The evolution of sex determination

Sexual reproduction is a fundamental aspect of life. Sex-determination mechanisms are responsible for the sexual fate and development of sexual characteristics in an organism, be it a unicellular alga, a plant, or an animal. Surprisingly, sex-determination mechanisms are not evolutionarily conserved but are bewilderingly diverse and appear to have had rapid turnover rates during evolution. Evolutionary biologists continue to seek a solution to this conundrum. What drives the surprising dynamics of such a fundamental process that always leads to the same outcome: two sex types, male and female? The answer is complex but the ongoing genomic revolution has already greatly increased our knowledge of sex-determination systems and sex chromosomes in recent years. This novel book presents and synthesizes our current understanding, and clearly shows that sex-determination evolution will remain a dynamic field of future research. The Evolution of Sex Determination is an advanced, research level text suitable for graduate students and researchers in genetics, developmental biology, and evolution.

Effect of food on immature development, consumption rate, and relative growth rate of Toxorhynchites splendens (Diptera: Culicidae), a predator of container breeding mosquitoes

Food utilization by the larvae of Toxorhynchites splendens (Wiedemann) was studied in the laboratory by offering larvae of Aedes aegypti Linnaeus, Anopheles stephensi (Liston), and Culex quinquefasciatus (Say). Quantitative analyses of data indicated that immature development was significantly faster with increase in food availability. The regression analysis showed that the degrees of the relationship between immature duration (Id) and food availability were higher when offered early instars of prey (first and second instars) than late instars. Consumption rate (Cr) of the predator increased with increase in food availability and this relationship was highly significant when larvae of An. stephensi were offered as food. Consumption rate to food level decreased with increase in the age class of the prey. There was a significant negative correlation between Id and Cr. This aspect helps to increase population turnover of T. splendens in a shorter period when the prey is abundant. Conversely, the predator compensated the loss in daily food intake at low food level by extending Id thereby attains the minimum threshold pupal weight for adult emergence. There was an increase in the relative growth rate (RGR) of the predator when An. stephensi was offered as prey and this was related to the high protein content of the prey per body weight. There was a positive correlation between Cr and RGR. This adaptive life characteristic strategy of this predator is useful for mass-rearing for large scale field release programmes in the control of container breeding mosquitoes is discussed.

ICT Action Plan Meeting the high-level skills needs of enterprise in Ireland

The technology sector in Ireland is thriving. Employment, through indigenous and multinational technology firms continues to grow strongly year on year. All of the top 10 multinational technology companies have a significant presence in Ireland and the indigenous software sector’s exports are worth well in excess of €1 billion annually. Five of the top 10 exporters in Ireland are technology companies, and the sector is responsible for approximately one-third of Ireland’s total turnover. Since January 2011, over 80 jobs a week have been announced in the sector. This is on foot of 6% employment growth in 2009 and 4% in 2010. A recent global competitiveness report ranks Ireland as the top destination in the world by quality and value of investments. With a growing multinational technology presence in Ireland and a vibrant and innovative indigenous software sector, the future prospects for Ireland’s technology sector are bright.

Le médecin de famille de demain [Tomorrow's family doctor].

The profession of family doctor will undergo profound changes in the coming decade due to external, political, demographic and societal developments. Changes will also occur from within the profession affecting its content and its functioning. Other influences, in addition to generational developments (reduced working hours, feminisation, revaluation of the work-life balance), will come from collaboration with new professions, news structures as well as technical and human progress. In this transitional period it is important to uphold core values of family medicine, in particular coordination, continuity of care and the global approach to patients. In training future family doctors we must both prepare them for new skills and roles, and continue to share the core values with them.

10

Research on individual social policy preferences has highlighted a number of socio-structural cleavages as determinants. Studies investigating public opinion on the various redistributive schemes that make up today's welfare states have shown the relevance of class-related factors such as income or education as key explanatory variables (Ferrera 1993; Taylor-Gooby 1995, 1998; and Svallfors 1997). More recent studies, however, have suggested that other factors are also likely to play a role. Among these, the most important are age, gender, and individual values (Armingeon 2006; Deitch 2004; and Roller 2000, 2002). The scenario that emerges from the existing literature is one of multiple intersecting cleavages, but it remains unclear as to what today is the relative weight and specific impact of each of these cleavages.

