THE CEPHALOPOD EYE
Image 1: Vertebrate and Cephalopod Eye (Image used by permission of Robert Rodieck, from The First Steps in Seeing. Sinauer Associates: Massachusetts. 1998.)
Upon first glance, it is almost impossible to recognize any differences between these two images. The image on the right is that of a cephalopod eye while the image on the left is that of a vertebrate eye. Superficially their eyes are identical to each other and exhibit a single-lens eye structure that possesses a cornea, iris, and lens (Wells 1962). However these two structures are in fact analogous to each other, rather than homologous and only through microscopic examination do any of these differences become readily apparent (Doughty 1995). These similarities were all produced by convergent evolution, a term used to describe the independent development of similar traits between species as a result of their having similar ecological roles and selection pressures (Campbell et al 1999). Specifically, both cephalopods and vertebrates use their eyes extensively for hunting and survival and as a result require highly sophisticated visual systems (Ichikawa et al. 1994, Wells 1978).
Image 2: Cephalopod Eye (Image used by permission of Bert Chauvel; www.visualdiving.com)
The pages found on this web site were created to explain and examine the visual system of higher cephalopods and how it differs and relates to the vertebrate visual system. The information on these pages are meant for general viewing and for the most part can be understood by anyone, regardless of previous experience in the biological sciences.