Fig. 3

Refraction by the lens of the African cichlid fish, Haplochromis burtoni (upper; supplied by Dr Robert Fernald, Stanford University, Stanford, CA, USA), and of the squid, Sepiotheuthis lessoniana (lower; supplied by Dr. Jacob Sivak, University of Waterloo, Ontario, Canada). The fish lens contains α-, β-, and mostly γ-crystallins, while the squid lens contains almost exclusively S-crystallins, which are homologous to the enzyme glutathione S-transferase although they lack enzyme activity. Note that despite that the fish and squid lens have entirely different crystallins, they both have the ability to focus an image without spherical aberration. From (Piatigorsky 2007)