Acclimation in ants : interference of communication and waterproofing through cuticular hydrocarbons in a multifunctional trait

Organismal traits may experience conflicting selection pressures if they fulfil different functions simultaneously. This can require trade-offs between functions or alternatively functional separation between elements of the trait. An important multifunctional trait in insects is the cuticular hydrocarbon (CHC) layer. CHCs cover the body of nearly all insects, protect against desiccation and serve as a communication signal. In social insects like ants, they provide cues for nestmate recognition. To maintain their waterproofing function, insects have to adjust CHC composition to current temperatures. These changes might affect information content and interfere with communication, which would be especially detrimental in social insects. Here, we studied how acclimation affects nestmate recognition in two sister species of the ant genus Lasius. Colony fragments were exposed to three climate regimes. We analysed behaviour towards same and differently acclimated conspecifics, and determined which CHCs were related to acclimatory changes, colony differences and inter-individual aggression. Differential acclimation led to higher aggression and chemical distances among former nestmates. We identified small CHC subsets, which only differed among colonies or among acclimation treatments. Moreover, few compounds sufficed to explain inter-individual aggression, suggesting that ants do not use the entire CHC profile for nestmate recognition and that colony identity is encoded in a redundant way. Across individual CHCs, their contribution to colony differences and to differences among acclimatory treatments was negatively correlated, indicating that there is some degree of functional separation. However, CHC classes could not be clearly assigned to one or another function, indicating that the role of each CHC is idiosyncratic and may differ among species. Acclimatory effects and colony differences were more independent from each other in L. platythorax than in L. niger, indicating that functional separation can differ even among sister species. Our results show that CHC functions are more intertwined than previously assumed, suggesting that insects cannot optimise all functions independently. The main constraint might be the need to maintain a certain phase behaviour of the CHC layer, which depends on CHC composition and affects functionality. The need to separate functions might depend on species-specific ecological and life-history parameters

Measuring specialization in species interaction networks

BACKGROUND: Network analyses of plant-animal interactions hold valuable biological information. They are often used to quantify the degree of specialization between partners, but usually based on qualitative indices such as 'connectance' or number of links. These measures ignore interaction frequencies or sampling intensity, and strongly depend on network size. RESULTS: Here we introduce two quantitative indices using interaction frequencies to describe the degree of specialization, based on information theory. The first measure (d') describes the degree of interaction specialization at the species level, while the second measure (H(2)') characterizes the degree of specialization or partitioning among two parties in the entire network. Both indices are mathematically related and derived from Shannon entropy. The species-level index d' can be used to analyze variation within networks, while H(2)' as a network-level index is useful for comparisons across different interaction webs. Analyses of two published pollinator networks identified differences and features that have not been detected with previous approaches. For instance, plants and pollinators within a network differed in their average degree of specialization (weighted mean d'), and the correlation between specialization of pollinators and their relative abundance also differed between the webs. Rarefied sampling effort in both networks and null model simulations suggest that H(2)' is not affected by network size or sampling intensity. CONCLUSION: Quantitative analyses reflect properties of interaction networks more appropriately than previous qualitative attempts, and are robust against variation in sampling intensity, network size and symmetry. These measures will improve our understanding of patterns of specialization within and across networks from a broad spectrum of biological interactions

Tropical parabiotic ants: Highly unusual cuticular substances and low interspecific discrimination

