@article{13127, abstract = {Cooperative disease defense emerges as group-level collective behavior, yet how group members make the underlying individual decisions is poorly understood. Using garden ants and fungal pathogens as an experimental model, we derive the rules governing individual ant grooming choices and show how they produce colony-level hygiene. Time-resolved behavioral analysis, pathogen quantification, and probabilistic modeling reveal that ants increase grooming and preferentially target highly-infectious individuals when perceiving high pathogen load, but transiently suppress grooming after having been groomed by nestmates. Ants thus react to both, the infectivity of others and the social feedback they receive on their own contagiousness. While inferred solely from momentary ant decisions, these behavioral rules quantitatively predict hour-long experimental dynamics, and synergistically combine into efficient colony-wide pathogen removal. Our analyses show that noisy individual decisions based on only local, incomplete, yet dynamically-updated information on pathogen threat and social feedback can lead to potent collective disease defense.}, author = {Casillas Perez, Barbara E and Bod'Ová, Katarína and Grasse, Anna V and Tkačik, Gašper and Cremer, Sylvia}, issn = {2041-1723}, journal = {Nature Communications}, publisher = {Springer Nature}, title = {{Dynamic pathogen detection and social feedback shape collective hygiene in ants}}, doi = {10.1038/s41467-023-38947-y}, volume = {14}, year = {2023}, } @phdthesis{13984, abstract = {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.}, author = {Franschitz, Anna}, isbn = {978-3-99078-034-3}, issn = {2663-337X}, pages = {89}, publisher = {Institute of Science and Technology Austria}, title = {{Individual and social immunity against viral infections in ants}}, doi = {10.15479/at:ista:13984}, year = {2023}, } @article{12133, abstract = {Social distancing is an effective way to prevent the spread of disease in societies, whereas infection elimination is a key element of organismal immunity. Here, we discuss how the study of social insects such as ants — which form a superorganism of unconditionally cooperative individuals and thus represent a level of organization that is intermediate between a classical society of individuals and an organism of cells — can help to determine common principles of disease defence across levels of organization.}, author = {Cremer, Sylvia and Sixt, Michael K}, issn = {1474-1741}, journal = {Nature Reviews Immunology}, keywords = {Energy Engineering and Power Technology, Fuel Technology}, number = {12}, pages = {713--714}, publisher = {Springer Nature}, title = {{Principles of disease defence in organisms, superorganisms and societies}}, doi = {10.1038/s41577-022-00797-y}, volume = {22}, year = {2022}, } @article{10284, abstract = {Infections early in life can have enduring effects on an organism's development and immunity. In this study, we show that this equally applies to developing ‘superorganisms’––incipient social insect colonies. When we exposed newly mated Lasius niger ant queens to a low pathogen dose, their colonies grew more slowly than controls before winter, but reached similar sizes afterwards. Independent of exposure, queen hibernation survival improved when the ratio of pupae to workers was small. Queens that reared fewer pupae before worker emergence exhibited lower pathogen levels, indicating that high brood rearing efforts interfere with the ability of the queen's immune system to suppress pathogen proliferation. Early-life queen pathogen exposure also improved the immunocompetence of her worker offspring, as demonstrated by challenging the workers to the same pathogen a year later. Transgenerational transfer of the queen's pathogen experience to her workforce can hence durably reduce the disease susceptibility of the whole superorganism.