Losing focus: the decline in T. Marmoratus larvae’s hunting success correlates with visual system degradation prior to pupation.
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1
University of Cincinnati, Department of Biological Sciences, United States
The larvae of the Sunburst Diving Beetle Thermonectus marmoratus are primarily visually guided hunters with two principal camera-type eyes one either side of the head that are used for prey capture. The visual systems of these eyes are complex, with large bifocal lenses and two dominant retinas (distal and proximal). These larval stemmata are replaced by compound eyes during holometabolous metamorphosis. In the last days of their third, and final, instar these eyes retain their overall shape but shrink significantly in length. Here we examine when and how pre-metamorphic degradation influences the ability of late third instars to focus images within their eyes, and to capture prey. A frame-by frame video analysis of hunting behavior was used to assess hunting behavior. Specifically, we scored capture success and failure rates, the distance from the prey at each strike, the larvae’s body posture preceding a strike, and for failed attempts the distance by which larvae missed their targets. After behavioral trials, larvae were sacrificed, and one half of the head was used to measure the lens’ optics, while the other was used for histological measurements. For each eye, anatomical measurements were made from the back of the lens to the surface of the proximal and distal retinas as well as to the back of the eye. Optical data from the principal lenses was analyzed for the position of focal planes, as well as for the relative quality of the image. We found that within the approximately seven days of their life as third instar, larvae’s ability to hunt is optimal between days two and five, after which it declines sharply. This decline in hunting success is accompanied by a reduction in eye length and a decline in image quality, to the point that the two distinct focal planes become undistinguishable. At the same time, based on the larvae’s body pasture, attacks appear to become more vigorous. Based on our optical findings we conclude that the larvae’s reduced success in prey capture correlates with a decline in vision. However, the shrinkage of the eye tubes may result in slightly improved vision in air, possibly helping them during their transition to land.
Acknowledgements
This work was supported by NSF IOS0545978 and IOS1050754
Keywords:
hunting behavior,
optics,
prey capture,
Vision
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for student poster award)
Topic:
Sensory: Vision
Citation:
Werner
S and
Buschbeck
EK
(2012). Losing focus: the decline in T. Marmoratus larvae’s hunting success correlates with visual system degradation prior to pupation..
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00304
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Received:
30 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Ms. Shannon Werner, University of Cincinnati, Department of Biological Sciences, Cincinnati, OH, 45221, United States, wernersl@mail.uc.edu