RESUMEN
Structurally diverse queen pheromones and fertility signals regulate the reproductive division of labor of social insects, such as ants, termites, some bees, and some wasps. The independent evolution of sociality in these taxa allows for the exploration of how natural history differences in sender and receiver properties led to the evolution of these complex communication systems. While describing the different effects and the structural diversity of queen pheromones, we identify two major syndromes that mostly separate ants and wasps from bees and termites in their use of different pheromone classes. We compare olfactory receptor evolution among these groups and review physiological and hormonal links to fecundity and pheromone production. We explore the cases in which queen pheromone evolution is conserved, convergent, or parallel and those in which queen pheromone responses are more likely to be learned or innate. More mechanistic information about the pathways linking fecundity to queen pheromone production and perception could help close major knowledge gaps.
RESUMEN
Insect societies discriminate against foreigners to avoid exploitation. In ants, helper workers only accept individuals with the familiar chemical cues of their colony. Similarly, unfamiliar eggs may get rejected at their first appearance in the nest. We investigated egg acceptance mechanisms by introducing different types of foreign eggs into worker groups of the ant Camponotus floridanus. Workers from established colonies familiar with queen-laid eggs always accepted eggs from highly fecund queens, but worker-laid eggs only after exposure for several weeks. Workers naive to eggs only rejected worker-laid eggs once they had prior exposure to eggs laid by highly fecund queens, suggesting that prior exposure to such eggs is necessary for discrimination. The general acceptance of eggs from highly fecund queens, irrespective of previous worker egg exposure, suggests an innate response to the queen pheromone these eggs carry. Workers learned to accept queen-laid eggs from different species, indicating high flexibility in learning egg-recognition cues. In incipient colonies with queen-laid eggs that carry a weak queen pheromone, worker-laid eggs were more likely to get accepted than queen-laid eggs from a different species, suggesting that the similarity of egg-recognition cues between the two types of C. floridanus eggs increases acceptance.
RESUMEN
Understanding the diversity of insect societies is tied to explaining the mechanisms of reproductive division of labor. Small societies were not expected to use chemical signals or queen pheromones for this purpose. A new study shows that one of them does while using unexpected compounds.
Asunto(s)
Odorantes , Sudor , Animales , Abejas , Insectos , Lactonas , FeromonasRESUMEN
Gut-associated microbiota of ants include Rhizobiales bacteria with affiliation to the genus Bartonella. These bacteria may enable the ants to fix atmospheric nitrogen, but no genomes have been sequenced yet to test the hypothesis. Sequence reads from a member of the Rhizobiales were identified in the data collected in a genome project of the ant Harpegnathos saltator. We present an analysis of the closed 1.86 Mb genome of the ant-associated bacterium, for which we suggest the species name Candidatus Tokpelaia hoelldoblerii. A phylogenetic analysis reveals a relationship to Bartonella and Brucella, which infect mammals. Novel gene acquisitions include a gene for a putative extracellular protein of more than 6,000 amino acids secreted by the type I secretion system, which may be involved in attachment to the gut epithelium. No genes for nitrogen fixation could be identified, but genes for a multi-subunit urease protein complex are present in the genome. The urease genes are also present in Brucella, which has a fecal-oral transmission pathway, but not in Bartonella, which use blood-borne transmission pathways. We hypothesize that the gain and loss of the urease function is related to transmission strategies and lifestyle changes in the host-associated members of the Rhizobiales.
Asunto(s)
Alphaproteobacteria/genética , Hormigas/microbiología , Genoma Bacteriano , Alphaproteobacteria/clasificación , Alphaproteobacteria/aislamiento & purificación , Animales , Proteínas Bacterianas/clasificación , Proteínas Bacterianas/genética , Análisis por Conglomerados , Microbioma Gastrointestinal , Glutamato-Amoníaco Ligasa/clasificación , Glutamato-Amoníaco Ligasa/genética , Fijación del Nitrógeno/genética , Filogenia , ARN Ribosómico 16S/química , ARN Ribosómico 16S/genética , ARN Ribosómico 16S/metabolismo , Simbiosis , Sistemas de Secreción Tipo I/química , Sistemas de Secreción Tipo I/clasificación , Sistemas de Secreción Tipo I/metabolismo , Ureasa/clasificación , Ureasa/genéticaRESUMEN
BACKGROUND: The molecular mechanisms of variations in individual longevity are not well understood, even though longevity can be increased substantially by means of diverse experimental manipulations. One of the factors supposed to be involved in the increase of longevity is a higher stress resistance. To test this hypothesis in a natural system, eusocial insects such as bees or ants are ideally suited. In contrast to most other eusocial insects, ponerine ants show a peculiar life history that comprises the possibility to switch during adult life from a normal worker to a reproductive gamergate, therewith increasing their life expectancy significantly. RESULTS: We show that increased resistance against major stressors, such as reactive oxygen species and infection accompanies the switch from a life-history trait with normal lifespan to one with a longer life expectancy. A short period of social isolation was sufficient to enhance stress resistance of workers from the ponerine ant species Harpegnathos saltator significantly. All ant groups with increased stress resistances (reproducing gamergates and socially isolated workers) have lower catalase activities and glutathione levels than normal workers. Therewith, these ants resemble the characteristics of the youngest ants in the colony. CONCLUSIONS: Social insects with their specific life history including a switch from normal workers to reproducing gamergates during adult life are well suited for ageing research. The regulation of stress resistance in gamergates seemed to be modified compared to foraging workers in an economic way. Interestingly, a switch towards more stress resistant animals can also be induced by a brief period of social isolation, which may already be associated with a shift to a reproductive trajectory. In Harpegnathos saltator, stress resistances are differently and potentially more economically regulated in reproductive individuals, highlighting the significance of reproduction for an increase in longevity in social insects. As already shown for other organisms with a long lifespan, this trait is not directly coupled to higher levels of enzymatic and non-enzymatic antioxidants.