Leaf-cutter Ant Atta Laevigata Research Articles

Mandible elemental composition and mechanical properties from distinct castes of the leafcutter ant Atta laevigata (Attini; Formicidae).

Leafcutter ant colonies are divided into castes with the individuals performing different tasks, based mostly on size. With the mandibles, the small minims care for the brood or the fungus, whereas the larger minors and mediae cut and transport plant material, with the ant size positively related to the material size. The mechanical properties and composition of the mandible cuticle have been previously tested in the soldiers as the largest caste, revealing that the cutting edges contained high contents of the cross-linking transition metal zinc (Zn). With regard to the smaller castes, no data are present. To study how the mandible size and function relates to its mechanical properties, we here tested the mandibles of minims, minors and mediae by nanoindentation. We found that the hardness (H) and Young's modulus (E) values increased with increasing ant size and that the mandible cutting edges in each caste have the highest H- and E-values. To gain insight into the origins of these properties, we characterized the elemental composition by energy-dispersive X-ray analysis, revealing that minors and mediae possessed higher content of Zn in the cutting edges in contrast to the minims containing significantly less Zn. This shows, that Zn content relates to higher mechanical property values. Additionally, it shows that all of these parameters can differ within a single species.

Perception and use of edible insects in Santa María de Itapinima and Piracemo indigenous communities, Mitú, Vaupés, Colombia

The indigenous communities of the Colombian Amazon East maintain their traditional knowledge for the use of their resources. Insects have been used as an alternative food that has been included as part of their daily diet. Fourteen species of edible insects belonging to 15 families of five orders were recorded in the communities of Santa María de Itapinima and Piracemo, located on the he Cuduyarí River in the department of Vaupés. According to its use value, mojojoy Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae), manivara Syntermes spinosus (Latreille) (Blattodea: Termitidae), leaf-cutting ant Atta laevigata (F. Smith) (Hymanoptera: Formicidae) and several species of moth caterpillars (Lepidoptera) commonly called as tapurú, are the most important species of edible insects. For each species, its ecological calendar was established, and its collecting techniques and methods, and traditional forms of preparation and consumption were documented. Through community pedagogical workshops, strategies for the conservation and sustainable use of edible insects were proposed, identifying research priorities in order to improve the food security of communities.

Perception and use of edible insects in Santa María de Itapinima and Piracemo indigenous communities, Mitú, Vaupés, Colombia

The indigenous communities of the Colombian Amazon East maintain their traditional knowledge for the use of their resources. Insects have been used as an alternative food that has been included as part of their daily diet. Fourteen species of edible insects belonging to 15 families of five orders were recorded in the communities of Santa María de Itapinima and Piracemo, located on the he Cuduyarí River in the department of Vaupés. According to its use value, mojojoy Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae), manivara Syntermes spinosus (Latreille) (Blattodea: Termitidae), leaf-cutting ant Atta laevigata (F. Smith) (Hymanoptera: Formicidae) and several species of moth caterpillars (Lepidoptera) commonly called as tapurú, are the most important species of edible insects. For each species, its ecological calendar was established, and its collecting techniques and methods, and traditional forms of preparation and consumption were documented. Through community pedagogical workshops, strategies for the conservation and sustainable use of edible insects were proposed, identifying research priorities in order to improve the food security of communities.

Differential parasitism by four species of phorid flies when attacking three worker castes of the leaf-cutting ant Atta laevigata (Smith, 1858).

