How cunning is the puppet-master? Cestode-infected fish appear generally fearless

Area of Science:

• Ecology
• Parasitology
• Animal Behavior

Background:

• Trophically transmitted parasites rely on predator-prey interactions for transmission.
• Parasite manipulation of host behavior can enhance transmission but carries risks if imprecise.
• The cestode Schistocephalus solidus infects three-spined sticklebacks, altering their antipredator behaviors.

Purpose of the Study:

• To investigate whether Schistocephalus solidus precisely manipulates three-spined stickleback antipredator behaviors.
• To determine if reduced antipredator behavior is a specific adaptation or a general side effect of infection.
• To test alternative explanations for altered behavior, such as disease symptoms or increased hunger.

Main Methods:

• Experimental comparison of antipredator responses in infected and uninfected three-spined sticklebacks.
• Exposure to simulated predatory attacks and olfactory cues from predators.
• Assessment of fish vigor and hunger levels.

Main Results:

• Infected sticklebacks exhibited reduced responses to simulated predatory attacks.
• This fearlessness was general, extending to non-host predators and non-visual threats.
• No evidence supported reduced vigor or increased hunger as causes for altered behavior.

Conclusions:

• Schistocephalus solidus induces a general fearlessness in sticklebacks, not a precise manipulation targeting specific predators.
• Imprecise behavioral manipulation may still benefit parasites by increasing host exposure to correct predators.
• Altered host behavior, even if general, can have adaptive value for parasite transmission.