<p>Abstract</p> <p>Background</p> <p>Associations between animal species require that at least one of the species recognizes its partner. Parabioses are associations of two ant species which co-inhabit the same nest. Ants usually possess an elaborate nestmate recognition system, which is based on cuticular hydrocarbons and allows them to distinguish nestmates from non-nestmates through quantitative or qualitative differences in the hydrocarbon composition. Hence, living in a parabiotic association probably necessitates changes of the nestmate recognition system in both species, since heterospecific ants have to be accepted as nestmates.</p> <p>Results</p> <p>In the present study we report highly unusual cuticular profiles in the parabiotic species <it>Crematogaster modiglianii </it>and <it>Camponotus rufifemur </it>from the tropical rainforest of Borneo. The cuticle of both species is covered by a set of steroids, which are highly unusual surface compounds. They also occur in the Dufour gland of <it>Crematogaster modiglianii </it>in high quantities. The composition of these steroids differed between colonies but was highly similar among the two species of a parabiotic nest. In contrast, hydrocarbon composition of <it>Cr. modiglianii </it>and <it>Ca. rufifemur </it>differed strongly and only overlapped in three regularly occurring and three trace compounds. The hydrocarbon profile of <it>Camponotus rufifemur </it>consisted almost exclusively of methyl-branched alkenes of unusually high chain lengths (up to C₄₉). This species occurred in two sympatric, chemically distinct varieties with almost no hydrocarbons in common. <it>Cr. modiglianii </it>discriminated between these two varieties. It only tolerated workers of the <it>Ca. rufifemur </it>variety it was associated with, but attacked the respective others. However, <it>Cr. modiglianii </it>did not distinguish its own <it>Ca. rufifemur </it>partner from allocolonial <it>Ca. rufifemur </it>workers of the same variety.</p> <p>Conclusion</p> <p>We conclude that there is a mutual substance transfer between <it>Cr. modiglianii </it>and <it>Ca. rufifemur</it>. <it>Ca. rufifemur </it>actively or passively acquires cuticular steroids from its <it>Cr. modiglianii </it>partner, while the latter acquires at least two cuticular hydrocarbons from <it>Ca. rufifemur</it>. The cuticular substances of both species are highly unusual regarding both substance classes and chain lengths, which may cause the apparent inability of <it>Cr. modiglianii </it>to discriminate <it>Ca. rufifemur </it>nestmates from allocolonial <it>Ca. rufifemur </it>workers of the same chemical variety.</p

Synthesen und Prozessentwicklung zur radioaktiven [18F]Fluorierung von PET-Tracern via Flow-Chemie

Flow-Chemie gilt als eine der modernsten und vielversprechendsten Synthesemethoden der Neuzeit. Vor allem die Industrie macht sich ihre Vorteile schon seit einigen Jahren zu eigen. In universitären Forschungseinrichtungen fehlt jedoch preisgünstiges und flexibel einsetzbares Equipment, um diese Art der Forschung attraktiv zu gestalten. Ein wichtiges Forschungsgebiet, bei dem die Vorteile von flexibel einsetzbaren und zuverlässig automatisierten Flow-Prozessen zur Geltung kommt, ist die Radiochemie. Diese beschäftigt sich unter anderem mit der Synthese von radioaktiven Krebsmarkern, sogenannten PET-Tracern (positron emission tomography), welche sowohl in der Diagnostik als auch in der Therapie eingesetzt werden. Als Marker dienen radioaktive Isotope wie 18F, 11C oder 64Cu. Diese Arbeit befasst sich mit den wichtigsten Aspekten, die für eine erfolgreiche, automatisierte PET-Synthese notwendig sind. Das beinhaltet die Konstruktion und Entwicklung von Laborequipment, die Synthese neuer Precursor, dem Labeling dieser, der Automatisierung der Synthesen, sowie die in-vivo und in-vitro pharmakokinetische Auswertung im Mausmodell. Die Entwicklung des Flow-Systems fokussiert sich hauptsächlich auf die Kernkomponenten, dem Flow-Reaktor, der Spritzenpumpe, dem Drucksensor, sowie dem Druckregulator. Vor allem die Geometrie des Flow-Reaktors spielt eine entscheidende Rolle für die Effizienz der Synthese. Aus diesem Grund wurden unterschiedlicher Geometrien designt, mit Hilfe von 3D-Druck-Technologie umgesetzt und untersucht. Als Reaktormaterial dient dabei PEEK (polyetheretherketone), welches sich Aufgrund seiner thermischen und chemischen Resistenz hervorragend dafür eignet. Zur Evaluierung des Flow-Systems und als „Proof of Concept“ konnte ein Prozess für [18F]Fluordeoxyglucose ([18F]FDG), dem wohl erfolgreichsten PET-Tracer, entwickelt werden. Eine große Herausforderung bei der Synthese mit nukleophilen [18F]Fluorid, stellt die Trocknung des [18F]Fluorids dar. Um diesen Schritt sicherer und effektiver zu gestalten, wurde ein eigenständiges Modul entwickelt, welches die azeotrope Trocknung des wässrigen [18F]Fluorid umgeht. Als Grundlage dient dabei die Darstellung von [18F]Triflylfluorid, einem radioaktiven Gas, welches durch Trocknungskartuschen geleitet und anschließend in wasserfreies [18F]KF überführt wird. Des Weiteren konnte ein neuer, auf β-Galactose basierender Tracer ([18F]FGal-Al), synthetisiert werden. Aufgrund der hohen Strahlenbelastung bei der Synthese wurde dafür ein automatisierter Prozess auf einem kommerziell erhältlichen Synthesemodul (FN X Pro, Tracerlab) entwickelt. Der Tracer wurde im Anschluss sowohl im in-vitro als auch im in-vivo Mausmodell an hepatozellulären Karzinomzellen (AMp19-Tumorzellen), welche zuvor mit CMX-5461 behandelt wurden, getestet

