Leaf-cutting Ants Research Articles

Divergent reproductive responses of Caatinga dry forest plants to leaf-cutting ant herbivory

Herbivory is one of the key processes shaping life history traits linked to plant fitness and the leaf-cutting ants are amongst the most voracious and polyphagous herbivores of the Neotropics. They extensively harvest aboveground plant parts to grow their symbiotic fungus, including vegetative and reproductive tissues. Although leaf-cutting ant herbivory is expected to reduce plant reproductive success, the potentially different outputs of damage to vegetative and reproductive parts are still poorly known. This study investigates the influence of Atta opaciceps herbivory on the reproductive success of three plant species native to the Caatinga dry forest: Croton argyrophylloides (Euphorbiaceae), Cenostigma pyramidale, and Indigofera suffruticosa (Leguminosae). We selected 10 adult and active nests of A. opaciceps based on the presence of individuals of the three focal plant species in their vicinity. For each colony, we marked four individuals of each plant species (totaling 12 individuals per colony), which were then subjected to one of four herbivory treatments: (1) ant herbivory on both reproductive and vegetative parts, (2) manually simulated herbivory on the reproductive parts alone, (3) ant herbivory exclusively on vegetative parts, and (4) no herbivory. From January to April 2020, we monitored all 120 individuals, recording the number of inflorescences, flower buds, flowers, fruits, and the proportion of flowers maturing into fruits (fruit set, as a proxy of reproductive success). Results revealed variations in reproductive structure production and divergent responses to leaf-cutting ant herbivory among our focal species. In terms of inflorescence, flower bud production, and fruit set C. argyrophylloides showed reduced numbers when subjected to higher levels of total herbivory (reproductive and vegetative parts), but increased inflorescence and flower bud production when plants suffered only leaf damage. Cenostigma pyramidale individuals under partial herbivory displayed lower flower bud numbers than protected ones. In contrast, I. suffruticosa displayed conflicting results, with fully exposed plants producing more inflorescences than partially exposed counterparts and more flowers than leaf-damaged and protected individuals. Despite the varied effects on different plant parts across all three study species, the overall reproductive success (i.e. fruit set) of only one species (C. argyrophylloides) was significantly reduced by leaf-cutting ant herbivory. The resilience of the two other plant species to leaf-cutting ant pressure may be attributed to compensatory mechanisms, shedding light on the intricate interplay between herbivores and plants in the Caatinga dry forest. As leaf-cutting ants proliferate in response to anthropogenic disturbances, the patterns described in this study may become more pronounced, potentially affecting the organization of plant communities in the Caatinga dry forest.

Flavonoids from Kalanchoe ×laetivirens Impair Survival and Immunity of Atta sexdens (Hymenoptera: Formicidae)

Background: The active secondary metabolites of various Kalanchoe species are promising for controlling insects and other agricultural pests. Objective: This study aimed to evaluate the mortality and immune responses of the leafcutter ant Atta sexdens (L.) after treatment with Kalanchoe ×laetivirens (Desc.) aqueous extract. The effects on an aquatic organism used as a bioindicator, Chironomus xanthus (Rempel), were also evaluated. Methods: Different K. ×laetivirens concentrations were prepared by dilution in honey to assess the toxicity and determine the median lethal concentration (LC50) for A. sexdens workers. The haemocytes of workers treated with a sublethal concentration (0.005 g/mL) were counted. Results: The plant extracts induced high mortality in A. sexdens workers. All concentrations, except 0.001 g/mL, increased mortality rates. The sublethal concentration negatively affected the immune system of A. sexdens workers 48 and 72 h after ingestion. The flavonoids 4″″-acetylsagittatin A, sagittatin A and the nucleosides uridine and adenosine were identified. The LC50 of the K. ×laetivirens (128.1 mg /L) was determined for the non-target organism, C. xanthus. Conclusion: These natural compounds can be used in future research to plan alternative control strategies for leafcutter ants in forests and other agroecosystems.

Large deformation diffeomorphic mapping of 3D shape variation reveals two distinct mandible and head capsule morphs in Atta vollenweideri leaf-cutter worker ants.