Certain species of parasitic flies belonging to the Phoridae are known to attack Atta spp. workers foraging along trails, near nest openings used by the ants to supply the colony with plant material, and in the areas where the ants are actively cutting plant material. However, there have been no previous studies of phorid parasitism of non-foraging worker ants, for example excavators and soldiers. Excavators can be found on the surface around specialized nest openings, carrying and dumping soil on characteristic mounds. Soldiers can be found on the trails protecting foragers or guarding the different types of nest openings. The current study was performed to investigate the differential parasitism rates of Atta laevigata (Smith, 1858) worker castes by four species of phorids. Ants of all castes on trails and at nest entrances were collect from 18 mature colonies in the field. A total of 21,254 ants were collected from trails and 14,649 collected from the mounds of loose soil near nest openings. The captured workers were maintained under controlled laboratory conditions to evaluate the rate of parasitism. Of the ants collected from trails, 1,112 (5.23%) were found to have been parasitized, of which 1,102 were foragers and only 10 were soldiers. Of the ants collected from the soil mounds near the nest openings, only 27 (0.18%) were found to have been parasitized, of those 25 were excavators and 2 were soldiers. When evaluating parasitism of ants on the trails, 46.2% were attacked by Apocephalus attophilus Borgmeier, 1928, 22.6% by Myrmosicarius grandicornis Borgmeier, 1928, 16.6% by Eibesfeldtphora erthali (Brown, 2001) and 14.6% by Apocephalus vicosae Disney, 2000. Only two species of phorid, M. grandicornis and E. erthali, were observed parasitizing excavators, whilst only E. erthali parasitized soldiers. This is the first time that Atta spp. excavators and soldiers have been shown to be parasitized by phorids. The low rates of parasitism and specificity of certain phorid species for excavators and soldiers is discussed in relation to the behavioral interactions of hosts and their parasitoids, as well as the relationship between host and parasitoid size.

Dynamics of physical trail construction and of trail usage in the leaf-cutting ant Atta laevigata

Leaf cutting ants of the genus Atta build long lasting physical trails to exploit the vegetation around their nest. In this paper we investigated the dynamics of physical trail construction and usage in the leaf-cutting ant Atta laevigata. We assessed the average duration of physical trail construction in a pasture environment and estimated the impact of the change in the physiognomy of the terrain on ant speed, individual gross transport rate and rate of resource collection by taking into account the effects of confounding variables for each of these parameters. We also examined whether ants are able to adjust their foraging behaviour at the individual or collective level in order to maintain the same rate of vegetation return to their nest along the construction process. We found that a colony of A. laevigata needs between 4½ and 6½ days to complete a physical trail. The construction proceeded in a fairly uniform manner along the trail, suggesting that it is not the result of the coordinated action of a small group of specialized individuals progressing along the trail but rather of the sum of uncoordinated actions of individual workers. Ant speed increased by a 2.6 factor on a cleared trail compared to an uncleared trail and individual gross transport rate nearly doubled. However, there was no significant change along the construction process in traffic intensity, the proportion of ants returning to the nest with a piece of vegetation or the rate of resource delivery to the nest. The main benefit of trail construction is thus to mobilize less foragers on the trail to collect the same amount of food, leaving the possibility for the remaining workers to forage on other trails or to accomplish other tasks.

Good ant, bad ant? Soil engineering by ants in the Brazilian Caatinga differs by species

It is commonly acknowledged that ants improve the hydraulic properties of soils in which they build their nests. To date, however, most studies of such soil modifications have focused on one ant species and one type of ecosystem, rather than investigating how different ant species affect different types of land cover within the same landscape. Our study focused on modifications to water infiltration and surface texture of Haplic Luvisols by two ant species—one of them present only in a forest and the other present only in a pasture. These two sites are located near each other in the Caatinga, a tropical dry forest region of Brazil, and have similar climatic conditions and soil type. We found that in the forest site, soils undisturbed by ant activity already showed water infiltration 13 times higher than the similarly undisturbed soils of the pasture site; and that the ant Dinoponera quadriceps more than doubled water infiltration in their nest annular zones compared with the surrounding forest areas. In addition, D. quadriceps increased clay content in their mound soils by 50% compared with the soils of the surrounding forest. In contrast, at the pasture site, the leaf-cutter ant Atta laevigata had a mixed effect on water infiltration: compared with pasture matrix soils, their nest-building activities led to a threefold increase in infiltration of the mound soils, but a threefold decrease in the nest annular zones. In addition, compared with the pasture matrix, A. laevigata almost doubled sand content in their mounds—which explains the comparatively high infiltration rates. These results suggest that the contrasting soil modifications by the two species could lead to amplifying feedbacks in opposite directions: an ant species that depends on healthy forests is improving water infiltration and soil texture (and thus increasing water available to plants) in its environment, while another ant species that is known to profit from disturbances is having the opposite effect.