Toward a Metric Catalog for Large-Scale Agile Development

Nowadays, organizations use agile software development to remain competitive in their frequently changing business environment. Inspired by the success of agile methods on a small scale, organizations have started to apply them in larger contexts. However, the limited scalability of agile methods is a problem. Metrics can be a success factor for achieving agility at scale, thus adopting them is promising. Most scaling agile frameworks provide few recommendations regarding metrics. Likewise, research on metrics in large-scale agile development lacks concrete guidance for metrics or their organization-specific adoption. To fill this gap, we propose two artifacts. We present the design of a minimalistic metric management fact sheet (MMFS) for large-scale agile development to support practitioners in using metrics in their organization-specific development environment. Furthermore, the MMFS is the basis for our metric catalog documenting 196 metrics identified in an expert study to provide a comprehensive metric set for scaling agile environments

The chemistry of competition: exploitation of heterospecific cues in ants

This article is reproduced from the previous edition, volume 22, pp. 14879–14882, © 2001, Elsevier Ltd

Mechanical Adaptive Silicone Composites for UV-triggered Facilitated Cochlear-Implant Removal

The removal of the cochlear implant (CI), which in some cases is without alternative, is still an act of simple pulling, not only causing harm for the patient by damaging tissue but also making reimplantation more difficult. For that reason, it is necessary to develop mechanisms to make an explantation easier. To overcome this problem adaption of the mechanical properties by light-degradable periodic mesoporous organosilica (PMO) can be one solution. By introducing PMO nanoparticles into the CI's silicone matrix, the particles act as a stiffening agent, which can be degraded by irradiation with UV light. Using this mechanism, the silicone becomes softer, thus making explantation easier and safer for patients. Here first results, concerning the creation of a silicone composite material with light-sensitive adaptive mechanical properties are reported

Interactions of ants with native and invasive lady beetles and the role of chemical cues in intraguild interference

The predator-predator naivete hypothesis suggests that non-native predators benefit from being unknown to native predators, resulting in reduced intraguild interference with native predators. This novelty advantage should depend on the ability of native predators to recognize cues of non-native predators. Here, we compared ant aggression and lady beetle reaction in four native and the invasive lady beetle species Harmonia axyridis. In addition, we tested whether lady beetle cuticular hydrocarbons (CHCs) are involved in species recognition, which might explain naivete if the invasive species has a specific CHC profile. To this end, we conducted behavioral assays confronting two native ant species with both living lady beetles and lady beetle elytra bearing or lacking CHCs of different lady beetle species. Finally, we characterized CHC profiles of the lady beetles using GC-MS. In general, the aggression of Lasius niger was more frequent than that of Myrmica rubra and L. niger aggression was more frequent towards most native lady beetle species compared to H. axyridis. The removal of CHCs from lady beetle elytra reduced aggression of both ant species. If CHCs of respective lady beetle species were added on cue-free elytra, natural strength of L. niger aggression could be restored. CHC analyses revealed a distinct cue composition for each lady beetle species. Our experiments demonstrate that the presence of chemical cues on the surface of lady beetles contribute to the strength of ant aggression against lady beetles. Reduced aggression of L. niger towards H. axyridis and reduced avoidance behavior in H. axyridis compared to the equally voracious C. septempunctata might improve the invasive lady beetle's access to ant-tended aphids