Ants are crucial ecosystem engineers, and their ecological success is facilitated by a division of labour among sterile "workers". In some ant lineages, workers have undergone further morphological differentiation, resulting in differences in body size, shape, or both. Distinguishing between changes in size and shape is not trivial. Traditional approaches based on allometry reduce complex 3D shapes into simple linear, areal, or volume metrics; modern approaches using geometric morphometrics typically rely on landmarks, introducing observer bias and a trade-off between effort and accuracy. Here, we use a landmark-free method based on large deformation diffeomorphic metric mapping (LDDMM) to assess the co-variation of size and 3D shape in the mandibles and head capsules of Atta vollenweideri leaf-cutter ants, a species exhibiting extreme worker size-variation. Body mass varied by more than two orders of magnitude, but a shape atlas created via LDDMM on μ-CT-derived 3D mesh files revealed only two distinct head capsule and mandibles shapes-one for the minims (body mass < 1 mg) and one for all other workers. We discuss the functional significance of the identified 3D shape variation, and its implications for the evolution of extreme polymorphism in Atta.

New records of herbivory of Leucothyreus MacLeay, 1819 (Coleoptera: Scarabaeidae: Geniatini) on Cecropia Loefl. (Urticaceae)

Species in the genus Cecropia Loefl. (Urticaceae) are important food sources for a handful of species belonging to the insect orders Orthoptera (grasshoppers), Lepidoptera (caterpillars), Hymenoptera (leafcutter ants), and Coleoptera (beetles). Among the leaf chafer beetles, specimens of the scarab genus Leucothyreus MacLeay, 1819 (Scarabaeidae: Geniatini) have been barely recorded as defoliators of Cecropia spp., and information about the identity of the involved plant and beetle species is scarce and imprecise. The present paper records for the first time the incidence of two species of Leucothyreus on four species of Cecropia in Central Amazon (Brazil), with short behavioral notes regarding their feeding habits.

Unearthing a Cryptic Biosynthetic Gene Cluster for the Piperazic Acid-Bearing Depsipeptide Diperamycin in the Ant-Dweller Streptomyces sp. CS113.

Piperazic acid is a cyclic nonproteinogenic amino acid that contains a hydrazine N-N bond formed by a piperazate synthase (KtzT-like). This amino acid, found in bioactive natural products synthesized by non-ribosomal peptide synthetases (NRPSs), confers conformational constraint to peptides, an important feature for their biological activities. Genome mining of Streptomyces strains has been revealed as a strategy to identify biosynthetic gene clusters (BGCs) for potentially active compounds. Moreover, the isolation of new strains from underexplored habitats or associated with other organisms has allowed to uncover new BGCs for unknown compounds. The in-house "Carlos Sialer (CS)" strain collection consists of seventy-one Streptomyces strains isolated from the cuticle of leaf-cutting ants of the tribe Attini. Genomes from twelve of these strains have been sequenced and mined using bioinformatics tools, highlighting their potential to encode secondary metabolites. In this work, we have screened in silico those genomes, using KtzT as a hook to identify BGCs encoding piperazic acid-containing compounds. This resulted in uncovering the new BGC dpn in Streptomyces sp. CS113, which encodes the biosynthesis of the hybrid polyketide-depsipeptide diperamycin. Analysis of the diperamycin polyketide synthase (PKS) and NRPS reveals their functional similarity to those from the aurantimycin A biosynthetic pathway. Experimental proof linking the dpn BGC to its encoded compound was achieved by determining the growth conditions for the expression of the cluster and by inactivating the NRPS encoding gene dpnS2 and the piperazate synthase gene dpnZ. The identity of diperamycin was confirmed by High-Resolution Mass Spectrometry (HRMS) and Nuclear Magnetic Resonance (NMR) and by analysis of the domain composition of modules from the DpnP PKS and DpnS NRPS. The identification of the dpn BGC expands the number of BGCs that have been confirmed to encode the relatively scarcely represented BGCs for depsipeptides of the azinothricin family of compounds and will facilitate the generation of new-to-nature analogues by combinatorial biosynthesis.

