Researchers used motion-capture techniques to watch dragonflies catch their prey and found their movement is guided by internal models of its own body and the anticipated motions of its target.
The findings are significant because these internal models are also known to be used by humans, the Howard Hughes Medical Institute reported.
"This highlights the role that internal models play in letting these creatures construct such a complex behavior," said Janelia group leader Anthony Leonardo, who led the study. "It starts to reshape our view of the neural underpinnings of this behavior."
This type of behavior has only been seen before in vertebrates, but these new findings suggest dragonflies perform internal calculations as complex as a ballet dancer's. Humans perform complex inner calculations that are required to even perform simple tasks such as reaching for a cup of coffee.
"You have an internal model of how your arm works, how the joints are articulated, of the cup and its mass. If the cup is filled with coffee, you incorporate that," Leonardo said. "Articulating a body and moving it through space is a very complicated problem."
In the past, researchers thought insects captured prey through a simpler system in which movement is guided solely by the target's position; these new findings suggest otherwise.
To make their findings, researchers spent several years creating a system that allowed them to track a dragonfly's movement as it went in for a kill. The system is based on the same motion-capture techniques that allow actors' motions to be translated into movement. Reflective markers are placed on different parts of the body and a high-speed video camera captures the flashes of light that occurs when the subject moves. This allowed the researchers to reconstruct the dragonfly's exact movements as it chased either a fruit fly or maneuverable false prey.
The team found the dragonfly was not simply responding to the movements of the prey but instead were making structured turns that adjusted their body orientations, even when the prey itself did not change angles.
"Those turns were driven by the dragonfly's internal representation of its body and the knowledge that it has to rotate its body and line it up to the prey's flight path in a particular way," Leonardo said.
The dragonflies oriented themselves so as to hit their prey from below, reducing the risk of detection. The insects also move their head to keep the center of their prey lined up with their eye, despite their own body's movement. This allows the dragonfly to receive two channels of information from its prey.
"It gives the dragonfly a very elegant combination of predicted model-driven control and the original reactive control," Leonardo concluded.
The findings were published Dec. 11 in the journal Nature.