Protein synthesis in jejunum and liver of neonatal calves fed vitamin A and lactoferrin

Rates of protein synthesis (PS) and turnover are more rapid during the neonatal period than during any other stage of postnatal life. Vitamin A and lactoferrin (Lf) can stimulate PS in neonates. However, newborn calves are vitamin A deficient and have a low Lf status, but plasma vitamin A and Lf levels increase rapidly after ingestion of colostrum. Neonatal calves (n = 6 per group) were fed colostrum or a milk-based formula without or with vitamin A, Lf, or vitamin A plus Lf to study PS in the jejunum and liver. l-[(13)C]Valine was intravenously administered to determine isotopic enrichment of free (nonprotein-bound) Val (AP(Free)) in the protein precursor pool, atom percentage excess (APE) of protein-bound Val, fractional protein synthesis rate (FSR) in the jejunum and liver, and isotopic enrichment of Val in plasma (APE(Pla)) and in the CO(2) of exhaled air (APE(Ex)). The APE, AP(Free), and FSR in the jejunum and liver did not differ significantly among groups. The APE(Ex) increased, whereas APE(Pla) decreased over time, but there were no group differences. Correlations were calculated between FSR(Jej) and histomorphometrical and histochemical data of the jejunum, and between FSR(Liv) and blood metabolites. There were negative correlations between FSR(Liv) and plasma albumin concentrations and between FSR(Jej) and the ratio of villus height:crypt depth, and there was a positive correlation between FSR(Jej) and small intestinal cell proliferation in crypts. Hence, there were no effects of vitamin A and Lf and no interactions between vitamin A and Lf on intestinal and hepatic PS. However, FSR(Jej) was correlated with histomorphometrical traits of the jejunum and FSR(Liv) was correlated with plasma albumin concentrations.

Response of bone metabolism related hormones to a single session of strenuous exercise in active elderly subjects

OBJECTIVE: To evaluate the effect of strenuous exercise on bone metabolism and related hormones in elderly subjects. METHODS: Twenty one active elderly subjects (11 men and 10 women; mean age 73.3 years) showing a mean theoretical Vo2max of 151.4% participated. Concentrations of plasma ionised calcium (iCa), serum intact parathyroid hormone (iPTH), 25-hydroxyvitamin D (25(OH)D), and 1.25-dihydroxy-vitamin D3 (1.25(OH)2D3), as well as the bone biochemical markers type I collagen C-telopeptide for bone resorption and osteocalcin and bone alkaline phosphatase for bone formation, were analysed before and after a maximal incremental exercise test. RESULTS: At basal level, iPTH was positively correlated with age (r = 0.56, p < 0.01) and negatively correlated with 25(OH)D (r = -0.50; p < 0.01) and 1.25(OH)2D3 (r = -0.47; p < 0.05). Moreover, 25(OH)D and 1.25(OH)2D3 levels were negatively correlated with age (r = -0.50, p < 0.01 and r = -0.53, p < 0.01, respectively). After exercise, iCa and 25(OH)D decreased (p < 0.001 and p = 0.01, respectively) while iPTH increased (p < 0.001). The levels of 1.25(OH)2D3, bone biochemical markers, haematocrit, and haemoglobin were unchanged. The variations in iCa and 25(OH)D were not related to age and/or sex. The iPTH variation was directly related to basal iPTH levels (p < 0.01) and indirectly related to age. CONCLUSIONS: In active elderly subjects, strenuous exercise disturbed calcium homeostasis and bone related hormones without immediate measurable effect on bone turnover. Although an increase in iPTH could have an anabolic action on bone tissue, our findings from our short term study did not allow us to conclude that such action occurred.

War and Natural Resource Exploitation

We build a theoretical framework that allows for endogenous conflict behaviour (i.e., fighting efforts) and for endogenous natural resource exploitation (i.e., speed, ownership, and investments). While depletion is spread in a balanced Hotelling fashion during peace, the presence of conflict creates incentives for rapacious extraction, as this lowers the stakes of future contest. This voracious extraction depresses total oil revenue, especially if world oil demand is relatively elastic and the government's weapon advantage is weak. Some of these political distortions can be overcome by bribing rebels or by government investment in weapons. The shadow of conflict can also make less efficient nationalized oil extraction more attractive than private extraction, as insecure property rights create a holdup problem for the private firm and lead to a lower license fee. Furthermore, the government fights less intensely than the rebels under private exploitation, which leads to more government turnover. Without credible commitment to future fighting efforts, private oil depletion is only lucrative if the government's non-oil office rents are large and weaponry powerful, which guarantees the government a stronger grip on office and makes the holdup problem less severe.

The balanced lethal system of crested newts: a ghost of sex chromosomes past?

