Peptide toxins that target vertebrate voltage-gated sodium channels underly the painful stings of harvester ants.

Harvester ants (genus Pogonomyrmex) are renowned for their stings which cause intense, long-lasting pain, and other neurotoxic symptoms in vertebrates. Here, we show that harvester ant venoms are relatively simple and composed largely of peptide toxins. One class of peptides is primarily responsible for the long-lasting local pain of envenomation via activation of peripheral sensory neurons. These hydrophobic, cysteine-free peptides potently modulate mammalian voltage-gated sodium (NaV) channels, reducing the voltage threshold for activation and inhibiting channel inactivation. These toxins appear to have evolved specifically to deter vertebrates.

Interaction of red crabs with yellow crazy ants during migration on Christmas Island.

Invasive species have had a profound impact on ecosystems all over the world. Their presence can lead to fundamental changes in the biodiversity of a given ecosystem as well as the extinction of native species. In particular, this work looks at the effect on the Gecarcoidea natalis (Red Crab) population on Christmas Island due to the presence of vast arrays of supercolonies containing Anoplolepis gracilipes (Yellow Crazy Ant). We primarily study the inter-species interaction occurring during the crab migration to the island coast. We propose a microscopic model for the dynamics of the crabs and ants with the goal of increasing crab survival. Through analysis of the model, we investigate a range of potential preventative measures that could be taken to preserve the native crab population dependent on their locations. The main result of this work is that by considering the locations of ant supercolonies incorporated into Monte Carlo simulations of the model, we can identify the order that the supercolonies need to be removed to provide the greatest chance at survival for the crabs per migration cycle.

Zombie-Ant Fungi Emerged from Non-manipulating, Beetle-Infecting Ancestors.

The manipulation of animal behavior by parasitic organisms is one of the most complex adaptations to have arisen via natural selection. Among the most impressive examples of behavioral manipulation are the zombie-ant fungi [1]. In this association, ants are controlled to leave the colony and perform a stereotyped death grip behavior, where they bite onto vegetation over foraging trails, before being killed for the post mortem fungal growth. Manipulation functions to provide a platform outside the nest, from which fungal parasites actively shoot out spores, targeting foraging ants because within colony transmission is prevented by strong social immunity exhibited by social insect societies [2, 3]. It is not clear how such complex examples of host manipulation arose. To address this, we performed a broad-scale phylogenetic reconstruction of the order Hypocreales, to which the zombie-ant fungi, Ophiocordyceps, belong. In order to understand the patterns of host association and host switching along the evolution of Ophiocordyceps, we performed ancestral character state reconstruction analysis. We found that zombie-ant fungi likely arose from an ancestor that infected beetle larvae residing in soil or decaying wood, similar to extant beetle-infecting Ophiocordyceps species. Surprisingly, the jump led to an extensive species radiation observed after the development of behavioral manipulation. We suggest that the jump from solitary beetle larva to ants within a colony exposed the fungus to the robust social immunity of ant societies.

Unconscious Woman in Shock and Covered with Ants Pulled from an Abandoned Automobile.

BACKGROUND: A middle-aged woman was taken from an abandoned automobile unconscious and covered with ants in Tucson, Arizona. When hospitalized in July 2018, she had an extensive papular-pustular skin eruption on her abdomen and thigh and disseminated intravascular coagulation. She was stung innumerable times by native golden fire ants (Solenopsis aurea) while sleeping in the vehicle. The large amount of venom injected by stings into this individual may have triggered dissemnated intravascualar coagulation because the venom contains powerful hemolytic factors. METHODS: The patient history is presented and ants were captured and identified. RESULTS: Clinical findings of fire ant stings are presented and the importance of recognizing the distinctive skin lesions that occur is emphasized. Stings of the red imported fire ant, Solenopsis invicta, and the black imported fire ant, Solenopsis richteri, cause skin lesions recognized by physicians and victims alike in the southern and southeastern United States. Native fire ant stings are documented much less often. However, there is significant cross-reactivity among the venoms of Solenopsis species. CONCLUSION: It is important for clinicians to recognize the characteristic skin lesions of fire ant envenomation as fire ant populations are expanding and they sting millions of people each year.

