nest, and strong aggressive responses of nestmates when applied onto a host worker. Although the hosts own Dufour’s gland secretion also elicits intra-colonial fights, no support for the hypothesis was found that the slave-maker propaganda substance mimics a fertility signal of the host, as the chemical profile of the gland secretions is highly divergent between the two species. Preliminary results on the chemical composition of the secretion obtained by gas chromatography indicate that the propaganda substance of P. americanus differs from that of the related European slavemaker Harpagoxenus sublaevis, and is thus likely to represent an independent evolutionary development. Received 24 February 2005; revised 28 July 2005 and 2 March 2006; accepted 6 March 2006.     

Formic acid and saturated hydrocarbons as alarm pheromones for the ant Formica rufa

Releasers for the most intense, the fast-running, phase of the alarm behaviour were studied in worker ants of the formicine ant Formica rufa. The investigation was performed with a new technique in which the intensity and the duration of the behaviour pattern were measured in an objective and automatic way.Workers of formicine ants eiect a mixture of formic acid and the secretion from Dufour's gland against an enemy. The secretion from this gland in F. rufa consists of a great number of substances, 39 of which have been identified. The dominating substances form a homologous series of aliphatic, saturated hydrocarbons. Some of these hydrocarbons as well as the formic acid are alarm pheromones. The behavioural threshold value for one of these compounds, decane, was lower than 5.10¹³ molecules cm^?3 air. The threshold value for formic acid was estimated to 7.10¹⁵ molecules cm^?3 air. Formic acid and undecane are shown to belong to different reaction groups. The hydrocarbons, on the other hand, seem to affect the same kind of acceptor or receptor.The total intensity and duration of the alarm behaviour released by formic acid and one hydrocarbon are additive if the two substances are combined in a stimulus. A combination of two hydrocarbons and formic acid release a stronger behaviour than one hydrocarbon with formic acid even when the two stimuli contain the same number of molecules. The hydrocarbons have a combined effect and their relative concentrations regulate the intensity and duration of the alarm behaviour.     

Queen pheromones affecting the production of queen-like secretion in workers

The honeybee queen pheromones promote both worker sterility and worker-like pheromone composition; in their absence workers become fertile and express the queen pheromones. Which of the queen pheromones regulate worker pheromone expression and how, is still elusive. Here we investigated how two queen pheromones, the mandibular and Dufour’s, singly or combined, affect worker ovarian activation and occurrence of queen-like Dufour’s esters. Although queen mandibular pheromone (QMP) alone, or combined with Dufour’s secretion, inhibited to some extent worker reproduction, neither was as effective as the queen. The effect of the queen pheromones on worker pheromone expression was limited to workers with developed ovaries. Here too, QMP and Dufour’s combined had the greatest inhibitory effect. In contrast, treatment with Dufour’s alone resulted in augmentation of esters in the workers. This is another demonstration that a pheromone emitted by one individual affects the rates of its production in another individual. Ester production was tightly coupled to ovarian development. However fertile workers from queenright or QMP-treated colonies had significantly higher amounts of esters in their Dufour’s gland than untreated queenless colonies. The fact that the queen or QMP exert greater suppression on signal production than on ovary activation, suggests disparate regulatory pathways, and presents a challenging ultimate as well as proximate questions.     

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.     

The volatile Dufour's gland components of the harvester ants Pogonomyrmex rugosus and P. barbatus

The volatile Dufour's gland components of Pogonomyrmex rugosus and P. barbatus have been examined and found to be hydrocarbons. Homologous families of alkanes from this gland consisted of normal hydrocarbons ranging from n-dodecane to n-pentadecane and three types of methyl-branched homologues of the general formula C_nH_2n+1CH(CH₃)C_mH_2m+1, where n is 2, 4, or 5 and the sum of n and m is 10, 11, 12, or 13. The dimethyl-branched hydrocarbons 3,5-dimethyldodecane and 3,4-dimethyltridecane were also observed.     