Balanced lethal systems are more than biological curiosities: as theory predicts, they should quickly be eliminated through the joint forces of recombination and selection. That such systems might become fixed in natural populations poses a challenge to evolutionary theory. Here we address the case of a balanced lethal system fixed in crested newts and related species, which makes 50% of offspring die early in development. All adults are heteromorphic for chromosome pair 1. The two homologues (1A and 1B) have different recessive deleterious alleles fixed on a nonrecombining segment, so that heterozygotes are viable, while homozygotes are lethal. Given such a strong segregation load, how could autosomes stop recombining? We propose a role for a sex-chromosome turnover from pair 1 (putative ancestral sex chromosome) to pair 4 (currently active sex chromosome). Accordingly, 1A and 1B represent two variants (Y(A) and Y(B)) of the Y chromosome from an ancestral male-heterogametic system. We formalize a scenario in which turnovers are driven by sex ratio selection stemming from gene-environment interactions on sex determination. Individual-based simulations show that a balanced lethal system can be fixed with significant likelihood, provided the masculinizing allele on chromosome 4 appears after the elimination of the feminizing allele on chromosome 1. Our study illustrates how strikingly maladaptive traits might evolve through natural selection.

Los medios audiovisuales entre los progenitores y los hijos e hijas

En el presente artículo se exponen los resultados de una investigación realizada con una muestra de adolescentes (N = 1211) entre 12 y 16 años y otra de sus progenitores (N = 462) para explorar cómo las diferentes respuestas generacionales ante la presencia de diversos medios audiovisuales en su entorno próximo afectan las interacciones familiares entre progenitores e hijos/as. Los resultados apuntan al hecho que los progenitores tienden a sobredimensionar tanto el interés como las informaciones de que dispone su propio hijo o hija acerca de la mayor parte de los medios audiovisuales explorados, así como la satisfacción que proporcionan las conversaciones con los adultos acerca de cualquier actividad con estos medios. Los progenitores realizan atribuciones diferentes sobre el uso de medios audiovisuales según se refieran a un hijo o a una hija. Se aprecia una importante diferencia entre la satisfacción con las conversaciones que los y las adolescentes mantienen con sus iguales y la que proporcionan las conversaciones con los adultos respecto a cualquiera de sus actividades con los medios

