42 VISION 



Soluble protein— Methodology in the following studies is aimed 

 mainly at separating and classifying structural (nonenzymatic) proteins of 

 the lens. This requires one or a combination of techniques for arriving at 

 molecular weight, charge, or antigenic specificity of the protein in question. 

 However, many techniques with varying relationship to one another are avail- 

 able. For example, there are no less than six independent immunoassays. 

 Thus, part of the conflicting results reported here may be due to varying 

 methodology rather than to species differences. Unfortunately, extraction 

 and preparation of lens protein has not yet been standardized. In addition, it 

 is frequently difficult to determine the age of a fish, an important consid- 

 eration since, as just mentioned, protein composition changes in ontogeny. 

 Thus, further disparities of results from different research groups can be 

 expected (Clayton 1974). 



Bon and his coworkers (Bon 1958, Bon et al. 1964, 1966, 1968) have 

 analyzed soluble proteins of the ocular lens by a variety of techniques. Using 

 agar electrophoresis, Bon (1958) found a remarkable similarity between a 

 and j3 crystallin of the adult shark (Scyliorhinus) and the newborn calf. He 

 reported that a crystallin of Scyliorhinus changes little during ontogeny, 

 while /3 crystallin continuously increases throughout early life. This is similar 

 to the pattern in higher vertebrates. Bon further speculated on genetic 

 mechanisms of crystallin formation. 



Bon et al. (1964) characterized the soluble lens proteins of five elasmo- 

 branch species, all adults. Pronounced a and j3 groups were noted, as well as 

 a series of low electrophoretic peaks representing y and 3 proteins. This was 

 apparently the first observation of 3 crystallin in the fish lens. It is not clear, 

 however, if Bon's 9 crystallin corresponds to Rabaey's (1962) so-called first 

 important soluble component (FISC) of the bird, which was later called 3 

 crystallin. Indeed, Bon felt that Rabaey's 3 crystallin was identical to verte- 

 brate crystallin. 



Bon correctly noted the phylogenetic disparity between the sharks he 

 investigated, pointing out that spiny dogfish and blue shark represent separate 

 ordinal levels. Yet the lens proteins of these two sharks were structurally 

 more closely related than the proteins of Scyliorhinus (taxonomically close 

 to the blue shark) or Raja (relatively close to the spiny dogfish). The authors 

 thus suggested an environmental effect on protein elaboration since Scylio- 

 rhinus and Raja are benthic while Squalus and Prionace are pelagic. 



Bon et al. (1968) further characterized 3 crystallin in adults of four elas- 

 mobranch species. Basically different gel filtration and sedimentation pat- 

 terns between teleosts and elasmobranchs, especially Squaliformes and Raja- 

 formes, were found. Surprisingly, the elasmobranch pattern more closely 

 resembled that of mammals than that of teleosts. However, Rabaey (1965a) 

 disagreed, finding little difference between the protein patterns of sharks and 

 bony fish. 



Cobb et al. (1968) criticized the usual methods of identifying lens crystal- 

 lins, claiming that the best methods rely on the specification of charge, 

 electrophoretic mobility, size, shape, and distribution of charge, combined 

 with free electrophoresis, zone electrophoresis, and sedimentation analyses. 



