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First published online February 29, 2008
Journal of Experimental Biology 211, 844-851 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.012179
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Visual sensitivity in the crepuscular owl butterfly Caligo memnon and the diurnal blue morpho Morpho peleides: a clue to explain the evolution of nocturnal apposition eyes?

Rikard Frederiksen* and Eric J. Warrant

Lund University, Department of Cell and Organism Biology, Helgonavägen 3, S-22362 Lund, Sweden


Figure 1
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  		Fig. 1. Maps of the frontal visual fields of the left eyes of male Caligo memnon (A,B) and male Morpho peleides (C,D) with isolines representing facet diameter D, in µm (A,C), and interommatidial angle {Delta}{phi}, in degrees (B,D). The globes represent the three-dimensional space around the butterfly (with lines of latitude and longitudes in 10° steps), with the eye located at the globe's centre. The arrows indicate the orientation of the butterfly: A, anterior; D, dorsal; V, ventral; L, lateral. The boundary of the eye's receptive field is also indicated by the dorso-ventrally oriented contour in each panel.

 

Figure 2
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  		Fig. 2. Scanning electron micrographs of the eyes of a male Caligo memnon (A) and a male Morpho peleides (B). The local eye radius of C. memnon is almost twice as large as that of M. peleides. Scale bar for A and B, 1 mm.

 

Figure 3
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  		Fig. 3. Transmission electron micrographs showing distal transverse sections through the rhabdoms of male Caligo memnon (A) and male Morpho peleides (B). Scale bar for A and B, 2 µm.

 

Figure 4
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  		Fig. 4. Typical angular sensitivity functions recorded from single cells in a male Caligo memnon (blue) and male Morpho peleides (red) in (A) light-adapted (LA) and (B) dark-adapted (DA) conditions. The acceptance angles of the angular sensitivity functions for these cells are slightly larger in C. memnon ({Delta}{rho}LA=1.4°, {Delta}{rho}DA=2.1°) than in M. peleides ({Delta}{rho}LA=0.9°, {Delta}{rho}DA=1.7°).

 

Figure 5
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  		Fig. 5. Typical impulse responses (A,B) with corresponding calculated power spectra (C,D) recorded from single cells in a male Caligo memnon (blue) and a male Morpho peleides (red) in (A,C) light-adapted (LA) and (B,D) dark-adapted (DA) conditions. The integration time and time-to-peak of these recordings are: C. memnon {Delta}tLA=9 ms, {Delta}tDA=18 ms, {tau}p,LA=17 ms, {tau}p,DA=31 ms, and M. peleides {Delta}tLA=8 ms, {Delta}tDA=15 ms, {tau}p,LA=16 ms, {tau}p,DA=26 ms. The corresponding corner frequencies are: C. memnon fc,LA=33 Hz, fc,DA=16 Hz and M. peleides fc,LA=42 Hz, fc,DA=23 Hz.

 




© The Company of Biologists Ltd 2008