Role of Notch signalling in intestinal epithelium

Résumé: Chez les mammifères, les intestins sont les organes ayant le plus haut taux de renouvellement cellulaire dans l'organisme. L'épithélium intestinal se renouvelle complètement en moins d'une semaine. Il se compose de projections (villosités) et d'invaginations (cryptes) qui ont toutes deux des fonctions bien distinctes. Les cellules de l'intestin sont constamment produites à partir de cellules souches, situées dans la crypte, qui se différencient en cellules proliférantes transitoires, puis en cellules caliciformes, de Paneth, entéroendocrine ou en entérocytes. Ces cellules migrent dans leurs lieux spécifiques pour accomplir leur fonction physiologique pour finalement mourir. A cours de mon travail de thèse, j'ai étudié le rôle de la voie de signalisation de Notch dans le renouvellement cellulaire et dans le processus de l'homéostase des cellules de l'intestin marin en utilisant le système Cre-loxP pour induire la délétion des gènes Notch1, Notch2, Jaggedl et RBP-Jk. Bien que l'inactivation de Notch1 avec ou sans Jagged1, ou celle de Notch2, n'aboutissent à aucun phénotype, une déficience pour RBP-Jk, ou pour Notch1 et Notch2 simultanément, conduit au développement d'un impressionnant phénotype. Au niveau de la crypte, une rapide et importante modification des cellules apparaît: les cellules proliférantes sont devenues des cellules caliciformes qui ont perdu la capacité de se renouveler. Ces résultats impliquent la voie Notch en tant que nouvelle clé de voûte dans le maintien des cellules qui s'auto-renouvellent dans l'épithélium intestinal. Un rôle similaire a été proposé pour la voie Wnt, laquelle n'est cependant, pas affectée dans nos souris. C'est pourquoi ces deux voies sont essentielles dans le maintien de la prolifération dans les cryptes intestinales. Ce travail a aussi proposé un mécanisme par lequel la voie Notch contrôlerait l'intégrité du cycle cellulaire dans les cellules de la crypte intestinale, ceci en inhibant la transcription d'un inhibiteur du cycle cellulaire, la protéine p27KIP1. De plus, l'inactivation de RBP-Jk dans les adénomes développés par les souris APCmin induisent la différenciation de cellules tumorales en cellules caliciformes. Comme autre effet, la localisation histologique des cellules de Paneth est également affectée par la délétion de RBP-Jk ou de Notch1/Notch2, suggérant un rôle pour la voie Notch dans le compartiment des cellules de Paneth. Finalement, ce travail démontre que les cellules progénitrices de l'intestin ont besoin d'une convergence fonctionnelle des voie Wnt et Notch. Ces résultats préliminaires peuvent être considérés comme un concept pour l'utilisation d'inhibiteurs de secrétase-γ (inhibiteurs de Notch) à des fins thérapeutiques pour les cancers colorectaux. Summary The mammalian intestine has one of the highest cellular turnover rates in the body. The complete intestinal epithelium is renewed in less than a week. It is divided into spatially distinct compartments in the form of finger-like projections (villi) and flask-shaped invaginations (crypts) that are dedicated to specific functions. Intestinal cells are constantly produced from a stem cell reservoir that gives rise to proliferating transient amplifying cells, which subsequently differentiate and home to their specific compartments before dying after having fulfilled their physiological function. In this thesis project, the physiological role of the Notch signalling cascade in the marine intestine was studied. Inducible tissue specific inactivation of Notch1, Notch2, Jagged1 and RBP-Jk genes was applied to assess their role in the maintenance of intestinal homeostasis and cell fate determination. The analysis unequivocally revealed that Notch1, Notch1 and Jagged1 combined as well as Notch2 are dispensable for intestinal homeostasis and lineage differentiation. However, deficiency of RBP-Jk as well as the simultaneous inactivation of both Notch1 and Notch2 receptors unveiled a striking phenotype. In these mice, a rapid and massive conversion of proliferative crypt cells into post-mitotic goblet cells was observed. These results identify the Notch pathway as a key player for the maintenance of the proliferative crypt compartment. A similar role was implicated for the Wnt cascade, which, however, was not affected in the different tissue specific Notch signalling deficient mice. Thus, the Wnt and Notch signalling pathways are essential for the self-renewal capacity of the intestinal epithelium. Furthermore, our results suggest a molecular mechanism for Notch signalling mediated control of cell cycle regulation within the crypt. The Notch cascade inhibits expression of the cyclin-dependent kinase inhibitor p27KIP1 and thereby maintains proliferation of the intestinal progenitor cells. In addition, the inactivation of RBP-Jk in adenomas developed by APCmin mice resulted in the differentiation of tumour cells into goblet cells. Finally, Notch deficiency affected differentiated Paneth cells, suggesting that Notch may play a role in the Paneth cell compartment. In summary, this work clearly demonstrates that undifferentiated, proliferative cells in intestinal crypts require the concerted activation of the RBP-Jk-mediated Notch signalling and the Wnt cascade. In addition, our preliminary results can be considered as a "proof-of-principle" for the use of γ-secretase inhibitors for therapeutic modalities for colorectal cancer.

In vivo quantification of neuro-glial metabolism and glial glutamate concentration using 1H-[13C] MRS at 14.1T.

Astrocytes have recently become a major center of interest in neurochemistry with the discoveries on their major role in brain energy metabolism. An interesting way to probe this glial contribution is given by in vivo (13) C NMR spectroscopy coupled with the infusion labeled glial-specific substrate, such as acetate. In this study, we infused alpha-chloralose anesthetized rats with [2-(13) C]acetate and followed the dynamics of the fractional enrichment (FE) in the positions C4 and C3 of glutamate and glutamine with high sensitivity, using (1) H-[(13) C] magnetic resonance spectroscopy (MRS) at 14.1T. Applying a two-compartment mathematical model to the measured time courses yielded a glial tricarboxylic acid (TCA) cycle rate (Vg ) of 0.27 ± 0.02 μmol/g/min and a glutamatergic neurotransmission rate (VNT ) of 0.15 ± 0.01 μmol/g/min. Glial oxidative ATP metabolism thus accounts for 38% of total oxidative metabolism measured by NMR. Pyruvate carboxylase (VPC ) was 0.09 ± 0.01 μmol/g/min, corresponding to 37% of the glial glutamine synthesis rate. The glial and neuronal transmitochondrial fluxes (Vx (g) and Vx (n) ) were of the same order of magnitude as the respective TCA cycle fluxes. In addition, we estimated a glial glutamate pool size of 0.6 ± 0.1 μmol/g. The effect of spectral data quality on the fluxes estimates was analyzed by Monte Carlo simulations. In this (13) C-acetate labeling study, we propose a refined two-compartment analysis of brain energy metabolism based on (13) C turnover curves of acetate, glutamate and glutamine measured with state of the art in vivo dynamic MRS at high magnetic field in rats, enabling a deeper understanding of the specific role of glial cells in brain oxidative metabolism. In addition, the robustness of the metabolic fluxes determination relative to MRS data quality was carefully studied.

