Low-energy electric dipole response in 120Sn

The electric dipole strength in 120Sn has been extracted from proton inelastic scattering experiments at E_p = 295 MeV and at forward angles including 0 degree. Below neutron threshoild it differs from the results of a 120Sn(gamma,gamma') experiment and peaks at an excitation energy of 8.3 MeV. The total strength corresponds to 2.3(2)% of the energy-weighted sum rule and is more than three times larger than what is observed with the (gamma,gamma') reaction. This implies a strong fragmentation of the E1 strength and/or small ground state branching ratios of the excited 1- states.Comment: 7 pages, 6 figure

Dipole polarizability of 120Sn and nuclear energy density functionals

The electric dipole strength distribution in 120Sn between 5 and 22 MeV has been determined at RCNP Osaka from a polarization transfer analysis of proton inelastic scattering at E_0 = 295 MeV and forward angles including 0{\deg}. Combined with photoabsorption data an electric dipole polarizability \alpha_D(120Sn) = 8.93(36) fm^3 is extracted. The dipole polarizability as isovector observable par excellence carries direct information on the nuclear symmetry energy and its density dependence. The correlation of the new value with the well established \alpha_D(208Pb) serves as a test of its prediction by nuclear energy density functionals (EDFs). Models based on modern Skyrme interactions describe the data fairly well while most calculations based on relativistic Hamiltonians cannot.Comment: 6 pages, 4 figure

Cis-regulatory evolution spotlights species differences in the adaptive potential of gene expression plasticity

Plasticity allows organisms to respond to environmental change. Here the authors compare the distribution of cis-regulatory variants in the transcriptomes of Arabidopsis lyrata and A. halleriafter exposure to stress, to trace the role of polygenic selection in the evolution of gene expression plasticity

Stochastic and Conditional Regulation of Nematode Mouth-Form Dimorphisms

Integrative research at the interphase between ecology, developmental, and evolutionary biology increasingly highlights the importance of phenotypic plasticity, the property of a single genotype to produce different phenotypes depending on environmental conditions. Plasticity occurs in multiple forms at the morphological, physiological, and behavioral levels. It can be reversible or irreversible, continuous or discrete, the latter also known as “polyphenism”. While plasticity has long been discussed as a concept of both, ecological and evolutionary significance, only recent experimental studies have begun providing insights into the associated molecular mechanisms. One promising system for genetic and molecular analyses of phenotypic plasticity is a feeding polyphenism in the nematode model organism Pristionchus pacificus. In this species, genetically identical nematodes can express two alternative mouth-forms, which are advantageous under different environmental conditions. Although the expression of these mouth-forms can be influenced by environment, even under fixed environmental conditions, genetically identical individuals of P. pacificus form both morphs. Thus, in addition to conditional regulation, mouth dimorphism in P. pacificus is regulated stochastically. Here, we discuss the importance of the stochastic regulation of the switch between alternative phenotypes and show that this characteristic provides a unique advantage for genetic, molecular, and experimental analyses. We then relate this stochasticity in mouth-form regulation to a similar phenomenon seen in bacteria, bistability, and finally discuss stochasticity as a bet-hedging mechanism for living in unpredictable environments

Natural sensory context drives diverse brain-wide activity during C. elegans mating

Neuronal activity traces and concurrent behavioral features. Susoy et al, 202

Evolutionarily conserved behavioral plasticity enables context-dependent mating in C. elegans

Tail morphology of plate-grown and liquid-grown C. elegans males. The dataset contains 2D positions of 45 landmarks and 48 semilandmarks of 104 C. elegans individuals. Two conditioning regimes were used: 1-grown on agar plates, 2-grown in liquid.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

Description of the bark beetle associated nematodes Micoletzkya masseyi n. sp. and M. japonica n. sp. (Nematoda: Diplogastridae)

Micoletzkya masseyi n. sp. and M. japonica n. sp. from bark beetles Orthotomicus caelatus and Dryocoetes uniseriatus, respectively, are described based on morphology and molecular data. Both species are gonochoristic and can be cultured monoxenically on bacteria. Micoletzkya masseyi n. sp. is differentiated from other species of the genus by a very short male tail, P6-P8 genital papillae arranged in a triangle and with P7 being closer to P8 than to P6, and a conoid female tail to a sharp terminus. Micoletzkya japonica n. sp. is distinct from other Micoletzkya species by the arrangement of its male papillae such that P6 and P7 are close to each other and P8 is positioned apart from them, a conoid male tail with a spicate terminus, and a small gubernaculum (ca 11 μm in length). Phylogeny of the genus was inferred using nucleotide sequences of 18S rRNA, 28S rRNA, COI, and two ribosomal protein genes. Biological data for the new species are presented and the associations between Micoletzkya species and bark beetles are discussed

Predatory feeding behaviour in Pristionchus nematodes is dependent on phenotypic plasticity and induced by serotonin

Behavioural innovation and morphological adaptation are intrinsically linked but their relationship is often poorly understood. In nematodes, a huge diversity of feeding morphologies and behaviours can be observed to meet their distinctive dietary and environmental demands. Pristionchus and their relatives show varied feeding activities, both consuming bacteria and also predating other nematodes. In addition, Pristionchus nematodes display dimorphic mouth structures triggered by an irreversible developmental switch, which generates a narrower mouthed form with a single tooth and a wider mouthed form with an additional tooth. However, little is known about the specific predatory adaptations of these mouth forms or the associated mechanisms and behaviours. Through a mechanistic analysis of predation behaviours, in particular in the model organism Pristionchus pacificus, we reveal multifaceted feeding modes characterised by dynamic rhythmic switching and tooth stimulation. This complex feeding mode switch is regulated by the neurotransmitter serotonin in a previously uncharacterised role, a process that appears conserved across several predatory nematode species. Furthermore, we investigated the effects of starvation, prey size and prey preference on P. pacificus predatory feeding kinetics, revealing predation to be a fundamental component of the P. pacificus feeding repertoire, thus providing an additional rich source of nutrition in addition to bacteria. Finally, we found that mouth form morphology also has a striking impact on predation, suppressing predatory behaviour in the narrow mouthed form. Our results therefore hint at the regulatory networks involved in controlling predatory feeding and underscore P. pacificus as a model for understanding the evolution of complex behaviours

Leptojacobus dorci n. gen., n. sp. (Nematoda: Diplogastridae), an Associate of Dorcus Stag Beetles (Coleoptera: Lucanidae)

A new species of diplogastrid nematode, Leptojacobus dorci n. gen., n. sp., was isolated from adults of the stag beetle Dorcus ritsemae (Coleoptera: Lucanidae) that were purchased from a pet shop in Japan. Leptojacobus n. gen. is circumscribed by a very thin, delicate body and by a small stoma with minute armature. A combination of other stomatal characters, namely the division of the cheilostom into adradial plates, the symmetry of the subventral stegostomatal sectors, and the presence of a thin, conical dorsal tooth, further distinguishes Leptojacobus n. gen. from other genera of Diplogastridae. Phylogenetic analysis of nearly full-length SSU rRNA sequences support the new species, together with an isolate identified previously as Koerneria luziae, to be excluded from a clade including all other molecularly characterized diplogastrids with teeth and stomatal dimorphism. Therefore, the new species will be of importance for reconstruction of ancestral character histories in Diplogastridae, a family circumscribed by a suite of feeding-related novelties