Ant Bites Conjunctival Tissue: The ABCs of Removing an Ocular Ant Foreign Body.

BACKGROUND: A variety of insect-related ocular injuries have been reported in the literature. However, no reports have been published documenting injuries resulting from exposure of the ocular surface to ants. This is surprising, given the relatively ubiquitous presence of ants. This is the first known case report to describe various techniques utilized in the removal of ants from the ocular surface. CASE REPORT: This case report details the presentation of a distressed 24-year-old woman who presented to the Emergency Department with an ocular foreign body associated with pain and increased lacrimation. She was identified to have an ant adherent to her conjunctiva. Various techniques of removal were performed, with the ant finally removed without any trauma to underlying tissues. CONCLUSION: This is the first case report to detail various techniques utilized in the removal of ants from the ocular surface, and discusses salient features that treating physicians should be aware of in managing patients presenting with ant bites.

A Visual Guide for Studying Behavioral Defenses to Pathogen Attacks in Leaf-Cutting Ants.

The complex lifestyle, evolutionary history of advanced cooperation, and disease defenses of leaf-cutting ants are well studied. Although numerous studies have described the behaviors connected with disease defense, and the associated use of chemicals and antimicrobials, no common visual reference has been made. The main aim of this study was to record short clips of behaviors involved in disease defense, both prophylactically and directly targeted towards an antagonist of the colony following infection. To do so we used an infection experiment, with sub-colonies of the leaf-cutting ant species Acromyrmex echinatior, and the most significant known pathogenic threat to the ants' fungal crop (Leucoagaricus gongylophorus), a specialized pathogenic fungus in the genus Escovopsis. We filmed and compared infected and uninfected colonies, at both early and more advanced stages of infection. We quantified key defensive behaviors across treatments and show that the behavioral response to pathogen attack likely varies between different castes of worker ants, and between early and late detection of a threat. Based on these recordings we have made a library of behavioral clips, accompanied by definitions of the main individual defensive behaviors. We anticipate that such a guide can provide a common frame of reference for other researchers working in this field, to recognize and study these behaviors, and also provide greater scope for comparing different studies to ultimately help better understand the role these behaviors play in disease defense.

Combined Peptidomic and Proteomic Analysis of Electrically Stimulated and Manually Dissected Venom from the South American Bullet Ant Paraponera clavata.

Ants have evolved venoms rich in peptides and proteins used for predation, defense, and communication. However, they remain extremely understudied due to the minimal amount of venom secreted by each ant. The present study investigated the differences in the proteome and peptidome of the venom from the bullet ant, Paraponera clavata. Venom samples were collected from a single colony either by manual venom gland dissection or by electrical stimulation and were compared using proteomic methods. Venom proteins were separated by 2D-PAGE and identified by nanoLC-ESI-QTOF MS/MS. Venom peptides were initially separated using C18 reversed-phase high-performance liquid chromatography, then analyzed by MALDI-TOF MS. The proteomic analysis revealed numerous proteins that could be assigned a biological function (total 94), mainly as toxins, or roles in cell regulation and transport. This investigation found that ca. 73% of the proteins were common to venoms collected by the two methods. The peptidomic analysis revealed a large number of peptides (total 309) but with <20% shared by the two collection methods. There was also a marked difference between venoms obtained by venom gland dissection from different ant colonies. These findings demonstrate the rich composition and variability of P. clavata venom.

Ancestry trumps experience: Transgenerational but not early life stress affects the adult physiological stress response.