Chemical analysis and hydroalcoholic extract activity of ferns on the mutualist fungus of leafcutter ants

Abstract Leafcutter ants are among the most important agricultural and forest pests in the Neotropical region, given that they use plant matter as substrate for the growth of their mutualist fungus Leucoagaricus gongylophorus. Plant-based insecticides and fungicides have shown potential for controlling these ants. The present study assessed the hydroalcoholic extract activity of four fern fronds (dry and rainy periods) on the mutualist fungus of leafcutter ants. Fungal mycelium suspensions were seeded on the surface of tubes containing fern extracts at a concentration of 5 mg/mL and 100 μg/mL. The chemical profile of the extracts was analyzed by thin layer chromatography (TLC). Extracts (dry period) at a concentration of 5 mg/mL inhibited the growth of the fungus: Macrothelypteris torresiana and Dicksonia sellowiana (less than 20%), Niphidium crassifolium (approximately 40%), Parapolystichum effusum extract (100%). None of the extracts (dry and rainy periods) inhibited fungal growth at a concentration of 100 μg/mL. The chemical profile analysis of the extracts indicated the presence of beta-sitosterol, friedelinol, rutin, and kaempferol. The crude extracts of P. effusum and N. crassifolium were the most promising in future formulations of antifungal products. Thus, ferns are potential plants in the search for environmentally-friendly substances for sustainable agriculture.

Sequencing, assembly, and genomic annotation of Leucoagaricus gongylophorus LEU18496, a dikarya mutualistic species.

The basidiomycete fungus Leucoagaricus gongylophorus is able to grow in the fungus garden of leaf-cutter ants. This mutualistic interaction has driven the evolutionary adaptation of L. gongylophorus, shaping its metabolism to produce enzymes adept at lignocellulosic biomass degradation. In this study, we undertook the comprehensive sequencing, assembly, and functional annotation of the genome of L. gongylophorus strain LEU18496, mutualistic fungus of the Atta mexicana. Our genomic analyses revealed a distinctive bimodal nature to the genome: a predominant region characterized by AT enrichment and low genetic density, alongside a smaller region exhibiting higher GC content and higher genetic density. The presence of transposable elements (TEs) within the AT-enriched region suggests genomic compartmentalization, facilitating differential evolutionary rates. With a gene count of 6748, the assembled genome of L. gongylophorus LEU18496 surpasses previous reports for this fungal species. Inspection of genes associated with central metabolism unveiled a remarkable abundance of carbohydrate-active enzymes (CAZymes) and fungal oxidative lignin enzymes (FOLymes), underscoring their pivotal roles in the life cycle of this fungus.

Action mode of fipronil and sulfluramid in baits on Acromyrmex crassispinus (Forel, 1909) (Hymenoptera: Formicidae) in laboratory conditions

The leaf-cutting ants (LCAs) of the genus Atta Fabricius, 1804 and Acromyrmex Mayr, 1865 (Hymenoptera: Formicidae) are major pests in forest plantations, agriculture and livestock. Toxic baits with the active ingredients fipronil and sulfluramid are the main method to manage these insects. The internal hygiene of the ant colony needs to be considered to carry out chemical control of LCA. The baits must act as a true ‘Trojan horse’ deceiving the toxic action during the moment of transport. The objective was to evaluate fipronil and sulfluramid in toxic baits against Acromyrmex crassispinus (Forel, 1909) (Hymenoptera: Formicidae) in the laboratory. The action was observed in the first hours after application. The pick-up of the bait with fipronil was more heterogeneous and more random than that with the sulfluramid. Individuals of A. crassispinus stopped cutting leaves after four and seven days after application (DAA) of fipronil and sulfluramid baits, respectively. The foraging activity tended to zero over time with the sulfluramid bait, but a low carry of leaves was observed on the 11th DAA with the fipronil bait. The fipronil and sulfluramid baits, in laboratory conditions, were toxic and efficient to the ant A. crassispinus. The lethal action of fipronil was faster, an undesired aspect in the management of social insects. A control method that simulates the mythical ‘Trojan horse’ on LCAs nests is desirable.

