Mesoscale spatiotemporal variability in a complex host-parasite system influenced by intermediate host body size

Area of Science:

• Ecology
• Parasitology
• Marine Biology

Background:

• Parasites are crucial ecological components, yet factors influencing their distribution in host populations remain unclear.
• Understanding host-parasite dynamics is key to comprehending natural community structures.

Purpose of the Study:

• To investigate the spatiotemporal relationships between parasite exposure, host body size, and parasite burden.
• To determine how host body size influences the effects of parasite exposure on infection prevalence and aggregation.

Main Methods:

• Analyzed parasite prevalence and burden in molecrabs along a 150 km coastline over 22 months.
• Utilized an indirect host-parasite system involving seagulls (definitive hosts) and molecrabs (intermediate hosts) infected by an acanthocephalan worm.
• Employed linear mixed-effects models to assess relationships between seagull density, molecrab size, and parasite load.

Main Results:

• Seagull density positively correlated with molecrab infection prevalence, with a stronger effect on smaller molecrabs.
• Larger molecrabs harbored significantly more parasites than smaller ones, irrespective of seagull density.
• Parasite aggregation showed no clear relationship with seagull density, but unexplained variability was higher in larger molecrabs.

Conclusions:

• Host-parasite interactions are shaped by complex interplay between environmental factors and host traits.
• Size-dependent dynamics in molecrabs are likely driven by parasite accumulation and increased mortality with age in this indirect host-parasite system.