Abstracts (first author)

Talk 

Do rising temperatures accelerate the evolutionary arms race of hosts and parasites?

Author(s): Scharsack JP, Dittmar J, Schmidt AM, Franke F, Kurtz J

Summary:

Climate change is expected to impact host-parasite coevolution, but information on effects of climate variables on such systems is sparse. Here, three-spined sticklebacks (Gasterosteus aculeatus) infected with the tapeworm Schistocephalus solidus were experimentally exposed to different temperatures. Hosts and parasites were laboratory offspring of populations from Norway, Spain and Germany. Infections were done at 18°C and temperatures were changed to 13°, 24° or kept at 18°C. Whole transcriptome sequencing (RNAseq, Illumina) was performed with liver RNA from a subset (n=96) of control and infected sticklebacks maintained at 13° and 24°C. Temperature alone had significant effects on the gene expression. Exposure to the parasite boosted the temperature effects on genes expression. At 13°C S. solidus grew slower compared to 18° and 24°C, which might partially be explained by lower metabolic rates, but also by the higher activity of the stickleback’s immune system at 13° compared to 18°and 24°C. This was supported by the gene ontology (GO) analysis of the RNAseq data, which revealed that immune genes of infected sticklebacks were more strongly differentially expressed in infected sticklebacks at 13° compared to 24°C. Parasite growth rates did not simply increase with temperature and were lower at 24° compared to 18°C. This suggests that immune activity of sticklebacks is optimal and represses parasite growth around 13°C, while S. solidus grows best at 18°C. Similar observations were made with different origins of sticklebacks and S. solidus, but Norwegian parasites were more virulent and Norwegian sticklebacks were more resistant than the other origins. In ectothermic systems, at first parasites benefit from rising temperatures, but over-exploitation of hosts at very high temperatures might become maladaptive also for the parasites. The present data suggest that rising temperatures indeed have the potential to accelerate the arms race of hosts and parasites.



Abstracts (coauthor)

Summary:

Individual variation in defence can be based on genetic and phenotypic variation in host immune genes. An effective immune response needs to specifically recognise and act against numerous parasites. One way that a host can evolve diversity in immune recognition and effector molecules is through alternative splicing, potentially resulting in variation in gene expression at the individual level. It has been proposed for crustaceans and insects that the alternatively spliced gene Dscam, might be involved in specific immune responses against diverse parasites. Factors in the immune signalling pathways, Imd and Toll, can affect Dscam splice variants, but evidence from the literature appears to be scarce and inconsistent with respect to the effect of parasites on total Dscam mRNA expression. In a first experiment we therefore tested whether Dscam expression is increased after bacterial immune challenge in the red flour beetle, Tribolium castaneum, and the fly, Drosophila melanogaster. In a second experiment we tested whether there is a life-history cost at the individual level of Dscam knock-down in T. castaneum. We predicted that if Dscam is involved in immunity that it would result in reduced survival after a bacterial immune challenge, and given that Dscam has previously been found to be expressed in the gonads and is vital for nervous system development we predicted that there may be a fecundity cost to the knock-down. Our results take a step towards understanding a little more about the role of this intriguing gene in relation to host-pathogen interactions.

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