Evolutionary links between apposition and superposition optics in crustacean eyes

• DOI: 10.1038/302818a0
• Publication Date: 2004-11-17T22:54:45Z
• Authors: D.-E. Nilsson
• Keywords: 0301 basic medicine; 0303 health sciences; 03 medical and health sciences

The two fundamental principles of image formation in compound eyes, apposition and superposition, have long been known to exist in both insects and crustaceans1. The scattered distribution of the two optical mechanisms2–4 indicates that one type can evolve into the other, but as they are so fundamentally different, it has been an enigma how such evolution could occur. In crustaceans, superposition eyes are present among the orders Mysidacea, Euphausiacea and Decapoda5. I now report that the planktonic larvae of most euphausiids and decapods possess a transparent type of apposition eye, designed for planktonic life, that is pre-adapted for superposition optics. This discovery suggests that the evolution of superposition eyes in crustaceans has its origin in the special apposition optics found in the larval eyes, thus providing the first evidence of an evolutionary link between apposition and superposition optics.