Myrmecia Gulosa Research Articles

A Review of Jaw Morphology and Foraging Behaviour in the Bulldog Ant (Myrmecia Gulosa) Group

Formicidae are one of the most diverse groups that, along with termites, make up one third of the total animal biomass on Earth. Contributing to their success is the large variety of foraging behaviours and morphologies ants have evolved in response to various food supplies. On the world continent Gondwana, Myrmeciinae, were the dominant group with many characters considered primitive or ancestral within Formicidae. The Myrmecia gulosa group retains ancestral traits of the Myrmeciinae, now found only in Australia. This research aims to a review the facial morphologies and foraging behaviours of the M. gulosa group to better understand their unique success in Australia, compared to their demise elsewhere. Evaluation of jaw morphology, foraging behaviour, and geographical distribution revealed a narrow range of morphologies and consistent foraging behaviour across 41 of 42 studied species all over Australia. Based on similar morphologies of 41 species and behaviours of eleven, eight of which were considered well researched, it is possible that understudied M. gulosa species will demonstrate traits similar to well-researched species. It appears that M. gulosa species maintained ancestral traits that failed to allow the present-day success of Myrmeciinae elsewhere, and likely allowed the diversification of other ant genera. The following collated results suggests, members of the M. gulosa species group appear not to face the same food resource selective pressures that led to diversification in other ant genera and further supports food resources as an important selective pressure for other ant genera that M. gulosa possibly failed to adapt to.

A peptide toxin in ant venom mimics vertebrate EGF-like hormones to cause long-lasting hypersensitivity in mammals

Venoms are excellent model systems for studying evolutionary processes associated with predator-prey interactions. Here, we present the discovery of a peptide toxin, MIITX2-Mg1a, which is a major component of the venom of the Australian giant red bull ant Myrmecia gulosa and has evolved to mimic, both structurally and functionally, vertebrate epidermal growth factor (EGF) peptide hormones. We show that Mg1a is a potent agonist of the mammalian EGF receptor ErbB1, and that intraplantar injection in mice causes long-lasting hypersensitivity of the injected paw. These data reveal a previously undescribed venom mode of action, highlight a role for ErbB receptors in mammalian pain signaling, and provide an example of molecular mimicry driven by defensive selection pressure.

A pain-causing and paralytic ant venom glycopeptide

SummaryAnts (Hymenoptera: Formicidae) are familiar inhabitants of most terrestrial environments. Although we are aware of the ability of many species to sting, knowledge of ant venom chemistry remains limited. Herein, we describe the discovery and characterization of an O-linked glycopeptide (Mg7a) as a major component of the venom of the ant Myrmecia gulosa. Electron transfer dissociation and higher-energy collisional dissociation tandem mass spectrometry were used to localize three α-N-acetylgalactosaminyl residues (α-GalNAc) present on the 63-residue peptide. To allow for functional studies, we synthesized the full-length glycosylated peptide via solid-phase peptide synthesis, combined with diselenide–selenoester ligation-deselenization chemistry. We show that Mg7a is paralytic and lethal to insects, and triggers pain behavior and inflammation in mammals, which it achieves through a membrane-targeting mode of action. Deglycosylation of Mg7a renders it insoluble in aqueous solution, suggesting a key solubilizing role of the O-glycans.

Venom chemistry underlying the painful stings of velvet ants (Hymenoptera: Mutillidae).

Velvet ants (Hymenoptera: Mutillidae) are a family of solitary parasitoid wasps that are renowned for their painful stings. We explored the chemistry underlying the stings of mutillid wasps of the genus Dasymutilla Ashmead. Detailed analyses of the venom composition of five species revealed that they are composed primarily of peptides. We found that two kinds of mutillid venom peptide appear to be primarily responsible for the painful effects of envenomation. These same peptides also have defensive utility against invertebrates, since they were able to incapacitate and kill honeybees. Both act directly on cell membranes where they directly increase ion conductivity. The defensive venom peptides of Dasymutilla bear a striking similarity, in structure and mode of action, to those of the ant Myrmecia gulosa (Fabricius), suggesting either retention of ancestral toxins, or convergence driven by similar life histories and defensive selection pressures. Finally, we propose that other highly expressed Dasymutilla venom peptides may play a role in parasitisation, possible in delay or arrest of host development. This study represents the first detailed account of the composition and function of the venoms of the Mutillidae.

