Cyclic release of carbon dioxide accompanied by abdominal telescoping movements in forager ants of Formica polyctena (Hymenoptera, Formicidae)

Abstract.  Discontinuous gas exchange and abdominal telescoping movements were investigated in intact forager ants of Formica polyctena Förster. For simultaneous recording of discontinuous gas exchange and abdominal movements, an electrolytic differential microrespirometer was combined with an infrared-optical device using an infrared-sensor diode commonly applied as a cardiograph in insect studies. The air in the insect chamber was saturated with water vapour, and an ant was contacted with a sliver of wet filter paper. Accordingly, the ants used in the experiments were regarded as being hydrated. The enforced immobility of the ant in the respirometry chamber (0.15 mL volume) induced continuous struggling during the first hours of measurement but, after 3–4 h, the activity periods alternated with quiescent periods when regular cycles of discontinuous gas exchange (8.97 mHz) were displayed. After remaining in the chamber for a day, the ants showed such cycles (8.15 mHz) without any interruption by periods of activity. The cyclic release of carbon dioxide (burst) was accompanied by a bout of telescoping movements of the abdominal segments (rapid contractions and slow relaxations), which were interpreted as active ventilation. The irregular and rare abdominal contractions, recorded during the interburst periods on the first day of measurements, were regarded as a symptom of stress because these disappeared on the second day. In approximately 20% of foragers, the telescoping movements during the interburst periods were characterized by very rapid (0.09 s) protractions and slow retractions of the abdominal segments, obviously acting as inspiration movements. The results do not support the hypothesis that discontinuous gas exchange is an adaptation for conserving water in ants.     

Lineage specific evolution of an alternative social strategy in Tetramorium ants (Hymenoptera: Formicidae)

The western Palearctic ant, Tetramorium moravicum , is the only species of the large genus known to display two alternative social strategies: macrogyny-monoygyny (characterized by one large queen per colony) and microgyny-polygyny (multiple small queens per colony). The microgyne colonies of this ant are confined to the westernmost part of its distribution area and occasionally co-occur with macrogyne colonies. We investigated phylogenetic and geographical patterns in relation to social strategy by analysing 1031 bp of the mitochondrial cytochrome c oxidase subunit I gene of T. moravicum from the entire known species range. Phylogenetic analyses revealed two clear-cut lineages coinciding with the eastern and western populations, which probably were separated after the late Quaternary glacial periods. Geographical distance analysis suggested allopatric fragmentation of the two lineages. We hypothesize that the two lineages colonized Central Europe postglacially from two directions. The current distribution gap of 500 km between the tip of the eastern lineage, in the Czech Republic, Austria and Hungary, and the western lineage, in Germany, was confirmed by hierarchical population analysis. Macrogyny-monogyny probably was the original condition in T. moravicum ; the alternative strategy of microgyny-polygyny may have evolved at the tip of the western lineage, as recently as the early Holocene.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 247–255.     

Nutrition of Borneo's ‘exploding’ ants (Hymenoptera: Formicidae: Colobopsis): a preliminary assessment

Functional effects of ants in rainforest canopies depend on difficult to characterize ant diets. In Bornean dipterocarp forests, certain diurnal, arboreal, territorial, and ecologically dominant ‘COCY’ ant species (Colobopsis cylindrica clade) grazed epiphytic biofilms on adaxial leaf surfaces, as well as on tree trunks and branches. Microscopic examination of worker buccal pellets revealed numerous (mainly ascomycete) fungal spores, together with insect appendages and cuticle. Direct observations, video‐imaging, and δ¹⁵N isotope data rule out feeding by predation, but isotopes cannot separate fungi from plant and insect exudates as principal nitrogen sources. Lipid‐rich products, extracted from pellets in situ, are hypothesized sources of essential sterols. Also present in pellets were colorful mandibular gland (MG) compounds unique to this ant clade and deployed, as a derived character state, in suicidal defense of foraging territories. Mildly antimicrobial and highly adhesive MG products also occur basally in the clade and may have first evolved for roles in microbial sterilization and food‐gathering and processing. Proteomic studies of YG COCY ants detected 2% proteins in hypertrophied, product‐filled MG reservoirs, but SDS‐PAGE qualitative analysis revealed mostly low‐molecular mass proteins and peptides (8–15 kDa), too small for enzymes but consistent with membrane‐binding proteins and/or antimicrobial peptides. Breakdown of chitin and chitosan in pellets may occur with enzymes derived from molting fluids in insect cuticle (proteases and chitinases) and/or fungi and bacteria. To the extent that COCY workers collect and consume pathogenic and/or beneficial phyllosphere microbes, ant effects on plants may be mediated by these activities.     