Structured intermittent interruption of chronic HIV infection treatment with highly active antiretroviral therapy: Effects on leptin and TNF-alpha.

The changes in nutritional parameters and adipocytokines after structured intermittent interruption of highly active antiretroviral treatment of patients with chronic HIV infection are analyzed. Twenty-seven patients with chronic HIV infection (median CD4+ T cell count/microl: nadir, 394; at the beginning of structured interruptions, 1041; HIV viral load: nadir, 41,521 copies/ml; at the beginning of structured interruptions <50 copies/ml; median time of previous treatment: 60 months) were evaluated during three cycles of intermittent interruptions of therapy (8 weeks on/4 weeks off). CD4+ T cell count, HIV viral load, anthropometric measures, and serum concentrations of triglycerides, cholesterol, leptin, and tumor necrosis factor and its soluble receptors I and II were determined. After the three cycles of intermittent interruptions of therapy, no significant differences in CD4+ T cell count/microl, viral load, or serum concentrations of cholesterol or triglycerides with reference to baseline values were found. A near-significant higher fatty mass (skinfold thicknesses, at the end, 121 mm, at the beginning, 100 mm, p = 0.100), combined with a significant increase of concentration of leptin (1.5 vs. 4.7 ng/ml, p = 0,044), as well as a decrease in serum concentrations of soluble receptors of tumor necrosis factor (TNFRI, 104 vs. 73 pg/ml, p = 0.022; TNFRII 253 vs. 195 pg/ml, p = 0.098) were detected. Structured intermittent interruption of highly active antiretroviral treatment of patients with chronic HIV infection induces a valuable positive modification in markers of lipid turnover and adipose tissue mass.

Birth and expression evolution of mammalian microRNA genes.

MicroRNAs (miRNAs) are major post-transcriptional regulators of gene expression, yet their origins and functional evolution in mammals remain little understood due to the lack of appropriate comparative data. Using RNA sequencing, we have generated extensive and comparable miRNA data for five organs in six species that represent all main mammalian lineages and birds (the evolutionary outgroup) with the aim to unravel the evolution of mammalian miRNAs. Our analyses reveal an overall expansion of miRNA repertoires in mammals, with threefold accelerated birth rates of miRNA families in placentals and marsupials, facilitated by the de novo emergence of miRNAs in host gene introns. Generally, our analyses suggest a high rate of miRNA family turnover in mammals with many newly emerged miRNA families being lost soon after their formation. Selectively preserved mammalian miRNA families gradually evolved higher expression levels, as well as altered mature sequences and target gene repertoires, and were apparently mainly recruited to exert regulatory functions in nervous tissues. However, miRNAs that originated on the X chromosome evolved high expression levels and potentially diverse functions during spermatogenesis, including meiosis, through selectively driven duplication-divergence processes. Overall, our study thus provides detailed insights into the birth and evolution of mammalian miRNA genes and the associated selective forces.

