Senescence of the cellular immune response in Drosophila melanogaster

Immune system effectiveness generally declines as animals age, compromising disease resistance. In Drosophila, expression of a variety of immune-related genes elevates during ageing; however how this is linked to increasing pathogen susceptibility in older flies has remained unclear. We investigated whether changes in the Drosophila cellular immune response might contribute to immunosenescence. Experiments studied fly cohorts of different ages and compared the numbers and activity of the circulating haemocytes involved in pathogen defence. In female wildtype Samarkand and Oregon R flies the haemocyte population fell by 31.8% and 10.2% respectively during the first four weeks of adulthood. Interestingly we detected no such decline in male flies. The impact of ageing on the phagocytic activity of haemocytes was investigated by injecting flies with fluorescently labelled microbes or latex beads and assessing the ability of haemocytes to engulf them. For all immune challenges the proportion of actively phagocytosing haemocytes decreased as flies aged. Whilst 24.3% ± 1.15% of haemocytes in one-week-old flies phagocytosed Escherichia coli bacteria or Beauveria bassiana fungal spores, this decreased to 16.7% ± 0.99% in four-week-old flies. This clear senescence of the Drosophila cellular immune response may underpin increased disease susceptibility in older flies

Ageing in personal and social immunity: do immune traits senesce at the same rate?

1) How much should an individual invest in immunity as it grows older? Immunity is costly and its value is likely to change across an organism’s lifespan. A limited number of studies have focused on how personal immune investment changes with age in insects, but we do not know how social immunity, immune responses that protect kin, changes across lifespan, or how resources are divided between these two arms of the immune response. 2) In this study both personal and social immune function are considered in the burying beetle, Nicrophorus vespilloides. We show that personal immune function declines (phenoloxidase levels) or is maintained (defensin expression) across lifespan in non-breeding beetles but is maintained (phenoloxidase levels) or even upregulated (defensin expression) in breeding individuals. In contrast, social immunity increases in breeding burying beetles up to middle age, before decreasing in old age. Social immunity is not affected by a wounding challenge across lifespan, whereas personal immunity, through PO, is upregulated following wounding to a similar extent across lifespan. 3) Personal immune function may be prioritised in younger individuals in order to ensure survival until reproductive maturity. If not breeding, this may then drop off in later life as state declines. As burying beetles are ephemeral breeders, breeding opportunities in later life may be rare. When allowed to breed beetles may therefore invest heavily in ‘staying alive’ in order to complete what could potentially be their final reproductive opportunity. As parental care is important for the survival and growth of offspring in this genus, staying alive to provide care behaviours will clearly have fitness payoffs. 4) This study shows that all immune traits do not senesce at the same rate. In fact, the patterns observed depend upon the immune traits measured and the breeding status of the individual

A Revision of Malagasy Species of Anochetus Mayr and Odontomachus Latreille (Hymenoptera: Formicidae)

Species inventories are essential for documenting global diversity and generating necessary material for taxonomic study and conservation planning. However, for inventories to be immediately relevant, the taxonomic process must reduce the time to describe and identify specimens. To address these concerns for the inventory of arthropods across the Malagasy region, we present here a collaborative approach to taxonomy where collectors, morphologists and DNA barcoders using cytochrome c oxidase 1 (CO1) participate collectively in a team-driven taxonomic process. We evaluate the role of DNA barcoding as a tool to accelerate species identification and description. This revision is primarily based on arthropod surveys throughout the Malagasy region from 1992 to 2006. The revision is based on morphological and CO1 DNA barcode analysis of 500 individuals. In the region, five species of Anochetus (A