Atta cephalotes (Hymenoptera: Myrmicinae) is colonizing urban areas in Cali, Colombia

Numerous studies have examined the effect of invasive species on biodiversity in urban environments, however, few of them have investigated the role of native species while turning into invasive pests. In Colombia, Atta cephalotes, a native leaf-cutting ant (LCA), has responded successfully to the conversion of natural ecosystems to agricultural-rural environments and, most recently, to residential and urban development. In this study, we illustrate the incidence and distribution of this native ant species in an environment where animal life must face urban disturbs in the physical environment, resource availability, and ecosystem processes associated with human urbanization in Cali, the third most important city in Colombia. For this, A. cephalotes nests were georeferenced in public green areas located in 12 communes across the city of Cali, southern Colombia. Vegetation and soil cover, urban settings, foraging trails and plants foraged by the ants were recorded. A. cephalotes nests were present in all green areas and, even in human dwellings; the ants harvested both native and introduced plant species. Despite being well adapted to strongly modified urban environments, this ant species appears to be dependent on human-subsidized resources. Given the wide distribution of leaf-cutting ants in Latin America, it is plausible to expect that similar processes are underway in other countries where these ants are found. Hence, this study also proposes to alert the academic and social communities to direct future research towards evaluating both the responses and impacts of these ants in relation to changes in the urban landscape.

Fungal Cultivars of Higher Attine Ants Promote Escovopsis Chemotropism.

In varied environments, microorganisms search for partners or nutritional resources using chemical signals. Microbes are drawn (chemotaxis) or grow directionally (chemotropism) towards the chemical source, enabling them to establish and maintain symbiosis. The hypocrealean fungi Escovopsis enhance their growth towards the basidiomycete fungus Leucoagaricus gongylophorus, which is cultivated by leaf-cutting attine ants for food. Although directional growth is well documented in this symbiosis, it is unclear whether non-volatile or volatile organic compounds participate in the interaction between cultivar and Escovopsis, and which specific chemical compounds might attract and induce chemotropism. In this study, we examined the growth responses of Escovopsis isolates to non-volatile and volatile organic compounds produced by fungal cultivars of higher attine ants. We also isolated and identified molecules released by the ant-cultivar and assessed the chemotropism of Escovopsis towards them. Our results indicate that the growth of Escovopsis is stimulated in the presence of both non-volatile and volatile compounds from fungal cultivars. We also identified three isomeric diketopiperazines molecules from crude extracts of the ant cultivar, suggesting that these might play a role in Escovopsis chemotropism. Our findings provide insights into the complex chemical interactions that govern the association between Escovopsis and fungal cultivars.

Ecología de la fauna chaqueña. Una revisión.

The present status of knowledge about the Chaco fauna is reviewed. The main points considered inelude: The environment. Regional división. The fauna: mammals, birds, reptiles, anurans and invertebrates. Pattems of species diversity. Adaptations of the Chaco animáis. Key processes. The following relevant processes are considered in detail: edaphic inñuence of ants, termites and mammals; decomposers and reducers; pattems of herbivory, particularly the importance of leaf-cutting ants as primary consumers; and the impact of human activity on the Chaco fauna.

The Design and Experimental Validation of a Biomimetic Stubble-Cutting Device Inspired by a Leaf-Cutting Ant's Mandibles.

Under the conditions of conservation tillage, the existence of the root-soil complex greatly increases the resistance and energy consumption of stubble-cutting blades, especially in Northeast China. In this research, the corn root-soil complex in Northeast China was selected as the research object. Based on the multi-toothed structure of the leaf-cutting ant's mandibles and the unique bite mode of its mandibles on leaves, a gear-tooth, double-disk, bionic stubble-cutting device (BSCD) was developed by using a combination of power cutting and passive cutting. The effects of rotary speed, tillage depth, and forward speed on the torque and power of the BSCD were analyzed using orthogonal tests, and the results showed that all of the factors had a large influence on the torque and power, in the order of tillage depth > rotary speed > forward speed. The performance of the BSCD and the traditional power straight blade (TPSB) was explored using comparative tests. It was found that the optimal stubble-cutting rate of the BSCD was 97.4%. Compared with the TPSB, the torque of the BSCD was reduced by 15.2-16.4%, and the power was reduced by 9.2-11.3%. The excellent performance of the BSCD was due to the multi-toothed structure of the cutting edge and the cutting mode.

