RNA allows identifying the consumption of carrion prey

Area of Science:

• Ecology
• Molecular Biology
• Zoology

Background:

• Facultative scavenging is a common feeding strategy in predatory carnivores, yet its ecological significance is poorly understood.
• Current DNA-based diet analysis methods cannot differentiate between predation and scavenging.
• This limitation hinders the assessment of scavenging's impact on population dynamics and resource partitioning.

Purpose of the Study:

• To develop a novel molecular method to distinguish between fresh prey consumption and scavenging.
• To utilize prey RNA as a target molecule, hypothesizing its rapid post-mortem degradation differentiates consumption types.
• To overcome a key limitation in molecular diet analysis for ecological studies.

Main Methods:

• Ground beetles (Pseudoophonus rufipes) were fed either fresh or 1-day-old (carrion) Drosophila melanogaster fruit flies.
• Prey RNA and DNA detectability in beetle regurgitates were assessed using RT-PCR and PCR assays.
• Samples were analyzed at multiple time points (0, 6, 12, 24, 48 hours) post-feeding.

Main Results:

• Both prey RNA and DNA were equally detectable after consumption of fresh prey across all time points.
• When carrion was consumed, prey RNA detection was significantly lower than DNA detection immediately after feeding.
• Prey RNA detection in carrion-fed beetles dropped to zero within 6 hours of digestion.

Conclusions:

• Prey RNA detection is a reliable indicator to differentiate between the consumption of fresh prey and scavenged food.
• This methodological innovation provides a generally applicable approach to study scavenging in food webs.
• Understanding scavenging's role can reveal its functional consequences for populations, communities, and ecosystems.