}, author = {Casillas Perez, Barbara E and Pull, Christopher and Naiser, Filip and Naderlinger, Elisabeth and Matas, Jiri and Cremer, Sylvia}, issn = {1461-0248}, journal = {Ecology Letters}, number = {1}, pages = {89--100}, publisher = {Wiley}, title = {{Early queen infection shapes developmental dynamics and induces long-term disease protection in incipient ant colonies}}, doi = {10.1111/ele.13907}, volume = {25}, year = {2022}, } @phdthesis{10727, abstract = {Social insects are a common model to study disease dynamics in social animals. Even though pathogens should thrive in social insect colonies as the hosts engage in frequent social interactions, are closely related and live in a pathogen-rich environment, disease outbreaks are rare. This is because social insects have evolved mechanisms to keep pathogens at bay – and fight disease as a collective. Social insect colonies are often viewed as “superorganisms” with division of labor between reproductive “germ-like” queens and males and “somatic” workers, which together form an interdependent reproductive unit that parallels a multicellular body. Superorganisms possess a “social immune system” that comprises of collective disease defenses performed by the workers - summarized as “social immunity”. In social groups immunization (reduced susceptibility to a parasite upon secondary exposure to the same parasite) can e.g. be triggered by social interactions (“social immunization”). Social immunization can be caused by (i) asymptomatic low-level infections that are acquired during caregiving to a contagious individual that can give an immune boost, which can induce protection upon later encounter with the same pathogen (active immunization) or (ii) by transfer of immune effectors between individuals (passive immunization). In the second chapter, I built up on a study that I co-authored that found that low-level infections can not only be protective, but also be costly and make the host more susceptible to detrimental superinfections after contact to a very dissimilar pathogen. I here now tested different degrees of phylogenetically-distant fungal strains of M. brunneum and M. robertsii in L. neglectus and can describe the occurrence of cross-protection of social immunization if the first and second pathogen are from the same level. Interestingly, low-level infections only provided protection when the first strain was less virulent than the second strain and elicited higher immune gene expression. In the third and fourth chapters, I expanded on the role of social immunity in sexual selection, a so far unstudied field. I used the fungus Metarhizium robertsii and the ant Cardiocondyla obscurior as a model, as in this species mating occurs in the presence of workers and can be studied under laboratory conditions. Before males mate with virgin queens in the nest they engage in fierce combat over the access to their mating partners. First, I focused on male-male competition in the third chapter and found that fighting with a contagious male is costly as it can lead to contamination of the rival, but that workers can decrease the risk of disease contraction by performing sanitary care. In the fourth chapter, I studied the effect of fungal infection on survival and mating success of sexuals (freshly emerged queens and males) and found that worker-performed sanitary care can buffer the negative effect that a pathogenic contagion would have on sexuals by spore removal from the exposed individuals. When social immunity was prevented and queens could contract spores from their mating partner, very low dosages led to negative consequences: their lifespan was reduced and they produced fewer offspring with poor immunocompetence compared to healthy queens. Interestingly, cohabitation with a late-stage infected male where no spore transfer was possible had a positive effect on offspring immunity – male offspring of mothers that apparently perceived an infected partner in their vicinity reacted more sensitively to fungal challenge than male offspring without paternal pathogen history.}, author = {Metzler, Sina}, issn = {2663-337X}, publisher = {Institute of Science and Technology Austria}, title = {{Pathogen-mediated sexual selection and immunization in ant colonies}}, doi = {10.15479/AT:ISTA:10727}, year = {2022}, } @misc{13061, abstract = {Infections early in life can have enduring effects on an organism’s development and immunity. In this study, we show that this equally applies to developing “superorganisms” – incipient social insect colonies. When we exposed newly mated Lasius niger ant queens to a low pathogen dose, their colonies grew more slowly than controls before winter, but reached similar sizes afterwards. Independent of exposure, queen hibernation survival improved when the ratio of pupae to workers was small. Queens that reared fewer pupae before worker emergence exhibited lower pathogen levels, indicating that high brood rearing efforts interfere with the ability of the queen’s immune system to suppress pathogen proliferation. Early-life queen pathogen-exposure also improved the immunocompetence of her worker offspring, as demonstrated by challenging the workers to the same pathogen a year later. Transgenerational transfer of the queen’s pathogen experience to her workforce can hence durably reduce the disease susceptibility of the whole superorganism.}, author = {Casillas Perez, Barbara E and Pull, Christopher and Naiser, Filip and Naderlinger, Elisabeth and Matas, Jiri and Cremer, Sylvia}, publisher = {Dryad}, title = {{Early queen infection shapes developmental dynamics and induces long-term disease protection in incipient ant colonies}}, doi = {10.5061/DRYAD.7PVMCVDTJ}, year = {2021}, } @article{10568, abstract = {Genetic adaptation and phenotypic plasticity facilitate the migration into new habitats and enable organisms to cope with a rapidly changing environment. In contrast to genetic adaptation that spans multiple generations as an evolutionary process, phenotypic plasticity allows acclimation within the life-time of an organism. Genetic adaptation and phenotypic plasticity are usually studied in isolation, however, only by including their interactive impact, we can understand acclimation and adaptation in nature. We aimed to explore the contribution of adaptation and plasticity in coping with an abiotic (salinity) and a biotic (Vibrio bacteria) stressor using six different populations of the broad-nosed pipefish Syngnathus typhle that originated from either high [14–17 Practical Salinity Unit (PSU)] or low (7–11 PSU) saline environments along the German coastline of the Baltic Sea. We exposed wild caught animals, to either high (15 PSU) or low (7 PSU) salinity, representing native and novel salinity conditions and allowed animals to mate. After male pregnancy, offspring was split and each half was exposed to one of the two salinities and infected with Vibrio alginolyticus bacteria that were evolved at either of the two salinities in a fully reciprocal design. We investigated life-history traits of fathers and expression of 47 target genes in mothers and offspring. Pregnant males originating from high salinity exposed to low salinity were highly susceptible to opportunistic fungi infections resulting in decreased offspring size and number. In contrast, no signs of fungal infection were identified in fathers originating from low saline conditions suggesting that genetic adaptation has the potential to overcome the challenges encountered at low salinity. Offspring from parents with low saline origin survived better at low salinity suggesting genetic adaptation to low salinity. In addition, gene expression analyses of juveniles indicated patterns of local adaptation, trans-generational plasticity and developmental plasticity. In conclusion, our study suggests that pipefish are locally adapted to the low salinity in their environment, however, they are retaining phenotypic plasticity, which allows them to also cope with ancestral salinity levels and prevailing pathogens.}, author = {Goehlich, Henry and Sartoris, Linda and Wagner, Kim-Sara and Wendling, Carolin C. and Roth, Olivia}, issn = {2296-701X}, journal = {Frontiers in Ecology and Evolution}, keywords = {ecology, evolution, behavior and systematics, trans-generational plasticity, genetic adaptation, local adaptation, phenotypic plasticity, Baltic Sea, climate change, salinity, syngnathids}, publisher = {Frontiers Media}, title = {{Pipefish locally adapted to low salinity in the Baltic Sea retain phenotypic plasticity to cope with ancestral salinity levels}}, doi = {10.3389/fevo.2021.626442}, volume = {9}, year = {2021}, } @article{10569, abstract = {For animals to survive until reproduction, it is crucial that juveniles successfully detect potential predators and respond with appropriate behavior. The recognition of cues originating from predators can be innate or learned. Cues of various modalities might be used alone or in multi-modal combinations to detect and distinguish predators but studies investigating multi-modal integration in predator avoidance are scarce. Here, we used wild, naive tadpoles of the Neotropical poison frog Allobates femoralis ( Boulenger, 1884) to test their reaction to cues with two modalities from two different sympatrically occurring potential predators: heterospecific predatory Dendrobates tinctorius tadpoles and dragonfly larvae. We presented A. femoralis tadpoles with olfactory or visual cues, or a combination of the two, and compared their reaction to a water control in a between-individual design. In our trials, A. femoralis tadpoles reacted to multi-modal stimuli (a combination of visual and chemical information) originating from dragonfly larvae with avoidance but showed no reaction to uni-modal cues or cues from heterospecific tadpoles. In addition, visual cues from conspecifics increased swimming activity while cues from predators had no effect on tadpole activity. Our results show that A. femoralis tadpoles can innately recognize some predators and probably need both visual and chemical information to effectively avoid them. This is the first study looking at anti-predator behavior in poison frog tadpoles. We discuss how parental care might influence the expression of predator avoidance responses in tadpoles.}, author = {Szabo, B and Mangione, R and Rath, M and Pašukonis, A and Reber, SA and Oh, Jinook and Ringler, M and Ringler, E}, issn = {1477-9145}, journal = {Journal of Experimental Biology}, number = {24}, publisher = {The Company of Biologists}, title = {{Naïve poison frog tadpoles use bi-modal cues to avoid insect predators but not heterospecific predatory tadpoles}}, doi = {10.1242/jeb.243647}, volume = {224}, year = {2021}, } @article{9101, abstract = {Behavioral predispositions are innate tendencies of animals to behave in a given way without the input of learning. They increase survival chances and, due to environmental and ecological challenges, may vary substantially even between closely related taxa. These differences are likely to be especially pronounced in long-lived species like crocodilians. This order is particularly relevant for comparative cognition due to its phylogenetic proximity to birds. Here we compared early life behavioral predispositions in two Alligatoridae species. We exposed American alligator and spectacled caiman hatchlings to three different novel situations: a novel object, a novel environment that was open and a novel environment with a shelter. This was then repeated a week later. During exposure to the novel environments, alligators moved around more and explored a larger range of the arena than the caimans. When exposed to the novel object, the alligators reduced the mean distance to the novel object in the second phase, while the caimans further increased it, indicating diametrically opposite ontogenetic development in behavioral predispositions. Although all crocodilian hatchlings face comparable challenges, e.g., high predation pressure, the effectiveness of parental protection might explain the observed pattern. American alligators are apex predators capable of protecting their offspring against most dangers, whereas adult spectacled caimans are frequently predated themselves. Their distancing behavior might be related to increased predator avoidance and also explain the success of invasive spectacled caimans in the natural habitats of other crocodilians.}, author = {Reber, Stephan A. and Oh, Jinook and Janisch, Judith and Stevenson, Colin and Foggett, Shaun and Wilkinson, Anna}, issn = {1435-9456}, journal = {Animal Cognition}, number = {4}, pages = {753--764}, publisher = {Springer Nature}, title = {{Early life differences in behavioral predispositions in two Alligatoridae species}}, doi = {10.1007/s10071-020-01461-5}, volume = {24}, year = {2021}, } @misc{13060, abstract = {Coinfections with multiple pathogens can result in complex within-host dynamics affecting virulence and transmission. Whilst multiple infections are intensively studied in solitary hosts, it is so far unresolved how social host interactions interfere with pathogen competition, and if this depends on coinfection diversity. We studied how the collective disease defenses of ants – their social immunity ­– influence pathogen competition in coinfections of same or different fungal pathogen species. Social immunity reduced virulence for all pathogen combinations, but interfered with spore production only in different-species coinfections. Here, it decreased overall pathogen sporulation success, whilst simultaneously increasing co-sporulation on individual cadavers and maintaining a higher pathogen diversity at the community-level. Mathematical modeling revealed that host sanitary care alone can modulate competitive outcomes between pathogens, giving advantage to fast-germinating, thus less grooming-sensitive ones. Host social interactions can hence modulate infection dynamics in coinfected group members, thereby altering pathogen communities at the host- and population-level.}, author = {Milutinovic, Barbara and Stock, Miriam and Grasse, Anna V and Naderlinger, Elisabeth and Hilbe, Christian and Cremer, Sylvia}, publisher = {Dryad}, title = {{Social immunity modulates competition between coinfecting pathogens}}, doi = {10.5061/DRYAD.CRJDFN318}, year = {2020}, } @inbook{9096, author = {Schmid-Hempel, Paul and Cremer, Sylvia M}, booktitle = {Encyclopedia of Social Insects}, editor = {Starr, C}, isbn = {9783319903064}, publisher = {Springer Nature}, title = {{Parasites and Pathogens}}, doi = {10.1007/978-3-319-90306-4_94-1}, year = {2020}, } @article{7343, abstract = {Coinfections with multiple pathogens can result in complex within‐host dynamics affecting virulence and transmission. While multiple infections are intensively studied in solitary hosts, it is so far unresolved how social host interactions interfere with pathogen competition, and if this depends on coinfection diversity. We studied how the collective disease defences of ants – their social immunity – influence pathogen competition in coinfections of same or different fungal pathogen species. Social immunity reduced virulence for all pathogen combinations, but interfered with spore production only in different‐species coinfections. Here, it decreased overall pathogen sporulation success while increasing co‐sporulation on individual cadavers and maintaining a higher pathogen diversity at the community level. Mathematical modelling revealed that host sanitary care alone can modulate competitive outcomes between pathogens, giving advantage to fast‐germinating, thus less grooming‐sensitive ones. Host social interactions can hence modulate infection dynamics in coinfected group members, thereby altering pathogen communities at the host level and population level.}, author = {Milutinovic, Barbara and Stock, Miriam and Grasse, Anna V and Naderlinger, Elisabeth and Hilbe, Christian and Cremer, Sylvia}, issn = {1461-0248}, journal = {Ecology Letters}, number = {3}, pages = {565--574}, publisher = {Wiley}, title = {{Social immunity modulates competition between coinfecting pathogens}}, doi = {10.1111/ele.13458}, volume = {23}, year = {2020}, } @article{7490, abstract = {In plants, clathrin mediated endocytosis (CME) represents the major route for cargo internalisation from the cell surface. It has been assumed to operate in an evolutionary conserved manner as in yeast and animals. Here we report characterisation of ultrastructure, dynamics and mechanisms of plant CME as allowed by our advancement in electron microscopy and quantitative live imaging techniques. Arabidopsis CME appears to follow the constant curvature model and the bona fide CME population generates vesicles of a predominantly hexagonal-basket type; larger and with faster kinetics than in other models. Contrary to the existing paradigm, actin is dispensable for CME events at the plasma membrane but plays a unique role in collecting endocytic vesicles, sorting of internalised cargos and directional endosome movement that itself actively promote CME events. Internalized vesicles display a strongly delayed and sequential uncoating. These unique features highlight the independent evolution of the plant CME mechanism during the autonomous rise of multicellularity in eukaryotes.}, author = {Narasimhan, Madhumitha and Johnson, Alexander J and Prizak, Roshan and Kaufmann, Walter and Tan, Shutang and Casillas Perez, Barbara E and Friml, Jiří}, issn = {2050-084X}, journal = {eLife}, publisher = {eLife Sciences Publications}, title = {{Evolutionarily unique mechanistic framework of clathrin-mediated endocytosis in plants}}, doi = {10.7554/eLife.52067}, volume = {9}, year = {2020}, } @article{6105, abstract = { Hosts can alter their strategy towards pathogens during their lifetime; that is, they can show phenotypic plasticity in immunity or life history. Immune priming is one such example, where a previous encounter with a pathogen confers enhanced protection upon secondary challenge, resulting in reduced pathogen load (i.e., resistance) and improved host survival. However, an initial encounter might also enhance tolerance, particularly to less virulent opportunistic pathogens that establish persistent infections. In this scenario, individuals are better able to reduce the negative fecundity consequences that result from a high pathogen burden. Finally, previous exposure may also lead to life‐history adjustments, such as terminal investment into reproduction. Using different Drosophila melanogaster host genotypes and two bacterial pathogens, Lactococcus lactis and Pseudomonas entomophila, we tested whether previous exposure results in resistance or tolerance and whether it modifies immune gene expression during an acute‐phase infection (one day post‐challenge). We then asked whether previous pathogen exposure affects chronic‐phase pathogen persistence and longer‐term survival (28 days post‐challenge). We predicted that previous exposure would increase host resistance to an early stage bacterial infection while it might come at a cost to host fecundity tolerance. We reasoned that resistance would be due in part to stronger immune gene expression after challenge. We expected that previous exposure would improve long‐term survival, that it would reduce infection persistence, and we expected to find genetic variation in these responses. We found that previous exposure to P. entomophila weakened host resistance to a second infection independent of genotype and had no effect on immune gene expression. Fecundity tolerance showed genotypic variation but was not influenced by previous exposure. However, L. lactis persisted as a chronic infection, whereas survivors cleared the more pathogenic P. entomophila infection. To our knowledge, this is the first study that addresses host tolerance to bacteria in relation to previous exposure, taking a multi‐faceted approach to address the topic. Our results suggest that previous exposure comes with transient costs to resistance during the early stage of infection in this host–pathogen system and that infection persistence may be bacterium‐specific. }, author = {Kutzer, Megan and Kurtz, Joachim and Armitage, Sophie A.O.}, issn = {1365-2656}, journal = {Journal of Animal Ecology}, number = {4}, pages = {566--578}, publisher = {Wiley}, title = {{A multi-faceted approach testing the effects of previous bacterial exposure on resistance and tolerance}}, doi = {10.1111/1365-2656.12953}, volume = {88}, year = {2019}, } @article{6415, abstract = {Ant invasions are often harmful to native species communities. Their pathogens and host disease defense mechanisms may be one component of their devastating success. First, they can introduce harmful diseases to their competitors in the introduced range, to which they themselves are tolerant. Second, their supercolonial social structure of huge multi-queen nest networks means that they will harbor a broad pathogen spectrum and high pathogen load while remaining resilient, unlike the smaller, territorial colonies of the native species. Thus, it is likely that invasive ants act as a disease reservoir, promoting their competitive advantage and invasive success.}, author = {Cremer, Sylvia}, issn = {2214-5753}, journal = {Current Opinion in Insect Science}, pages = {63--68}, publisher = {Elsevier}, title = {{Pathogens and disease defense of invasive ants}}, doi = {10.1016/j.cois.2019.03.011}, volume = {33}, year = {2019}, } @misc{9806, abstract = {1. Hosts can alter their strategy towards pathogens during their lifetime, i.e., they can show phenotypic plasticity in immunity or life history. Immune priming is one such example, where a previous encounter with a pathogen confers enhanced protection upon secondary challenge, resulting in reduced pathogen load (i.e. resistance) and improved host survival. However, an initial encounter might also enhance tolerance, particularly to less virulent opportunistic pathogens that establish persistent infections. In this scenario, individuals are better able to reduce the negative fitness consequences that result from a high pathogen load. Finally, previous exposure may also lead to life history adjustments, such as terminal investment into reproduction. 2. Using different Drosophila melanogaster host genotypes and two bacterial pathogens, Lactococcus lactis and Pseudomonas entomophila, we tested if previous exposure results in resistance or tolerance and whether it modifies immune gene expression during an acute-phase infection (one day post-challenge). We then asked if previous pathogen exposure affects chronic-phase pathogen persistence and longer-term survival (28 days post-challenge). 3. We predicted that previous exposure would increase host resistance to an early stage bacterial infection while it might come at a cost to host fecundity tolerance. We reasoned that resistance would be due in part to stronger immune gene expression after challenge. We expected that previous exposure would improve long-term survival, that it would reduce infection persistence, and we expected to find genetic variation in these responses. 4. We found that previous exposure to P. entomophila weakened host resistance to a second infection independent of genotype and had no effect on immune gene expression. Fecundity tolerance showed genotypic variation but was not influenced by previous exposure. However, L. lactis persisted as a chronic infection, whereas survivors cleared the more pathogenic P. entomophila infection. 