Stonefly nymphs use hydrodynamic cues to discriminate between prey

Area of Science:

• Ecology
• Aquatic Ecology
• Predator-Prey Dynamics

Background:

• Stream-dwelling predatory stoneflies (Kogotus modestus) exhibit selective predation on certain mayfly species.
• Understanding the sensory mechanisms underlying prey discrimination is vital for aquatic ecosystem research.

Purpose of the Study:

• To determine if predatory stonefly nymphs use hydrodynamic cues to differentiate between prey and non-prey mayfly species.
• To investigate the role of swimming patterns in prey selection by Kogotus modestus.

Main Methods:

• Playback experiments were conducted in a Rocky Mountain stream using recorded pressure wave patterns of mayfly swimming behavior.
• Predatory stoneflies were video recorded responding to playbacks of favored prey (Baetis bicaudatus) and non-prey (Ephemerella infrequens) mayflies using live and model stimuli.
• Experimental conditions included starved and recently fed stoneflies, and different playback presentation orders.

Main Results:

• Kogotus modestus showed a higher probability of attack per encounter with Baetis bicaudatus playbacks, indicating prey discrimination.
• Discrimination between prey and non-prey swimming patterns occurred, but was dependent on the playback method (model vs. live mayfly).
• Successful prey capture prior to playback heightened attack probability and prey discrimination, mimicking responses to live prey.

Conclusions:

• This study provides the first evidence of stream-dwelling predators using hydrodynamic cues for prey-nonprey discrimination.
• Hydrodynamic cues from mayfly swimming patterns are a key mechanism explaining selective predation by stoneflies in natural environments.
• Kogotus modestus can discriminate prey based on distinct swimming-induced hydrodynamic signatures.