Blood protein variation in eight stocks of channel catfish

Vita.1. Horizontal starch gel electrophoresis was employed to detect variation in six blood proteins in eight populations of channel catfish. The proteins examined included hemoglobin, tetrazolium oxidase, lactate dehydrogenase, transferrin, esterase, and total serum proteins (including albumin). 2. No variation was observed for hemoglobin, lactate dehydrogenase, or tetrazolium oxidase and it was concluded that these proteins are unsuitable for genetic markers. They may, however, prove useful in comparative biochemical studies. 3. Electrophoretic variation was observed in several serum protein components visualized with a general protein stain but most of the variation appeared to be epigenetic in origin and probably useless as genetic markers. An infrequent variation was observed in serum that may involve genetic variation in an unidentified tetrameric protein. Further study should determine the identity of the protein and its value as a genetic marker. 4. Ten transferrin phenotypes were recognized in adult channel catfish sera, presumably encoded in four codominant autosomal alleles. Evidence of excessive numbers of individuals homozygous for transferrins indicates that the variation may possess a selective value that would detract from its usefulness as a genetic marker. 5. Electrophoretic variation was observed in erythrocyte and serum esterases. The erythrocyte esterase variants (Es-4) were difficult to score and were not evaluated as genetic markers. One of the serum esterases (Es-6) appeared to be associated with albumin, demonstrated considerable non-genetic variation, and was judged unsuitable as a genetic marker. The second esterase polymorphism (Es-5) was shown to be genetic and produced by three alleles at a single autosomal locus. The frequencies of Es-5 alleles differed significantly between populations and may reflect selective pressures extant in intensive fish culture