Invasion of Argentine ants (Hymenoptera: Formicidae) in South Australia: Impacts on community composition and abundance of invertebrates in urban parklands

Abstract The Argentine ant (Linepithema humile Mayr) is a worldwide invasive pest species that has been associated with losses of native ant and non‐ant invertebrates in its introduced range. To date, few studies have investigated the effects of Argentine ants on native invertebrates in Australia. This study assessed the effects of Argentine ants on community composition of invertebrates, with particular focus on resident ant communities and functional groups. In this study, the author compared the composition and abundances of invertebrates between invaded and uninvaded locations at four paired sites in Adelaide, South Australia. The results showed that there were significantly fewer non‐Argentine ants at invaded sites than at uninvaded sites. In particular, ants from the two common and widespread genera Iridomyrmex and Camponotus showed decreased abundances at the invaded sites. Multidimensional scaling analyses revealed differences in the composition of ant communities at the invaded and uninvaded sites, with uninvaded sites characterized by a similar native ant species composition, while communities at the invaded sites displayed much greater variability in species composition. These results suggest that the presence of Argentine ants may have a negative effect on particular ant genera and functional groups, with likely disruptions to ecosystem processes.     

Biogeography and endemism of ants (Hymenoptera: Formicidae) in Baja California, Mexico: afirst overview

Abstract Aims Ants (Hymenoptera: Formicidae) of the Baja California peninsula are poorly known, with information based largely on scattered museum and literature records. We provide the first comprehensive account of ant species occurring on the peninsula, we examine distribution patterns, and we assess the ‘peninsular effect’ which predicts that species richness declines from the base to the tip of a peninsula. Location Peninsula of Baja California, Mexico. Methods Data collection involved examining, identifying and recording label data from c. 2350 series of ants. These records provide a provisional, if incomplete, species list. We applied the incidence‐based estimator, Chao‐2, to our data base of specimen records to estimate the total number of ant species on the peninsula. We assessed endemism by comparing our peninsular species list to those from adjacent states. The peninsular effect was tested by comparing genus and species level richness between the two states of Baja California, and across five latitudinal blocks. Results We document 170 native ant species in thirty‐three genera, plus six non‐native species, in Baja California. It seems likely that additional species remain to be discovered: the Chao‐2 estimator of species richness, at 206.0 species, is about 20% higher than our observed species richness. About 30% of the species and 20% of the genera are restricted within Baja California to the relatively mesic California Floristic Province of north‐western Baja California. Nearly all of these species also occur in California. Forty‐seven species (27.6%) are peninsula endemics. Using our entire data set, the peninsular effect appears to be strong, with about twice as many species in the northern state of Baja California than are recorded from the southern state of Baja California Sur; the ratio of genera is 33 to 24. However, this effect becomes weak at the species level and absent at the genus level when minimizing habitat effects by omitting species restricted to the California Floristic Province. At a finer scale, across latitudinal blocks of about 1.9°, the number of species declines towards central portions of the peninsula and then increases in the Cape Region. Nine ant species display strongly disjunct distributions, and these occur in two general patterns: peninsula disjuncts and peninsula–mainland disjuncts. Main conclusions The Baja California peninsula supports a diverse and distinctive ant fauna, with the proportion of endemic species similar to that displayed by plants. Patterns of species and genus richness across the five latitudinal blocks provide poor support for the peninsular effect. Moreover, habitat diversity, especially that related to topographic relief, appears to be the most important factor affecting the gradient of ant species richness in Baja California. Additional collections are needed to develop a more complete species list and to determine the boundaries and status of many species. Nevertheless, the present data base provides a useful starting point for understanding the evolution of ant assemblages in Baja California and for comparison with peninsular patterns in other taxa.     

