A hypothesis for robust polarization vision: an example from the Australian imperial blue butterfly,Jalmenus evagoras
Abstract
The Australian lycaenid butterfly Jalmenus evagoras has iridescent wings that are sexually dimorphic, spectrally and in their degree of polarization, suggesting that these properties are likely to be important in mate recognition. We first describe the results of a field experiment showing that free-flying individuals of J. evagoras discriminate between visual stimuli that vary in polarization content in blue wavelengths but not in others. We then present detailed reflectance spectrophotometry measurements of the polarization content of male and female wings, showing that female wings exhibit blue-shifted reflectance, with a lower degree of polarization relative to male wings. Finally, we describe a novel method for measuring alignment of ommatidial arrays: by measuring variation of depolarized eyeshine intensity from patches of ommatidia as a function of eye rotation, we show that (a) individual rhabdoms contain mutually perpendicular microvilli; (b) many rhabdoms in the array have their microvilli misaligned with respect to neighboring rhabdoms by as much as 45 deg; and (c) the misaligned ommatidia are useful for robust polarization detection. By mapping the distribution of the ommatidial misalignments in eye patches of J. evagoras, we show that males and females exhibit differences in the extent to which ommatidia are aligned. Both the number of misaligned ommatidia suitable for robust polarization detection and the number of aligned ommatidia suitable for edge detection vary with respect to both sex and eye patch elevation. Thus, J. evagoras exhibits finely tuned ommatidial arrays suitable for perception of polarized signals, likely to match sex-specific life history differences in the utility of polarized signals.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2023
- Source ID
- 10.1242/jeb.244515
Entities
People
- Benedict G Hogan
- Cheng‐Chia Tsai
- Edward Soucy
- Gary D Bernard
- Heqing Huang
- Joel Greenwood
- Marjorie A. Liénard
- Mark Cornwall
- Mary Caswell Stoddard
- Matthew L M Lim
- Nanfang Yu
- Naomi Pierce
- Richard Childers
Organizations
- Air Force Office of Scientific Research
- Columbia University
- Harvard University
- Lund University
- National Science Foundation
- National University of Singapore
- Princeton University
- Swedish Research Council
- University of Washington
- Yale University