Detection and use of foraging trails of the leaf-cutting ant Atta laevigata (Hymenoptera: Formicidae) by Amphisbaena alba (Reptilia: Squamata)

Se provee información sobre un individuo de Amphisbaena alba (Reptilia: Squamata) que reconoce y usa un sendero de la hormiga cortadora de hojas Atta laevigata (Hymenoptera: Formicidae) en la sabana neotropical de Brasil. También registramos y describimos movimientos de desviación de obstáculos y el comportamiento de A. alba para reconocer el sendero de hormigas. Adicionalmente, discutimos cómo el mimetismo químico de A. alba pudiera estar involucrado en nuestra observación y sugerimos que esta relación va más allá de un simple inquilinismo, donde A. alba puede usar el nido como un sitio de reposo y alimentación para otros organismos asociados con nidos de hormigas cortadoras.

The mitochondrial genome of the leaf-cutter ant Atta laevigata: a mitogenome with a large number of intergenic spacers.

In this paper we describe the nearly complete mitochondrial genome of the leaf-cutter ant Atta laevigata, assembled using transcriptomic libraries from Sanger and Illumina next generation sequencing (NGS), and PCR products. This mitogenome was found to be very large (18,729 bp), given the presence of 30 non-coding intergenic spacers (IGS) spanning 3,808 bp. A portion of the putative control region remained unsequenced. The gene content and organization correspond to that inferred for the ancestral pancrustacea, except for two tRNA gene rearrangements that have been described previously in other ants. The IGS were highly variable in length and dispersed through the mitogenome. This pattern was also found for the other hymenopterans in particular for the monophyletic Apocrita. These spacers with unknown function may be valuable for characterizing genome evolution and distinguishing closely related species and individuals. NGS provided better coverage than Sanger sequencing, especially for tRNA and ribosomal subunit genes, thus facilitating efforts to fill in sequence gaps. The results obtained showed that data from transcriptomic libraries contain valuable information for assembling mitogenomes. The present data also provide a source of molecular markers that will be very important for improving our understanding of genomic evolutionary processes and phylogenetic relationships among hymenopterans.

Microsatellite loci characterized in the leaf-cutter ant Atta laevigata

BackgroundThe leaf-cutter ant Atta laevigata (Formicidae: Attini) is an agricultural pest largely distributed in the Neotropics and a model organism for studies of evolution, speciation and population genetics. Microsatellites are a very powerful tool for these kind of studies, but such markers are not available for studies on A. laevigata. In the present report, we describe the isolation and characterization of nine microsatellite loci in A. laevigata and the testing of these markers across other species of leaf-cutter ants.FindingsNine microsatellite loci, consisting of six dinucloeotide, one trinucleotide, one tetranucleotide, and one di/trinucleotide repeat motifs, were isolated and characterized. Primers and protocols were successfully designed to selectively amplify these markers. To test effectiveness of these markers for detailed population genetic studies, we genotyped female workers collected from 36 monogynic nests of A. laevigata and found that eight loci were within Hardy–Weinberg expectations, while the remaining locus had a deficiency of heterozygotes. Micro-Checker analysis of individuals from 55 monogynic nests indicated that loci Alae11, Alae24, Alae18 showed signs of null alleles. For the remaining six loci, the number of alleles per locus ranged between 2 and 11, with expected heterozygosity ranging between 0.07 and 0.88. All of these loci cross-amplified in other species of Atta.ConclusionsThese six polymorphic microsatellite loci should prove useful for future genetic investigations of the pest species Atta laevigata, as well as studies of other species of leaf-cutter ants in the genus Atta.

