Evolutionary significance of photoreceptors: In retrospect

Abstract

This essay presents an updating of the author's theory that there are two major lines in the evolution of photoreceptors, one ciliary and the other rhabdomeric (microvillar). Arguments are presented for rejecting a new and alternative theory of Salvini-Plawen and Mayr (1977) that photoreceptors have arisen many times, independently of one another, and that there are no major lines in the evolution of light-sensitive organelles. Arguments are also advanced against the theory of Vanfleteren and Coomans (1976) and others that microvillar photoreceptors are induced by ciliary structures. © 1979 by the American Society of Zoologists.