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Variation in gene expression leads to phenotypic diversity and plays a central role in caste differentiation of eusocial insect species. In social Hymenoptera, females with the same genetic background can develop into queens or workers, which are characterized by divergent morphologies, behaviours and lifespan. Moreover, many social insects exhibit behaviourally distinct worker castes, such as brood-tenders and foragers. Researchers have just started to explore which genes are differentially expressed to achieve this remarkable phenotypic plasticity. Although the queen is normally the only reproductive individual in the nest, following her removal, young brood-tending workers often develop ovaries and start to reproduce. Here, we make use of this ability in the ant Temnothorax longispinosus and compare gene expression patterns in the queens and three worker castes along a reproductive gradient. We found the largest expression differences between the queen and the worker castes (~2500 genes) and the smallest differences between infertile brood-tenders and foragers (~300 genes). The expression profile of fertile workers is more worker-like, but to a certain extent intermediate between the queen and the infertile worker castes. In contrast to the queen, a high number of differentially expressed genes in the worker castes are of unknown function, pointing to the derived status of hymenopteran workers within insects.

Abstract. Quasi-free photoproduction of η -mesons off nucleons bound in the deuteron has been measured with the combined Crystal Barrel -TAPS detector. The experiment was done at a tagged photon beam of the ELSA electron accelerator in Bonn for incident photon energies from the production threshold up to 2.5 GeV. The η -mesons have been detected in coincidence with recoil protons and recoil neutrons. The quasi-free proton data are in good agreement with the results for free protons, indicating that nuclear effects have no significant impact. The coincidence with recoil neutrons provides the first data for the γn → nη reaction. In addition, also first estimates for coherent η -production off the deuteron have been obtained. In agreement with model predictions, the total cross-section for this channel is found to be very small, at most at the level of a few nb. The data are compared to model calculations taking into account contributions from nucleon resonances and t-channel exchanges.

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SignificanceSocial insects such as honey bees or termites are promising new models for aging research. In contrast to short-lived models like the fruit fly or mouse, the reproductives of an insect colony have exceptionally long lifespans. This offers important new avenues for gerontology, especially as mechanisms underlying aging are highly conserved among animals. We studied aging in a termite from the wild. Our results suggest that aging in this species, as in other animals, is related to the activity of transposable elements (TEs; also known as “jumping genes”). Yet reproductives seem to be protected by a process that normally silences TEs in the germline of animals. This suggests that natural selection used a mechanism from the germline to protect whole animals.

The photoproduction of ω mesons on nuclei has been investigated using the Crystal Barrel/TAPS experiment at the ELSA tagged photon facility in Bonn. The aim is to study possible in-medium modifications of the ω meson via the reaction γ + A → ω + X → π 0 γ + X ′ . Results obtained for Nb are compared to a reference measurement on a LH2 target. While for recoiling, long-lived mesons (π 0 , η and η ′ ), which decay outside of the nucleus, a difference in the lineshape for the two data samples is not observed, we find a significant enhancement towards lower masses for ω mesons produced on the Nb target. For momenta less than 500 MeV/c an in-medium ω meson mass of M medium = [722 +2 −2 (stat) +35 −5 (syst)] MeV/c 2 has been deduced at an estimated average nuclear density of 0.6 ρ0.

Abstract. The electric form factor of the neutron, GE,n, has been measured at the Mainz Microtron by recoil polarimetry in the quasielastic D( e, e ′ n)p reaction. Three data points have been extracted at squared four-momentum transfers Q 2 = 0.3, 0.6 and 0.8 (GeV/c) 2 . Corrections for nuclear binding effects have been applied. PACS. 13.40.Gp Electromagnetic form factors -14.20.Dh Protons and neutrons -13.88.+e Polarisation in interactions and scattering

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