Host behaviour alteration by its parasite: from brain gene expression to functional test

Area of Science:

• Parasitology
• Neurobiology
• Behavioral Ecology

Background:

• Complex life cycle parasites often manipulate intermediate host behavior to enhance transmission.
• The threespine stickleback (Gasterosteus aculeatus) is an intermediate host for the cestode Schistocephalus solidus, exhibiting increased risky behaviors when infected.

Purpose of the Study:

• To investigate the proximate molecular mechanisms underlying behavioral alterations in sticklebacks infected with S. solidus.
• To identify specific host genes and pathways targeted by the parasite.

Main Methods:

• Comparative transcriptomics of infected and uninfected stickleback brains.
• Functional testing of the inositol pathway using lithium chloride exposure.
• Analysis of gene expression in fish exposed to the parasite but not successfully infected.
• Comparison of gene expression profiles with selective serotonin reuptake inhibitor (SSRI) treated fish.

Main Results:

• Infected sticklebacks exhibit altered gene expression in the inositol pathway.
• Lithium treatment rescued normal behaviors in infected fish, implicating the inositol pathway.
• Fish exposed to the parasite but uninfected showed a distinct gene expression profile, separating exposure effects from infection consequences.
• Serotonin pathway gene expression in infected fish did not mirror that of SSRI-treated fish, despite similar behavioral changes.

Conclusions:

• The inositol pathway is a likely target for S. solidus-mediated manipulation of stickleback behavior.
• This research provides a molecular basis for understanding host-parasite interactions and behavioral manipulation.
• The findings differentiate between general parasite exposure effects and specific infection-driven alterations.