Social evolution and defences against pathogens in ants

Pathogens represent a threat to all organisms, which generates a coevolutionary arms race. Social insects provide an interesting system to study host-pathogen interactions, because their defences depend on both the individual and collective responses, and involve genetic, physiological, behavioral and organizational mechanisms. In this thesis, I studied the evolutionary ecology of the resistance of ant queens and workers to natural fungal pathogens. Mechanisms that increase within-colony genetic diversity, like polyandry and polygyny, decrease relatedness among colony mates, which reduces the strength of selection for the evolution and maintenance of altruistic behavior. A leading hypothesis posits that intracolonial genetic diversity is adaptive because it reduces the risk of pathogen transmission. In chapter 1, I examine individual resistance in ant workers of Formica selysi, a species that shows natural variation in colony queen number. I discuss how this variation might be beneficial to resist natural fungal pathogens in groups. Overall my results indicate that there is genetic variation for fungal resistance in workers, a requirement for the 'genetic diversity for pathogen resistance' hypothesis. However I was not able to detect direct evidence that group diversity improves the survival of focal ants or reduces pathogen transmission. Thus, although the coexistence of multiple queens increases the within-colony variance in worker resistance, it remains unclear whether it protects ant colonies from pathogens and whether it is comparable to polyandry in other social insects. Traditionally, it was thought that the immune system of invertebrates lacked memory and specificity. In chapter 2, I investigate individual immunity in ant queens and show that they may be able to adjust their pathogen defences in response to their current environment by means of immune priming, which bears similarities with the adaptive immunity of vertebrates. However, my results indicate that the expression of immune priming in ant queens may be influenced by factors like mating status, mating conditions or host species. In addition, I showed that mating increases pathogen resistance in çhe two ant species that I studied (F. selysi and Lasius niger). This raises the question of how ant queens invest heavily in both maintenance and reproduction, which I discuss in the context of the evolution of social organization. In chapter 3,1 investigate if transgenerational priming against a fungal pathogen protects the queen progeny. I failed to detect this effect, and discuss why the detection of transgenerational immune priming in ants is a difficult task. Overall, this thesis illustrates some of the individual and collective mechanisms that likely played a role in allowing ants to become one of the most diverse and ecologically successful groups of organisms. -- Les pathogènes représentent une menace pour tous les organismes, ce qui a engendré l'évolution d'une course aux armements. Les insectes sociaux sont un système intéressant permettant d'étudier les interactions hôtes-pathogènes, car leurs défenses dépendent de réponses aussi bien individuelles que collectives, et impliquent des mécanismes génétiques, physiologiques, comportementaux et organisationnels. Dans cette thèse, j'ai étudié l'écologie évolutive de la résistance des reines et des ouvrières de fourmis exposées à des champignons pathogènes. Les facteurs augmentant la diversité génétique à l'intérieur de la colonie, comme la polyandrie et la polygynie, diminuent la parenté, ce qui réduit la pression de sélection pour l'évolution et la maintenance des comportements altruistes. Une hypothèse dominante stipule que la diversité génétique à l'intérieur de la colonie est adaptative car elle réduit le risque de transmission des pathogènes. Dans le chapitre 1, nous examinons la résistance individuelle à des pathogènes fongiques chez les ouvrières de Formica selysi, une espèce présentant une variation naturelle dans le nombre de reines par colonie. Nous discutons aussi de la possibilité que ces variations individuelles augmentent la capacité du groupe à résister à des champignons pathogènes. Dans l'ensemble, nos résultats indiquent une variation génétique dans la résistance aux champignons chez les ouvrières, un prérequis à l'hypothèse que la diversité génétique du groupe augmente la résistance aux pathogènes. Cependant, nous n'avons pas pu détecter une preuve directe que la diversité du groupe augmente la survie de fourmis focales ou réduise la transmission des pathogènes. Ainsi, bien que la coexistence de plusieurs reines augmente la variance dans la résistance des ouvrières à l'intérieur de la colonie, la question de savoir si cela protège les colonies de fourmis contre les pathogènes et si cela est comparable à la polyandrie chez d'autres insectes sociaux reste ouverte. Traditionnellement, il était admis que le système immunitaire des invertébrés ne possédait pas de mémoire et était non-spécifique. Dans le chapitre 2, nous avons étudié l'immunité individuelle chez des reines de fourmis. Nous avons montré que les reines pourraient être capables d'ajuster leurs défenses contre les pathogènes en réponse à leur environnement, grâce à une pré-activation du système immunitaire (« immune priming ») ressemblant à l'immunité adaptative des vertébrés. Cependant, nos résultats indiquent que cette pré-activation du système immunitaire chez les reines dépend du fait d'être accouplée ou non, des conditions d'accouplement, ou de l'espèce. De plus, nous avons montré que l'accouplement augmente la résistance aux pathogènes chez les deux espèces que nous avons étudié (F. selysi et Lasius niger). Ceci pose la question de la capacité des reines à investir fortement aussi bien dans la maintenance que dans la reproduction, ce que nous discutons dans le contexte de l'évolution de l'organisation sociale. Dans le chapitre 3, nous étudions si la pré-activation trans-générationelle du système immunitaire [« trans-generational immune priming ») protège la progéniture de la reine contre un champignon pathogène. Nous n'avons par réussi à détecter cet effet, et discutons des raisons pour lesquelles la détection de la pré-activation trans-générationelle du système immunitaire chez les fourmis est une tâche difficile. Dans l'ensemble, cette thèse illustre quelques-uns des mécanismes individuels et collectifs qui ont probablement contribué à la diversité et à l'important succès écologique des fourmis.