Structure and function of a compound eye, more than half a billion years old
Brigitte Schoenemann a, b, 1, Helje Pärnaste c, and Euan N. K. Clarkson d
Author Affiliations
aDepartment of Zoology (Neurobiology/Animal Physiology), Biocenter Cologne, D-50647 Cologne, Germany;
bInstitut of Biology Education, D-50931 Cologne, Germany;
cKivion MTÜ, Tallinn 13517, Estonia;
dGrant Institute, School of Geosciences, University of Edinburgh, EH3 9LJW Edinburgh, Scotland
Edited by Dale Purves, Duke University, Durham, NC, and approved November 3, 2017 (received for review September 25, 2017)
Source/Fonte: Schmidtiellus reetae fossil's right eye. Credit: Gen nadi Baranov - PhysOrg
Significance
An exceptionally well-preserved arthropod fossil from near the base of the lower Cambrian shows the internal sensory structures of a compound eye, more than half a billion years old. The trilobite to which it belongs is found in a zone where the first complete organisms appear in the fossil record; thus, it is probably the oldest record of a visual system that ever will be available. This compound eye proved to possess the same kind of structure as the eyes of bees and dragonflies living today, but it lacks the lenses that are typical of modern eyes of this type. There is an elegant physical solution, however, of how to develop a quality image of modern type.
Abstract
Until now, the fossil record has not been capable of revealing any details of the mechanisms of complex vision at the beginning of metazoan evolution. Here, we describe functional units, at a cellular level, of a compound eye from the base of the Cambrian, more than half a billion years old. Remains of early Cambrian arthropods showed the external lattices of enormous compound eyes, but not the internal structures or anything about how those compound eyes may have functioned. In a phosphatized trilobite eye from the lower Cambrian of the Baltic, we found lithified remnants of cellular systems, typical of a modern focal apposition eye, similar to those of a bee or dragonfly. This shows that sophisticated eyes already existed at the beginning of the fossil record of higher organisms, while the differences between the ancient system and the internal structures of a modern apposition compound eye open important insights into the evolution of vision.
compound eye visual system arthropod evolution Cambrian
Footnotes
1To whom correspondence should be addressed. Email: B.Schoenemann@uni-koeln.de.
Author contributions: B.S., H.P., and E.N.K.C. designed research; B.S., H.P., and E.N.K.C. performed research; B.S. analyzed data; and B.S. and E.N.K.C. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
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