Exposure to stressors can affect an organism's physiology and behavior as well as that of its descendants (e.g. through maternal effects, epigenetics, and/or selection). We examined the relative influence of early life vs. transgenerational stress exposure on adult stress physiology in a species that has populations with and without ancestral exposure to an invasive predator. We raised offspring of eastern fence lizards (Sceloporus undulatus) from sites historically invaded (high stress) or uninvaded (low stress) by predatory fire ants (Solenopsis invicta) and determined how this different transgenerational exposure to stress interacted with the effects of early life stress exposure to influence the physiological stress response in adulthood. Offspring from these high- and low-stress populations were exposed weekly to either sub-lethal attack by fire ants (an ecologically relevant stressor), topical treatment with a physiologically-appropriate dose of the stress-relevant hormone, corticosterone (CORT), or a control treatment from 2 to 43weeks of age. Several months after treatments ended, we quantified plasma CORT concentrations at baseline and following restraint, exposure to fire ants, and adrenocorticotropic hormone (ACTH) injection. Exposure to fire ants or CORT during early life did not affect lizard stress physiology in adulthood. However, offspring of lizards from populations that had experienced multiple generations of fire ant-invasion exhibited more robust adult CORT responses to restraint and ACTH-injection compared to offspring from uninvaded populations. Together, these results indicate that transgenerational stress history may be at least as important, if not more important, than early life stress in affecting adult physiological stress responses.

Does the whistling thorn acacia (Acacia drepanolobium) use auditory aposematism to deter mammalian herbivores?

Auditory signaling including aposematism characterizes many terrestrial animals. Auditory aposematism by which certain animals use auditory aposematic signals to fend off enemies is well known for instance in rattlesnakes. Auditory signaling by plants toward animals and other plants is an emerging area of plant biology that still suffers from limited amount of solid data. Here I propose that auditory aposematism operates in the African whistling thorn acacia (Acacia drepanolobium = Vachellia drepanolobium). In this tree, the large and hollow thorn bases whistle when wind blows. This type of aposematism compliments the well-known conspicuous thorn and mutualistic ant based aposematism during day and may operate during night when the conspicuous thorns are invisible.

Evidence that microgynes of Myrmica rubra ants are social parasites that attack old host colonies.

Ant microgynes are miniaturized queen forms found together with normal queens (macrogynes) in species occurring across the ant phylogeny. Their role is not yet fully understood: in some cases, they seem to be nonparasitic alternative reproductive morphs, in others incipient social parasites, and thus potential models for studying the evolution of social parasitism. Whether they are regarded as parasitic or not has traditionally been based on genetic differentiation from syntopic macrogynes and/or the queen/worker ratio of their offspring rather than measuring fitness traits. We confirmed previously reported genetic differentiation between microgynes and macrogynes of Myrmica rubra in a population studied for the first time. Further, we measured virulence and infectivity of M. rubra microgynes in a controlled laboratory experiment. Nests headed only by macrogynes (controls), only by microgynes, and naturally and artificially mixed nests were kept under identical conditions. We found reduction in worker numbers of both naturally and artificially mixed macrogyne/microgyne nests compared with controls, and strong reduction but also surprising variation in fitness of nests headed only by microgynes. Microgyne nests produced workers, males and microgynes. Microgynes did not themselves reproduce in artificially mixed nests, but reproduced most in naturally mixed nests that had lost their macrogyne queen. This, together with higher mortality of field-collected macrogyne queens from naturally infested colonies and greater estimated relative age of macrogyne queens in naturally infected nests, suggests that they preferentially exploit older host colonies. We conclude that M. rubra microgynes are intraspecific social parasites specialized on exploiting old host colonies.

Trichome-derived O-acyl sugars are a first meal for caterpillars that tags them for predation.

Plant glandular trichomes exude secondary metabolites with defensive functions, but these epidermal protuberances are surprisingly the first meal of Lepidopteran herbivores on Nicotiana attenuata. O-acyl sugars, the most abundant metabolite of glandular trichomes, impart a distinct volatile profile to the body and frass of larvae that feed on them. The headspace composition of Manduca sexta larvae is dominated by the branched chain aliphatic acids hydrolyzed from ingested O-acyl sugars, which waxes and wanes rapidly with trichome ingestion. In native habitats a ground-hunting predator, the omnivorous ant Pogonomyrmex rugosus, but not the big-eyed bug Geocoris spp., use these volatile aliphatic acids to locate their prey.