Resource Assessment, Recruitment Behavior, and Organization of Cooperative Prey Retrieval in the Ant Formica schaufussi (Hymenoptera: Formicidae)

Foragers of the ant Formica schaufussi recruit nestmates to large anthropod prey and cooperatively transport the prey to the nest. The size of the group of ants retrieving prey is significantly correlated with the prey mass at the point at which the retrieval group reaches the nest entrance. To understand the mechanism involved in this size matching process, the regulation of retrieval group size was investigated by examining the modulatory role of trail pheromones in recruitment communication and the behavioral processes that might adjust retrieval group size to prey mass. Laboratory studies of hindgut, poison, and Dufour's gland extracts showed that the contents of the hindgut, which was determined to be the source of trail pheromone, induced recruitment and orientation behavior in ants and regulated the recruitment response of ants in the absence of any other communication signal. However, chemical mass communication alone did not appear to explain the regulation of retrieval group size. Scout ants assess whether to collect prey individually or recruit nestmates to group-retrieve 100-, 200-, or 400-mg prey but did not vary group size in relation to either the prey mass or the presence of interspecific competitors once the decision to initiate group retrieval was made. The number of recruits leaving the nest was independent of these factors and first matched prey mass during prey transport, possibly through a process of differential individual response to immobile versus mobile prey items. Unpredictable factors such as prey resistance to movement and rapidly changing degrees of interspecific competition may preclude scouts from fine-tuning the retrieval group size before it reaches the prey.     

Brain GABA and glutamate levels in workers of two ant species (Hymenoptera: Formicidae): Interspecific differences and effects of queen presence/absence

Presence of amino acid neurotransmitters gamma‐aminobutyric acid (GABA) and glutamate (Glu) in ant brains was reported in very few studies. To learn more about factors influencing GABA and Glu levels in ant brains, we applied high‐performance liquid chromatography to measure levels of these compounds in single brains of workers of 2 ant species, Myrmica ruginodis (subfamily Myrmicinae) and Formica polyctena (subfamily Formicinae) taken from queenright/queenless colony fragments and tested in dyadic aggression tests consisting of an encounter with a nestmate, an alien conspecific or a small cricket. Brain glutamate levels were higher than those of GABA in both tested species. Brain GABA levels (in μmol/brain) and GABA : Glu ratio were higher in M. ruginodis (a submissive species) than in F. polyctena (a dominant, aggressive species) in spite of smaller brain weight of M. ruginodis. Brain glutamate levels (in μmol/brain) did not differ between the tested species, which implies that glutamate concentration (in μmol/mg of brain tissue) was higher in M. ruginodis. Queen absence was associated with increased worker brain GABA levels in F. polyctena, but not in M. ruginodis. No significant effects of opponent type were discovered. As GABA agonists enhance friendly social behavior in rodents, we hypothesize that elevated brain GABA levels of orphaned workers of F. polyctena facilitate the adoption of a new queen. This is the first report providing information on GABA and glutamate levels in single ant brains and documenting the effects of queen presence/absence on brain levels of amino acid neurotransmitters in workers of social Hymenoptera.     

