Fast spread of a fungal parasite in an invasive supercolony

Dissertação de mestrado em Evolução e Biologia Humanas, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.O diagnóstico paleopatológico continua a lidar com o dilema que conecta, paradoxalmente, um alto número de casos de mortalidade infantil e a reduzida variedade de doenças referenciadas como “possíveis” causas da morte: infeções, doenças metabólicas e traumatismos. A presença de porosidade óssea, como única evidência macroscópica frequente em muitos casos arqueológicos infantis, é extremamente alta nas porções cranianas e pós-cranianas e pode atribuir-se à patologia, ao desenvolvimento biológico, e/ou à diagénese. No entanto, a distinção macroscópica da sua origem não é fácil, e a junção intrínseca entre este tipo de doenças, fornece evidências conflituosas que dificultam o diagnóstico diferencial. Com o propósito de desenvolver outras metodologías mais precisas do que a simples observação a olho nu, o objectivo deste estudo é realizar um exame topográfico (cortical) da superfície óssea, para testar a fiabilidade do Microscópio Electrónico de Varrimento (MEV) como ferramenta diagnóstica não destrutiva. A base desta investigação radica na determinação de diferenças entre as manifestações ósseas mencionadas anteriormente, e as possíveis diferenças entre indivíduos de idades diferentes. A amostra compõe-se por 9 esqueletos articulados e um conjunto de fragmentos ósseos, que podem atribuir-se à existência de um total de 29 indivíduos segundo o NMI obtido a partir dos ossos temporais. Estes restos, não adultos, foram exumados da Praça de Armas do castelo da vila Alentejana de Amieira do Tejo (Portugal), e datam dos séculos XIX e XX. Depois da realização da estimativa macroscópica da idade à morte, 70 amostras foram estudadas e fotografadas com um microscópio binocular Leica MD6, e observadas num Microscópio Electrónico de Varimento JEOL JSM-5400 a 20KV no modo de electrões secundários. Para este fim, os restos foram cobertos com uma camada de Carbono num Evaporador de Vácuo JEOL JEE-4X. Apesar de que a idade a morte estimada oscilara entre os 0-6 anos de idade - através das características dentais macroscópicas - foi observado um desfasamento entre o grau de desenvolvimento ósseo, com idades muito mais precoces, e o dentário, com idades mais avançadas. Isto pode estar associado com eventos stressantes durante a vida (p.ex. Malnutrição, condições do meio ambiente, doenças...), sobretudo, naquelas estruturas porosas encontradas para além dos 5-10mm. do extremo do osso. A bibliografía sobre o contexto socioeconómico da região mostra precariedade, insalubridade e uma alta taxa de mortalidade infantil. Este estudo exploratório mostra que é essencial desenvolver novas metodologias que esclareçam a etiologia multifatorial que envolve este tipo de alterações, dado que permite combinar um excelente detalhe, uma boa resolução, simplicidade no emprego, e o pré-requisito de ser não destrutiva. Até a data o controverso estudo que envolve os sinais porosos só tem tido sucesso com evidências patognomónicas. São precisos mais estudos que potenciem a funcionalidade da microscopia de varrimento, sobretudo, se tencionamos encontrar características microscópicas patológicas que permitam depurar o diagnóstico macroscópico. Ao mesmo tempo esta dissertação salienta as consequências do estudo da infância, já que esta fração demográfica supõe o reflexo mais próximo dos parâmetros do meio ambiente e da economia, e permite também inferir sobre restrições culturais, práticas de aleitamento e certos tabus alimentares, características extremamente importantes para a pesquisa populacional antropológica.Paleopathological diagnosis continues to struggle with the quandary that connect, paradoxically, a high number of infancy mortality cases, and the reduced variety of disease referenced as “possible” causes of death: infections, metabolic diseases and trauma. Bone porosity presence, as a single common macroscopic evidence found in many archaeological infant cases, is extremely high in their cranial and post cranial skeleton and may be attributed to pathology, biological development, and/or diagenesis. However, to distinguish those origins macroscopically is not easy, and the intrinsic junction between this kinds of sickness, provide conflicting evidences that makes difficult the differential diagnosis. With the purpose of developing other more precise methodologies than the simple observation with the naked eye, the aim of this study is to perform a topographic (cortical) surface exam, to test the reliability of the Scanning Electronic Microscopy (SEM) as a non-invasive diagnostic tool. The base of this investigation lie in determining differences between the bone manifestations mentioned above and possible differences between different age individuals. The sample consists of 9 single non-adult skeletons and an ossuary settlement of non-adult bone fragments (compound by a total of 29 individuals according to the MNI obtained by temporal bones), recovered inside the castle of Amieira do Tejo villa (Alentejo, Portugal), and dating from the 19th and 20th centuries. After performing the macroscopic age at death estimation, 70 samples were studied and photographed with a Leica MD6 binocular microscope, and selected porous areas were further observed in a JEOL JSM-5400 Scanning Electron Microscopy (SEM) at 20KV in secondary electron mode. For this end, the remains were carbon coated in a JEOL JEE-4X Vacumm Evaporator. Despite the age at death was between 0-6 years old as estimated by the macroscopic study of dental characteristics, a mismatch between bone and teeth development degree was observed, being the first younger thant the second. This, is possibly associate to stressful events during life (e.g. malnutrition, environmental conditions, diseases…), above all, that porosity structure found beyond 5-10mm from the bone end. The bibliography about the socioeconomic context of the region shows precariousness, unhealthiness, and a high infant mortality rate. This exploratory study shows it is essential to develop news methodologies to shed light on the multifactorial aetiology this type of alterations entailed, as they allows to combine an excellent detail, a good resolution, simplicity of operation, and the prerequisite of being nondestructive. At the present moment, the controversial study involving porous signals only have had success with pathognomonic evidences. Further studies that enhance the functionality of the scanning electron microscope are needed, especially if we intend to find pathological microscope features that enable to polish macroscopical diagnosis. At the same time, this dissertation points out the consequences of childhood studies, as this demographic fraction supposes the most closely reflection of environmental and economic parameters, as well as allow to infer about cultural restrictions, breastfeeding practices and certain food taboos, a very remarkable characteristics for anthropological populational research

Balancing life history investment decisions in founding ant queens

Reproduction is a very critical step in the life of an organism. Females must balance their investment in different life-history traits while reproducing. During the process of colony founding in social organisms, such as ants or bees, a trade-off between reproduction and immunity might be very stringent, because queens might be constrained to invest into immune protection of themselves and their developing offspring until the first workers emerge. Here we investigate how different levels of microbial pressure affect colony founding success of Lasius niger ant queens and whether investment into immune defense traits comes at a substantial cost to the queens. In a first experiment mated queens were exposed to four different environments: sterile housing, autoclaved soil, untreated soil and soil containing two opportunistic pathogens. In this experiment, we investigated an immediate cost, i.e., the success of producing the first brood, and a potential delayed cost, i.e., queen survival and colony founding success after hibernation. For the latter, we removed the first brood after hibernation to reveal hidden costs via the application of an additional stressor. We found that irrespective of the microbial environment all queens successfully managed to start a colony, with queens in the soil treatments showing a higher worker production than the queens in the sterile environment. This suggests that either soil components or soil microbes benefit colony growth. After hibernation queens in microbe soil showed significantly lower survival and could not replace a lost brood. In a second experiment, we investigated whether external immune defense in the form of formic acid use can explain part of the costs imposed on queens. We found that queens used formic acid to sanitize their new nest suggesting that queens founding a colony under high microbial pressure are forced to pay a substantial cost by investing in both reproduction and immunity simultaneously. Our results suggest that early, simultaneous investment in reproduction and immunity can allow colony growth under microbial pressure but may be costly in terms of resistance to later challenges. Ant queens may thus be trading off insurance against future challenges for increased pathogen immunity

Attachment of Laboulbeniales fungi on their ant hosts: ultrastructural study

24 - Social insect host-microbe interactions, Poste

Ants Disinfect Fungus-Exposed Brood by Oral Uptake and Spread of Their Poison

SummaryTo fight infectious diseases, host immune defenses are employed at multiple levels. Sanitary behavior, such as pathogen avoidance and removal, acts as a first line of defense to prevent infection [1] before activation of the physiological immune system. Insect societies have evolved a wide range of collective hygiene measures and intensive health care toward pathogen-exposed group members [2]. One of the most common behaviors is allogrooming, in which nestmates remove infectious particles from the body surfaces of exposed individuals [3]. Here we show that, in invasive garden ants, grooming of fungus-exposed brood is effective beyond the sheer mechanical removal of fungal conidiospores; it also includes chemical disinfection through the application of poison produced by the ants themselves. Formic acid is the main active component of the poison. It inhibits fungal growth of conidiospores remaining on the brood surface after grooming and also those collected in the mouth of the grooming ant. This dual function is achieved by uptake of the poison droplet into the mouth through acidopore self-grooming and subsequent application onto the infectious brood via brood grooming. This extraordinary behavior extends the current understanding of grooming and the establishment of social immunity in insect societies

Destructive disinfection of infected brood prevents systemic disease spread in ant colonies

Social insects protect their colonies from infectious disease through collective defences that result in social immunity. In ants, workers first try to prevent infection of colony members. Here, we show that if this fails and a pathogen establishes an infection, ants employ an efficient multicomponent behaviour − "destructive disinfection" − to prevent further spread of disease through the colony. Ants specifically target infected pupae during the pathogen's non-contagious incubation period, relying on chemical 'sickness cues' emitted by pupae. They then remove the pupal cocoon, perforate its cuticle and administer antimicrobial poison, which enters the body and prevents pathogen replication from the inside out. Like the immune system of a body that specifically targets and eliminates infected cells, this social immunity measure sacrifices infected brood to stop the pathogen completing its lifecycle, thus protecting the rest of the colony. Hence, the same principles of disease defence apply at different levels of biological organisation

Land-cover and climate factors contribute to the prevalence of the ectoparasitic fungus Laboulbenia formicarum in its invasive ant host Lasius neglectus

International audienceUnderstanding the distribution of parasites is crucial for biodiversity conservation. Here, we studied the distribution of the ectoparasitic fungus Laboulbenia formicarum in native and invasive Lasius ants in a 2000 km2 area. We screened over 16,000 ant workers in 478 colonies of five different species. We found that Lab. formicarum was rare in native Lasius species but infected 58% of the colonies of the invasive species Las. neglectus. At landscape scale, Lab. formicarum presence could not be explained by geographic and genetic distances between Las. neglectus colonies but was associated with hotter and dryer climatic conditions and its prevalence in colonies increased with urbanization. Within infected colonies, fungal prevalence varied from 0 to 100 percent within meters and was negatively correlated with impervious ground cover. In a changing world, our findings emphasize the importance of land-use and climatic factors in shaping the distribution and prevalence of fungal parasites

Social Transfer of Pathogenic Fungus Promotes Active Immunisation in Ant Colonies

Social contact with fungus-exposed ants leads to pathogen transfer to healthy nest-mates, causing low-level infections. These micro-infections promote pathogen-specific immune gene expression and protective immunization of nest-mates