Indirect effects of tending ants on holm oak volatiles and acorn quality.

The indirect effect of ants on plants through their mutualism with honeydew-producing insects has been extensively investigated. Honeydew-producing insects that are tended by ants impose a cost on plant fitness and health by reducing seed production and/or plant growth. This cost is associated with sap intake and virus transmissions but may be overcompesated by tending ants if they deter or prey on hebivorous insects. The balance between cost and benefits depends on the tending ant species. In this study we report other indirect effects on plants of the mutualism between aphids and ants. We have found that two Lasius ant species, one native and the other invasive, may change the composition of volatile organic compounds (VOCs) of the holm oak (Quercus ilex) blend when they tend the aphid Lachnus roboris. The aphid regulation of its feeding and honeydew production according to the ant demands was proposed as a plausible mechanism that triggers changes in VOCs. Additionally, we now report here that aphid feeding, which is located most of the time on acorns cap or petiole, significantly increased the relative content of linolenic acid in acorns from holm oak colonized by the invasive ant. This acid is involved in the response of plants to insect herbivory as a precursor or jasmonic acid. No effect was found on acorn production, germination or seedlings quality. These results suggest that tending-ants may trigger the physiological response of holm oaks involved in plant resistance toward aphid herbivory and this response is ant species dependant.

My journey to the ants.

In this paper, I review the strange, unplanned and unexpected journey I have had with Solenopsis invicta, the imported fire ant. Through serendipity, good fortune and repeated invenomation, I have come to count as collaborators a number of entomologists, toxicologists, allergists and immunologists who have guided me on this journey to the ants. We now understand the mechanisms for the cutaneous reactions experienced by 50% of the exposed population stung per year, as well as the immunologic and toxicologic properties of the ants unique venom. Allergen immunotherapy to fire ant extracts has been demonstrated to protect patients from repeat anaphylaxis. Methods have been developed to prevent and treat massive sting attacks on frail elders, including those in residential and medical facilities. The potential beneficial effects of venom components are under investigation. And yes, the journey and the stings continue.

Range expansion drives dispersal evolution in an equatorial three-species symbiosis.

BACKGROUND: Recurrent climatic oscillations have produced dramatic changes in species distributions. This process has been proposed to be a major evolutionary force, shaping many life history traits of species, and to govern global patterns of biodiversity at different scales. During range expansions selection may favor the evolution of higher dispersal, and symbiotic interactions may be affected. It has been argued that a weakness of climate fluctuation-driven range dynamics at equatorial latitudes has facilitated the persistence there of more specialized species and interactions. However, how much the biology and ecology of species is changed by range dynamics has seldom been investigated, particularly in equatorial regions. METHODOLOGY/PRINCIPAL FINDINGS: We studied a three-species symbiosis endemic to coastal equatorial rainforests in Cameroon, where the impact of range dynamics is supposed to be limited, comprised of two species-specific obligate mutualists--an ant-plant and its protective ant--and a species-specific ant parasite of this mutualism. We combined analyses of within-species genetic diversity and of phenotypic variation in a transect at the southern range limit of this ant-plant system. All three species present congruent genetic signatures of recent gradual southward expansion, a result compatible with available regional paleoclimatic data. As predicted, this expansion has been accompanied by the evolution of more dispersive traits in the two ant species. In contrast, we detected no evidence of change in lifetime reproductive strategy in the tree, nor in its investment in food resources provided to its symbiotic ants. CONCLUSIONS/SIGNIFICANCE: Despite the decreasing investment in protective workers and the increasing investment in dispersing females by both the mutualistic and the parasitic ant species, there was no evidence of destabilization of the symbiosis at the colonization front. To our knowledge, we provide here the first evidence at equatorial latitudes that biological traits associated with dispersal are affected by the range expansion dynamics of a set of interacting species.