Selection and sharing of sheltered nest sites by ants (Hymenoptera: Formicidae) in grasslands of the Australian Capital Territory

Abstract  In this study, it was investigated whether ants nesting under artificial rocks in a mesic south-eastern Australian grassland showed preference for nest sites with different temperature regimes. The study also allowed evaluation of competition between species for nest sites and observations of seasonality in brood and alate production in the nests of four common ant groups. On every sampling occasion more than 90% of nests were either Iridomyrmex spp., Rhytidoponera 'metallica' , Paratrechina sp. or Pheidole spp. Soil underneath thinner artificial rocks had higher average temperatures and warmed up earlier in the day and Iridomyrmex spp. and R. 'metallica' showed preference for establishing nests under these. While all ant nests had summer peaks in brood production, Iridomyrmex spp. and R. 'metallica' had brood observed throughout the year. Winged reproductives were commonly encountered in Iridomyrmex spp., R. 'metallica' and Paratrechina sp. nests, but only occasionally Pheidole spp. nests. Alates were present in the nests from February but released by all taxa after spring rains and were scarcely recorded in November, December and January when brood production was observed in most nests. Nest sites that offer protection from predators are an obvious advantage, but improved reproductive success can be gained in cool regions such as the mesic grasslands of the Australian Capital Territory by choosing nest sites with an optimal thermal regime.     

Competition between grass‐cutting Atta vollenweideri ants (Hymenoptera: Formicidae) and domestic cattle (Artiodactyla: Bovidae) in Argentine rangelands

相似文献   

Effects of nest size and dispersion on brood production in a North American population of wood ant Formica fusca (Hymenoptera: Formicidae)

We examined several key parameters of the population ecology of a North American population of Formica fusca (L.), including nest dispersion, colony size and brood production. Physical nest size was significantly correlated with colony size, and colony size, in turn, was significantly correlated with brood production. Sex allocation was male biased, although larger nests were more likely to produce reproductive female brood (gynes). Neither nest temperature nor moisture level was significantly correlated with brood production. Formica fusca nests in this population had a comparatively low average nearest-neighbor distance with a significantly even pattern of dispersion, which suggests relatively high intraspecific competition. However, nearest-neighbor distance was not significantly associated with either colony size or relative brood production.     

Loss of mating flight and shift in the pattern of carbohydrate storage in sexuals of ants (Hymenoptera; Formicidae)

Summary In ants, energy for flying is derived from carbohydrates (glycogen and free sugars). The amount of these substrates was compared in sexuals participating or not participating in mating flights. Results show that in participating females (Lasius niger, L. flavus, Myrmica scabrinodis, Formica rufa, F. polyctena, F. lugubris), the amount of carbohydrates, especially glycogen, was higher than in non-participating females (Cataglyphis cursor, Iridomyrmex humilis). Similarly, male C. cursor and I. humilis which fly, exhibit a much higher carbohydrate content than do the non-flying females of these species. Furthermore, the quantity of carbohydrates stored was generally higher in males than in females for each species. These results are discussed with regard to the loss of the nuptial flight by some species of ants.     

Colony genetic structure and queen mating frequency in fire ants of the subgenus Solenopsis (Hymenoptera: Formicidae)

Colony genetic structure was studied in natural populations of three fire ant taxa, Solenopsis richteri Forel, S. geminata (Fabr.), and hybrid S. invicta/richteri , using allozyme markers. All colonies studied exhibited arrays of female genotypes predicted under a model of monogyny (single functional queen) and monoandry (single insemination of queens). Males produced in the colonies appear to originate exclusively from the foundress queen, rather than from any virgin females present in the colonies. Thus these social insect colonies represent simple, albeit enormous, family groups. Single insemination and foundress parentage of males appear to be conserved reproductive traits in the subgenus Solenopsis , whereas another major determinant of colony genetic structure, the number of functional queens, is evolutionarily labile in this group.     