Plant palatability to leaf-cutter ants (Atta laevigata) and litter decomposability in a Neotropical woodland savanna

Although leaf-cutter ants have been recognized as the dominant herbivore in many Neotropical ecosystems, their role in nutrient cycling remains poorly understood. Here we evaluated the relationship between plant palatability to leaf-cutter ants and litter decomposability. Our rationale was that if preference and decomposability are related, and if ant consumption changes the abundance of litter with different quality, then ant herbivory could affect litter decomposition by affecting the quality of litter entering the soil. The study was conducted in a woodland savanna (cerrado denso) area in Minas Gerais, Brazil. We compared the decomposition rate of litter produced by trees whose fresh leaves have different degrees of palatability to the leaf-cutter ant Atta laevigata. Our experiments did not indicate the existence of a significant relationship between leaf palatability to A. laevigata and leaf-litter decomposability. Although the litter mixture composed of highly palatable plant species showed, initially, a faster decay rate than the mixture of poorly palatable species, this difference was no longer visible after about 6 months. Results were consistent regardless of whether litter invertebrates were excluded or not from litter bags. Similarly, experiments comparing the decomposition rate of litter from pairs of related plant species also showed no association between plant palatability and decomposition. Decomposition rate of the more palatable species was faster, slower or similar to that of the less palatable species depending upon the particular pair of species being compared. We suggest that the traits that mostly influence the decomposition rate of litter produced by cerrado trees may not be the same as those that influence plant palatability to leaf-cutter ants. Atta laevigata select leaves of different species based – at least in part – on their nitrogen content, but N content was a poor predictor of the decomposition rates of the species we studied.

Ant nests and soil nutrient availability: the negative impact of fire

Abstract:High-nutrient patches are important for regulating the structure and physiognomy of dystrophic habitats. Leaf-cutting ants create these rich patches in many neotropical habitats. Burning, however, could diminish or even annul the effects of ant nests on soil properties. To test this hypothesis, we compared the nutrient concentrations at various depths in soil samples near three nests of the leaf-cutting ant Atta laevigata and three non-nest soils, located in 10-ha plots subjected to burning or with fire-protection within a Brazilian cerrado. Root density in ant-nest soil was greater than in non-nest soil in both unburned and burned plots. Besides, the concentration of Ca, Mg, K and P increased 2–50-fold in ant nests from the unburned area compared to non-nest soils. In contrast, nutrient concentrations and pH in burned ant nests were similar to or lower than non-nest soils, but the nests maintained higher values of organic matter and cation exchange capacity. The positive effect of leaf-cutting ant nests as high-nutrient patches may be strongly reduced in habitats with frequent burning. In this case, the negative effects of leaf-cutter herbivory on a plant community could surpass the benefits of local nutrient enrichment by their nests.Resumo: Sauveiros modificam as propriedades físicas e químicas do solo, alterando a estrutura e fisionomia local. Entretanto, queimadas podem reduzir os efeitos dos formigueiros nesses ambientes como, por exemplo, pela diminuição do forrageamento das formigas e, conseqüentemente, pela baixa incorporação de material orgânico ao solo. Este estudo testou o efeito do fogo sobre a concentração de nutrientes no solo de colônias de Atta laevigata em área de cerrado. A densidade de raízes foi maior nas colônias do que áreas controle, independentemente da presença do fogo. Na ausência de queimadas, as concentrações de nutrientes foram até 50 vezes superiores nos sauveiros. Contudo, queimadas reduzem a concentração de nutrientes e pH nas colônias. Possivelmente, essa baixa concentração seja atribuída à maior demanda pela vegetação remanescente, em resposta à perturbação provocada pelo fogo. Nesse caso, os efeitos negativos da herbivoria podem superar os benefícios causados por meio da disponibilização de nutrientes pelos sauveiros.