Lesiones post mortales por fauna cadavérica. La acción de las hormigas sobre el cadáver / Post-mortal injuries by cadaveric fauna. The action of the ants on human corpses

Los animales pueden actuar como predadores delos restos humanos y las lesiones postmortales que infligenen los cadáveres pueden dar lugar a errores de interpretaciónde los hallazgos en las autopsias forenses.Entre la fauna cadavérica, las hormigas constituyen uncaso excepcional al ser los únicos insectos que puedeniniciar su actividad predadora antes de instaurarse laputrefacción. Las hormigas suelen producir lesiones quepor su asiento y morfología resultan típicas. Se presentaun caso en el que se evidencia la presencia de lesiones demorfología típica por la acción lesiva postmortal de hormigas,pero con una extensión y localización inhabituales

Post-mortem animal predation can lead to errorswhen interpreting forensic autopsy findings. Ants are theonly insects that can attack human corpses after deathand before decomposition process starts. Ants producepost mortal injuries in the skin that have a distinctlocation and morphology. We present a forensic case inwhich post mortal injuries produced by ants in a humancorpse had a typical morphology; however theirlocation and extension were unusual

Bactérias veiculadas por formigas em ambiente hospitalar / Bacteria carried by ants in a hospital environment

As infecções hospitalares constituem um dos maiores problemas em hospitais públicos e privados em todo o mundo. A prevalência dessas infecções é grande, gerando aumento da mortalidade e gastos, em geral. Objetivos: Este trabalho teve como objetivo avaliar as bactérias veiculadas por formigas em ambiente hospitalar, bem como a resistência aos antibióticos das cepas encontradas nestes insetos. Material e métodos: Foram coletadas, de forma asséptica, formigas alocadas em diversos setores do Hospital das Clínicas (Unidade I e II) e do Hemocentro da Faculdade de Medicina de Marília (São Paulo, Brasil), sendo também coletada uma amostra domiciliar. A metodologia envolveu cultura em laboratório e realização de antibiograma. Resultados: Em todas as amostras foram isolados bacilos gram-positivos. Bacilos gram-negativos foram isolados em 62,5% dos casos, encontrando-se Klebsiella pneumoniae, Klebsiella ozaenae e Escherichia coli. Dentre os locais avaliados, destacou-se o berçário, de onde se isolaram cepas de Klebsiella pneumoniae multirresistentes. Conclusão: Pôde ser encontrado um número de bactérias em formigas, ocorrendo cepas multirresistentes, classicamente associadas a infecções hospitalares. Entretanto, estudos ainda são necessários para estabelecer uma possível correlação.

Hospital infections are one of the most important problems in public and private hospitals in the world. The prevalence of hospital infections is considerable and may promote mortality, besides raising expenses. Objective: The present study evaluated the bacteria transported by ants in hospital environments and the antimicrobial resistance of species isolated from these insects. Material and methods: Samples of ants were aseptically collected in different sectors of Hospital de Clínicas I and II and Hemocentro of Faculdade de Medicina de Marília (São Paulo, Brazil). We also collected samples of ants from a household. The methodology has involved evaluation by laboratorial culture and antibiogram. Results: In all samples gram positive bacilli were isolated. Gram negative bacilli were isolated in 62.5% of the samples, being Klebsiella pneumoniae, Klebsiella ozaenae and Escherichia coli. Considering the sectors evaluated, the ward nursing was an important place, because multiresistant Klebsiella pneumoniae were isolated there. Conclusion: Ants in hospital can carry multiresistant bacteria and these strains can be related with hospital infections, but other studies are required to investigate this possible correlation.

Interaction intimacy affects structure and coevolutionary dynamics in mutualistic networks.