Size and fat content of gynes in relation to the mode of colony founding in ants (Hymenoptera; Formicidae)

Summary In ants, there are two main processes of colony founding, the independent and the dependent modes. In the first case young queens start colony founding without the help of workers, whereas in the second case they are accompanied by workers. To determine the relation between the mode of colony founding and the physiology of queens, we collected mature gynes of 24 ant species. Mature gynes of species utilizing independent colony founding had a far higher relative fat content than gynes of species employing dependent colony founding. These fat reserves are stored during the period of maturation, i.e. between the time of emergence and mating, and serve as fuel during the time of colony founding to nurture the queen and the brood. Gynes of species founding independently but non claustrally were found to have a relative fat content intermediate between the values found for gynes founding independently and those founding dependently. This suggests that such gynes rely partially on their fat reserves and partially on the energy provided by prey they collect to nurture themselves and the first brood during the time of colony founding. Study of the fat content of mature gynes of all species has shown that it gives a good indication of the mode of colony founding.     

Choice of food resource by bees and ants (Hymenoptera: Apoidea,Formicidae) on coconut tree inflorescences (Cocos nucifera,Arecaceae)

Coconut trees are mostly anemophilous; however, because bees and ants forage on coconut tree inflorescences for floral food, entomophilous pollination can also occur. The aim of this study was to determine the food resource preference of bees and ants while they collect pollen, nectar and, for ants, occasionally prey on coconut tree inflorescences, as well as to evaluate their impact on self-pollination. The number of ant visits to first female and then male flowers is significantly higher than that of bees. For Apis mellifera (L.) and Pseudomyrmex gracilis (Fabricius) 14% of the sequences were favorable to direct self-pollination. The probability of visits for all of the sequences was similar for both bees and ants and there was no difference in resource choice. For these reasons, neither can be considered a more effective pollinator of the coconut tree.     

Energetics of newly-mated queens and colony founding in the fungus-gardening ants Cyphomyrmex rimosus and Trachymyrmex septentrionalis (Hymenoptera: Formicidae)

Abstract.  The energetics of colony founding is investigated in the fungus gardening ants (Attini) Trachymyrmex septentrionalis and Cyphomyrmex rimosus . Similar to most ants, inseminated queens of these two species found nests independently unaccompanied by workers (haplometrosis). Whereas most ant founding queens seal themselves in a chamber and do not feed when producing a brood entirely from metabolic stores (claustral founding), the majority of fungus gardening ants must forage during the founding phase (semiclaustral founding). Laboratory-reared T. septentrionalis individuals comprise 84 dealate females collected after mating flights in June 2004. Twenty are immediately killed to obtain values for queen traits and another 20 after worker emergence for queen, fungus garden and worker traits. Cyphomyrmex rimosus comprise 22 dealate females collected in June 2005; ten of which are immediately killed and similarly prepared. Newly-mated T. septentrionalis queens have 25% of their dry weight as fat; whereas newly-mated C. rimosus queens contain 11% fat. These amounts are 50–75% less than most independently founding ant species. Trachymyrmex septentrionalis queens lose merely 5% of their energetic content during colony founding, whereas the total energetic content of their brood is more than three-fold the amount lost by the queen. Incipient T. septentrionalis colonies produce approximately half as much ant biomass per gram of fungus garden as do mature colonies. Similar to most ants, T. septentrionalis produces minim workers that are approximately 40% lighter than workers from mature colonies. Regardless of their size, T. septentrionalis workers contain much lower fat than do workers of claustral species. These data indicate that fungus gardening is adaptive because colonies can produce much cheaper offspring, making colony investment much lower.     