Neural and hormonal control of Brunner's gland secretion

For many years it has been speculated that the physiological function of Brunner's glands was to secrete mucus to protect the proximal duodenum from the corrosive effects of acidified gastric juice. However the control of Brunner's gland secretion remains an enigma. Some evidence exists which indicates both cholinergic and adrenergic innervation of these glands, but current consensus weighs heavily in favor of a hormonal stimulus for glandular secretion. This is based in part on evidence obtained from denervated Brunner's gland pouches following a feeding stimulus. A number of hormones and hormone-like substances have been investigated as possible mediators in this secretory response, however, no specificity was ever demonstrated. The inability to pinpoint a given substance as a common mediator can be attributed to the fact that most active agents employed also affect duodenal motility. We present evidence that Brunner's gland secretion can be observed to be a diphasic response. The initial, transient response is always observed in the presence of increased duodenal motility. The sustained response does not require duodenal motility and is probably hormonally mediated.     

Identification of the components of Dufour gland secretion of the ant Myrmica rubra and responses to them

The Dufour gland secretion consists of a solution of volatile oxygenated compounds in a mixture of higher hydrocarbons and sesquiterpenoid alkenes. Methanol, butenone, 2-methylpropanal, and 1-butanol have now been identified as the remaining major volatile components. These substances have no strong behavioural effect upon ants, nor do they induce trail following behaviour. The principal activity of the Dufour gland can be traced to the three more abundant volatile components, ethanal, acetone, and butanone, together with the minor component ethanol.     

The hormonal control of salivary gland secretion in Drosophila melanogaster: Studies in vitro

The larval salivary gland of Drosophila melanogaster synthesises a complex secretion, known as ‘glue’. which is secreted at puparium formation and then cements the puparium to its substrate. This secretion is made during the third larval instar and is stored in the gland cells as large granules. A few hours before puparium formation it is secreted into the gland's lumen by exocytosis. This process is induced by ecdysone and can be studied in vitro. Secretion is initiated about 3.5 hr after exposure of glands to ecdysone and is complete by 8 hr. The effects of varying the ecdysone concentration, of inhibitors of RNA or protein synthesis, and of withdrawing the hormone at various times after initial exposure on the process of secretion have been studied. We conclude that some event(s) occurring during the first 3 hr exposure to ecdysone is necessary to initiate secretion of the glue into the gland lumen. The possible relationship between this event(s) and the ecdysone induced changes in gene activity (puffs) which occur in the salivary glands at the same time is discussed.     

Studies on the larval salivary gland of Drosophila: I. The nucleic acids

The localization and identification of the two nucleic acids, ribonucleic and desoxyribonucleic, have been determined for the larval salivary gland of Drosophila robusta. The determinations were made by the use of basic staining, Brachet's ribonuclease method, and the Feulgen reaction.The cytological observations suggest that the gland is functional as a secretory organ up to the mid-point of the third instar. It is during this period that the cytoplasmic basophilia (RNA) is most intense. When secretion ceases there is a decided decrease in RNA concentration. These findings suggest that the RNA system is concerned primarily with secretion.     

An empirical demonstration of risk-sensitive foraging preferences

We report laboratory experiments with yellow-eyed juncos (Junco phaeonotus) revealing that the birds' foraging preferences for variable rewards respond not only to the mean, but also the variance, of food rewards. The nature of their preferences for variable rewards is related to their expected daily energy budget. We summarize the birds' preferences in utility functions for energetic rewards. Since mean reward size is inadequate to predict their behaviour, we believe that foraging models should consider environmental stochasticity and an animal's response to this variation.     

Concentration effects and the response of Nemeritis canescens to a secretion of its host

An ovipositional response in the ichneumonid parasite Nemeritis canescens is elicited by a compound from the mandibular gland secretion of flour moth caterpillars. Exposure to that compound, even at concentrations too low to elicit an observable response, influences the parasites' subsequent response to a host larva or to the compound itself, increasing or decreasing that subsequent response to an extent that depends on the timing and on the amount of the compound at the initial exposure. When the same compound is deposited on the parasites' antennae, as by attacked host larvae, the parasites groom and oviposition is postponed.     

Antorbital and forehead secretions of black-tailed deer (Odocoileus hemionus columbianus): Their role in age-class recognition

Male black-tailed deer (Odocoileus hemionus columbianus) scent mark with their forehead gland secretion and antorbital sac contents. When forehead and antorbital sections were presented on the same nylon rod on an artificial tree, male deer discriminated between male yearlings' and fawns' secretions. When the secretions were presented separately, male deer discriminated between yearlings' forehead and antorbital secretions and blank controls. Discrimination was indicated by differential rates of sniffing and licking. In addition, the frequency of forehead rubbing of the scent marks appeared to be dependent on the dominance relationships of the male deer. Chemical evidence is presented which suggests that male yearlings' and fawns' antorbital secretions differ quantitatively. Females did not respond preferentially to these secretions and, with the exception of sniffing, responded significantly less than males.     

