The eye of a “living fossil” butterfly, Parnassius glacialis (Papilionidae): a view into the evolution of rhabdom in insects
-
1
Sokendai-Hayama (The Graduate University for Advanced Studies), Department of Evolutionary Studies of Biosystems, Japan
-
2
Howard Hughes Medical Institute, Janelia Farm Research Campus, United States
The Glacial Apollo, Parnassius glacialis, a living fossil species, appear abundantly in the spring in Japan. The genus Parnassius belongs to the Parnassini, the oldest tribe in the subfamily Parnassiinae, which diverged from the other papilionid subfamilies in the Cretaceous period and rapidly radiated in the late tertiary period. They fly slowly as if they are floating in the air and feed on nectar of various flowers. Recent studies on butterfly color vision have revealed that the organization of their eyes is quite diverse among species. The diversity includes the number of opsin genes, their expression pattern, the eye pigmentation, and spectral sensitivities of photoreceptors. In order to elucidate the origin of the various butterfly eye designs, we have initiated a detailed analysis of the eyes of Parnassius.
The Parnassius eyes consist of about 5000 ommatidia, each containing nine photoreceptors R1-R9. The ommatidia can be divided into three spectrally-heterogenous types. Electron microscopy revealed that the Parnassius rhabdom is tiered: the distal tier is exclusively composed of photoreceptors expressing opsins of UV or blue-absorbing visual pigments, whereas the proximal tier consists of photoreceptors expressing opsins of green or red-absorbing visual pigments. This organization is unique because the distal tier of other known butterflies contains two green-sensitive photoreceptors in all ommatidia completely filling the hexagonal lattice, which probably function in improving spatial and/or motion vision.
Interspecific comparison of the rhabdom structure among insects suggests that the ancestral rhabdom was non-tiered, which first became tiered with two short wavelength receptors in the distal tier and several green receptors in the proximal tier. The set of long wavelength receptors in the proximal tier then became spectrally rich due to opsin duplication and/or the implementation of perirhabdomal pigments. Two of the long wavelength receptors in each ommatidium eventually became distal photoreceptors that are presently green sensitive in all ommatidia, which appear to be most suitable to improve spatial and motion vision. Taken together, the Parnassius eye is apparently unique, because it lacks the monochromatic R3/R4 system in the distal tier. Instead, the receptors in a subset of ommatidia become red sensitive, probably enhancing the color discrimination ability towards the long wavelength region of the spectrum. Presumably for the slow-flying, ancestral group of butterflies acute spatial and motion vision had a lower priority than extreme colour discrimination.
Keywords:
Color Vision,
Compound eye,
insect,
Ommatidia,
photoreceptor,
Rhabdom,
Spectral sensitivity,
Visual pigment opsin
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster (but consider for Participant Symposium)
Topic:
Sensory: Vision
Citation:
Arikawa
K,
Matsushita
A,
Awata
H,
Wakakuwa
M and
Takemura
S
(2012). The eye of a “living fossil” butterfly, Parnassius glacialis (Papilionidae): a view into the evolution of rhabdom in insects.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00175
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
28 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Prof. Kentaro Arikawa, Sokendai-Hayama (The Graduate University for Advanced Studies), Department of Evolutionary Studies of Biosystems, Shonan Village, Hayama, 240-0193, Japan, arikawa@soken.ac.jp