Abstracts (first author)

Poster 

Inbreeding dependent trade-offs in the ant Formica exsecta

Author(s): Freitak D, Bos N, Stucki D, Sundström L

Summary:

Trade-offs between different defence mechanisms and life-history traits are known to exist. Especially interesting are the ones involving immune defences, as surviving infections is paramount for any organism. The capability to respond to stressors depends on the phenotypic plasticity of an organism. It is assumed that inbreeding decreases the adaptability of organisms to environmental stresses (e.g. dealing with pathogens, oxidative stress). Recent evidence from many insects highlights the importance of Reactive Oxygen Species (ROS) in insect immunity by regulating potential pathogens and keeping commensal gut flora under control. Although the release of these free radicals is an extremely effective defence against intruders, it is also harmful to the organism itself, as it causes oxidative stress. This is a situation where cellular production of ROS overwhelms its antioxidant capacity, leading to damage of various macromolecules (e.g. lipids, proteins, DNA). Dealing with this self-inflicted injury is essential, but requires extra resources for anti-oxidant production. In a multi-infection scenario, the capability of an organism to deal with multiple stressors may give a crucial advantage in comparison to less adaptive phenotypes. Here, we study how ants with different inbreeding levels cope with bacterial and fungal parasites, being previously exposed to oxidative stress via feeding with ROS. Dietary intake of extra ROS may lead to better survival against gut penetrating entomopathogenic bacteria, but may at the same time leave fewer resources to fight against fungal pathogens. We use oral infection with the pathogenic bacterium Serratia marcescens, and the exposure to the generalist fungal pathogen Metarhizium brunneum to study the trade-offs between ROS responses and the immune response in workers of F. exsecta. Comparing inbred colonies and outbred colonies reveals differences in the expression of various antioxidant and immunity related responses.



Abstracts (coauthor)

Why do inbred ants live longer?

Author(s): Bos, N, Freitak D, Pulliainen U, Sundström L

Summary:

Inbreeding has profound consequences on a genomic, individual, population and even species level. However, the effects of inbreeding on natural populations, especially in insects, remain largely unstudied. Ants are an ideal model system to study the consequences of inbreeding, as they are ecologically important and form socially complex groups. Social groups provide another level possibly affected by inbreeding, as the large amount of interactions between numerous individuals could give rise to socially mediated inbreeding depression. Inbreeding has been shown to have negative consequences both at the individual and colony level in a natural population of the narrow-headed ant (Formica exsecta). Here, we compare the resistance of inbred and outbred worker ants against starvation. Our results indicate that inbreeding has no effect on longevity under starvation, however, naïve (fed) inbred ants outlive the outbred ones. What makes inbred ants live longer? We investigated these questions using both behavioural assays and gene expression studies.

Transgenerational immune priming in Lepidoptera

Author(s): Vilcinskas, A, Freitak D, Schmidtberg H, Vogel H

Summary:

Parental investment in offspring encompasses its preparation to defend themselves against pathogens or parasites initially encountered by the adults. In order to explore the mechanisms mediating trans-generational immune priming in insects we used the established lepidopteran model host Galleria mellonella. Here we show that feeding of G. mellonella larvae with either non-pathogenic bacteria or with bacterial pathogens such as Pseudomonas entomophila and Serratia entomophila is sufficient to increase expression of immunity-related genes such as the antibacterial protein gloverin. Dietary uptake of bacteria by the larvae resulted also in differential expression of immunity-related genes in the eggs laid by the corresponding female adults, providing evidence for trans-generational immune priming of the offspring. In subsequent studies we explored the mechanism mediating transgenerational immune priming in Lepidoptera.

Summary:

Recent studies on invertebrate immunity show that insects possess mechanisms to protect themselves from a secondary infection of a pathogen they have previously encountered. This suggests that invertebrates are able to differentiate between pathogens and mount more specific defence responses than previously thought. However, mechanisms for this specificity remain largely unknown. Here, we report a strain-specific immune priming response in the lepidopteran Parasemia plantaginis with enthomopathogenic Serratia marcescens bacteria. A major proportion of the moth larvae survived a septic injury with S. marcescens strain to which they had been previously orally exposed. Priming with another strain of S. marcescens and a similarly gram-negative, but harmless, Escherichia coli both failed to provide the protection later in life. We also show that production of caseinolytic proteases is likely a very important virulence factor in orally induced infection in this system. The findings have implications on the evolution of immune system in relatively short-lived insects, as well as on the selective processes entomopathogens may encounter in the arms race with their hosts.

Summary:

Eusocial insects are favorable targets for parasites due to high relatedness within a colony and a large amount of interacting individuals. Consequently, eusocial insects evolved a strong defense against parasites on an individual, as well as a social level. When resources are scarce, individuals and colonies are weakened and opportunistic pathogens might be able to infect the hosts, which face a trade-off between energy saving and immune defense. Different demands for energy use during the active season and hibernation are likely to influence this trade-off. This possible trade-off might even be stronger when resource availability is low and starvation imposes additional stress on the individual. Here we investigate seasonal differences in regulation of immune defenses under starvation in the ant Formica exsecta. We used bioassays coupled with gene expression analysis of immune, stress and storage protein. In order to estimate the organism’s capability to fight off infections, depending on seasonal and nutritional status, entomopathogenic bacteria Serratia marcescens and Pseudomonas entomophila were used.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
Close