Ectoparasite Activity During Incubation Increases Microbial Growth on Avian Eggs

Area of Science:

• Ecology
• Parasitology
• Microbiology

Background:

• Direct impacts of parasites are known, but indirect effects are less understood.
• Ectoparasite activity can alter host environments, promoting microbial growth.
• Parasite remains like feces and blood can increase nutrient availability.

Purpose of the Study:

• To investigate the indirect effects of ectoparasites on host offspring.
• To explore how parasitic fly activity influences eggshell microbial communities.
• To determine if these microbial changes impact embryo mortality.

Main Methods:

• Experimental addition of hematophagous flies (Carnus hemapterus) to spotless starling (Sturnus unicolor) nests.
• Quantification of fly feces and blood remains on eggshells.
• Assessment of eggshell bacterial loads and species richness (Operational Taxonomic Units).
• Analysis of the link between bacterial loads and embryo mortality.

Main Results:

• Experimental nests had significantly more fly feces and blood remains.
• Increased abundance and diversity of cultivable bacteria, including potential pathogens, were found on experimental eggshells.
• A correlation was observed between higher eggshell bacterial loads and increased embryo mortality.

Conclusions:

• Ectoparasite activity can indirectly harm host offspring by promoting bacterial growth on eggshells.
• Trans-shell bacterial infection is a potential cause of embryo death.
• This previously overlooked indirect effect of ectoparasitism may have significant ecological and evolutionary implications for host-parasite interactions.