Leaf-cutter ants - mycorrhizal fungi: observations and research questions from an unexpected mutualism.

Leaf-cutter ants (LCAs) are widely distributed and alter the physical and biotic architecture above and below ground. In neotropical rainforests, they create aboveground and belowground disturbance gaps that facilitate oxygen and carbon dioxide exchange. Within the hyperdiverse neotropical rainforests, arbuscular mycorrhizal (AM) fungi occupy nearly all of the forest floor. Nearly every cubic centimeter of soil contains a network of hyphae of Glomeromycotina, fungi that form arbuscular mycorrhizae. Our broad question is as follows: how can alternative mycorrhizae, which are-especially ectomycorrhizae-essential for the survival of some plant species, become established? Specifically, is there an ant-mycorrhizal fungus interaction that facilitates their establishment in these hyperdiverse ecosystems? In one lowland Costa Rican rainforest, nests of the LCA Atta cephalotes cover approximately 1.2% of the land surface that is broadly scattered throughout the forest. On sequencing the DNA from soil organisms, we found the inocula of many AM fungi in their nests, but the nests also contained the inocula of ectomycorrhizal, orchid mycorrhizal, and ericoid mycorrhizal fungi, including Scleroderma sinnamariense, a fungus critical to Gnetum leyboldii, an obligate ectomycorrhizal plant. When the nests were abandoned, new root growth into the nest offered opportunities for new mycorrhizal associations to develop. Thus, the patches created by LCAs appear to be crucial sites for the establishment and survival of shifting mycorrhizal plant-fungal associations, in turn facilitating the high diversity of these communities. A better understanding of the interactions of organisms, including cross-kingdom and ant-mycorrhizal fungal interactions, would improve our understanding of how these ecosystems might tolerate environmental change.

Collaborative Use of Sensor Networks and Cyberinfrastructure to Understand Complex Ecosystem Interactions in a Tropical Rainforest: Challenges and Lessons Learned.

Collaborations between ecosystem ecologists and engineers have led to impressive progress in developing complex models of biogeochemical fluxes in response to global climate change. Ecology and engineering iteratively inform and transform each other in these efforts. Nested data streams from local sources, adjacent networks, and remote sensing sources together magnify the capacity of ecosystem ecologists to observe systems in near real-time and address questions at temporal and spatial scales that were previously unobtainable. We describe our research experiences working in a Costa Rican rainforest ecosystem with the challenges presented by constant high humidity, 4300 mm of annual rainfall, flooding, small invertebrates entering the tiniest openings, stinging insects, and venomous snakes. Over the past two decades, we faced multiple challenges and learned from our mistakes to develop a broad program of ecosystem research at multiple levels of integration. This program involved integrated networks of diverse sensors on a series of canopy towers linked to multiple belowground soil sensor arrays that could transport sensor data streams from the forest directly to an off-site location via a fiber optic cable. In our commentary, we highlight three components of our work: (1) the eddy flux measurements using canopy towers; (2) the soil sensor arrays for measuring the spatial and temporal patterns of CO2 and O2 fluxes at the soil-atmosphere interface; and (3) focused investigations of the ecosystem impact of leaf-cutter ants as "ecosystem engineers" on carbon fluxes.

Three-dimensional kinematics of leaf-cutter ant mandibles: not all dicondylic joints are simple hinges.

Insects use their mandibles for a variety of tasks, including food processing, material transport, nest building, brood care, and fighting. Despite this functional diversity, mandible motion is typically thought to be constrained to rotation about a single fixed axis. Here, we conduct a direct quantitative test of this 'hinge joint hypothesis' in a species that uses its mandibles for a wide range of tasks: Atta vollenweideri leaf-cutter ants. Mandible movements from live restrained ants were reconstructed in three dimensions using a multi-camera rig. Rigid body kinematic analyses revealed strong evidence that mandible movement occupies a kinematic space that requires more than one rotational degree of freedom: at large opening angles, mandible motion is dominated by yaw. But at small opening angles, mandibles both yaw and pitch. The combination of yaw and pitch allows mandibles to 'criss-cross': either mandible can be on top when mandibles are closed. We observed criss-crossing in freely cutting ants, suggesting that it is functionally important. Combined with recent reports on the diversity of joint articulations in other insects, our results show that insect mandible kinematics are more diverse than traditionally assumed, and thus worthy of further detailed investigation. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

Interspecific Repellent Effect of Hydroalcoholic Solution of Nest Refuse from Two Leaf-cutter Ant Species

Leaf-cutting ants manage their waste continuously to avoid risks of colony contamination. The presence of residues or their odor near foraging areas is enough for ants to stop attacking plant tissues. However, to date, no study has demonstrated an interspecific effect of nest waste on the deterrence of leaf-cutting ants. Here, we tested whether a hydroalcoholic extract of nest refuse (NR) of the leaf-cutting ants Acromyrmex balzani Emery, 1890 and Atta opaciceps Borgmeier (Hymenoptera: Formicidae, Attini) causes an interspecific deterrent effect. Field colonies of Ac. balzani (n = 30) and A. opaciceps (n = 36) were used. For each colony, we offered baits made with plastic straws covered by citrus pulp and sprayed with a hydroalcoholic solution of 20% (vol/vol) alcohol/water (Control) or an extract of 20% (vol/vol) of NR from Ac. balzani and/or A. opaciceps. Over 20-30 minutes we recorded the amount of baits removed and data were compared through survival analysis and Linear Mixed Effect (LME) model. Ants avoided collecting baits sprayed with NR resulting in less than 20% of these baits being carried to the nest versus 80% of control baits. The deterrence was both intra and interspecific, considering that the response was similar for baits from both species. Such results reinforce the premise that the presence of nest refuse alters the foraging behavior of ants and paves the way for new studies that can verify its effectiveness in reducing foliar consumption on a larger spatial scale.

Reciprocal nutritional provisioning between leafcutter ants and their fungal cultivar mediates performance of symbiotic farming systems

Abstract Optimized food acquisition is challenging because foraged diet items are chemically complex and often nutritionally imbalanced. These challenges are likely magnified when foraged foods are used to provision others (e.g. offspring, nestmates, symbionts) with different nutritional requirements. We used a theoretical framework of nutritional niches to study these provisioning challenges in leafcutter ants that cultivate a fungal symbiont with nutrients derived from freshly foraged plant fragments. While the leaf‐cutting behaviours of free‐ranging foragers are well studied, little is known about how colonies use these plant fragments to produce their fungal crop within underground nest chambers. For instance, gardener ants are known to convert vegetation into a nutritional mulch that they plant on the fungus garden. However, it remains poorly understood how the ants use this mulch to target the specific nutritional needs of their fungal crop, and whether the cultivar signals if provisioned mulch meets its nutritional needs. Towards answers, we performed three experiments to assess the precision and specificity of nutritional regulation in farming systems of the Panamanian leafcutter ant Acromyrmex echinatior. A laboratory feeding experiment with nutritionally defined diets showed that ant farmers collect a specific intake target for protein and carbohydrates and then linked strict protein regulation by foragers to the cultivar's fundamental niche for protein. An in vitro experiment with the fungal cultivar in isolation did not detect a signal of protein stress that could be used by the ants to regulate their provisioning behaviour, but it did identify an elevated fatty acid that may reinforce optimal nutritional provisioning if detected by gardening ants. A feeding experiment with isotopically labelled diets then revealed nutrient‐specific and caste‐specific allocation timelines, with nitrogen being assimilated into the cultivar's nutritional rewards before being exclusively consumed by developing brood. In turn, these combined results help resolve the integrated behaviours that give rise to resilient leafcutter farming productivity. We further show how nutritional niches can help disentangle reciprocal provisioning dynamics between symbionts as well as the nutritional transactions that more generally mediate symbiotic stability (e.g. sanctioning, screening, policing). Read the free Plain Language Summary for this article on the Journal blog.

