Cercarial Behavior Determines Risk of Predation

Area of Science:

• Ecology
• Parasitology
• Biodiversity

Background:

• Local biodiversity can influence parasite transmission, particularly for trematodes, where non-host organisms dilute infective stages (cercariae).
• Previous research focused on single trematode species' transmission stages and predator effects, lacking comparative analysis across species with different behaviors.

Purpose of the Study:

• To investigate how varying host-searching movement patterns of trematode cercariae affect their susceptibility to predation by non-host species with different feeding habits.
• To understand the role of species-specific interactions between parasite dispersal and predator feeding modes in trematode transmission dynamics.

Main Methods:

• Conducted predation experiments using six trematode cercariae species exhibiting free-swimming or bottom-dwelling behaviors.
• Utilized two predator species with distinct feeding modes: a filter feeder (Sphaerium sp.) and a grazer (Physa acuta).
• Assessed cercarial survival rates under different predator-grazer interactions.

Main Results:

• Cercarial susceptibility to predation was strongly dependent on the interaction between cercarial dispersal behavior and predator feeding strategy.
• Filter feeders preyed on free-swimming cercariae but not bottom-dwelling ones.
• Grazers did not affect free-swimming cercariae but reduced bottom-dwelling cercariae in one species.

Conclusions:

• Trematode transmission dynamics are shaped by specific interactions between parasite life stages and free-living organisms, not just overall biodiversity.
• These findings have significant implications for understanding disease ecology, parasite infection success, and ecosystem energetics, as cercariae are a food source.