The volatile components of the mandibular gland secretion of workers of the ants Myrmica lobicornis and Myrmica sulcinodis

The mandibular glands of workers of M. lobicornis produce a mixture of 3-alkanones and 3-alkanols in the C₆–C₁₀ carbon chain length range, in addition to nanogram amounts of acetone, ethanal and 2-methylpropanal. Ethological studies have shown that the three major constituents, 3-octanol, 3-octanone and 3-decanol, are also the major pheromonally active components. When presented together they stimulate an alarm response in the workers similar to that induced by a worker's crushed head.In M. sulcinodis the mandibular gland secretion is composed of a mixture of the same ketones and alcohols, but in different proportions.     

Characterization of Antimicrobial Substances Produced by Enterococcus faecalis MRR 10-3, Isolated from the Uropygial Gland of the Hoopoe (Upupa epops)

The uropygial gland (preen gland) is a holocrine secretory gland situated at the base of the tail in birds which produces a hydrophobic fatty secretion. In certain birds, such as the hoopoe, Upupa epops, the composition of this secretion is influenced by both seasonal and sexual factors, becoming darker and more malodorous in females and in their nestlings during the nesting phase. The secretion is spread throughout the plumage when the bird preens itself, leaving its feathers flexible and waterproof. It is also thought to play a role in defending the bird against predators and parasites. We have isolated from the uropygial secretion of a nestling a bacterium that grows in monospecific culture which we have identified unambiguously by phenotypic and genotypic means as Enterococcus faecalis. The strain in question produces antibacterial substances that are active against all gram-positive bacteria assayed and also against some gram-negative strains. Its peptide nature identifies it as a bacteriocin within the group known as enterocins. Two peptides were purified to homogeneity (MR10A and MR10B), and matrix-assisted laser desorption ionization-time of flight (mass spectrometry) analysis showed masses of 5201.58 and 5207.7 Da, respectively. Amino acid sequencing of both peptides revealed high similarity with enterocin L50A and L50B (L. M. Cintas, P. Casaus, H. Holo, P. E. Hernández, I. F. Nes, and L. S. Håvarstein, J. Bacteriol. 180:1988-1994, 1998). PCR amplification of total DNA from strain MRR10-3 with primers for the L50A/B structural genes and sequencing of the amplified fragment revealed almost identical sequences, except for a single conservative change in residue 38 (Glu→Asp) in MR10A and two changes in residues 9 (Thr→Ala) and 15 (Leu→Phe) in MR10B. This is the first time that the production of bacteriocins by a bacterium isolated from the uropygial gland has been described. The production of these broad-spectrum antibacterial substances by an enterococcal strain living in the uropygial gland may be important to the hygiene of the nest and thus to the health of the eggs and chicks.     

Comparative study of the mandibular gland secretion of four species of Myrmica ants

The mandibular glands of the two species of ant, Myrmica ruginodis and Myrmica sabuleti contain a similar mixture of compounds, but the proportions are different. M. sabuleti produces ethanol, propanone, methylpropanal, 3-hexanone, 3-hexanol, 3-heptanone, 3-heptanol, 3-octanone, 3-octanol, 6-methyl-3-octanone, 6-methyl-3-octanol and 3-decanone. With the exception of 3-decanone these compounds were also found in M. ruginodis. These compounds were also found in M. rubra and M. scabrinodis.In both species now studied, the mandibular gland contents attract the workers and cause a large increase in their linear speed. In M. sabuleti these behavioural activities are due to 3-octanone and 3-octanol: the attraction of these two compounds in a synthetic mixture is exactly like that of an isolated mandibular gland; the compounds act in synergy to cause an increase in the ants' linear speed. Workers of M. ruginodis specifically respond to a mixture of ethanol, 3-octanone and 3-octanol: the alcohol only moderates the ethological action of the ketone, which is a true attractant and causes a very large increase in the ants' velocity; ethanol also attracts workers, acting in this respect in synergy with 3-octanone.These chemical and behavioural results are combined with those previously reported (Cammaerts-Tricot, 1973; Morganet al., 1978) to explain the responses of M. rubra, M. ruginodis, M. sabuleti and M. scabrinodis workers to isolated mandibular glands from each of these four species.     

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.