The escape response to avoid the perceived threat is fundamental behavior seen throughout the animal kingdom, and laboratory research has identified the specific neural circuits that control this behavior. Understanding how these neural circuits operate in complex natural settings, however, has become a challenge.
A new study led by researchers at UC Santa Cruz and NOAA Fisheries overcame this challenge using intelligent experimental designs to record and analyze escape responses in reef fish. The result, published November 12 at Proceedings of the National Academy of Sciences, revealing how a defined sequence of decision rules results in circumcision behavior in various species of reef fish.
"We take the approach used in laboratory research into complex and natural environments and find that the same behavioral mechanism seems to apply. A simple set of rules is combined in different ways to produce a rich set of behaviors to achieve this fundamental goal: avoid being killed, "said first author Andrew Hein, research assistant at the UC Santa Cruz Institute of Marine Sciences and research ecologist at NOAA Fisheries Lab in Santa Cruz.
Coral fish in the study ate algae on shallow reef terrain, where they were vulnerable to predators such as moray eels and reef sharks. To simulate threats, researchers use widely used visual stimuli called towering stimuli, black dots that grow in size slowly and then quickly, creating the illusion of rapidly approaching objects. A waterproof tablet computer placed on a coral reef in Moeaea, French Polynesia, plays a towering stimulus, while a video camera records the response of fish swimming to the area in front of the tablet.
The researchers then used computer vision technology to analyze videos. Automatic tracking and a method known as "ray casting," originally developed by video game designers, allowed them to reconstruct what each fish saw when deciding whether or not to escape a threat. They found that fish began escaping maneuvers in response to perceived size and threat stimulus level expansion using rules of decision that matched the dynamics of well-woven-sensitive neural circuits.
"The same behavioral circuits that neurologists identify in laboratory studies seem to operate in more complex natural environments," Hein said. "But we also found something new: sensitivity to a towering stimulus will be set up or down depending on the location of other fish. If someone is the closest to the stimulus, it is far more likely to escape than if there were other fish in between. and threats. "
The third factor in escape response is the location of safe haven, which is offered by coral mounds along the experimental area. The initial response to the stimulus was to quickly turn away from the threat, but soon the fish then began heading to the sanctuary and swam directly at him.
"When you see the path they are taking, it looks like spaghetti – everything is different – but the analysis shows they are all produced by the same set of simple behavior rules," Hein said.
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Material provided by University of California – Santa Cruz. Asli was written by Tim Stephens. Note: Content can be edited for style and length.