In eusocial insects, the division of labour means, among other things, that only few individuals forage for the entire colony. The survival of the colony depends on their efficiency in fitting the nutritional needs of all its members. We aimed at measuring the network topology and at understanding the role and centrality of each caste in this network and as a consequence on food dissemination across castes. We constructed the trophallaxis networks from 34 food exchanges experiments-in black garden ants (Lasius niger). We tested the influence of brood and colony size on: (i) global indices at the network level, i.e. efficiency, resilience, centralisation and modularity; (ii) the individuals' values of degree, strength, betweenness and clustering coefficient. Network resilience, which is the ratio between global efficiency and centralisation, is stable with colony size but increases with the presence of a brood, in order to possibly respond to the needs of larvae. Individual metrics highlighted the major role of foragers in food dissemination. In addition, a hierarchical clustering analysis suggested that some trophallactic network against resource quality.
Studies on cooperative breeders have addressed the efects of non-breeding 'helpers' on reproduction and parental care, but the consequences for ofspring physiology and long-term survival are less understood. Helpers are expected to beneit ofspring, but their presence can also lead to decreased pre-or post-natal parental reproductive efort. To examine whether prenatal and postnatal helpers inluence ofspring condition, we conducted a whole-clutch cross-fostering experiment in sociable weavers (Philetairus socius) that altered the nestlings' social environment (presence/absence of helpers). We tested whether relative telomere length (rTL), an indicator of somatic maintenance, was inluenced by prenatal and/or postnatal presence of helpers 9 and 17 days after hatching, and whether rTL predicted long-term survival. Nine days after hatching, we found an overall positive efect of postnatal helpers on rTL: for nestlings with prenatal helpers, a reduction in the number of helpers post-hatch was associated with shorter telomeres, while nestlings swapped from nests without helpers to nests with helpers had a larger rTL. However, when prenatal helpers were present, an increased number of helpers after hatching led to shorter telomeres. Nine-day old chicks with longer rTL tended to be more likely to survive over the 5 years following hatching. However, close to ledging, there was no detectable efect of the experiment on rTL and no link between rTL and survival. This experimental study of a wild cooperative breeder, therefore, presents partial support for the importance of the presence of helpers for ofspring rTL and the link between early-life telomere length and long-term survival.
The social organisation of many primate, bird and rodent species and the role of individuals within 24 that organisation are associated with specific individual physiological traits. However, this 25 association is perhaps most pronounced in eusocial insects (e.g., termites, ants). In such species, 26 genetically close individuals show significant differences in behaviour, physiology, and life 27 expectancy. Studies addressing the metabolic changes according to the social role are still lacking.
28We aimed at understanding how sociality could influence essential molecular processes in a 29 eusocial insect, the black garden ant (Lasius niger) where queens can live up to ten times longer 30 than workers. Using mass spectrometry-based analysis, we explored the whole metabolome of 31 queens, nest-workers and foraging workers. A former proteomics study done in the same species 32 allowed us to compare the findings of both approaches. Confirming the former results at the 33 proteome level, we showed that queens had fewer metabolites related to immunity. Contrary to 34 our predictions, we did not find any metabolite linked to reproduction in queens. Among the 35 workers, foragers had a metabolic signature reflecting a more stressful environment and a more 36 highly stimulated immune system. We also found that nest-workers had more digestion-related 37 metabolites. Hence, we showed that specific metabolic signatures match specific social roles.
38Besides, we identified metabolites differently expressed among behavioural castes and involved 39 in nutrient sensing and longevity pathways (e.g., sirtuins, FOXO). The links between such 40 molecular pathways and ageing being found in an increasing number of taxa, our results confirm 41 and strengthen their potential universality.
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