University Scientists Quantify the Zebrafish's Use of a 'Stealth Zone' to Capture Prey
A team from the University of Minnesota provides new insights on the ability of zebrafish to alter aspects of fluid motion around their bodies to overcome escape responses and increase capture of prey.
Zebrafish prey on tiny crustaceans called copepods, which exhibit some of the shortest response times and fastest swimming speeds, relative to body size, in the animal kingdom. These tiny creatures have developed an incredible sensitivity to disruptions in water, enabling them to sense approaching predators and quickly evade attacks. Yet despite increased sensitivity and lightning-fast reactions, copepods still have problems evading zebrafish, who are frequently successful at catching their prey.
"We believe this high success rate can be attributed to a 'stealth zone,' created when an approaching zebrafish generates suction within its mouth," explains Deepak Adhikari, doctoral candidate in the Department of Aerospace Engineering and Mechanics. "The zebrafish employ suction ahead of a strike to minimize the flow disturbance generated by their forward swimming. Thus, the copepods are unaware of the approaching threat until the zebrafish is close enough to strike."
While previous studies have focused on what occurs during the actual strike, the UMN team used high-speed, infrared tomographic particle image velocimetry (PIV) to study the flow field around the zebrafish during its approach. The team's insights suggest that to create this 'stealth zone', the suction velocities at the opening of the fish's mouth must approximately match the forward swimming velocity of the zebrafish.
"This study provides insight into a critical trophic interaction in aquatic food webs," explains Ellen K. Longmire, Professor in the Department of Aerospace Engineering and Mechanics. "The detection and quantification of a mechanism that aids in the capture of evasive prey helps explain how a common, but short range, feeding mechanism can be deployed successfully on highly sensitive, evasive prey."
Danio rerio also known as the zebrafish. Credit: Bob Jenkins