Défenses immunitaires et division du travail chez les fourmis

Chez les insectes sociaux, les défenses immunitaires sont importantes à la fois pour la survie individuelle et pour la protection de la colonie contre les infections parasitaires. Nous avons étudié comment les défenses immunitaires, qui sont un trait coûteux, étaient modulées par la division du travail concernant la reproduction ou les autres tâches. En effet, les différentes fonctions assurées par les individus au sein de la colonie peuvent être associées à des contraintes sélectives distinctes et donc faire varier l investissement immunitaire. Réciproquement, considérer les défenses immunitaires comme un trait d histoire de vie peut aider à comprendre certains aspects de l évolution sociale. Les fourmis offrent des modèles intéressants pour ces problématiques. Dans un premier temps, nous avons étudié l impact des conflits reproducteurs dans une espèce de fourmi sans reine, Diacamma sp. Nilgiri. Un taux plus faible de travail et une immunosuppression ont été observés dans les groupes affectés par les conflits, ce qui suggère un coût des conflits reproducteurs. Dans un deuxième temps, nous avons examiné les niveaux de phénoloxydase (PO) et prophénoloxydase (PPO), deux enzymes importantes du système immunitaire des insectes, chez les ouvrières de la fourmi Cataglyphis velox. Nous avons trouvé que les fourrageuses présentaient des niveaux plus élevés de PO que les ouvrières internes. Ceci semble indiquer une élévation du niveau de PO chez les fourrageuses en lien avec le risque élevé de blessures et d infection à l extérieur du nid. Enfin, nous avons fait l hypothèse que les ouvrières inactives, fréquemment observées dans les colonies, pourraient investir plus de ressources dans les défenses immunitaires. Nous avons conduit une étude comportementale chez Cataglyphis velox associée à des mesures de défenses immunitaires. Nous n avons pas mis en évidence de lien entre l inactivité des ouvrières et leurs défenses immunitaires mais d autres paramètres immunitaires pourraient être analysés. L ensemble de ces travaux suggère que la division du travail pourrait influencer la variation intra-coloniale dans l immunité et souligne l importance de prendre en compte les défenses immunitaires dans l étude des insectes sociaux.Immune defence is a fundamental trait determining fitness in social insects, both by increasing individual survival and by limiting contamination at colony level. We investigated how individual variation in immune defence, which is a costly trait, is related to division of labour concerning reproduction or sterile tasks. Indeed, the different worker functions within the colony may be associated to distinct selection pressures and thus induce a variation in immune defence. Reciprocally, including immune defence as a life-history trait can help to understand some aspects of social evolution. Ants offer interesting models to address these questions. Firstly, we studied the effects of reproductive conflicts on labour and immune defence in a queenless ant, Diacamma sp. from Nilgiri. The groups affected by conflicts showed a lower rate of labour and an immunosuppression, suggesting a cost of reproductive conflicts. Secondly, we investigated the levels of phenoloxidase (PO) and prophenoloxidase (PPO), two major enzymes of the insect immune system, in workers of the ant Cataglyphis velox. We found a higher PO activity in foragers than in intra-nidal workers, which could result from an adaptive up-regulation of PO in foragers in relation to the high risk of infection and wounding outside the nest. Finally, we hypothesized that inactive workers, often observed in social insect colonies, may invest more resources in immune defence. We conducted a behavioural and immunological study in Cataglyphis velox to analyse the relation between inactivity and immune defence. Our hypothesis was not supported but could be further studied by measuring other immune parameters. This work suggests that division of labour may influence the intra-colonial immune variation and highlights the importance of considering immune defence for the study of social insects.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Worker thelytoky allows requeening of orphaned colonies but increases susceptibility to reproductive cheating in an ant

The file contains the microsatellite genotypes of the individuals used in the paper by Doums et al. Animal Behaviour (2017). Each line corresponds to an individual with its identity, enclosure number (enclosure 7 is missing), nest number, nest origin (QR = from queenright colony , QL = from queenless colony), its caste (male, foreignmale, diploidmale, worker, gyne, queen), its age (found at the pupal stage, as callow or adult), and its genotypes. For each microsatellite locus, the two alleles are given in two separated column labelled by the locus name and the allele number (a or b). Missing data or the second allele of haploid genotypes is indicated by NA

Dataset for the paper worker thelytoky allows requeening of orphaned colonies but increases susceptibility to reproductive cheating in an ant

The file contains the microsatellite genotypes of the individuals used in the paper by Doums et al. Animal Behaviour (2017). Each line corresponds to an individual with its identity, enclosure number (enclosure 7 is missing), nest number, nest origin (QR = from queenright colony , QL = from queenless colony), its caste (male, foreignmale, diploidmale, worker, gyne, queen), its age (found at the pupal stage, as callow or adult), and its genotypes. For each microsatellite locus, the two alleles are given in two separated column labelled by the locus name and the allele number (a or b). Missing data or the second allele of haploid genotypes is indicated by NA

To have and not to have sex: when multiple evolutions of conditional use of sex elegantly solve the question in the ant genus Cataglyphis

International audienceOrganisms use an amazingly large diversity of mechanisms to pass on their genes to the next generation. Sex is ancestral in eukaryotes, where it remains the most widespread way of reproduction. By combining one's genes with those of a partner, sex entails a dilution of one's genes at each generation. Evolution has been particularly creative in devising mechanisms allowing females to avoid this dilution, from classical parthenogenesis to the elimination of male genes after fertilization (Bell, 1982). Moreover, the term parthenogenesis include various forms. Parthenogenesis can be used for female (thelytoky) or male (arrhenotoky) production and it can be associated with different cytological mechanisms, from strict clonality to meiotic division with the fusion of two of the four products of meiosis to restore diploidy (Suomalainen, Saura, & Lokki, 1987). Understanding the evolution of these diverse reproductive systems remains one of the most exciting and longstanding questions in evolutionary biology. By characterizing the reproductive systems of 11 species from the thermophilic ant genus Cataglyphis, in this issue of Molecular Ecology, Kuhn, Darras, Paknia, & Aron (2020) show the high lability of parthenogenesis, with multiple independent evolution of facultative thelytoky from sexual ancestors. The diversity of life history traits and social characteristics of this genus (e.g. mode of colony foundation, female polyandry) provides a unique and exciting opportunity to investigate the social and environmental factors driving the evolution of reproductive systems in social Hymenoptera

Dataset for the paper worker thelytoky allows requeening of orphaned colonies but increases susceptibility to reproductive cheating in an ant

The file contains the microsatellite genotypes of the individuals used in the paper by Doums et al. Animal Behaviour (2017). Each line corresponds to an individual with its identity, enclosure number (enclosure 7 is missing), nest number, nest origin (QR = from queenright colony , QL = from queenless colony), its caste (male, foreignmale, diploidmale, worker, gyne, queen), its age (found at the pupal stage, as callow or adult), and its genotypes. For each microsatellite locus, the two alleles are given in two separated column labelled by the locus name and the allele number (a or b). Missing data or the second allele of haploid genotypes is indicated by NA.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV