A Novel Interception Strategy in a Miniature Robber Fly with Extreme Visual Acuity

Curr Biol. 2017 Mar 20;27(6):854-859. doi: 10.1016/j.cub.2017.01.050. Epub 2017 Mar 9.

Abstract

Our visual system allows us to rapidly identify and intercept a moving object. When this object is far away, we base the trajectory on the target's location relative to an external frame of reference [1]. This process forms the basis for the constant bearing angle (CBA) model, a reactive strategy that ensures interception since the bearing angle, formed between the line joining pursuer and target (called the range vector) and an external reference line, is held constant [2-4]. The CBA model may be a fundamental and widespread strategy, as it is also known to explain the interception trajectories of bats and fish [5, 6]. Here, we show that the aerial attack of the tiny robber fly Holcocephala fusca is consistent with the CBA model. In addition, Holcocephala fusca displays a novel proactive strategy, termed "lock-on" phase, embedded with the later part of the flight. We found the object detection threshold for this species to be 0.13°, enabled by an extremely specialized, forward pointing fovea (∼5 ommatidia wide, interommatidial angle Δφ = 0.28°, photoreceptor acceptance angle Δρ = 0.27°). This study furthers our understanding of the accurate performance that a miniature brain can achieve in highly demanding sensorimotor tasks and suggests the presence of equivalent mechanisms for target interception across a wide range of taxa. VIDEO ABSTRACT.

Keywords: flight; interception strategy; invertebrate; moving target; predation; retina; spatial resolution; tracking; vision.

MeSH terms

  • Animals
  • Diptera / physiology*
  • Motion Perception*
  • Psychomotor Performance
  • Visual Acuity*