The structure of mutualistic networks provides clues to processes shaping biodiversity [1-10]. Among them, interaction intimacy, the degree of biological association between partners, leads to differences in specialization patterns [4, 11] and might affect network organization [12]. Here, we investigated potential consequences of interaction intimacy for the structure and coevolution of mutualistic networks. From observed processes of selection on mutualistic interactions, it is expected that symbiotic interactions (high-interaction intimacy) will form species-poor networks characterized by compartmentalization [12, 13], whereas nonsymbiotic interactions (low intimacy) will lead to species-rich, nested networks in which there is a core of generalists and specialists often interact with generalists [3, 5, 7, 12, 14]. We demonstrated an association between interaction intimacy and structure in 19 ant-plant mutualistic networks. Through numerical simulations, we found that network structure of different forms of mutualism affects evolutionary change in distinct ways. Change in one species affects primarily one mutualistic partner in symbiotic interactions but might affect multiple partners in nonsymbiotic interactions. We hypothesize that coevolution in symbiotic interactions is characterized by frequent reciprocal changes between few partners, but coevolution in nonsymbiotic networks might show rare bursts of changes in which many species respond to evolutionary changes in a single species.

Plant-aphid interactions: molecular and ecological perspectives.

Many aphids are major agricultural pests because of their unparalleled reproductive capacity and their ability to manipulate host plant physiology. Aphid population growth and its impact on plant fitness are strongly influenced by interactions with other organisms, including plant pathogens, endophytes, aphid endosymbionts, predators, parasitoids, ants, and other herbivores. Numerous molecular and genomic resources have recently been developed to identify sources of aphid resistance in plants, as well as potentially novel targets for control in aphids. Moreover, the same model systems that are used to explore direct molecular interactions between plants and aphids can be utilized to study the ecological context in which they occur.

Emergence of the introduced ant Pachycondyla chinensis (Formicidae: Ponerinae) as a public health threat in the southeastern United States.

Pachycondyla chinensis (Emery) (Formicidae: Ponerinae), a species introduced into North America > 70 yr ago, is found throughout Southeast Asia. Stinging of zookeepers by P. chinensis at the Greenville Zoo (Greenville, SC) initiated an investigation of this exotic species and a survey of sting victims. Eighty percent of sting victims experienced local reactions, including swelling < 5 cm in diameter around the sting site, recurring pain, skin redness, and mild-to-severe urticaria. These symptoms lasted 2 h to 5 d. Twelve percent of the sting victims reported minor reactions, including no swelling, localized redness, minor pain sensation at the time of sting, mild urticaria, and symptoms lasting < 1 h. Eight percent of the sting victims reported significant local reactions, including swelling > 5 cm in diameter around the sting site, recurring pain, skin redness, severe urticaria, and symptoms lasting 3-14 d. P. chinensis represents an emerging public health threat throughout its present range in the southeastern United States (i.e., Georgia, North Carolina, South Carolina, and Virginia). Because of reported adverse reactions to stings of P. chinensis, further studies on its ecology and medical and veterinary importance need to be undertaken.

Formigas: análise dos microorganismos carreados no ambiente hospitalar / Ants: analysis of carried microorganisms in hospital environment

O objetivo deste trabalho é avaliar a carga bacteriana carreada por formigas encontradas em um hospital. Foram recolhidas formigas de várias unidades, que foram colocadas para caminhar em placas de ágar sangue. Após, realizou-se a identificação e o antibiograma. Das 18 placas marcadas, 14 (77,77%) apresentaram crescimento microbiano. Acinectobacter sp. (27,77%), Micrococcus sp. (11,11%), Bacillus sp. (11,11%), Staphylococcus Coagulase Negativa (11,11%) e diferentes gêneros de fungos filamentosos característicos de ambiante (16,66%). As formigas encontradas na UTI Neonatal apresentaram ressitência a vários antimicrobianos. Associada à aplicação sistemática de inseticidas, deve-se promover a conscientização da comunidades hospitalar para evitar estes pequenos, mas importantes inimigos.