Correction to: 'Developmental biomechanics and age polyethism in leaf-cutter ants' (2023) by Püffel et al.

Correction to: 'Developmental biomechanics and age polyethism in leaf-cutter ants' (2023) by Püffel et al.

Evidence that the domesticated fungus Leucoagaricus gongylophorus recycles its cytoplasmic contents as nutritional rewards to feed its leafcutter ant farmers

Leafcutter ants farm a fungal cultivar (Leucoagaricus gongylophorus) that converts inedible vegetation into food that sustains colonies with up to millions of workers. Analogous to edible fruits of crops domesticated by humans, L. gongylophorus has evolved specialized nutritional rewards—swollen hyphal cells called gongylidia that package metabolites and are consumed by ant farmers. Yet, little is known about how gongylidia form, and thus how fungal physiology and ant provisioning collectively govern farming performance. We explored the process of gongylidium formation using advanced microscopy to image the cultivar at scales of nanometers, and both in vitro experiments and in silico analyses to examine the mechanisms of gongylidia formation when isolated from ant farmers. We first used transmission electron, fluorescence, and confocal microscopy imaging to see inside hyphal cells. This imaging showed that the cultivar uses a process called autophagy to recycle its own cellular material (e.g. cytosol, mitochondria) and then shuttles the resulting metabolites into a vacuole whose continual expansion displaces other organelles and causes the gongylidium cell’s bulging bulb-like appearance. We next used scanning electron microscopy and light microscopy to link this intracellular rearrangement to the external branching patterns of gongylidium cells as they clump together into edible bundles called staphyla. We next confirmed that autophagy plays a critical role in gongylidium formation both: (1) in vitro as gongylidium suppression occurred when isolated fungal cultures were grown on media with autophagy inhibitors, and (2) in silico as differential transcript expression (RNA-seq) analyses showed upregulation of multiple autophagy gene isoforms in gongylidia relative to undifferentiated hyphae. While autophagy is a ubiquitous and often highly derived process across the tree of life, our study reveals a new role for autophagy as a mechanism of functional integration between ant farmers and their fungal crop, and potentially as a signifier of higher-level homeostasis between uniquely life-time committed ectosymbionts.

The Influence of Selected Insecticides on the Oxidative Response of Atta sexdens (Myrmicinae, Attini) Workers

Reactive oxygen species (ROS) are generated as products of normal cellular metabolic activities; however, the use of pesticides to control leafcutter ants leads to unbalanced ROS production. We evaluated the effects of two insecticides (fipronil, sulfluramid) and metallic insecticide complex (magnesium complex [Mg(hesp)2(phen)] (1)) on the superoxide dismutase (SOD), glutathione (GSH) and the overall antioxidant capacity using two different methodologies: total radical-trapping potential (TRAP) and oxygen radical absorbance capacity (ORAC). Media workers of Atta sexdens (C. Linnaeus) were exposed to the insecticides for 24 h, 48 h, 72 h and 96 h before their fat bodies were dissected for analysis. The results showed that although the sulfluramid may cause the production of ROS, its slow action in the organism does not lead to oxidative stress. There is a rise in oxidative stress in workers of leafcutter ants treated with fipronil because SOD significantly increased when compared to the control group. On the other hand, Mg1-complex suppressed both GSH and SOD, indicating that the immune system may be affected by Mg1-complex, which has a delayed activity ideal for its use in chemical pest control. Both TRAP and ORAC evaluated total antioxidant capacities; however, ORAC proved to be a more sensitive method. In conclusion, the Mg1-complex is a new compound that should be further investigated as a potential replacement for fipronil and sulfluramid in pest control.