Comparisons of Protein and Peptide Complexity in Poneroid and Formicoid Ant Venoms

Animal venom peptides are currently being developed as novel drugs and bioinsecticides. Because ants use venoms for defense and predation, venomous ants represent an untapped source of potential bioactive toxins. This study compared the protein and peptide components of the poneroid ants Neoponera commutata, Neoponera apicalis, and Odontomachus hastatus and the formicoid ants Ectatomma tuberculatum, Ectatomma brunneum, and Myrmecia gulosa. 1D and 2D PAGE revealed venom proteins in the mass range <10 to >250 kDa. NanoLC-ESI-QTOF MS/MS analysis of tryptic peptides revealed the presence of common venom proteins and also many undescribed proteins. RP-HPLC separation followed by MALDI-TOF MS of the venom peptides also revealed considerable heterogeneity. It was found that the venoms contained between 144 and 1032 peptides with 5-95% of peptides in the ranges 1-4 and 1-8 kDa for poneroid and formicoid ants, respectively. By employing the reducing MALDI matrix 1,5-diaminonapthalene, up to 28 disulfide-bonded peptides were also identified in each of the venoms. In particular, the mass range of peptides from poneroid ants is lower than peptides from other venoms, indicating possible novel structures and pharmacologies. These results indicate that ant venoms represent an enormous, untapped source of novel therapeutic and bioinsecticide leads.

Changes in the cuticular hydrocarbons of incipient reproductives correlate with triggering of worker policing in the bulldog ant Myrmecia gulosa

In social insects, conflicts over male parentage can be resolved by worker policing. However, the evolution of policing behavior is constrained by the ability of individuals to identify reproductive nestmates, or their eggs. We investigated the occurrence of worker policing and its underlying chemical communication in the bulldog ant Myrmecia gulosa. Although workers have functional ovaries and can lay male-destined eggs, they do not reproduce in queenright colonies. To determine if their sterility is a consequence of worker policing, we experimentally induced worker reproduction in the presence of a queen. Some individuals were seized and immobilized by nestmates, and sometimes killed as a consequence. Although the ovarian development of immobilized individuals was variable, their cuticular hydrocarbon profiles were intermediate between reproductive and nonreproductive workers, indicating they were in the process of starting to reproduce. Approximately 29% of these incipient reproductive workers were successfully policed. To test for policing on eggs, we transferred viable worker eggs to queenright colonies and monitored their acceptance. Furthermore, we compared the surface hydrocarbons of the different types of eggs to determine whether these chemicals could be involved in egg recognition. We found that although there were differences in hydrocarbon profiles and discrimination between queen and worker-laid eggs, viable eggs were not destroyed. Our results strongly support the idea that cuticular hydrocarbons are involved in the policing of reproductive workers. A low level of worker policing appears sufficient to select for self-restraint in workers when few fitness benefits are gained by selfish reproduction. Policing of eggs may thus be unnecessary.

Role of the queen in regulating reproduction in the bulldog ant Myrmecia gulosa: control or signalling?

Ant queens generally monopolize reproduction, even though workers are able to produce males in orphaned colonies. The mechanisms maintaining worker sterility in the presence of a queen remain inadequately understood. In species with small societies, queens may use agonistic interactions, whereas pheromones are more efficient in large colonies. Whether such pheromones represent coercive tools or honest signals has not been established. We investigated behavioural interactions between queen and workers in the bulldog ant Myrmecia gulosa, a species with limited queen–worker dimorphism and small colonies. About 1.6% of a queen’s time budget was spent visiting nest chambers, but there was no aggression and the workers sought contact with their queen, suggesting that pheromones are involved. Cuticular hydrocarbons deposited on the nest substrate by the queen were attractive to workers, but were not necessary for regulating their sterility. Confined queens were able to prevent worker oviposition. Myrmecia gulosa is monogynous and probably monandrous, and workers could maximize their fitness by producing sons and rearing nephews. None the less, they refrained from reproduction in the presence of a fertile queen, even though there was no queen policing. Worker sterility seems to be selected to maximize colony productivity. Our results provide evidence against the notion that queen pheromones inhibit worker oviposition.

Cuticular hydrocarbons mediate discrimination of reproductives and nonreproductives in the ant Myrmecia gulosa.

In many species of social insects, the cuticular hydrocarbons of adults vary with both colony identity and individual physiology (oogenesis). Such variations have been shown in some ants and social wasps to function in nestmate recognition, but as yet there is no demonstration of their use by workers to recognize egg layers. We report that in the ant Myrmecia gulosa, workers can discriminate queens and fertile workers from infertile individuals based on distinctive blends of long-chained hydrocarbons present both on the cuticle and in the postpharyngeal gland. The purified hydrocarbon fraction of cuticular extracts from queens elicited high interest in workers, unlike the nonhydrocarbon fraction. However, both fractions were necessary to trigger a response of maximal intensity. In contrast, extracts of mandibular and Dufour glands from queens or infertile workers were not treated differentially by workers. We suggest that cuticular hydrocarbons function as pheromones allowing for recognition of the queen as well as egg-laying workers.