5. To our knowledge, this is the first study that addresses host tolerance to bacteria in relation to previous exposure, taking a multi-faceted approach to address the topic. Our results suggest that previous exposure comes with transient costs to resistance during the early stage of infection in this host-pathogen system and that infection persistence may be bacterium-specific.}, author = {Kutzer, Megan and Kurtz, Joachim and Armitage, Sophie A.O.}, publisher = {Dryad}, title = {{Data from: A multi-faceted approach testing the effects of previous bacterial exposure on resistance and tolerance}}, doi = {10.5061/dryad.9kj41f0}, year = {2019}, } @article{6552, abstract = {When animals become sick, infected cells and an armada of activated immune cells attempt to eliminate the pathogen from the body. Once infectious particles have breached the body's physical barriers of the skin or gut lining, an initially local response quickly escalates into a systemic response, attracting mobile immune cells to the site of infection. These cells complement the initial, unspecific defense with a more specialized, targeted response. This can also provide long-term immune memory and protection against future infection. The cell-autonomous defenses of the infected cells are thus aided by the actions of recruited immune cells. These specialized cells are the most mobile cells in the body, constantly patrolling through the otherwise static tissue to detect incoming pathogens. Such constant immune surveillance means infections are noticed immediately and can be rapidly cleared from the body. Some immune cells also remove infected cells that have succumbed to infection. All this prevents pathogen replication and spread to healthy tissues. Although this may involve the sacrifice of some somatic tissue, this is typically replaced quickly. Particular care is, however, given to the reproductive organs, which should always remain disease free (immune privilege). }, author = {Cremer, Sylvia}, issn = {09609822}, journal = {Current Biology}, number = {11}, pages = {R458--R463}, publisher = {Elsevier}, title = {{Social immunity in insects}}, doi = {10.1016/j.cub.2019.03.035}, volume = {29}, year = {2019}, } @inbook{7513, abstract = {Social insects (i.e., ants, termites and the social bees and wasps) protect their colonies from disease using a combination of individual immunity and collectively performed defenses, termed social immunity. The first line of social immune defense is sanitary care, which is performed by colony members to protect their pathogen-exposed nestmates from developing an infection. If sanitary care fails and an infection becomes established, a second line of social immune defense is deployed to stop disease transmission within the colony and to protect the valuable queens, which together with the males are the reproductive individuals of the colony. Insect colonies are separated into these reproductive individuals and the sterile worker force, forming a superorganismal reproductive unit reminiscent of the differentiated germline and soma in a multicellular organism. Ultimately, the social immune response preserves the germline of the superorganism insect colony and increases overall fitness of the colony in case of disease. }, author = {Cremer, Sylvia and Kutzer, Megan}, booktitle = {Encyclopedia of Animal Behavior}, editor = {Choe, Jae}, isbn = {9780128132517}, pages = {747--755}, publisher = {Elsevier}, title = {{Social immunity}}, doi = {10.1016/B978-0-12-809633-8.90721-0}, year = {2019}, } @phdthesis{6435, abstract = {Social insect colonies tend to have numerous members which function together like a single organism in such harmony that the term ``super-organism'' is often used. In this analogy the reproductive caste is analogous to the primordial germ cells of a metazoan, while the sterile worker caste corresponds to somatic cells. The worker castes, like tissues, are in charge of all functions of a living being, besides reproduction. The establishment of new super-organismal units (i.e. new colonies) is accomplished by the co-dependent castes. The term oftentimes goes beyond a metaphor. We invoke it when we speak about the metabolic rate, thermoregulation, nutrient regulation and gas exchange of a social insect colony. Furthermore, we assert that the super-organism has an immune system, and benefits from ``social immunity''. Social immunity was first summoned by evolutionary biologists to resolve the apparent discrepancy between the expected high frequency of disease outbreak amongst numerous, closely related tightly-interacting hosts, living in stable and microbially-rich environments, against the