Parasites and Host Behaviour: Co-evolution from genotype to phenotype (completed)

• Helland-Riise, Siri Helene; Nadler, Lauren Elizabeth; Vindas, Marco; Bengston, Erik; Turner, Andrew & Johansen, Ida Beitnes [Show all 9 contributors for this article] (2020). Regional Distribution of a Brain-Encysting Parasite Provides Insight on Parasite-Induced Host Behavioral Manipulation. Journal of Parasitology. ISSN 0022-3395. 106(1), p. 188–197. doi: 10.1645/19-86. Full text in Research Archive
• Nadler, Lauren Elizabeth; Bengtson, Erik; Eliason, Erika J.; Hassibi, Cameron; Helland-Riise, Siri Helene & Johansen, Ida Beitnes [Show all 12 contributors for this article] (2020). A brain‐infecting parasite impacts host metabolism both during exposure and after infection is established. Functional Ecology. ISSN 0269-8463. doi: 10.1111/1365-2435.13695. Full text in Research Archive
• Midttun, Helene Louise Eghave; Vindas, Marco; Whatmore, Paul J; Øverli, Øyvind & Johansen, Ida Beitnes (2020). Effects of Pseudoloma neurophilia infection on the brain transcriptome in zebrafish (Danio rerio). Journal of Fish Diseases. ISSN 0140-7775. 43(8). doi: 10.1111/jfd.13198. Full text in Research Archive Show summary

  Laboratory zebrafish are commonly infected with the intracellular, brain‐infecting microsporidian parasite Pseudoloma neurophilia . Chronic P. neurophilia infections induce inflammation in meninges, brain and spinal cord, and have been suggested to affect neural functions since parasite clusters reside inside neurons. However, underlying neural and immunological mechanisms associated with infection have not been explored. Utilizing RNA‐sequencing analysis, we found that P. neurophilia infection upregulated 175 and downregulated 45 genes in the zebrafish brain, compared to uninfected controls. Four biological pathways were enriched by the parasite, all of which were associated with immune function. In addition, 14 gene ontology (GO) terms were enriched, eight of which were associated with immune responses and five with circadian rhythm. Surprisingly, no differentially expressed genes or enriched pathways were specific for nervous system function. Upregulated immune‐related genes indicate that the host generally show a pro‐inflammatory immune response to infection. On the other hand, we found a general downregulation of immune response genes associated with anti‐pathogen functions, suggesting an immune evasion strategy by the parasite. The results reported here provide important information on host–parasite interaction and highlight possible pathways for complex effects of parasite infections on zebrafish phenotypes.

• Midttun, Helene Louise Eghave; Vindas, Marco; Nadler, Lauren Elizabeth; Øverli, Øyvind & Johansen, Ida Beitnes (2020). Behavioural effects of the common brain-infecting parasite Pseudoloma neurophilia in laboratory zebrafish (Danio rerio). Scientific Reports. ISSN 2045-2322. 10. doi: 10.1038/s41598-020-64948-8. Full text in Research Archive Show summary

  Research conducted on model organisms may be biased due to undetected pathogen infections. Recently, screening studies discovered high prevalence of the microsporidium Pseudoloma neurophilia in zebrafish (Danio rerio) facilities. This spore-forming unicellular parasite aggregates in brain regions associated with motor function and anxiety, and despite its high occurrence little is known about how sub-clinical infection affects behaviour. Here, we assessed how P. neurophilia infection alters the zebrafish´s response to four commonly used neurobehavioral tests, namely: mirror biting, open field, light/dark preference and social preference, used to quantify aggression, exploration, anxiety, and sociability. Although sociability and aggression remained unaltered, infected hosts exhibited reduced activity, elevated rates of freezing behaviour, and sex-specific effects on exploration. These results indicate that caution is warranted in the interpretation of zebrafish behaviour, particularly since in most cases infection status is unknown. This highlights the importance of comprehensive monitoring procedures to detect sub-clinical infections in laboratory animals.

• Helland-Riise, Siri Helene; Vindas, Marco; Johansen, Ida Beitnes; Nadler, Lauren Elizabeth; Weinersmith, Kelly L. & Hechinger, Ryan F. [Show all 7 contributors for this article] (2020). Brain-encysting trematodes (Euhaplorchis californiensis) decrease raphe serotonergic activity in California killifish (Fundulus parvipinnis). Biology Open. ISSN 2046-6390. doi: 10.1242/bio.049551. Full text in Research Archive Show summary

  Modulation of brain serotonin (5-HT) signalling is associated with parasite-induced changes in host behaviour, potentially increasing parasite transmission to predatory final hosts. Such alterations could have substantial impact on host physiology and behaviour, as 5-HT serves multiple roles in neuroendocrine regulation. These effects, however, remain insufficiently understood, as parasites have been associated with both increased and decreased serotonergic activity. Here, we investigated effects of trematode Euhaplorchis californiensis metacercariae on post-stress serotonergic activity in the intermediate host California killifish (Fundulus parvipinnis). This parasite is associated with conspicuous behaviour and increased predation of killifish by avian end-hosts, as well as inhibition of post-stress raphe 5-HT activity. Until now, laboratory studies have only been able to achieve parasite densities (parasites/unit host body mass) well below those occurring in nature. Using laboratory infections yielding ecologically relevant parasite loads, we show that serotonergic activity indeed decreased with increasing parasite density, an association likely indicating changes in 5-HT neurotransmission while available transmitter stores remain constant. Contrary to most observations in the literature, 5-HT activity increased with body mass in infected fish, indicating that relationships between parasite load and body mass may in many cases be a real underlying factor for physiological correlates of body size. Our results suggest that parasites are capable of influencing brain serotonergic activity, which could have far-reaching effects beyond the neurophysiological parameters investigated here.

• Øverli, Øyvind & Johansen, Ida Beitnes (2019). Kindness to the final host and vice versa: A trend for parasites providing easy prey? Frontiers in Ecology and Evolution. ISSN 2296-701X. 7(50). doi: 10.3389/fevo.2019.00050. Full text in Research Archive
• Johansen, Ida Beitnes; Henriksen, Eirik Haugstvedt; Shaw, Jenny Carolyn; Mayer, Ian; Amundsen, Per-Arne & Øverli, Øyvind (2019). Contrasting associations between breeding coloration and parasitism of male Arctic charr relate to parasite species and life cycle stage. Scientific Reports. ISSN 2045-2322. 9. doi: 10.1038/s41598-019-47083-x. Full text in Research Archive Show summary

  Conspicuous carotenoid ornamentation is considered a signal of individual “quality” and one of the most intensely studied traits found to co-vary with parasitism. Since it has been suggested that only “high quality” individuals have enough resources to express excessive sexual ornaments and resist parasites, current theory struggles to explain cases where the brightest individuals carry the most parasites. Surprisingly little emphasis has been put on the contrasting routes to fitness utilized by different parasite species inhabiting the same host. Using Arctic charr (Salvelinus alpinus) as model species, we hypothesized that skin redness and allocation of carotenoids between skin and muscle (redness ratio) will be positively and negatively associated with parasites using the fish as an intermediate and final host, respectively. Both pigment parameters were indeed positively associated with abundances of parasites awaiting trophic transmission (Diplostomum sp. and Diphyllobothrium spp.) and negatively associated with the abundance of adult Eubothrium salvelini tapeworms. These empirical data demonstrate that contrasting associations between carotenoid coloration and parasite intensities relates to the specific premises of different parasite species and life cycle stages.

View all works in Cristin