Caste specialization and differentiation in reproductive potential in the phylogenetically primitive ant Myrmecia gulosa

Division of labour is associated with morphological specialization in many species of social insects. Comparative data on phylogenetically "primitive" ants can help understand the selective forces promoting the production of multiple worker castes as well as the morphological divergence between queens and workers. We quantified size variations among workers and queen-worker dimorphism in the Myrmeciinae ant Myrmecia gulosa. Worker size varies over a wide range (14–23 mm), exhibiting a bimodal distribution. Growth is monophasic and only slightly allometric. Workers do not perform trophallaxis but lay trophic eggs, which constitute the main channel of food exchange in the colony. Large individuals have more ovarioles than small individuals and lay more trophic eggs. The difference in egg output persists when orphaned workers start to reproduce. Although small workers are less fecund, they reproduce more readily than large individuals following queen removal. Queens are not much larger than the largest workers, but have disproportionately more ovarioles and have a 10-fold higher egg-laying rate than workers. We examine size frequency distribution and bi-logarithmic plots of head and gaster measurements in order to infer the developmental processes that generate divergence in size and proportion among colony members. The appearance of two classes of workers in M. gulosa has not been accompanied by a loss in reproductive potential as in some "higher" ants. We review the morphometric studies available for Myrmecia, and discuss the evolution of morphological specialization in the genus.

Increase in levels of microbiota recoverable from male and larval Myrmecia gulosa (Fabricius) (Hymenoptera: Formicidae) following segregation from worker ants

The segregation of laboratory maintained male and larval Myrmecia gulosa from workers resulted in increased levels of culturable microbiota. After 29 days, microbial levels recovered from segregated males and larvae were 27 and 126 times greater than from males and larvae not segregated from workers. These findings are consistent with the hypothesis that metapleural gland secretions, absent in larvae and males, are transferred from workers to larvae, and males contribute to the inhibition of cuticular microbiota.

Isolation from an Ant Myrmecia gulosa of Two Inducible O-Glycosylated Proline-rich Antibacterial Peptides

Reported here is the isolation and characterization of two antibacterial peptides synthesized in an ant Myrmecia gulosa in response to bacterial challenge. The peptides were purified by reversed-phase high performance liquid chromatography and characterized by peptide sequencing and mass spectrometry. Both peptides were formed from 16 amino acids, were rich in proline ( approximately 30%), and had N-acetylgalactosamine O-linked to a conserved threonine. The activity of a synthetic non-glycosylated isoform was markedly reduced demonstrating that glycosylation was necessary for maximum activity. The peptides were active only against growing Escherichia coli. They were inactive against stationary cells, Gram-positive bacteria, the yeast Candida albicans, two species of mammalian cells, and bovine pestivirus.

Antimicrobial mode of action of secretions from the metapleural gland ofMytmecia gulosa(Australian bull ant)

Secretions from exocrine metapleural glands of Myrmecia gulosa (Australian bull ant) exhibit broad-spectrum antimicrobial activity. Treatment of the yeast Candida albicans with metapleural secretion resulted in the rapid and total leakage of K+ ions from cells within 10 min. Ultrastructural analysis of the bacteria Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa, and cells and protoplasts of Candida albicans demonstrated gross damage of the cell membrane and aggregation of the cytoplasmic matrix of treated cells. Degradation of membrane-bound organelles was also observed in Candida albicans. The antimicrobially active components of metapleural secretions were nonpolar and interacted with the phospholipid bilayer, causing damage to the structural integrity of liposomes and the release of carboxyfluorescein. The data suggest that the antimicrobial agents in metapleural secretion act primarily by disrupting the structure and function of the phospholipid bilayer of the cytoplasmic membrane.

Immediate allergic reactions to Myrmecia ant stings: immunochemical analysis of Myrmecia venoms

IgE antibody reactivities to the venoms of Myrmecia pilosula, Myrmecia nigrocincta, Myrmecia tarsata, Myrmecia pyriformis, Myrmecia simillima and Myrmecia gulosa have been identified in sera from subjects allergic to ant venom. Sera with IgE reactivity to only a single Myrmecia venom most often recognize M. pilosula venom although all six venoms appear capable of inducing IgE antibodies. The six different Myrmecia venoms were electrophoretically separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Western blotted to nitrocellulose and probed with sera from ant venom-allergic subjects. Four to six IgE-binding components ranging in size from 2 to 25 kDa were identified in each of the venoms. Similarities in molecular weights of the IgE-binding components exist and close taxonomic relationships between the species suggest that common or similar peptides may be present in the different venoms.

