A study describes the internal structures of an early trilobite eye. The mechanisms of vision early in animal evolution are poorly understood due to a lack of preserved internal eye structures in the fossil record. Brigitte Schoenemann and colleagues found remnants of internal eye structures in an exceptionally well-preserved fossil of the trilobite Schmidtiellus reetae. The fossil was recovered from a formation in the Baltic that dates to the early Cambrian, more than 500 million years ago. Unlike modern eye lenses, the trilobite lenses were extremely flat and thin with no refracting and focusing convexity. Directly behind the lens was a triangular structure resembling a light-focusing crystalline cone. The structure was followed by a conical tube, consisting of about seven similar elements, likely remnants of receptor cells, grouped around a central structure, possibly a light-guiding rhabdom. The preserved structures resembled the components of an apposition eye, a type of compound eye currently found in bees, dragonflies, and many crustaceans. Based on the dimensions of these structures, the authors estimated the sensitivity, light-gathering capacity, and resolution of the trilobite eyes, which were comparable to the eyes of modern arthropods. According to the authors, the findings suggest that apposition eyes might be as old as the animal fossil record, if not older.
Article #17-16824: "Structure and function of a compound eye, more than half a billion years old," by Brigitte Schoenemann, Helje Pärnaste, and Euan N. K. Clarkson.
MEDIA CONTACT: Brigitte Schoenemann, University of Cologne, GERMANY; tel: +49-221-470-7732, +49-2227-80058; e-mail: <B.Schoenemann@uni-koeln.de>