Foraging patterns of the leaf-cutter ant Atta laevigata (Smith) (Myrmicinae: Attini) in an area of cerrado vegetation

Foraging rate can directly affect the impact that Atta laevigata (Smith) has on the environment. We attempted to assess the factors which most affect foraging rate of A. laevigata using data collected over a three month period in the Parque Nacional da Serra do Cipo in Minas Gerais, Brazil. A bimodal foraging pattern was observed on clear sunny days, based on collected dry weights of vegetative material being carried towards nest entrances. Sampled entrances on clear sunny days yielded a daily average dry weight twice as high (0.9713 ± 0.1358 g) as on rainy days (0.4485 ± 0.1120 g). Larger nests (0.9713 ± 0.1358 g) yielded higher dry weights than smaller nests (0.2752 ± 0.0463 g). Field observations showed Ants switched to nest entrances with more suitable microhabitat conditions in both rainy and sunny days. A combination of temperature, humidity, nest size, and microhabitat specialization were the most important factors influencing A. laevigata foraging pattern.

Parasitism characteristics of two phorid fly species in relation to their host, the leaf-cutting ant Atta laevigata (Smith) (Hymenoptera: Formicidae)

The leaf-cutting ants Atta sexdens (L.) and Atta laevigata (Smith) constitute serious pests of agriculture and forestry in Brazil. These ants are parasitized by the phorids Neodohrniphora tonhascai Brown and Neodohrniphora erthali Brown (Diptera: Phoridae), respectively. The parasitic potential of N. tonhascai against its host has been previously investigated, but no equivalent information is available for N. erthali. The objectives of this study were to evaluate the oviposition behavior and some biological characteristics of N. erthali in relation to its host and to determine the parasitic potential of N. tonhascai against A. laevigata, considering that in many parts of southeastern Brazil nests of A. sexdens and A. laevigata are found in close proximity of each other. These data were obtained from female N. erthali and N. tonhascai collected in the field in Viçosa (Minas Gerais State) and released singly in an observation chamber placed between a laboratory nest of A. laevigata and its foraging arena. Neodohrniphora tonhascai took less time selecting its hosts, attacked more ants and had greater rate of parasitism in relation to N. erthali. We could not establish whether A. laevigata is parasitized by N. tonhascai in the field, but the reproductive success of N. tonhascai in the laboratory demonstrated that A. laevigata is a suitable host to this parasitoid. The types of defense displayed by A. laevigata against both phorid species were markedly different, and these results suggest that foragers take specific defensive steps in order to reduce the possibility of parasitism by phorid flies.

Inter-population differences in the essential oils of Pinus caribaea needles.

Differences in volatile terpene content of Pinus caribaea needles and soil qualities between two pine plantations (Uverito and Sartenejas) in Venezuela were analyzed. Soils in the Uverito pine plantation were sandy, low in nutritional quality, and deficient in available nitrogen and phosphorus content. Pines grown on these soils presented in their needles higher concentrations of alpha-pinene, camphene, sabinene, myrcene+alpha-phellandrene mixture, beta-phellandrene, beta-caryophyllene, alpha-humulene, and a higher total monoterpene content than pines of the Sartenejas plantation, where soils were nutritionally richer and higher in nitrogen and phosphorus content. The hypothesis of the carbon/nutrient balance could explain these results. Alternatively, continuous stress on the pines of the Uverito plantation due to herbivory by the leafcutter ant Atta laevigata may induce, in part, the differences observed between these pines and those of the Sartenejas plantation.

Mandibular gland secretion in different castes of the leaf-cutter ant Atta laevigata

Gas chromatography analyses and behavioral assays showed that Atta laevigata, a highly polymorphic ant species, has a mandibular gland secretion that varies with castes. All castes contain 4-methyl-3-heptanone as the main component and its concentration is proportional to head size. Small workers and soldiers, but not medium size workers, also contain 4-methyl-3-heptanol. Queens show variations in their chemical composition after mating, as virgin males contain a secretion dominated by 4-methyl-3-heptanol, and, in a lesser proportion, 4-methyl-3-heptanone. In mated males these proportions are inverted. The compounds 4-methyl-6-hepten-3-one, 4-methyl-4-hepten-3-one, 6-methyl-tetradecene, and 2,6-dimethyl-2-dodecene are found only in queens. The behavioral response elicited by the secretion is mainly alarm, which is elicited more strongly by glands of larger workers. The results suggest that chemical castes, behavioral castes, and morphological castes overlap in this species.

