Although data herein presented are expressions of — was precipitated by the anti-B serum but not the anti-A 
only one character (the LDH isozyme pattern), they are serum (Fig. 3) indicating that it contained only B sub- 
especially significant at the generic level. The LDH B, units and was the B, homopolymer. 
isozyme of 19 species of Percina possessed an identical Electrophoresis of EDEH isozymes in EBT buffer (Fig. 
electrophoretic mobility; that mobility was absent in 45 4) showed more clearly the unique mobilities of LDH 
of 46 species of Etheostoma and in the 2 species of Am- isozymes of certain species of Etheostoma (Es cinereum, 
mocrypta examined (Fig. 1). Although not resolved for E. microperca, E. edwint, Ji trisella, and E. duryt) which 
the specimen of P. uranidea in Fig. 1, in a separate run appeared in tris-citrate buffer (Fig. 1) to possess a band 
using another specimen the band was as prominent in with a mobility possibly identical to that of the B, of 
this species as in other Percina (Fig. 2). In addition to Percina species. As demonstrated in EBT buffer, E. cin- 
the 67 species presented in Fig. 1, E. punctulatum was ereum does posses a band with the same mobility as the 
examined and was without the B, mobility of Percina. Percina B,; the other species do not. The most anodal 
Isozymes may be selectively precipitated by the ad- band of E. squamiceps also appears in Fig. 1 to have the 
dition of antisera to the enzyme extract prior to electro- same mobility as the B, band of Percina; however, elec- 
phoresis. The anodal band of Percina (designated B,) trophoresis in other gels demonstrated it to be different 
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Fig. 1—Lactate dehydrogenase isozymes from head extracts of 67 species of darters. Percina sciera is present on each 
as a marker species to facilitate comparisons between gels. Electrophoresis was in pH 6.8 tris-citrate buffer. 
