TY - THES AB - Social insects fight disease using their individual immune systems and the cooperative sanitary behaviors of colony members. These social defenses are well explored against externally-infecting pathogens, but little is known about defense strategies against internally-infecting pathogens, such as viruses. Viruses are ubiquitous and in the last decades it has become evident that also many ant species harbor viruses. We present one of the first studies addressing transmission dynamics and collective disease defenses against viruses in ants on a mechanistic level. I successfully established an experimental ant host – viral pathogen system as a model for the defense strategies used by social insects against internal pathogen infections, as outlined in the third chapter. In particular, we studied how garden ants (Lasius neglectus) defend themselves and their colonies against the generalist insect virus CrPV (cricket paralysis virus). We chose microinjections of virus directly into the ants’ hemolymph because it allowed us to use a defined exposure dose. Here we show that this is a good model system, as the virus is replicating and thus infecting the host. The ants mount a clear individual immune response against the viral infection, which is characterized by a specific siRNA pattern, namely siRNAs mapping against the viral genome with a peak of 21 and 22 bp long fragments. The onset of this immune response is consistent with the timeline of viral replication that starts already within two days post injection. The disease manifests in decreased survival over a course of two to three weeks. Regarding group living, we find that infected ants show a strong individual immune response, but that their course of disease is little affected by nestmate presence, as described in chapter four. Hence, we do not find social immunity in the context of viral infections in ants. Nestmates, however, can contract the virus. Using Drosophila S2R+ cells in culture, we showed that 94 % of the nestmates contract active virus within four days of social contact to an infected individual. Virus is transmitted in low doses, thus not causing disease transmission within the colony. While virus can be transmitted during short direct contacts, we also assume transmission from deceased ants and show that the nestmates’ immune system gets activated after contracting a low viral dose. We find considerable potential for indirect transmission via the nest space. Virus is shed to the nest, where it stays viable for one week and is also picked up by other ants. Apart from that, we want to underline the potential of ant poison as antiviral agent. We determined that ant poison successfully inactivates CrPV in vitro. However, we found no evidence for effective poison use to sanitize the nest space. On the other hand, local application of ant poison by oral poison uptake, which is part of the ants prophylactic behavioral repertoire, probably contributes to keeping the gut of each individual sanitized. We hypothesize that oral poison uptake might be the reason why we did not find viable virus in the trophallactic fluid. The fifth chapter encompasses preliminary data on potential social immunization. However, our experiments do not confirm an actual survival benefit for the nestmates upon pathogen challenge under the given experimental settings. Nevertheless, we do not want to rule out the possibility for nestmate immunization, but rather emphasize that considering different experimental timelines and viral doses would provide a multitude of options for follow-up experiments. In conclusion, we find that prophylactic individual behaviors, such as oral poison uptake, might play a role in preventing viral disease transmission. Compared to colony defense against external pathogens, internal pathogen infections require a stronger component of individual physiological immunity than behavioral social immunity, yet could still lead to collective protection. AU - Franschitz, Anna ID - 13984 SN - 2663 - 337X TI - Individual and social immunity against viral infections in ants ER - TY - JOUR AB - It has been known since Stefan Vogel's observations in 1969 that solitary female oil bees collect fatty floral oils from specialized oil-secreting plants with the aid of hairy patches on either their legs or abdomen, a reward used as food for their larvae and/or to line their brood cells. Similar adaptations are also known from male oil bees, although the purpose of their oil-collecting behavior has not yet been clarified. Here, we describe a novel pollination system involving male Paratetrapedia oil bees and the tropical herb Anthurium acutifolium. We present ultrastructural morphological details of bee and plant structures involved in this interaction and the composition of floral scents likely mediating pollinator attraction. Inflorescences of A. acutifolium were visited almost exclusively by male P. chocoensis oil bees. The bees mopped with a hairy patch of their abdominal sterna 3 across the inflorescence surface. During this activity on both staminate and pistillate stage inflorescences, bees’ abdomens and legs became loaded with pollen and contacted receptive stigmas. In contrast to what has been observed in other angiosperms visited for the collection of fatty floral oils, the inflorescences/flowers of A. acutifolium do not have structures specialized in oil secretion, i.e., elaiophores. These inflorescences, nonetheless, were strongly scented during the time interval they were visited by the bees. Gas chromatography/mass spectrometry (GC/MS) analyses of dynamic headspace floral samples revealed that inflorescences of both anthetic phases emitted scent bouquets consisting mainly of aliphatic esters, indole and uncommmon terpenoids (megastigmanes). Interestingly enough, our data suggest that the unusual floral scent of A. acutifolium is a perfume reward collected by male P. chocoensis oil bees. This pollination system thus bears a remarkable resemblence with the interactions between perfume-collecting male euglossine bees and their preferred flowers, discovered by Stefan Vogel half a century ago. AU - Etl, Florian AU - Franschitz, Anna AU - Aguiar, Antonio AU - Schönenberger, Jürg AU - Dötterl, Stefan ID - 695 JF - Flora: Morphology, Distribution, Functional Ecology of Plants SN - 03672530 TI - A perfume collecting male oil bee? Evidences of a novel pollination system involving Anthurium acutifolium Araceae and Paratetrapedia chocoensis Apidae Tapinotaspidini VL - 232 ER -