Intraindividual variations of volatile terpene contents in Pinus caribaea needles and its possible relationship to Atta laevigata herbivory

Volatile terpene content variations in Pinus caribaea needles are examined in relation to season, dry hour, and canopy level. According to the results, the concentration of s-pinene was lower and that of sabinene and caryophyllene higher in the dry season than in the rainy season. s-Pinene, camphene, and s-phellandrene were more abundant in needles located at the lower canopy level, and limonene, α-ocimene, and the mixture of myrcene+α-phellandrene were more abundant at the upper canopy level. Camphene, sabinene, myrcene+α-phellandrene, and s-cadinene+γ-cadinene were more abundant in the afternoon, with lower concentrations at night. These results indicate that intraindividual variations in the contents of volatile terpenes in Pinus caribaea needles are significant even in regard to interindividual differences. The foraging pattern of the leafcutting ant Atta laevigata, as observed in a Caribbean pine plantation, could be, in part, related to these intraindividual variations.

Ant wars: combat strategies, territory and nest defence in the leaf-cutting ant Atta laevigata

Two laws have been highlighted when discussing combat strategies in ants: the linear law (in a series of one-to-one conflicts, a few good fighters are better than many poor fighters) and the square law (if all individuals are vulnerable to attack, numerous fighters are more advantageous than a few good fighters). The leaf-cutting ant, Atta laevigata, responded to a simulated vertebrate threat by recruiting many soldiers (large workers), but responded to conspecific and interspecific ant threats by recruiting mainly small ants. In staged intraspecific interactions in the field between adjacent nests, ants were reluctant to fight on unmarked land and often retreated onto established marked trails, retreated to the nest entrance which they then capped or guarded, or immediately began marking the battle site with Dufour's gland secretion. These results indicate that the territorial behaviour of A. laevigata is part of a complex system to defend resources, where the defence of one resource (food) can develop into the defence of another (the nest). During the build-up of a war, once individuals from two nests met, recruitment changed from medium and large ants to mainly small ants. It is suggested that A. laevigata uses the soldier caste to defend the nest against large organisms and recruits numerous small ants in response to conspecific and interspecific ant threats following the square law.

Territorial mechanisms in post-nuptial fligit gynes of the leaf-cutting ant Atta laevigata (F. Smith)

Territorial mechanisms in post-nuptial fligit gynes of the leaf-cutting ant Atta laevigata (F. Smith)

Nestmate recognition in the leaf-cutting antAtta laevigata

We tested matureAtta laevigata colonies in the field to see if the ants used queen substances, environmental odours (in this case odours produced by the nest's fungi), an odour produced by each individual, or a gestalt odour (resulting from odours distributed between nestmates) as a discrimination signal for nestmate recognition. We found that nestmate recognition inA. laevigata appears to be largely based on an odour produced by each nestmate which appears to be concentrated in the head, although other odours may also be used. We found no evidence of genetic relatedness influencing the discrimination ability, nor did ants respond differently to neighbors in comparison to non-neighbors.

Leaf-cutting antAtta laevigata (Formicidae: Attini) marks its territory with colony-specific dufour gland secretion

The workers of the leaf-cutting antAtta laevigata were found to mark a territory around their nest and along trunk trails. Elsewhere, we reported that the territorial mark had orientation and agonistic functions. The presence of this mark induced an alarm behavior in intruder workers and stimulated the residents' aggressiveness. Of the parts of the body tested, only the extracts from gaster or Dufour gland were able to induce the same agonistic behavior. The compoundsn-heptadecane, (Z)-9-nonadecene, 8,11-nonadecadiene, and (Z)-9-tricosene, secreted by Dufour gland were identified on foraging trails in the field as components of the territorial odor.