Meeting Abstract

48.2  Monday, Jan. 5  Patterns of S-crystallin evolution are correlated with optical acuity in cephalopods SWEENEY, AM*; MATZ, MV; MORSE, DE; JOHNSEN, S; University of California, Santa Barbara; University of Texas, Austin; University of California, Santa Barbara; Duke University sweeney@lifesci.ucsb.edu

Positive selection on surface charge and thermodynamic stability in Loligo opalescens lens S-crystallin proteins contributed to the evolution of low refractive index regions in the exterior of the lens. This evolutionary development allowed squid to develop highly acute and sophisticated graded refractive index lenses necessary for good vision underwater. In this study, we simultaneously explored visual acuity and patterns of S-crystallin evolution across cephalopods. We found that an organisms overall optical acuity is reflected in the physical characteristics of S-crystallins expressed in the lens and their patterns of evolution. Octopuses have a small suite of highly similar crystallins, and accordingly, their visual acuity is relatively low. All studied families of decapod squid exhibit the same large suite of S-crystallins and the same pattern of charge evolution previously described in Loligo. Accordingly, the decapod squids’ optical capabilities are quite similar to each other, and are more acute than those of octopuses. In addition, each squid family’s S-crystallin suite appears to be more closely related to itself than to the other squid families’ S-crystallins. As a result, we predict that squid S-crystallins have had a history of concerted evolution. We discuss the possibility that concerted evolution may be a mechanism for maintaining S-crystallin monodispersity in the lens, which is necessary for optical function and cataract prevention.