Chemical detection of the proteins and lipids in the fat body cells from workers of Attini ants (Hymenoptera: Formicidae)

The ultrastructural cytochemistry study and the chemical analysis carried out to examine the fat body of workers of the basal Attini Cyphomyrmex rimosus and Mycetarotes parallelus and the derived Acromyrmex disciger and Atta laevigata revealed very electrondense protein granules of varied sizes and shapes distributed throughout the cytoplasm of parietal and perivisceral trophocytes and oenocytes. Lipids were present in the cytoplasm of trophocytes as very electrondense granules. In M. parallelus, A. disciger, and A. laevigata, lipids were present as droplets. In parietal as well as perivisceral oenocytes, lipid granules were very electrondense. In A. laevigata, lipids were present as droplets. The chemical analysis using gas chromatography showed that the main lipid compounds present in trophocytes and oenocytes were saturated (myristic, palmitic, and stearic) and unsaturated fatty acids (oleic and linoleic). Also, in basal species, lipid compounds consisted of mainly saturated fatty acids, while in derived species saturated as well as unsaturated fatty acids were observed.     

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.     

Digestive enzymes of leaf-cutting ants, Acromyrmex subterraneus (Hymenoptera: Formicidae: Attini): distribution in the gut of adult workers and partial characterization

Enzyme activities associated with the labial glands, midgut and rectum of adult Acromyrmex subterraneus were investigated in order to understand their role in digestion of plant and fungal material. High chitinolytic activity was detected in the labial glands, indicating a possible role in the degradation of fungus ingested by the ants. Chitinolytic activity seen in other compartments of the alimentary canal probably originated in the labial glands. The highest activity detected in the midgut was for alpha-glucosidase, which was considered to be of insect origin due to its association with midgut epithelium and it is probably involved in glucose assimilation from nutrient sources such as maltose and sucrose present in plant material. A large range of enzyme activities were detected in the rectal lumen contents, and as in the midgut the highest values were for alpha-glucosidase activity. The absence of activity associated with the epithelium, in the particulate fraction, indicates that the rectal epithelium does not have a secretory function. The detection of enzymes in the rectal lumen contents, which were not detected in the midgut lumen contents, indicates that the rectum acts as a reservoir, accumulating enzymes. The major digestive enzymes were partially characterized using hydrophobic interaction chromatography, gel filtration and SDS-PAGE. The pH of the adult intestinal tract and flow rate of dye through the tract was investigated. A gradual acidification of the intestinal tract was noted commencing with the crop (pH 6-8.2) and terminating with the rectum (pH 3-5). The flow of dye through the different compartments of the tract showed a rapid fill time for all the gut compartments and a short residence time in the crop. In all other compartments, the dye remained detectable for 10 days or longer.     

Influence of ants (Hymenoptera: Formicidae) on honeydew excretion and escape behaviors in a myrmecophile,dalbulus quinquenotatus (Homoptera: Cicadellidae), and its congeners

Few leafhopper species are known to be ant-attended. Evidence is presented that unequivocally demonstrates that Dalbulus quinquenotatusis a myrmecophile. In a greenhouse study, the behavior of D. quinquenotatusand four Dalbulusspecies not associated with ants was observed in the absence and presence of the pavement ant, Tetramorium caespitum. D. quinquenotatusis readily contacted by tending ants and responds to stroking on the abdomen from ants' antennae by excreting and holding honeydew droplets until droplets are removed by ants. Nonattended Dalbulusspecies avoid contact with ants by walking,jumping, or flying away when approached. D. quinquenotatusexcretes three to six times the volume of honeydew as do two nonattended species, D. maidisand D. gelbus.Droplets of D. quinquenotatusare about 23% larger in diameter and excreted two to four times more frequently than for the other species. D. quinquenotatustakes about 0.15 s to form honeydew droplets on the anal tube, then holds the droplet an average of 0.28 s before expelling it when ants are absent. In the presence of ants, D. quinquenotatusholds the droplet an average of 1.31 s, which gives ants time to harvest the droplet. Nonattended species, however, immediately expel droplets from the anal tube after droplet formation. This ant-leafhopper mutualism apparently has evolved due to the ability of D. quinquenotatusto have extensive physical contact with ants and excrete large amounts of honeydew. D. chiapensis,a possible descendent of D. quinquenotatus,may secondarily have lost its mutualistic relationship with ants.