A POSSIBLE EXPLANATION FOR SIZE DIFFERENCES IN THE METAPLEURAL GLANDS OF ANTS (HYMENOPTERA: FORMICIDAE)

AbstractPosterior thoraces of the queen, male and worker castes of the bull ants Myrmecia gulosa F. and M. urens Lowne were examined by light and scanning electron microscopy. Metapleural glands are present in queens and workers but absent in males. There are differences in gland size and cell number, both between species and between queen and worker castes. Our data, together with previously published data, show that cell number is positively correlated with overall body size, suggesting that variation in gland size is functionally related to surface area. Because metapleural secretions have strong antibiotic properties, this relationship may be to provide sufficient secretion to cover the integument.

Antimicrobial properties of secretions from the metapleural glands of Myrmecia gulosa (the Australian bull ant).

Myrmecia gulosa (Australian bull ant) produce secretions from their metapleural exocrine glands which have broad spectrum antimicrobial properties. Such secretions are probably of importance in disease control in bull ant communities. These antimicrobial secretions are stable at 100 degrees C, resistant to proteolytic enzymes and are active over a wide pH range. Of the organisms tested only endospores of Bacillus cereus were found to be resistant. The antimicrobial agent(s) are absorbed by cells and result in cell lysis. The secretions do not interfere with any growth-related processes. These observations demonstrate that insects may be a source of novel antimicrobial agent(s).

Formula omitted] from the head of the bull ant Myrmecia gulosa (Fabr.)

2,5- Dimethyl-3-n- propylpyrazine has been identified as the sole pyrazine in the head of the Australian bull ant Myrmecia gulosa. The compound is present in approx. 400 ng per ant.

Graded and discrete receptor potentials in the compound eye of the Australian Bulldog-ant (Myrmecia gulosa)

1. Graded and discrete receptor potentials are recorded from the visual cells of the Australian Bulldog-ant. The intensity dependence of the graded responses is described by a new formula [Eq. (3)]. While the frequency of the discrete potentials in relation to the number of light quanta fits best a Poisson distribution, the graded potentials are best described by a logarithmic Gaussian distribution. 2. It is shown that the non-linear summation of single bumps and the reduction of the bump amplitude lead to a logarithmic intensity dependence. 3. The frequency spectrum of single bumps is measured with a Fast-Fourier-Analysis. It is observed that the harmonic frequencies have a negative slope around 12 dB/octave. 4. A difference is found in the higher harmonics of bumps generated at lower light intensities from those generated at higher light intensities. It is shown that this difference becomes more obvious if the bumps are further divided into short and longer latency groups. 5. From these results, it is concluded, that there is a mutual influence between neighbouring visual cells. Using this influence as a basis, a model of the low electric coupling between the cells is discussed.

Visually mediated snapping in the bulldog ant: A perceptual ambiguity between size and distance

1. The isolated head of the bulldog ant,Myrmecia gulosa, snaps its mandibles in a predictable way in response to an approaching target, allowing the isolation of a single visually mediated component from the complex prey capture repertoire of intact animals. 2. The timing of the response depends on both the size of the target and its position relative to the animal's visual midline (Figs. 2, 12, 13). Except for a latency component, the snapping is velocity independent (Fig. 3). 3. Only 14% of the animals tested continued to respond to the targets when vision in one eye was occluded. Although monocular responses occurred at the same mean target distance as binocular responses, the variance was significantly greater (Figs. 4, 5). 4. Optical measurements of the visual field ofM.gulosa indicate a binocular overlap of nearly 60° (Figs. 7, 9). 5. Correlation of behavioral and optical measurements suggest that the snapping is triggered when the edge of any size target comes into the visual field of a small group of facets (Figs. 9, 10). 6. These experiments with the isolated head preparation show that the bulldog ant cannot judge the absolute distance of a target in the visual field when limited to primary visual cues, and suggest that two eyes are better than one simply because they provide more input.

Insect UV-, and green-photoreceptor membranes studied by the freeze-fracture technique.

The membranes of the microvilli of UV- and green-photoreceptors of the ant Myrmecia gulosa have been studied with the freeze-fracture technique. Both inner fracture faces, the cytoplasmic P-face and the extracellular E-face, are covered by globular particles. The P-face particles appear to be randomly distributed, occasionally forming clusters. Their density is about 7,000/mum2, and their mean diameter is 8.5 nm. The E-face particles, however, are arranged in an ordered square pattern with a center-to-center spacing of 9 nm. The density and distribution of P- and E-face particles are the same in both the UV- and the green-photoreceptor membranes. No differences were found in the ultrastructural organization of photoreceptor membranes after dark or light adaptation. It is suggested that the P-face particles represent rhodopsin molecules.

Release of aggressive and capture behaviour in the antMyrmecia gulosa F. by exocrine products of the ant Camponotus

SYNOPSISAn account is given of the behaviour of workers of Myrmecia gulosa in the presence of formic acid and undecane (substances produced by its normal prey Camponotus). Comparative studies with three other species of Myrmecia are described.