exceptionally scarce epidemic accounts in natural populations. Social immunity comprises a multi-layer assembly of behaviours which have evolved to effectively keep the pathogenic enemies of a colony at bay. The field of social immunity has drawn interest, as it becomes increasingly urgent to stop the collapse of pollinator species and curb the growth of invasive pests. In the past decade, several mechanisms of social immune responses have been dissected, but many more questions remain open. I present my work in two experimental chapters. In the first, I use invasive garden ants (*Lasius neglectus*) to study how pathogen load and its distribution among nestmates affect the grooming response of the group. Any given group of ants will carry out the same total grooming work, but will direct their grooming effort towards individuals carrying a relatively higher spore load. Contrary to expectation, the highest risk of transmission does not stem from grooming highly contaminated ants, but instead, we suggest that the grooming response likely minimizes spore loss to the environment, reducing contamination from inadvertent pickup from the substrate. The second is a comparative developmental approach. I follow black garden ant queens (*Lasius niger*) and their colonies from mating flight, through hibernation for a year. Colonies which grow fast from the start, have a lower chance of survival through hibernation, and those which survive grow at a lower pace later. This is true for colonies of naive and challenged queens. Early pathogen exposure of the queens changes colony dynamics in an unexpected way: colonies from exposed queens are more likely to grow slowly and recover in numbers only after they survive hibernation. In addition to the two experimental chapters, this thesis includes a co-authored published review on organisational immunity, where we enlist the experimental evidence and theoretical framework on which this hypothesis is built, identify the caveats and underline how the field is ripe to overcome them. In a final chapter, I describe my part in two collaborative efforts, one to develop an image-based tracker, and the second to develop a classifier for ant behaviour.}, author = {Casillas Perez, Barbara E}, issn = {2663-337X}, keywords = {Social Immunity, Sanitary care, Social Insects, Organisational Immunity, Colony development, Multi-target tracking}, pages = {183}, publisher = {Institute of Science and Technology Austria}, title = {{Collective defenses of garden ants against a fungal pathogen}}, doi = {10.15479/AT:ISTA:6435}, year = {2019}, } @article{29, abstract = {Social insects have evolved enormous capacities to collectively build nests and defend their colonies against both predators and pathogens. The latter is achieved by a combination of individual immune responses and sophisticated collective behavioral and organizational disease defenses, that is, social immunity. We investigated how the presence or absence of these social defense lines affects individual-level immunity in ant queens after bacterial infection. To this end, we injected queens of the ant Linepithema humile with a mix of gram+ and gram− bacteria or a control solution, reared them either with workers or alone and analyzed their gene expression patterns at 2, 4, 8, and 12 hr post-injection, using RNA-seq. This allowed us to test for the effect of bacterial infection, social context, as well as the interaction between the two over the course of infection and raising of an immune response. We found that social isolation per se affected queen gene expression for metabolism genes, but not for immune genes. When infected, queens reared with and without workers up-regulated similar numbers of innate immune genes revealing activation of Toll and Imd signaling pathways and melanization. Interestingly, however, they mostly regulated different genes along the pathways and showed a different pattern of overall gene up-regulation or down-regulation. Hence, we can conclude that the absence of workers does not compromise the onset of an individual immune response by the queens, but that the social environment impacts the route of the individual innate immune responses.}, author = {Viljakainen, Lumi and Jurvansuu, Jaana and Holmberg, Ida and Pamminger, Tobias and Erler, Silvio and Cremer, Sylvia}, issn = {2045-7758}, journal = {Ecology and Evolution}, number = {22}, pages = {11031--11070}, publisher = {Wiley}, title = {{Social environment affects the transcriptomic response to bacteria in ant queens}}, doi = {10.1002/ece3.4573}, volume = {8}, year = {2018}, }